International Research Journal of Applied and Basic Sciences © 2014 Available online at www.irjabs.com ISSN 2251-838X / Vol, 8 (9): 1316-1320 Science Explorer Publications Assessment of climatic parameters uncertainty under effect of different downscaling techniques Alireza Zamani Nuri 1 , Mohammadreza Farzaneh 2* , Kiamars Espanani 3 1. Assistant Professor, Department of Civil Engineering, Saveh Branch, Islamic Azad University, Saveh, Iran. 2. PhD Student in Water Resources Engineering, Water Engineering Department, Tarbiat Modares University, Tehran, Iran. 3. Post Graduated, Department of Water Engineering, Birjand University, Birjand, Iran. Corresponding Author email:m.farzaneh@modares.ac.ir ABSTRACT: One of the most discussed topics in climate change studies is uncertainty. New studies underline the importance of effect of different downscaling methods on the accuracy of outputs. Therefore, in this study the uncertainty of outputs in downscaling models of LARS-WG and SDSM in Kermanshah weather station has been examined for the climatic parameters of maximum temperature, minimum temperature, and precipitation, with an emphasis on A2 emission scenario and HADCM3. The results of SDSM and LARS-WG outputs have been investigated in base period in two states: with and without considering uncertainty. It was observed that, in general, both models are properly capable of simulating the existing conditions in base period. LARS-WG showed a better evaluation compared to SDSM for the parameter of precipitation. Thus, the priority of LARS-WG over SDSM in future periods implies that a decrease in precipitation for near future, and an increase in precipitation for middle and distant future are possible. Also, a rise in temperature based on the estimation provided by SDSM for future periods is anticipated as a result of this study. Key words: climate change, uncertainty, LARS-WG, SDSM, Karkhe basin, Kermanshah INTRODUCTION In climate change studies, different resources of uncertainty affect the final outcomes. One of these sources is that related to downscaling methods which plays a major part in producing the final result. Several studies have focused on this area, and we will discuss some of them in following sections. Wibly et al (2010) invented a comprehensive method to evaluate the effects of climate change by interconnecting regional climate models (HadCM3, CGCM2, CSIRO, and the two emission scenarios A2and B2) in a certain framework. In their case study of Kennet river, they showed how this comprehensive system can be used for observing different aspects of uncertainty in climate change and generalizing it to water resources and the quality of water in upside and downside of drainage networks. The results signify high uncertainty in climate change scenarios and its effects on supplying drinking water, compared to the uncertainty of water resources. The highest uncertainty was observed during summer months through fluctuations between GCM predictions of minimum river flow and its effect on ground water, nitrate leaching rate, and the long term process of surface water quality. In a study regarding sub-basin of Catt de Diable in Quebec, Canada with an area of 9700 Km2, the uncertainty of outputs in three downscaling models including LARS-WG, SDSM, and ANN was examined. Using bootstrap method and by comparing mean and variance of temperature and precipitation, dry and wet periods of precipitation and comparing them with observed data, it was concluded that SDSM provides better results than LARS-WG, which in turn shows more acceptable results than ANN (Khan et al, 2006). Examining the effects of different sources of uncertainty including downscaling methods (LARS-SDSM, HRD), AOGCM models, and emission scenarios in Behesht-Abad sub-basin of Northern Karoon river, Fakhri et al (2012) and Rostamian et al (2013) assessed the role of these resources to be more significant when approaching the middle future periods. In this study, with emphasis on A2 scenario and HADCM3 model, the uncertainty in outputs of downscaling models SDSM and LARS-WG in Karkheh basin would be examined.