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Investigating the variability of the Siberian high pressure intensity in relation to the anomalous winter circulation of the atmosphere
Atefeh Rezaei Talei, Zahra , Buhlol Alijani, Hematolah Roradeh, Taher Safarrad,
Volume 0, Issue 0 (3-1921)
Abstract
The role of regional and extra-regional forcings causes changes in the Siberian high-pressure cyclonic circulation every year. In this regard, an attempt was made to investigate the variability of the intensity of the Siberian high pressure in relation to the abnormal winter circulation of the atmosphere. For this purpose, gridded data of sea level pressure, geopotential height, orbital and meridional wind components of Center for Environmental Prediction/Atmospheric Sciences (NCEP/NCAR) between the years until 2020 (December to February) were used. After applying the Siberian high pressure intensity index, the extreme periods of this high pressure in winter were extracted. Next, the development of this system and the systems affecting the Siberian high pressure were investigated using the quantity of relative Vorticity advection. The results showed that during the winter period, the high pressure center of Siberia has undergone changes and has taken on a growing trend between 4 and 6 hectopascals. On the other hand, it was observed that the role of atmospheric systems such as dynamic ridges on the Siberian region along with advection The negative relative humidity, the location of the Siberian region in the east of the ridge, and the formation of omega bands play an important role in strengthening this system, which has caused this high pressure to develop from east to west or north to south. On the other hand, the role of the polar vortex in the cold advections of the region and the displacement towards the equator has caused the Siberian high pressure to sometimes increase by more than 11 hectopascals compared to its long-term average. Finally, it was observed that the atmospheric circulation in mid-latitudes plays a transitional role in the high pressure changes in Siberia and the polar and subpolar currents.

Radiation balance and urban land use (case study: Kermanshah city)
Taher Safarrad, Mehran Mansourinia, Hersh Entezami,
Volume 19, Issue 53 (6-2019)
Abstract
Population growth and urbanization development are the main triggering factors of changes in urban land uses. These, in turn, result in changes in the components of radiation balance. The present study tries to analyze the role of urban land uses in radiation balance by calculating net radiation and its analysis. For this purpose, the Landsat 8 satellite image of 2016 was used. Characteristics of radiation flux including net radiation flux (RN), ground surface albedo (α), incoming longwave radiation (RL↓), incoming shortwave radiation (RS↓), outgoing longwave radiation (RL↑), and ground surface temperature were computed using Sebal algorithm.The values ​​of these components in different land uses (compressed residential, scattered residential, green area and wastelands) were analyzed using one-way analysis of variance (ANOVA) and Tukey’s test. The results of this study showed that the selected land uses have significant differences in the amount of radiation flux, therefore the wastelands are warmer than the residential areas by about 6 oC and the residential areas are warmer than the green areas by about 1.5 oC. The results also indicated that these differences are due to changes in output energy (α and RL↑), and any change in land use over time will ultimately lead to a change in the radiation balance and the temperature of those places, which this temperature increase, is different from the increase of the temperature due to global warming.

Investigation of Impervious surface and Urban Surface Temperature in Qaemshahr
Taher Safarrad, Yadollah Yousefi, Atefeh Rezaei Taleei,
Volume 21, Issue 62 (9-2021)
Abstract
Information on a variation of impervious surface is useful for understanding urbanization and its impacts on the hydrological cycle, water management, surface energy balances, urban heat island, and biodiversity. This research attempts to detect impervious surfaces and its changes by satellite imagery in Qaemshahr. The relationship between impervious surfaces and changes in land surface temperature in the city was investigated. For this purpose, after obtaining three images in 1978, 2000, and 2017, and performing the necessary preprocessing, the reflection values of the infrared spectrum and ground surface temperature in the study area were calculated. The reflectance of this spectrum was investigated in various land uses vegetation, asphalt and building areas in two parts of the urban and the suburb.  Using the results of ANOVA and Tukey these properties compared to different land uses. By the difference between Permeable surfaces and impervious surfaces, the impervious surface index was calculated. The results of the detection and comparison of the three surveyed images showed that the impervious surfaces in Qaemshahr were significantly increased from 1978 to 2017. In the next step, by calculating the land surface temperature, it was determined that the temperature of the impervious surfaces is higher than the other parts of the study area. An increase in the population of the city followed by an increase in urban construction has led to an increase in impervious surfaces and a reduction in green space and this has caused a rise in city temperatures. The results of this study showed that increasing impervious surfaces has led to an increase of around 4 degrees in the city's temperature. Finally, any increase in the impervious surface at the city will lead to unsustainability in the urban environment, if not accompanied by proper planning.

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