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…