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Untersuchungen troposphaerischen Ozons mit DIAL

By G.C. Grabbe and Hamburg (Germany) Max-Planck-Institut fuer Meteorologie


This work contains meteorological investigations of ozone measurements by using the DIAL technique. An extensive intercomparison of DIAL measurements and mesurements made by an ECC sonde was made to check the reliability of the system. For the first time results of an ozone DIAL were compared to results of free flying sondes and tethersondes. The agreement is very good. The average difference of the 10 compared measurements with free flying sondes was 3.6 #mu#g/m"3 (4.1%). The six comparisons of results of the tethersonde showed an average difference of 3.5 #mu#g/m"3 (3.5%). The new technique of comparing DIAL measurements with tethersondes also allowed intercomparisons of trends and standard deviations of the measurements. In order to answer the equation of what caused the larger standard deviation of the lidar measurement in three out of four cases an analysis of the spectral density of the variance was made. The lidar measurement contains errors only at heights with large gradients in the aerosol concentration caused by uncertainties in the knowledge of the aerosol parameters. During an ozone episode the increase of the ozone density was about 50 #mu#g/m"3 in the boundary layer (PBL) within 60 hours, while there is an increase of only 3% in the lower free troposphere (LFT) within the first 24 hours. During the night persisting high ozone densities exist within the former PBL while there is a reduction of ozone at ground level. The increase of ozone within the PBL could partly be explained with advection of ozone rich air from East Germany and the Czech Republic by calculating backward trajectories. To model an ozone episode three factors have to be known: advection, turbulent mixing and thickness of the atmospheric layers. In the case shown here, the PBL values were modeled better than the values at ground level. Altogether, the results from the model used here were satisfying, if the three factors are taken into account. With the MPI ozone DIAL it is possible to measure the annual variation of the ozone density in the LFT. The minimal measured value within the three years of measurements is 54 #mu#g/m"3, the maximal value 116 #mu#g/m"3. The average is 83 #mu#g/m"3. The monthly mean values varied between 70 #mu#g/m"3 in December and 108 #mu#g/m"3 in May. The influence of meteorological parameters, such as temperature, relative humidity, wind direction and wind velocity is much less in the LFT than at ground level with the exception of the wind direction. Due to linear regression or fit of a cosinus function to the data, the standard deviation can not be reduced significantly in comparison to the standard deviation from the mean value within the LFT, while at ground level there is a significant reduction when correlating ozone with temperature or relative humidity. Under different grosswetterlagen (GWL), there was 6% more ozone during tropical air masses in the LFT, while there was 8% less ozone during maritime air masses than on the average. At ground level there was 14% more ozone during continental air masses of tropical origin and 15% less during maritime air masses of tropical origin than on the average. Due to the large scattering of the data, the standard deviation could not be reduced significantly in comparison to the standard deviation from the average value by splitting up the data into GWLAvailable from TIB Hannover: RR 9(31) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Year: 1995
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Provided by: OpenGrey Repository
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