South Red Sea Wind Maps
 by Robert Van Buskirk, Karina Garbesi, & Karen Rosen
 
Wind Map Links: 

  Wind Speed: 
    Annual Map (Scatterometry) 
    Annual Map (new COADS) 
    Annual Map (old COADS) 
    Monthly Maps:
     (COADS):  (Scatterometry):
       January January
       February February
       March March
       April April
       May May
       June June
       July  July
       August  August
       September September
       October October
       November November
       December December

    Seasonal Maps: 
      Oct - April 
         00:00-06:00 hrs 
         06:00-12:00 hrs 
         12:00-18:00 hrs 
         18:00-24:00 hrs 
      May - Sept 
         00:00-06:00 hrs 
         06:00-12:00 hrs 
         12:00-18:00 hrs 
         18:00-24:00 hrs 

  Wind Direction: 
   Seasonal Maps: 
      Oct - April 
         00:00-06:00 hrs 
         06:00-12:00 hrs 
         12:00-18:00 hrs 
         18:00-24:00 hrs 
      May - Sept 
         00:00-06:00 hrs 
         06:00-12:00 hrs 
         12:00-18:00 hrs 
         18:00-24:00 hrs 

  Old Map Index  

Home 
 

 Mean Monthly Wind Speed Maps are made available for the South Red Sea at this site.  These maps are derived from two sources. The primary source is ship observations collected in the Comprehensive Ocean-Atmosphere Data Set (COADS) available from the  National Center for Atmospheric Research (NCAR).  The data is extrapolated to all locations within the South Red Sea through use of a variable-distance-scale gaussian-weighted averaging technique.  The second source is satellite scatterometry data from the TOPEX and ERS satellites available from Colorado Center for Astrodynamics Research at: http://www-ccar.colorado.edu/~realtime/global_data_winds/wind.html
 
Wind Speed Data is useful for both energy resource and meteorological analyses.  Wind energy may be the cheapest source of indigenous utility-scale electricty for Eritrea. A key issue for wind energy development is where it is best to locate the wind energy plants. Maps such as these assist in the geographic analysis of wind energy resources. 
 
Multiple data sets are used because different data have different types of errors. The COADS data has low resolution outside of regular shipping lanes, so it does not characterize the East-West variation of the wind speeds well. Meanwhile the scatterometry data is calibrated with wave heights over open oceans, and it therefore underestimates winds in shallow or closes waters, or near land. The Scatterometry estimates are therefore about 1 m/s to 2 m/s lower than the COADS estimates, but they show the jet-like structure of the winds through Bab-al-Mandab better than the COADS data.

Wind speed data will be a key input for a national Eritrean meteorological model. In Eritrea, meteorological modeling is needed to extrapolate sparse ground measurements (of humidity, wind, rainfall, etc.) in order to provide complete geographic coverage.  Such meteorological models will calculate the air motions in the lower 3-4 kilometers of the Eritrean atmosphere.  Wind patterns over the Red Sea will be an essential input for calibrating and testing these models. 

Mean annual wind speeds in the South Red Sea from COADS data: 


Mean annual wind speeds in the South Red Sea from Scatterometry data:
(Red = 2 m/s, Yellow = 4 m/s, Green = 6 m/s)
 

These maps were produced utilizing a binned, adaptive length scale, gaussian-weighted averaging of data from 1971-1993 of the Comprehensive Ocean-Atmosphere Data Set (COADS) or using the same method for the 1997-1999 Scatterometry data. More specifically, data from the data sets were binned into different temporal periods (usually four or six periods of the day for each seasonal or monthly map). A map was produced for each temporal bin, and the maps produced from the binned data were averaged to produce the monthly  map. The data was binned this way in order to  take out biases from uneven temporal sampling in the data. 

To calculate averages, for each point on the map, two quantities are calculated: a gaussian weighted sum of values (wind speed in this case)  and a sum of gaussian weights.  The equation for the gaussian-weighted wind sum is as follows: 

WIND-SUM = SUM OF (WS*EXP(-(R2/R02))) 

where WS is the wind speed, R is the distance between the data point and the point of interest, and R0 is the averaging distance (or length scale). The second quantity is the sum of the weights: 

WEIGHT-SUM = SUM OF (EXP(-(R2/R02))) 

For the COADS data, the two quantities are calculated for progressivly larger R0 starting from R0= 10 kilometers to R0 = 150 kilomters. When the weight-sum is equal to a predetermined value (either 30, 40 or 50 depending on the degree of averaging desired), it is considered that there is enough data to calculate an average.  The average is calculated as the ratio of the wind-sum and weight-sum for that location. 

For the Scatterometry data a fixed R0 of 0.4 degrees was used.

For the wind direction, maps were first produced for the east-west and north-south velocities, and the direction of the resulting vector wind was taken as the mean wind direction. 
 
 
Last update 18 February 1999 by rvb