ERA-Interim and ASR Data Management at NCAR

1. ERA-Interim and ASR Data Management at NCAR Steven Worley Dave Stepaniak Chi-Fan Shih February 17, 2009

2. ERA-Interim • Time Period, 1989-current • T255L60 4DVAR global, spectral or reduced Gaussian • Products • high resolution • reg. gaussian (512x256) • 37 press. lvls. (10001) • 15 isentropic surf. • 30 ocn. wave anal. fields • 47 surface anal. fields • Total size ≅ 84 TB (tapes) • Network Access ≅ 18 TB • Details • http://www.ecmwf.int/research/era/do/get/era-interim • http://dss.ucar.edu/datasets/ds627.0/ (to be here)

3. Information sources / documentation • Web pages • http://dss.ucar.edu/datasets/ds627.0/docs/

4. IFS @ ECMWF • Chapter 14 – Data Flow • difference between analysis (an), 4D-Var analysis (4v), 4D-increment analysis (4i) files • variables coming out of the analysis • variables coming out of the forecasts – with reference times

5. Model levels and layers • Documented accurate method to determine model level and layer coefficients. • Tables and codes that provide them • netCDF file with values • Tricky matter • GRIB files have model layer interfaces defined, not the level • Contrast of ERA-15 (red) versus ERA-40 and ERA-Interim (blue)

6. High Resolution Model Level Data Two forms combined define atmosphere • T255 spectral coefficients, Model Level Fields • Z, geopotential height of level 1 • T, temperature, 60 levels • W, vertical velocity, 60 levels • VO, relative vorticity, 60 levels • LNSP, log. of surface pressure • D, divergence, 60 levels • N128 reduced Gaussian, Model Level Fields • Q, specific humidity, 60 levels • O3, ozone mass mixing ratio, 60 levels • CLWC, cloud liquid water content, 60 levels • CIWC, cloud ice water content, 60 levels • CC, cloud cover, 60 levels dss.ucar.edu/datasets/ds627.0/docs/era_interim_grib_table.oper_an_ml.html

7. Horizontal GridsNCAR will compute Regular Gaussian (512x256) N128 512x256

8. Regular Gaussian (512x256) Transform to aid users • N128 Reduced Gaussian  Regular Gaussian • T255 Spectral  Regular Gaussian • U and V winds are computed from VO and D Products to be transformed • Analyses on model levels (ml), surface (sfc), pressure levels (pl), isentropic levels (pt), and potential vorticity levels (pv). • Note: Important fields are in the forecast files • Transform only selected fields and forecast intervals

9. Surface Forecast Grids – Model resolution • Initialization every 12 hours • Generally, out to 240 hours • 3,6,9,12,15,18,21,24,30,36,42,48,60,72,84,96,108,120,132,144,156,168,180,192,204,216,228,240 http://dss.ucar.edu/datasets/ds627.0/docs/era_interim_grib_table.oper_fc_sfc.html

10. Regular Gaussian (512x256), continued What high resolution data will ASR use? • N128 and T255 spectral model level orregular Gaussian model level data created at NCAR? If regular Gaussian, then: • We expect ASR to use the analysis (an) files. • We will extract some fields from the forecast (fc) files. • Are there any fields in the ‘fc’ files that you need? • Planning just one pass on the ‘fc’ files to create regular Gaussian Let’s get coordinated soon!

11. Regular Gaussian (512x256), continued • Surface and Single level analysis (N128) • 47 fields • http://dss.ucar.edu/datasets/ds627.0/docs/era_interim_grib_table.oper_an_sfc.html

12. Status @ NCAR • All products for January 1989 • High resolution transformations (reg. gaussian) • Decision still to be made on fields coming from the forecasts

13. Status @ NCAR • Within a product there are 6-hourly synoptic files • Our recommendation – if you plan to work with regular Gaussian model level fields ASAP begin working with the January 1989 data • Examine the model level and surface level analyses. • Examine forecasts for additional fields that ASR might need. Documents, metadata tables, test data (on NCAR/MSS) http://dss.ucar.edu/datasets/ds627.0/docs/ /DSS/DS627.0/ei.oper.an.ml/198901/ei.oper.an.ml.regn128sc.1989010100 /DSS/DS627.0/ei.oper.an.ml/198901/ei.oper.an.ml.regn128uv.1989010100 /DSS/DS627.0/ei.oper.an.sfc/198901/ei.oper.an.sfc.regn128sc.1989010100 /DSS/DS627.0/ei.oper.fc.sfc/198901/ei.oper.fc.sfc.regn128sc.1989010100 /DSS/DS627.0/ei.oper.fc.sfc/198901/ei.oper.fc.sfc.regn128sc.1989010112

14. Status Future • December 2007 data will arrive next • Delivery – probably, mid-March, 2009 • Receive and process 1989 – 2007 • Receive 2008, about August, 2009 • 2009 updates by network transfer • Lagging about 3 months behind real time @ ECMWF • Establish the RDA online service. Product suite TBD • All data will be on the NCAR MSS • How will ASR get a copy of ERA-Interim?

15. ASR Data Management at NCAR • Managed a component in the NCAR/CISL Research Data Archive (RDA) • http://dss.ucar.edu/index.html • Planning for about 55 TB total (?) • Duplicate copies on the NCAR MSS • All data available to the public (?) • usage restriction? • 5-7 TB online, network access (TBD) • Follow template used for JRA-25 • http://dss.ucar.edu/datasets/ds625.0/

16. What we need to know • Was there a proposed data management plan? • Is a product model like ERA-Interim suitable • e.g. ml, pl, sfc, forecasts, etc. ? • Will the netCDF file metadata be CF compliant? • Good idea, enables tool compatibility • How will the data files be structured? • Synoptic 3-hourly • Single variable time series

17. What we need to know • How to deal with the 2x horizontal resolution and polar projection? • What interpolations from model coordinates will be done? • Will pressure level data be computed? • Will time averages be computed • e.g. monthly means • Will model assimilation feedback be added to the observations used, should that data be archived? In what format?

18. What we need to know • What other organization will host ASR data? • We must not duplicate efforts • How will we get the data to NCAR? • Tapes, TB disks, network? • Who will provide other organization bulk data delivery? • How do we handle re-runs and fixes?

19. Contacts