Wind speed from SSMI satellite

Plots of the 10 m wind speed from the SSMI satellite are in the following two tables.  The data is courtesy of Joseph V. Ardizzone at the NASA Goddard Space Flight Center. Tbe red numbers are 10 m buoy speeds at the satellite pass time.  The vectors are aircraft winds adjusted to 10 m from flights at 30 m altitude. The aircraft flight time is given in the upper right. Local times are shown, not GMT.

From satellite passes which were close in time to the flights (morning passes on 06/17, 06/19, 06/21, 07/01 and evening passes on 06/18, 06/22, 06/27, 06/30), it seems the satellite winds are 3-5 m/s slower than the aircraft winds.  The maxima (expansion fans?) in the lee of Capes Blanco, Mendocino and Point Sur are seen on almost every high-speed day.    Wind maxima over 100 km offshore were news to me (6/23 and 6/29 morning passes; 6/02, 6/26, and 6/29 evening passes).  They can't be confirmed by the aircraft data, but seem to have influenced the June 1996 mean.

  • Averaged wind fields for June, July, and June-July 1996 are averaged of all satllite overpasses of the region within the averaging time.  Some overpasses only viewed part of the region, but their data was used in the average.
  • To look for diurnal effects, the daytime (7 am - 7 pm) and nighttime (7 pm - 7 am) average June data can be compared.   They appear similar.
  • For comparison, a  long-term June wind stress climatology (Nelson, 1997) is shown for comparison to the June 1996 stress from SSM/I winds.  The stress was estimated from the SSM/I winds with a bulk formula and the Large and Pond (1981) drag coefficient.  The  stress maxima are 1/2 as low as in the Nelson climatology.
    • Information on how the data is obtained and dataset descriptions can be found at the ssmi web site. All speeds in gridpoints with active rainfall, or one gridpoint away, were discarded on the suggestion of Joseph V. Ardizzone.

    Morning passes:

    Point Conception Point Sur Cape Mendocino Cape Blanco
    June 19 June 02 June 07 July 01
    June 23 June 11 June 12
    June 29 June 17 June 26
    June 21

    Evening passes:

    These passes were closer in time to the aircraft flights.
    Point Conception Point Sur Cape Mendocino Cape Blanco
    June 19 June 02 June 07 July 01
    June 23 June 11 June 12
    June 29 June 17 June 26
    June 21