Fersch, B.

Heidbach, K.

Kunstmann, H.

Weiß, E.

English

KITopen

Figure 4 compares the time series for 2m-temperature, air pressure, short wave radiation, and relative humidity. The colors red, blue, and orange depict the forecasts for day 1, day 2 and day 3. The baseline triangle marks the station reference. The point, square, and downward triangle symbols represent the different domains. Helmholtz Climate InitiativeRegional Climate ChangeEvaluation of Regional Atmospheric Simulationswith TERENO Pre-Alpine Observations (TP4)Benjamin Fersch (fersch@kit.edu), Katja Heidbach, Elisabeth Weiß and Harald KunstmannKIT IMK-IFU, Garmisch-Partenkirchen www.reklim.dePreliminary ResultsConclusion and OutlookStudy Site and Measurement EquipmentObjectivewww.imk-ifu.kit.eduRegional Atmospheric SimulationsSince October 2011, all three major measurement sites of the Pre-Alpine Terrestrial Environmental Observatory (TERENO) are in full operation with online data transfer. Beside of the high frequency eddy flux measurements, meteorological observations are derived with a 10 minute interval. The new data provides great temporal and promises good comparability on the scale of regional atmospheric modeling. This study presents a first comparison between the TERENO Pre-Alpine station measurements and simula-tions with the Advanced Weather Research and Forecast model WRF-ARW.The WRF-ARW simulations depict a series of dynamically downscaled predictions of the Global Forecasting System (GFS) of NOAA. The model is set up with 3 nested do-mains and 42 vertical layers. Every day, a 72 hour prediction is computed. Soil moisture and temperature, and snow variables are initialized from the WRF-ARW forecast of the previous day. The Pre-Alpine observatory encompasses the Ammer river catchment. Three mea-surement facilities (Fendt, Rottenbuch, and Graswang) are installed over grassland with an north to south elevation gradient from 600 to 860 m.a.s.l. The Graswang location represents a complex alpine valley terrain. In 2012, further climate stations and precipitation gauges will be mounted throughout the Pre-Alpine observatory. Additional measurement facilities will be established in  mountainous environments.Moreover, the regional atmospheric model driving will be extended from the GFS fore-casts to global analysis and reanalysis products. In a further step, the comparison should also address the benefits of fully two-way coupled models like WRF-Hydro, and WRF-HMS.In general, the dynamical downscaling with the WRF-ARW model yields an improved representation of the atmospheric state near the surface. For Fendt and Rottenbuch the skill improves with increasing domain resolution. However, for Graswang better results are achieved with the coarser domains. We assume that the special features of this nar-row mountain valley are not yet resolved by the finest regional domain. A further incre-ment in spatial resolution could be a solution. Fendt (600m, Pre-Alpine Lands)Rottenbuch (750 m, Plateau)Graswang (860 m, Alpine Valley)Fig.4: Taylor diagram comparison of regional atmospheric model and TERENO Pre-Alpine observations,            2011-12-15 to 2012-03-13 (90 days) for the sites Fendt, Graswang, and RottenbuchDomain 1 (60km) Domain 3 (3.3km)Domain 2 (20km)MunichFig. 3: WRF model domain configurationSetup Domain 3• Goddard SW RAD• Goddard LW RAD• Grell-Devenyi  CU• Goddard GCE MP  Better for short forecasts; not always improving with increasing resolution  Better for short forecasts; 20km resolution equal to 3.3km    Decreasing skill with inc. forecast time;  improvement with inc. resolution  Weak coherence; in general improvement with increased resolution  3.3km run resembles the station characteristics best  3.3km run fails except for pressure; best results obtained with 20km  Similar to Fendt, increasing resolution improves the skillTemperature:Pressure :Radiation:Humidity:Fendt:Graswang:Rottenbuch: Fig. 1: TERENO Pre-Alpine extent and measurement site configurationFig. 2: Data gaps: one point equals a 10 minutes lackRottenbuch GraswangThe measurements are recorded with an interval of one minute and 10 minute mean values are computed by the data logger.Due to the 3 weeks cold period in early 2012 with temperatures below -25 °C the power supply for the logger devices failed at Graswang and Rottenbuch.Sensors• Temperature: • Pressure:• Shortwave radiation:• Relative humidity:Vaisala HMP45  (±0.2K)Vaisala WX7 520 (±0.5 hPa)Kipp & Zonen CNR 4 (±10%)Vaisala HMP 45 (±1%)

Evaluation of regional atmospheric simulations with TERENO pre-Alpine observations

https://publikationen.bibliothek.kit.edu/220087009/3816072

Evaluation of regional atmospheric simulations with TERENO pre-Alpine observations

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