An Assessment of the Projected Future Intra-Seasonal Rainfall Characteristics in Uganda

Rainfall is a key climate parameter that affects most operations that affect human life, especially in the tropics. Therefore, understanding the various factors that affect the distribution and intensity of this rainfall is important for effective planning among the different stakeholders in the weather and climate sectors. This study aimed at understanding how intra seasonal rainfall characteristics, especially Consecutive Dry Days (CDD) and Consecutive Wet Days (CWD), in the two major rainfall seasons will change under two future climate scenarios of RCP4.5 and RCP8.5 in Uganda, covering two future periods of 2021-2050 and 2051-2080. The results indicate a high likelihood of reduced consecutive rainfall days, especially over the Northeastern regions of the country, for both 2021-2050 and 2051-2080. However, the trends in the entire country for the two major rainfall seasons, March to May and September to November, are not significant. Nonetheless, the distribution of these days is important for most agricultural activities during different stages of crop growth. The consecutive dry days show a fairly increasing trend in the eastern part of the country, particularly in the second season of September to November. An increase in consecutive dry days implies more frequent dry spells in the midst of the growing season, potentially affecting some crops during critical growth stages.

Dry and wet spell probability by Markov chain model-a case study of North Lakhimpur(Assam),India

For the purpose of crop planning and to carry out the agricultural practices,it is important to know the sequence of dry and wet periods.The present study was undertaken with the objectives to forecast dry and wet spell analysis using Markov chain model and also to find out the exact time of onset and termination of monsoon at study area for North Lakhimpur(Assam),India using weekly rainfall data for a period of 24 years.The results indicated that probability of occurrence of dry week is higher from week 1st to 14^(th) and also from week 41^(st) to 52^(nd).The range of probability of occurrence of dry week in these weeks varies from 41.67% to 100%.Probability of occurrence of wet week is higher from week 17^(th) to 40^(th).The range of probability of wet week in these weeks varies from 66.67% to 100%.Week 1^(st) to 4^(th) and 43^(rd) to 52^(nd) of the year remains under stress on an average,as there are 50% to 95.83% chances of occurrence of two consecutive dry weeks.The analysis showed that monsoon starts effectively from week 23^(rd)(4^(th) June to 10^(th) June)in North Lakhimpur.The week 25^(th)(18^(th) June to 24^(th) June)is ideal time for initiation of wet land preparation for growing short duration rice variety.Pre-monsoon effectively starts from week 14^(th)(2^(nd) April to 8^(th) April).On week 14^(th) sowing of summer maize(rain fed)may be done.Week 15^(th)(9^(th) April to 15^(th) April)is ideal time for initiation of wet land preparation for growing long duration rice variety.