Remote Sensing of Ocean Surface Winds

Dear Colleagues,

Ocean surface winds are one of the key components of the Earth system. They are a major driver of the circulation of both the ocean and the atmosphere. Accurate knowledge of winds, related wind stress, and wind-driven ocean currents is necessary to understand and quantify air-sea fluxes of heat and nutrients. Heat fluxes and their relationship to global sea surface temperature, temperatures at depth, and ocean heat content are necessary to understand and predict global climate change and its effect on the global ocean. Knowledge of nutrient fluxes, on the other hand, is important for sustaining global fisheries and developing an understanding of the effect of climate change on marine life.

Ocean surface winds affect air–sea interactions, fueling weather systems by modulating sensible and latent heat fluxes. They reveal the regions where the converging near-surface air provides favorable dynamical conditions for the development of convection and precipitation. Understanding these interactions is critical for improving weather forecasting on a variety of spatial and temporal scales—from the isolated convective cores, to the organized mesoscale systems, to hurricanes, to seasonal and intraseasonal phenomena such as MJO, El Nino and trends and variability in large-scale atmospheric circulation (e.g. monsoon rains).  Indeed, ocean surface winds and stress are essential climate variables (ECV), as identified by the Global Climate Observing System (GCOS) (GCOS-200, 2016).

In addition to its scientific necessity, accurate ocean vector wind climatology is also a requirement for developing offshore wind power generation facilities as a method to reduce worldwide dependence on fossil fuels and ameliorate ongoing global climate change. Ocean surface winds vary on several important timescales, including diurnal variation (e.g. on-shore and off-shore oscillations in coastal winds), seasonal variation, and longer term variation which correlates with long-term ocean current and sea surface temperature periodicity, including the well-known El Nino Southern Oscillation. Because of diurnal variation, it is important to obtain global ocean surface vector winds multiple times a day, to avoid aliasing the diurnal signature into longer term climatology. In order to achieve sufficiently frequent global coverage, it is necessary to employ space borne remote sensors.

Two primary remote sensors have been utilized to measure ocean surface winds; microwave radiometers (e.g. GMI, AMSR, SSM/I, SMAP) which typically measure wind speed only, and scatterometers (e.g. QuikSCAT, ASCAT), which measure speed and direction in order to obtain full vector wind fields. Full wind vectors can also be obtained from polarimetric microwave radiometers, such as WindSAT, with significant degradation in directional performance for low wind speeds. High resolution wind fields with regional, rather than global, coverage have also been obtained using a synthetic aperture radar. Wind in tropical cyclones is measured by some of these instruments, and these measurements are very valuable for forecasting intensity and size of storms.

In this Special Issue, we plan to bring together papers describing how to improve global ocean vector wind measurements in terms of accuracy, resolution, and frequency of sampling, as well as application papers describing advances in the scientific use of remotely sensed ocean vector winds.

We invite papers on the following related topics.

1. New remote sensor technology for the improved measuring of ocean surface winds in terms of spatial extent (e.g. closer to the coast), frequency of global coverage, measurement resolution, or any other improvement that will significantly impact the scientific utility of the measurement.
2. Methods for improving the accuracy of ocean surface winds from current or historical sensor data, including, but not limited to, fusion with other sensors, improved quality control, improved accuracy, or increases in the extent of the data record.
3. Methods for cross calibrating or harmonizing winds, measured from different sensors in order to produce more consistent and more accurate climate data records, over longer periods of time and with more frequent global coverage.
4. Methods for simultaneously retrieving ocean surface winds and other related geophysical parameters of interest (e.g. ocean currents, salinity, sea surface temperature, precipitation), where combining wind with the other parameter greatly enhances the scientific utility of both.

Novel scientific or technological uses of remotely sensed ocean surface winds, including, but not limited to: the estimation of air–sea heat, momentum, and nutrient fluxes; the detection of changes in intraseasonal to decadal climate modes (i.e. Wind Bursts, MJO, ENSO, PDO, …); the evaluation and improvement of models of ocean or atmosphere dynamics through data assimilation or process studies;  understanding hurricane genesis and evolution; the detection of trends in large-scale atmospheric circulation, as depicted by its lower-level branch; understanding the role of surface winds in regulating the geographical distribution of precipitation; and using ocean surface wind climatology to optimize power generation from offshore facilities.

Dr. Bryan Stiles
Dr. Svetla Hristova-Veleva
Dr. Lucrezia Ricciardulli
Dr. Larry O’Neill
Dr. Zorana Jelenak
Dr. Joe Sapp
Guest Editors

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