The Sensitivity of a Real-Time Four-Dimensional Data Assimilation Procedure to Weather Research and Forecast Model Simulations: A Case Study - PowerPoint PPT Presentation

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The Sensitivity of a Real-Time Four-Dimensional Data Assimilation Procedure to Weather Research and Forecast Model Simulations: A Case Study

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The Sensitivity of a Real-Time Four-Dimensional Data Assimilation Procedure to Weather Research and Forecast Model Simulations: A Case Study Hsiao-ming Hsu and Yubao Liu – PowerPoint PPT presentation

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Title: The Sensitivity of a Real-Time Four-Dimensional Data Assimilation Procedure to Weather Research and Forecast Model Simulations: A Case Study


1
The Sensitivity of a Real-Time Four-Dimensional
Data Assimilation Procedure to Weather Research
and Forecast Model Simulations A Case Study
  • Hsiao-ming Hsu and Yubao Liu
  • NCAR/RAP

2
  • Motivations
  • WRF real-case initialization schemes
  • SI interpolation from other models
  • 3DVAR hopeful, but 3D, simplified balance
  • 4DVAR bright future
  • Hereby, we look into a method to initialize WRF
    with a four-dimensional dynamically and
    physically consistent analysis, which
    incorporates all available synoptic and asynoptic
    observations.
  • NCAR/ATEC MM5-based RT-FDDA system provides this
    kind of analysis to initialize WRF forecast.

3
NCAR/ATEC RTFDDA
  • Built around MM5 (Jennifer et al. 2001, Liu et
    al. 2002)
  • Continuous observation nudging (Stauffer and
    Seaman 1994)
  • Multi-grids (1 km fine meshes)
  • 3 hourly-cycling
  • Operated at 5 ATEC ranges and support several
    special tasks (CO-fire, Olympics)

Coldstart
t
FDDA
Forecasts
Day N
Day 0
4
(No Transcript)
5
CASE
During Year-2002 Winter Olympics at SLC, RTFDDA
was operational for 2 months. There was a snow
storm event during March 13. A pair of contrast
experiments of 12-hr WRF forecasts with different
initial conditions were conducted, started at
00Z, March 13.
6
Experiment Design
  • EXP1- Cold start WRF
  • WRF initial condition was generated by
    re-analysis of ETA forecast with available
    observations at 00Z, March 13.
  • EXP2 - Warm start WRF
  • WRF initial condition was obtained from the
    RTFDDA analysis which had been running
    continuously from a cold start 84 hours ago.
  • EXP3 - Warm start MM5
  • Same as EXP2, but with MM5
  • (from op-RTFDDA).

7
Domain configuration
  • 82 x 70
  • dx 36 km
  • 36 layers
  • 12 levels in 1 km AGL
  • Coarse mesh only

8
Hourly Precipitation of 1 12 Forecasts
Cold start
Warm start
9
Subjective verification of 1 hour precipitation
at 3-h forecast
A
A
C
C
B
B
Warm start
Cold start
C
A
B
C
B
OBS IR
OBS Radar
10
(No Transcript)
11
WRF Forecast at 03Z
RTFDDA forecast at 03Z
12
Summary
  • Significant differences were observed between the
    cold start and the warm start WRF forecasts.
  • The warm-start WRF run compares more favorable
    to observations.
  • The Warm start WRF results are very similar to
    those from RTFDDA (MM5) during the first few
    fours of forecasts.
  • It is evident that reasonable benefit of reduced
    dynamical and cloud/precipitation spin-up
    during first few hours can be obtained by
    interfacing MM5 RTFDDA process to WRF
    initialization.

13
Future Work
  • Comparison study on higher resolutions and severe
    weather cases.
  • Ingesting RTFDDA cloud/precipitation analyses
    into warm start WRF.
  • Implement warm start WRF in the same
    operational environment of RTFDDA MM5
  • Quantitative verification of warm-start WRF
    against various observations for a longer-term
    parallel tests with MM5.
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