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Meteorological Drought Index Mapping in Bangladesh Using Standardized Precipitation Index During 1981–2010

Md. Anarul Haque Mondol
Department of Geography and Environment, Jahangirnagar University, Savar, Dhaka 1342, Bangladesh

Iffat Ara
Department of Geography and Environment, Jahangirnagar University, Savar, Dhaka 1342, Bangladesh; 2 School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia

Subash Chandra Das
Department of Geography and Environment, Jahangirnagar University, Savar, Dhaka 1342, Bangladesh

Abstract/ Executive Summary:

Natural disasters are a major concern in Bangladesh, particularly drought which is one of the most common disaster in Bangladesh. Drought needs to be explained spatially to understand its spatiotemporal variations in different areas. In this paper, the meteorological drought has been shown by using the Standardized Precipitation Index (SPI) method and illustrated through the Inverse Distance Weighted (IDW) method across Bangladesh. We used rainfall data of 30 meteorological stations in Bangladesh during the study period of 1981–2010. The results indicate that drought has been fluctuating and it has become a recurrent phenomenon during the study period. The SPI depicted the drought conditions that plunged dramatically in 1981, 1982, 1985, 1987, 1989, 1992, 1994, and 1996 and then gradually improved in 2004, 2006, and 2009 in the country. The present study demonstrated that drought occurred in Bangladesh on an average of 2.5 years. Drought was more prominent in the northern, south-western, and eastern regions in Bangladesh compared to the rest of the areas of the country.The outcomes of the present study will help in during disaster management strategies, particularly drought, by initiating effective plans and adaptation remedies in different areas of Bangladesh.

Keywords: Drought Index Mapping, Bangladesh, Standardized Precipitation Index

Location: Bangladesh

Start Date: 00-00-1981

End Date: 00-00-2010

Program Area: Crop-Soil-Water Management

Commodity: Drought

Objectives:

The aim of the present study is to characterize the spatial and temporal pattern of meteorological drought across Bangladesh by using Standardized Precipitation Index (SPI) [34].

Methodology:

Study Area. The study area covers Bangladesh that is located in the tropics. In the present study, the 30 meteorological stations of Bangladesh Meteorological Department (BMD) were selected on the basis of the data for the study period of 1981 to 2010. 2.2. Rainfall Data. The data of rainfall of Bangladesh were obtained from the Bangladesh Meteorological Department (BMD). Monthly data of average rainfall over Bangladesh have been collected for a maximum period of 64 years, 1948–2011. Time series of 30 meteorological stations were then used for the period of 1981 to 2010 in the present study. 2.3. SPI Calculation and Drought Categories. There are many more drought indices to detect, analyze, and predict the drought related issues. The most commonly used drought indices are Standardized Precipitation Index (SPI) and Palmer Drought Severity Index (PDSI). Standardized Precipitation Index (SPI) is more flexible and simpler than other indices. This model of drought indices allows temporal analysis of drought in all time periods. As only single variable, rainfall is used for input and can help to take decision and predict drought easily. SPI analysis is suited for different time periods. The SPI classification is based on three-month, six-month, and twelve-month calculation in the present study [8]. Here three-month SPI covers January, February, and March. The six-month SPI covers the period of January–June and the twelve-month SPI covers the period of January–December. Three-month SPI indicates the conditions of short-term drought of the area while six-month SPI indicates medium short-term drought and twelve-month SPI indicates longterm drought of an area. The analysis of the SPI was performed by the Drought Index Calculator (DrinC), which was developed by the Laboratory of Reclamation Works & Water Resources Management, National Technical University of Athens. The software was downloaded from http:// www.ewra.net/drinc in 1st of June, 2013. The index is mainly based on an equiprobability transformation and numerically depends on the combined likelihood of a given precipitation occasion happening at a station. The noteworthy precipitation information of the station is fitted to a gamma appropriation, as the gamma transformation has been found to fit the precipitation conveyance entirely well. Before this the mean, standard deviation and the rainfall data were transformed by the log (In) and then the mean was calculated and also constant U, shape, and scale. The statistical significance of the differences among the three periods at each station was assessed using a Kruskal-Wallis test. The following drought categories were used during the study. 2.4. Drought Index Mapping and Justification of Use of IDW. The Geographic Information System (GIS) has been used for the mapping drought index. The Inverse Distance Weighted (IDW) method was considered in the study to interpolate the SPI station based results across Bangladesh where the power was considered as 2, the searching neighborhood was standard, including at least 10 neighborhoods, neighbors to include 15, major semiaxis was 1.52, minor semiaxis was 1.52, and the angle was 0. The Inverse Distance Weighting (IDW) is an established deterministic methods for SPI mapping and one of the most frequently used deterministic models in spatial interpolation. The IDW is the simple and intuitive deterministic interpolation method based on principle that sample values closer to the prediction location have more influence on the prediction value than sample values farther apart.

Source of Information: Advances in Meteorology, Volume 2017, Article ID 4642060, 17 pages

Article Link (Online Journal): https://doi.org/10.1155/2017/4642060

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The meteorological drought being a changing phenomenon in Bangladesh is mostly unpredictable over the study period. The spatiotemporal character of the meteorological drought of Bangladesh indicated that the country was vulnerable to drought incidents on the basis of the past rainfall records. The meteorological drought varied due to the temporal and spatial pattern of rainfall occurrences. The SPI depicted that the drought conditions plunged dramatically in some years whereas in other years they remained stable. Drought hits Bangladesh on an average of 2.5 years which was alarming for agriculture practices and environment issues. Drought was more prominent in northern and south-western regions of Bangladesh compared to the rest of the areas of the country. SPI is only based on rainfall. For this, it is easy to detect, monitor, and forecast meteorological drought in a region. The present study helps in understanding drought in different areas in Bangladesh using past rainfall performance. Further, the results may help in planning to take necessary actions to manage regional drought and reduce the adverse impacts of drought across Bangladesh.

Knowledge Management: Journal