1. COSMO General Meeting Zürich, 20 - 23 Sept 2005 christoph.schraff@dwd.de 05.08.2005 - 1 - 1 Christoph Schraff christoph.schraff@dwd.de Revision of Quality Control for Radiosonde Humidity 24-h precipitation analysis for 1 August 2004, 6 UTC relative humidity profile at Stuttgart 31 July 17 UTC LM ass without use of profile ref LM ass obs Motivation ‘ref’ LM assimilation opr. humidity QC setting Stuttgart > 100 mm

2. COSMO General Meeting Zürich, 20 - 23 Sept 2005 christoph.schraff@dwd.de 05.08.2005 - 2 - 2 threshold quality control for individual observations (first guess check) relative humidity observation RH o rejected if :| RH o – RH b | > RH thr z T  crit TokTok T o k+1 sTsT  further revision to increase threshold in stable conditions and in particular at inversions where model errors are known to be larger ( limit RH thr(3) (t o ) ≤ 70 % )  b   b * (1 + f stable + f invers ), where for lapse rate  >  crit = – 0.0065 K/m : f stable = ¼ * (1 +  s T /(1+  s T )) * (1 – min{ ,0} /  crit ) operational (‘ref’) : RH thr (t o ) = 70 %, RH thr (t[h]) = RH thr (t o ) * (1 + 0.1* | t o – t | ) revision (analogous to revised GME scheme): RH thr(1,3) (t o ) = min { (  o 2 +  b 2 ) ½, 2  b } * c flag(1,3), where observation error  o = 10 % ( 15% for T o < 233K, 20% for RH o < 20% ) background error  b = 10 % ( 15% south of 30 N ) constant c flag(3) = 3.1 ( c flag(1) = 1.8 for flag 1 as used in multi-level check ) for lapse rate  > 0 : f invers = 0.2 *  T invers * (1 + min{2,  / 0.05 [K/m] } )  both factors increase with increasing stability  and with increasing  T

3. COSMO General Meeting Zürich, 20 - 23 Sept 2005 christoph.schraff@dwd.de 05.08.2005 - 3 - 3 multi-level check define ‘analysis layers’: as standard layers, except  p = 50 hPa below 700 hPa  p = 25 hPa below 800 hPa (boundaries of standard layers: p s, 925, 775, 600, 450, criterion:if 4 or all consecutive standard layers contain observations with flag > 0, set these standard layers to rejected follow-up criterion:each analysis layer within these standard layers are rejected if they contain observations with flag > 0 all observations within these rejected analysis layers are rejected

4. COSMO General Meeting Zürich, 20 - 23 Sept 2005 christoph.schraff@dwd.de 05.08.2005 - 4 - 4 spatial consistency check of integrated water vapour derive observation increments of IWV from radiosonde humidity profiles and optionally from ground-based GPS ZPD data at each observation location, an ‘analysis increment’ is computed from neighbouring observations analysis increments used to correct model background value to obtain a better estimate of ‘truth’  revised first guess check many observations used for analysis increment  better estimate of truth  decrease threshold large analysis increment = disagreement of model and obs  large uncertainty  increase threshold no neighbouring observations (no GPS) :first guess check on IWV many neighbouring observations :checks consistency of current obs to them

5. COSMO General Meeting Zürich, 20 - 23 Sept 2005 christoph.schraff@dwd.de 05.08.2005 - 5 - 5 why all this ? if threshold RH thr too small  too many good observations near inversions are rejected 13 Feb 2003, 0 UTC (old) GME QC thresholds too tight → GME thresholds revised larger stability-dependent thresholds thresholds too small (no IWV-QC) new QC incl. IWV, larger thresh. ok LM ass., opr. QC (ref) 01:53 NOAA IR

6. COSMO General Meeting Zürich, 20 - 23 Sept 2005 christoph.schraff@dwd.de 05.08.2005 - 6 - 6 results, low stratus period low-stratus period 8 – 13 Feb 2003, assimilation cycle with forecasts (GPS used / not used) -multi-level check rejects 4 % of profiles (completely or partly, above p s … 700 hPa) -IWV check rejects 1 % of profiles (completely) -<< 1 % of remaining individual observations rejected by first guess check -> 80 % of rejected data are close to lateral domain boundaries (within ~ 50 grid points)  boundary fields too moist (GME-OI)  background field too moist  rejection of (good) profile new QC ref QC obs 12 UTC Warsaw 12 Feb 0 UTC new QC ref QC obs 13 Feb 2003, 12 UTC Warsaw boundary east-west vertical cross section LM-ass. using Warsaw sounding 12 Feb 2003, 0 UTC

7. COSMO General Meeting Zürich, 20 - 23 Sept 2005 christoph.schraff@dwd.de 05.08.2005 - 7 - 7 Stuttgart 30 July 23 UTC new QC ref QC obs Stuttgart 19 July 23 UTC new QC ref QC obs 24-h precipitation 30 – 31 July 2004, 6 UTC > 100 mm humidity profile rejected by spatial consistency check of IWV > 100 mm LM ass, ref QCLM ass, new QCobserved precipitation 24-h precipitation 19 – 20 July 2004, 6 UTC humidity profile above 925 hPa rejected by first guess / multi-level check

8. COSMO General Meeting Zürich, 20 - 23 Sept 2005 christoph.schraff@dwd.de 05.08.2005 - 8 - 8 Stuttgart 22 July 23 UTC new QC ref QC obs 24-h precipitation 22 – 23 July 2004, 6 UTC humidity profile not rejected ! Stuttgart 23 July 17 UTC new QC ref QC obs 24-h precipitation 23 – 24 July 2004, 6 UTC humidity profile rejected (only) above 850 hPa by first guess / multi-level check observed precipitationLM ass, ref QC 75 mm LM ass, new QC 50 mm 20 mm 30 mm

9. COSMO General Meeting Zürich, 20 - 23 Sept 2005 christoph.schraff@dwd.de 05.08.2005 - 9 - 9 summary introduced smaller, stability-dependent thresholds for radiosonde humidity adjusted multi-level check, rejects 2 % (summer period) to 4 % (low-stratus winter period) of humidity profiles introduced IWV spatial consistency check (both for radiosonde and GPS data; without dense GPS data  IWV first guess check), rejects 1 % of profiles QC accepts almost all good data near inversions rejects most erroneous profiles of radiosonde Stuttgart (in particular the ones with worst impact) will go into next LM version and become operational