Reanalysis of the 20th Century
Gilbert P. Compo, Jeffrey S. Whitaker, and Prashant D. Sardeshmukh
Univ. of Colorado/CIRESClimate Diagnostics Center andNOAA Earth System Research Laboratory/PSD
Special thanks to N. Matsui, R. Vose, R. Allan, S. Woodruff
The 20th Century Reanalysis Project
Summary: An international collaborative project led by NOAA and CIRESto produce high-quality tropospheric reanalyses for the last 100 years using only surface observations.
The reanalyses will provide:-First-ever estimates of near-surface and tropospheric 6-hourly fields
extending back to the beginning of the 20th century; -Estimates of biases and uncertainties in the basic reanalyses;-Estimates of biases and uncertainties in derived quantities (storm tracks, etc.) Initial product will have higher quality in the Northern Hemisphere than in the Southern Hemisphere.
US Department of Energy INCITE computing award and NOAA Climate Program Office support to produce 1892-2007 by early 2009.
Initially produce 1908-1958.
Ensemble Filter Algorithmxj
b = <x>b + x’jb = first guess jth ensemble member ( j=1,…,56 )
yo = single observation with error variance R
First guess interpolated to observation location:<y>b = H <x>b , y’j
b = H x’jb
Form analysis ensemble xja = <x>a + x’j
a from
<x>a = <x>b + K ( yo - <y>b )
x’ja = x’j
b + M (-y’jb ) Note the different gain
K = j x’jb y’j
b (j y’j
b y’jb + R)-1 Kalman Gain
M = (1 + {R/(j y’j
b y’jb + R)} –1/2 )-1 K Modified Kalman Gain
shrinks the ensemble(1/(n-1)) is included in j
Analysis ensemble becomes first guess ensemble for next observation.Using 56 member Ensemble FilterT62 (about 2 degree), 28 level NCEP CFS03 modelHadISST monthly boundary conditions (Rayner et al. 2003)
International Surface Pressure Databank
All Union Research Institute of Hydrometeorological Information WDC
Atmospheric Reconstructions over the EarthAustralian Bureau of MeteorologyBritish Antarctic SurveyDanish Meteorological InstituteDeutscher WetterdienstEMULATEEnvironment CanadaETH-ZurichGCOS AOPC/OOPC Working Group on Surface PressureHong Kong ObservatoryICOADSInstituto Geofisico da Universidade do PortoJapanese Meteorological AgencyJersey Met Dept.KNMIMeteoFranceMeteorological and Hydrological Service, Croatia
National Center for Atmospheric ResearchNOAA Climate Database Modernization ProgramNOAA Earth System Research LaboratoryNOAA National Climatic Data CenterNOAA National Centers for Environmental PredictionNOAA Northeast Regional Climate Center at Cornell U.NOAA Midwest Regional Climate Center at UIUCNorwegian Meteorological InstituteOhio State U. – Byrd Polar Research CenterProudman Oceanographic LaboratorySIGN - Signatures of environmental change in the
observations of the Geophysical InstitutesSouth African Weather ServiceUK Met Office Hadley CentreU. of Colorado-CIRES/Climate Diagnostics CenterU. of East Anglia-Climatic Research UnitU. of Lisbon-Instituto Geofisico do Infante D. LuizU. of Lisbon- Instituto de MeteorologiaU. of Milan-IFGAU. Rovira i Virgili-CCRG
Subdaily observations assembled under GCOS AOPC/OOPC Working Group on Surface Pressure GCOS/WCRP Working Group on Observational Data Sets for Reanalysis NOAA NCDC, NOAA ESRL, and CU/CIRES: merging station data NOAA ESRL and NCAR (ICOADS): merging marine dataThank you to partners contributing observations:
Sea Level Pressure analyses for Tri-State Tornado Outbreak of 18 March 1925
(deadliest tornado in U.S. history)
Manual Analysis, courtesy C. DoswellEnsemble mean from Ensemble Filter (4 hPa interval, 1010 hPa thick)
NOTE!!! This analysis did not use ANYof the observations shown on the left.
Range of possibilities for Sea Level Pressure 18 March 1925 18Z using 14 (of 56) members
Ensemble of 56 possible realizations consistent with the observations
SLP 1 December 1918 500 hPa GPHSLP 1 December 1925 500 hPa GPHSLP 1 December 1935 500 hPa GPHSLP 1 December 1945 500 hPa GPH
Analysis Ensemble Mean and Spread on selected dates in the 1918-1945 reanalysis period
Contours- ensemble meanShading- blue: more uncertain, white: more certain
Sea Level Pressure 500 hPa Geopotential Height
Uncertainty estimate poleward of 20Nblue actual differencered expected difference
Nobs
Reanalysis skill is comparable to current Day-3 forecast skill !
Analyzed 500 mb Z compared with independent radiosonde obs (1935-1956)
* Assumes observation error of 20 m
Median Absolute Error = 22.4 mExpected Error = 21.5 m*
Analyzed Anomaly
Obs
erve
d A
nom
aly Correlation = 0.97
N = 7106
(courtesy S. Bronniman and A. Grant, ETH)
Day 3 Pattern Correlation September-October 2007 0.96 - 0.97
Day-3, Day-5, Day-7500 mb Z anomaly correlation forecast skill from NCEP and ECMWF (Sept-Oct 2007)
0.9
0.7
0.5
0.3
300 hPa Geopotential Height Verification using independent radiosonde observations (1935-1956)
(courtesy S. Bronniman and A. Grant, ETH)
N = 6619
Correlation = 0.94
* Assumes observation error of 35 m
Median Abs Error = 39 m
Expected Error = 37 m*
Summary• Accuracy: Mid-tropospheric NH fields about as accurate as current 3-day forecasts.
• Uses:
1. Effectively doubling the reanalysis record length 2. Climate model validation dataset for large-scale synoptic anomalies during extreme
periods, such as droughts (30’s, 50’s) and extreme tornado outbreaks.
3. Better understand events such as the 1920-1940’s Arctic warming.
• Timeline: 1908-1958 done, full 1892-present done by Spring 2009.
• Data Access: Will be freely available from NCAR, NOAA/ESRL and NOAA/NCDC.
1908-1958 in Fall 2008.
1892-2007 in Spring 2009.
• 1850-2007, Partnering with GCOS Working Group on Surface Pressure, GCOS/WCRP Working Group on Observational Datasets for Reanalysis, Atmospheric Circulation Reconstructions over the Earth, RECLAIM, NOAA/CDMP, many National and University surface pressure data recovery efforts.
• For status updates, email – [email protected],– [email protected], or [email protected]
Future plans with ACRE
• 2009-2011: Early to mid-19th Century Reanalysis (with DoE and NOAA support)
Version 3: mid-19th – 21st century would need all data by August 2010improved version of NCEP model at higher resolution
=> hurricanes, high impact phenomena?potentially available in 2012
Obstacles to Improving Reanalyses of the
19th to 21st Centuries• Model Error
– Need improved representation of errors and unresolved processes (stochastic parameterization)
• Petascale Computing power
– Need higher resolution for mesoscale extremes, e.g., hurricanes
• Additional observations needed – Millions of land and marine observations not yet recovered or
exchanged
– Working with partners in Met Services, Universities, and international initiatives such as ACRE, NOAA CDMP, GEOSS/GCOS, IEDRO, RECLAIM, WCRP, WMO DARE
ISPD only
ISPD plus HURDAT-derived pressure
Effect of HURDAT data on Sept 1938 “Long Island Express”
Any Skill Forecasting the Track?
using 56 ensemble members T254L64 (about 0.5 degree)
36 hour forecast verifying 21 Sept 1938 18Z
Summary• Accuracy: Mid-tropospheric NH fields about as accurate as current 3-day forecasts.
• Uses:
1. Effectively doubling the reanalysis record length 2. Climate model validation dataset for large-scale synoptic anomalies during extreme
periods, such as droughts (30’s, 50’s) and extreme tornado outbreaks.
3. Better understand events such as the 1920-1940’s Arctic warming.
• Timeline: 1908-1958 done, full 1892-present done by Spring 2009.
• Data Access: Will be freely available from NCAR, NOAA/ESRL and NOAA/NCDC.
1908-1958 in Spring 2008.
1892-2007 in Spring 2009.
• 1850-2007, Partnering with GCOS Working Group on Surface Pressure, GCOS/WCRP Working Group on Observational Datasets for Reanalysis, Atmospheric Circulation Reconstructions over the Earth (Rob Allan at the UK Hadley Centre), RECLAIM, NOAA/CDMP, many National and University surface pressure data recovery efforts.
• For status updates, email – [email protected],– [email protected], or [email protected]
Analysis Ensemble Mean and Spread on selected dates in the 1935-1945 reanalysis period
SLP 1 December 1935 500 hPa GPH
Contours- ensemble meanShading- blue: more uncertain, white: more certain
Sea Level Pressure 500 hPa Geopotential Height
SLP 1 December 1945 500 hPa GPH
Analysis Ensemble Mean and Spread on selected dates in the 1935-1945 reanalysis period
Contours- ensemble meanShading- blue: more uncertain, white: more certain
Sea Level Pressure 500 hPa Geopotential Height
T700 Verification - Independent Obs(courtesy S. Bronniman and A. Grant, ETH)
MAE = 1.59 KExpected Error = 1.73 K*
MAE = 1.58 KExpected Error = 1.71 K*
* Assumes observation error of 1.5 K
Anom Corr = 0.87 Anom Corr = 0.90
Uncertainty estimate poleward of 20Nblue actual differencered expected difference
Nobs
1918-1948: 24-h forecast skill
Nobs
Sea Level Pressure Analyses26 - 27 December 1947
US Weather Bureau Ensemble Filter
Intensity of East Coast Lowis weaker in Ensemble Filteranalyses, but major features arepresent.
(Kocin and Uccellini, 2004)
Contour interval is 4 hPain all panels and 1012 hPacontour is thickened.
L
L
L
Analyses of 500 hPa Geopotential Height 27 December 1947
Air Weather Serviceanalysis valid 0400GMTUsing only surface
pressure observations, Ensemble Filter analysis compares well with analyses using upper-air observations.
5500 m (18000 ft)contour is thickened
Ensemble Filter T62analysis valid 0600GMT
NCEP T2543 hr forecast valid 0600GMT
Using only surface pressure obs
Using all available surface and upper-air obs
Severe snowstorm casein New York City, USA.
RMS error of 6-hourly 500 mb Z analyses for Jan-Feb 2005
using ECWMF 3DVAR
and only Surface Pressure observations at 1930’s densities
ECWMFSystem Retuned foronly surface
pressure
ECWMF2005 T159L64 Courtesy J. Thepaut
Northern Hemisphere Analysis Error
ECWMF2005 T159L64 Courtesy J. Thepaut
Need system tailored for ClimateReanalyses
Northern Hemisphere Analysis Error
RMS error of 6-hourly 500 mb Z analyses for Jan-Feb 2005
using ECWMF 3DVAR, 4DVAR, NOAA/CIRES Ensemble Data Assimilation
and only Surface Pressure observations at 1930’s densities
ECWMFSystem Retuned foronly surface
pressure
Effect of HURDAT data at on Sept 1938 “Long Island Express”
No HURDAT data
Effect of HURDAT data on Sept 1938 “Long Island Express”
With HURDAT data
