Ocean Surface Winds - NHC Forcast Area

Ocean Surface Winds -- SSMI and AMI Microwave Sensors

SSMI

The SSMI derived ocean surface winds are calculated at a height of 19.5m for the previous days ascending and descending satellite passes. The wind speed algorithm used was developed by Goodberlet et al., and expresses the wind speed, WS, in meters/second as

WS=147.90+1.0969*TB16v-0.4555*TB22v-1.7600*TB37v+0.7860*TB37h

where, TB is the radiometric brightness temperature at the frequencies and polarizations indicated. All data where TB37v-TB37hr < 50 or TB19h > 165 was rain flagged (Rain Flag 0) yielding wind speeds with an accuracy of 2m/s.

ERS-1 (AMI)

The ERS-1(AMI) derived ocean surface winds are calculated at a height of 10m for the previous days satellite passes as provided by ESA in their fast delivery product data. The current empirically derived model function being used by ESA to relate normalized radar cross-section with wind speed and direction is referred to as CMOD4.

This data is considered to be of research quality, and the presented wind speed quantities should not be considered absolute. In storms with high wind gradients, the wind speed values will be underestimated. For the SSMI data, the presence of liquid water not detected with rain flag 0 will tend to add a positive bias in the estimated wind speeds.