COSMIC Retreat 2008 Impact of COSMIC on typhoon prediction Bill Kuo and Ted Iwabuchi.

COSMIC Retreat 2008

Impact of COSMIC on typhoon prediction

Bill Kuo and Ted Iwabuchi

Historical Typhoon Tracks

• Inter-annual variations of typhoon path and activity

• It’s clear that we need observation over the ocean

200429

200523

200623

200724

Typhoon Paths in 2008

• 17 typhoons in 2008 (by Oct 9)

Typhoon Landfalls in Taiwan in 2008

• Three typhoons have landfalled in Taiwan in 2008• How is relative importance of COSMIC data ?

Real-time Typhoon Forecast Design

• Cold 3DVAR: 6 hour DA time windows at 00 UTC• Cycling 3DVAR: 3 hour DA time window every 3 hours

from 00UTC for 24 hour time windows

Real-time Typhoon Forecast Design

• COSMIC + Conventional vs only Conventional (w/o COSMIC)• Cold 3DVAR vs Cycling 3DVAR • Conventional data (SYNOP, SHIP, BUOY, METAR, PILOT, SOUND,

AMDAR, SATEM, SATOB, GPSPW, AIREP, PROFL)

COSMIC Profile Availability

• COSMIC data is available continuously– Not like radiosonde data available only at 00 and 12Z

• Cycling 3DVAR for long data assimilation time window is one of the optimal assimilation scheme for COSMIC DA

22.5-1.5 1.5-4.5 4.5-7.5 7.5-10.5

10.5-13.5 13.5-16.5 16.5-19.5 19.5-22.5

22.5-1.5(+1d)

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DAtime window: 09-25_00Z - 09-26_00Z

Cold 3DVAR vs Cycling 3DVAR

• Significant improvement for track forecast in cycling 3DVAR

Cold 3DVAR Cycling 3DVAR

IC: 2008-09-25_00Z

Track Forecast Errors

• Cycling 3DVAR forecast is much better than cold 3DVAR forecast

• Forecast with COSMIC profile is better than that without COSMIC profile

Cold 3DVAR

Cycling 3DVARCOSMIC

IC: 2008-09-25_00Z

Intensity Forecast Comparison

• Gaps between best track from JMA and WRF forecast

• Trend of intensity changes is more similar in cycling 3DVAR forecast than those in cold 3DVAR forecast

Typhoon Real-time Forecast with COSMIC

• Real-time and continuous ingestion of COSMIC profile helped to forecast typhoon Jangmi

• We need more test case studies for statistical discussions

• We need to mprove intensity forecasts

Landfall of Jangmi to Taiwan

Cold 3DVAR vs Cycling 3DVAR

• Significant improvement for track forecast in cycling 3DVAR and COSMIC

IC: 2008-09-26_00Z

Cold 3DVAR Cycling 3DVAR

Track Forecast Errors

• Significant improvement for track forecast with COSMIC cycling DA

IC: 2008-09-26_00Z

Intensity Forecast Comparison

Cold 3DVAR vs Cycling 3DVAR

• Significant improvement for track forecast in cycling 3DVAR and COSMIC

IC: 2008-09-10_00Z

Cold 3DVAR Cycling 3DVAR

Track Forecast Errors

• Significant improvement for track forecast with COSMIC cycling DA

IC: 2008-09-10_00Z

Intensity Forecast Comparison

Summary and Discussions

• Cycling 3DVAR DA can get maximum benefit of COSMIC data– Not like radiosonde only at 00 and 12Z

• Positive impact for track forecast continue more than 3 days– Improvement of environment around typhoon path ?

• More COSMIC profile should be helpful for forecast of tropical cyclone

• More intensity is needed for short-tern forecast– Longer DA time window?

• Which is important: number of data or number of cycling ?

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