Wind observations from hot-air balloons and the application in an NWP model

We report on a wind observation method based on the movement of hot-air balloons (HABs). A quality assessment was carried out by comparing against wind observations at the meteorological tower of Cabauw in the Netherlands during May–September 2018, and the obtained standard deviations in error were σu=0.65 m/s and σv=0.69m/s  for the measured zonal and meridional wind components, respectively. Subsequent comparison against short-term forecasts of the HARMONIE-AROME model showed a standard deviation of 2.5 ms−1 for the wind vector difference. From the HAB observation set, a case was selected with a rapidly changing wind field belonging to a small intensifying depression. The HAB wind observation was applied in data assimilation as a proof of principle for a single-observation experiment. It is shown that in a complex baroclinic situation, the model state is slightly improved.