The fraction of water distributed in the atmosphere is surprisingly small, about 0.001 percent of the total. This water, however, is a driving force of active atmospheric phenomena through the latent heat exchange in the phase changing process (water vapor to cloud, to precipitation and snow) and the short dwell time of water. Devastatingly severe typhoons, for example, are provided their enormous energy almost solely by the latent heat release. In addition to this latent heat effect, water plays an important role in the radiation budget. Clouds reflect solar radiation at optical wavelengths and absorb infrared emission from the Earth's surface. These properties give clouds a bilateral character of cooling or warming the Earth depending on its reflectance and height. Water vapor is a major greenhouse gas on the Earth and plays an important role in determining the current atmospheric temperature.
AMSR and AMSR-E will contribute to the quantification of these phenomena by global observation of atmospheric geophysical parameters such as water vapor, cloud liquid water, and precipitation.
(Image: Global distribution of water vapor)