Observing System Simulation Experiments for

COSMIC-IIUCAR COSMIC Team

FORMOSAT-3/COSMIC Follow-on Mission Planning

• NSC/NSPO and NOAA are discussing a possible collaboration on the FORMOSAT-3 Follow-On Mission, which is called “COSMIC-II.”

• Preliminary design calls for 12 low-Earth orbiting satellites, each carrying an advanced receiver to track thee navigation systems, including GPS, GALILEO, and GLONASS.

• Observing system simulation experiments (OSSE) are useful to assess the potential impacts of the COSMIC-II mission, and to assist in constellation design.

Three Key Questions:

• What are the potential impacts of FORMOSAT-3 Follow-on on the prediction of typhoons in the vicinity of Taiwan?

• What is the optimal design of the Follow-on Mission? [This needs to be looked at from global, regional weather prediction, climate, and space weather perspectives.]

• What are the relative performance of FORMOSAT-3 Follow-on compared with the existing FORMOSAT-3 mission?

Two Possible Configurations

• Option A: – 8 satellites placed at 72 degree inclination angle– 4 satellites placed at 24 degree inclination angle

• Option B:– 12 satellites placed at 72 degree inclination angle

Distribution of RO soundings in a day

FORMOSAT-3/COSMIC COSMIC-IIA COSMIC-IIBG A B

Different color shows availability of RO soundings at different hours of the day.

COSMIC - 6 x 72o

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

COSMIC-IIB - 12 x 72o

Data Density for FORMOSAT-3, COSMIC-IIA, COSMIC-IIB

COSMIC-IIA Provides a much more even data density around the globe.Enhanced data density over the tropics is important for typhoon prediction.

Selected Case: Typhoon Shanshan (2006)

• Min. pressure of 920 hPa on Sep 15, 2006

Nature Run from MM5 with ECMWF Initial condition

• Typhoon track recurvature was reproduced• The track is close to the best track• Note that no official intensity observation is available

Forecast Experiment Design

• WRF-Var (3D-Var) /WRF with GFS IC and LBC– B.E.: generated from one month forecast

of September, 2006 (NMC)– 169 x 157 x 38, ptop = 10 hPa– Assimilation performed on 36-km grid,

1hr update cycle, over two-day period.

Convention Data Are Assimilated As Well

• Upper Air sounding (SOUND)• Observation (SYNOP)• Satellite Cloud track Wind (SATOB)• The horizontal and temporal distribution of these data are

consistent with actual observations (location/time, and with realistic errors )

Synop SOUND upper air Satellite wind (SATOB)

Simulated RO Refractivity Data

• For GPSRO refractivity, the observation errors vary with height and latitude (Chen and Kuo, 2005).

• RO soundings are simulated from the nature run as local value, no ray tracing simulation.

GPS OBS_ERR Based on Chen-Kuo

0

4

8

12

16

20

0 0.5 1 1.5 2 2.5 3 %N

KM obs_err_new lat 0 lat 90

Percentage of GPS Ref observations

Equator

pole

Height

Intensity Forecast

• Intensity Forecast Performance: C+A > C+B > C+G > C

C+G

C+A

C+B

C

Nature

Intensity Forecast Improvement against control (conventional data) forecast

• FORMOSAT-3 only shows modest improvement over Control.• COSMIC-IIA shows significant improvements over control.• COSMIC-IIA is superior to COSMIC-IIB

Percentage of improvement of intensity forecast

Percent Improvement relative to the control:

P.I. = (Error of Exp. C minus Error of Exp. X)/Error of Exp. C

Track Forecast Errors

• Performance: C+A > C+B > C+G > C

C+G

C+A

C+B

C

Track Forecast ErrorsImprovement against control (conventional data) forecast

Percentage of improvement of track forecast

• FORMOSAT-3 only shows visible improvement over Control.• COSMIC-IIA shows significant improvements over control.• COSMIC-IIA is superior to COSMIC-IIB

6 hour Integrated Precipitation Forecast

No precipitation system was developed in C, C+G, and C+B, only C+A

C+G C+A C+BN C

6 hour Integrated Precipitation (cont’d)

• Precipitation in C+A is much closer to that in nature run

C+G C+A C+BN C

6 hour Integrated Precipitation (cont’d)

• Late development of precipitation in C, C+G, and C+B, but in wrong locations

C+G C+A C+BN C

6 hour Integrated Precipitation (cont’d)

• All precipitation is stronger, but C+A still show better location

C+G C+A C+BN C

Summary and Conclusions

• COSMIC-IIA gives a much more uniform data distribution globally, compared with COSMIC-IIB.

• Data density is important for typhoon prediction:– FORMOSAT-3: < 1 over 500 km x 500 km– COSMIC-IIA: > 8 over 500 km x 500 km– COSMIC-IIB: < 4 over 500 km x 500 km

Typhoon Forecast Improvements• We perform two-day data assimilation, followed

with three-day forecast for FORMOSAT-3, COSMIC-IIA, and COSMIC-IIB.

• Compared with the Control (without RO data) COSMIC-II gives far superior results.

Intensity forecast Track forecast

FORMOSAT-3 8.1 25.0

COSMIC-IIA 43.3 79.1

COSMIC-IIB 26.0 39.5

Summary and Conclusions• COSMIC-IIA also gives significantly better

precipitation forecasts, in terms of rainfall intensity and distribution.

• The Option A design will greatly benefit the prediction of severe weather events over the Taiwan area, including typhoon, Mei-Yu, and mesoscale convective systems.

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

Intensity Forecast

Track Forecast Errors

Intensity Forecast Improvement against control (conventional data) forecast

• Intensity: C+D ~ C+C ~ C+A > C+B > C+G > (C) in evident

Percentage of improvement of intensity forecast

Track Forecast ErrorsImprovement against control (conventional data) forecast

• Track forecast: C+A ~ C+D > C+C > C+B > C+G > (C) in evident

Percentage of improvement of track forecast

6 hour Integrated Precipitation

2A: 8x72 + 4x24, 2B: 12x72 + 0x24, 2C: 6x72 + 6x24, 2D: 4x72 + 8x24

C+G C+A C+BN C+C C+D

Future Work• Additional cases that affect Taiwan area:

– Sinlaku (2008), Jangmi (2008), and other T-PARC and U.S. cases– Mei-Yu convective systems and heavy rainfall events

• More realistic simulation of observations:– Ray tracing simulation of RO observations– Take into account available ground stations, and data latency

• Use different data assimilation systems:– Global and Regional NCEP GSI system– WRF/DART ensemble data assimilation system

• Collaborate with NCEP and ECMWF on global OSSEs and observing system experiments (OSE).

The COSMIC Team

Bill Kuo: P.I. on OSSE StudyTed Iwabuchi: WRF-3D-Var and ForecastBill Schreiner: Mission simulationZaizhong Ma: Observation simulationsTae-Kwon Wee:Nature runYong-Run Guo: WRF-Var and Obs. Simulation

This work is funded by Dr. Jay Fein at NSF.