Suitability of different data sources in rainfall pattern characterization in the tropical central highlands of Kenya

Abstract

Uncertainty in rainfall pattern has put rain-fed agriculture in jeopardy, even for the regions considered high rainfall potential like the Central Highlands of Kenya (CHK). The rainfall pattern in the CHK is spatially and temporally variable in terms of onset and cessation dates, frequency and occurrence of dry spells, and seasonal distribution. Appraisal of the variability is further confounded by the lack of sufficient observational data that can enable accurate characterisation of the rainfall pattern in the region. We, therefore, explored the utilisation of satellite daily rainfall estimates from the National Aeronautics and Space Administration (NASA) for rainfall pattern characterisation in the CHK. Observed daily rainfall data sourced from Kenya meteorological department were used as a reference point. The observation period was from 1997 to 2015. Rainfall in the CHK was highly variable, fairly distributed and with low intensity in all the seasons. Onset dates ranged between mid-February to mid-March and mid-August to mid-October for long rains (LR) and short rains (SR) seasons, respectively. Cessation dates ranged from late May to mid-June and mid-December to late December for the LR and SR, respectively. There was a high probability (93%) of dry spell occurrence. More research needs to be done on efficient use of the available soil moisture and on drought tolerant crop varieties to reduce the impact of drought on crop productivity. Comparison between satellite and observed rain gauge data showed close agreement at monthly scale than at daily scale, with general agreement between the two datasets. Hence, we concluded that, given the availability, accessibility, frequency of estimation and spatial resolution, satellite estimates can complement observed rain gauge data. Stakeholders in the fields of agriculture, natural resource management, environment among others, can utilise the findings of this study in planning to reduce rainfall-related risks and enhance food security.

Changes and Variability in rainfall onset, cessation and length of rainy season in the IGAD region of Eastern Africa

“…In addition, the changes and variability in mean state of RODs and RCDs have direct impacts in terms of changes in variability of LRS over most parts of the region. The piece of information in this study de nitely helps rain-fed agriculture, food and wide range of cash crops, farmers to make decisions on crop varieties, where and when to plant and harvest.It is also worth emphasizing that the patterns of onset in march and retreat occurs gradually in December determined the longest Length of rainy season in the IGAD region is observed over most parts of Uganda and Nyanza and highlands of Western Kenya, which range between 240-300 days in average due to early rainfall in march and late cessation in December, which con rmed in study byNathan et al, (2020) over highlands of Western Kenya. This results in agreement partly with what reported study of RODs, RCDs and LRS over Uganda(Ocen et al, 2021) and Kenya(Mugalavai et al, 2008).…”

Soil water use efficiency under integrated soil management practices in the drylands of Kenya

“…The rainfall data was used in the calculation of the start and end of the season, and the length of the crop growth period. The onset date was the first three days that received a cumulative rainfall of more than 40 mm in a season [ 27 ]. The cessation date was the end of the rains.…”

Evaluation of satellite precipitation products for water allocation studies in the Sio-Malaba-Malakisi River Basin of East Africa

“…There has been increasing interest in the application of satellite precipitation products over East African regions of data scarcity (Näschen et al 2018;Oduor et al 2020;Pellarin et al 2020). A majority of the studies have focused around the greater Lake Victoria drainage basin considering its economic significance (Habib et al 2012;Williams et al 2015;Awange, 2021).…”