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 ...
Read More
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
Atefeh Hoseini Sadr; Gholam Hasan Mohammadi; Firooz Abdoul Alizade; Vaheid Khjaste Golamei
Volume 23, Issue 70 , March 2020, , Pages 79-100
Abstract
Heavy rainfall occurrence on April 14th, 2017 which followed by flood in Azarshahr and Ajabshir regions caused 48 deaths at East Azerbaijan province. Detecting synoptic mechanisms for such event was our main motivation for this study. In this regard, observational, upper atmospheric and SkewT data were ...
Read More
Heavy rainfall occurrence on April 14th, 2017 which followed by flood in Azarshahr and Ajabshir regions caused 48 deaths at East Azerbaijan province. Detecting synoptic mechanisms for such event was our main motivation for this study. In this regard, observational, upper atmospheric and SkewT data were used. First, spatial distribution of precipitation in the study area was plotted. Then, Geo-potential height, vorticity and omega, specific humidity, moisture transition, jet stream for upper level and Huff-Muller chart were analyzed for different atmosphere layers. Finally, some atmospheric stability indexes were surveyed by using SkewT charts. Results showed that, highest rainfall was occurred as a rain corridor between southwest of West Azerbaijan province and middle regions of Urmia Lake to the central regions of East Azerbaijan Province with 30 to 57 mm range. Synoptic maps showed that in this day simultaneous expansion of the ascending area of Mediterranean trough in mid atmospheric layers and the core of polar Jet stream in upper levels provided favorable conditions for unstable atmosphere on the northwest of Iran, so that the amount of omega was less than -0.3 Pascal per second. Specific humidity maps indicate that, at the same time a significant moisture flux has flown from the Red Sea to the northwest of Iran. Therefore, the rapid conversion of atmospheric moisture into the rain in the ascending area of Mediterranean trough was the main cause of the heavy rainfall occurring on this day. This issue was proved by convergence moisture flux map and the Hoff-Müller graph. SkewT charts and instability indexes of Tabriz station also confirmed high amount of moisture and favourable ascending conditions in the atmosphere on April 14th
Climatology
ali akbar rasouli; elnaz ostadi; mohammad reza aziz zade
Volume 23, Issue 69 , December 2019, , Pages 87-103
Abstract
The consequences of climate change in drought areas such as Iran, temporal and spatial changes are the distribution and concentration of rainfall, which can affect water resources. On the other hand, increasing the concentration of rainfall can causing hazards such as floods . The importance of the issue ...
Read More
The consequences of climate change in drought areas such as Iran, temporal and spatial changes are the distribution and concentration of rainfall, which can affect water resources. On the other hand, increasing the concentration of rainfall can causing hazards such as floods . The importance of the issue of distribution and concentration of rainfall has encouraged researchers to study in this regard. Concentration Index (CI) is a method which is used to study the distribution and concentration of rainfall. This study was performed to calculate and analyze 23 station daily precipitation concentration index in Northwest of Iran during 1951 to 2015. In this research range of CI values calculated between 0.57 for Khoy station to 0.67 for Maku station and average 0.61 for all station. CI map obtain from values Interpolation and showed that the Northwest part of the study area with Maku station depute, compared to other regions, especially in central areas such as Tabriz station is not uniformly distributed. Also Northwest area with an average of 0.61 compared with an average CI of Iran ( 0.64) is more evenly precipitation distributed throughout the year.
Climatology
Saeid Jahanbaksh; Gholam Hasan Mohammadi; shahnaz rashedi; Atefeh Hoseini Sadr
Abstract
In this study, non-parametric Mann-Kendall test was used to analyze the trend of monthly mean minimum temperature in the Northwest of Iran. For this purpose, the data from 35 synoptic stations in the cold part of year including November, December and January-to-April have been used in the period of 24 ...
Read More
In this study, non-parametric Mann-Kendall test was used to analyze the trend of monthly mean minimum temperature in the Northwest of Iran. For this purpose, the data from 35 synoptic stations in the cold part of year including November, December and January-to-April have been used in the period of 24 years (1987-2010). Kriging interpolation method was used to obtain spatial distribution of mean minimum temperature over study area. The results showed that the minimum temperature in most parts of study area is rising so that in the months of February, March and December respectively in 22, 19 and 17 stations of the 35 stations were determined an increasing trend. While only in April, at 6 weather stations decreased and this parameter is relatively stable in November and January. Spatial distribution of monthly mean minimum temperature indicated that this element is lower in the mountainous parts of study area (including Northwest and Southeast) and whiles in lowlands (including Northeast and Southwest parts), is higher than its regional average. It was also found that regional minimum temperature and its trend in the Northwest of Iran Does not have the same characteristics in different months, so that this parameter in January and in April increased and decreased in November and December. Finally, in November and December minimum temperature has not substantially changed.
Geomorphology
Rashid Saeidabadi
Abstract
The aim of current study are numerical simulation of the role of the Urmia Lake in climatic parameters in surrounding areas of the Lake. For analysis of climatic impacts of the Lake in Northwestern Iran the synoptic data in 5 station in the west and east of the lake were used. For simulation of the impacts ...
Read More
The aim of current study are numerical simulation of the role of the Urmia Lake in climatic parameters in surrounding areas of the Lake. For analysis of climatic impacts of the Lake in Northwestern Iran the synoptic data in 5 station in the west and east of the lake were used. For simulation of the impacts of Urmia Lake in mean temperature and precipitation in surrounding areas the Regional Climate Model (RegCM4) and TAPM model and two time series years include 2003 and 2006 have been used. Then by using the models outputs and observed data performance, the models have been calibrated. For modeling the impacts of the Urmia Lake in climatic elements in surrounding areas, two scenarios were considered. First: Existence of the lake at it’s the maximum extent; two: Aquatic body of Urmia lake removed and substituted by an area having coverage of gravel and sand with a texture of loam and also desert. The results of this study indicate that the RegCM model has a good performance than TAPM in simulation of temperature and precipitation in the North West of Iran. By changing the Lake landuse, precipitation of the region will decrease which in spring is more than other seasons. Another impact of landuse change in northwest of Iran is change in mean temperature. This parameter in cold period of year will decrease and in warm period will increase.
Geomorphology
masumeh Rjabi; ali shiri tarzam
Abstract
Abstract There are more than 50 salt domes with neogene age in the northwest of Iran 48 Domes of which have measurable dimensions. One of the criteria's according with which we can classify Iran north-west salt domes is structural features of salt's appearances in the region. In this article salt ...
Read More
Abstract There are more than 50 salt domes with neogene age in the northwest of Iran 48 Domes of which have measurable dimensions. One of the criteria's according with which we can classify Iran north-west salt domes is structural features of salt's appearances in the region. In this article salt domes in north west of Iran, according to their structural characteristics, have been divided into two groups with mono-clinal structure and anticline structure, at first the scatter diagram, regression line, the kind and amount of correlation between morphometric parameters of each group have been analyzed. Then the parameters of each group have been compared with those of the other group. Examining the salt domes morphometric parameters show that mono-clinal domes in comparison with the anticlinal domes have area, circularity coefficient and height but more stretching and elongation coefficient. Also, mono-clinal domes are located on faults or in a near distance from faults, therefore the mono-clinal domes in comparison with the anticlinal domes, are more influenced by the faults
Majid Rezaee Banafshe; Hoseyn Hossein Alipour Ghazi; Fatemeh Jaffari Shendi; Majid Alimohammadi
Volume 19, Issue 53 , September 2015, , Pages 117-135
Abstract
In this study, the heavy rainfall of Northwest of Iranhas been analyzed using environmental circulation approach. Isohyte maps were depicted using Kriging method on 14*14 km pixels from 21/3/1961 up to 31/12/2004 (a17508× 533 matrix). Based on these interpolated data we selected super heavy rainfalls ...
Read More
In this study, the heavy rainfall of Northwest of Iranhas been analyzed using environmental circulation approach. Isohyte maps were depicted using Kriging method on 14*14 km pixels from 21/3/1961 up to 31/12/2004 (a17508× 533 matrix). Based on these interpolated data we selected super heavy rainfalls for all in Northwest of Iran as a whole. Heavy rainfall and their locations have been detected from 00 to 1200 E and 00 to 800 N in the five this levels (1000, 925, 850, 700, 600 and 500 hPa level) at 00:00, 06:00, 12:00 and 18:00 UTC. The results of this study showed that four thickness circulation patterns play role in producing these super heavy rainfalls. In analysis of these precipitations one representative day was introduced for every circulation pattern. The analysis showed that the circulation patterns 2 justify the most of precipitations. These findings can play an important role in forecasting the precipitation and preventing from flooding in the region.
Davod Mokhtari
Volume 17, Issue 43 , October 2013, , Pages 275-305
Abstract
Jolfa-Hadishahr plain existing in the Aras free industrial and trade zone (northwest of Iran) are used by tourists for trekking or as pathways to other tourist sites and neighbor countries around the plain. The aim of this paper is to introduce the plain as a geomorphosite and to define vulnerability ...
Read More
Jolfa-Hadishahr plain existing in the Aras free industrial and trade zone (northwest of Iran) are used by tourists for trekking or as pathways to other tourist sites and neighbor countries around the plain. The aim of this paper is to introduce the plain as a geomorphosite and to define vulnerability of geoheritage which draws attention to the geological and geomorphological elements of nature, to planners. The research was based on the following survey and data processing phases: a) definition of general characteristics of study area, b) survey of geomorphological units, 3) survey of the geomorphological features and the geoenvironmental elements that may affect vulnerability, d) definition of possible risk scenarios. In conclusion, the Jolfa-Hadishahr plain is a geomorphosite and its characteristics are showed in a table as geomorphosite description card. Increasing people and tourists on the site threats environmental stability of the plain. The data collected on this geomorphological environment could be made available to a wider public, ranging from the individual visitor, to plain agency departments and staff, in the form of thematic geotourist maps and geomorphosite description card and in turn, plain agencies could utilize these maps as support for plain area planning and management with the aim of safeguarding both the plain and the plain visitors and dwellers, while also valorising the environment.
