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Status Report for WRF's Variational Data Assimilation System _WRF

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Status Report for WRF's Variational Data Assimilation System _WRF Powered By Docstoc
					 Initialization of Microphysical Fields with
Radar Reflectivity Assimilation in WRF-Var
    and its Implication in Cloud Analysis


                                    Qingnong Xiao

 University of South Florida, College of Marine Science
               Saint Petersburg, Fl 33701


  ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
Outline:
• Introduction
• Radar reflectivity data assimilation in WRF 3D-Var
• Experiments with an IHOP squall line case
    OSSEs (Observing System Simulation Experiments)
    Real data assimilation

• Preliminary results from cloudy radiance assimilation
• Summary and discussions


  ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
Introduction
• We started development of radar data assimilation in
  2002 with KMA project
• The developed schemes were based on MM5
  3DVAR initially, and transformed to WRF 3DVAR
  in 2005
• A warm rain process from MM5 was included in
  reflectivity assimilation algorithm
• The scheme went OSSE, real case study, and
  operational application

 ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
Radar reflectivity assimilation

• Control variable qt (qt=qv+qc+qr)
• Background error statistics (using qt instead
  of qv)
• A warm rain microphysics scheme to partition
  (balance) the hydrometeor increments and
  other increments (qv’, qc’, qr’  T’, p’)



 ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
Microphysics in WRF 3D-Var

A warm rain                                                                 qc
process is
                                                      PCON
currently built in                                                        PRA
WRF 3D-Var to                                 qv
                                                                          PRC
bridge increments                                        PRE
of water
hydrometeors                                                                qr
and other
variables                                          PCON: condensation/evaporation;
                                                   PRA: accretion; PRC: conversion;
                                                   PRE: evaporation/deposition
  ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
     Flow Chart of Reflectivity Assimilation
                in WRF 3D-Var




ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
Observation operators

• Reflectivity (Sun and Crook 1997)

               dbZ  43.1 17.5 log qr 




ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
        Experiments with an IHOP
             squall line case
•     OSSEs
•     Real-data experiments




ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
                                                              Surface analysis and
                                                              Composite radar reflectivity
                                                              observations at (a) 2100
                                                              UTC 12 and (b) 0000 UTC
                                                              13 June 2002.

                                                              The cold front (blue line), dry line
                                                              (brown line) and outflow boundary
                                                              (pink line) at 2100 UTC 12 June are
                                                              depicted in (a). The 12 red dots in
                                                              (b) indicate 12 WSR-88D radar
                                                              stations with their station name
                                                              above the red dot. The data from the
                                                              12 WSR-88D radars are used for the
                                                              Doppler radar data assimilation
                                                              experiments.




ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
OSSEs: Test of the Algorithm
•     In OSSEs, the truth and background error
      are known
•     We can evaluate the performance of the
      developed algorithm and compare with the
      truth.
•     This work is going to be published this
      year by Sugimuto et al. 2009 in Mon. Wea.
      Rev.

ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
Setup of OSSEs
 Simulations: Simulations with initial condition at 12Z as background
                                                     15Z as truth
 Assimilation: Observations are simulated from the truth experiment
                plus random error (with standard deviation of 1 dBZ, unbiased).
                The simulated observations are assimilated to the background
                and compared with the truth.

                           Time Table (June 12 - 13, 2002)

                                                                                             Bkg
          1200Z 1500Z                             2100Z           0000Z
                                                                                            Truth
                                                (6-hrs fcst)      (9-hrs fcst)
                                                        3dvar
                                                (9-hrs fcst)
                                                                       3dvar
                                                                 (12-hrs fcst)
     ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
Simulated observations
- Data within 200 km radius from
 each radar site
- Data from 25 radar sites (real
  WSR-88D sites)
- The simulated observation is calculated
 on each grid point without interpolation

- Observation error

    Reflectivity factor: 1 dBZ                                           WSR-88D network
                                                                     (Each circle indicates range of
                                                                     200 km from each radar site.)



     ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
            1-hour accumulated rainfall simulation

Truth




Bkg




Stage4



         ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
      Analysis of rain water mixing ratio
T-B                       A-B                          T-B                        A-B




T-B                       A-B




 ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
      Analysis of cloud water mixing ratio
T-B                       A-B                          T-B                        A-B




T-B                       A-B




 ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
       T-B                   A-B                      T-B                   A-B




       T-B                   A-B                      T-B                   A-B




                                                       Analysis of
                                                   potential temperature
ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
               1-hour accumulated rainfall forecast

Truth




Bkg




Da-run



         ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
                 Real Case Experiments
           (Xiao and Sun 2007 in Mon. Wea. Rev.)

21UTC 12       00UTC 13                       WRF Forecast                                      12UTC 13




               Doppler radar data DA
               at 21 UTC 12 and 00 UTC 13
WRF SI

• Domain of 400X400X28 grids, with grid-spacing of 4km
• WRF SI using eta data at 21 UTC 12 June 2002, WRF 3D-Var
  Doppler radar data assimilations at 21 UTC 12 and 00 UTC 13
  (3 hour cycling), 12-hr WRF forecast from the 3D-Var analysis
  at 00 UTC 13 to 12 UTC 13 June 2002.
    ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
CTRL                                     RADR

                                                                                       500 hPa
                                                                                       vertical
                                                                                       velocity


CTRL                                     RADR
                                                                                     700 hPa
                                                                                   reflectivity
                                                                                  and rainwater
                                                                                   increments



ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
CTRL                                     RADR

                                                                                       500 hPa
                                                                                       vertical
          OBS                                                                          velocity


CTRL                                     RADR
                                                                                     700 hPa
                                                                                   reflectivity
                                                                                  and rainwater
                                                                                   increments



ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
                                                                           QPF
                                                                           Verification

                                                                           Left panel:
                                                                           Impact of
                                                                           more temporal
                                                                           radar data

                                                                           Right panel:
                                                                           Impact of
                                                                           more spatial
                                                                           radar data

ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
        Assimilation of cloudy radiance
         with WRF 3D-Var: An OSSE
•      CRTM is used as the cloudy radiance observation
       operator for simulation and assimilation of SSMIS
       radiance data
•      Minimization starts from a cloud-free background
•      2 outer-loops with eps=0.01 for gradient converge
       criterion
•      Details can be seen in Liu 2009 (this workshop)



    ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
                                Analysis Vs. Truth
Column-Integrated cloud water        Column-Integrated rain water          Column-Integrated water vapor




           Truth                                 Truth                                  Truth

          Analysis                              Analysis                              Analysis




       ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009
    Summary and discussion
•   A warm rain process, its tangent linear and adjoint are implemented in WRF-Var. OSSEs
    indicate that it works and can extract some extend of cloud/rain information from cloud
    observations from radar reflectivity and cloudy radiance data.

•   However, the scheme in real case assimilation shows a different story. It sometimes works
    well, sometimes doesn’t work. High nonlinearity in the microphysics scheme (on-off switch)
    causes problems that, in case the background (first-guess) is under-saturated and too stable
    over cloudy area, the switch for microphysics may never turn on during minimization.
•   The warm rain microphysics is not enough for assimilation of cloud observations. Even it
    works, it put all the cloud information into rainwater or cloud water mixing ratio. Sometimes
    it produces unrealistic moisture or temperature increments.

•   In order to produce more reasonable cloud analysis, we need to improve the WRF-Var
    assimilation technique. In addition, more advanced, sophisticated microphysics, its linear
    and adjoint should be developed and included in the WRF-Var.

•   The WSM6 microphysics is one of the advanced microphysics scheme. It is a one-moment
    scheme with moderate complexity. Its tangent linear and adjoint are produced. It should be a
    good candidate.

         ACAPS kickoff meeting at National Center for Atmospheric Research, Boulder, Colorado on 09/02/2009

				
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