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ERA-Interim and ASR Data Management at NCAR. Steven Worley Dave Stepaniak Chi-Fan Shih February 17, 2009. ERA-Interim. Time Period, 1989-current T255L60 4DVAR global, spectral or reduced Gaussian Products high resolution reg. gaussian (512x256) 37 press. lvls . (1000  1)

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era interim and asr data management at ncar

ERA-Interim and ASR Data Management at NCAR

Steven Worley

Dave Stepaniak

Chi-Fan Shih

February 17, 2009

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)
information sources documentation
Information sources / documentation
  • Web pages
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
model levels and layers
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)
high resolution model level data
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


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
surface forecast grids model resolution
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

regular gaussian 512x256 continued
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!

regular gaussian 512x256 continued1
Regular Gaussian (512x256), continued
  • Surface and Single level analysis (N128)
    • 47 fields
status @ ncar
Status @ NCAR
  • All products for January 1989
    • High resolution transformations (reg. gaussian)
  • Decision still to be made on fields coming from the forecasts
status @ ncar1
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)








  • 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?
asr data management at ncar
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
what we need to know
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
what we need to know1
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?
what we need to know2
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?