Defence School of Languages, UK BILC Professional Seminar for NATO/PfP countries Monterey, USA 2011.
FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years...
Transcript of FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years...
![Page 1: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/1.jpg)
1
![Page 2: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/2.jpg)
2
FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION
Roger Daley
Naval Research Laboratory,Monterey CA, USA
Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical weather prediction. The situation is very different today. Data assimilation is now felt to be important for all climate/environmental monitoring and estimating the ocean state. There have been great advances in both modelling and instrumentation for a variety of atmospheric phenomena and variables, and data assimilation provides the bridge between them….
![Page 3: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/3.jpg)
3
Observations, assimilation and the improvement of global weather prediction
Some results from operational forecasting and ERA-40
Adrian Simmons(with thanks to the ERA-40 team, Tony Hollingsworth, …..)
![Page 4: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/4.jpg)
4
Contents
• Introduction to data assimilation
• ERA-40- evolution of the observing system since 1957- evolution of data fits and analysis increments- evolution of forecast accuracy
• Recent improvements in operational forecasts
• Inferences from forecast differences- between two operational systems- between successive forecasts
• Predictability as a function of horizontal scale
![Page 5: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/5.jpg)
5
Radiosondes Pilots and profilers Aircraft
Synops and ships Buoys
ATOVS Satobs Geo radiances
ScatterometerSSM/I Ozone
Data coverage09 – 15 UTC5 September 2003
![Page 6: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/6.jpg)
6
Data Assimilation
Six-hourly 3D analysis
![Page 7: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/7.jpg)
7
Mean-square 500hPa height increments
Units: (dam)2
(06UTC – 12UTC)
ERA-40 3D-Var for 2001
Background forecast Analysis
9.19 0.47
0.505.03
![Page 8: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/8.jpg)
8
Four Dimensional variational data assimilation(4D-Var)
![Page 9: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/9.jpg)
9
ERA-40 (www.ecmwf.int/research/era)
• A re-analysis from September 1957 to August 2002
• Based on cycle 23r4 of ECMWF forecasting system - operational from June 2001 to January 2002
• Six-hourly 3D-Var analysis- operations uses 12-hourly 4D-Var
• T159 horizontal resolution (~125km grid) - operations uses T511 (~39km grid)
![Page 10: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/10.jpg)
10
ERA-40
• Produced with considerable external support:- Most of the older observations were supplied by NCAR via NCEP- EUMETSAT supplied reprocessed satellite winds- SST and sea-ice analyses were produced by the Met Office and NCEP- Validation partners provided valuable feedback- Practical support from EU, Fujitsu, IAP, JMA, PCMDI, WCRP, GCOS …
• Production was completed in April 2003
• Full set of products is available from ECMWF MARS
• Products are (or will be) available from some national data centres
• 2.5o products are available on a public data server (http://data.ecmwf.int/data)
![Page 11: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/11.jpg)
11
Radiosonde coverage for March 1958
45478 reports
Average number of soundings per day:
![Page 12: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/12.jpg)
12
Radiosonde coverage for March 1997
36312 reports
Average number of soundings per day:
![Page 13: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/13.jpg)
13
Counts of observations accepted by ERA-40 system
AIRCRAFT
SATELLITE WINDS
SATELLITE RADIANCES
1
1E3
1E6
BUOYS
1973 1979
1960 1970 1980 1990 2000
![Page 14: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/14.jpg)
14
R.m.s. 500hPa height increment (m) at 12UTC from ERA-40
RMS(AN-BG)
AN=analysis
BG=6h background forecast
![Page 15: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/15.jpg)
15
24-hour 12UTC forecast errorvssondes
R.m.s. 500hPa height increment (m) at 12UTC
![Page 16: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/16.jpg)
16
Use of SYNOP surface pressure observations over the extratropical southern hemisphere in ERA-40
Number of observations used per day
OB-BG OB-AN4
2
800
400
1960 1970 1980 1990 2000
1960 1970 1980 1990 2000
1973 1979
R.m.s background and analysis fits (hPa)
1200
![Page 17: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/17.jpg)
17
Anomaly correlations of 500hPa height forecasts
Ops 1980Ops 1980Ops 2001
ERA 2001
Ops 1980Ops 2001
Ops 2002/3
ERA 2001
Northern Hemisphere
%
![Page 18: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/18.jpg)
18
Anomaly correlations of 500hPa height forecasts
Ops 1980
Ops 2002/3
Ops 2001ERA 2001
Australia/New Zealand
%
![Page 19: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/19.jpg)
19
Recent improvement in the accuracy of forecasts
Annual-mean r.m.s. errors against analyses from WMO scores500hPa height (m) Northern hemisphere
D+3
D+4
D+5
![Page 20: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/20.jpg)
20
Annual-mean r.m.s. errors against analyses from WMO scores
N Hem 500hPa (m)
D+3
D+4
D+5
S Hem 500hPa (m)
D+5
D+3
D+4
N Hem Pmsl (hPa)
D+5
D+3
D+4
S Hem Pmsl (hPa)
D+5
D+3
D+4
4D-Var
Model, analysis and data changes
Higher resolution
![Page 21: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/21.jpg)
21
Annual-mean r.m.s. errors against radiosondes from WMO scores
N Hem 500hPa (m)
D+3
D+4
D+5
S Hem 850hPa wind (m/s)
S Hem 500hPa (m)
D+5
D+3
D+4
D+5
D+3
D+4
New Jb formulation
N Hem 850hPa wind (m/s)
D+5
D+3
D+4
![Page 22: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/22.jpg)
22
Some aspects of the differences:
between ECMWF and Met Office analyses and forecasts
between successive ECMWF forecasts
![Page 23: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/23.jpg)
23
R.m.s. differences (m) between ECMWF andMet Office 500hPa height analyses
December – February
10.27.82002/03
11.510.12001/02
11.69.82000/01
16.312.21999/00
21.415.61998/99
21.214.11997/98
S HemN Hem
![Page 24: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/24.jpg)
24
Mean square difference between ECMWF and Met Office 500hPa height analyses
DJF 1997/98 DJF 2000/01 DJF 2002/03
m2
![Page 25: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/25.jpg)
25
R.m.s. differences (m) between ECMWF andMet Office 500hPa height analyses
June – August
10.75.52003
12.38.32002
14.28.22001
17.08.92000
27.410.31999
29.710.61998
S HemN Hem
![Page 26: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/26.jpg)
26
Mean square difference between ECMWF and Met Office 500hPa height analyses
JJA 2003DJF 2002/03
m2
![Page 27: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/27.jpg)
27
S HemN Hem
Correlation between ECMWF forecast errors and Met Office forecast errors
500hPa height DJF 2002/03
Implied r.m.s error of ECMWF analysis ~ 4 – 5m
![Page 28: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/28.jpg)
28
R.m.s. 500hPa height forecast errors (m)
Northern hemisphere Southern hemisphere
R.m.s ECMWF errorsR.m.s. Met Office errors
![Page 29: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/29.jpg)
29
R.m.s. 500hPa height forecast errors (m)
Northern hemisphere Southern hemisphere
R.m.s ECMWF errorsR.m.s. Met Office errorsR.m.s. ECMWF errors of 12-hour-old forecasts
![Page 30: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/30.jpg)
30
Tony Hollingsworth’s valediction:
Day
Forecast day on which a particular anomaly correlation is reached500hPa height Northern hemisphere Two-year running mean
Day
YearYear
![Page 31: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/31.jpg)
31
R.m.s. 500hPa height forecast errors (m)
Northern hemisphere Southern hemisphere
R.m.s ECMWF errorsR.m.s. Met Office errorsR.m.s. differences: ECMWF – Met Office
![Page 32: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/32.jpg)
32
R.m.s. 500hPa height forecast errors (m)
Northern hemisphere Southern hemisphere
R.m.s ECMWF errorsR.m.s. Met Office errorsR.m.s. differences: ECMWF – Met OfficeR.m.s. differences: ECMWF - (ECMWF - 12h)
![Page 33: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/33.jpg)
33
N Hem
S HemCorrelation between differences in 500hPa height forecasts and differences in verifying analyses(ECMWF – Met Office)
2,
22 2 ecefectruetruemeasured eCefffectrue+−=
For current measured forecast errors, and estimated analysis errors and correlations, the terms and tend to
cancel in short range, and are relatively small at longer ranges.ectrue efectrue Cef ,2− 2
ece+
Error of the verifying analysis contributes little to measured forecast error from 12h onwards:
![Page 34: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/34.jpg)
34
R.m.s. errors and differences between successive forecasts Northern hemisphere 500hPa height Winter
(D+5) – (D+4)“consistency”
(D+5) – (D+0)
![Page 35: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/35.jpg)
35
R.m.s. errors and differences between successive forecasts Northern hemisphere 500hPa height Winter
(D+5) – (D+4)“consistency”
(D+5) – (D+0)
![Page 36: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/36.jpg)
36
RMS differences between successive daily 500hPa height forecastsDecember-February Northern hemisphere
m
Assimilating model: T319 → T511Analysis resolution: T63 → T159
November 2000:
DJF 1999/2000: Underactive forecastsdue to stratospherichumidity analysisproblem
Day
![Page 37: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/37.jpg)
37
RMS differences between successive daily 500hPa height forecastsDecember-February Southern hemisphere
m
Day
![Page 38: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/38.jpg)
38
Spectra of mean-square day-1 500hPa height error variance
m2
Wavenumber
December - February
m2
December - February
m2
December - February
![Page 39: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/39.jpg)
39
Spectra of mean-square 850hPa temperature errors
K2
December 2002 – February 2003
Wavenumber
![Page 40: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/40.jpg)
40
Spectra of mean-square 850hPa temperature errors
K2
December 2002 – February 2003
Wavenumber
![Page 41: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/41.jpg)
41
Spectra of mean-square 850hPa vorticity errors
10-12s-2
December 2002 – February 2003
Wavenumber
![Page 42: FUNDAMENTALS OF ATMOSPHERIC DATA ASSIMILATION Monterey CA, USA · Monterey CA, USA Fifteen years ago, data assimilation was a minor and often neglected sub-discipline of numerical](https://reader033.fdocuments.us/reader033/viewer/2022043000/5f7754e18f85234e5218d025/html5/thumbnails/42.jpg)
42
In summary:• There has been a clear long-term improvement in the
observing system – especially for the southern hemisphere.
• There has been a substantial improvement in forecasts over the past seven years – especially arising from improved data assimilation (improved models as well as improved analysis techniques) and better observations.
• There has been some significant convergence in the performance of different centres – but significant (and informative) differences remain.
• There has been a recent improvement in the handling of smaller scales – suggesting potential for further benefit from resolution increases.