The long-term prevailing weather conditions in a region or place. There are a number of different schemes for dividing the Earth into climatic regions, the majority of which are based on a combination of indices of mean annual temperature, mean monthly temperature, annual precipitation totals, and seasonality. The climate of a place is influenced by several factors. Latitude determines the amount of solar radiation received, with the greatest in equatorial regions and the least in polar regions. Elevation affects both temperature and precipitation; mountainous areas are generally cooler and wetter. Location close to the sea or large bodies of water moderates temperature; continental areas are generally more arid and affected by greater extremes of temperature. Aspect is of local importance; in the N hemisphere, S- and W-facing slopes are warmer than N- and E-facing slopes. The scientific study of climate, describing and attempting to explain climatic differences from place to place, is known as climatology.