Source/sensor: SeaWinds on QuikSCAT

Coverage: 19 July 1999-present, global

Abstract:
The SeaWinds on QuikSCAT scatterometer provides normalized radar cross section (sigma-0) measurements of the Earth's surface. Typically, products such as PO.DAAC products 108 and 109 convert the sigma-0s to wind measurements. However, scatterometers have also proven useful in a variety of land and ice studies. This product consists of browse images made directly from the sigma-0s to aid in the selection of regions and time periods for study.

For each day, this dataset has 1 sigma-0 browse image for each combination of

• 3 regions: global, north, and south
• 2 polarizations: horizontal and vertical
• 3 image types: average, standard deviation, and count

Regions: all global images (6 per day) are rectangular lat/lon grids covering the entire globe with a resolution of 5 pixels/deg, or about 22.5 km/pixel at the equator. They well suit mid-latitude regions but distort polar regions. The two sets of hemispheric products well suit the high-latitude regions. Those images are polar stereographic projections using a 70° reference latitude with a nominal grid size of about 22.5 km. The polar views include only measurements above a high latitude cutoff of 52°.

Polarizations: QuikSCAT measures the sigma-0s at both vertical and horizontal polarization. Since it is undesirable to combine measurements from different polarizations, measurements for each are kept separate.

Image Types: the average sigma-0s are temporal averages over a one-day period of all the sigma-0 measurements whose centers fall within each image pixel area. These are the most useful of the three image types. The standard deviation images are the normalized standard deviation of the measurements hitting each pixel divided by the mean value. The count images are the number of measurements.

Data Set Volume: There are 18 data files per day:

SIR Files			Size (in bytes)
region	image type	polarization	uncompressed	compressed
global	average sigma-0	horizontal	3240960	~2500000
		vertical	3240960	~2700000
	count	horizontal	3240960	~700000
		vertical	3240960	~800000
	standard deviation	horizontal	3240960	~1900000
		vertical	3240960	~2000000
north	average sigma-0	horizontal	302080	~200000
		vertical	302080	~200000
	count	horizontal	302080	~80000
		vertical	302080	~80000
	standard deviation	horizontal	302080	~150000
		vertical	302080	~150000
south	average sigma-0	horizontal	302080	~210000
		vertical	302080	~210000
	count	horizontal	302080	~80000
		vertical	302080	~80000
	standard deviation	horizontal	302080	~160000
		vertical	302080	~150000
total per day			23070720	~10800000

Smallest order: One average sigma-0 file via FTP.

Standard Product: FTP

Data Format: SIR

Media Format: These data are available via FTP to podaac.jpl.nasa.gov, on CD-R and on 8mm EXABYTE tape in LINUX TAR.