VITAL II: Enhancing regional atmospheric boundary layer observations through the synergy of novel state-of-the-art sensors

Spatially and temporally continuous observations of atmospheric boundary layer (ABL) dynamics and thermodynamics are key for many areas of atmospheric research. State-of-the-art observational approaches are either limited by vertical resolution (satellites), spatial coverage (ground-based profilers) or spatial and temporal coverage (radiosondes). The VITAL II campaign (Vertical Profiling of the Troposphere: Innovation, Optimization and Application) as part of HErZ (Hans Ertel Center for Weather Research), a cooperation on fundamental weather and climate research between the German Meteorological Service (DWD) and German universities, addresses this observational gap.

VITAL II will take place from June 1 – August 31, 2026 in the Cologne Bay region between the west German cities of Cologne, Bonn and Aachen employing and installing seven profiling sites over a wide variety of land surface types. At the profiling sites, ground-based remote sensing systems such as water vapor lidar, Doppler lidar and microwave radiometers will be operated which yield high potential to reliably profile ABL temperature, humidity, winds and turbulence in a nearly continuous manner. Uncrewed aircraft systems (UAS) will additionally be operated at selected sites during an intensive observation period, complemented by a large number of radiosonde ascents.

During VITAL II, first data from the Meteosat Third Generation Sounder (MTG-S1) satellite instrument IRS (Infrared Sounder) will be employed for providing continuous 3D observations of temperature and humidity with a temporal resolution of ~30 min. However, IRS deficits will remain in observing the ABL, especially in cloudy conditions. VITAL II will leverage the use of these novel, hyperspectral IRS observations by combining them with the VITAL II surface-based in-situ and remote sensing observations. Novel machine learning algorithms which synthesize MTG-S1 data with surface-based observations will be applied to and assessed by the multitude of additional VITAL II profiling observations. The objective is to significantly enhance the observed information content in the ABL. Next to the extensive profiling, VITAL II will install a dense near-surface observation network on the meso-beta-scale (20–200km = regional scale). Up to 50 surface stations of the updated autonomous cold pool logger (APOLLO 2.0) will be installed within Cologne Bay.

Altogether, the observational setup will be used for enhancing the understanding of the evolution of the stable and convective ABL over an urban – rural transition zone, as well as on convective cold pools. For the latter, the main focus is on merging dense spatial, near surface data with vertical temperature and humidity patterns. The profiling observations will be used for data assimilation studies with the DWD numerical weather prediction model ICON and for evaluating and improving ICON land surface and ABL turbulence parameterization schemes.

This contribution will present in detail the VITAL II concept and first measurements highlighting the importance of sensor synergy for ABL coverage.