Remote measurement of trace gas fluxes in the convective boundary layer using differential absorption lidar and radar/Rass

Abstract

Exchange processes of trace gases in the troposphere play an important role in atmospheric dynamics and chemistry. In particular, the vertical transport of water vapor governs a major part of the energy balance, both through direct latent heat transport and through modification of the radiation field by cloud formation. Vertical mixing is most efficiently performed by convective processes, where latent heat release is one of the main driving forces. Ozone is an example for a chemically reactive gas, the importance of which has been increasingly recognized. While many measurements of this gas have been performed on ground stations, and of course in the stratosphere, there is relatively little knowledge about it's vertical distribution in the troposphere. The redistribution of this gas by convective mixing in the boundary layer has a large impact e.g. on the actual surface concentration. While in situ methods certainly can have adequate accuracy and resolution to study convective exchange processes, the available platforms for measurements throughout the boundary layer, e.g. aircraft or tethered balloons, require a rather big effort, both financially and with respect to manpower. In addition, tethered balloons are generally restricted in height and can only be operated in light to moderate minds, and with severe restrictions on the sites of operation. From aircraft it is almost impossible to derive true vertical profiles. Therefore, the authors have started the development of adequate remote sensing methods, some results of which are presented.<>