We can measure soil moisture with weather balloons!
Back in March, another CLASS4GL paper was published by Denissen et al. (2021) in the Nature partner journal Climate and Atmospheric Sciences. In this research, sensible heat and humidity input from the surface to the atmospheric boundary layer was estimated from weather balloon observations using the CLASS4GL framework. The atmospheric boundary layer model was initialized with morning temperature and specific humidity observations from balloon soundings. Afterwards, the model simulations were matched to the respective afternoon soundings by scaling the soil moisture and consequently the surface heat flux partitioning between sensible heat and humidity. As a result, the coupling between soil moisture and the atmospheric boundary layer is achieved on a much larger scale than state-of-the-art observational products, such as FLUXNET/AMERIFLUX.
The estimated fluxes are then used to distinguish water-limited (evaporation is controlled by available soil moisture) from energy-limited (evaporation controlled by available surface energy) sounding days. We find significantly different behavior of the atmospheric boundary layer between these two regimes, associating dry conditions with on average warmer (+3K), higher (+400m) and drier (+1kPa) afternoon atmospheric boundary layers than wet conditions.
This work is a result of a collaboration between the Meteorology and Air Quality Group and the Hydrology and Quantitative Water Management Group at Wageningen University, the Hydro-Climate Extremes Lab at Ghent University and the Hydrosphere-Biosphere-Climate Interactions Group at the Max Planck Institute for Biogeochemistry.
All the details can be found in the original reference: Denissen, J.M.C., Orth, R., Wouters, H. et al. Soil moisture signature in global weather balloon soundings. npj Clim Atmos Sci4, 13 (2021). https://doi.org/10.1038/s41612-021-00167-w
Other recent CLASS4GL activities:
- A revision of the study on the effect of soil dryness on human heat stress conducted by Hendrik Wouters (Ghent University; Flemish Institute for Technological Research) is under review.
- Douwe De Vestele (Ghent Universtiy) investigates in his master thesis the role of land surface and soil moisture in flash drought termination.
- João Geirinhas (University of Lisbon) has been analyzing the drivers of recent severe heatwaves in Brasil, including the effect of drought conditions. His work was submitted recently for peer-review.