Hydrologic Response of Increasing Minimum Air Temperature in North Karun Basin

Introduction1
The change climate and global warming is a problem in the world. The climate is changing and the global warming is happening. Increasing the green house gases compactness is the reason about this phenomenon (Dettinger et al, 2004, 2). According to IPPC report Average annual temperature of the earth has been raised between 0.3 to 0.6º because spreading the greenhouse gases and this report predicts this amount will increase between 1 to 3.5º till 2100(Masahbavani&Morid, 2005,41).
These are cusses drought, flood sharp, and snowmelt, storms and increasing air temperature in different regions. These phonemes are in the whole world but they have different together. Climate change is an important environmental challenge in recently years.
In the north Karun basin have altitude higher than 2500 m and snowfall. Therefore, it has supply water important role in Karun River. We will analysis the effect of minimum air temperature on snow cover and discharge changes in Karun River. In this basin, snowfall has more than rate of precipitation to whole basin.
According to studied in different regions in the world, rainfall annual has downward but heavy rains have upper ward trend. Average air temperature, maximum air temperature, minimum air temperature and evaporation have upper ward trend. In addition, flooding and flood huge have upper ward. However, these parameters have caused decreasing water resources.
That the temperature increasing, melting of polarized, the world’s seas level rise and change in are result of that. Among the negative affects about climate change are Non-uniformly distributed rainfall, increasing and continuity the droughts and finally on water resources in all over the world. North Karun basin has 2300km2 area. This basin is south west Iran. This basin is one of the basins important at supply water resources in southwest Iran. The volume water is resources almost 10billionm3 in North Karun basin.
We used to record by power ministry and meteorological organization in 1984-2014.These data are included air temperature minimum , ice daily, snow cover and discharge. In this research for changes assessment, simulation and forecast the minimum temperature has been used data as for 4 synoptic stations in the north Karun basin. Research period in stations divided to 2part:30 and 25 years. Therefore, the purpose of this research is evaluation changes of minimum temperature in the past and forecast that in the future and changes compare than observer period.
from CMIP5 were selected for future climate change projections over the HNZ under a very-low forcing scenarios (RCP2.6), a medium stabilization scenarios (RCP4.5) and a very high baseline emission scenarios(RCP8.5). CMIP5 data were interpolated to the spatial scale (0.4˚×0.4˚).there for downscaling by Matlab software (0.2˚ ×0.2˚). In the following we used for correction model in accordance with the equation:(Equ1) Also we used to of indexes Bias, RMSE and R for assessment models that their used in forecasting data in North Karun basin.One models of CMIP5 under, RCP4.5 and RCP8.5were utilized in this study.
The mention that for output CMIP5 and scenarios RCP4.5 and 8.5 is done compare, and finally the CMIP5 and MNA-44_ICHEC-EC, RCP4.5 scenario choice for simulation and forecast.
Eventually temperature changes were evaluated. In addition, we used to change snow cover of MODIS TERRA and Aqua satellite Image monthly for during 2000-2014.
-Mann- Kendall test one of the most important nonparametric tests is Mann- Kendall test. The following equation can be used: (Equ2) (Equ3) (Equ4) (Equ5) (Equ6) (Equ7) The climate change is causing water stress. The increasing air temperature, drought and decreasing water are signs climate change in the whole world. The results indicative to exist changes at minimum air temperature, snow cover and discharge in North Karun Basin. The results shown that minimum air temperature has upper ward at 95% and it is increasing between 0.1Cº to 4.4Cº in particular at cold season (November, December, January, February). In addition, Snow cover, ice daily and discharge have decreasing trend. Also, the results simulator by GCM shown that air temperature trend will perpetuate in this basin at future period. Therefore, the increasing air temperature minimum, decreasing snow cover and discharge are causing water stress in North Karun Basin and Karun River. The results show that air minimum temperature increased cause water resources decreasing and supply hydro-electric in the feature period