Latent Heat Release from Warm Rain over the Global Oceans and its Connection to the Large-Scale Environment

Latent heating transports energy from the surface to the atmosphere. The Tropical Rainfall Measurement Mission (TRMM) has provided measurements of latent heating in the tropics, but shallow warm rain was previously found to be underrepresented in TRMM products due to a lack of instrument sensitivity and the small-scale nature of cumulus clouds. We have generated the first global estimates of latent heating from oceanic warm rain by leveraging the high sensitivity of CloudSat to light precipitation.

The algorithm behind these estimates, called the Wisconsin Algorithm for Latent Heating and Rainfall using Satellites, or WALRUS, is a Bayesian Monte Carlo algorithm that compares observations of key integrated and structural characteristics of the reflectivity profile (such as echo top height and path integrated attenuation) to a database assembled from a suite of oceanic warm rain simulations generated using the Regional Atmospheric Modeling System. WALRUS output consists of not only vertically resolved latent heating profiles, but also surface warm rain intensities, total liquid water path, vertical velocity profiles, and several other cloud properties.

Using four years of data from CloudSat, we analyze the global distribution of latent heating from warm rain and place this in the perspective of the global energy budget. The response of warm rain process rates to changing environmental conditions will be assessed by contrasting different ocean basins and compositing WALRUS latent heating estimates with several environmental variables including estimated inversion strength, free tropospheric humidity, and zonal winds. The results provide insights into the effects of the large-scale environment on the nature of diabatic heating occurring in warm rain systems.