Study of diurnal variation of rainfall in Bangladesh using GSMaP data

Abstract

To study the diurnal variation of rainfall and possibility to use of Global Satellite Mapping of Precipitation (GSMaP) data in Bangladesh, GSMaP hourly data of spatial resolution of 0.1 degree by 0.1 degree and three hourly rain gauge data of 35 stations of Bangladesh Meteorological Department (BMD) are used. Daily, monthly, seasonal and yearly diurnal variation of rainfall and their spatial distribution are studied during the period 2001-2015. It is found that GSMaP data is well correlated with rain gauge data. The correlation coefficients between GSMaP and BMD rain gauge for 3-hourly, daily, monthly and yearly rainfall are found 0.71, 0.74, 0.82 and 0.66, respectively. From this study, it is found that monthly diurnal variation of BMD rain gauge rainfall showed two peaks of maximum rainfall; one at 0600 Local Standard Time (LST) and other at 1500 LST whereas GSMaP found these peaks at 0300 LST and 1500 LST. During pre-monsoon season both datasets found well matched maximum rainfall peak at 1500 LST (primary peak) and 21 LST (secondary peak). GSMaP found primary peak at 0300 LST and secondary peak at 1500 LST whereas rain gauge found these peaks at 0600 LST and 1500 LST during monsoon season. During the post-monsoon season the well matched primary and secondary peaks of rainfall of both data sets are found at 1500 LST and 0600 LST, respectively. In winter, both datasets showed only one peak of maximum rainfall at 0300 LST. Rain gauge measured yearly maximum rainfall over Bangladesh at 0600 LST with a secondary maximum peak at 1500 LST whereas GSMaP observed primary peak at 1500 LST with a secondary peak at 0300 LST. The spatial distribution of occurrence time of maximum rainfall showed that the western, north-eastern part of the country experiences maximum rainfall at 0300-0900 LST and central and southern part at 1800-2100 LST during pre-monsoon season. During monsoon season maximum rainfall is observed in the western and north-western region at 0300-0900 LST, whereas rest part of the country showed at 1200-1500 LST. In post-monsoon season, maximum rainfall occur in the western, north-western part of the country at 0900-1200 LST whereas central and southern part observed at 1200-1500 LST. Station wise analysis of diurnal variation of rainfall confirmed that most of the stations showed continental type diurnal variation during pre-monsoon and post-monsoon season whereas during monsoon and winter seasons dominated maritime type diurnal properties. Yearly average of station wise diurnal variation of rainfall confidently confirmed that Bangladesh is dominating the maritime type diurnal properties.