Seminar Ozean, Eis, Atmosphäre

Termin: 28.05.2002

Referent/in: Voltaire Velazco,
Institut für Umweltphysik
Universität Bremen, Bremen

Title: Aerosol Depolarization and Water Vapor Studies from Raman LIDAR Measurements in Chile and in the Arctic

Laser measurements through Light Detection and Ranging (LIDAR) with the use of the Mobile Aerosol Raman LIDAR (MARL) system of the Alfred Wegener Institute in Bremerhaven, Germany were conducted during the INCA* campaign in 2000.

Extensive amount of measurements were performed in Punta Arenas, Chile. The measurements included depolarization and backscatter ratios of clouds and particles in the atmosphere. Water vapor measurements were made possible with the use of the water vapor Raman channel of the MARL system.

The combined measurements show an interesting behavior of particle depolarization and fluctuations in water vapor mixing ratios above the boundary layer. With the use of the depolarization measurements, we were able to detect the presence of microscopic depolarizing particles at 1.8 -2.5 km, which could be aerosols at subzero temperatures.

Statistical analyses reveal strong correlations between particle depolarization and the gradient of the water vapor mixing ratios above the atmospheric boundary layer suggesting the interdependence of the two variables. This implies that optical properties of aerosols such as depolarization are influenced by water vapor and perhaps temperature.

In May 2002, new measurements were performed in the Arctic using the Koldewey Aerosol Raman LIDAR (KARL) located at the NDSC station in Ny Alesund in Spitsbergen. The aim was to supplement the existing data from MARL and to test if aerosols existing in Arctic temperatures behave the same as the aerosols in Chile. Data evaluation of the new measurements is now underway.

Measurements from the far northern hemisphere and the southern hemisphere of the planet from two similar systems will provide more insights on the interplay of aerosols and particles with water vapor in the atmosphere and ultimately, the global climate.