MSG cloud mask initialisation in hydrostatic and non-hydrostatic NWP models Sibbo van der Veen KNMI De Bilt, The Netherlands EMS conference, September 2012, Lodz, Poland Changing initial clouds in Hirlam / Harmonie: Use: cloud mask nowcasting SAF MSG cloud top temperatures Synoptic cloud base heights Relation between cloud amount and specific humidity: Preserve buoyancy when changing humidity (keep virtual T constant) especially important in Harmonie! Correction: N: 3-D cloud cover (N>0)(N=0) Apply to: 1) Hirlam (hydrostatic) * 4 seasons verification See Van der Veen, S. H., 2012: Improving NWP model cloud forecasts using Meteosat Second Generation imagery. Accepted for publication in Mon. Wea. Rev. * RUC (in cooperation with Siebren de Haan, KNMI) 2) Harmonie (non-hydrostatic) Spin up / spin down rainfall / cloud cover Limit initial humidity changes to 10% (optimisation of precipitation forecasts) results based on ~ 140 runs Example: cloud creation and cloud removal 1. Hirlam Rapid Update Cycle Semi-operational (version 7.3), 11 km 3d VAR Observations: Mode S, AMDAR, synop, GPS Analysis every hour Forecast length: 6 h Period: 5 May 23 December 2011 Control run and MSG run (Kain-Fritsch) Observations used for verification: AMDAR: upper air temperatures Synop: cloud amounts Synop: pressure Synop: 2-m temperature Verification of forecast cloud amounts: Standard deviation / bias cloudiness averaged over whole period Verification of precipitation forecasts Verification of upper air temperatures: Verification of 2-m temperatures: Standard deviation: slightly better Bias: worse! (radiation module?) Verification of forecast surface pressure: 2a) Convection in Harmonie Case study: 10 July 2010 Analysis times: 12 / 18 UTC Severe thunderstorms over the Netherlands CNTR 18+(3-2) MSG CNTR 12+(9-8) MSG 2b) Fog in Harmonie Two experiments: with and without cloud mask / synop initialisation Cycling frequency: once every 6 hours Period: 15 30 March 2012 Area: The Netherlands / North Sea Example showing impact: 22 March, 06 UTC + 24h forecast CNTR +1 MSG CNTR +2 MSG CNTR +3 MSG CNTR +4 MSG CNTR +5 MSG CNTR +6 MSG CNTR +7 MSG CNTR +8 MSG CNTR +9 MSG CNTR +10 MSG CNTR +11 MSG CNTR +12 MSG CNTR +13 MSG CNTR +14 MSG CNTR +15 MSG CNTR +16 MSG CNTR +17 MSG CNTR +18 MSG CNTR +19 MSG CNTR +20 MSG CNTR +21 MSG CNTR +22 MSG CNTR +23 MSG CNTR +24 MSG Summary (1): > Initialisation procedure Hirlam / Harmonie: * change spec. humidity after analysis (MSG, synoptic cloud base) > Verification results for Hirlam: * better cloud cover, precipitation, upper air temperatures, surface pressure for forecasts * worse bias of 2-m temperatures > Conclusion: * (variational) data assimilation not necessary for humidity in Hirlam > Convection in Harmonie: Initial MSG cloud mask in Harmonie increased thunderstorm precipitation considerably in +3h and +9h forecasts > Fog in Harmonie: MSG cloud mask can remove erroneous fog fields in forecasts (up to +24 h) > buoyancy correction in Harmonie: significant impact (more rain if not applied) Summary (2): Outlook: -Improve initial cloud base over ocean -MSG in Harmonie semi-operational -More verification of Harmonie