assessment of the precipitation and temperature changes over south east iran using downscaling of general circulation models outputs

نویسندگان

محسن حمیدیان پور

استادیار گروه اقلیم شناسی، دانشگاه سیستان و بلوچستان، زاهدان، ایران محمد باعقیده

استادیار گروه اقلیم شناسی، دانشگاه حکیم سبزواری، سبزوار، ایران مجسن عباس نیا

دانشجوی دکتری اقلیم شناسی، دانشگاه سیستان و بلوچستان، زاهدان، ایران

چکیده

introduction numerous studies have demonstrated the relationship between the amount of co2 in the atmosphere and climate change. in this respect, developed countries have an undeniable role and cause serious damage to earth environment throughout the world. ipcc’ forth evaluation report implies that adding greenhouse gases to the atmosphere during recent decades prevents the heat rays to emit which, in turn, cause atmospheric temperature to increase. during the past centuries, the temperature has increased by 3 to 6 degrees centigrade, with a rapid speed in the recent decades. it is believed that if greenhouse gases continue to increase at the present rate, an average increase in temperature, from 1c to3.5c, is expected by the year 2100. therefore, it is necessary to study and evaluate climate changes in the future decades so as to plan a proper environmental program corresponding to future climate conditions, consequently reduce its unfavorable effects. with the uncertainty in atmospheric circulation models being taken into account, the present study investigates the temperature and precipitation changes in southeastern iran during the following periods: 2011-30, 2044-65, and 2080-99. material and methods we have used two datum groups, namely, observed data and model data. these are including maximum and minimum temperature, precipitation and solar radiation. the period, 1983-2007, was chosen as the observed period; data from weather synoptic stations were gathered. the required data for general circulation models including ipcm4, ncccm3, hadch3, and incm3 with three scenarios of a1b, a2, b1 were gathered from the two reference networks, canada climate change reference and data bank of lars-wg5.1. the most upgraded version of lars-wg5.1 was used to evaluate climate change in eastern south of iran. this version observes the forth report on ipcc. therefore, it uses the outputs of 15 general circulation models with a1b, a2, and b1 scenarios. four climate models with three shared scenarios were used in this study. time series of the observed data from synoptic stations in eastern south of iran were compared with those of ipcm4, ncccm3, hadch3, and incm3 in similar periods with a1b, a2, and b1 scenarioes. to do so, first, average time series of each station were computed using temperature and precipitation data from synoptic stations; then, monthly thermal data and those of gcm fall values during the study period were received from cccsn (canada). finally, the mentioned data were compared with the average temperature and precipitation during the study period. to investigate the uncertainty resulted from employing various gcm models, weighting method of averages of the observed temperature and precipitation was used. results and discussions general circulation models don’t have equal results in estimating long-term temperature and precipitation. this indicates the existing uncertainty in their outputs. analysis by t-test and chi square statics results for all stations, revealed no significant difference between the modeled and observed values at p

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جلد ۴۸، شماره ۱، صفحات ۱۰۷-۱۲۳

کلمات کلیدی
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d a t a f r o m w e a t h e r s y n o p t i c s t a t i o n s w e r e g a t h e r e d . t h e r e q u i r e d d a t a f o r g e n e r a l c i r c u l a t i o n m o d e l s i n c l u d i n g i p c m 4 ' , ' n c c c m 3 ' , ' h a d c h 3 ' , ' a n d i n c m 3 w i t h t h r e e s c e n a r i o s o f a 1 b ' , ' a 2 ' , ' b 1 w e r e g a t h e r e d f r o m t h e t w o r e f e r e n c e n e t w o r k s ' , ' c a n a d a c l i m a t e c h a n g e r e f e r e n c e a n d d a t a b a n k o f l a r s ' , ' w g 5 . 1 . t h e m o s t u p g r a d e d v e r s i o n o f l a r s ' , ' w g 5 . 1 w a s u s e d t o e v a l u a t e c l i m a t e c h a n g e i n e a s t e r n s o u t h o f i r a n . t h i s v e r s i o n o b s e r v e s t h e f o r t h r e p o r t o n i p c c . t h e r e f o r e ' , ' i t u s e s t h e o u t p u t s o f 1 5 g e n e r a l c i r c u l a t i o n m o d e l s w i t h a 1 b ' , ' a 2 ' , ' a n d b 1 s c e n a r i o s . f o u r c l i m a t e m o d e l s w i t h t h r e e s h a r e d s c e n a r i o s w e r e u s e d i n t h i s s t u d y . r n t i m e s e r i e s o f t h e o b s e r v e d d a t a f r o m s y n o p t i c s t a t i o n s i n e a s t e r n s o u t h o f i r a n w e r e c o m p a r e d w i t h t h o s e o f i p c m 4 ' , ' n c c c m 3 ' , ' h a d c h 3 ' , ' a n d i n c m 3 i n s i m i l a r p e r i o d s w i t h a 1 b ' , ' a 2 ' , ' a n d b 1 s c e n a r i o e s . t o d o s o ' , ' f i r s t ' , ' a v e r a g e t i m e s e r i e s o f e a c h s t a t i o n w e r e c o m p u t e d u s i n g t e m p e r a t u r e a n d p r e c i p i t a t i o n d a t a f r o m s y n o p t i c s t a t i o n s ; t h e n ' , ' m o n t h l y t h e r m a l d a t a a n d t h o s e o f g c m f a l l v a l u e s d u r i n g t h e s t u d y p e r i o d w e r e r e c e i v e d f r o m c c c s n ( c a n a d a ) . f i n a l l y ' , ' t h e m e n t i o n e d d a t a w e r e c o m p a r e d w i t h t h e a v e r a g e t e m p e r a t u r e a n d p r e c i p i t a t i o n d u r i n g t h e s t u d y p e r i o d . t o i n v e s t i g a t e t h e u n c e r t a i n t y r e s u l t e d f r o m e m p l o y i n g v a r i o u s g c m m o d e l s ' , ' w e i g h t i n g m e t h o d o f a v e r a g e s o f t h e o b s e r v e d t e m p e r a t u r e a n d p r e c i p i t a t i o n w a s u s e d . r n r e s u l t s a n d d i s c u s s i o n s r n g e n e r a l c i r c u l a t i o n m o d e l s d o n ’ t h a v e e q u a l r e s u l t s i n e s t i m a t i n g l o n g ' , ' t e r m t e m p e r a t u r e a n d p r e c i p i t a t i o n . t h i s i n d i c a t e s t h e e x i s t i n g u n c e r t a i n t y i n t h e i r o u t p u t s . a n a l y s i s b y t ' , ' t e s t a n d c h i s q u a r e s t a t i c s r e s u l t s f o r a l l s t a t i o n s ' , ' r e v e a l e d n o s i g n i f i c a n t d i f f e r e n c e b e t w e e n t h e m o d e l e d a n d o b s e r v e d v a l u e s a t p ' ]

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