Evaluation of Potential Impacts of Doppler Lidar Wind Measurements on High-impact Weather Forecasting:
A Regional OSSE Study
Zhaoxia Pu and Lei ZhangUniversity of Utah
Collaborate withBruce Gentry NASA GSFC
Belay Demoz Howard University
Acknowledgements: Michiko Masutani, EMC/NCEP, Joint OSSEs
Las Peter Riishojgaard, JCSDARobert Atlas, NOAA/AMOL
NASA/HQ 13th IOAS-AOLS
89th AMS Annual Meeting, Phoenix, AZJanuary 15, 2009
About this talk
• Observing system simulation experiments (OSSEs) with Doppler Wind Lidar (DWL) measurements
• Problems and challenges in regional OSSEs
Backgorund
“Tropospheric winds are the number one unmet measurement for improving weather forecasts.”
-- National Research Council
• NASA has supported a “Lidar wind science” program to help develop next generation space-based Doppler Wind Lidar (DWL) measurements.
• It is expected that the future DWL will provide much denser (high horizontal and vertical resolution) wind profile observations than the currently available rawinsonde networks
• It has also been well recognized that the future DWL should be operated in adaptive observation mode in order to save power resources.
General concept of OSSEs
(Courtesy of R. Atlas 2008)
Previous OSSEs with Doppler Lidar Wind (DLW)
• Liu and Kalnay (2007), adaptive targeting strategies (simple global model)• R. Atlats et al. (2008), Impact of DLW on hurricane track forecast (NASA global model)• M. Masutani (2008), Evaluation of the impact of DLW with NCEP GFS• D. Emmitt (2008), Various experiments with DLW
The objective of OSSEs
• Access the impact of the data from future instruments • Define minimum requirements for future instruments in order to meet a certain goals in weather/climate prediction.
• Most of previous OSSEs have been done with global models• Impact of DLW data on high-impact weather system (e.g. hurricane) has been examined ( Atlas et al. 2008; Emmitt et al. 2008). Positive impact has been shown on hurricane track forecast.
Issues and Research Objectives
• For these high-impact weather systems, we not only care about their track, but are also concerned about their intensity and structures
For instance • Hurricane intensity forecast remains a challenging problem (Roger et al. 2006)
Then:
To what extent can next generation DLW observing system improve the hurricane intensity forecast?
Do ECMWF global natural runs represent hurricane structure?
Case: 00UTC October 1 2005 – 00UTC October 4, 2005
SLP
Track
3-h rainfall (T511)
Tropical cyclones were found to be reasonably well represented in the Natural Run for a model of intermediate resolution.
Due to the relatively low resolution of the Natural Run in comparison with the scale of the storm inner core structure, the data may only be useful for the OSSEs that focus on tropical cyclone track forecasting rather than intensity forecasting.
Are ECMWF natural runs adequate for verification purposes?
3-h rainfallT511
WRF 9-km
WRF 3-km
Regional OSSEs
Regional Natural Run: Regional numerical simulation with Advanced Research Version of Weather Research and Forecasting (WRF) model Nested inside of ECMWF T799 natural run Resolution: 27km, 9km and 3km Physics option: BMJ cumulus, LIN microphysics, MYJ PBL
Simulation of the data (25-km resolution)
CTRL run: WRF simulation nested inside of T511
Resolution: 27km, 9km and 3kmPhysics option: KF cumulus, WSM6 microphysics, YSU PBL
Data Assimilation : WRF 3DVAR
Verification
Data Impact
Regional OSSE results
Regional OSSE results
3-h precipitation at 48 h fcst
CTRL Exp Truth
Regional OSSE results
Minimum central SLP Maximum surface wind
Some issues with regional OSSEs
Forecast is very sensitive to physicsParameterization options
Can be good or bad
Some issues with regional OSSEs
Exp.1 T799 IC and T799 BCExp.2 T799IC and FNL BC
Some issues with regional OSSEs
Forecast is very sensitive to the boundary conditions
Concluding remarks
• Future DLW measurements could be a very useful data source for improving the forecast of high-impact weather systems (e.g., hurricane)
• More work needs to be done to explore the instrument strategies In order to improve the intensity forecast
• There are some issues (such as the impact of model physics, boundary conditions, and resolution) that need to be studied carefully with regional OSSEs in order to make a realistic assessment of the impact.
• The study is ongoing…