Estimating Convection’s Moisture Sensitivity Function Using DYNAMO Observations

We propose to examine the sensitivities of tropical convective activity to humidity and temperature profiles in the environment, based on new field observations from the DYNAMO experiment. The sensitivities can be succinctly described in the framework of a time-independent matrix, which we propose to estimate as a novel activity in this project. In order to advance these objectives, we propose two linked lines of activity:

1. Data processing of special field observations to produce profiles of moisture, radar echo statistics (cloud systems) and wind divergence (indicative of convective activity and heating profiles), as input to the estimation;

2. Estimation of the sensitivity matrix (or linear response function), based on these and other data (soundings, satellite), guided by first-guess estimates derivable from existing cloud-resolving model results, and subdivided into convecting regimes as appropriate.

Knowing the sensitivity matrix (or a few such matrices, for different ‘regimes’ of convection activity) is desirable for several reasons. First, it helps advance understanding of convection variations and their impacts, including the Madden-Julian Oscillation (MJO) and other climate variations. The sensitivity matrix quantitatively attributes a relative importance to temperature and moisture anomalies at different altitudes in explaining convection or rainfall anomalies. The matrix can also be compared directly to its counterpart in climate models, acting as an inclusive standard and guide for the development of better moist physics packages to improve climate simulation and prediction.
In this way, our work will support core capabilities of NOAA in understanding and modeling of the climate system, as well as in observing system design and use. Through its vertical integral, the convection sensitivity matrix allows prediction of rainfall based on thermodynamic input profiles, which may be a useful tool informing the societal challenges of better understanding and prognosis of Climate Impacts on Water Resources, Changes in Extremes of Weather and Climate, and better models that can provide Information for Mitigating and Adapting to Climate Change, NOAA’s long-term goal in its Next-Generation Strategic Plan.