Humidity profile retrieval with the Clermont-Ferrand VHF wind profiler

The humidity profile can be derived from ST radars echo power and spectral width, provided the temperature profile, and one at least one humidity reference (either integrated or at a given altitude within the radar altitude range), are known. This technique has already been successfully implemented on VHF (MU, Japan, Gadanki, India) and UHF radars (Payerne, Switzerland). To this purpose, several algorithms have been developed, based on works by Tsuda (2001), and Gossard and Stankov (2003).

In this project, we will use the particular topography of the Puy-de-Dôme Observatory to our advantage. The Laboratoire de Météorologie Physique (LaMP) Clermont-Ferrand VHF profiler is located a few kilometers from the Puy de Dôme, which culminates at an altitude close to the first range gate of the radar (1464 m). At its summit, continuous measurements are performed with a humidity sensor and a GPS station, which provides the integrated water vapor (IWV).

Hence, we will be able to test the different humidity profile retrieval approaches, and particularly the direct exploitation of the IVW data without the need of any assumption on the vertical distribution of the water vapor. This information, completed by reference data at the top (negligible humidity near the tropopause) and at the base of the profile (humidity sensor data) will give us a unique opportunity to fine-tune the retrieval algorithm and to cross check the measurement quality.

Finally, the humidity profiles retrieved with the VHF profiler will be validated by comparisons with the LaMP newly acquired water vapor Raman lidar.