An atmospheric lake is a long-lived moisture-rich pool of slow moving water vapor. Currently, such pools are only known to exist over the western equatorial Indian Ocean (WEIO).^[1][2][3] Atmospheric lakes are formed when streams of water vapor separate from the South Asian monsoons to become isolated objects. These objects last for days at a time and can occur several times during the year.^[4][5]

Atmospheric lakes move water from one area and to other areas that are dry and semi-arid. Atmospheric lakes that occur away from the Equator sometimes become tropical cyclones.^[6][7]