Cold Pool Metrics based on High-Resolution Saildrone and Moored Buoy Observations over the Tropical Pacific

Abstract:

Atmospheric cold pools are an important source of variability in heat and moisture exchange over the tropical ocean. Given the smaller spatial and temporal scales of cold pools and their parent convection, in-situ observations of this phenomenon have been limited to shipboard and moored buoy measurements over the tropical Pacific. Saildrone unmanned surface vehicles (USV) offer an autonomous ocean-going observing platform capable of providing sustained, long-term observations over remote regions of the ocean. As part of a recent Tropical Pacific Observing System (TPOS) 2020 pilot study, high-resolution observational data collected during three 6-month Saildrone missions to the central/eastern tropical Pacific are analyzed to investigate wind and moisture variability associated with atmospheric cold pools. The analysis focuses on state variables, such as temperature and humidity, and how these variables regulate air-sea fluxes on high frequency timescales. Preliminary results based on high-resolution Saildrone data reveal rapid variations in air temperature during cold pool passages, as well as significant differences between 1-minute wind speeds and wind gusts behind the leading edge of the cold pool. The characteristics of cold pools identified from the Saildrone data will be compared to those derived from shipboard measurements in previous studies. The cold pool analysis will also be expanded to high-resolution timeseries obtained from the Tropical Atmosphere Ocean (TAO) moored buoy array. The results of this research will be discussed in context of understanding the effect of small-scale processes on large-scale ocean-atmosphere coupling and refining bulk algorithms for heat and momentum fluxes at the air-sea interface, as well as the broader implementation of Saildrone technology under the TPOS-2020 project.