The Commodity Risk Management Group (CRMG) of the World Bank has developed a prototype Malawi Maize Production Index (MMPI), constructed from weather data recorded by the Malawi Meteorological Office weather stations throughout the country, to capture maize production levels in Malawi. The aim is to find a simple and objective indicator that can be used as a proxy measure of the countrywide exposure of Malawi maize production to drought and hence serve as a nation-wide food security indicator on which an insurance agreement could be written for the Government of Malawi (GoM).
However, this indicator turned out to be relatively poorly linked with crop yields. FAO proposed to use the tools included in the FAO AgroMetShell (AMS) software2 to derive an effective weather-based maize yield index (WYX, Weather Yield indeX) that could be used for crop insurance purposes in Malawi. AMS computes a crop specific water balance to derive value-added crop-weather variables that can be combined with other data (e.g. remote sensing inputs, farm inputs such as fertilizer use) and statistically related with crop yield using standard multiple regression techniques3. “Value-added crop-weather variables” are variables such as actual evapotranspiration that are know to be more meaningful than raw meteorological variables; see, for instance, the documents listed in footnote 3 for theory and references.