Variability of Integrated Water Vapour: An Assessment on Various Scales with Observations and Model Simulations over Germany

• Main Author: Steinke, Sandra
• Format: Doctoral or Postdoctoral Thesis
• Language: German; English
• Published: 2017
• Subjects: ddc:550; Aerosol Robotic Network
• Online Access: https://kups.ub.uni-koeln.de/7629/; https://kups.ub.uni-koeln.de/7629/1/Steinke_Sandra_PhDThesis_2017_Variability_IWV.pdf

Since water vapour plays a key role in several atmospheric processes on various scales including cloud formation and precipitation it is highly variable in both space and time. The characterization and quantification of its variability is crucial for improvement in parametrization of subgrid scale processes in climate and weather prediction models as well as for evaluation of highly resolving simulations. The present work focuses on the characterization and quantification of integrated water vapour (IWV) variability on meso-α to meso-γ scales over Germany. First of all, a multi-instrument intercomparison during the two months of High Definition Clouds and Precipitation for advancing Climate Prediction (HD(CP)^2) Observational Prototype Experiment (HOPE) is performed to provide a realistic error estimate for the individual instruments observing IWV. The campaign took place from 1 April to 31 May 2013 at the Forschungszentrum Jülich (FZJ) in Germany (50.9°N, 6.4°E). During this two-month period, standard instrumentation for observing water vapour at Jülich ObservatorY for Cloud Evolution (JOYCE), including Global Positioning System (GPS) antenna of the GeoForschungsZentrum Potsdam (GFZ), a scanning microwave radiometer (MWR), and a sunphotometer from Aerosol Robotic Network (AERONET), was complemented by frequent radiosoundings and four additional MWRs all within less than 4 km distance of each other. In addition to the ground-based measurements, IWV estimates from two Moderate Resolution Imaging Spectroradiometer (MODIS) retrievals, near infrared (NIR) and infrared (IR), that provide information with spatial resolution of 1 and 3 km, respectively, are available from satellite overpasses. The comparison reveals a good agreement in terms of standard deviation (≤ 1 kg m^−2 ) and correlation coefficient (≥ 0.98). The exception is MODIS, which appears to suffer from insufficient cloud filtering. Based on the results of the intercomparison, observations of the Germany-wide GPS network are chosen for evaluation of two ...