Nafiseh Seyyed Nezhad Golkhatmi; Javad Bazrafshan; Arezo Nazi Ghameshlou; Parviz Irannejad
Abstract
North Atlantic Oscillation (NAO) is one of large-scale signal that affects the north hemisphere. Various studies have investigated the correlations between Iran’s precipitations and North Atlantic Oscillation from monthly to yearly scales. This study has considered weekly time scale. The daily ...
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North Atlantic Oscillation (NAO) is one of large-scale signal that affects the north hemisphere. Various studies have investigated the correlations between Iran’s precipitations and North Atlantic Oscillation from monthly to yearly scales. This study has considered weekly time scale. The daily precipitation variable was obtained from the ERA-Interim database (grid) and its compliance with ground reference points (synoptic) were investigated (1979-2016). The results showed that the amount of annual precipitation in regions with more humidity, especially in the Caspian region, is underestimated. Also, the correlation between grid and synoptic precipitation data in the western, northeastern and southeastern area of the country is the highest and in the strip parallel to the western-eastern line (the middle areas) is the lowest (weekly average). This correlation decreases from winter to autumn and spring, respectively. A review of the time series of the sever events of NAO during the year with the weekly scale showed that this signal had two peaks, which was used to select the time period of assessing the relationship between precipitation in Iran and NAO. The results showed that the correlation between grid precipitation and NAO is not completely direct and relative frequency of direct correlation is more than non-direct type and decreases from north to south.
Shahab oddin Zarezade Mehrizi; Asadollah Khoorani; Javad Bazrafshan; Ommolbanin Bazrafshan
Abstract
Gamasiab River is one of the five main branches of the Karkheh River and plays a basic role in preserving the life and ecosystem of the region. The first step in the adoption of proper and sustainable methods for managing the water resources of the Gamasiyab river is to gain continuous knowledge of the ...
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Gamasiab River is one of the five main branches of the Karkheh River and plays a basic role in preserving the life and ecosystem of the region. The first step in the adoption of proper and sustainable methods for managing the water resources of the Gamasiyab river is to gain continuous knowledge of the quantitative and qualitative status of the water as well as its variations. The use of hydrological models is common to simulate quantitative and qualitative processes associated with the water cycle. One of the models that is widely used in the international level is the SWAT model. In this research, we evaluated the efficiency of SWAT model in simulation of Gamasiyab river flow. For running this model requires a DEM, soil map, land use map and slope classification. Initially, discharge data in daily step at Polchehr Hydrometric Station was calibration (1977-1995 AD) and then validation (1996-2005 AD) by using precipitation data of two synoptic stations and three weather stations and minimum and maximum temperature of two synoptic stations. Statistical coefficients including Nash-Sutcliff coefficient, R2, P-factor and R-factor for calibration period were 0.71, 0.73, 0.79, 1.36 respectively and for validation period were 0.57, 0.61, 0.71 and 1.34 respectively. These results indicate that the SWAT model has the ability to simulate the Gamasiyab River discharge and researchers can use this model to apply management scenarios in short time and low cost for better decision making.
M Zare; Aliakbar Nazari Samani; shahram khalighi; javad bazrafshan; mohsen hasan joury
Abstract
Land use Changes have recently been increasing due to anthropogenic and climatic factors. Natural resources management critically needs land use maps and simulation of its changes for understanding the interaction and relationship between humans and natural phenomena, as well as for making premium decisions. ...
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Land use Changes have recently been increasing due to anthropogenic and climatic factors. Natural resources management critically needs land use maps and simulation of its changes for understanding the interaction and relationship between humans and natural phenomena, as well as for making premium decisions. Accordingly, present study has dealth with simulation of future changes land use of Kessillian watershed. Hence, land-use and land cover maps of the catchment was prepared by using multi-period Landsat images captured in 1986, 2000, and 2011. Then, applying cellular automaton and Markov model, the land-use/land cover condition in 2011 was predicted 0.9 using ROC. Thereafter, this model was run for simulating land-use/land cover changes in 2030. According to the results of detection and simulation of changes, forest land reduction trend will continue but the area of rangelands and inhabited areas will expand. Agricultural lands will not seriously change due to steep slope and low fertility after several consequent plantings. In most cases, maximum changes occurred around the forest and rangeland areas and changes will decrease far from these margins. Markov model can precisely show the land changes in the area via time period and can anticipate the future of them. Therefore, this model can be applied in order to manage the land.
amin salehpour jam; Mohsen Mohseni Saravi; Javad Bazrafshan; Shahram Khalighi
Abstract
Investigation of drought event has a great importance in the natural resources management and planning water resources management. In this research, the effect of the climate change on drought characteristics in northwest of Iran was investigated using the HadCM3 model under A2 scenario. The statistical ...
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Investigation of drought event has a great importance in the natural resources management and planning water resources management. In this research, the effect of the climate change on drought characteristics in northwest of Iran was investigated using the HadCM3 model under A2 scenario. The statistical downscaling was executed using SDSM 4.2.9 and observed daily precipitation, observed predictors and large-scale predictors derived from the HadCM3 model. Afterwards the SPI was calculated for different time scales of 3, 12, 24 and 48 months in the observed period of 1977-2006 and three periods of 2007-2036, 2037-2066 and 2067-2096. Obtained results show that the mean annual precipitation at the stations of Ardebil, Khoy and Oroomieh was decreased in the future periods and it was also increased at the station of Tabriz in the future period. The Ardebil station with the depletion of 97 mm (32 %) in the fourth period than the observed period has maximum rate of the depletion. The results also show that the drought occurrence with more intensity, duration and frequency can occur in the future periods. The comparison of the results between different stations shows that the Ardebil station has the most intensity of dry period in time scales of 3, 12 and 24 months based on the maximum cumulative intensity of dry periods among the stations. On the time scale of 48 months, the Oroomieh station with the cumulative intensity of -92.78, has the most intensity of dry period between the different stations.
