Wind Data and Scatterometry

Data Access

NSCAT, ERS-1 and ERS-2 uniform grids of North and East wind velocity, North and East wind stress or pseudostress, wind divergence and curl of stress or pseudostress are available.

NSCAT data are available as ESIP grids and CERSAT grids.
ERS-1 and 2 data are from CERSAT grids.

The data can be accessed as:

• User selectable subsets , using our GUI with image and/or ASCII output.
• GIF images of global fields of wind velocity, wind divergence, and the curl of pseudo-stress.
• Binary data and read software for those wishing to write their own subsetting/plotting program.

QuikSCAT data will be available at this site in early 2001.

Importance of Wind Monitoring
      Wind is driven by the differential heating of the atmosphere; it advects water and latent heat, drives ocean currents and thus redistributes the heat the ocean stores.  By redistributing heat in both ocean and atmosphere, wind plays a key role in giving Earth moderate climates. 
       The wind stress at the surface measures the momentum exchange that couples the ocean with the atmosphere. In regions where the horizontal divergence of the wind field is significant, there is upwelling or downwelling of air, and the heat and moisture it carries. The curl of the wind stress is a measure of the angular momentum imparted to the ocean by the atmosphere, and is the central quantity in quasi-geostrophic analyses of ocean circulation. The importance of these derived fields is the reason we wish to estimate them simultaneously. 

Development of Scatterometry
       Only spaceborne sensors can measure winds globally and rapidly.  Scatterometers emit short pulses at microwave frequencies and observe the scatter in the return signal caused by capillary waves (of about 2 cm in length) on the ocean surface due to wind friction.  These instruments can penetrate cloud covers and take measure under all-weather conditions.  The NASA Scatterometer (NSCAT), launched in August 1996 on the ADEOS-1 spacecraft, covers 95% of the ice-free oceans once every 2 days. The ERS-2 scatterometer covers most of the globe about once in 4 days. 
      With NSCAT's operational data starting in September 1996 we have for the first time the chance to observe twice daily the global wind field.  Although the the ADEOS-1 satellite carrying NSCAT failed in June 1997, a follow-up mission QuikSCAT launched in mid-1999 to continue where NSCAT left off.  A subsequent mission ADEOS-II/SeaWinds is scheduled for launch in 2001.  The figure below shows the history and future of scatterometry missions (click for a larger image).

Scatterometer Spacecrafts: 1990's and Beyond

ESIP Scatterometry Objectives
        The objective is to create gridded maps, once per day, at 1 degree spatial resolution, between +/-75 degrees latitude, at all longitudes, of the horizontal near surface wind (at 10 m) and wind stress, as well as the divergence and curl of these fields. The maps will cover the period from September 1996 through June 1997 (after which the satellite failed). We will soon generate wind products based on QuikSCAT scatterometry, currently undergoing calibration/validation.
     The work described here is an extension of work recently funded under a separate NOAA/NASA opportunity to evaluate both the stress computation and the interpolation algorithms, and make a useful gridded stress field from NSCAT.  Here we will also compute the dynamically useful divergence and curl fields.