Summary of Winds and Currents from Satellite Meeting April 19 and 20, 2018 Mark A. Bourassa1 Ernesto Rodriguez2 and Sarah Gille3 Center for Ocean-Atmospheric Prediction Studies and Department of Earth, Ocean and Atmospheric Science, Florida State University 2. JPL/Caltech 3. Scripps Institution of Oceanography

Designated Measurements Atmospheric Boundary Layer? GRACE Follow-on

Competed Concepts Winds and Currents Opportunities for 3 of 6 to be selected in coming decade Possibility that other concepts needing tech development could also be ready for competition by end of decade, so maybe 3 of 7 or 3 of 8. Competed between science objectives Community buy-in a must Needs to address a wide scope of science and applications

Questions to esas2017@nas.edu WACM opportunities Questions to esas2017@nas.edu http://sites.nationalacademies.org/DEPS/ESAS2017/index.htm

Goals of Meeting We must develop science topics (or topic) that sound exciting to more than oceanographers. We must develop the measurement requirements for these science topics. The orbit selection and instrument design can be refined later to be optimized for the research goals. A past point design (WaCM) for an Earth Ventures mission had roughly 5km spatial scales, 1600km swath width, 0.8 m/s uncertainty in winds, and 0.5 m/s uncertainty in currents This design had to meet specific budget and accommodation constraints and address a single science hypothesis Our new design can be optimized based on science goals Identify potential issues that will need to be addressed Communicate the benefits to the science and applications communities and decision makers Publications and outreach Produce a white paper eventually resulting in an refereed publication

Suggested Science Goals Broad theme of Improved Air-Sea Coupling Improving representation of the interface between the ocean and the atmosphere as well as the atmospheric and oceanographic boundary-layers Suggested Specific Topics Improved understanding of the tropical ocean circulation Improved seasonal to interseasonal forecasting Improved air-sea interaction associated with eddies and currents Links to ocean and weather forecasting Strong links to ocean biological Ocean-atmosphere-sea ice coupling Links to changes in Arctic and ocean circulation

Winds and Currents Applications The observations required for the science topics would greatly benefit ocean observing systems TPOS2020 and AtlantOS, among others The in situ observing system would help validate some of the science goals related to mixed layer variability and ocean circulation (tropical and Arctic There are many applications that help the business case Ship routing Weather forecasting Fisheries management Glacier and sea ice tracking Agriculture (based on longer-term forecasts) Forecasting of severe weather More….

Steps to Move Forward Get a better name that WaCM Pin down science objectives – and clearly articulate them Verify that there are not serious problems with rain and aliasing of inertial, tidal and diurnal cycles Optimize instrument characteristics with respect to the science goals The aircraft instrument works better than expected, so we have some trade space with the instrument design Develop modeling of the boundary-layers This would allow for better use of the winds and currents observations Improved surface physics, winds and currents would put much stronger constraints on entrainment at the top of the atmospheric boundary-layer Likely improving the assimilation of surface winds

General Concept Behind the Goal The ocean and atmosphere are relatively strongly coupled on scales below about 70km Far more so that seen in one-way coupled models The spatial derivatives of currents and directional wind (stress) show a strong signal. Coupled models will need to represent this coupling to properly describe the energy and water cycle, as well as ocean forcing Desired Outcome To characterize the coupling between current gradients and the curl of the wind (stress) as a function of spatial scale and current gradient. This will provide critical information for two-way coupled ocean-atmosphere models, the future of modeling. Graphic created by WHOI

Ocean’s Vertical Heat Flux Due to Submesoscale Variability Graphic from Ocean submesoscales as a key component of the global heat budget by Zhan Su, Jinbo Wang, Patrice Klein, Andrew F. Thompson & Dimitris Menemenlis

Upper-ocean heat content rate of change Upper-Ocean Heat Content Rate of Change - Modern Model vs data - Seas Around Antarctica Upper-ocean heat content rate of change Modern Model A smattering of other Argo and air-sea heat flux-related results 6.  Air-sea fluxes in the Southern Ocean explain the annual cycle in upper ocean heat content when you average over the entire Southern Ocean, but don't explain the local balances.  Net temperature change of the Southern Ocean is consistent with about 0.6 W/m^2 input over the last 50 years; net freshening consistent with increased precipitation or ice melt. Gille et al, in prep (Presentation at Ocean Sciences Meeting) Models (left) don’t match observations (right) Except when averaged over the whole Southern Ocean If regional energy budgets are wrong, heating will occur in the wrong areas and air-sea exchange will be non-sense Sarah Gille

Summary The curl of wind (stress) as a function of the gradient of surface current is a strong indicator of small scale (low end of mesoscale, <75 km) coupling between the ocean and atmosphere We can diagnose this coupling with WaCM Geophysical variables This coupling appears to be relatively important for the regional and global energy and water cycles, as well as ocean forcing We can greatly improve tropical coupling and identify the tropical general circulation Surface mMeridonal circulation can be observed with high confidence for the first time Ice motion couple with flow around ice and stress around ice can be observed. Many applications, including data assimilation.