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Recent Developments of Medium-Range EPS at JMA Haruki YAMAGUCHI*, Masakazu HIGAKI, and Masayuki KYOUDA Numerical Prediction Division, Japan Meteorological.

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Presentation on theme: "Recent Developments of Medium-Range EPS at JMA Haruki YAMAGUCHI*, Masakazu HIGAKI, and Masayuki KYOUDA Numerical Prediction Division, Japan Meteorological."— Presentation transcript:

1 Recent Developments of Medium-Range EPS at JMA Haruki YAMAGUCHI*, Masakazu HIGAKI, and Masayuki KYOUDA Numerical Prediction Division, Japan Meteorological Agency, Tokyo, Japan 1The 4th THORPEX-Asia Science Workshop (31 October 2012)

2 Outline Introduction of One-week EPS and Typhoon EPS of JMA Experiment A – Impact of enhancing horizontal resolution of forecast model in One-week EPS Experiment B – Impact of increasing ensemble size in typhoon track forecasts in Typhoon EPS Summary The 4th THORPEX-Asia Science Workshop (31 October 2012)2

3 Specification of medium-range EPS at JMA One-week EPSTyphoon EPS ObjectivesOne-week forecastTyphoon forecast EPS model and its integration Forecast DomainThe whole Globe by using JMAs AGCM, GSM Horizontal ResolutionT L 319 (~55km) Vertical Levels60 levels, up to 0.1 hPa Forecast Hours216 hours (12UTC) 132 hours(00,06,12,18) only when Tropical Cyclones of TS/STS/TY intensity are present or are expected to appear in the RSMC Tokyo –Typhoon Centres area of responsibility Ensemble Settings Member 1 control run and 50 perturbed runs 1 control run and 10 perturbed runs Initial perturbation Singular Vector (SV) method, Three target areas (NH,TR,SH) SV method, RSMC target (Fixed) and Max. 3 Typhoon Target (Movable) Model ensembleStochastic Physics 3 More detailed information is available at the JMA part of the latest WMO Technical Progress Report on GDPFS and NWP Research and the standardized EPS documentation in Excel spreadsheet format at The 4th THORPEX-Asia Science Workshop (31 October 2012) Will be extended to 264 hours by next March

4 Planned upgrades of the two EPSs Both EPSs: Enhancing forecast model – Apply several improvements in high-res deterministic forecast GSM, including increase of vertical levels – Increase horizontal resolution for better weather forecast in Japan One-week EPS: Increasing frequency of operation to two times in a day as almost retaining ensemble size per day to offer forecasters more fresh materials. Typhoon EPS: Almost doubling ensemble size to improve reliability of probabilistic typhoon track forecasts The 4th THORPEX-Asia Science Workshop (31 October 2012)4 OperationPlanned upgrades One-week EPSTyphoon EPSOne- week EPSTyphoon EPS Horizontal resolution TL319 (~55km)TL479 (~40km) Vertical levels60 levels up to 0.1hPa100 levels up to 0.01hPa Initial time12UTC00,06,12,18UTC00,12UTCNot changed Ensemble size

5 Experiments Planned changes are broken down into several small changes and have been examined by multiple experiments. Two of them are introduced. Experiment A Enhancing horizontal resolution of One-week EPS to examine impacts in – Reducing gap with high-res deterministic GSM – Better orographic effects Experiment B: Increasing ensemble size of Typhoon EPS to examine impacts in – Improving probabilistic typhoon track forecasts The 4th THORPEX-Asia Science Workshop (31 October 2012)5

6 Experiment A: Impact of enhancing Horizontal resolution The 4th THORPEX-Asia Science Workshop (31 October 2012)6 One-week EPSOperationExperiment A Horizontal resolutionTL319 (~55km)TL479 (~40km) Ensemble size51 (27 when comparing to experiment) 27 Initial time12 UTC12 UTC (00 UTC omitted) TL319 TL479 Equivalent horizontal grid representing land around Japan Better resolve Japan archipelago

7 Tropical cyclone Typhoons reproduced in the experiment tend to get closer to those of high-res GSM in the ways that: – The typhoons have deep center with strong wind near the center – Actually they are often too strong compared to analysis The 4th THORPEX-Asia Science Workshop (31 October 2012)7 Unperturbed member of the EPSs, initial time 27 AUG UTC, FT 72 hr Operation (TL319) Experiment (TL479) GSM (JMAs high- res TL959 forecast) Surface wind speed [m/s] west-east section across the typhoon center Sea level pressure [hPa]Surface wind speed [m/s] TL959 TL479 TL319TL959 TL479 TL319 deep strong Analysis (For this case, forecasts are too strong)

8 Winter monsoon Typical weather with winter monsoon – Upwind orographic precipitation and stripe precipitation pattern in Pacific Experiments shows finer precipitation pattern Not so obvious difference of upwind orographic precipitation between operation and experiment The 4th THORPEX-Asia Science Workshop (31 October 2012)8 Unperturbed member of the EPSs, initial time 23 DEC UTC, FT 72 hr Operation (TL319) Experiment (TL479) GSM (JMAs high- res TL959 forecast) Observation (For this case, forecasts are too weak) Precipitation [mm/24hr]

9 Impact in precipitation probability The 4th THORPEX-Asia Science Workshop (31 October 2012)9 Operation (TL319) Experiment (TL479) Initial time 2012/1/7 12UTC, FT144 Probability of precipitation exceeding 1mm/24hr DIFF(Experiment-Operation) & Observation [%] Green dot (event occurred) Black dot (not) In some cases, there is a difference near border of orographic precipitation

10 Verification of precipitation probability AMeDAS rain gauge observation on land across Japan, converted deg x deg verification grid, is compared with forecast Period: 2012 JAN 3 ~ FEB 3 12UTC Brier score of probability of precipitation exceeding 1mm/24hr – Brier skill score is improved by improving both reliability and resolution term. – Score of Experiment is also comparable or superior to that of 51-member Operation The 4th THORPEX-Asia Science Workshop (31 October 2012)10 Reliability term of Brier score Resolution term of Brier score Brier skill score

11 Experiment B: Increasing ensemble size of Typhoon EPS The 4th THORPEX-Asia Science Workshop (31 October 2012)11 Typhoon EPSOperationExperiment B Horizontal resolutionTL319 (~55km)Not changed Ensemble size1125 Initial time00,06,12,18 UTCNot changed Typhoon EPS has the following features: Identical forecast model with One-week EPS Specialized for Typhoon forecast in RSMC Tokyo Initial perturbations are composed of singular vectors targeted at RSMC Tokyo and around typhoons like the right figure High frequency operation (up to 4 per day) but with smaller ensemble size than One-week EPS Targeted areas around up to three typhoons Targeted area over RSMC Tokyo

12 Impact on increase of ensemble size 12 Operational EPS (11 members)Experiment (25 members) Ensemble TC tracks of Typhoon Talas up to 120 hours derived from the Typhoon EPS (left panel) and an experimental EPS (right panel). - Initial time is 12UTC 28 th August Black lines and color lines indicate the best track and the forecast tracks, respectively. The 4th THORPEX-Asia Science Workshop (31 October 2012)

13 Verification of strike probability 13 Verification target: Typhoon EPS operated initial times during 6 Jun UTC ~ 5 Aug 00 UTC Reliability term is improved 13The 4th THORPEX-Asia Science Workshop (31 October 2012) Reliability diagrams of strike probability that the center of a typhoon will pass within 120km during the next five days Operation (11 members) Operation (11 members) Experiment (25 members) Experiment (25 members)

14 Close look to position error of track forecasts There found no significant improvement of ensemble mean track forecasts between operation and experiment. Common difficulties in the both cases are found: – Too large ensemble spread during earlier forecast time, possibly be deteriorating ensemble mean – Spread seems not to be enough for large error cases during later forecast time 14 The 4th THORPEX-Asia Science Workshop (31 October 2012) Verification target: Typhoon EPS operated initial times during 6 Jun UTC ~ 5 Aug 00 UTC Position error of ensemble mean forecast is larger than that of control run. Need to tune amplitude of initial perturbations. For large position error cases, larger spread is desired.

15 Summary JMA prepares the next upgrade of its two EPSs. Two preliminary experiments are introduced. Results of the experiment enhancing horizontal resolution of One-week EPS – Expected tendency of resemblance to high-res GSM – The center of typhoons tend to be stronger though they often exceed analysis – Improvement of precipitation probability forecast in winter Results of the experiment increasing ensemble size of Typhoon EPS – Improvement of reliability of strike probability – Little impact in ensemble mean track forecast. – Regardless of ensemble size, there is a need to tune ensemble spread The 4th THORPEX-Asia Science Workshop (31 October 2012)15


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