Objective Quantification of Drought Severity and Duration

469

293

Drought monitoring is an essential component of drought risk management. It is normally performed using various drought indices that are effectively continuous functions of rainfall and other hydrometeorological variables. A number of drought indices have been introduced and applied in different countries to date. This paper compares the performance of seven indices for drought monitoring in the Tehran province of Iran. The indices used include deciles index (DI), percent of normal (PN), standard precipitation index (SPI), China-Z index (CZI), modified CZI (MCZI), Z-Score and effective drought index (EDI). The comparison of indices is based on drought cases and classes that were detected in the province over the 32 years of data, as well as over the latest 1998-2001 drought spell. The results show that SPI, CZI and Z-Score perform similarly with regard to drought identification and respond slowly to drought onset. DI appears to be very responsive to rainfall events of a particular year, but it has inconsistent spatial and temporal variation. The SPI and EDI were found to be able to detect the onset of drought, its spatial and temporal variation consistently, and it may be recommended for operational drought monitoring in the Province. However, the EDI was found to be more responsive to the emerging drought and performed better.

Section: The Effective Drought Index (Edi)mentioning

confidence: 99%

Comparison of seven meteorological indices for drought monitoring in Iran

Morid

Smakhtin

Moghaddasi

2006

469

293

“…The EDI is an attempt to more accurately determine the exact start and end of a drought period. Unlike most drought indices, the EDI in its original form is calculated with a daily time step (Byun and Wilhite, 1996). The EDI is a function of 'precipitation needed for a return to normal' conditions (or to recover from the accumulated deficit since the beginning of a drought), which, in turn, is related to 'effective precipitation (EP)'.…”

Section: Drought Indicesmentioning

confidence: 99%

Assessment of areal interpolation methods for spatial analysis of SPI and EDI drought indices

Akhtari

Morid

Mahdian

et al. 2008

Drought monitoring is an essential component of drought risk management. Drought indices -functions of precipitation showing the severity of dryness during a particular time period -are often used for monitoring purposes. These indices may only be calculated originally at a limited number of sites where observations on climate variables are available. However, what is required for monitoring is to estimate the spatial distribution of drought severity over larger areas in the form of maps. In this article, several geostatistical methods including kriging, co-kriging and thin plate smoothing splines with and without secondary variables, as well as Thiessen polygons and weighted moving average were assessed for the derivation of maps of drought indices. The techniques are evaluated using 1-month Standardized Precipitation Index (SPI) and Effective Drought Index (EDI) at 43 climatic stations in the Tehran province of Iran. The results indicate that although kriging is the most accurate method, weighted moving average provides a reasonable accuracy combined with the simplicity and speed of the procedure, and thus, can be recommended for operational drought monitoring system in the region.

“…Although this implied that comprehensive research on the spatial and temporal characteristics of droughts over East Asia is necessary, the studies on droughts over East Asia have been very limited so far. Kang and Byun (2001) showed that the 2001 drought in Korea and China was abnormally strong using a daily drought index developed by Byun and Wilhite (1999), but they did not take into account any spatial relationships of drought occurrence and magnitude between the two countries.…”

Section: Introductionmentioning

confidence: 99%

Spatial and temporal comparisons of droughts over Korea with East Asia

Min

Kwon

Park

et al. 2003

146

To investigate the spatial and temporal relationships of drought occurrence and intensity between Korea and East Asia, the Standardized Precipitation Index (SPI), calculated from Climatic Research Unit (CRU) monthly precipitation data, was used from 1951 to 1996. It is found that the frequency of occurrence of droughts in Korea has significant time intervals of 2-3 and 5-8 years and has been increasing since the 1980s. Correlation and composite analyses showed that the occurrence of droughts over central eastern China, Manchuria, and the north coast of Japan was highly correlated with those in Korea. However, the time scales of occurrence of droughts over the three regions were different. Droughts in eastern China represented in-phase variations with those in Korea with a time interval of 5-8 years, whereas those in Manchuria occurred with a time interval of 15 years, and those in Japan had no coincident variations.To assess the feasibility of usage of proxy climate data in eastern China for the research of droughts in Korea during the pre-instrumental period, dry-wet indices in six regions of eastern China were correlated to the SPI values in Korea for the period of 1951-92 considering several time scales. Dry-wet indices of region V showed a larger correlation and the most similar trend to the droughts in Korea with a time scale of 5-11 years. This suggested an effective utilization of historical records and other proxy data in eastern China to understand extreme climatic events in Korea for the past 500 years.