Variations in Radiative Heating and Moisture Profiles During AMIE
Authors
Courtney Schumacher — Texas A&M University
Fiaz Ahmed — University of California, Los Angeles
Category
MJO: Madden-Julian Oscillation
Description
Vertical profiles of Q1, Q2, Qr and MSE from the AMIE campaign on Gan Island in 2011-2012. The time runs from 10/02/2011 to 12/31/2011. Note that the radiative heating profiles are only available for dates after 10/10/2011.
The step-wise progression of moisture that precedes each MJO event is seen in the MSE profiles.
One school of thought suggests that the Madden-Julian Oscillation (MJO) is regulated primarily by radiative and surface fluxes via the column moist static energy (MSE). Keeping this in mind, we examine the vertical profiles of radiative heating and MSE over the equatorial Indian Ocean from observations during the AMIE/DYNAMO/CINDY2011 campaign. Cloud radiative heating from the KAZR on Gan Island is generally positive in the column and aids the convective heating. However, when the MJO convective envelope is decaying, there is a top-heavy cloud radiative heat source relative to the surroundings. We examine the role of this heat source in the context the MJO life cycle. Particularly we ask: does the top-heavy radiative heating destabilize the environment, paving the way for the next phase of the MJO? Or does it reduce CAPE in the environment by creating a stable layer, thus contributing to a lengthy inactive phase? Does the primacy of one process over the other control the time scale between two initiation events?
Preliminary analysis of MSE profiles from the AMIE variational analysis shows that the mid-tropospheric minimum in MSE is prominent during the inactive phase. During the MJO active phase however, the mid-tropospheric minimum is wiped out by presumably a combination of radiative and convective fluxes to nudge the moisture profile towards the moist adiabat. The MSE profiles displays two preferred heights for mid-tropospheric dryness. A mode initially present near 700 mb migrates upward to 550 mb, close to the climatological melting layer, with the advent of shallow convective clouds. We also take a closer look at the factors that control the vertical profile of MSE.
