Jörg Gerchau

Micrometeorological measurements during the total solar eclipse of August 11, 1999

Micrometeorological measurements of radiation, atmospheric and soil parameters, and turbulent energy and momentum e uxes, ozone and carbon dioxide e uxes have been conducted over a maize e eld at FreisingWeihenstephan in Southern Germany during the total solar eclipse on August 11, 1999. For the period 30 minutes before and after the totality the weather conditions at the location where the micrometeorological measurements were made was satisfactory. Several connections between the irradiation and other meteorological parameters over a maize e eld have been found. The time response between irradiation and the long-wave upward radiation was only a few minutes, whereas almost all parameters caused by the turbulent transport had a time shift of up to 30 minutes. A period of nearly 30 minutes with reduced turbulence regime after the totality was found. Using a wavelet transformation for the time series, a change of time scales from longer to shorter ones was observed before the totality, and after the turbulence increased in the short time scales. The investigation of the residuum of the closure of the energy balance showed that with a time shift for the latent heat e ux (unlike the net radiation) after the totality, a better energy budget closure was obtained.

A Collector for Fog Water and Interstitial Aerosol

Abstract An active heatable cloud water collector for ground sampling is presented. The collector can be operated unattended for approximately one week, even in harsh winter conditions. The collection strands are Teflon tubes. A preset cycle of 15-min sampling followed by 250 s of mild heating using wires inserted into the tubes is used. The lower cutoff diameter for fog droplets is 7.3 μm, and its overall collection efficiency is 79% for the liquid water content of fogs at the experimental site in central Europe. It performed reliably during a 2-yr experiment. The collected fog water interacts exclusively with inert materials such as Teflon and Perspex so the collector is well suited for trace analyses of fog water. The collector can be upgraded with an interstitial aerosol collection unit, at the expense of unattended operation. The lower cutoff diameter of the fog water collection strands is 8.1 μm when the interstitial aerosol module is installed. The module efficiently collects particles with diamete...