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The total solar eclipse of 11 August 1999 over Central Europe was also visible in Baden-Wuerttemberg, a state in southwest Germany. To investigate the impact of the total solar eclipse on the lower planetary boundary layer, meteorological and air quality data extracted from routine measurements at six sites in Baden-Wuerttemberg were examined. The meteorological data were recorded at the Plittersdorf meteorological station (in the path of totality of the total solar eclipse) and at the Forestmeteorological Site Hartheim (outside the path of totality of the total solar eclipse). The air quality data were obtained from four of cial air quality monitoring stations located at Freudenstadt, Karlsruhe-West, Rastatt and Welzheimer Wald, all of which lie within the path of totality of the total solar eclipse. Due to cloudiness, weather conditions on 11 August 1999 were not optimal in southwest Germany. However, the transient reduction (followed by a rise) induced by the total solar eclipse on meteorological variables including global solar radiation, upward longwave radiation, net radiation, air temperature, horizontal wind speed, elevation angle of the three-dimensional wind vector as well as turbulent sensible and latent heat uxes was quite obvious. Despite unfavourable weather conditions, half-hourly mean values of ozone routinely measured at the above-mentioned standard of cial air quality monitoring stations showed a varying decline up to 27% at the urban station Rastatt and 37% at the background station Welzheimer Wald. This decline was owing mainly to the fall in global radiation during the total solar eclipse. However, additional in uences by advection and deposition can not be precluded. Zusammenfassung Die totale Sonnen nsternis am 11. August 1999über Mitteleuropa konnte auch im Südwesten von Deutschland im Bundesland Baden-Württemberg beobachtet werden. Ihre Auswirkung auf die untere planetare Grenzschicht wurdeüber Daten untersucht, die routinemäßig an der meteorologischen Station Plittersdorf in der Kernzone der Sonnen nsternis und an der Forstmeteorologischen Messstelle Hartheim außerhalb der Kernzone der Sonnen nsternis sowie an den vier amtlichen Luftmessstationen Freudenstadt, Karlsruhe-West, Rastatt und Welzheimer Wald innerhalb der Kernzone der Sonnen nsternis erhoben werden. Obwohl am 11. August 1999 in Südwestdeutschland kein Strahlungswetter herrschte, ließen sich als Folge der Sonnen nsternis die Abnahme und anschließende Zunahme von Globalstrahlung, langwelliger Ausstrahlung der Erdober äche, Strahlungsbilanz, Lufttemperatur, horizontaler Windgeschwindigkeit , Elevationswinkel des dreidimensionalen Windvektors sowie turbulenter Ströme fühlbarer und latenter Wärme erkennen. Trotz ungünstiger Wetterverhältnisse zeigte sich auch bei den Halbstundenmittelwerten von Ozon, die an amtlichen Luftqualitätsmessstellen in der Kernzone der Sonnen nsternis in Baden-Württemberg routinemäßig gemessen werden, häu g eine Reduktion. Sie betrug an der Stadtstation Rastatt bis zu ca. 27% und an der Hintergrundstation...

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Long‐term measurements (1974–1993 and 1996, respectively) of the net radiation (Q), global radiation (G), reflected global radiation (R), long‐wave atmospheric radiation (A) and thermal radiation (E) of a pine forest in Southern Germany (index p) and of a grass surface in Northern Germany (index g) are compared. The influence of changes in surface properties is discussed. There are, in the case of the pine stand, forest growth and forest management and in the case of the grass surface, the shifting of the site from a climatic garden to a horizontal roof. Both series of radiant fluxes are analyzed with respect to the influences of the weather (cloudiness, heat advection). To eliminate the different influence of the solar radiation of the two sites, it is necessary to normalize by means of the global radiation G, yielding the radiation efficiency Q/G, the albedo R/G=α and the normalized long‐wave net radiation (A+E)/G. Furthermore, the long‐term mean values and the long‐term trend of yearly mean values are discussed and, moreover, a comparison is made of individual monthly values. Qp is twice as large as Qg. The reason for this is the higher values of G and A above the pine forest and half values of αp compared to αg. Ep is only a little greater than Eg. The time series of the radiation fluxes show the following trends: Qp declines continuously despite a slight increase of Gp. This is mainly due to the long‐wave radiation fluxes. The net radiation of the grass surface Qg shows noticeably lower values after the merging of the site. This phenomenon is also dominated by the long‐wave radiation processes. Although the properties of both site surfaces alter, Ep and Eg remain relatively stable. Ap and Ag show a remarkable decrease however. The reason for this is to be found in a modification of the heat advection, showing a more pronounced impact on the more continentally exposed site (pine forest). Compared to αg, αp shows only a small variability. The changes of αp can be easily explained as resulting from the influence on the albedo of alterations in cloudiness and the changes in the water storage in stand and soil produced by varying weather conditions. The influence of the forest management is only small and short‐termed. αg reacted with a leap on site merging, followed by a continuous drop. The drop of the grass surface albedo αg on top of the observatory is probably related to the gradual development of the newly sown lawn there and the resultant change in the specific hydrological balance of the soil. A decreasing radiation efficiency Q/G at both sites is observed, which is principally due to an increase in −(A+E)/G. The investigation discovered changes in the long‐wave radiation processes. Its influence in Q should lead to more attention to the long‐wave radiation processes in routine monitoring of radiation. Copyright © 1999 Royal Meteorological Society

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