1 Rachel Capon 04/2004 © Crown copyright Met Office Unified Model NIMROD Nowcasting Rachel Capon Met Office JCMM

2 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright Outline Unified Model 5.+, 6.+ –New Dynamics Core –Physical Parametrisations –Limited Area Configuration Single Column Unified Model Site Specific Forecast Model Nimrod Nowcasting System

3 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright New Dynamical Core Unified Model 5.x operational since Aug 2002 OLD formulation Eulerian 4 th order advection Split-explicit time integration Horizontal B grid Vertical staggering – Lorenz Sigma pressure coordinate Quasi-hydrostatic formulation NEW formulation Semi-Lagrangian advection Semi-implicit time integration Horizontal C grid Vertical – Charney-Phillips Hybrid height coordinate Non-hydrostatic formulation

4 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright Fully-compressible deep atmosphere equns

5 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright Unified Model Dynamics What’s ‘New’ Fully compressible, non-hydrostatic, deep atmosphere. –Universal application (Climate to microscale) Semi-Lagrangian, Semi Implicit solution. u d is value at departure point, found by high order interpolation. No stability limit on timestep. No additional diffusion required.

6 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright Unified Model Dynamics What’s ‘New’ Terrain following height based vertical coordinate –r(i,j,k) specified Arwakawa C Grid in horizontal (not B) –No averaging of pressure gradient –No grid decoupling –Better geostrophic adjustment for short waves Charney-Philips Grid in vertical –No computational modes –More consistent with thermal wind balance –Can have complications in coupling with boundary layer parametrisation w, ,q u v x y ,  (p)

7 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright Physical Parametrisations Edwards-Slingo Radiation –(Edwards & Slingo 1996) Mixed phase precipitation –(Wilson & Ballard 1999) –Extending to prognostic cloud fraction (Wilson, Bushell) –Extending to prognostic cloud water, rain water, ice, snow, graupel (Forbes) Met Office Surface Exchange Scheme (MOSES I and II) –(Cox, Essery, Betts) Non-local Boundary Layer –(Lock et al 2000) New GWD scheme + GLOBE orography, smoothed (Raymond filter) Mass flux convection scheme with CAPE closure, downdraft and momentum transport, separate shallow cumulus –(Gregory and Rowntree, Kershaw, Grant)

8 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright Microphysical parametrisation Complexity vs. Efficiency Operational Unified Model Wilson and Ballard (1999) “Cloud Resolving” Models Enhanced Microphysics

9 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright Blending Height Surface MOSES II Treats heterogeneous surfaces using ‘blending height’ techniques and tiles. Surface exchange from each surface type treated separately Nine surface types, –Broad Leaf Trees –Needle Leaf Trees –C3 Grass –C4 Grass –Shrub –Urban –Water –Soil –Ice Each tile has fixed characteristics. 4 layer soil temperature and moisture.

10 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright  s  T s 4  g  T g 4 H E  s  T s 4 G RNRN Tiles surface exchange Each tile has a full surface energy balance. This includes a radiatively coupled ‘canopy’. In the urban case this has high thermal inertia to simulate wall effects. Work in progress (Harman, Belcher, Best) to improve urban representaion.

11 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright Boundary Layer Scheme First order, moist Allows for non-local mixing in unstable regimes (top down/bottom up) Scheme diagnoses 6 different mixing regimes in order to represent stable, well mixed and cumulus and stratocumulus processes Scheme includes boundary layer top entrainment parametrisation. Especially well suited for strato- cumulus. Improved interaction with the convection scheme New non-local stable scheme

12 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright NWP Model Domains Research Configuration HorizontalVertical (lowest km)

13 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright NWP Model Orography 12 km4 km1 km

14 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright Single Column Unified Model 1D column version with full physics Choice of forcing –Observational –Statistical –Fixed

15 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright Site Specific Forecast Model 1D (semi-)automated model based on UM “physics” - full column Greatly increased resolution in BL & soil “Dynamics”=“Forcing data”: grad p, advection, etc. Simple forcing correction for orography MOSES with tile surface exchange for separate treatment of land use types Radiative canopy coupled to surface exchange Upwind satellite derived land-use determines drag & surface fluxes of heat, moisture Surface landuse weighting via a stability dependent Source Area Model

16 Rachel Capon 04/2004 © Crown copyright NIMROD Nowcasting System Rod Brown, Stephen Moseley Input – radar + satellite data – SYNOPS – Mesoscale model forecasts – Sferics Output includes Visibility, T, Td, total water, liquid water temp, fog probability (200m, 1km, 5km), relative humidity

17 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright Visibility Analysis Visibility Analysis Model T and T d Satellite data Model Aerosol concentration Synops

18 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright Visibility Forecast Initial analysis from satellite data and SYNOPs Trends in liquid water temperature and total mixing ratio from the Mesoscale model are applied to the analysis to produce an extrapolation forecast Forecast values are merged with the model and persistence values Visibility is diagnosed using the model aerosol concentration

19 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright Visibility Analysis

20 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright T+3 Forecast Analysis

21 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright

22 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright Temperature and Dew Point Forecasts

23 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright Probabilistic Visibility Forecast The probability of the visibility being less than 200 m, 1 km, 5 km is also forecast A triangular distribution of qt is assumed about the forecast (median) value qt qt threshold qt median

24 Rachel Capon COST 722 Paris 25/06/2004 © Crown copyright T+1 F/C Probability of Visibility < 5 km