Investigation of Iran Vulnerability Trend to Desertification with approach of climate change

Transcription

1 2011 2nd Internatonal Conference on Envronmental Scence and Development IPCBEE vol.4 (2011) (2011) IACSIT Press, Sngapore Investgaton of Iran Vulnerablty Trend to Desertfcaton wth approach of clmate change Peyman Mahmoud, Dostmohammad Kalm and Mohamad Reza Amrmorad Drought clmatology group Centre of Appled Meteorologcal Research Zahedan, Iran E-mal: Abstract-- In ths paper for study of amount of Vulnerablty of Iran to Desertfcaton s used of boclmatc ndex of UNEP (Unted Naton Envronment Programme). Frst Annual temperature average and total of annual precptaton from 45 synoptc meteorologcal statons for a 30 years perod ( ) has been collected the Meteorologcal Organzaton of Iran. Then UNEP ndex are computed for all of studed statons. In fnal usng Mann-Kendall graphcal statstcal test was nvestgated UNEP changes trend n Iran. On the bass of UNEP ndex s observed that most of areas of Iran have ard and sem-ard clmates. Wth respect to desertfcaton ntensty class, these two knds of clmates have classes of severe and very severe. After those two knds of clmates, ultra ard, dry sub-humd, very humd and subhumd clmates have the most area n Iran, respectvely. Results of Mann-Kendall test show that n three statons of Brjand, Tabrz and Mashhad, UNEP ndex changes trend have sgn of tendency from sem-ard clmate to ard clmate. Changes trend at two statons of Oroomeh and Khoy have tendency from dry sub-humd clmate to sem-ard clmate. Changes trend at staton of Sanandaj have sgn of replacement between sem-humd clmate wth sem-ard clmate and staton of Yazd have tendency to ultra-ard from ard clmate. But staton of Zabol at north of Sstan and Baluchstan provnce, have been alone staton that has had postve trend, that s ts changes trend have been from ultra-ard clmate to ard clmate. Changes trend of all of these statons at level of α 0.05 are sgnfcant. Keywords- Desertfcaton; UNEP ndex; Mann-Kendall test; Trend; Iran I. INTRODUCTION The researches done n many dfferent areas n Iran and the world show that the phenomenon of desertfcaton and ts result affects on the processes such as drought [3, 2, 16], desert area expandng [6], pasture runaton [15, 8, 11], sol brnng [14], underwater surface loss and ther qualty reducton[10], surface water reducton [13, 19], dares fatalty, poorness and poverty of thousands of people due to the mpermanent ecosystems (specally n ard and semard areas) and avarcous human. Clmate change was notced as an affectve feature on severty and expandng the desertfcaton process by many dfferent scentsts from dfferent vews. Of ts man subjects are changes n rate of earth surface Albedo due to surface coverng feature changes [12], the effect of ncreasng mne dust on cloud ran capablty rate reducton role [20, 7, 18], the effect of sea level temperature pattern on atmospherc process [4, 5, 18, 1, 17] and relaton between desertfcaton and drought [16]. As we know Iran s located n the desert zone of the north hemsphere and ts major part s surrounded wth subtropcal hgh pressure, so the most parts form ard and semard areas that have ranfall between mm. Desert and desertfcaton s a phenomenon that threatens our envronment and economcal lfe. Therefore, regardng the ncreasng heat n the world and successve droughts n the country, ths queston s rased that Does ths global heatng have affects on Iran vulnerablty n desertfcaton or not? So, ths survey ams to study the clmate change process UNEP ndex n Iran area usng Mann-Kendall graphcal statstcal test that s a suggestve method n the world Meteorologcal Organzaton for analyzng tme seres. II. MATERIALS AND METHODS To study Iran clmate change trend and ts effects on severty and expandng desertfcaton process, the data for two parameters about annual temperature average and monthly total ranfall of synoptc meteorologcal statons for a 30 year perod ( ) were obtaned from Iran Meteorologcal Organzaton. We can see the dstrbuton of studed statons n Iran n Fgure1. To study Iran vulnerablty to desertfcaton, we used Unted Naton Envronment Programme (UNEP) ndex. UNEP ndex s calculated as followng: P R (1) ETP 63

2 khoy tabrz ardabl 38 oroomeh anzal rasht ramsar babolsar gorgan 36 saghez ghazvn sabzevar mashhad zanjan tehran shahroud sanandaj nozheh torbat heydareh semnan kermanshah arak kashan 34 khoramabad tabas dezful esfahan brjand yazd 32 ahwaz shahre kord zabol abadan kerman 30 shraz zahedan bushehr fasa bam Fgure 1. locaton map and studed staton dstrbuton Where R s UNEP numercal ndex, P s the annual ranfall average n mm, ETP s potental evapotranspraton n mm. It s necessary to say that calculaton of potental evapotranspraton n ths relaton s done usng Thornthwate Index. At last, we classfy the ard, semard areas based on ths ndex (table 1). TABLE 1: ARID REGIONS CLASSIFICATION BASED ON UNEP ARID INDEX Desertfcaton UNEP ard ndex Clmatc Regons alarm class Real desert R<0.05 Ultra ard Very hgh 0.05<R<0.2 Ard Hgh 0.2<R<0.5 Sem-ard Md 0. 5<R<0.65 Dry sub-humd Low 0.65<R<0.75 Sub-humd Lack of Humd and very 0.75<R desertfcaton danger humd Then Provdng UNEP ndex tme seres for 45 studed statons through the country, we used Mann-Kendall graphcal statstcal test n the second stage to study ths ndex change trends. Kendall statstc (t) to test the null hypothess, lack of trend n tme seres was calculated based on the followng formula: 4 H t 1 N( N 1) (2) Where, H IS THE CUMULATIVE FREQUENCY OF SOME RANKS THAT ARE HIGHER EACH ROW AND N IS THE YEARS OF A STATISTICAL perod THAT IS 30 YEARS HERE. KENDALL STANDARD STATISTICS ( t 0 ) WAS CALCULATED AS THE FOLLOWING: t 0 ± tg bandar lengeh 4N N ( N 1) bandar abas IN THIS FORMULA, tg IS THE CONFIDENCE DEGREE OR SIGNIFICANT LEVEL THAT AMOUNTS TO 1.96 BASED ON THE jask ranshahr chabahar (3) t PROBABILITY LEVEL OF 95%? SO, IF THIS IS 1.96, 0 WILL EQUAL TO ± NOW, WE HAVE THREE FOLLOWING STATES REGARDING THE OBTAINED CRITICAL AMOUNT: If +0.21>t>-0.21, we don't have any tme seres trend. If t<-0.21, we have a negatve trend n tme seres. If t>+0.21, we have postve trend n tme seres. In the second step, f we have a sgnfcant trend, we wll determne tme and knd changes usng Mann-Kendall graphcal statstcs. To do ths, U and U' wll be calculated. We wll obtan these two components based on the followng formulas. V E U n n ( n 1) 4 ( n 1 )( 2n + 5) 18 t E ( V t ) In ths formula, n s the number of row. U' s nverse U. Mathematcal expectaton, Varance and U' component wll be calculated as 7-9: V E ( t ) ( N n + )( N n ) 4 1 ( N n + 1)( N n )( 2( N n + 1) + 5) ( t ) 75 t E U ( t ) V Calculatng above amounts, U and U' wll be drawn graphcally. Fnally, zonng of desertfcaton trend s drawn n Surfer software usng Krgng Method. III. RESULTS We can see that most of Iran s n center, east, south, North West and north east domnates wth ard and semard areas. Caspan Sea strp has humd and very humd clmate, Alborz northern heghts have sem humd clmate and ts south heghts and some parts of the west dry sub humd (4) (5) (6) (7) (8) (9) 64

3 clmate. The ultra ard clmate s seen n central Iran, Sstan plan and south of Sstan and Balouchestan provnce (Fg. 2). Calculatng the Mann-Kendall statstc for the whole studed statons shows a descendng trend n most of UNEP tme seres. But only 7 statons have had sgnfcant descendng trend such as Sanandaj, Yazd, Tabrz, Oroomeh, Khoy, Brjand and Mashad and Zabol staton was the only one that has had a sgnfcant postve ncreasng trend. So that n Brjand, Tabrz and Mashhad statons that have sem ard clmate and located n hgh level of desertfcaton hazard, UNEP ndex changng trend shows the clmate from sem ard toward ard clmate that ts desertfcaton hazard changes nto so hgh. (fgure3). Oroomeh and Khoy n North West of Iran have a trend toward sem-ard that n desertfcaton hazard level, they are tended from average to so hgh one. The trend of Sanandaj Staton n west of Iran shows replacng sub-humd and semard clmates and Yazd staton from ard nto ultra ard clmate. Of course ther desertfcaton hazard level wll be changed accordngly. (Fg. 3) we have ultra ard, sem most ard, hgh most and sem most clmates n Iran. The results of Mann-Kendall statstcs for three statons of Brjand, Tabrz and Mashhad, whch have semard clmates and are n hgh level of desertfcaton hazard, UNEP ndex change trend shows t from semard nto ard clmate, so ther hazard level changes nto the so hgh level. Two statons of Oroomeh and Khoy n North West of Iran wth sem most ard clmate, have tends toward semard clmate and so hgh level from the average one. The changes n Sanandaj n the west show the dsplacng sem most wth semard and Yazd from ard toward ultra ard one. So, ther desertfcaton hazard level wll change accordngly. Fgure 4 - Feldng trend of UNEP ard ndex changes throughout Iran Fgure 2. Iran clmate feldng usng UNEP ndex But, Zabol, n the north of Sstan and Balouchestan n east of Iran, was the only staton that has had postve UNEP trend, from ultra ard towards ard clmate. So, ths staton shows the desertfcaton hazard level from real desert nto so hgh level one. (Fg. 3) We can see the spatal dstrbuton of sgnfcant changes n tme seres of staton's UNEP ndex n fg. 4. In ths, t s clear that n west and North West and also north east are the areas that ther clmate changes wll lead to ther desertfcaton trend strengthenng. Although the statstcal perod s so short to comment about confrmng clmate changes, but we can know that as a marker of startng changes. IV. DISCUSSION Iran s located n the bg desert belt of Atlantc Ocean to Chna, has desertfcaton phenomenon due to brttle and senstve specfcatons of ts domnate clmate and human unconscous contacts wth envronment. We can see that most of Iran s domnated wth ard and semard clmate and s n hgh and so hgh level of desertfcaton hazard. Then, But, Zabol s the only one wth postve UNEP trend from ultra ard toward ard clmate. So, ts desertfcaton level s from real desert nto so hgh one. These changes n UNEP ndex, that can be the results of changes n the other clmate elements such as mnmum temperature, maxmum temperature and ranfall amount, were studed before by Tavoos et al [19]. Ther results confrm these changes especally n the west and North West. If these clmatc stuatons follow wth other strengthenng desertfcaton elements such as destroyng jungles, underwater source decrease, water eroson can be effectve n destroyng ths land. So, each change n the clmate wll be notced as the frst nfluental chan n other desertfcaton processes. REFERENCES [1] A. Gannn, R. Saravanan and P. Chang., Ocean forcng of Sahel ranfall on nterannual to nterdecadal tme scales. Scence, 302, pp [2] C. J. Tucker, and S. E. Ncholson, "Varatons n the sze of the Sahara desert from 1980 to 1997," Ambo, Vol.28, No. 7, pp ,1999. [3] C. J. Tucker, H. E. Dregne, and W. W. Newcomb, "Expanson and contracton of the Sahara desert from 1980 to 1990," Scence, 253, pp , [4] C. K.Folland, J. Owen, M. N. Ward, and A. Colman," Predcton of seasonal ranfall n the Sahel regon usng emprcal and dynamc methods," Journal of Forecastng, 10, pp , [5] C. K.Folland, T. N. Palmer, and D. E. Parker, "Sahel ranfall and worldwde sea temperature," Nature, 320, pp ,

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5 Fgure 3. U and U' change dagrams, the UNEP ard ndex of statons wth meanngful trend 67