Relative Humidity (RH) = (Actual Vapor Density) -------------------- X 100% (Saturation Vapor Density)
Relative humidity can be expressed by partial vapor and air pressure, density of the vapor and air, or by the actual mass of the vapor and air. Relative humidity is usually expressed in per cent and abbreviated by φ or RH. Precipitation is when moisture in clouds condenses and become too heavy to stay in the air so they fall to earth as precipitation in the forms of hail, snow, sleet, rain, freezing rain. Rain develops when the growing cloud droplets become too heavy and fall to earth. Hail is when a large frozen raindrop which falls through certain layers of the cloud and liquid freezes onto them forming ice pellets that will grow bigger as the hail falls. Freezing rain can cause major damage to an area. Freezing rain is usually found at the narrow band on the cold side of a warm front were the surface temperature is just below freezing. Global climate change is a change in the long term weather patterns that characterize the regions