Four-dimensional Assimilated Dataset for the TOGA COARE Intensive Observing Period (IOP)
Entry ID:
COARE_lsa_dao
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Summary
Abstract:
DATA ACCESS The NASA/TOGA COARE Data Archive http://daac.gsfc.nasa.gov/fieldexp/TOGA/ A subset of the 4-D DAO data (26N-26S, 40E-100W) is available from the NASA GSFC DAAC via ftp from ftp://disc1.gsfc.nasa.gov/data/toga_coare/assim/dao/ BACKGROUND TOGA COARE was a multidisciplinary, international research effort that investigated the scientific phenomena associated with the interaction ... between the atmosphere and the ocean in the warm pool region of the
western Pacific. The field experiment phase of the program took place
from 1 November 1992 through 28 February 1993 and involved the
deployment of oceanographic ships and buoys, several ship and land
based Doppler radars, multiple low and high level aircraft equipped
with Doppler radar and other airborne sensors, as well as a variety of
surface based instruments for in situ observations.
DATASET INFORMATION
The 4-D Assimilated Dataset is a 4-month, global, gridded atmospheric
dataset for use in large-scale atmospheric research. The Laboratory
for Atmospheres Data Assimilation Office (DAO) at Goddard Space Flight
Center (GSFC) produced this dataset by assimilating rawinsonde
reports, satellite retrievals of geopotential thickness, cloud-motion
winds, aircraft, ship, and rocketsonde reports with model forecasts
employing version 1 of the Goddard Earth Observing System (GEOS-1)
atmospheric general circulation model (GCM). At the lower boundary,
the assimilating GCM is constrained by the monthly mean observed sea
surface temperature and climatological soil moisture derived from
monthly mean observed surface air temperature and precipitation
fields.
The data are well suited for process studies and intraseasonal
variability research since they are produced by a fixed assimilation
system designed to minimize spinup in the hydrological cycle. By
using a nonvarying system the variability due to algorithm change is
eliminated and geophysical variability can be more confidently
isolated.
The data archived at the Goddard Distributed Active Archive Center
(DAAC) are a subset of the full dataset produced by the DAO. The
data are organized chronologically in a time series format to
facilitate the computation of statistics spanning long time periods.
Data are available for the time period November 1992 through February
1993. Data cover the geographical area 26N-26S and 40E-100W. These
data will be online. An expanded subset is available covering the
geographical area 50S-50N and 180W-180E.
In calculating variables for this dataset, the DAO makes a
distinction between PROGNOSTIC and DIAGNOSTIC variables. A prognostic
parameter is an atmospheric variable that the model forecasts. During
the assimilation these are the parameters most directly influenced by
the observations.
Diagnostic parameters are generally not measured, but are calculated
by the model in a manner consistent with the observations. Examples
of prognostic parameters include wind, temperature, and humidity.
Surface fields include albedo, pressure, wetness, temperature, and
ice/water flags. Both upper air and surface prognostic parameters are
sampled every 6 hours, though it must be kept in mind that in the
current version of the GCM (GEOS-1) some of the surface fields (e.g.,
albedo, sea surface temperature) are specified from temporally
interpolated monthly mean values, while the soil moisture is specified
using climatology; the fields are saved more frequently, simply for
convenience.
There are also many time averaged diagnostic parameters (e.g., heating
rates, precipitation, surface heat fluxes, radiative fluxes at the top
and bottom of the atmosphere, and upper air temperature and moisture
tendencies) provided either 8 or 4 times daily, depending upon whether
the parameter is a surface, single level or upper air quantity.
DATA SOURCE INFORMATION
The assimilated data were a synthesis of observations and short-term
model forecasts. Data were collected from globally deployed in situ
and remote observations throughout the assimilation period. The
platforms used to collect observations were:
1 - Tiros Operational Vertical Sounder (TOVS)
(NOAA/NESDIS thickness retrievals)
2 - Ships and Buoys
3 - Surface synoptic reports over land
4 - Rawinsondes, dropwindsondes, rocketsondes
5 - Aircraft (wind measurements)
6 - Cloud-motion winds
Sources 1, 4, 5, and 6 are used in the upper air analyses of height
and wind, while the moisture analysis uses only rawinsonde reports.
Sources 2 and 3 are used in the determination of sea level pressure
and near-surface wind analysis over the oceans. It should be noted
that for this DAO TOGA COARE analysis all wind and sea level pressure
data collected during COARE (that was received over the GTS) were
assimilated. TOGA COARE upper air moisture and temperature data were
withheld.
The analysis scheme is carried out at a horizontal resolution of 2
degrees latitude by 2.5 degrees longitude at 14 upper-air pressure
levels (20, 30, 50, 70, 100, 150, 200, 250, 300, 400, 500, 700, 850,
1000 mb) and at sea level. Note, however, that the assimilated data
are provided at 18 pressure levels with higher vertical resolution in
the lower troposphere.
The analysis increments are computed every 6 hours using observations
from a +/-3 hour data window centered on the analysis times (00, 06,
12, and 18 UTC). The model computes a 3-hour forecast from an initial
reference time. This forecast is compared to its observational
counterpart (which was collected during a 6 hour interval centered on
the forecast time). An estimate of the forecast error is computed and
divided into incremental updates. The model is then re-run from the
initial reference time for 6 hours with the incremental updates
applied to the simulation. Another three-hour forecast is produced and
the cycle is repeated. It is the model integration forced by the
incremental updates that makes up the assimilated data provided here.
For more detailed information on the assimilation system, please refer
to the appropriate references in section 7 of this document.
DATASET ORGANIZATION
There are 22 different files for each month in the assimilation
period, for a total of 88 data files over the 4-month run. Associated
with every data file is a short ASCII "table" file containing
descriptive information to allow data interpretation by the Grid
Analysis and Display System (GrADS) visualization package developed at
the University of Maryland. The table file includes the name of the
associated data file, the x, y, and z coordinate scales, the value
used for undefined data, the number of time periods, the date, and a
list of the parameters contained in the data file. Since the data
files contain only binary science data, all spatial, temporal and
parameter information for these files must be inferred from the file
name or the contents of the accompanying table file. The file naming
conventions are as follows:
Data file : edvl049.prs.xxxxxxx_ss.byymmdd.eyymmdd
Table file : edvl049.tabl.xxxxxxx_ss.byymmdd.eyymmdd
where byymmdd, eyymmdd are the beginning and ending year, month, and
day, respectively (spanning 1 month, e.g., b921101.e921130), and
xxxxxxx denotes the parameters contained in that file. These
parameters are drawn from the designations given in the third column
of the list below. The first part of the file names, edvl049.prs and
edvl049.tabl, remain the same for all files. Each file contains
parameters for all days of the specified month.
The parameters are listed below along with their corresponding units
and filename designator:
Surface prognostic fields Units File Location
------------------------- ----- -------------
SURFACE GEOPOTENTIAL HEIGHTS (G * M) (m/s)^2 sfcprog
SURFACE ALBEDO (0-1) sfcprog
SURFACE GROUND WETNESS (0-1) sfcprog
SURFACE PRESSURE - PTOP (mb) sfcprog
SURFACE GROUND TEMPERATURE (K) sfcprog
SEA LEVEL PRESSURE (mb) sfcprog
LAND_(2), WATER_(1), ICE_(3) FLAGS - sfcprog
VERTICALLY INTEGRATED (BAROTROPIC) U-WIND (m/s) sfcprog
VERTICALLY INTEGRATED (BAROTROPIC) V-WIND (m/s) sfcprog
Upper air prognostic fields (18 levels) Units File Location
--------------------------- ----- -------------
U-WIND (m/s) uwnd
V-WIND (m/s) vwnd
GEOPOTENTIAL HEIGHT (m) hght
TEMPERATURE (K) tmpu
SPECIFIC HUMIDITY (g/kg) sphu
TURBULENT KINETIC ENERGY (m/s)^2 qq
STANDARD DEVIATION OF HEIGHT ERROR (m) hghte
Surface diagnostic fields (group 1) Units File Location
----------------------------------- ----- -------------
SURFACE PRESSURE - PTOP (PTOP= 10mb) (mb) diag1
TOTAL PRECIPITATION (mm/day) diag1
CONVECTIVE PRECIPITATION (mm/day) diag1
SURFACE EVAPORATION (mm/day) diag1
VERTICALLY AVERAGED U*Q (m/s g/kg) diag1
VERTICALLY AVERAGED V*Q (m/s g/kg) diag1
VERTICALLY AVERAGED U*T (m/s K) diag1
VERTICALLY AVERAGED V*T (m/s K) diag1
TOTAL PRECIPITABLE WATER (g/cm^2) diag1
Surface diagnostic fields (group 2) Units File Location
----------------------------------- ----- -------------
SURFACE PRESSURE - PTOP (PTOP= 10mb) (mb) diag2
U-MOMENTUM SURFACE STRESS (N/m^2) diag2
V-MOMENTUM SURFACE STRESS (N/m^2) diag2
SURFACE FLUX OF SENSIBLE HEAT (W/m^2) diag2
SURFACE DRAG COEF. FOR T AND Q - diag2
SURFACE DRAG COEF. FOR U AND V - diag2
SURFACE WIND SPEED (m/s) diag2
FRICTION VELOCITY USTAR (m/s) diag2
SURFACE ROUGHNESS Z0 (m) diag2
PBL DEPTH (mb) diag2
Surface diagnostic fields (group 3) Units File Location
----------------------------------- ----- -------------
SURFACE PRESSURE - PTOP (PTOP= 10mb) (mb) diag3
NET UPWARD LW RADIATION AT GROUND (W/m^2) diag3
NET DOWNWARD SW RADIATION AT GROUND (W/m^2) diag3
OUTGOING LONGWAVE RADIATION (W/m^2) diag3
OUTGOING LONGWAVE RADIATION CLEAR SKY (W/m^2) diag3
SURFACE LONGWAVE FLUX CLEAR SKY (W/m^2) diag3
INCIDENT SW RADIATION AT TOP OF ATMOS (W/m^2) diag3
OUTGOING SHORTWAVE RADIATION (W/m^2) diag3
OUTGOING SHORTWAVE RADIATION CLEAR SKY (W/m^2) diag3
SURFACE SHORTWAVE FLUX CLEAR SKY (W/m^2) diag3
2-DIMENSIONAL TOTAL CLOUD FRACTION (0-1) diag3
Surface diagnostic fields (group 4) Units File Location
----------------------------------- ----- -------------
SURFACE PRESSURE - PTOP (PTOP= 10mb) (mb) diag4
GROUND TEMPERATURE (K) diag4
SURFACE AIR TEMPERATURE (K) diag4
SATURATION SURFACE SPECIFIC HUMIDITY (g/kg) diag4
SURFACE PRESSURE TENDENCY (mb/day) diag4
U AT 2 METERS (m/s) diag4
V AT 2 METERS (m/s) diag4
T AT 2 METERS (K) diag4
Q AT 2 METERS (kg/kg) diag4
U AT 10 METERS (m/s) diag4
V AT 10 METERS (m/s) diag4
T AT 10 METERS (K) diag4
Q AT 10 METERS (kg/kg) diag4
Upper air diagnostic fields (18 levels) Units File Location
--------------------------------------- ----- -------------
U-MOMENTUM CHANGES DUE TO TURBULENCE (m/s/day) turbu
V-MOMENTUM CHANGES DUE TO TURBULENCE (m/s/day) turbv
MOISTURE CHANGES DUE TO TURBULENCE (g/kg/day) turbq
TEMPERATURE CHANGES DUE TO TURBULENCE (K/day) turbt
TEMPERATURE CHANGES DUE TO MOIST PROCESSES (K/day) moistt
MOISTURE CHANGES DUE TO MOIST PROCESSES (g/kg/day) moistq
TEMPERATURE CHANGES DUE TO LW RADIATION (K/day) radlw
TEMPERATURE CHANGES DUE TO SW RADIATION (K/day) radsw
VERTICAL VELOCITY (mb/day) omega
FILLING OF NEGATIVE SPECIFIC HUMIDITY (g/kg/day) qfill
Thus, surface diagnostics are contained in 4 files, surface
prognostics in 1 file, upper air prognostics in 7 files, and upper air
diagnostics in 10 files. Each upper air prognostic file or each upper
air diagnostic file will contain a single parameter for 18 pressure
levels. These levels are located at 1000, 950, 900, 850, 800, 700,
600, 500, 400, 300, 250, 200, 150, 100, 70, 50, 30, and 20 mb. On the
other hand, each surface prognostic file or each surface diagnostic
file will contain all the parameters in that category evaluated at the
surface or the vertical average through the atmosphere. A summary of
the individual file characteristics is shown in the following table:
# Reporting # Reporting File size (bytes)
File # Parameters levels times/day (31-day month)
---- ------------ ------------ ------------ --------------
1. sfcprog 9 1 4 10735920
2. uwnd 1 18 4 21471840
3. vwnd 1 18 4 21471840
4. hght 1 18 4 21471840
5. tmpu 1 18 4 21471840
6. sphu 1 18 4 21471840
7. qq 1 18 4 21471840
8. hghte 1 18 4 16700320
9. diag1 9 1 8 21471840
10. diag2 10 1 8 23857600
11. diag3 11 1 8 26243360
12. diag4 13 1 8 31014880
13. turbu 1 18 4 21471840
14. turbv 1 18 4 21471840
15. turbt 1 18 4 21471840
16. turbq 1 18 4 21471840
17. moistt 1 18 4 21471840
18. moistq 1 18 4 21471840
19. radlw 1 18 4 21471840
20. radsw 1 18 4 21471840
21. omega 1 18 4 21471840
22. qfill 1 18 4 21471840
All prognostic quantities (in files 1-8 above) represent instantaneous
values at the designated synoptic time, i.e., at 00Z, 06Z, 12Z or
18Z. The surface diagnostics (in files 9-12), which are reported 8
times daily at 00Z, 03Z, 06Z, etc., are averages over the 3 hour
period immediately prior to the designated time tag. For example, a
tag of 18Z denotes an average from 15Z-18Z. The upper air diagnostics
(in files 13-22) refer to averages over a 6 hour period centered on
the designated time tag (i.e., a tag of 18Z denotes an average from
15Z-21Z).
All fields are written in a time-series format, i.e., all global
parameter arrays are written out for each daily time period in
sequence and then for each day of the month. As an example, for
surface prognostics for November 1992, the data and table file names
will be:
edvl049.prs.sfcprog_ss.b921101.e921130
edvl049.tabl.sfcprog_ss.b921101.e921130
with the data file having the following organization:
November 1 00Z field 1 ----> field 9
(geopotential height) (vert. int. barotropic vwind)
November 1 06Z field 1 ----> field 9
(geopotential height) (vert. int. barotropic vwind)
November 1 12Z field 1 ----> field 9
(geopotential height) (vert. int. barotropic vwind)
November 1 18Z field 1 ----> field 9
(geopotential height) (vert. int. barotropic vwind)
followed by the same geophysical fields for November 2, November 3,...,
November 30.
In the case of the upper air prognostic variable u-wind, the files would be
called:
edvl049.prs.uwnd_ss.b921101.e921130
edvl049.tabl.uwnd_ss.b921101.e921130
with the data file having the following organization:
November 1 00Z field 1 ----> field 18
(1000mb U-wind) (20 mb U-wind)
November 1 06Z field 1 ----> field 18
(1000mb U-wind) (20mb U-wind)
November 1 12Z field 1 ----> field 18
(1000mb U-wind) (20mb U-wind)
November 1 18Z field 1 ----> field 18
(1000mb U-wind) (20mb U-wind)
followed by the same geophysical parameters for November 2, November
3,..., November 30.
The logical organization of an upper air diagnostic file will be
similar to the upper air prognostic file shown above, while the
surface diagnostic files (diag1, diag2, diag3, diag4) will be similar
to the surface prognostic files except that there will be twice the
number of time periods (3 hour increments) and a different number of
fields (9 for diag1, 10 for diag2, 11 for diag3, 13 for diag4 (see
above table listings)).
For each field in a file, there are 89 grid points in longitude with
the first grid point at 40E and with a grid spacing of 2.5
degrees. There are 27 grid points in latitude with the first grid
point at 26S and with a grid spacing of 2.0 degrees. The data are
stored such that all values along the first latitude (26S) are written
first, followed by data from the next northernmost latitude (24S), and
continuing on to the last latitude at 26N. For longitude, the first
data point is 40E followed by 42.5E and so on to the 89th grid point
at 100W. All data are written as IEEE 32-bit floating point numbers.
DATA
The data are IEEE 32-bit floating point, written sequentially. There
are no header or trailer records, and the data are distributed
uncompressed.
The expanded set is available on 4 mm (DAT), high or low density 8 mm
(Exabyte), and 6250 bpi 9-track tapes.
Reading the 4D Assimilation Data Files:
Two FORTRAN programs are available from the Goddard DAAC to read the
upper air data products. These programs are called the UPPER AIR
SAMPLE READ PROGRAM and the SINGLE LEVEL SAMPLE READ PROGRAM.
For each DATA FILE there is an associated TABLE FILE as mentioned
above. Some DATA FILES contain a number of different fields at a
single level; the TABLE FILE is used to determine how many fields are
in the dataset.
>From the TABLE FILE
NTIMES is provided by TDEF (number of time steps)
NXX is provided by ZDEF for upper air files (vertical levels)
NXX is provided by VARS for single level files (parameters)
IM is provided by XDEF (longitude)
JNP is provided by YDEF (latitude)
The 4-D Assimilated Dataset is compatible with the Grid Analysis and
Display System (GrADS) data analysis and visualization software
package. This package was developed by Brian Doty with support from
Jim Kinter at the Center for Ocean-Land-Atmosphere Studies (COLA) at
the University of Maryland. It has gained widespread acceptance by
the scientific community as a valuable data analysis tool. The system
handles a variety of gridded datasets and observational data. Both
the data and table files are required as input in the GrADS package.
The software is distributed and supported by the authors via anonymous
FTP at COLA. 
Related URL
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Description:
Access the 4-Dimensional Assimilated Data Set.
Description:
README for the 4-Dimensional Assimilated Data Set
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Geographic Coverage
(Click for Interactive Map)
Spatial coordinates
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N: 50.0
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S: -50.0
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E: 180.0
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W: -180.0
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Data Set Citation
Dataset Originator/Creator:
TOGA COARE
Dataset Title:
Four-dimensional Assimilated Dataset for the TOGA COARE Intensive Observing Period (IOP)
Online Resource:
http://daac.gsfc.nasa.gov/fieldexp/TOGA/
Temporal Coverage
Start Date:
1992-11-01
Stop Date:
1993-02-28
Data Resolution
Latitude Resolution:
2 degrees
Longitude Resolution:
2.5 degrees
Horizontal Resolution Range:
100 km - < 250 km or approximately 1 degree - < 2.5 degrees
Temporal Resolution:
6 Hours
Temporal Resolution Range:
Hourly - < Daily
Creation and Review Dates
DIF Creation Date:
2007-03-12
Last DIF Revision Date:
2009-11-18
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