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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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