1. Swedish Meteorological and Hydrological Institute SE-601 76 Norrköping, SWEDEN COMPARISON OF AREAL PRECIPITATION ESTIMATES: A CASE STUDY FOR A CENTRAL SWEDISH CATCHMENT Jonas Olsson, Barbro Johansson (presented by Günther Haase) Swedish Meteorological and Hydrological Institute SE-601 76 Norrköping, SWEDEN

2. Swedish Meteorological and Hydrological Institute SE-601 76 Norrköping, SWEDEN Study region - Gimån catchment Catchment area: 4 300 km² Mean annual precipitation: 700 mm Mean altitude: 340 m.a.s.l. (range: 20-540 m.a.s.l.)

3. Swedish Meteorological and Hydrological Institute SE-601 76 Norrköping, SWEDEN Data sources and analyses Sources: PTHBV: interpolated gauge data HIRLAM: NWP model (+30h - +6h forecasts) RADAR: gauge-adjusted radar data MA22, MA11: mesoscale analysis, real-time (22) and climate- corrected(11) Resolution, extension: Temporal: daily accumulations during 2002 Spatial: ~22 km resolution in 72  120 km 2 grid (20 grid nodes) Analyses: Temporal: descriptive statistics and autocorrelation of daily spatial mean precipitation Spatial: standard deviation and correlation

4. Swedish Meteorological and Hydrological Institute SE-601 76 Norrköping, SWEDEN Temporal analysis - descriptive statistics

5. Swedish Meteorological and Hydrological Institute SE-601 76 Norrköping, SWEDEN Temporal analysis - seasonal & autocorrelation

6. Swedish Meteorological and Hydrological Institute SE-601 76 Norrköping, SWEDEN Spatial analysis 2002 totals PTHBV HIRLAM RADAR (maximum=1390 mm) MA22 MA11

7. Swedish Meteorological and Hydrological Institute SE-601 76 Norrköping, SWEDEN Spatial analysis - standard deviation & correlation

8. Swedish Meteorological and Hydrological Institute SE-601 76 Norrköping, SWEDEN Summary - PTHBV vs. MA: The mesoscale analysis consistently generated the lowest amount of precipitation, possibly due to (i) no correction for observation losses and (ii) an underestimation in synoptical observations. - HIRLAM: Somewat different seasonal cycle than the other sources. Low daily areal variability, possibly due to areal smoothing in the model. High areal variability of 2002 totals, possibly due to orographically induced small but systematic areal variations. - RADAR: A distinct inhomogeneity was found, with precipitation amounts being consistently overestimated by ~8 mm/day over a region of 500-1000 km² during October-December. Possible cause: temporary improper functionality of the Östersund radar, north-west of the study catchment.

9. Swedish Meteorological and Hydrological Institute SE-601 76 Norrköping, SWEDEN Runoff simulation (HBV model) 2000-2002