The analyses can be found here.
Background Information
The dominant species of malaria in Africa is Plasmodium falciparum. Its development rate is temperature dependent. The climatic conditions considered suitable for its development and transmission through the mosquito stage of its life cycle are temperatures within the range 18°C to 32°C. Below 18°C the parasite development ceases. Above 32°C the survival of the mosquito is compromised. Relative humidity greater than 60% is also considered as a requirement for the mosquito to survive long enough for the parasite to develop sufficiently to be transmitted to its human host stage. Rainfall and surface water is required for the egg laying and larval stages of the mosquito life cycle and monthly rainfall above 80mm is considered as a requirement.
The climate variables used here are derived on a macro-scale from historical records. We may use these variables to provide an illustration of where and when this combination of climatic conditions exist. However, we should also remember that mosquitoes will actively seek out micro-climatic conditions to maximize their chances of survival and this will have a significant bearing on actual transmission.
Note that the Annual_Sum variable is unlike the Percent Occurrence variables in that it is based on climatological averages only. In other words, it states the number of months during the year that the average climatological conditions, based on the 1951-2020 base period, met the requirements necessary for malaria transmission. The Percent Occurrence variables are based on the same 50-year period, but represent the percent of the time that those conditions were actually met.
Data Sources
Precipitation
Data: Monthly precipitation over land areas on a 0.5° x 0.5° lat/lon grid
Historical Base Period: 1951-2020
Data Source: University of East Anglia (UEA CRU TS 4.05)
Temperature
Data: Monthly mean temperature over land areas on a 0.5° x 0.5° lat/lon grid
Historical Base Period: 1951-2020
Data Source: University of East Anglia (UEA CRU TS 4.05)
Relative Humidity Climatology
Data: Monthly specific humidity data (converted to rh) on a 2.5° x 2.5° lat/lon grid
Historical Base Period: 1951-2020
Data Source: National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR CDAS/Reanalysis)
References
Gilles, H. M., and D. A. Warrell (eds), 1993: Bruce-Chwatt's Essential Malariology. Arnold Publishing, 340 pp.
Craig, M. H., R. W. Snow and D. le Sueur, 1999: A climate based distribution model of malaria transmission in sub-Saharan Africa. Parasitology Today, 15(3) 105-111. <
