Assessing fitness for purpose: a validation of Ghanaian satellite rainfall within the context of participatory agricultural services and index insurance.

Satellite Rainfall Estimates (SRFEs) are becoming increasingly important in the world of food security, especially given that they provide over 30 years of high-resolution data across the tropics. As these regions are typically reliant on rain-fed agriculture and are vulnerable to weather shocks, SRFEs are now a key part of the weather risk management tool-kit. In recent years, SRFEs are finding practical use in applications such as agricultural “index” insurance, or programmes such as the Participatory Integrated Climate Services for Agriculture approach, (PICSA)*.

Many of these agricultural applications were originally developed around local historical weather statistics, obtained through the analysis of historical records from National Meteorological Services. This is a challenging process as [1] many countries don’t have a high-density historical gauge-network; [2] quality control is complex; and/or [3] there can be a large amount of missing data. These are particularly pressing issues for these applications because agricultural development interventions typically target remote and vulnerable agricultural regions, which are the least likely to have a good historical record. Attention has recently turned to SRFEs to assess whether they can help solve the problem.

However, assessing whether a given SRFE is appropriate for use is a new challenge. Conventional validations of SRFEs often center around a small variety of standardized statistics, which make it difficult to assess products’ fitness for purpose for use in applications such as insurance or PICSA. For example, the SRFE that is most appropriate for an extreme rainfall insurance product, or the one that best captures early season dry spells, might not be the most ‘skillful’ in a standard validation. Here, we use a large set of Ghanaian weather station data to validate SRFEs through the lens of the needs of PICSA and the drought insurance community.

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* PICSA builds the capacity of agricultural extension to enable farmers to use climate information in their planning and decision-making. Agricultural extension agents work with their national meteorological office to access weather forecasts and to develop local agriculturally relevant local historical weather statistics. These are then integrated into a holistic set of exercises that allow farmers to consider their management decisions within the context of this weather information. A 2015 survey found that 97% of ~6000 Ghanaian PICSA participants had made changes in their farming and livelihood activities based on the climatic information. PICSA has now expanded to reach many tens of thousands of farmers across the sub-Saharan Africa and Latin America.