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
(to be here)

3. Information sources / documentation
Web pages

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 Grids NCAR will compute Regular Gaussian (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

10. Regular Gaussian (512x256), continued
What high resolution data will ASR use?
N128 and T255 spectral model level or regular 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

12. Status @ NCAR All products for January 1989
High resolution transformations (reg. gaussian)
Decision still to be made on fields coming from the forecasts
ASR
Product
Size (GB/mn) ✔
an.ml 21
an.pl 16
an.pt 4
an.sfc 2
an.pv .2

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)
/DSS/DS627.0/ei.oper.an.ml/198901/ei.oper.an.ml.regn128sc
/DSS/DS627.0/ei.oper.an.ml/198901/ei.oper.an.ml.regn128uv
/DSS/DS627.0/ei.oper.an.sfc/198901/ei.oper.an.sfc.regn128sc
/DSS/DS627.0/ei.oper.fc.sfc/198901/ei.oper.fc.sfc.regn128sc
/DSS/DS627.0/ei.oper.fc.sfc/198901/ei.oper.fc.sfc.regn128sc

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 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)
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

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 Steven Worley worley@ucar.edu Dave Stepaniak
Chi-Fan Shih