Column water vapor: a key constraint on
tropical deep convection

 

Column integrated water vapor (sometimes called "precipitable water", PW) apparently needs to exceed some critical threshold value to permit tropical deep convection. That is, PW exceeding a threshold is a necessary but not sufficient condition. PW is well measured over the ocean by satellites, with values ranging up to about 60 mm, so detailed visualizations can be examined. Patches of high or low PW can last for many days, despite precipitation rates of many mm/d, indicating that a very efficient maintenance mechanism is at work, keeping the PW values nearly constant. The moisture equation shows us that the sum of net condensation plus vertical advection by the associated heating-induced vertical motion must be this maintenance mechanism, and can be translated into new mathematical constraints on the process of convective activity as a whole.

Brian Mapes

 

Con traducción

 

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