Hello,everyone.
Once I recorded 2 vanes as below
  Dwind=1 
  WindVector (1,Dwind,WD_10m,FP2,False,0,0,4)
  FieldNames("WD_10m_mean,WD_10m_Std")
  Maximum (1,WD_10m,FP2,False,False)
  Minimum (1,WD_10m,FP2,False,False)
  
  WindVector (1,Dwind,WD_80m,FP2,False,0,0,4)
  FieldNames("WD_80m_mean,WD_80m_Std")
  Maximum (1,WD_80m,FP2,False,False)
  Minimum (1,WD_80m,FP2,False,False)
Sometimes WD_10m_mean or WD_80m_mean stayed as a changeless value for a longtime but the WD_10m_Std or WD_80m_Std recorded "NAN" at the same time.
In my opinion,the "std dev wind dir" should be "0" when "vector mean wind dir" remains the same.
Any ideas?
Best wishes