Showing 5 results for Ghaemi
Miss Sorayya Derikvand, Dr Behrooz Nasiri, Dr Hooshang Ghaemi, Dr Mostafa Karampoor, Dr Mohammad Moradi,
Volume 0, Issue 0 (3-1921)
Abstract
sudden stratospheric warming has an obvious effect on the Earth's surface climate. In this research, the changes in precipitation during the occurrence of this phenomenon have been investigated. For this purpose, after revealing the warmings that occurred during the studied period (1986-2020), 18 warmings were identified. The 5th decile and 9th decile of precipitation were calculated for the precipitation data of 117 stations. And the size of the difference from the normal rainfall was checked in two ways. First, the precipitation at the time of warming was compared with the long-term average, and then the trend of changes in precipitation at three times before thewarming, at the same time as the warming, and after the warming was finished. Finally, these results were obtained. Warmings according to the month in which they occur; They have a different effect on the amount of precipitation. In the sudden stratospheric warming that occurred in December, January and February, the northwest experiences the most rainfall changes and is above normal, and the probability of rainfall above the 9th decile increases up to 65%. Western and southwestern regions also have higher than average rainfall and the probability of heavy rainfall is high. Precipitation on the shores of the Caspian Sea shows an inverse relationship with sudden stratospheric warming, so in all the investigations of this research, the lack of precipitation at the time of warming in these areas is significant. Southern regions have less than normal rainfall in all sudden stratospheric warming events. The center of Iran has higher than average rainfall in the sudden stratospheric warming months of March. Eastern Iran also has heavy rains compared to normal during the sudden stratospheric warming months of March.
Elham Yarahmadi, Mostafa Karampoor, Hooshang Ghaemi, Mohammad Moradi, Behrouz Nasiri,
Volume 19, Issue 53 (6-2019)
Abstract
Investigating of rainfall behavior in the spatial-temporal dimension and determining the tolerance thresholds of different geographical areas with respect to vegetation, animal life and human activities, is essential for any decision in the environment. Therefore, precipitation data of 27 stations were received from the Meteorological Organization during the 60-year period and After the data were evaluated qualitatively, The distribution of temporal and spatial mean, coefficient of variation, skewness and probability distribution of 20% maximum and minimum monthly and seasonal autumn and winter, for a period of 60 years (1951-2010), two 30-year periods (1980-1951), (1981- 2010) and two 10-year periods (2010-2001), (1951-1960) were calculated and were zoned using GIS. Studies show, except on the shores of the Caspian Sea, there is little change between autumn and winter patterns. The average rainfall of the southern shores of the Caspian Sea has decreased to the west and east. in other areas of the country, the spatial and temporal variations of rainfall in the autumn are very highand from the north to the south, the mean decreases and the coefficient of variation and skewness increase. In winter, maintaining the pattern of autumn, the average precipitation increases and the coefficient of variation decreases. The average precipitation of 30 years and 10 years of the second winter season, compared to the first 30 years and 10 years, and also the 60 year period, has decreased in most stations, which is consistent with the results of the Mannkundal test. Analysis and review of the 20% minimum and maximum seasonal rainfall show that the intensity and range of performance of winter precipitation systems in the second 30 years have decreased. Also, the frequency and severity of drought in the autumn season have increased in the second 30 years and in the last 10 years. The highest decline occurred in the western and eastern parts of the Caspian coast and in the northwest, which requires special attention to managers in light of the areas of activity and concentration of the population.
Hosseinali Roohbakhsh Sigaroodi, Mostafa Karampoor, Hooshang Ghaemi, Mohammad Moradi, Majid Azadi,
Volume 19, Issue 55 (12-2019)
Abstract
Investigating the variability of the spatial-temporal pattern of rainfall, which can lead to climate change, due to its strong impact, is of interest to various scientists. For this purpose, after receiving the daily precipitation data of 27 stations for the period of 60 years (2010-1951), its quality and the total monthly precipitation and statistics necessary for the continuation of the research process such as mean, coefficient of variation, skewness, probability estimate of 20% The upper limit of the maximum and minimum rainfall average were calculated experimentally for a period of 60 years and two 30-year periods (1951-1980 and 1981-2010) and two periods of 10 years (1951-1960 and 2010-2001) for each of the spring and summer seasons Was calculated. The studies show relatively modest variations in spring and summer precipitation patterns on the Caspian coast, Northwest-West, 30 and 10 years old, compared to the 60-year, 30-year, and 10-year periods. In general, the mean of precipitation decreases from north and northwest to south and south east and increases the amount of coefficient of change and skidding. Except for the Caspian Basin, in the remaining stations, the average spring precipitation is higher than the average summer rainfall. There is a clear difference in the long-term characteristics of precipitation and its changes. It is worth mentioning that the increase in the coefficient of variation of the 30-year and 10-year periods is comparable to the corresponding periods at all stations, which indicates a decrease in the monthly and seasonal mean of spring and summer precipitation, which confirms the results of the decade and the first decade of the second decade. The greatest decrease occurred in the northern and western parts. In the second 30 years, the incidence of dry sunshine and drought-affected stations has increased. Therefore, it confirms the climate change for the Caspian and the Southwest coast.
Ms Elaheh Ghasemi Karakani, Mr Ebrahim Fattahi, Mrs Loabat Salehi Pak, Mr Hooshang Ghaemi,
Volume 23, Issue 69 (6-2023)
Abstract
During the rainfall, the intensity of precipitation varies. Changes in the amount of precipitation during an event of rainfall are effective in the resulting of flood and its intensity. Knowledge of how rainfall changes over time during rainfall is determined by temporal distribution pattern of rainfall. For this purpose, availability of short-term time scales rainfalls data are important that obtained by rain gauge stations. However, the low density of the rain gauge network and the lack of sufficient data from the time pattern of rainfall have always been a problem in determining storm patterns for executive plans. Therefore, the simulation of WRF numerical weather models can be used. The WRF model is one of the most responsive models for predicting precipitation, temperature and atmospheric elements that used in this study. In this paper, three great storm events on 15 December 2003, 24 - 26 December 2006 and 6-7 March 2007 have been selected in the Parsian dam basin and surrounding areas in south west of Iran. The result of WRF numerical weather prediction model for these great storms compared with data loggers. It showed that the WRF model was able to performance the heavy rainfall and simulates the rainfall pattern in these dates.
Doc. Zahra Ghassabi, Doc. Hoshang Ghaemi, Mr. Ebrahim Mirzaei,
Volume 25, Issue 76 (3-2025)
Abstract
The structure of deep moist convection can be influenced by various factors, including wind shear, available potential energy of convection, relative humidity, and vertical distribution of these variables. Among these factors, wind shear plays a more significant role in the creation of convection. The interaction between large-scale and synoptic-scale processes, along with the adjustment of available potential energy for convection and the presence of convection inhibitors, creates conditions suitable for the development of convection. The large-scale average reduces the convection inhibitor, while even small vertical velocities, such as a few centimeters per second, can have a noticeable impact on the environment's sounding. The presence of potential instability is also considered an important factor in initiating deep moist convection. When the temperature reaches the critical point and the convection inhibitor is removed, moist deep convection begins. If an air parcel rises above the lower stable layer with low relative convective inhibition energy and high relative free convective potential energy, it supports the development of deep moist convection. The initiation of updrafts by warm air masses and the subsequent development of convection depend on parameters like vertical wind shear and the inversion cap of the environment, among others. Large-scale convective systems can be triggered with less forcing due to the significant uplift of the air mass from the surface to the convection level along the front.
