Identifying and Characterizing Tropical Oceanic Mesoscale Cold Pools using Spaceborne Scatterometer Winds

Convective cold pools over oceans contribute to the air-sea exchange of heat and moisture. Beyond cold pools' physical properties, cold pools and their intersections are important mechanisms controlling the life cycle of tropical convective systems. However, few observational techniques are available to routinely observe the properties of cold pools and their association with convection. The primary goal of this study is to demonstrate a new technique using gradients in remotely sensed ocean vector winds as a proxy for the structure and characteristics of tropical oceanic cold pools. Using Advanced Scatterometer (ASCAT) vector wind retrievals with field of view of 12.5 km, regions of enhanced gradients in surface winds are identified as gradient features. A 3-km Weather Research and Forecasting (WRF) model simulation was carried out to illustrate the technique over the Indian Ocean during the 2011 DYNAmics of Madden-Julian Oscillation (DYNAMO) field campaign. A forward operator was applied to the model wind fields, allowing direct comparisons of wind gradients and virtual temperature-defined cold pool thermodynamic and kinematic properties. In situ buoy measurements of air temperature were also used to validate ASCAT-identified cold pools. Quantitative skill metrics demonstrate that the technique has a low false alarm rate (<10%), high critical success index (>85%), and a low bias (~1). The gradient feature technique was then applied to ASCAT-retrieved ocean vector winds, revealing global variations in cold pool properties. These properties are shown to be related to the properties of global convective systems observed by the Tropical Rainfall Measurement Mission (TRMM).