Occurrence of wet and dry spells of rainfall in Bagan, Myanmar

Daily rainfall at Bagan in the central dry zone of Myanmar was analyzed to identify the occurrence of wet and dry spells of rainfall during the farming period. A wet season was identified from May to October and a dry season from November to April. The wet season can be divided into an early (May–June) and late (August–October) monsoon, separated by an inter-monsoon (July). The bimodal distribution of rainfall makes rainfed agriculture even more challenging in this dry area. A rainy season was defined as a duration that started from the first 5 days with at least 2 wet days (total of at least 10 mm of rainfall) without a maximum dry spell of 10, 15, or 20 days at least for 90 days. A period that satisfies only the onset condition but that is interrupted by a dry spell was classified as a false rainy season. Under the maximum dry spell conditions of 10, 15, and 20 days, rainy seasons were identified 5, 12, and 16 times, respectively. Dry spells up to 20 days long often occur during the farming period in Bagan and should be accounted for farm planning.