GPS atmosphere sounding project - An innovative approach for the recovery of atmospheric parameters WP 232 - Validation of regional models - BALTEX - and contributions to WP 341 and WP 344

The atmospheric water vapor content is one of the most important parameters for the hydrological cycle. In order to investigate the energy and water balance over the BALTEX study region this report describes comparisons of specific humidity profiles of the hydrostatic High resolution Regional weather forecast Model HRM of the Deutscher Wetterdienst (DWD) with profiles derived from spaceborne radio occultation data of GPS/MET and CHAMP and comparisons with the vertically integrated water vapor (IWV) of different networks of groundbased GPS receivers within Europe. High correlations (with a correlation coefficient around 0.9) between the HRM IWV and GPS IWV were found. It is shown that the analysis data used to initialize the HRM model can explain a large part of the mean difference between the IWV from the model and the GPS data. Specific humidities and the IWVs were determined from the refractivity profiles of the radio occultations of GPS/MET and CHAMP/GPS using an iterative algorithm of Gorbunov and Sokolovski (1993). The comparisons of the specific humidity profiles have shown that both receivers, GPS/MET and CHAMP/GPS, measure significantly lower mean specific humidities below about 4 km than HRM. This is e.g. supported by comparisons between the HRM model and the ECMWF analysis data, between the HRM model and radiosonde ascents at Lindenberg/Germany (which have shown lower mean absolute differences of about 0.2 g/kg) as well as between HRM and further spaceborne data like AMSU-A/B and TERRA/MODIS. Comparisons between CHAMP/GPS and AMSU-A over oceans and AMSU-B over Antarctica show the high value of GPS radio occultations for applications worldwide. (orig.)Available from TIB Hannover: RA3251(03/34) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Geophysikalische Messungen auf dem archaeologischen Ausgrabungsgelaende von Lattes, Suedfrankreich Zweite Exkursion im September 1991 und Zusatzmessungen im September 1992

Available from TIB Hannover: RA 2000(53) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Radiometrische Messungen im arktischen Ozean - Vergleich von Theorie und Experiment

Summary in EnglishAvailable from TIB Hannover: RN 9219(297) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Study of passive remote sensing of the atmosphere and surface ice Executive summary and final report

A radiative transfer model to compute brightness temperatures in the microwave frequency range for polar regions including sea ice, open ocean and atmosphere has been developed. The calculation of the sea-ice reflectivity is incorporated by the 'many layer strong fluctuation theory' model of Grenfell and Stogryn. The surface reflectivity of the open water is computed with three scale model of Schrader. Both surface models supply the bistatic scattering coefficients, which define the lower boundary for the atmospheric model. The atmospheric model computes the gaseous absorption of water vapour and oxygen by the Liebe model. Cloud hydrometeors are considered by Mie- or Rayleigh-scattering. The radiative transfer model has been validated for SSM/I frequencies using six test cases. The ground truth data (surface and atmosphere) has been observed during the ARKTIS'88 and ARKTIS'93 experiments. The simulated brightness temperatures are compared to collocated SSM/I measurements. The validation exhibits shortcomings of the sea-ice model for 37 GHz. The actual reasons for these deviations are unknown, but a possible explanation is an artificial oscillation of the reflectivity as function of frequency and ice-layer thickness. An empirical correction of the reflectivity for this frequncy has been derived and its application gives consistent comparison results between the simulated and observed brightness temperatures within the accuracy range. (orig.)207 refs.Available from TIB Hannover: RN 3292(297) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman