ECMWF by fionan

VIEWS: 19 PAGES: 18

									Some recent developments in the ECMWF
                model

          Mariano Hortal ECMWF
      Thanks to: A. Beljars (physics),
        E. Holm (humidity analysis)




             EWGLAM   Oct 2003           1
                       Noise in forecasts




H+12 from 26-09-2002 at 00z
                                           H+12 Z10 from 28-12-2002 at 12z




                       EWGLAM   Oct 2003                          2
Linear least square fit interpolation


                                                           x   x       x   x
                                                       X   x   x       x   x
                                  X
                                                                   x
                                                           x   x       x   x
                         X
                                              X            x   x       x   x




                         x         x           x       x
                        -1        0     I      1       2




                             EWGLAM         Oct 2003           3
SETTLS with LLSI at both departure and arrival in the vertical trajectory
                            computation




H+12 from 26-09-2002 at 00z                 H+12 Z10 from 28-12-2002 at 12z


                       EWGLAM      Oct 2003                          4
       Recent developments in the ECMWF
                     physics

   Radiation (aerosol climatology)
   Convection and clouds
   Clouds and boundary layer
   Land surface
   Simplified physics for linear and adjoint applications
   Orography (MAP reanalysis, turbulent orographic form
    drag)




                       EWGLAM   Oct 2003                     5
Radiation

   26R3:
       •Radiation on a separate grid to save costs (instead of 1 out
       of 4 points). In T511 model radiation is done on T255 grid.

        •New aerosol climatology

        •Post-processing of PAR and UV-B

   Under development:
       •RRTM short wave

        •McICA: Monte Carlo Independent Column Approximation to
        represent cloud overlap and inhomogeneous clouds by using
        different samples of the clouds in the different computational
        intervals (140 g-points in 16 spectral intervals)




                       EWGLAM      Oct 2003                  6
Convection and clouds

   26R3:
       •Clean-up of code and improved numerics leading to better
       representation of ice fallout

       •New cloud base/top algorithm based on entraining plume

       •Convection from any layer in lowest 300 hPa

       •Revised initiation of convection with perturbed parcels (in T
       and q) starting from mixed layer properties

       •Reduced water load in updrafts through more efficient
       microphysics

       •Increased entrainment




                      EWGLAM     Oct 2003                    7
      Convection and clouds
old                               ne
                                  w




         EWGLAM   Oct 2003    8
Convection and clouds




   EWGLAM   Oct 2003    9
Clouds and
boundary layer

 •A statistical
 cloud scheme
 based on variance
 of total water is
 under development

 •Moist boundary
 layer mixing
 scheme is nearly
 finished (better
 stratocumulus)




                     EWGLAM   Oct 2003   10
 Land surface

•Fully implicit tile coupling
with less noisy results for the
tiles with small fraction




           Tiles:
           •     Water
           •     Ice
           •     Wet skin
           •     Low vegetation
           •     Exposed snow
           •     High vegetation
           •     Snow under vegetation
           •     Bare soil

                               EWGLAM    Oct 2003   11
                 Land surface
•An Extended Kalman Filter (EKF) has been developed for soil moisture
analysis (as part of the EU project ELDAS).

•EKF can assimilate SYNOP-T/RH, Meteosat heating rates, and microwave
brightness temperatures

  Single column simulation for MUREX (France),
  1. Control with no data assimilation, 2. EKF with microwave Tb
  3. EKF with SYNOP T/RH, 4. EKF with surface heating rates




                           EWGLAM    Oct 2003                      12
 Physics in relation to data assimilation

•Linear and adjoint of radiation code has been developed and is currently
under test

•Simplified cloud and convection schemes have been developed for linear and
adjoint applications

•Experiments are under way to evaluate assimilation of microwave rain
products and brightness T in rainy areas via 1DVAR of TCWV which is
assimilated in 4DVAR

•TRMM precipitation radar is used for verification




                           EWGLAM    Oct 2003                    13
         Physics in relation to data assimilation

TRMM-
PR                                                   first
                                                     guess




assim.                                              assim.
of                                                  of
TMI-                                                TMI
rain                                                Tb
rate




                   EWGLAM   Oct 2003          14
  Orography: MAP                           TCWV from GPS 21-10-1999
  reanalysis

  • Reanalysis with all the additional
  MAP data is available




 TCWV from MAP                                  TCWV from operations
reanalysis, T511                               1999, T319




                             EWGLAM      Oct 2003                15
   New scheme for turbulent orographic form drag
    •Alternative to effective roughness length concept
    •Drag is distributed in vertical and implemented on model levels (Brown
    and Wood, 2003)
    •Scales between 5 km and 10 m are represented by this scheme
    •Universal orographic spectrum is assumed to account for scales smaller
    than 5 km
    •Standard deviation of orography at scales between about 10 to 2 km
    is used to drive the scheme (from 1 km data base)



Comparison of orographic drag and
turbulent surface drag (from
vegetation) from new scheme with
fine scale model results. Expressed
as drag coefficient versus terrain
slope.




                               EWGLAM   Oct 2003                  16
Nonlinearities in the humidity analysis

 Humidity is bounded from
  below (>0) and restricted
  close to saturation by
  condensation.
 Analysis increments behave
  asymmetrically at different
  levels of relative humidity.
 A new humidity analysis
  accounts for this through
  nonlinear flow-dependent
  change of variable,



                       rh
     rh* 
               ( p, 2 (rhan  rhbg ))
                     1




                               EWGLAM    Oct 2003   17
Some humidity analysis results

 With a better background
  error description, better use
  is made of humidity
  observations.
 An example is given by HIRS-
  12 humidity sensitive
  radiances.
 The new humidity analysis
  (bottom) has removed
  unrealistic outliers in the
  background error
  description.
 This results in better humidity
  forecasts.




                       EWGLAM       Oct 2003   18

								
To top