PRO wdirmean, u,ud,umean,udmean
; u ---input array for wind velocity
; ud---input array for wind direction (degree)
; umean--output mean wind velocity
; udmean--output mean wind direction

badval=-999.
pi=3.1415926

umean=badval
udmean=badval

uu=u*0.0+badval
vv=uu

r=where(u NE badval AND ud NE badval,c)

IF c GE 1 THEN BEGIN

  uu(r)=u(r)*cos((270.0-ud(r))*pi/180.0)
  vv(r)=u(r)*sin((270.0-ud(r))*pi/180.0)

  uumean=mean(uu(r))
  vvmean=mean(vv(r))

  x=uumean^2+vvmean^2

 


  umean=sqrt(x)


 
  IF(x NE 0.0) THEN BEGIN
  
  udmean=asin(vvmean / umean );(rad)

; Put horizontal rotation into the correction quadrant.
if ((uumean lt 0.) and (vvmean lt 0.)) then udmean=-pi-udmean
if ((uumean lt 0.) and (vvmean gt 0.)) then udmean=pi-udmean

 

  udmean=udmean*180.0/pi

 udmean=270.0-udmean; convert to wind direction coordinate

  IF udmean GE 360.0 THEN udmean=udmean-360
  IF udmean LT 0.0 THEN udmean=360+udmean

  ENDIF

ENDIF

  umean=meanbadval(u)

return
end