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Changing Pattern of Droughts during Cropping Seasons of Bangladesh

机译：孟加拉国农作物种植季节干旱的变化方式

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摘要

There has been a growing concern on temporal variations on drought characteristics due to climate change. This study compares meteorological drought characteristics for two different periods to quantify the temporal changes in seasonal droughts of 18 weather stations of the country. Fifty-five years rainfall and temperature data are divided into two different thirty-year periods, 1961-1990 and 1985-2014 and standardized precipitation evapotranspiration index (SPEI) for those periods are calculated to assess the changes. Four seasons in this study are selected as two major crop growing seasons namely, Rabi (November to April) and Kharif (May to October) and two critical periods for crop growth in term of water supply namely critical Rabi (March-April) and critical Kharif (May). Results show that moderate, extreme, and severe Rabi droughts has increased in 11, 9, and 4 stations out of 18 stations, respectively, and Kharif severe and extreme droughts has increased in 8 and 9 stations, respectively, In addition, the frequency analysis shows that the return periods have decreased during 1985-2014 at the stations where it was high during 1961-1990 and vice versa. This has made the spatial distribution of return periods of droughts more uniform over the country for most of the seasons. Increased return period of droughts in highly drought prone north and northwest Bangladesh has caused decrease in average frequency of droughts. Consequently, this result corresponds that Bangladesh experiences fewer droughts in recent years. Trend analysis of rainfall and temperature data reveals that significant increase of mean temperature and no significant change in rainfall in almost all months have increased the frequency of droughts in the regions where droughts were less frequent.
机译：人们越来越关注由于气候变化造成的干旱特征的时间变化。这项研究比较了两个不同时期的气象干旱特征，以量化该国18个气象站的季节性干旱的时间变化。五十五年的降雨量和温度数据分为两个不同的三十年期，1961-1990年和1985-2014年，并计算了这些时期的标准降水蒸散指数（SPEI）以评估变化。在该研究中，四个季节被选作两个主要作物生长季节，即拉比（11月至4月）和哈里夫（5月至10月）以及就供水而言的两个作物生长关键时期，即关键拉比（3月至4月）和关键时期。哈里夫（五月）。结果表明，在18个站中，分别有11个，9个和4个站的拉比干旱出现了中度，极端和严重干旱，而在8个和9个站中的Kharif严重和极端干旱分别增加了。结果表明，在1985-2014年期间，在1961-1990年期间较高的气象站，其返回期有所减少，反之亦然。这使得该国大部分季节干旱恢复期的空间分布更加均匀。在高度干旱的孟加拉国北部和西北部，干旱的返还期增加，导致平均干旱频率下降。因此，这一结果表明，孟加拉国近年来遭受的干旱较少。降雨和温度数据的趋势分析显示，在几乎不干旱的地区，平均温度的显着提高以及几乎所有月份的降雨量都没有明显变化，这增加了干旱发生的频率。

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