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

In this paper, 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 ${\sigma }_u=0.65{\mathrm{ms}}^{-1}$ and ${\sigma }_v=0.69{\mathrm{ms}}^{-1}$ 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.