Effect of climate change on rainfall characteristics in future periods (Case Study: Golestan province)

Background & objectives & Today, climate change has effect not only on the management levels of water resources but also has some implications in everyday life. Study of changing in key variables of temperature and precipitation with regard to the effects of climate change in coming years can be helpful for solving some problems such as drought, sudden floods. Since others researchers, have performed their analysis more than one stationary and just had to show changes in quantity, in this study it was trying to analyzes by location (region) is also to be considered. As well as increasing the number of models and downscaling techniques and the future simulation of periods due to increased uncertainty in the results of climate change, in this study, only a regional model and a downscaling methods were used. The purpose of this study is to investigate the effect of climate change on precipitation changes and extreme rainfall events in the next period (2040-2011) in two selected stations in Golestan province. In this study, it is used data from the database of Climate Research Unit (CRU), under four emission scenarios A1, A2, B1 and B2. HADCM3 regional model was used as boundary conditions. This model in the fourth assessment report (2007) was published and new models is for applied modeling. Rainfall data of two weather stations Ali abad Katoul and Mazrae nemooneh artesh, as the both Humid and semi -arid stations in Golestan Province, were downscaled by proportional method. And then precipitation data were interpolated using IDW (8) as statistical method, and finally the time series scenario of future climate change were calculated by the change factor method. To investigate number of occurrences of heavy rainfall with precipitation index greater than 50 mm was considered and high-risk months in each station, the incidence of extreme rainfall was predicted.
The results show that precipitation changes for both stations in autumn and early spring and winter and late and mid-summer increases. The maximum rainfall in November and January is expected that the increased intensity of floods warns at the beginning of winter. In Aliabad Katoul station with humid climate, precipitation changes for A1 scenario will occur with more intensity and more increase precipitation during autumn and early winter and late summer would be expected. In the more scenarios and in all seasons, changes in seasonal rainfall, increase in seasonal rainfall in the regions studied show. The largest increase precipitation in both stations, is occurred under the B2 scenario. The number of extent occurrences is expected to increase in future period, the increase in Ali abad Katoul station more will happen in late summer and early fall, but in Mazrae nemooneh artesh station in late autumn and early winter will increase, as well as the most of increase in extreme events Looking at the chart in more Ali abad katoul station of Mazrae nemooneh artesh. Also it is expected in the future, the extent precipitation will increase and the highest increase in Aliabad and Mazrae nemooneh artesh stations would happen in November and January, respectively. The number of high rainfall events (greater than 50 mm) and high precipitation levels increased in both stations; if the rate average precipitation not show significant changes. As a result, it can be concluded that the probability of occurrence of more heavy rainfall this has been an increased amount of annual rainfall. The results indicate that climate change could increase extreme events in Golestan province was rainingso that by increasing levels of carbon dioxide, the daily limit will increase the number of days with precipitation; in fact, it would be an increased frequency of flooding in the Golestan province.
Results from the base period 2010 -1981 and the future period 2040 -2011 have been analyzed and evaluated.
Results showed increasing in mean of annual precipitation Ali abad Katoul and Mazrae nemooneh artesh stations around 6/7 and 73/8 percent, respectively. Also expected in future period, the number of extent precipitation events will increase. Climate change could increase the number of extreme events precipitation in Golestan province, so that with increasing levels of carbon dioxide, the number of days with some precipitation will increaseIn fact, it would be an increased frequency of flooding in the Golestan province.