Institut für Weltraumwissenschaften, Freie Universität Berlin (FUB-WeW):
Precipitation statistics in the Baltic Region
Dr. Ralf Bennartz
Summary:
Observations of the total amount of precipitation and its temporal and spatial distribution are of crucial importance for the understanding of the water cycle. In the Baltic area the total amount of precipitation consists of convective and frontal precipitation in different mixtures. To establish a baseline for regional climate modelling not only the absolute amount of precipitation but also the type of precipitation event has to be monitored. Based on these considerations we will address the following key issues in the project:
- How much of the total amount of precipitation in the Baltic area is related to frontal precipitation and how much to convective events?
- For a given frontal system, what is the amount of precipitation associated with cold and warm fronts and how much precipitation falls within the cold sector of the front?
- How does climate change affect the amount and distribution of precipitation in the Baltic area?
Based on radar and satellite observations a climatology of precipitation over the Baltic area will be derived with special emphasis on the internal variability of precipitation type, intensity and spatial distribution in the Baltic area. In close co-operation with the MPI the REMO precipitation output will be validated. The aforementioned precipitation climatology in conjunction with REMO climate change scenarios will serve as a reference to extrapolate the impact of climate change on the amount and distribution of precipitation in the Baltic area.
Results:
BALTIMOS/REMO
- has too many rain events (24 % ; Radar: 15 %)
- has too many rain events with weak intensities.
- has too less number of extreme events.
- has 14 % more yearly rain amount ( 846 mm; Radar 740 mm)
- simulates summer too dry (~10 %)
- simulates too much precipitation in other seasons (up to 20 %)
- simulates daily amounts with an accuracy of less than 1mm
- underestimates the frontal partition (43 % Radar:56 %)
- simulates the number of frontal passages well
- simulates convective precipitation over land 1-2 hours too early (~13 Local Solar Time)
- simulates typical features of the diurnal cycle according to land/sea distribution well.
