GEOS-FP

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NOTE: The GEOS-FP ("forward processing") met data product (formerly known as GEOS-5.7.2) is now the active the operational met field product being produced by GMAO. GEOS-FP has now replaced the older GEOS-5.2.0 product.

This page describes some basic information about the new GMAO GEOS-5.7.2 data product. This product will be released in Summer 2011.

For more information, please see:

  1. GEOS-5.7.2 file specification document, Version 1.2 (04 Aug 2011)
  2. GEOS-5.7.2 upgrade page
  3. List of GEOS-5.7.2 met fields for GEOS-Chem
  4. Details about the implementation of GEOS-5.7.2 into GEOS-Chem
  5. GEOS-5 page on the GEOS-Chem wiki
  6. Overview of GMAO met data products
  7. Evolution of the GEOS-5 system from GEOS-5.2.0/MERRA to GEOS-5.7.2 (aka "Fortuna")

Overview

From the GEOS-5.7.2 (v1.2) file specification document (04 Aug 2011), p. 7:

The GEOS-5.7.2 Atmospheric Data Assimilation System (GEOS-5 ADAS) uses an analysis developed jointly with NOAA’s National Centers for Environmental Prediction (NCEP) which allows the Global Modeling and Assimilation Office (GMAO) to take advantage of the developments at NCEP and the Joint Center for Satellite Data Assimilation (JCSDA). The GEOS-5 AGCM uses the finite-volume dynamics (Lin, 2004) integrated with various physics packages (e.g, Bacmeister et al., 2006), under the Earth System Modeling Framework (ESMF) including the Catchment Land Surface Model (CLSM) (e.g., Koster et al., 2000). The GSI analysis is a three-dimensional variational (3DVar) analysis applied in grid-point space to facilitate the implementation of anisotropic, inhomogeneous covariances (e.g., Wu et al., 2002; Derber et al., 2003). The GSI implementation for GEOS-5.7.2 incorporates a set of recursive filters that produce approximately Gaussian smoothing kernels and isotropic correlation functions.

The GEOS-5 ADAS is documented in Rienecker et al. (2008). More recent updates to the model are presented in Molod et al. (2011). The GEOS-5 system actively assimilates roughly 2 × 106 observations for each analysis, including about 7.5 × 105 AIRS radiance data. The input stream is roughly twice this volume, but because of the large volume, the data are thinned commensurate with the analysis grid to reduce the computational burden. Data are also rejected from the analysis through quality control procedures designed to detect, for example, the presence of cloud.

To minimize the spurious periodic perturbations of the analysis, GEOS-5.7.2 uses the Incremental Analysis Update (IAU) technique developed by Bloom et al. (1996).

The analysis is performed at a horizontal resolution of 0.3125° longitude by 0.25° latitude and at 72 levels, extending to 0.01 hPa. All products are generated at the native resolution of the horizontal grid. The majority of data products are time-averaged, but four instantaneous products are also available. Hourly data intervals are used for two-dimensional products, while 3-hourly intervals are used for three-dimensional products. These may be on the model’s native 72-layer vertical grid or at 42 pressure surfaces extending to 0.1 hPa.

--Bob Y. 14:36, 4 August 2011 (EDT)

Acknowledge the source of GEOS-5.7.2 data in your publications

If your GEOS-Chem research depends on the GEOS-5.7.2 meteorological data producs, please consider adding an acknowledgment to your citations, such as:

The GEOS-5.7.2 data used in this study/project have been provided by the Global Modeling and Assimilation Office (GMAO) at NASA Goddard Space Flight Center.

--Bob Y. 14:38, 23 April 2012 (EDT)

GEOS-5.7.2 grid structure

This section describes the horizontal and vertical grids used by the GEOS-5.7.2 data products.

Input grids

From the GEOS-5.7.2 file specification document, Version 1.2 (04 Aug 2011), page 12:

Fields are produced on the model’s native horizontal grid, with a resolution of 5/16 degree longitude by 1/4 degree latitude.

</blockquote> The GEOS-5 global horizontal grid consists of IMn=1152 points in the longitudinal direction and JMn=721 points in the latitudinal direction. The horizontal native grid origin, associated with variables indexed (i=1, j=1) represents a grid point located at (180°W, 90°S). Latitude and longitude of grid points as a function of their indices (i, j) can be determined by: </blockquote> 

     Lon(I) = -180° + [ ΔLon * ( I - 1 ) ],  I = 1, IMN
     Lat(I) =  -90° + [ ΔLat * ( J - 1 ) ],  J = 1, JMN

Where ΔLon = 5/16° = 0.3125° and ΔLat = 1/4° = 0.25°. For example, (i = 577, j = 361) corresponds to a grid point at ( 0, 0).

and on page 13:

Gridded products use four different vertical configurations: horizontal-only (can be vertical averages, single level, or surface values), pressure-level, model-level, or model-edge. Horizontal-only data for a given variable appear as 3-dimensional fields (x, y, time), while pressure-level, model-level, or model-edge data appear as 4-dimensional fields (x, y, z, time). In all cases the time dimension spans multiple files, as each file (granule) contains only one time. Pressure-level data is output on the LMp=42 pressure levels shown in Appendix B. The model layers used for GEOS-5.7.2 products are on a terrain-following hybrid sigma-p coordinate. Model-level data is output on the LM=72 layers shown in the second table of Appendix B. The model-edge products contain fields with LMe = LM + 1 levels representing the layer edges. The pressure at the model top is a fixed constant, PTOP=0.01 hPa. Pressures at model edges should be computed by summing the DELP starting at PTOP. A representative pressure for the layer can then be obtained from these. In the GEOS-4 eta files, one could compute the pressure on the edges by using the “ak” and “bk” values and the surface pressure. In GEOS-5, the full 3-dimensional pressure variables are explicitly provided through (DELPijl) and PTOP. Even though the model-level fields are on a hybrid sigma-p coordinate and their vertical location could be obtained from the “ak-bk” relationship, this may change in future GMAO systems. We thus recommend that users rely on the reported 3D pressure distribution, and not use ones computed from the “ak” and “bk”.

Note that the indexing for the GEOS-5.7.2 vertical coordinate system is top to bottom, i.e., layer 1 is the top layer of the atmosphere, while layer LM is adjacent to the earth’s surface. The same is true for edge variables, with level 1 being the top of the model’s atmosphere (PTOP), and level LM+1 being the surface

The table below lists the combination of the horizontal and vertical grids onto which the GEOS-5.7.2 "raw" data products are placed:

Grid Name Horizontal
Resolution 		Vertical
Resolution 		Used for Notes
Horizontal-only Nx 0.25° x 0.3125° 1 level Surface data fields
(e.g. PS, EVAP, HFLUX, etc.)
Model level Nv 0.25° x 0.3125° 72 hybrid levels Most 3D data fields
(e.g. U, V, T, etc.) 		Vertical levels are identical to
GEOS-5.2.0 and MERRA data
Model edges Ne 0.25° x 0.3125° 73 hybrid level edges Data fields defined on level edges
(e.g. PLE) 		Vertical level edges are identical to
GEOS-5.2.0 and MERRA data
Pressure Np 0.25° x 0.3125° 42 pressure levels:

1000, 975, 950, 925, 900, 875,
850, 825, 800, 775, 750, 725,
700, 650, 600, 550, 500, 450,
400, 350, 300, 250, 200, 150,
100, 70, 50, 40, 30, 20,
10, 7, 5, 4, 3, 2, 1
0.7, 0.5, 0.4, 0.3, 0.1 hPa

Various 3D data fields We do not use of the pressure-level for GEOS-Chem.
We only use data on the Nx, Nv, Ne grids.

Output grids

We foresee the use of GEOS-5.7.2 at the following resolutions:

  1. GEOS-Chem 2° x 2.5° grid
  2. GEOS-Chem 4° x 5° grid

as well as native resolution for GEOS-Chem nested grid simulations.

--Bob Y. 13:33, 14 April 2011 (EDT)

GEOS-5.7.2 file naming convention

The following description of the naming convention used for GEOS-5.7.2 "raw" data files is paraphrased from Section 5.1 and 5.2 of the GEOS-5.7.2 file specification document, Version 1.2 (04 Aug 2011), pp 12-16:

Standard names

The standard generic complete name for the assimilated GEOS-5 products will appear as follows: 

       DAS.config.mode.collection.sys_ver.timestamp.file_ver.nc4

A brief description of the node fields appear below:

DAS
Identifies output as a Data Assimilation System product.For mainstream MERRA data, the following runid's are used:
config
GEOS-5 will run in only one operational configuration. Other configurations may be added later.
  1. ops: Operational assimilation, nominally 12 hours behind real-time.
mode
GEOS-5 can run in different modes of operation, but the only mode used to support EOS instrument teams is asm.
  1. asm: Assimilation. Uses a combination of atmospheric data analysis and model forecasting to generate a time-series of global atmospheric quantities.
collection
All GEOS-5.7.1 data are organized into file collections that contain fields with common characteristics. These collections are used to make the data more accessible for specific purposes. Fields may appear in more than one collection. Collection names are of the form freq_dims_group_HV, where the four attributes are:
  1. freq: time-independent (cnst), instantaneous (instF), or time-average (tavgF), where F indicates the frequency or averaging interval and can be any of the following:
    • 1 = Hourly
    • 3 = 3-Hourly
  2. dims: Can be either:
    • 2d for collections with only 2-dimensional fields or
    • 3d for collections with a mix of 2- and 3-dimensional fields.
  3. group: A three-letter mnemonic for the type of fields in the collection.
  4. HV: Horizontal and Vertical grid.
    • H can be:
      • N: Native (2/3° x 1/2°) horizontal resolution
    • V can be:
      • x: horizontal-only data (surface, single level, etc.) ; dims must be 2D
      • p: pressure-level data (see Appendix D for levels) ; dims must be 3D
      • v: model layer centers (see Appendix D ) dims must be 3D
      • e: model layer edges (see Appendix D ) dims must be 3D
sys_ver
This node defines the GEOS-5 system version that was used to generate this data.
  1. GEOS571: GEOSdas 5.7.1 is the current operational version of GEOS-5.
timestamp
This node defines the date and time associated with the data in the file. It has the form yyyymmdd_hhmm for either instantaneous or time-averaged daily files, yyyymm_hhmm for monthly-mean files.
  1. yyyy - year string (e.g. , 2002)
  2. mm - month string (e.g.., 09 for September)
  3. dd - day of the month string
  4. hh - hour (UTC)
  5. mm - minute
file_ver
This denotes the file version in the form V##. Under normal conditions ## will be 01. In the event of a processing error that requires a re-processing, this number will be incremented to identify the new version of this file.
  1. nc4: All files are in NetCDF-4 format, thus the suffix .nc4.


EXAMPLE: 

       DAS.ops.asm.inst3_3d_asm_Np.GEOS571.20101201_0000.V01.nc4

This is an example of a GEOS-5.7.2 filename. The collection is instantaneous, three-dimensional, assimilation products, at the native horizontal resolution, interpolated to pressure levels. The file contains data valid at 00 UTC on 01 December 2010.

--Bob Y. 14:36, 4 August 2011 (EDT)

ESDT names

To accommodate EOSDIS toolkit requirements, all GEOS-5 files are associated with a nine-character Earth Science Data Type (ESDT) name. The ESDT, also known as the ShortName, is a short handle for users to access sets of files and takes the form: 

       D57TFHVGGG

where

  1. T: Time Description:
    • I = Instantaneous
    • T = Time-averaged
    • C = Time-independent
  2. F: Frequency
    • 1 = Hourly
    • 3 = 3-Hourly
  3. H: Horizontal Resolution
    • N = Native
  4. V: Vertical Location
    • X = Two-dimensional
    • P = Pressure
    • V = model layer center
    • E = model layer edge
  5. GGG: Group
    • ASM = assimilated state variables (from the IAU corrector, see Appendix A)
    • TDT = tendencies of temperature
    • UDT = tendencies of eastward and northward wind components
    • QDT = tendencies of specific humidity
    • ODT = tendencies of ozone
    • LND = land surface variables
    • FLX = surface turbulent fluxes and related quantities
    • MST = moist processes
    • CLD = cloud-related quantities
    • RAD = radiation TRB = turbulence SLV = single level
    • INT = vertical integrals
    • CHM = chemistry forcing
    • AER = aerosol diagnostics
    • LSF = Large scale flux

--Bob Y. 14:36, 4 August 2011 (EDT)

GEOS-5.7.2 data file collections

The following information is taken from the GEOS-5.7.2 file specification document, Version 1.2 (04 Aug 2011), p. 17:

The GEOS-5 forward processing (FP) product is organized into the 21 collections listed below. These are described in detail in the next sections. All data is on the model’s native horizontal grid, which is a regular latitude-longitude grid with a spacing of 1/4° in latitude and 5/16° in longitude. Horizontal arrays (1152,721) are ordered by longitude first, with the first point at the Dateline and the South Pole, with the inner index increasing eastward. All 3d collections, except the inst3_3d_asm_Np, are on the model’s native, hybrid sigma-p vertical grid. ... Data in the inst3_3d_asm_Np are interpolated to the 42 pressure levels defined above.

File Collection
Name 		ESDT Name
(aka "Shortname") 		Description Times Used for
GEOS-Chem? 		Approx daily
size (MB)
const_2d_asm_Nx D57C0NXASM Constant fields Time-invariant Yes minimal
inst3_3d_asm_Nv D57I3NVASM Basic assimilated fields from IAU corrector Instantaneous values every 3 hours Yes 6,160
tavg3_3d_cld_Nv D57T3NVCLD Upper-air cloud related diagnostics 3-hour time-averaged values Yes 2,176
tavg3_3d_mst_Nv D57T3NVMST Upper-air diagnostics from moist processes at layers 3-hour time-averaged values Yes 816
tavg3_3d_mst_Ne D57T3NEMST Upper-air diagnostics from moist processes at layers 3-hour time-averaged values Yes 736
tavg3_3d_rad_Nv D57T3NVRAD Upper-air diagnostics by radiation 3-hour time-averaged values Yes 2,440
tavg3_3d_udt_Nv D57T3NVUDT Upper-air wind tendencies by process 3-hour time-averaged values Yes 8,800
tavg1_2d_slv_Nx D57T1NXSLV Single-level atmospheric state variables 1-hour time-averaged values Yes 1,104
tavg1_2d_flx_Nx D57T1NXFLX Surface fluxes and related quantities 1-hour time-averaged values Yes 1,006
tavg1_2d_rad_Nx D57T1NXRAD Surface and TOA radiative fluxes 1-hour time-averaged values Yes 648
tavg1_2d_lnd_Nx D57T1NXLND Land related surface quantities 1-hour time-averaged values Yes 600
tavg1_2d_ocn_Nx D57T1NXOCN Ocean related surface quantities 3-hour time-averaged values Yes 350
tavg3_3d_lsf_Nv D57T3NVLSF Upper-air large-scale flux 3-hour time-averaged values No 1,600
inst3_3d_asm_Np D57I3NPASM Basic assimilated fields from IAU corrector Instantaneous values every 3 hours No 3,480
inst3_3d_asm_Np D57I3NXASM Miscellaneous 2D assimilated fields from IAU corrector Instantaneous values every 3 hours No 192
inst3_3d_aer_Nv D57I3NVAER 3D instantaneous aerosol diagnostics Instantaneous values every 3 hours No 11,200
inst3_3d_chm_Nv D57I3NVCHM 3D instantaneous chemistry diagnostics Instantaneous values every 3 hours No 1,520
tavg3_3d_trb_Ne D57T3NETRB Upper-air diagnostics from turbulence at layer edges 3-hour time-averaged values No 4,736
tavg3_3d_tdt_Nv D57T3NVTDT Upper-air tendencies by process 3-hour time-averaged values No 5,640
tavg3_3d_qdt_Nv D57T3NVQDT Upper-air humidity tendencies by process 3-hour time-averaged values No 3,680
tavg3_3d_odt_Nv D57T3NVODT Upper-air ozone tendencies by process 3-hour time-averaged values No 2,720
tavg3_3d_lsf_Nv D57T3NVLSF Upper-air large-scale flux at level edges 3-hour time-averaged values No 1,104
tavg3_2d_aer_Nx D57T3NXAER 2D time-averaged aerosol diagnostics 3-hour time-averaged values No 992
tavg3_2d_chm_Nx D57T3NXCHM 2D time-averaged chemistry diagnostics 3-hour time-averaged values No 40

As described above, the full file name for the GEOS-5.7.2 data products takes the form: 

DAS.ops.asm.CCCCCCCCCCCCCCC.GEOS571.YYYYMMDD_hhmm.V01.nc4

where

  1. CCCCCCCCCCCCCCC is the collection name (i.e. one of the entries in the first column of the above table)
  2. YYYYMMDD_hhmm is the UTC date (year/month/day, hour:minutes)

--Bob Y. 11:49, 25 October 2011 (EDT)

GEOS-5.7.2 time archiving

Raw data

The GEOS-5.7.2 raw data are archived/averaged at the following times:

  1. const: Time-invariant data
  2. inst3: 3-hr instantaneous data
    • Times: 00:00, 03:00, 06:00, 09:00, 12:00, 15:00, 18:00, 21:00 GMT
  3. tavg1: 1-hour time-averaged data
    • Center times: 00:30, 01:30, 02:30 ... 23:30 GMT
  4. tavg3: 3-hour time-averaged data
    • Center times: 01:30, 04:30, 07:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT

Regridded data

The regridded GEOS-5.7.2 data for GEOS-Chem shall keep the same temporal resolution as the GEOS-5.7.2 raw data, and shall be split among the following data file types:

  1. CN (time-invariant data)
    • Filenames GEOS572.20110101.CN.{RESOLUTION}.nc
  2. A1 (1-hr time-averaged data)
    • Filenames GEOS572.YYYYMMDD.A1.{RESOLUTION}.nc
  3. A3 (3-hr time-averaged data)
    • Filenames
      • GEOS572.YYYYMMDD.A3cld.{RESOLUTION}.nc
      • GEOS572.YYYYMMDD.A3dyn.{RESOLUTION}.nc
      • GEOS572.YYYYMMDD.A3mstC.{RESOLUTION}.nc
      • GEOS572.YYYYMMDD.A3mstE.{RESOLUTION}.nc
  4. I3 (6-hr instantaneous data)
    • Filenames GEOS572.20110101.I3.{RESOLUTION}.nc

The CN files shall contain time-invariant data. For convenience we assign a file timestamp of 2011/01/01 at 00:00 GMT.

The I3 files shall contain instantaneous (i.e. snapshot) data at 00:00, 03:00, 06:00, 09:00, 12:00, 15:00, 18:00, 21:00 GMT.

The A1 and A3 files shall use the following bins for time-averaging. (NOTE: The image uses label "GEOS-5.7.1", but the time archiving is the same for GEOS-5.7.2.)

GEOS 571 times 800px.jpg

NOTE: GEOS-5.7.2 uses the same timing scheme as MERRA, with the exception that MERRA has 6-hour instantaneous data but GEOS-5.7.2 has 3-hour instantaneous data.

Please also see our List of GEOS-5.7.2 met fields wiki page for detailed information about which fields are stored in each of these file types.

--Bob Y. 10:26, 13 January 2012 (EST)

Implementation into GEOS-Chem

More info to be added later...

--Bob Y. 14:36, 4 August 2011 (EDT)

References

  1. GEOS-5.7.2 file specification document, Version 1.2 (04 Aug 2011)
  2. Bacmeister, J. T., M. J. Suarez, and F. R. Robertson, 2006. Rain Re-evaporation, Boundary Layer Convection Interactions, and Pacific Rainfall Patterns in an AGCM. J. Atmos. Sci., 63, 3383-3403.
  3. Bloom, S., L. Takacs, A. DaSilva, and D. Ledvina, 1996: Data assimilation using incremental analysis updates. Mon. Wea. Rev., 124, 1256-1271.
  4. Derber, J. C., R. J. Purser, W.-S. Wu, R. Treadon, M. Pondeca, D. Parrish, and D. Kleist, 2003: Flow-dependent Jb in a global grid-point 3D-Var. Proc. ECMWF annual seminar on recent developments in data assimilation for atmosphere and ocean. Reading, UK, 8-12 Sept. 2003.
  5. Koster, R. D., M. J. Suárez, A. Ducharne, M. Stieglitz, and P. Kumar, 2000: A catchment-based approach to modeling land surface processes in a GCM, Part 1, Model Structure. J. Geophys. Res., 105, 24809-24822.
  6. Molod, A., L. Takacs, M.J. Suarez, J. Bacmeister, I.S. Song, A. Eichmann, Y. Chang, 2011: The GEOS-5 Atmospheric General Circulation Model: Mean Climate and Development from MERRA to Fortuna. Technical Report Series on Global Modeling and Data Assimilation 104606, v28.
  7. Rienecker, M.M., M.J. Suarez, R. Todling, J. Bacmeister, L. Takacs, H.-C. Liu, W. Gu, M. Sienkiewicz, R.D. Koster, R. Gelaro, I. Stajner, and E. Nielsen, 2008: The GEOS-5 Data Assimilation System - Documentation of Versions 5.0.1, 5.1.0, and 5.2.0. Technical Report Series on Global Modeling and Data Assimilation 104606, v27.
  8. Wu, W.-S., R.J. Purser and D.F. Parrish, 2002: Three-dimensional variational analysis with spatially inhomogeneous covariances. Mon. Wea. Rev., 130, 2905-2916.

--Bob Y. 14:36, 4 August 2011 (EDT)

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