ERA-CLIM: Developing reanalyses of the coupled climate system

Transcription

1 ERA-CLIM: Developing reanalyses of the coupled climate system Dick Dee Acknowledgements: Reanalysis team and many others at ECMWF, ERA-CLIM project partners at Met Office, Météo France, EUMETSAT, Un. Bern, Un. Vienna, Un. Lisbon, RIHMI (Russia), Un. Pacífico (Chile). Special thanks to the Twentieth-Century Reanalysis Project, Compo et al.

2 For climate, different types of reanalyses are needed: Reanalyses of the modern observing period (~30 50 years): Produce the best state estimate at any given time Use as many observations as possible, including from satellites Closely tied to forecast system development (NWP and seasonal) Near real time product updates Extended climate reanalyses (~ years): Pioneered by NOAA CIRES 20 th Century Reanalysis Project Long perspective needed to assess current changes As far back as the instrumental record allows Focus on consistency, low frequency variability satellites Use only a restricted set of observations log(data count) surface upper air

3 ERA-CLIM EU collaborative research project, 9 institutions, Goal: Preparing input observations, model data, and data assimilation systems for a global atmospheric reanalysis of the 20 th century Main components: Data rescue (in situ upper air and satellite observations) Incremental development of new reanalysis products Use of reanalysis feedback to improve the data record Access to reanalysis data and observation quality information

4 Data rescue: Upper-air observations pre-1957 Pre 1930 Pre 1973

5 ERA-CLIM reanalysis products Atmospheric reanalysis for the 20 th century ( ) Using an ensemble of 10 plausible SST/sea ice evolutions Assimilating observations of surface pressure and marine wind 125/25 km global resolution, 91 vertical model levels ERA 20CM ERA 20C ERA 20CL Ensemble of model integrations (mainly monthly products) Assimilation of surface observations (3 hourly products) High resolution land surface (25km global) IFS Cy38r2 + CMIP5 data + HadISST v2.1 + ICOADS v ISPD v3.2.6 (incl. ERA CLIM) + CHTESSEL Final ERA 20C/M/L datasets (~200 Tb) are slowly becoming available at

6 Model data for ERA-20CM From , spatial resolution 125 km 10 members, using equally plausible SST/sea ice evolutions from HadISST2 Radiative forcing and land surface parameters as in CMIP5 Bias corrections used in HadISST2 ICOADS AVHRR ATSR

7 ERA-20CM global temperature anomalies 50 hpa 500 hpa 2 m

8 ERA-20CM land temperature anomalies vs CRUTEM4 ERA 20CM (ensemble mean) CRUTEM4 Agung El Chichón Pinatubo

9 ERA-20C: reanalysis of surface observations

10 3 February 1899 ERA-20C: A terrific storm at sea Published: February 16, 1899 Copyright The New York Times

11 What about trends? ERA 20CM model bias (temperature vs ERA Interim) + residual biases in observations + changes in observational coverage + changes in background error statistics => global mean temperature increments in ERA 20C:

12 20C global-mean temperature evolution ERA 20C slightly worse than ERA 20CM (relative to CRUTEM4) More warming than ERA Interim in lower troposphere (differences in model biases + SST data) Promising results from first experiment with ERA CLIM upper air observations (ERA Presat, )

13 ERA-20CL Meteorological forcing from ERA 20C (125km) Downscaling from 125km to 25km Run offline land surface model ERA 20CL (25km)

14 Spatial resolution and soil types T159 (~125 km) T799 (~25 km)

15 Verification against 2m-temperature observations Mean error [K] in diurnal cycle (ICOADS ) ERA 20CM (125km, no data assimilation) Scatter (all observations) Hour of day Reanalysis Observation

16 Verification against 2m-temperature observations Mean error [K] in diurnal cycle (ICOADS ) ERA 20CM (125km, no data assimilation) ERA 20C (125km, assimilating sfc pressure obs) Scatter (all observations) Hour of day Reanalysis Observation

17 Verification against 2m-temperature observations Mean error [K] in diurnal cycle (ICOADS ) ERA 20CM (125km, no data assimilation) ERA 20C (125km, assimilating sfc pressure obs) ERA 20CL (25km, improved land surface) Scatter (all observations) Hour of day Reanalysis Observation

18 ERA-CLIM2 EU collaborative research project, 16 institutions, Goal: Production of a consistent 20 th century Earth system reanalysis: atmosphere, land surface, ocean, sea ice, and the carbon cycle Main components: 1. Production of coupled reanalyses, for 20C and the modern era 2. Research and development in coupled data assimilation 3. Earth system observations for an extended climate reanalysis 4. Evaluation of uncertainties in observations and reanalyses

19 2 Coupled DA for climate reanalysis Motivation: To make better use of available observations The best SST products are still highly uncertain Daily variability is unrealistic pre 1980s Potential to get better energy budgets and fluxes HadISST2, used in ERA 20C ICOADS AVHRR ATSR

20 2 Coupled DA for climate reanalysis Motivation: To make better use of available observations The best SST products are still highly uncertain Daily variability is unrealistic pre 1980s Potential to get better energy budgets and fluxes HadISST2, used in ERA 20C ICOADS AVHRR ATSR

21 Implementation in ECMWF s IFS framework First prototype for coupled reanalysis (CERA): presentation by P. Laloyaux (Thursday 10:30, room 518 B C) IFS coupled with NEMO ocean model in 4D Var outer loop External SST/SIC product to constrain model bias NEMOVAR in inner loop

22 Final points Evaluation of ERA-20C/M/L is just beginning Several reports/papers are forthcoming Working hard to get the data to you! Key value of this work: unlocking observations for climate science Coupled Earth system reanalysis: a long-term project with many challenges Replacement of ERA-Interim: work in progress

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24 Plans for ERA-Interim replacement To start production end 2014 Based on IFS version CY40R3 Model resolution T511L91 (~40 km) 1979 present, hourly fields 8 years of model physics improvements FLAKE (treatment of unresolved lakes) and many other land surface model enhancements 10 member EDA at T255L91 (~80 km) 4D Var with 12h analysis window, T95/T159 inner loops Reprocessed / improved datasets: METEOSAT, GOES, and GMS AMV METEOSAT radiances AVHRR NOAA and METOP AMV ASCAT Sigma0 SSMI radiances (CM SAF) SBUV and TOMS ozone (NASA v8.6) NCAR upper air in situ observations Surface pressures (ISPD 3.2.6) Marine surface reports (ICOADS 2.5.1) +Various observation operator improvements: Microwave and infrared frequency shifts Time varying SSU cell pressure Time varying atmospheric CO2 concentration

25 ERA-20C small print Horizontal resolution T159 (approx. 125 km, as in ERA-40), 91 model levels up to 0.01 hpa Analysis increments at T95 (approx. 210 km) Model version IFS CY38R1, with added time-varying forcings: HadISST (sea-surface temperature and ice fraction), greenhouse gases (O3, CO2, CH4, N2O, CFC-11, CFC-12, CFC-22, CCL4), solar cycle, aerosols optical depth, as described in model-only integration documentation, ERA Report Series 16, Hersbach et al., Observations source: ISPD v3.2.6 and ICOADS v2.5.1 Two productions so far: a 10-member ensemble (~200 days in 2013) and a deterministic re-run (~50 days in 2014) Data assimilation method different from ECMWF NWP operations in 2013/14: 24-hour 4DVAR, 3-hourly output for analyses Ensemble updates of background error correlations and global variances every 10 days Deterministic uses constant (current) background error correlations, and global variances scaled to the ensemble Modulation of background errors in vorticity by daily maps of ensemble spread to reduce linear model instabilities Digital filtering of increments in vorticity and temperature activated Variational bias correction of surface pressure observations Using prior detection of time-series breaks based on SNHT homogeneity test using NOAA-CIRES 20CR departures Deterministic also includes detection and rejection of stationary observed time-series (quite a few in the 1990s ) Assimilation of marine surface wind observations from ICOADS2.5.1 Data produced in 6x 20-year streams for the ensemble, and 22x 5-year streams for the deterministic Data volume generated about 700 Tb for ensemble, 75 Tb for deterministic Model time-step of 60 minutes for ensemble, 30 minutes for deterministic ( better atmospheric tides) Only ensemble documentation available so far: ERA Report Series 14, Poli et al., Documents several issues found with ensemble production, all fixed in deterministic production Data currently being copied to a public data server for release