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Name: John
Status: other
Grade: N/A
Location: WY
Country: N/A
Date: 11/29/2005


Question:
Given :

Wind speed and wind direction for different heights like 3000m , 4000m , 5000m etc ...for a definite time and definite date for the past ten years (The data are accurate and taken from a radiosonde reports ) . example :

    Date     Height    wind/Dir    Wind/Speed
2/11/2005   5000m      240deg     23.4 m/sec
2/11/2005   5000m      286deg      9.2 m/sec
2/11/2005   5000m      291deg     23.7 m/sec
2/11/2005   5000m      277deg     11.11m/sec

Question :

1.Can we make an average for the direction of the wind for this height in this date and time ?

2.Can we make an average for the speed of the wind for this height in this date and time ?

In another way :
Is there any meteorological formula for calculating wind direction and speed in upper air?


Replies:
You are on some rather thin statistical ice. The data provide an instantaneous (altitude,direction,speed). However, one has to be careful about "averages" because these three variables are not independent of one another. While "altitude" I'd assume you mean the distance from the earth's surface perpendicular to the surface. But that is going to change from place to place. Also, because of turbulence, either from temperature differences or terrain, "direction" and "speed" may each be vector quantities. So it is difficult to know just what one is averaging. Also the data do not include a time variable. That is, the wind may blow in one direction/speed for a certain time period and another direction/speed for a certain different time period even at the same place. So somehow a time weighting factor would have to be folded into the averaging. It is a real tough problem.

Vince Calder


John,

Climatologically speaking, one could determine such an average for both wind direction and speed for a single date, time, and height for a ten year period, but it may not mean as much as, say, average surface temperature or precipitation.

Upper level winds are constantly changing and have a periodicity that can vary tremendously from one latitude and longitude to another, as well as seasonally.

Determining wind speed and direction is operationally done using radiosondes, as you know, as well as radar, sodar, or lidar profilers that make remote measurements from the ground. Furthermore, the complicated upper atmospheric computer models used by the National Weather Service and other country's weather services have become quite good at predicting the upper level wind speeds and directions. There is no simple formula or easy way to make these calculations/predictions; measurements and/or computer models are required.

David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory


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