A Qualitative View Of Clouds In The Equatorial Trough Zone

Oceanic tropical clouds are observed to occur at various length scales over the equatorial trough zone (an area around the intertropical convergence zone or ITCZ). As one proceeds from the subtropics towards the equator, the cloud types range from small stratocumulus, small cumulus (including trade cumulus), cumulus, cumulonimbus (isolated) and large mesoscale convective systems (MCSs)with a corresponding increase in the sea surface temperature (Fig. 1). Satellite observations of clouds and precipitation measurements from the Tropical Rainfall Measurement Mission (TRMM) satellite data indicate that the location of the ITCZ coincides with the region of maximum solar heating or warmest sea surface temperature (SST) and lies north of the equator by a few degrees latitude (during northern hemisphere summer). The ITCZ is itself composed of cumulonimbus clouds and MCSs and represents the rising branch of the Hadley cell. Pole ward of the ITCZ in association with the descending branch of the Hadley cell and colder SSTs, cloud populations are characterized by the presence of stratocumulus, trade cumulus and small cumulonimbus clouds.