Investigating dry spells in Malawi during the rainfall season

Abstract

This study investigated the occurrence of dry spells during the main rainfall seasons over Malawi so that the farming community and other stakeholders can use this information to reduce vulnerability of the agricultural produce to the negative impacts of dry spells within the season. The dataset used in the study was observed daily rainfall data from 10 synoptic stations for the period 1961 - 2012. A dry day was defined as a day with less than 1.0 mm of rainfall while for investigating dry spells 7 consecutive dry days, 10 consecutive dry days, and 15 consecutive dry days were used. Quality control was done on the data set. The number of occurrence of dry spells were determined using Instat software, time series plots were done with Microsoft Excel to show the trend lines. Significance of trends were analysed using the Mann-Kendall trend test. The time series plots for 7 consecutive dry days and for 10 consecutive dry days from Excel were showing increasing trends or decreasing trends but the Mann-Kendall trend test showed that all the trends were not significant. The time series plots for 15 consecutive dry days from Excel were showing increasing or decreasing trends but the Mann-Kendall trend test showed that one station had a significant decreasing trend while the remaining nine stations trends were not significant.