Journal of Spatial Analysis Environmental Hazards
تحلیل فضایی مخاطرات محیطی
Journal of Spatial Analysis Environmental Hazards
Literature & Humanities
http://jsaeh.khu.ac.ir
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2423-7892
2588-5146
10.61186/jsaeh
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jalali
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2022
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آغاز و پایان فصول طبیعی در ایران
Onset and End of Natural Seasons in Iran
تخصصي
Special
پژوهشي
Research
<strong>چهار فصل طبیعی ویژگی مناطق معتدل جهان است، اما تاریخ شروع، پایان و طول مدت آنها تفاوت دارد. به منظور تعیین شروع و پایان فصول طبیعی ایران از داده های روزانه دمای ظاهری 32 ایستگاه هواشناسی سینوپتیک طی 60 سال از 1959 تا 2018 استفاده شد. شروع زمستان و تابستان به ترتیب دمای ظاهری صفر و 20 درجه، یعنی زمان توقف یا کند شدن فعالیت فیزیولوژی و مرحله زایشی در طبیعت تعیین شد. نتایج نشان داد، همه مناطق ایران چهار فصل طبیعی ندارند، بلکه مناطق ساحلی شمال و مناطق پایین تر از عرض 29 درجه جغرافیایی، فقط دو فصل پاییز (دوره خنک)و تابستان(گرم) دارند، به ترتیب سواحل شمالی، پاییز طولانی تر و تابستان کوتاه تر و مناطق جنوبی بر عکس. در دیگر مناطق ایران، به طور طبیعی چهار فصل، زمستان، بهار، تابستان و پاییز اتفاق می افتد، اما آغاز، پایان و طول مدت فصول، مرتبط با موقعیت جغرافیایی، ارتفاع و سیستم های جوی، متفاوت است. بنابراین به ترتیب از مناطق جنوبی به شمالی، آغاز زمستان 12 دی - 21 آذر، بهار، 12 بهمن - 18 اسفند، تابستان، 27 فروردین - 30 خرداد و پاییز، 23 آبان - 28 شهریور است. از طرف دیگر پایان فصول طبیعی به ترتیب، زمستان ، 11 بهمن-17 اسفند، بهار، 21 اردیبهشت-29 خرداد، تابستان، 22 آبان </strong><strong>–</strong><strong> 27 شهریور و پاییز، 2 اردییهشت تا 20 آذر می باشد. در مناطق معتدل ایران، طول فصول انتقالی، منظم بوده و تغییر زیادی ندارد، اما فصل تابستان و زمستان در مناطق شمال غربی و مرتفع غرب، با نظم 3 ماه در فصل، اما به طرف شرق و جنوب، طول زمستان کوتاه، و تابستان بلندتر است. چنانکه اعتدال اقلیمی از شمال غربی در همسایگی مناطق معتدل کره زمین، به شرق و جنوب کم شده و برعکس بر شباهت آن به اقلیم های بیابانی خشک جنب حاره ای گرم، مرطوب و یا سرد و خشک توران افزوده می شود. اقلیم ایران با توجه به موقعیت جغرافیایی در منطقه گذار از اقلیم معتدل به اقلیم بیابانی گرم و سرد کره زمین قرار دارد. </strong>
<span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><b><span dir="LTR" lang="EN" style="font-size:12.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Onset and End of Natural Seasons in Iran</span></span></span></b><b><span lang="AR-SA" style="font-size:16.0pt"><span style="line-height:115%"><span style="font-family:"B Nazanin""></span></span></span></b></span></span></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><b><span dir="LTR" lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><b><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Introduction:</span></span></span></b><b><span dir="RTL" lang="FA" style="font-size:12.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> Season is the natural pattern of change in nature, which is related to the movement of the sun, the temperature cycle, the life cycle of the earth (phenology) and human culture. In astronomical and climatic seasons, a year divided into four seasons, spring, and summer, autumn and winter (Alsop, 2005), (</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Trenberth</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">, 1983). Season is a period of the year with a homogeneous climate (Alsop, 1989), </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">that</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> is difficult to determine exactly when to start and end. The methods of determining of the seasons are: change in the face of the earth (</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Cayan</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> et al, 2001), (Wang et al., 2021), constant temperature threshold, (</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Jaagus</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> et al, 2003; </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Kitowski</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> et al, 2019; </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Ruosteenoja</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> et al, 2019; Alijani,1998), Air Masses, (Lamb, 1950; Cheng et al, 1997; </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Pielke</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> et al, 1987; </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Kalinicky</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">,1987; Alpert et al, 2004). What is a natural constant sign is the key to determining change and starting a new season. Organisms react to the onset and end of natural seasons by changing their behavior. Naturally, plants and animals adjust and adapt their phonological stages to temperature changes and jumps (</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Sparks</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> et al, 2002), Plants germinate and flower in spring,fruit in summer, reduced activity and leaf in autumn and in winter fall asleep (</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Menzel</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> et al, 1999 Animals are also adapted to reproduction, nesting and childbirth, And their phonological period is also related to vegetation conditions. In other words, the life stages of living organisms are adapted and dependent on these natural changes (</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Schwartz</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> et al, 2000). Some organisms also migrate in order to adapt (Smith et al, 2012). The genetic response of organisms to rapid climate change and seasons associated with winter warming across the north, the early onset of spring and a long growing season is a factor in impairing the physiological response (reproduction, dormancy or migration time) of species(</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Bradshaw</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> et al, 2008). On the other hand, the sensible temperature of organisms is affected by radiation, wind, air temperature and humidity. As appearance temperature is an important heat factor (heat and cold) in nature, to which animals, plants and humans react. </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Ruosteenoja</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> et al (2019), showed the length and onset seasons of European with thresholds of 0 and 10 ° C focusing on the scenario of a 2 ° increase in temperature, an increase in summer length and a decrease in winter compared to pre-industrialization. The length of summer increases by 1 degree, increases by 10 days, and the length of winters decreases by 10 to 24 days. </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Kitowski</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> et al, (2019), showed the onset of summer earlier, the </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">shorter</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> autumn, the longer summer and the shorter winter in Poland with zero-, 5- and 15-degree temperature thresholds. Wang et al, (2021) change the onset time and length of natural and summer seasons from 78 days to 95 days, and spring, autumn and winter, 124 to 115, 87 to 82, and 76 to 73 days, respectively. Also, summer is halfway through the year and winter is less than two months to 2100 in the middle of the Northern Hemisphere. Dong (2009) showed that in most parts of China since 1950, summers have been longer and winters shorter, with the onset of summer 5.8 days earlier and the length of the season 9 days longer and the winter 5.6 days later and the length of the season 11 days. Changes in transition seasons are less. Season start, end and season length changes studied in Oregon and Washington (Alsop, 1989), in the United States (Barry and Perry, 1973), Europe (</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Jaagus</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> et al, 2003), Estonia (</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Jaagus</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> et al, 2000), South Korea (Choi et al, 2006), China (Ma et al, 2020), Xinjiang in northwestern China (Jiang et al, 2011</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">; </span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Cheng et al, 1997), Eastern Mediterranean (Alpert et al, 2004), Iran (Alijani ,1377). Therefore, with the increasing trend of temperature in different regions of Iran (Alijani et al, 2012), study of change </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">of </span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">the start and end dates of natural seasons in connection with life in nature is necessary (</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Penuelas</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> et al, 2002). The aim of this study is determine the time of onset, end and length of natural and significant seasons and its difference with astronomical and climatic seasons in Iran with highlands, inland and coastal lowlands in the north and south with a new approach based on biological physiology.</span></span></span></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><b><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Material and methods:</span></span></span></b> <span dir="RTL" lang="AR-SA" style="font-size:12.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">To determine the onset and end of natural seasons, daily data of relative humidity, water vapor pressure, and wind speed and air temperature over a 60-year period for 32 synoptic stations in Iran from 1959 to 2018 were used. Selected stations cover all areas of Iran (coastal, low and high</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">lands</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">). In the first step, the apparent daily temperature of each station was calculated (Formula 1). In the second stage, with the knowledge of the direct </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">effect</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> of atmospheric circulation factors in the occurrence of natural phenomena (Alijani, 2011) And rapid changes in temperature (season),</span></span></span> <span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">the 4-day moving averages of apparent temperature (average life of cyclone and anticyclone) at each station were calculated and</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> was the basis of study</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">. The onset and end of the season are with a natural and biological approach related to the stages of bio phenology and the natural part's reaction to temperature changes. Therefore, the apparent temperature of zero and below zero with the reduction or cessation of biological activity in nature, is the onset of winter. On the other hand, the time required by nature to adapt to new temperature conditions, is at least 10 days (Joy, 2017). Therefore, the temperature of zero degrees and non-return to zero Up to at least the next 10 days, is the basis for the onset of winter. In fact, with the continuation of sub-zero temperatures for 10 days</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">,</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> the living part of nature receives </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">the signal of </span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">change. If after that, for a period of less than 10 days, the temperature goes above zero, the situation will not return to the previous state (nature did not react and adaptation occurred). On the other hand, the best temperature for the growth period is from at least zero degrees to a maximum of 30 degrees in nature (Abrami, 1972). The second key indicator is the temperature of the onset of summer and the warm period. For the onset of the summer season, the temperature of 20 degrees </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">was</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> base with the previous conditions. Because at this temperature, the reproductive period in plants and animals has started, most animals and plants have children and humans also feel warm. As plants begin to fill grain at this temperature, including wheat (Jenner, 1991 and </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Dupont</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> et al, 2003) as the world's oldest grain. Here, the same con</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">diction as before,</span></span></span> <span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">don’t</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> return to 20 degrees for at least the next 10 days</span></span></span> <span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">was the basis. So at the onset of both seasons, if the temperature returns to zero and 20 in the 10-day period, the season has not begun, and in that year the station does not have winter and summer, respectively. Then, the temperature of 19 degrees and less with the above conditions, the onset of autumn and the temperature of 1 degree and more with the above conditions, are the basis for the onset of spring.</span></span></span></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Formula 1: Calculate the apparent temperature</span></span></span> <b><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">AT = T + 0.33 PV - 0.7 WS – 4</span></span></span></b><b><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">T = air temperature in Celsius, PV = water vapor pressure in hPa, WS = wind speed in meters per second, AT = apparent temperature in Celsius</span></span></span><span dir="RTL" lang="AR-SA" style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><b><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><b><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Results and discussion:</span></span></span></b><b><span dir="RTL" lang="FA" style="font-size:12.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> The onset and end of natural seasons are different in the geographical and topographical location of Iran. Southern regions and the northern coasts </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">are</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> two seasons with a warm summer season and a transitional season (cool). Other parts of Iran, like the temperate regions of the globe, have four seasons, but the start, end and length varies. The longest winter in the northwest and the western heights and the length of winter to the east and south is short and vice versa, the longest summer in the south and center of Iran. Spring season in below 29 degrees orbit, Khuzestan and the shores of the Caspian Sea is not a separate season, but with the absence of winter, it merges with autumn. In other regions, spring begins in the south and northwest, respectively, from </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">31 January</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> to 8 March. In most parts of Iran, the onset of spring coincides with the traditional date of Nowruz, after </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">small chelleh</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> of winter. This month coincides with the rise in temperature and the revival of nature and the introduction of the New Year. The end of spring in the central regions, 10 May and in the northwest, 18 June, and its length varies from 103 to 96 days in the northwest and northeast, respectively. In the temperate regions of Iran, it is about three months with a 10-day spatial fluctuation (Table 1). The onset of summer is with a new stage of phenology in nature</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">. </span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">The onset of summer is from 15 April on the southern coasts with high tropical arrival and the latest onset of summer in the northwestern part is 19 June (Table 1). In the south of the orbit of 29 degrees and the region of Khuzestan, until 8 May, in the central and northeastern regions of Iran from 22 May to 29 May and the west and northwest region, from mid-June to the end of June. The end of summer, as opposed to the onset, is the earliest time of 17 September in the northwest, and in the southern regions of Iran, the end of 8 October is in the 29 degree orbit. The southern regions of Iran, the longest summer that shows the role of latitude and slower exit of the tropical system (Alijani, 1390). The length of the summer season in temperate regions varies from 90 to 139 days, approximately three to five months, respectively in the northwest and the 29-degree geographical orbit, respectively. Therefore, the spatial trend of summer length from east and south of Iran to north and northwest is decreasing and there are the shortest summers in northwest of Iran. Naturally, this spatial trend is related to the high-altitude inbound and outbound routes of the subcontinent and the western systems from the south and northwest, respectively. The month of October and November is the onset of autumn in Iran, in the northwest and northeast, with the arrival of cold atmospheric circulation from above, the angle of radiation and altitude, is 18 September. The latest start of autumn in Hormozgan is 12 November (Table 1). The end of autumn is the first of April to the first of June in the south and north coasts, respectively. In the northeast of Iran, 24 to 28 December, and in the central regions, 28 to 31 December, is the end of the autumn season. The earliest end in the northwestern regions of Iran at the end of December is 10-17 December. The length of the autumn season in temperate regions is 83 to 97 days, respectively, in the northwest and northeast, that’s an average of nearly three months. With the onset of winter, decreases in temperature (frost) and winter during the year below the 29 degree orbit are rare, but on the northern coast, with the influence of atmospheric systems, it is a coincidence. In other regions of Iran, northwest, west and east of Zagros and south of Alborz, above 29 degree orbit, from 11 December to 1 January, is the time of winter. Respectively, the earliest onset of winter is in the northwest, and the latest onset in the central regions (Table 1). As the westerly winds of the extraterrestrial latitudes with cyclones and anticyclones dominate the Iranian atmosphere, also, the angle of radiation and the amount of radiation received at the earth's surface at this time, reaches a minimum during the year. The end of winter in temperate regions is from 30 January in the 29 degree orbit to 7 March in the northwestern regions. Winter length reaches 86 days in northwestern Iran, 29 days in central regions (above 29 degree orbit) and 58 days in northeastern Iran, Therefore, there are only three winter months in northwestern Iran and in other parts of Iran, it is the shortest season during the year. Spatial trend of winter length from northwest of Iran to east and south is decreasing.</span></span></span><b><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><b><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Figure1: </span></span></span></b><b><span dir="LTR" lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Date of onset, end and duration of natural seasons in different regions of Iran</span></span></span></b><b><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span>
<table align="center" class="MsoTableGrid" dir="rtl" style="border-collapse:collapse; border:none">
<tbody>
<tr>
<td colspan="3" style="border-bottom:1px solid black; width:134px; padding:0cm 7px 0cm 7px; border-top:1px solid black; border-right:1px solid black; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Fall</span></span></span><b><span lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span></td>
<td colspan="3" style="border-bottom:1px solid black; width:140px; padding:0cm 7px 0cm 7px; border-top:1px solid black; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Summer</span></span></span><b><span lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span></td>
<td colspan="3" style="border-bottom:1px solid black; width:137px; padding:0cm 7px 0cm 7px; border-top:1px solid black; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Spring</span></span></span><b><span lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span></td>
<td colspan="3" style="border-bottom:1px solid black; width:137px; padding:0cm 7px 0cm 7px; border-top:1px solid black; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Winter</span></span></span><b><span lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span></td>
<td rowspan="2" style="border-bottom:1px solid black; width:75px; padding:0cm 7px 0cm 7px; border-top:1px solid black; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Season</span></span></span></span></span></span></td>
</tr>
<tr>
<td style="border-bottom:1px solid black; width:52px; padding:0cm 7px 0cm 7px; border-top:none; border-right:1px solid black; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Length</span></span></span><b><span lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:39px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">End</span></span></span><b><span lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:43px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">onset</span></span></span><b><span lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:52px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Length</span></span></span><b><span lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:40px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">End</span></span></span><b><span lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:49px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">onset</span></span></span><b><span lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:52px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Length</span></span></span><b><span lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:40px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">End</span></span></span><b><span lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:45px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">onset</span></span></span><b><span lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:52px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Length</span></span></span><b><span lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:39px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">End</span></span></span><b><span lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:46px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span style="direction:rtl"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span dir="LTR" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">onset</span></span></span><b><span lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span></span></span></td>
</tr>
<tr>
<td style="border-bottom:1px solid black; width:52px; padding:0cm 7px 0cm 7px; border-top:none; border-right:1px solid black; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">83</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:39px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">10 Dec</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:43px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">18 Sep</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:52px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">227</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:40px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">17 Sep</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:49px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">15 Apr</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:52px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">100</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:40px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">10 may</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:45px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">31 Jan</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:52px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">86 </span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:39px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">30 Jan</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:46px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">11 Dec</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:75px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Earlier</span></span></span></span></span></span></td>
</tr>
<tr>
<td style="border-bottom:1px solid black; width:52px; padding:0cm 7px 0cm 7px; border-top:none; border-right:1px solid black; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">160</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:39px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">21 Apr</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:43px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">13 Nov</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:52px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">90</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:40px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">12 Nov</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:49px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">19 Jun</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:52px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">103</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:40px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">18 Jun</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:45px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">8 Mar</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:52px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">29</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:39px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">7 Mar</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:46px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">1 Jan</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:75px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Later</span></span></span></span></span></span></td>
</tr>
<tr>
<td style="border-bottom:1px solid black; width:52px; padding:0cm 7px 0cm 7px; border-top:none; border-right:1px solid black; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">77</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:39px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">133</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:43px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">56</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:52px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">137</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:40px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">55</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:49px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">65</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:52px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">3</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:40px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">39</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:45px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">36</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:52px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">57</span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:39px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">36</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:46px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span dir="RTL" lang="FA" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">21</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span></td>
<td style="border-bottom:1px solid black; width:75px; padding:0cm 7px 0cm 7px; border-top:none; border-right:none; border-left:1px solid black"><span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Fluctuation</span></span></span></span></span></span></td>
</tr>
</tbody>
</table>
<span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><b><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></b></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><b><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Conclusion:</span></span></span></b> <span dir="RTL" lang="AR-SA" style="font-size:12.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">The time of the onset, end and length of natural seasons in Iran are different from astronomical and calendar seasons. The slow decreasing and increasing trend of temperature at the onset and end of the seasons is initially a function of the angle of radiation and the length of day and night, but the real onset of a season with temperature jumps associated with the migratory atmospheric system (cyclone and anticyclone), Siberian hypertension, It is from the north and high in the subtropics from the south. Areas below 29 degree orbit in the south of Iran and Khuzestan and the northern coasts, have only two seasons of autumn (cool) and summer (warm) and the temperature decreases to zero and less (occurrence of winter), in the southern regions, rare and on the northern coasts is accidental and short. The apparent temperature in these areas has been decreasing since late summer and in the middle of the cold period, it is decreasing to the maximum (lowest temperature during the year) and increasing again until the onset of summer. Therefore, the above areas are two periods, with a cool season and a hot and hot season. The southern coasts of Iran and Khuzestan have short cooling seasons and long hot and hot summers, and the northern coasts, on the contrary, have shorter summers and longer and cooler autumns, that The influence of water temperature, latitude, topography and atmospheric systems are effective in these differences. In other regions of Iran, except the mentioned regions, four natural seasons occur (spring, summer, autumn and winter). In connection with the role of latitude, altitude, the arrival of migratory and high pressure Siberian atmospheric systems, the time of onset, end and length of the season has a change of location. As the length of summer is more in the southern, eastern and central regions of Iran and decreases in the northwest and west of Iran, and the length of winter is the opposite. The length of the transitional seasons (autumn and spring) in the temperate regions of Iran is not different and the three months in the season are similar to the astronomical and calendar seasons. The most important spatial difference is during winter and summer. Winter decreases from three months in the northwest of Iran to the south and east of Iran and reaches a month in the 29 degree orbit. On the other hand, the length of summer, on the contrary, varies from five and three months from east and south of Iran to northwest of Iran. Therefore, in temperate regions of Iran, the length of natural seasons from the south and east of Iran to the west and northwest of Iran is more regular and approaches</span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> to</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> three months in each season. This spatial trend indicates the climatic similarity of western and northwestern Iran with temperate regions of the globe in higher latitudes and but to the center, south and east of Iran, this similarity decreases and to hot and cold dry desert climate in the Middle East and </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">central Asia</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> region is similar, respectively. This indicates regularity and order in nature, </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">which</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> is related to the geographical principle of Tobler’s law, the spatial correlation of climates and the onset, end and length of their seasons. Therefore, if we consider three months in a season as a natural feature of the temperate regions of the earth and two seasons (climatic period) as a feature of the subtropical regions, Iran is in the transition zone of these two climates. As from three months, the length of each season in the northwest to less than a month in the range of orbit 29 degrees, and then the subtropical conditions with two seasons (warm and cool) appear. Therefore, from northwest to east and south of Iran, the climatic </span></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">moderation</span></span></span><span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""> decreases and its tropical sub-characteristic (longer summer and shorter winter) heat and dryness to heat and humidity in southern Iran is added. Naturally, in this spatial process, primarily large-scale atmospheric rotations and secondly, geographical phenomena (their shape and position) play a pivotal role. The Caspian Sea coast is an exception to this rule due to its higher latitude and complexity of geographical phenomena and the role of water, because the climate systems related to the Caspian climate are different from other regions of Iran.</span></span></span> <span dir="RTL" lang="AR-SA" style="font-size:12.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><b><span style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Key words:</span></span></span></b> <span lang="EN" style="font-size:10.0pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times="">Natural Seasons, Apparent Temperature, Plant and Animal Phenology, Iran.</span></span></span><span dir="RTL" lang="AR-SA" style="font-size:12.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span><br>
<br>
فصول طبیعی, دمای ظاهری, فنولوژی گیاهی و جانوری, ایران
Natural Seasons, Apparent Temperature, Plant and Animal Phenology, Iran
19
36
http://jsaeh.khu.ac.ir/browse.php?a_code=A-10-431-4&slc_lang=fa&sid=1
reza
doostn
رضا
دوستان
doostan@um.ac.ir
100319475328460010313
100319475328460010313
Yes
دانشگاه فردوسی