Detecting cold pools from soundings during EUREC4A

TL;DR

This study introduces a new method to detect atmospheric cold pools from soundings during the EUREC4A campaign, revealing their characteristics and behavior in tropical oceanic environments.

Contribution

The paper presents a simple, effective criterion based on mixed-layer height to identify cold pools from atmospheric soundings, validated with simulations and observational data.

Findings

Cold pools identified in 7% of soundings during EUREC4A.

Cold pools coincide with mesoscale cloud arcs and surface temperature drops.

Downshear spreading of cold pools suggests downward momentum transport.

Abstract

This paper develops a novel method to detect cold pools from atmospheric soundings over tropical oceans and applies it to sounding data from the EUREC4A field campaign, which took place south and east of Barbados in January-February 2020. The proposed method exploits the fact that the air in a cold pool is denser than the air above it. It leads us to define cold pool soundings as those for which the mixed-layer height is smaller than 400 m. We first test this criterion by verifying its consistency with surface temperature and precipitation in a realistic high-resolution simulation over the western tropical Atlantic. Applying it to EUREC4A data, we then identify 7% of EUREC4A dropsondes and radiosondes as cold pool soundings. In two selected case studies, we find that cold pools soundings coincide with mesoscale cloud arcs and temperature drops in the surface time series. Statistics for the entire campaign further characterize the signature of cold pools in temperature, humidity and wind profiles. In the presence of wind shear, we show in particular that the spreading of cold pools is favored downshear, suggesting downward momentum transport by unsaturated downdrafts. These results support the robustness of our simple method in different environmental conditions and illustrate the new insights it offers for the characterization of cold pools and their environment.