1. 1. Abdulmalek, A.A. and Y.T. Qassem. 2013. An analysis of dry spells patterns intensity and duration in Saudi Arabia. Middle-East Journal of Scientific Research, 13: 314-327.
2. Abramopoulos, F., C. Rosenzweig and B. Choudhury. 1988. Improved ground hydrology calculations for global climate models (GCMs): Soil water movement and evapotranspiration. Journal of Climate, 1: 921-941.
https://doi.org/10.1175/1520-0442(1988)001<0921:IGHCFG>2.0.CO;2 [
DOI:10.1175/1520-0442(1988)0012.0.CO;2]
3. Allen, R.G., M. Smith, L.S. Pereira and A. Perrier. 1994. An update for the calculation of reference evapotranspiration. ICID Bulletin of the International Commission on Irrigation and Drainage, 35-92.
4. Ansari, H. and K. Davari. 2008. Dry period zoning using standardized precipitation index in GIS environment. Geographical Research, 60: 97-108 (In Persian).
5. Ansari, M., Gh. Noori and S. Fotohi. 2016. Investigation of Temperature Precipitation and Flow Trend Using Nonparametric Mankendall (Case Study: Kaju River in Sistan and Baluchestan). Journal of Watershed Management Research, 7: 152-158 (In Persian).
6. Bazuhair, S.A., A. Gohani and Z. Sen. 1997. Determination of monthly wet and dry periods in Saudi Arabia. International Journal of Climatology, 17: 303-311.
https://doi.org/10.1002/(SICI)1097-0088(19970315)17:3<303::AID-JOC126>3.0.CO;2-K [
DOI:10.1002/(SICI)1097-0088(19970315)17:33.0.CO;2-K]
7. Begueria, S. and S.M. Vicente-Serrano. 2013. SPEI: Calculation of the standardized precipitation-evapotranspiration index. R package version 1.6. https://cran.r-project.org/web/packages/SPEI/index.html
8. Chang, T.J. and X.A. Cleopa. 1998. A proposed method for drought monitoring. Water Resources Bulletin, 27: 275-281. [
DOI:10.1111/j.1752-1688.1991.tb03132.x]
9. Edward, D.C. and T.B. McKee. 1997. Characteristics of 20th century drought in the United States and multiple time scales. Climatology Report 972, Dept. Atmospheric Science, Colorado State University, Fort Collins, 155 pp.
10. Hargreaves, G.H. 1994. Defining and using reference evapotranspiration. Journal of Irrigation and Drainage Engineering, 120: 1132-1139. [
DOI:10.1061/(ASCE)0733-9437(1994)120:6(1132)]
11. Heim, R.R. 2002. A review of twentieth-century drought indices used in the United States. Bulletin of the American Meteorological Society, 83: 1149-1165. [
DOI:10.1175/1520-0477-83.8.1149]
12. Hu, Q. and G.D. Willson. 2000. Effect of temperature anomalies on the palmer drought severity index in the central United States. International Journal of Climatology, 20: 1899-1911.
https://doi.org/10.1002/1097-0088(200012)20:15<1899::AID-JOC588>3.0.CO;2-M [
DOI:10.1002/1097-0088(200012)20:153.0.CO;2-M]
13. Khalighi Sigaroudi, Sh., A. Sadeghi Sangdehi, Kh. Ousati and Y. Ghavidel Rahimi. 2009. The study of drought and wet year assessment models for stations in Mazandaran province. Iranian Journal of Range and Desert Research, 16 (1-34): 44-54 (In Persian).
14. McKee, T.B., N.J. Doesken and J. Kleist. 1993. The relationship of drought frequency and duration to time scales. In proceedings of the 8th conference on applied climatology, 17: 179-183.
15. Mostafazadeh, R. and M. Zabihi. 2016. Comparison of SPI and SPEI indices to meteorological drought assessment using R programming (Case study: Kurdistan province). Journal of the Earth and Space Physics, 42: 633-643 (In Persian).
16. Mostafazadeh, R., M. Shahabi and M. Zabihi. 2015. Analysis of meteorological drought using Triple Diagram Model in the Kurdistan province, Iran. Geographical Planning of Space Quarterly Journal, 17: 129-140 (In Persian).
17. Mostafazadeh, R., M. Vafakhah and M. Zabihi. 2015. Analysis of monthly wet and dry spell occurrence by using power laws in Golestan Province, Iran. Ecohydrology, 2: 29-43 (In Persian).
18. Neves, J. 2012. SPI: compute SPI index. R package version 1.1. https://cran.r-project.org/web/packages/spi/index.html.
19. Otun, J.A. 2010. Using precipitation effectiveness variables in indexing drought in semi-arid regions. African Journal of Agricultural Research, 5: 1784-1793.
20. Paulo, A.A., R.D. Rosa and L.S. Pereira. 2012. Climate trends and behavior of drought indices based on precipitation and evapotranspiration in Portugal. Natural Hazards and Earth System Sciences, 12: 1481-1491. [
DOI:10.5194/nhess-12-1481-2012]
21. R Core Team. 2015. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria, URL: http://www.R-project.org/.
22. Raziei, T., I. Bordi, L.S. Pereira and A. Sutera. 2011. Detecting impacts of a changing climate on drought characteristics in Iran. Proceedings of the VI International Symposium of EWRA on Water Engineering and Management in a Changing Environment, 113-126 pp. Catania, Italy.
23. Rezaee, M., A. Rezvani Mahmuee and S. Khaksefidi. 2014. Meteorological drought investigation through percent of normal rainfall during the period from 1972 to 2013 A.H. in Zahedan. International Journal of Basic Sciences & Applied Research, 3: 137-141.
24. Shafiei, M., M. Raeini-Sarjaz and R. Fazoula. 2014. Drought monitoring of Arjan-Parishan plain (Study area of Parishan Lake of Fars province). Journal of Watershed Management Research, 5: 46-63 (In Persian).
25. Soltani, S. and S. Sadati. 2007. Drought mapping over Isfahan province using standardized precipitation index (SPI). Iranian Journal of Watershed Management Science and Engineering, 1(2): 64-67 (In Persian).
26. Sushama, L., N. Khaliq and R. Laprise. 2010. Dry spell characteristics over Canada in a changing climate as simulated by the Canadian RCM. Global and Planetary Change, 74: 1-14. [
DOI:10.1016/j.gloplacha.2010.07.004]
27. Tajbakhsh, S., N. Eisakhani and A. Fazl Kazemi. 2015. Assessment of meteorological drought in Iran using standardized precipitation and evapotranspiration index (SPEI). Journal of the Earth and Space Physics, 41: 313-321 (In Persian).
28. Thornthwaite, C.W. 1948. An approach toward a rational classification of climate. Geographical Review, 38: 55-94. [
DOI:10.2307/210739]
29. Vafakhah, M. and M. Rajabi. 2005. Efficiency of meteorological drought indices for monitoring and assessment of drought in Bakhtegan, Tashk and Maharlo Lakes watershed. Desert, 2: 369-382 (In Persian).
30. Vicente-Serrano, S.M., S. Begueria and J.I. Lopez-Moreno. 2009. A multi-scalar drought index sensitive to global warming: the standardized precipitation evapotranspiration index- SPEI. Journal of Climate. 23: 1696-1718. [
DOI:10.1175/2009JCLI2909.1]
31. Wei, T. 2013. Corrplot: Visualization of a correlation matrix. R package version 0.73. http://CRAN.R-project.org/package=corrplot.
32. Wilhite, D.A. 2000. Drought as a natural hazard: concepts and definitions. Chapter 1, In D.A. Wilhite (Edited), drought: a global assessment, Natural Hazards and Disasters Series, Routledge Publishers, U.K, pp. 3-18.
33. Yousefi, Y. and J. Masoompour Samakosh. 2014. Temporal-spatial variability of the severest dry spells in the north-west of Iran. Desert, 19-1:17-25.
34. Zare Abyaneh, H., M. Ghabaei Sough and A. Mosaedi. 2015. Drought monitoring based on Standardized Precipitation Evaoptranspiration Index (SPEI) under the effect of climate change. Journal of Water and Soil, 29: 384-392 (In Persian).
35. Zolina, O., C. Simmer, K. Belyaev, S.K. Gulev and P. Koltermann. 2013. Changes in the duration of European wet and dry spells during the last 60 years. Journal of Climate, 26: 2022-2047. [
DOI:10.1175/JCLI-D-11-00498.1]