Water Vapor in Earth's Atmosphere

This image shows the global distribution of water vapor measured by the satellite's radiometer from October 3 to October 12, 1992. The highest values (indicated by red) occur in the western tropical Pacific Ocean and the eastern tropical Indian Ocean where the ocean surface waters are the warmest. Without this correction, a water vapor content of 5 grams per square centimeter in these regions would cause an altimeter measurement error of 32 centimeters; such an error could interfere significantly with the study of ocean circulation.

The atmospheric water vapor is important in itself because the heat released by its condensation into vapor fuels atmospheric circulation. Water vapor is also related to sea- surface humidity, which controls the transfer of latent heat (heat required by evaporating water) from the oceans to the atmosphere. In addition, it is a greenhouse gas that affects Earth's radiative heat balance. Monitoring the global water vapor content is thus an important task for understanding the role of the oceans in weather and climate change.