Impact of GPS Radio Occultation Data on Typhoon Prediction

Bill Kuo, UCARChing-Yuang Huang, NCU

Jing-Shan Hong, CWB

Impact of COSMIC on HurricaneErnesto (2006) Forecast

Without COSMICWith COSMIC

Impact of COSMIC on HurricaneErnesto (2006) Forecast

GOES ImageWith COSMIC

GOES Image from Tim Schmitt, SSEC

Verification of WRF/DART analysis by about 100 dropsondes during the Ernesto genesis stage.

See Hui Liu’s presentation later this morning, at 11:40 a.m.

Super Typhoon Jangmi (2008)

4-km WRF forecast experiments for the genesis of Typhoon Jangmi

- Start model at T = 3, 2.5, 2, and 1.5 days before the genesis- Use NCEP FNL as well as ECMWF I.C.- Mix FNL and ECMWF initial conditions by swapping moisture fields

- FNL u.v. T + ECMWF q- FNL q + ECMWF u, v, T

FNL initial conditions

T = -3 d

T = -1.5 d

T = -2.5 d

T = -2 d

ECMWF initial conditions

T = -2.5 d

T = -1.5 dT = -2 d

T = -3 d

FNLu, v, T, q

ECMWFu, v, T, q

FNL – u, v, TEC -- q

FNL - qEC – u, v, T

2-day forecast

OP2 run DFI

Evaluating the impact of COSMIC GPS RO data on the prediction of Typhoon Morakot, using the CWB 45-km operational WRF system (OP2) and the another system with digital filter, from 080318 – 080918 (a week long period).

Red: No GPS, Green: With GPS

OP2 run DFI

diff-=CTL-GPSPositive means improvement from assimilating GPSRO

GPS RO is shown to have an impact on typhoon track prediction, particularly, after 36-h. The impact is even more robust with the use of digital filter initialization.

24h forecast of 24-h accumulated rainfall (Aug 7-8)

NOGPS GPS

Ensemble Ensemble meanmean

ObservedObserved

Rain Probability Forecast (August 7-8 00Z)

Ensemble Ensemble meanmean

ObservedObserved

The spatial distribution of the simulated 3-h rainfall rate (colored shade, unit: mm) at 12/8-15/8 August. The associated sea level pressure (blue contours, unit: hPa) at the end of this period is superimposed. ---EN0600

c. 12/8-15/8 August (model simulation time 60-h~63-h) ---for EN0600

The rainfall probability distribution (%) exceeding the thresholds of (a) 500, (b) 1000 mm for 24-h rainfall ending at 0000 UTC 8 August; (c) 500, (d) 1000 mm for 24-h rainfall ending at 0000 UTC 9 August; (e) 1000, (f) 1500 mm for 48-h rainfall ending at 0000 UTC 9 August; (g) 1500, (h) 2500 mm for 96-h rainfall ending at 0000 UTC 10 August estimated from the 32 members of EN0600. The observed rainfall at the corresponding threshold is superimposed by the blue line.

a. The rainfall probability forecast

(a) D2500 mm D2

00/7-00/8

(b) D21000 mm

(c) D3500 mm

(d) D31000 mm

(e) 2Ds1000 mm

(f) 2Ds1500 mm

(g) 4Ds1500 mm

(h) 4Ds2500 mm

D300/8-00/9

4Ds00/6-00/10

2Ds00/7-00/9

Paper Lists:Chen, S.-Y., C.-Y. Huang, Y.-H. Kuo, Y.-R. Guo, and S. Sokolovskiy, 2009: Assimilation of GPS refractivity from FORMOSAT-3/COSMIC using a nonlocal operator with WRF 3DVAR and its impact on the pre diction of a typhoon event. Terr. Atmos. Ocean. Sci., 20, 133154. Kueh, M.-T., C.-Y. Huang, S.-Y. Chen, S.-H. Chen and C.-J. Wang, 2009: Impact of GPS radio occultation soundings on prediction of Typhoon Bilis (2006) landfalling Taiwan. Terr. Atmos. Oceanic Sci., 20, 115-131. Huang, C.-Y., Y.-H. Kuo, S.-Y. Chen, C.-T. Terng, F.-C. Chien, P.-L. Lin, M.-T. Kueh, S.-H. Chen, M.-J. Yang, C.-J. Wang, A. S. K. A. V. Prasad Rao, 2010: Impact of GPS radio occultation data assimilation on regional weather predictions. GPS Solutions, 14, 35-49.Chen, S.-Y., C.-Y. Huang, Y.-H. Kuo, and S. Sokolovskiy, 2010: Observational Error Estimation of FORMOSAT-3/COSMIC GPS Radio Occultation Data. Mon. Wea. Rev., accepted.

Taiwan GPS-ARC Team Works on GPS RO Data Impact on Typhoon Prediction

Experiment RO soundings

Mean Track Error

3 days* 24 48 72

None 0 102 56 123 141

GPS1 6 98 56 130 122

GPS2 11 97 70 136 98

GPS3 15 85 83 72 110* 3 days Mean Track Error : including the track error at the initial time

－ B － CWB Best Track－ N － None－ 1 － GPS1－ 2 － GPS2－ 3 － GPS3

莫拉克颱風(Morakot)

Data Density for COSMIC and COSMIC-II Options: A, B, C, and D

COSMIC - 6 x 72o

COSMIC-IIA - 8 x 72o + 4 x 24o

COSMIC-IIB - 12 x 72o

COSMIC-IIC - 6 x 72o + 6 x 24o

COSMIC-IIB - 4 x 72o + 8 x 24o

COSMIC-II SoundingsGeographic Coverage

(6@72°, 6@24°)

1 hour

6 hour

3 hour

24 hour

Summary• Analysis and prediction of tropical cyclogenesis is highly sensitive to

moisture distributions over the tropics.• GPS RO data provide valuable information on moisture that are important

to tropical cyclone prediction.• The assimilation methods and strategies have significant influence on the

impacts of GPS RO data on tropical cyclogenesis. Ensemble based data assimilation system performs better than 3D-Var. True for both global and regional weather prediction systems (e.g., WRF and NCEP GFS).

• Use of cloud-scale ensemble system, coupled with advanced data assimilation system can be very valuable for the prediction of disastrous event such as Morakot. GPS RO data help improve the precipitation forecast for this case.

Outlook

• Current COSMIC sounding distribution is NOT optimal for tropical prediction. We have the lowest data density over the tropics.

• Future mission (e.g., COSMIC-II) will substantially increase the data density over the tropics (factor of 10).

• UCAR, under sponsorship of NSF, will be conducting an OSSE study to examine the impact of COSMIC-II on Typhoon Morakot.