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wind_direction

Calculate meteorological wind direction from zonal and meridional wind components.

Available in version 6.1.0 and later.

Prototype

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"

	function wind_direction (
		u    : numeric,  ; float, double, integer only
		v    : numeric,  
		opt  : integer   
	)

	return_val [dimsizes(u)] :  float or double

Arguments

u

A variable of any dimensionality containing the zonal wind component. Array size and shape must match v.

v

A variable of any dimensionality containing the meridional wind component. Array size and shape must match u.

opt

A scalar which indicates how 'calm' (u=v=0) wind direction is returned. Currently, the only option is:

  1. opt=0: the returned wind direction will be 0.0

Return value

A multi-dimensional array of the same sizes as u. The output will be double if u or v is of type double. Otherwise, type float will be returned.

Description

Calculates meteorological wind direction using the zonal and meridional wind components.

See Also

atan2, wind_component, wind_speed, wind_stats

Examples

Example 1 

   u    = (/ 10,   0,   0, -10,  10,  10, -10, -10, 0/)
   v    = (/  0,  10, -10,   0,  10, -10,  10, -10, 0/)

   wspd = wind_speed(u,v)
   wdir = wind_direction(u,v,0)
   print(sprintf("%7.2f", u)+sprintf("%7.2f", v)+sprintf("%7.2f", wspd)+sprintf("%7.2f", wdir))

The edited output is: 


            u      v     spd    dir
(0)	  10.00   0.00  10.00 270.00
(1)	   0.00  10.00  10.00 180.00
(2)	   0.00 -10.00  10.00   0.00
(3)	 -10.00   0.00  10.00  90.00
(4)	  10.00  10.00  14.14 225.00
(5)	  10.00 -10.00  14.14 315.00
(6)	 -10.00  10.00  14.14 135.00
(7)	 -10.00 -10.00  14.14  45.00
(8)	   0.00   0.00   0.00   0.00