Abstract

Drought is considered to be one of the most devastating natural hazards, causing widespread environmental and social damage in many parts of the world. Using standardized precipitation index, this work has assessed changes in the severity–area–frequency (SAF) relationship curve of seasonal droughts in Bangladesh. Changes were estimated for mild, moderate, severe and extreme droughts for the four climatic seasons; winter, pre-monsoon, monsoon, post-monsoon, and for the two major growing seasons; rabi (November to April) and kharif (May to October). Nineteen general circulation models (GCMs) of Couple Model Intercomparison Project 5 were used. The model output statistics approach was used to downscale GCM simulated rainfall for eighteen climate stations in Bangladesh. Changes in the SAF curve were computed for three periods (2010–2039, 2040–2069 and 2070–2099). The uncertainty band of the SAF relationship curve was then computed using the Bayesian bootstrap method at the 95% confidence level. The results reveal that moderate and severe drought categories have the highest return period and are likely to affect the region more than other types of droughts. The kharif season drought was found to be most pronounced and affected significant portions of the country during all return periods and severity categories. Projections also show that monsoon and kharif droughts would increase across Bangladesh in regards of severity and return period. Higher return period droughts were also projected to increase in aerial extent in the middle of this century (2040–2069).

中文翻译：

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在气候变化情景下评估孟加拉国季节性干旱的严重程度-区域-频率（SAF）

摘要

干旱被认为是最破坏性的自然灾害之一，在世界许多地方造成了广泛的环境和社会破坏。使用标准化的降水指数，这项工作评估了孟加拉国季节性干旱的严重程度-区域-频率（SAF）关系曲线的变化。估计四个气候季节的轻度，中度，重度和极端干旱的变化；冬季，季风前，季风，季风后以及两个主要生长季节；狂犬病（11月至4月）和哈里夫（五月至十月）。使用了偶对模型比较项目5的19个普通循环模型（GCM）。模型输出统计方法用于降低孟加拉国18个气候站的GCM模拟降雨量。计算了三个时期（2010-2039、2040-2069和2070-2099）的SAF曲线变化。然后使用贝叶斯自举法在95％置信水平下计算SAF关系曲线的不确定带。结果表明，中度和重度干旱类别具有最高的恢复期，并且比其他类型的干旱对区域的影响更大。在秋收在所有回归期和严重程度类别中，最严重的季节是干旱，并影响了该国大部分地区。预测还表明，就严重程度和恢复期而言，孟加拉国的季风和海里夫干旱将会增加。在本世纪中叶（2040年至2069年），预计较高的恢复期干旱也会在空中扩大。