Surface Wind and Humidity in the Eastern Tropical Pacific: Regimes and Variability as Observed by Saildrone Unmanned Surface Vehicles

The ocean and the atmosphere form a closely coupled system in which heat, momentum, and water are exchanged across the air-sea interface. These interactions have wide-ranging impacts on the large-scale and local patterns of climate and weather variability from one region of the globe to another. Hence, it is important to understand the state variables regulating air-sea fluxes, such as relative humidity, and how they vary across the globe. However, near-surface relative humidity is difficult to measure remotely and is not well understood. With limited in situ and surface-based observations over vast ocean regions (i.e., the remote tropics), this poses a problem for accurately resolving surface fluxes at the air-sea interface. Fortunately, recent advancements in autonomous technology and observing platforms aim to address these challenges.

Of these new and emerging technologies, Saildrone unmanned surface vehicles (USV) offer an autonomous ocean-going observing platform, capable of collecting large quantities of oceanic and atmospheric data at the air-sea interface in remote regions of the ocean. High resolution measurements from a recent 6-month mission to the eastern equatorial Pacific reveal new insight into the temporal and spatial scales of surface wind and humidity variability on sub-daily timescales. The results are investigated in the context of tropical convective events, and the implications for air-sea fluxes in the eastern Tropical Pacific are discussed.