User:Softlavender/W

A wet season or rainy season is the time of year, covering one or more months, when most of the average annual rainfall in a region falls. The term green season is also sometimes used as a euphemism by tourist authorities. Areas with wet seasons are dispersed across portions of the tropics and subtropics. While Savanna climates and areas with monsoon regimes have wet summers and dry winters, Mediterranean climates like the western United States and peninsular Italy have wet winters and dry summers. Tropical rainforests technically do not have dry or wet seasons, since their rainfall is equally distributed through the year. Some areas with pronounced rainy seasons will see a break in rainfall mid-season when the intertropical convergence zone or monsoon trough move poleward of their location during the middle of the warm season. When the wet season occurs during the warm season, or summer, precipitation falls mainly during the late afternoon and early evening hours. The wet season is a time when air quality improves, freshwater quality improves, and vegetation grows significantly. Soil nutrients diminish and erosion increases. Animals have adaptation and survival strategies for the wetter regime. Unfortunately, the previous dry season leads to food shortages into the wet season, as the crops have yet to mature. Developing countries have noted that their populations show seasonal weight fluctuations due to food shortages seen before the first harvest, which occurs late in the wet season.

Character of the rainfall
The wet, or rainy, season covers one or more months when most of the average annual rainfall in a region falls. In areas where the heavy rainfall is associated with a wind shift, the wet season known as the monsoon. Since rainfall during the wet season is predominantly due to daytime heating which leads to diurnal thunderstorm activity within a pre-existing moist airmass, rainfall is mainly focused during the late afternoon and early evening hours. This also leads to much of the total rainfall each day falling during the initial minutes of the downpour, before the storms mature into their stratiform stage.

The situation is different for locations within the Mediterranean climate regime. In the western United States, during the cold season from September through May, extratropical cyclones from the Pacific ocean move inland into the region due to a southward migration of the jet stream during the cold season. This shift in the jet stream brings much of the annual precipitation to the region, and also brings the potential for heavy rain events. The peninsula of Italy experiences very similar weather to the western United States in this regard.

Effects
During the wet season, a combination of heavy rainfall and in some areas, such as Hong Kong, a wind more off the ocean, significantly improve air quality. The pH level of water becomes more balanced due to the charging of local aquifers during the wet season. Water also softens, as desolved materials lower in concentration during the rainy season. Leaching of soils during periods of heavy rainfall depletes nutrients. Erosion is also increased during rainy periods.

Life adaptations
Within the tropics and warmer areas of the subtropics, decreased salinity of near shore wetlands due to the rains causes an increase in crocodile nesting. The wet season is the main period of vegetation growth within the savanna climate regime. However, this also means that wet season is a time for food shortages before crops reach their full maturity. This causes seasonal weight changes for people in developing countries, with a drop occurring during the wet season until the time of the first harvest, when weights rebound. In tropical areas, when the monsoon arrives daytime high temperatures drop and overnight low temperatures increase. Tropical species of butterflies show larger dot markings on their wings to fend off possible predators and are more active during the wet season than the dry season.