Ship-based Measurements of Atmospheric Cold Pools and Mass Flux Transport in the Indian Ocean from the DYNAMO Field Program

One of the goals of the Dynamics of the Madden Julian Oscillation (DYNAMO) field program is to understand the role of pre-moistening of the upper troposphere prior to MJO initiation. It is hypothesized that cold pools are integral to shallow-to-deep convection transition. To understand the structure and organization of cold pools, data gathered during leg 2 and 3 of the DYNAMO experiment will be studied. Lidar data will be used to track the leading edge velocity, depth and aerosol enhancement of cold pools as they pass over the ship. This information will be combined with in-situ measurements of thermodynamic variables to form a statistical database of the over 200 cold pools that passed over the ship.

A related component of this analysis is to understand the mechanism driving pre-moistening. In order to do this, the data from the High Resolution Doppler Lidar (HRDL) and the W-band radar will be used to study the updraft/downdraft structure and mass flux transport in the context of shallow convection cases. Time series of turbulence profiles from the HRDL will be combined with those from the W-band radar to allow the study of the updraft/downdraft structure from clear air to well within the cloud layer. In addition variables important for convective mass flux parameterization in models, such as updraft fractional coverage (σ) and convective mass flux velocity (M*) are computed. This direct measurement of σ and M* will allow evaluation of cumulus mass flux parameterizations used to model vertical transport of water vapor.