Transcript Recent Developments of Medium-Range EPS at JMA Haruki YAMAGUCHI*, Masakazu HIGAKI, and Masayuki KYOUDA Numerical Prediction Division, Japan Meteorological Agency, Tokyo, Japan The 4th.

Recent Developments of
Medium-Range EPS at JMA
Haruki YAMAGUCHI*, Masakazu HIGAKI, and Masayuki KYOUDA
Numerical Prediction Division, Japan Meteorological Agency, Tokyo, Japan
The 4th THORPEX-Asia Science Workshop (31 October 2012)
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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)
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Specification of medium-range EPS at JMA
One-week forecast
Typhoon forecast
EPS model and its
integration
Typhoon EPS
Forecast Domain
Horizontal Resolution
The whole Globe by using JMA’s AGCM, “GSM”
TL319 (~55km)
Vertical Levels
60 levels, up to 0.1 hPa
Ensemble Settings
Objectives
One-week EPS
Member
132 hours(00,06,12,18)
Forecast Hours
216 hours (12UTC)
Will be extended to 264 hours by next
March
Initial perturbation
Model ensemble
only when Tropical Cyclones of TS/STS/TY
intensity are present or are expected to
appear in the RSMC Tokyo –Typhoon
Centre’s area of responsibility
1 control run
and 50 perturbed runs
1 control run
and 10 perturbed runs
SV method,
Singular Vector (SV) method,
RSMC target (Fixed)
Three target areas
and
(NH,TR,SH)
Max. 3 Typhoon Target
(Movable)
Stochastic Physics
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 http://tigge.ecmwf.int/models.html
The 4th THORPEX-Asia Science Workshop (31 October 2012)
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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
Operation
One-week EPS
Horizontal
resolution
Vertical levels
Initial time
Ensemble size
Planned upgrades
Typhoon EPS
One- week EPS
Typhoon EPS
TL319 (~55km)
TL479 (~40km)
60 levels up to 0.1hPa
100 levels up to 0.01hPa
12UTC
00,06,12,18UTC
00,12UTC
51
11
27
The 4th THORPEX-Asia Science Workshop (31 October 2012)
Not changed
25
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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)
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Experiment A: Impact of enhancing
Horizontal resolution
One-week EPS
Operation
Experiment A
Horizontal resolution
TL319 (~55km)
TL479 (~40km)
Ensemble size
51 (27 when comparing to
experiment)
27
Initial time
12 UTC
12 UTC (00 UTC omitted)
Equivalent horizontal grid representing land around Japan
TL319
TL479
Better resolve Japan archipelago
The 4th THORPEX-Asia Science Workshop (31 October 2012)
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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
Surface wind speed [m/s]
Unperturbed member of the EPSs, initial time 27 AUG 2011 12UTC, FT 72 hr
Operation (TL319)
Experiment (TL479)
GSM (JMA’s highres TL959 forecast)
Analysis (For this case,
forecasts are too strong)
west-east section across the typhoon center
Sea level pressure [hPa]
Surface
wind speed [m/s]
TL319
TL479
TL959
deep
The 4th THORPEX-Asia Science Workshop (31 October 2012)
TL959
TL479
TL319
strong
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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
Precipitation [mm/24hr]
Unperturbed member of the EPSs, initial time 23 DEC 2011 12UTC, FT 72 hr
Operation (TL319)
Experiment (TL479)
GSM (JMA’s highres TL959 forecast)
The 4th THORPEX-Asia Science Workshop (31 October 2012)
Observation (For this case,
forecasts are too weak)
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Impact in precipitation probability
In some cases, there is a difference near border of orographic precipitation
Operation (TL319)
[%]
Probability of precipitation exceeding 1mm/24hr
DIFF(Experiment-Operation)
& Observation
[%]
Green dot (event occurred)
Black dot (not)
Experiment (TL479)
[%]
Initial time 2012/1/7 12UTC, FT144
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Verification of precipitation probability
• AMeDAS rain gauge observation on land across Japan, converted
0.5625deg x 0.5625deg verification grid, is compared with forecast
• Period: 2012 JAN 3 ~ FEB 3 12UTC
• Brier score of probability of precipitation exceeding 1mm/24hr
Operation(M27)
Operation(M51)
Experiment(M27)
Brier skill score
0.4
0.3
0.25
0.2
0.038
0.036
0.034
0.032
0.03
0.028
0.026
0.024
0.022
0.02
good
0
0.15
good
0.1
0.05
Experiment(M27)
Operation(M51)
Operation(M27)
24
48
72
96
120
144
Forecast time [hr]
168
48
72
96
120
144
Forecast
time [hr]
Operation(M51)
168
192
216
Experiment(M27)
Resolution term of Brier score
0.12
0
0
24
Operation(M27)
192
216
Brier score resolution term
Brier skill score
0.35
Brier score reliablity term
– Brier skill score is improved by improving both reliability and resolution term.
– Score of Experiment is also comparable or superior
to thatOperation(M51)
of 51-member
Operation
Operation(M27)
Experiment(M27)
Reliability term of Brier score
0.04
0.11
0.1
0.09
0.08
good
0.07
0.06
0.05
0
24
48
72
96
120
144
168
192
216
Forecast time [hr]
The 4th THORPEX-Asia Science Workshop (31 October 2012)
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Experiment B: Increasing ensemble size of
Typhoon EPS
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 area over RSMC Tokyo
Targeted areas around up to three typhoons
Typhoon EPS
Operation
Experiment B
Horizontal resolution
TL319 (~55km)
Not changed
Ensemble size
11
25
Initial time
00,06,12,18 UTC
Not changed
The 4th THORPEX-Asia Science Workshop (31 October 2012)
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Impact on increase of ensemble size
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 28th August 2011.
- Black lines and color lines indicate the best track and the forecast
tracks, respectively.
The 4th THORPEX-Asia Science Workshop (31 October 2012)
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Verification of strike probability
Reliability diagrams of strike probability that the center of a typhoon will pass within 120km
during the next five days
Verification target: Typhoon EPS operated initial times during 6 Jun 2012 00UTC ~ 5 Aug 00 UTC
Operation
(11 members)
Experiment
(25 members)
Reliability term is improved
The 4th THORPEX-Asia Science Workshop (31 October 2012)
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Close look to position error of track forecasts
Verification target: Typhoon EPS operated initial times during 6 Jun 2012 00UTC ~ 5 Aug 00 UTC
•
•
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
Position error of
ensemble mean
forecast is larger than
that of control run.
Need to tune amplitude
of initial perturbations.
The 4th THORPEX-Asia Science Workshop (31 October 2012)
For large position error
cases, larger spread is
desired.
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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)
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