An investigation of drought magnitude trend during 1975–2005 in arid and semi-arid regions of Iran

In addition to drought intensity, drought magnitude (DM) is an important parameter in drought analysis. Therefore, in this study, the drought intensity and DM trends are investigated based on the standardized precipitation index (3, 6, 9, 12, 18 and 24 monthly SPI time series) from 1975 until 2005 in 25 synoptic weather stations located in arid and semi-arid regions of Iran. Although the DM is commonly computed for negative SPI values, for analysis the wet years besides drought conditions, this study has also involved positive SPI values and therefore, each time series was divided into four drought intensity conditions as follows: drought (D; SPI values less than −1), normal near drought (ND; SPI values more than −1 and less than 0), normal near wet (NW, SPI values more than 0 and less than +1), and wet (W; SPI values more than 1). The non-parametric rank-based Mann–Kendall test was used to detect trends of SPI values (drought intensity and DM) for 3, 6, 9, 12, 18 and 24 monthly time scales. Based on the results, a considerable percentage (50 %) of the stations at the level of 0.05 showed a significant trend with regards to drought intensity when compared with the DM trend (5.8 %). Generally, it can be said that the arid and semi-arid areas of Iran had a negative SPI trend and it means the more drought severities. Also, the more frequent significant positive DM trend in comparison to negative ones is a sign of increasing DM during the three past decades.

[1]  Y. Niazi,et al.  Trend Detection of Drought in Arid and Semi-Arid Regions of Iran Based on Implementation of Reconnaissance Drought Index (RDI) and Application of Non-Parametrical Statistical Method , 2014, Water Resources Management.

[2]  T. McKee,et al.  THE RELATIONSHIP OF DROUGHT FREQUENCY AND DURATION TO TIME SCALES , 1993 .

[3]  D. C. Edwards,et al.  Characteristics of 20th Century Drought in the United States at Multiple Time Scales. , 1997 .

[4]  M. R. Kousari,et al.  An investigation of the Iranian climatic changes by considering the precipitation, temperature, and relative humidity parameters , 2011 .

[5]  Donald O. Whittemore,et al.  Non-parametric trend analysis of water quality data of rivers in Kansas , 1993 .

[6]  M. R. Kousari,et al.  Minimum, maximum, and mean annual temperatures, relative humidity, and precipitation trends in arid and semi-arid regions of Iran , 2011 .

[7]  D. Helsel,et al.  Statistical analysis of hydrologic data. , 1992 .

[8]  Ximing Cai,et al.  Global water outlook to 2025: averting an impending crisis. , 2002 .

[9]  V. P. D. Silva.  On climate variability in Northeast of Brazil , 2004 .

[10]  H. Tabari,et al.  Temporal variability of precipitation over Iran: 1966-2005 , 2011 .

[11]  V. Singh,et al.  Trends in reference crop evapotranspiration over Iran , 2011 .

[12]  Luis S. Pereira,et al.  Spatial Patterns and Temporal Variability of Drought in Western Iran , 2009 .

[13]  V. Singh,et al.  A review of drought concepts , 2010 .

[14]  D. Kumar,et al.  Review of trend detection methods and their application to detect temperature changes in India , 2013 .

[15]  Mohammad Taghi Dastorani,et al.  The survey of climatic drought trend in Iran , 2011 .

[16]  H. C. S. Thom,et al.  a Note on the Gamma Distribution , 1958 .

[17]  P. Sen.  Estimates of the Regression Coefficient Based on Kendall's Tau , 1968 .

[18]  B. Lloyd‐Hughes,et al.  A drought climatology for Europe , 2002 .

[19]  T. Jiang,et al.  Temporal and spatial trends of precipitation and river flow in the Yangtze River Basin, 1961-2000 , 2007 .

[20]  R. Sneyers.  On the statistical analysis of series of observations. , 1991 .

[21]  Antonino Cancelliere,et al.  An analytical formulation of return period of drought severity , 2003 .

[22]  Michael J. Hayes,et al.  Appropriate application of the standardized precipitation index in arid locations and dry seasons , 2007 .

[23]  Mohammad Taghi Dastorani,et al.  Application of artificial neural networks on drought prediction in Yazd (Central Iran) , 2011 .

[24]  A. Mishra,et al.  Drought forecasting using stochastic models , 2005 .

[25]  Sheng Yue,et al.  The influence of autocorrelation on the ability to detect trend in hydrological series , 2002 .

[26]  S. C.,et al.  A NOTE ON THE GAMMA DISTRIBUTION , 1958 .

[27]  Q. Feng,et al.  Spatial and temporal pattern of precipitation and drought in Gansu Province, Northwest China , 2009 .

[28]  M. Abramowitz,et al.  Handbook of Mathematical Functions With Formulas, Graphs and Mathematical Tables (National Bureau of Standards Applied Mathematics Series No. 55) , 1965 .

[29]  M. R. Kousari,et al.  An investigation on reference crop evapotranspiration trend from 1975 to 2005 in Iran , 2012 .

[30]  S. Vicente‐Serrano,et al.  Dam effects on droughts magnitude and duration in a transboundary basin: The Lower River Tagus, Spain and Portugal , 2009 .

[31]  H. Tabari,et al.  Temporal trends and spatial characteristics of drought and rainfall in arid and semiarid regions of Iran , 2012 .

[32]  Ali Sarhadi,et al.  Rainfall trends analysis of Iran in the last half of the twentieth century , 2009 .

[33]  Davar Khalili,et al.  Regional classification for dryland agriculture in southern Iran , 2002 .