Lengfeld, Katharina (2008) Parametrisierung solarer Einstrahlung aus Modellen und Beobachtungen. (Diploma thesis), Christian-Albrechts-Universität, Kiel, Germany, 77 pp.

Preview

Text 456_Lengfeld_2008_ParametrisierungSolarerEinstrahlungAusModellen_Hschri_pubid11209.pdf - Published Version Available under License German copyright act UrhG. Download (7MB)

Abstract

In this thesis the parameterization of the incoming solar radiation by Schewski (2001) based on model calculations is tested with real measurements. This parameterization based on the mesoscale atmospheric model GESIMA and the radiative transfer model GRIMALDI. The dataset is derived from Lindenberg, Germany, from February to December 2007. 10 minute means are used. The parameterization by Schewski calculates the transmission of the atmosphere in the shortwave range depending on domain averaged cloud cover and liquid water path respectively cloud liquid water. It is shown that the calculation of the incoming solar radiation is correlated quite well with the measurements, but the parameterization underestimates them. To fit the parameterization perfectly to the used data set, the coefficients are varied. The best coefficients are delivered, so that the the mean difference is 0 W/m2, the standard deviation is preferably small and the correlation with diurnal cycle as high as possible. Thereby a reduction of 12% of the standard deviation is reached. The correlation with diurnal cycle is enhanced compared to the original Schewski parameterization. Its value is 0.91. But the correlation without diurnal cycle, which is influenced by the clouds and atmospheric particles, gets a little smaller again. Especially for almost clear sky conditions the differences between measurement and calculation of the incoming solar radiation is high. This case is determined by the coefficients a. These coefficients are replaced by the parameterization of Zillman (1972). The incoming solar radiation is calculated depending on the solar zenith angle, the temperature and the relative humidity. Special coefficients for the clear sky case were derived by Kalisch (2008). The combination of the parameterizations by Schewski and Zillman produces an upgrade of the mean difference and the standard deviation for situations with small cloud cover. In generel the results change hardly. The modified parameterizations are tested with a dataset from Lindenberg from January to September 2006 and produce reductions of the differences between measurements and calculated incoming solar radiation and their standard deviation. The correlation with diurnal cycle is upgraded, too. Only the correlation without diurnal cycle gets a little worse than for 2007. By using this parameterization for a dataset, that is made during a cruise with the FS Polarstern from Bremerhaven to Kapstadt, a only reduction of the differences for the modified Schewski parameterization is shown. The standard deviation and the correlations get worse. The version with Zillman shows enhancements in every statistical parameter compared to the original one except for the correlation with diurnal cycle. But this is still high with 0.907. The results show that it is possible to parameterize the incoming solar radiation based on domain average cloud properties.

Actions (login required)

View Item