ارزیابی خشک‌سالی هواشناسی در ایران با استفاده از شاخص «استانداردشدة بارش و تبخیر-تعرق(SPEI)»

نویسندگان

1 دکتری مدیر توسعه کاربردهای هواشناسی، سازمان هواشناسی کشور، تهران، ایران

2 دانش آموخته کارشناسی ارشد، کارشناسی مرکز ملی خشکسالی سازمان هواشناسی کشور، تهران، ایران

3 دانشجوی کارشناسی ارشد، کارشناسی مرکز ملی خشکسالی سازمان هواشناسی کشور، تهران، ایران

چکیده

این تحقیق به بررسی اثر عوامل دما، بارش و تبخیر–تعرق در تعیین خشک‌سالی می‌پردازد. مجموع این تأثیرات در شاخص استاندارد‌شدة بارش وتبخیر- تعرق ارزیابی شده‌اند. از این رو در این مقاله کوشش شده است تا با مطالعة موردی در یک دورة یک‌ساله (چهار فصل)، خشک‌سالی کشور به کمک این شاخص (به صورت سه‌ماهه) بررسی شود. داده‌های دما و بارش برای تعیین ناهنجاری‌ها و شاخص خشک‌سالی استانداردشدة بارش وتبخیر-تعرق در دورة مورد نظر از سازمان هواشناسی کشور دریافت شده است. نتایج این تحقیق نشان می‌دهد که عامل تبخیر–تعرق، نقش مؤثری در تغییر شدت خشک‌سالی دارد، به گونه‌ای که با وجود افزایش (کاهش) بارش در مقایسه با میانگین بلندمدت به‌ویژه در بخش‌های جنوبی کشور، به علت افزایش (کاهش) تبخیر–تعرق، شدت خشک‌سالی افزایش (کاهش) یافته است. بنابراین از آنجا که خشک‌سالی پدیده‌ای وابسته به چند متغیر است، به نظر می‌رسد در کنار عامل بارش، می‌توان عامل تبخیر–تعرق را به‌ویژه برای بخش‌های جنوبی کشور و فصل‌های گرم سال لحاظ کرد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Assessment of meteorological drought in Iran using standardized precipitation and evapotranspiration index (SPEI)

نویسندگان [English]

  • Sahar Tajbakhsh 1
  • Nasrin Eisakhani 2
  • Amin Fazl Kazemi 3
1 Islamic Republic of Iran Meteorological Organization (IRIMO)
2 M.Sc, Expert of National Drought Center I.R. of Iran Meteorological Organization (IRIMO), Tehran, Iran
3 M.Sc. Student, Expert of National Drought Center I.R. of Iran Meteorological Organization (IRIMO), Tehran, Iran
چکیده [English]

Drought is one of the main natural causes of damages to the agriculture, economy, and environment. After a long period without precipitation, drought usually occur. Determination of the start time, end, and extent of drought is very difficult. Quantitative determination of the severity, magnitude, and duration of drought is very difficult.  Several factors such as rainfall, temperature, evaporation, relative humidity affect the incidence, severity, and duration of droughts. The basic characteristic of drought, according to the available water resources, including ground water, surface water, snow pack, and water supply have been discussed by many scientists. In addition, some studies have examined the importance of temperature in determination of drought conditions systematically. Precipitation and temperature assessments in Palmer index show that this index has similar the same changes of precipitation and temperature parameters, and only small fluctuations of temperature can be controlled by precipitation. Thus, drought indices, which include temperature data in formulas (like Palmer Index), especially for applications of climate forecasts are appropriate. However, the necessity of several quantitative drought indices has not been considered in different hydrological systems and only different values of Palmer Index for drought types has been used. Thus, the drought is formulated according to three variables precipitation, temperature, and potentiality of evapotranspiration (PET) in a new index called the Standardized Precipitation and evapotranspiration (SPEI). SPEI merges the Palmer Index sensitivity with evapotranspiration (based on temperature fluctuation) using simple computation while considering multi-scale nature of the Standardized Precipitation Index (SPI). This index was first introduced in 2009 by Vicente Serrano et al. The present study is an attempt to investigate the use of SPEI in drought evaluation in Iran.
Total precipitation and average temperature data are considered for 104 synoptic stations across Iran. The meteorological data have been obtained from the Islamic Republic of Iran Meteorological Organization (IRIMO). The statistical periods are between 25 to 30 years (25 stations on a 25-year period and information about the rest of the stations is for a 30-year period). The interpolation and visualization of meteorological parameters and indices were performed using Arc Map 9.3 GIS software. In order to calculate SPEI, first, total precipitation is determined for the considered period (month, quarter, etc.) and year for each station. Then using the data and methodology the precipitation for each station was calculated using Thornthwaite method. Then potential evapotranspiration is deducted from the total precipitation for each station in considered time periods and years. With skewness calculation, the mean and standard deviations of the data set are determined. By assuming “n” is the number of precipitation data and” m” is the sequence number, the probability of the amounts of precipitation is calculated. Using the probability of precipitation and the inverse gamma function, the corresponding precipitation is determined. Next, using the probability of precipitation and the inverse normal function with mean and standard deviation, the corresponding precipitation is counted. Now, the reported station precipitation, gamma precipitation and normalized precipitation for each station are available. Thus, the probability density function of station precipitation and the corresponding cumulative function of the probability density function can be calculated and SPEI can be determined after normalization. Thus, drawing and analysis of the abnormal patterns of temperature, precipitation, and evapotranspiration for the long-term average and seasonal SPEI can be made. The results show that due to considerable decrease in temperature in winter, the effect of evapotranspiration may not be significant. During spring, summer and autumn the effect of evapotranspiration is influenced heavily on precipitation in most provinces, especially the southern provinces of Iran (including Hormozgan, Sistan- Baluchestan, Fars and Khuzestan) and drought has intensified (weaken) while precipitation abnormal has increased(decreased). Regarding the geographical situation of Iran (arid and semiarid), index of evapotranspiration, especially during the warm season in most parts of the country had an impact on the determination of droughts and hence, it will be better to consider in addition to precipitation, for assessing drought.

کلیدواژه‌ها [English]

  • Meteorological drought
  • Standardized precipitation evapotranspiration index (SPEI)
  • Geographical Information System (GIS)
  • Potential of Evapotranspiration (PET)
 
1-Abramopoulos, F., C. Rosenzweig, and B. Choudhury, 1988, Improved ground hydrology calculations for global climate models (GCMs): Soil water movement and evapotranspiration, J. Climate, 1, 921–941.
2- Abramowitz, M., and I. A. Stegun, 1965: Handbook of Mathematical Functions, with Formulas, Graphs, and Mathematical Tables. Dover Publications, 1046 pp.
3-Allen, R. G., L. S. Pereira, D. Raes, and M. Smith, 1998, Crop evapotranspiration: Guidelines for computing crop water requirements, FAO Irrigation and Drainage Paper, 56, 300 pp.
4-Burton, I., R. W. Kates, and G. F. White, 1978, The Environment as Hazard, Oxford University Press, 240 pp.
5- Chang, T. J., and X. A. Cleopa, 1998, A proposed method for drought monitoring, Water Resour. Bull., 27, 275–281.
6-Dubrovsky, M., M. D. Svoboda, M. Trnka, M. J.Hayes, D. A. Wilhite, Z. Zalud, and P. Hlavinka, 2008, Application of relative drought indices in assessing climate-change impacts on drought conditions in Czechia, Theor. Appl. Climatol., 96, 155–171.
7-Dupisani, C. G., H. J. Fouche´ , and J. C. Venter, 1998, Assessing rangeland drought in South Africa, Agric. Syst., 57, 367–380.
8-Gonza´ lez, J., and J. B. Valde´ s, 2006, New drought frequency index: Definition and comparative performance analysis, Water Resour. Res., 42, W11421, doi:10.1029/2005WR004308.
9-Heim, R. R., 2002, A review of twentieth-century drought indices used in the United States, Bull. Amer. Meteor. Soc., 83, 1149–1165.
10-Hu, Q., and G. D. Willson, 2000: Effect of temperature anomalies on the Palmer drought severity index in the central United States. Int. J. Climatol.,20, 1899–1911.
11-Jones, P. D., and A. Moberg, 2003, Hemispheric and large-scale surface air temperature variations: An extensive revision and an update to 2001, J. Climate, 16, 206–223.
12- Keyantash, J. A., and J. A. Dracup , 2004, An aggregate drought index: Assessing drought severity based on fluctuations in the hydrologic cycle and surface water storage, Water Resour. Res., 40, W09304, doi:10.1029/2003WR002610.
13- Keyantash, J. A., and J. A. Dracup, 2002, The quantification of drought: An evaluation of drought indices, Bull. Amer. Meteor.Soc., 83, 1167–1180.
14-Khan, S., H. F. Gabriel, and T. Rana, 2008, Standardized precipitation index to track drought and assess impact of rainfall on watertables in rrigation areas, Irrig. Drain. Syst., 22, 159–177.
15- Martinez, J., Lopez, B.C., Adell, N., Badiella, L. and Ninyerola, M. 2008, Twentieth century increase of Scots pine radial growth in NE Spain shows strong climate interactions, Global Change Biology, 14, 2868-2881.
16- Mavromatis, T., 2007, Drought index evaluation for assessing future wheat production in Greece, Int. J. Climatol., 27, 911–924.
17- McKee, T. B., N. J. Doesken, and J. Kleist, 1993, The relationship of drought frequency and duration to time scales. Preprints, Eighth Conf. on Applied Climatology. Anaheim, CA, Amer. Meteor. Soc., 179–184.
18- Patel, N. R., P. Chopra, and V. K. Dadhwal, 2007, Analyzing spatial patterns of meteorological drought using standardized precipitation index, Meteor. Appl., 14, 329–336.
19- Rebetez, M., H. Mayer, O. Dupont, and A. Menzel, 2006, Heat and drought 2003 in Europe: a climate synthesis, Ann. For. Sci., 63, 569-577.
20-Sheffield, J., and E. F.Wood, 2008, Projected changes in drought occurrence under future global warming from multi-model, multi-scenario, IPCC AR4 simulations, Climate Dyn., 31, 79–105.
21- Sims, A. P., D. dutta, S. Nigoyi, and S. Raman, 2002: Adopting drought indices for estimating soil moisture: A North Carolina case study. Geophys. Res. Lett.29, 1183. doi:10.1029/2001GL013343.
22-Singh, V. P., H. Guo, and F. X. Yu, 1993, Parameter estimation for 3-parameter log-logistic distribution (LLD3) by Pome. Stochastic Hydrol. Hydraul., 7, 163–177.
23-Solomon, S., D. Qin, M. Manning, M. Marquis, K. Averyt, M. M. B. Tignor, H. L. Miller Jr., and Z. Chen, Eds., 2007,Climate Change 2007: The Physical Science Basis, Cambridge University Press, 996 pp.
24-Szalai, S., Cs. Szinell, and J. Zoboki, 2000, Drought monitoring in Hungary. Early Warning Systems for Drought Preparedness and Drought Management, World Meteorological Organization Rep, WMO/TD 1037, 182–199.
25-Tsakiris, G., D. Pangalou, and H. Vangelis, 2007, Regional drought assessment based on the Reconnaissance Drought Index (RDI). Water Resour. Manage., 21, 821–833.
26-Thornthwaite, C. W., 1948, An approach toward a rational classification of climate, Geogr. Rev., 38, 55–94.
27-Vicente-Serrano, S., S. Begueri'a, and J.  Lo'pez-moreno,2009, A Multiscalar Drought Index Sensitive to Global Warming: The Standardized Precipitation Evapotranspiration Index, JOURNAL OF CLIMATE,23  , 1696-1718.
28- Vicente-Serrano, 2007, Evaluating the Impact of Drought Using Remote Sensing in a Mediterranean, Semi-arid Region. Nat. Hazards, 40, 173–208
29-. Vicente-Serrano, S. M., 2006, Differences in spatial patterns of drought on different time scales: An analysis of the Iberian Peninsula, Water Resour. Manage., 20, 37–60.
30-Vicente-Serrano, and J. I. Lo´ pez-Moreno, 2005, Hydrological response to different time scales of climatological drought: An evaluation of the standardized precipitation index in a mountainous Mediterranean basin, Hydrol. Earth Syst. Sci., 9, 523–533.
31-Wells, N., 2003, PDSI Users Manual Version 2.0. National Agricultural Decision Support System, http://greenleaf.unl.edu/ downloads/PDSI_Manual.pdf.
32-Wilhite, D. A., and M. H. Glantz, 1985, Understanding the drought phenomenon: The role of definitions, Water Int., 10, 111–120.
33-Wilhite, D. A., 1993, Drought Assessment, Management, and Planning: Theory and Case Studies. Natural Resource Management and Policy Series, Vol. 2, Kluwer, 293 pp.