The potential temperature is useful in checking and characterizing super-adiabatic lapse rates. It is defined as a reference temperature obtained by changing an air parcel's temperature adiabatically to a pressure of 1000hPa. D.6 Wind Variables . The calculation of wind from the position of the balloon shall be made using earth spherical coordinates. D.6.1 Wind Speed and Direction .
Meteorological convention specifies wind direction as that FROM which the wind blows.
In meteorological usage the Cartesian velocity component values are calculated from the wind speed and direction. Wind speed can be determined from position components by D.6.2 Wind Shear . D.6.1 is used to convert to direction and speed. D.7 Location of the Balloon . Earth spherical geometry shall be used for the location of the balloon relative to the launch site.