As a simplification at the global scale, we assume that food availability is not a limiting factor for larval weight gain and modify the equation accordingly. Daily minimum and maximum temperatures, linearly approximated from the monthly values, determine survivorship rates. These rates are based on laboratory studies and anecdotal field observations, which could vary from what occurs in the field. At temperature extremes we set the survival factor to 0.00, since these studies indicate that mosquitoes at any life stage are unlikely to survive extreme temperatures. Moisture also affects mosquito survival.
Studies show eggs can survive desiccation for many months, but for hatching, water is necessary.
Larvae require water for survival, but pupae do not, and vapor pressure deficit affects adult mortality. We chose this depth as an average depth between typical ovipositional containers , such as discarded bottles, tires and water storage drums. By excluding human population densities and socioeconomic factors that might determine the types and densities of appropriate ovipositional containers, we strictly assess the effects of climate on mosquitoes. The number of mosquitoes in each grid cell is calculated per m2 of container surface water. Differences between precipitation and evaporation drive changes in water depth.