Climatology
Atefeh Hoseini Sadr; bromand salahi; Gholam Hasan Mohammadi
Abstract
The aim of this study is to investigate the long-term fluctuations and trend in horizontal visibility in the northwest of Iran. For this purpose, hourly horizontal visibility data from 7 synoptic stations were used for the period of 1951-2020. The Koschmieder approach was used to calculate the extinction ...
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The aim of this study is to investigate the long-term fluctuations and trend in horizontal visibility in the northwest of Iran. For this purpose, hourly horizontal visibility data from 7 synoptic stations were used for the period of 1951-2020. The Koschmieder approach was used to calculate the extinction coefficient. Moreover, the Mann-Kendall and Rdit tests were applied to examine the trend of horizontal visibility. Also, the percentages of very good visibility (>19 km) compared with bad (<10 km) visibilities. Based on the results the annual average of horizontal visibility in northwest of Iran is ~13 km. This study showed three different fluctuation periods in the regional average of horizontal visibility: the first period (1951-1985) showed a sharp decrease in the visibility, the second period (1987-2005) was characterized by a low and stable visibility, and the third period showed a recent relative improvement. The regional average of horizontal visibility (extinction coefficient) exhibited a significant decreasing (increasing) trend of -0.167(0.0017) km per year at a confidence level of 0.01. The significant decreasing trend was confirmed in all stations except for the Ardabil station. The most severe decreasing trend was detected in Sanandaj and Zanjan stations with rates of 0.183 and 0.179 km year-1, respectively. The region-average of Rdit statistic in northwest Iran in the early 1950s was ~0.85, but it decreased to around 0.3 in the 1990s. Despite the recent improvement in horizontal visibility, reaching the reference distribution (i.e. Rdit=~0.5), the decreasing trend of horizontal visibility was still confirmed. The percentage of trend analysis of very good and bad visibility showed an increase in bad visibilities (from 5% to 25%) and a decrease in very good visibilities (from 80% to 5%), which confirms the decreasing trend in horizontal visibility. Hazy condition with 38.7% was the most influential weather phenomenon in visibility degradation.
Climatology
Roghayeh Maleki Meresht; Bromand Salahi; Mahnaz Saber
Abstract
The current research was carried out to analyze the changes in precipitation in northwest Iran during the coming decades based on GCM models. For this purpose, first, the precipitation of 1985-2014 was trended based on the Mann-Kendall test. Then, the daily precipitation data for each of the studied ...
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The current research was carried out to analyze the changes in precipitation in northwest Iran during the coming decades based on GCM models. For this purpose, first, the precipitation of 1985-2014 was trended based on the Mann-Kendall test. Then, the daily precipitation data for each of the studied stations was simulated in SDSM6.1 software for 1985-2014. Then, under the scenarios (SSP2-4.5) and (SSP5-8.5) of CanEsm5 and MPI-ESMI-2HR models, the precipitation of 2015-2043 was predicted. To evaluate the performance of CMIP6 models and compare the basic and predicted values, MSE, RMSE, and MAE statistical measures were used. According to the results of the Man-Kendal test, the precipitation of the base period in the stations of Tabriz, Ardabil, Urmia, Takab, and Maragheh has a decreasing trend and in the stations of Meshginshahr, Sardasht, Mako, Khalkhal, Sarab, Jolfa, and Parsabad it has an increasing trend. Among the 12 investigated stations, only the Maragheh station had a significant decreasing trend. In other stations, precipitation trends were not significant. According to the predictions made based on the mentioned models, under the medium scenario (SSP 2-4.5), the precipitation will decrease in late winter and early spring. In other months, especially summer and autumn months, the percentage of precipitation will be higher. Based on the SSP5-8.5 scenario, the highest percentage of precipitation decrease in the MPI model was predicted by 33% in Jolfa, Sardasht, and Maragheh stations, and in the CanESM5 model, about 33-35% in Jolfa, Takab, and Urmia stations. According to the results, although both models predicted precipitation with a relatively high error, the MPI model had a lower error and more accuracy in predicting precipitation than the CanESM5 model.
Climatology
Shirin Mahdavian; Batool Zeynali; Bromand Salahi
Abstract
Climate diversity and land use / land cover change have a significant impact on hydrological regimes, especially in arid and semi-arid regions with critical water shortage problems. Therefore, estimating and evaluating climate change and land use and its consequences in each catchment is essential. This ...
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Climate diversity and land use / land cover change have a significant impact on hydrological regimes, especially in arid and semi-arid regions with critical water shortage problems. Therefore, estimating and evaluating climate change and land use and its consequences in each catchment is essential. This study examined the climate change of Kiwi Tea Basin using the data of four models of the Fifth Climate Change Assessment Report (CMIP5) under both optimistic and pessimistic scenarios (RCP8.5 and RCP4.5) using the LARS-WG6 microcirculation model. Changes in precipitation and temperature during three different periods (2040-2021, 2060-2041 and 2080-2061) compared to the base period (2019-1987) have been studied and for calibration and validation of LARS-WG6 model, observational data and output data of models with The use of F and T tests as well as RMSE, MSE, MAE and R2 indices were compared and evaluated. Based on the results of most of the models and the average of the studied models, in general, it is expected that the amount of precipitation and the minimum and maximum temperature in all the studied models will increase compared to the base period. Also, the results of evaluating land use changes with object-oriented classification showed that rangeland use with an area of 1224.18 and 1046.59 square kilometers, respectively, covered the largest area in both periods, while in 1987, residential use with an area of 3.66 square kilometers and in In 2019, water use with an area of 3.77 square kilometers had the lowest area. Also, the most modified use of rangeland use was dryland agriculture (181 square kilometers), which indicates thedestruction of rangelands
Climatology
Nafiseh Rahimi; Saeed jahanbakhsh; Brooman Salahei
Volume 23, Issue 70 , March 2020, , Pages 145-167
Abstract
Strong winds are one of natural disasters that sometimes cause enormous Financial and physical damages. Since northwest of Iran and specially Ardabil Province is one of windy regions, this study tried to identify synoptic patterns which bring strong winds. Through considering equal and threshold wind ...
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Strong winds are one of natural disasters that sometimes cause enormous Financial and physical damages. Since northwest of Iran and specially Ardabil Province is one of windy regions, this study tried to identify synoptic patterns which bring strong winds. Through considering equal and threshold wind speeding over 28 knots per second, 783 days identified as wind crashing days in Ardabil province. Then by data component- based analysis of 500hPa geo-potential height of the 783-days detected seven components which explain 92% of variance. Finally by clustering seven components identified ten patterns as synoptic patterns that are responsible for Strong wind of Ardabil province. The survey of topographic arrangement of these patterns indicates the rise of trough and ridge levels to these patterns. This means that the patterns consists of, mainly, trough, ridge, or combination of both and aren’t observed other systems such as cut off, block systems, etc. Although mentioned systems may be observe in individual patterns of each of the 783 days, but the systems aren’t responsible for the dominance and influence. The temporal distribution patterns show that two patterns, 6 and 7which occurs in the summer, has a similar system at 1000 hPa level when it compares with other models which occur in winter, spring, fall. What's notable, reversal of location position of pressure systems, 1000 hPa, in two patterns of summer, so that a low pressure instead of high pressure is over the Zagros and a high pressure instead of low pressure is over the Caspian Sea.
Climatology
Broomand Salahie; Mahdei Aeli Jaham; Saiede Ainei; Jafar Derakshei
Abstract
The purpose of this study is forecasting the moderat and severs frost of three stations in Kermanshah, Kangavar and Sarpolezahab using output of the LARS-WG downscale model in the next two decades. The Input data's of models used in this study are: precipitation, minimum temperature, maximum temperature ...
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The purpose of this study is forecasting the moderat and severs frost of three stations in Kermanshah, Kangavar and Sarpolezahab using output of the LARS-WG downscale model in the next two decades. The Input data's of models used in this study are: precipitation, minimum temperature, maximum temperature and radiation in daily scale during the period 1992 - 2012. In the present study, using the output of two climate models, HADCM3 and BCM2 Under A1B Scenario, the initiation and end of the moderat and sever frost in these three periods 2030-2011, 2065-2046 and 2099-2080 have been evaluated. The results of the LARS-WG model process by the means of two Scheme Bcm2 and Hadcm3 indicate the warming of these stations in the coming years. The initiation of the moderat frost in these pointed stations is going to April by passing time. Between the stations in which are under study, Kangavar and Kermanshah stations have similar behavior but the Sarpolezahab station because of its tropic characteristic, showed a different behavior rather than the two stations in the coming years. The beginning of sever frost of these stations delayed with passing time and proceeds toward spring and in the other side, the end time of the last sever frost by passing time and getting close to the end of the anticipated period, is toward the beginning of winter and even at the Sarpole-zahab station until February. According to the results of the processing these models, the number of days with the moderat and sever frost in these stations will be dwindled in the coming years and the trend of temperature in these stations will be increased.
