Updrafts in Deep Tropical Convection

Deep convection in the tropics, sometimes called hot towers in the context of tropical storms, has been challenging to study because of both sampling and safety issues. There have been years of modeling of deep convection beginning with simple 1-D models (e.g., Simpson and Wiggert, 1969) to sophisticated dynamical models such as WRF. Thermodynamic arguments have shown that strong updrafts in tropical convection would require undilute updrafts, but these are difficult to achieve except in rare situations (Zipser 2003). In this paper, we briefly review some of the early controversies on updrafts in deep tropical convection. We then describe magnitudes and scales of vertical velocities from NASA field campaigns (CAMEX-3&4, TCSP, TRMM-LBA, etc.) derived from the NASA ER-2 down-looking Doppler Radar (EDOP), and from a handful of flight level penetrations of tropical convective towers by the NASA DC-8 such as in Tropical Storm Chantal and a few towers not associated with tropical storms. More recent measurements are added to the 2010 data in Heymsfield et al. (2010). These measurements are generally consistent with both Zipser (2003) thermodynamic arguments and observations, and from Fierro et al. (2009) WRF modeling results, i.e., a double-peaked updraft, one peak at lower levels associated with the latent heat of condensation, and a second peak at higher altitudes associated with the latent heat of fusion. Finally, we discuss the need for high-resolution measurements in convection on scales less than 1 km, as well as the need for improved observations to study more extreme tropical convection.