Using Ocean Vector Wind Fields to Locate the ITCZ During SPURS-2

The Inter Tropical Convergence Zone (ITCZ) in the eastern central Pacific Ocean is marked by convergent winds in the lower atmosphere, precipitation and sea surface evaporation. The 2016-2017 Salinity Processes in the Upper Ocean Regional Study (SPURS-2) field campaign studies these processes in relation to the fate of freshwater in the eastern central Pacific Ocean. This study focuses on estimating the advection and convergence of atmospheric moisture through the region using 10-m ocean vector winds from a variety of satellite platforms. Representing atmospheric moisture convergence using a single 10-m level takes advantage of the ship-based and buoy-based (10N 125 W) observations from SPURS-2.

The location of the ITCZ is determined using ocean vector winds, sea surface salinity (SSS), precipitation (P), and evaporation (E) estimates for the region. Observation resources include satellite-based observations (wind, SSS, and P), models (wind, SSS, P, E), and in situ assets deployed during the SPURS-2 field campaign (wind, SSS, P, E). Observations from the in situ assets including upper air soundings, ships, and buoys are used to validate satellite and model data and to develop scaling requirements for estimating the advection and convergence of atmospheric moisture in the SPURS-2 region. The effective spatial and temporal resolution needed to determine the location and extent of the ITCZ is addressed. Issues and solutions for using satellite-only data to determine the location of the ITCZ are presented. The location of the ITCZ impacts several areas of interest for the SPURS-2 field campaign including precipitation, wind velocities, column integrated atmospheric moisture content, sea surface salinity, sea surface temperature, radiation budgets, and latent and sensible heat fluxes.