Page 1 Developments in regional DA Oct 2007 © Crown copyright 2007 Mark Naylor, Bruce Macpherson, Richard Renshaw, Gareth Dow Data Assimilation and Ensembles, Met R & D Developments in regional data assimilation at the Met Office EWGLAM / SRNWP 2007 new NAE UK4

Page 2 Developments in regional DA Oct 2007 © Crown copyright 2007 NAE Data Assimilation changes 2007  GPS IWV introduced (1 per 6 hr)  aerosol background error reduced  AIRS over land introduced (above 400hPa)  More frequent ATOVS data ( + thinning 40  80km)  More frequent GPS IWV data (1 per hr)  PF-Model Convection  cease soil temperature increments under snow  introduce IASI  introduce ASCAT Mar 07 Aug 07 Nov 07

Page 3 Developments in regional DA Oct 2007 © Crown copyright 2007  Impact of LS subsidence (similar to first ECMWF scheme) positive impact on moisture field  Cape closure perturbations (main term) positive impact on virtually all fields PF convection parametrisation in 4DVAR (Olaf Stiller) Two contributions: Unsteady/noisy UM convection scheme motivated statistical approach with time smoothing of input fields from nonlinear model

Page 4 Developments in regional DA Oct 2007 © Crown copyright 2007 PF convection – linearisation test (Olaf Stiller) after 6 hours

Page 5 Developments in regional DA Oct 2007 © Crown copyright 2007 PF convection - trial results  Summer 2006 NAE trial  Generally beneficial in most variables  +1% on UK Index (skill score for T2m, v10m, rain, cloud, visibility)  rms PMSL  rms T2m

Page 6 Developments in regional DA Oct 2007 © Crown copyright 2007 soil temperature increments  ΔT (soil level 1) = ΔT (atmosphere level 1) in NAE  helps retain benefit of screen temperature assimilation  (no screen level assimilation or ΔT (soil) in global model) CNTL no ΔT(soil) mean T2m rms T2m

Page 7 Developments in regional DA Oct 2007 © Crown copyright 2007 soil temperature increments …..under snow  ΔT (soil level 1) = ΔT (atmosphere level 1)  not sensible when snow insulates the soil  Feb 07 night-time T2m errors in Finland ~10-15K soil temp difference (NAE-GLOBAL) snow cover 20K !

Page 8 Developments in regional DA Oct 2007 © Crown copyright 2007 Ground GPS IWV (operational since March 07)  Operational coverage

Page 9 Developments in regional DA Oct 2007 © Crown copyright 2007 Ground GPS IWV ● Pre-operational trials gave slight benefit in screen temperature, rain, cloud and visibility. (~0.5% on UK Index) ● Obs frequency increased to hourly (Aug 07) with neutral impact / slight benefit ● Further trials to optimise assimilation underway- adjusting obs errors and forward model

Page 10 Developments in regional DA Oct 2007 © Crown copyright 2007 IASI trial  1-month trial – May 2007  Global trials gave benefit in PMSL & upper-level winds  NAE trial showed small benefit in UK pmsl mean rms CNTL IASI

Page 11 Developments in regional DA Oct 2007 © Crown copyright 2007 ASCAT  ASCAT data – implementation due Nov 07 in NAE  10-day NAE trial May 2007(impact neutral), following longer global trials  ASCAT observations for QY18, with ERS2 and Seawinds

Page 12 Developments in regional DA Oct 2007 © Crown copyright 2007 Weather radar – VAD winds  Currently  assimilated 61  rejected 26

Page 13 Developments in regional DA Oct 2007 © Crown copyright 2007 VAD wind impact experiment  3-week 24km NAE 4DVAR test, autumn 2006 CNTL noVAD mean pmsl rms pmsl

Page 14 Developments in regional DA Oct 2007 © Crown copyright 2007 VAD wind impact experiment - 2  Pmsl benefit statistically significant when error bars computed for mean difference in CNTL / noVAD errors

Page 15 Developments in regional DA Oct 2007 © Crown copyright 2007 Part 2

Page 16 Developments in regional DA Oct 2007 © Crown copyright km UK model assimilation  3DVAR  nudging scheme for cloud & rainfall assimilation  eight 3-hourly cycles per day  forecasts to t+36 from 03, 09, 15, 21 UTC  lateral boundaries from hh-3 run of 12km NAE

Page 17 Developments in regional DA Oct 2007 © Crown copyright 2007 UK model – increased vertical resolution  38  70 levels  same top at ~40km  7  16 levels in bottom 1km  lowest theta level at 5m  lowest wind level at 2.5m  due for implementation Nov 2007

Page 18 Developments in regional DA Oct 2007 © Crown copyright 2007 UK model – 70 level forecast error covariances  variant of lagged NMC method  74 forecast pairs  t+12 – t+24  horizontal scales  psi130km  chi180km  Ap130km  mu 90km  log m 90km

Page 19 Developments in regional DA Oct 2007 © Crown copyright 2007 UK model – 70 level case study trial – pmsl (17 cases) mean rms L38 L70

Page 20 Developments in regional DA Oct 2007 © Crown copyright 2007 UK model – 70 level case study trial – T2m mean rms L38 L70

Page 21 Developments in regional DA Oct 2007 © Crown copyright 2007 UK model – 70 level case study trial – RH2m mean rms L38 L70

Page 22 Developments in regional DA Oct 2007 © Crown copyright 2007 UK model – 70 level case study trial – v10m rms vector mean speed L38 L70

Page 23 Developments in regional DA Oct 2007 © Crown copyright 2007 UK model – 70 level case study trial – cloud cover rmsmean L38 L70

Page 24 Developments in regional DA Oct 2007 © Crown copyright 2007 UK model – 70 level case study trial – 6-hourly rainfall 0.2mm /6 hr 1mm /6 hr 4mm /6 hr solid L38 dashed L70

Page 25 Developments in regional DA Oct 2007 © Crown copyright 2007 Future work  Upgrade NAE (and global) to 70 levels (Feb 08).  Initial 1-month trial in NAE completed  Physics package still under development  MOPS cloud data in 4DVAR to replace nudging  PF model boundary layer scheme (autumn 08)  ensemble-based covariances  ? replace NAE continuous assimilation with single cycle spin-up from previous global ‘update’ analysis  2009: new computer  retain 12km NAE when global  25km  nest 1.5km UK model with variable resolution perimeter into 12km NAE

Page 26 Developments in regional DA Oct 2007 © Crown copyright 2007 OPERA composite  NAE impact experiment is planned with OPERA composite (Spring 08)  promote benefits to NWP of radar data exchange within Europe  clarify requirements from NWP for operational radar data hub  prepare for eventual operational assimilation

Page 27 Developments in regional DA Oct 2007 © Crown copyright 2007 Questions?

Page 28 Developments in regional DA Oct 2007 © Crown copyright 2007 Visibility/Aerosol tuning  3-week package trial consisting of:-  Reduced visibility background error  Climatological aerosol in radiation (not prognostic aerosol)  Maximum aerosol concentration reduced (200µg/kg)  Relaxation to climatological aerosol increased (20days)  Significant benefit seen in Screen temperature