Improved Lyman-alpha hygrometer. Part III: Performance of a field version for small scale atmospheric turbulence measurements over the sea.

An all-weather ruggedized and simplified version of the IMST/SA–CNRS improved Lyman-alpha hygrometer has been developed in cooperation with Riso\ National Laboratory to measure the small-scale, high-frequency fluctuations of humidity at an open-sea research platform. This version is characterized by the integration of the photomultiplier detection electronics inside the support and by a casings design especially adapted to operation in adverse conditions. Comparisons with other fast hygrometers during the HEXOS Main Experiment indicate that this instrument has probably, to date, the best sensitivity, signal-to-noise ratio, and effective frequency limit. It is able to measure the entire inertioconvective subrange of scales and probably, under some conditions, a part of the dissipation range. [ABSTRACT FROM AUTHOR]