Verification Verification with SYNOP, TEMP, and GPS data P. Kaufmann, M. Arpagaus, MeteoSwiss P. Emiliani., E. Veccia., A. Galliani., UGM U. Pflüger, DWD

Verification Surface Verification with SYNOP Verification scores neglecting a diurnal cycle

Verification 2 6th COSMO General Meeting, Sept 2004, Linate Availability of SYNOP data on GTS Red dots: all “main” SYNOPS (6- hourly) available GB: Sea level pressure but no pressure at station height Spain, Italy, Balkans: Many stations do not report during the night (not even the automatically measured parameters) PMSL PS

Verification 3 6th COSMO General Meeting, Sept 2004, Linate SYNOP Pressure: Standard Deviation of Errors Standard deviation of errors (STDE) is considerably larger in winter than in summer In winter much larger in the north than in the south Winter 2003/4, 42 – 48 h Summer 2004, 42 – 48 h

Verification 4 6th COSMO General Meeting, Sept 2004, Linate SYNOP Pressure Dependence of mean error (ME) on forecast range Winter: Increase Summer: Decrease Winter 2003/4 Summer 2003 but …

Verification 5 6th COSMO General Meeting, Sept 2004, Linate SYNOP Pressure … decrease in summer disappeared in summer 2004 Effect of ECMWF-IFS boundary conditions? Supported by results of IFS test chain summer 2003 Summer 2004

Verification 6 6th COSMO General Meeting, Sept 2004, Linate Model Grid Points over Water on Coasts and Lakes Winter 2003/4, forecast range 42 – 48 h Coasts and lakes: Large bias if model grid points over water are used! but: small bias for small islands and oil platforms – not all water points need to be eliminated Nearest grid point regardless of surface type Land points preferred

Verification 7 6th COSMO General Meeting, Sept 2004, Linate SYNOP Temperature Strong cold bias in winter (see verification of daily cycle), pronounced in Alps Weak cold bias in summer Standard deviation high in complex terrain Winter 2003/4, 42 – 48 h STDE ME Summer 2004, 42 – 48 h ME

Verification Verification with TEMPs Vertical profiles

Verification 9 6th COSMO General Meeting, Sept 2004, Linate TEMP Geopotential Summer 2004 (JJA) Sharp increase of mean error in stratosphere, reason unclear Standard deviation largest around tropopause LM only: negative bias below 600 hPa at +48 h LM ME aLMo ME STDE

Verification 10 6th COSMO General Meeting, Sept 2004, Linate TEMP Geopotential aLMo – LAMI “South of the Alps” aLMo 6 stations LAMI 7 stations LAMI only July, August Bias differences to aLMo below 500 hPa: Bias at +12 h more positive Negative bias at +48 h LAMI and LM both driven by GME, aLMo by IFS aLMo ME

Verification 11 6th COSMO General Meeting, Sept 2004, Linate TEMP Temperature Summer 2004 (JJA) Cold bias up to 0.7 K between 1000 and 750 hPa Warm bias 750 – 500 hPa, increase with forecast time up to 0.6 K Weak cold (LM: no) bias 500 – 250 hPa aLMo only: Strong cold bias in the stratosphere (150 hPa) Analysis (+00) h far better than all others – effect of nudging Standard deviation largest spread around tropopause (200 hPa) LM ME aLMo MESTDE

Verification 12 6th COSMO General Meeting, Sept 2004, Linate TEMP Temperature aLMo – LAMI LAMI only July, August Smaller cold bias near surface Warm bias extends higher up, up to 200 hPa level aLMo ME

Verification 13 6th COSMO General Meeting, Sept 2004, Linate TEMP Relative humidity Summer 2004 (JJA) Bias of varying sign, 5 – 8%, related to bias of temperature? Moist below 850 hPa Dry between 850 hPa and 500 hPa Moist between 500 hPa and 200 hPa Dry above 200 hPa Clear distinction between analysis and forecasts Standard deviation nearly uniform over large part of troposphere LM ME aLMo ME STDE

Verification 14 6th COSMO General Meeting, Sept 2004, Linate TEMP Humidity aLMo – LAMI Relative humidity and dew point temperature are not directly comparable ? aLMo ME Relative humidity biasDew point bias

Verification 15 6th COSMO General Meeting, Sept 2004, Linate Long term evolution of RH RMSE Decrease of RMSE for LM in 2004 Effect of prognostic ice scheme and assimilation of pseudo- TEMPS from ECMWF into GME LM RMSE of relative humidity

Verification 16 6th COSMO General Meeting, Sept 2004, Linate TEMP Wind speed aLMo Summer 2004 (JJA) Mean error well below 1 m/s Slightly increasing with forecast time Largest in boundary layer and near or above tropopause Boundary layer: Different sign of bias for LM and aLMo Standard deviation largest at tropopause, consistent with strongest winds LM ME aLMo MESTDE

Verification 17 6th COSMO General Meeting, Sept 2004, Linate TEMP Wind speed aLMo – LAMI Only stations south of the Alps Largest bias at 700 hPa

Verification Verification with GPS Vertically Integrated Water Vapour

Verification 19 6th COSMO General Meeting, Sept 2004, Linate GPS Integrated Water Vapour Path delay (W – W 0 ) caused by refraction Error for geodesy Signal for meteorology Refractivity index depends on Dry-air density (hydrostatic delay) Humidity (wet delay) Wet delay = total delay – hydrostatic delay Integrated water vapour: Need of surface pressure and temperature from nearby SYNOP Currently calculated by KNMI

Verification 20 6th COSMO General Meeting, Sept 2004, Linate GPS data availability Three processing centers deemed most reliable Each covers primarily its home country Time series have many gaps Processing centers are not WMO members LPT Switzerland GFZ GermanyGOP Czechia

Verification 21 6th COSMO General Meeting, Sept 2004, Linate GPS IWV BIAS Weak dry bias outside complex topography Bias (or mean error) is largest In summer In the mountains Possible explanations Larger specific humidity contents in summer than in winter Height differences GPS antenna – SYNOP station – model surface are largest in mountainous terrain Summer 2003 Winter 2002/3

Verification 22 6th COSMO General Meeting, Sept 2004, Linate GPS IWV Standard Deviation STDE largest in summer Homogeneous in whole model domain Problem in mountains only affect bias, i. e. values are shifted by constant offset Summer 2003 Winter 2002/3

Verification 23 6th COSMO General Meeting, Sept 2004, Linate Summary and Outlook Model verification often stops at national boundaries: Model comparison difficult Surface verification with SYNOP Pressure increase/decrease with forecast range Strong cold bias in winter Need for continuous, quality-controlled data for the whole of Europe! Model comparison even for TEMP difficult. Differences: Set of stations Time (definition of a season) Statistical measures used: Only two out of ME, MAE, STDE, RMSE GPS Data availability problem (currently only available through European project; each centre provides subset only ) Zenith total delay (ZTD) verification in the future to avoid interpolation problems between SYNOP and GTS locations