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1. TITLE
1.1 Data Set Identification.
Total and convective precipitation
(6-hourly ; NOAA/NMC, GPCP Hybrid)
1.2 Data Base Table Name.
Not Applicable.
1.3 CD-ROM File Name.
\DATA\YyyMmm\NMC_GPCP\nnnn_nnn\Oymmddhh.sfx
\DATA\YyyMmm\NMC_GPCP\nnnn_nnn\Cymmddhh.sfx
Where nnnn_nnn is the parameter name (The NOAA/NMC, GPCP Precipitation
data have 2 types of parameters, see table below). Note: capital letters
indicate fixed values that appear on the CD-ROM exactly as shown here,
lower case indicates characters (values) that change for each path and
file.
The format used for the filenames is: nymmddhh.Z, where n is the
parameter descriptor (see table below), y is the last digit of the year
(e.g., 7=1987), mm is the month of the year (e.g., 12=December), dd is
the day (i.e 01 to 31), and hh is the first two digits in the hour (e.g.,
12=1200 Greenwich Mean Time (GMT)). The filename extension (.Z),
indicates that the files are compressed and must be decompressed before
use (see section 8.4). Below is the list of the parameters, directory
names and descriptors:
Parameter Description Parameter Directory Name Descriptor
------------------------------------------------------------------------
Total Precipitation TOTL_PRC O
Convective Precipitation CNVT_PRC C
1.4 Revision Date Of This Document.
April 5, 1995.
2. INVESTIGATOR(S)
2.1 Investigator(s) Name And Title.
Dr. Kenneth E. Mitchell
Research Meteorologist
Development Division
National Meteorological Center (NMC)
Dr. Ying Lin
UCAR Visiting Scientist
Development Division
National Meteorological Center
2.2 Title Of Investigation.
Application of NMC Reanalysis precipitation to
temporal partitioning of GPCP monthly precipitation
for ISLSCP Initiative I CD-ROM data sets.
2.3 Contacts (For Data Production Information).
___________________________________________________________________
| Contact 1 | Contact 2 |
_______________|_________________________|________________________|
2.3.1 Name |Dr. Ken Mitchell |Dr. Ying Lin |
2.3.2 Address|Development Division |Development Division |
|DOC, NOAA |DOC, NOAA |
|W/NMC22, WWB, Rm 204 |W/NMC22, WWB, Rm 204 |
City/St.|Wasington DC, USA |Washington DC, USA |
Zip Code|20233 |20233 |
2.3.3 Tel. |301-763-8161 |301-763-8056 |
2.3.4 Email |wd22km@sgi74.wwb.noaa.gov|wd22yl@sun1.wwb.noaa.gov|
_______________|_________________________|________________________|
2.4 Requested Form of Acknowledgement.
Mitchell, K.E., and Y. Lin, 1994: Production of 6-hourly
continental precipitation data sets for 1987 and 1988 for ISLSCP
Initiative I, Development Division, National Meteorological
Center, Washington, DC.
3. INTRODUCTION
3.1 Objective/Purpose.
The objective of this data set is to provide a global continental
precipitation time series of relatively high temporal frequency.
Its purpose is to fulfill the precipitation forcing needs of the
various land-surface/hydrology initiatives of the Global Energy
and Water Cycle Experiment (GEWEX), including ISLSCP, GCIP, GNEP,
and PILPS.
One chief application is in the initiative of the GEWEX Global Soil
Wetness Workshop (4-6 Oct 1994, Longmont, Colorado), which enlisted
a number of international land-surface modeling groups to utilize
the same global, continental atmosperic forcing data as input to
various land-surface process models to generate a set of global
soil wetness estimates for use in global climate models and other
applications. A good discussion of the need for and approach to
a global soil wetness initiative is given by Dirmeyer (1995) in
his summary of a related forerunner meeting on soil wetness
(COLA, 19 Aug 94, Calverton, MD).
3.2 Summary of Parameters.
The data set provides global gridded 1-degree fields of 6-hourly
total and convective precipitation for 1987/88. Over a given
month, the 6-hourly total precipitation sums up to the original
monthly total of the GPCP data set. As in the GPCP data set,
all values over sea points (non-land mass) are set to zero.
The convective precipitation is always less than or equal to the
total precipitation for each 6-hour (and hence monthly) period.
3.3 Discussion.
The starting point for the generation of the 6-hour precipitation
analyses here was the global 1-degree monthly land mass precipit-
ation analyses of the GPCP, available as separate, independent
data sets in the ISLSCP Initiative I CD-ROM SET. Briefly summarizing
the latter, the GPCP a) collects monthly precipitation totals
received in CLIMATE reports via the World Weather Watch GTS (Global
Telecommunication System), b) calculates monthly totals from
synoptic reports, and c) acquires monthly precipitation data
from international/national meteorological and hydrological
services/institutions. On the basis of these precipitation-gauge
measurements, 1-degree gridded analyses over land areas are
carried out using a spatial objective analysis method. For
further documentation, refer to the documentation in this CD-ROM
collection accompanying the GPCP monthly analyses. Note that the
GPCP analyses on this CD-ROM set and applied below are 1-degree,
land-mass only, and based on surface gauge measurements only.
But the GPCP data sets provide only monthly total precipitation.
To satisfy the GEWEX modeling needs discussed in Sec. 3.1,
NMC agreed to partition the above GPCP monthly precipitation
analyses into estimates of 6-hourly total and convective
precipitation time series, using the 6-hourly precipitation time
series of the global 4DDA-based NMC Reanalysis Project (Kalnay
and Jenne, 1991; Kalnay et al. 1993, Kalnay et al., 1995). The NMC
Reanalysis 6-hourly precipitation time-series are the source of the
derivation of temporal partitioning coefficients or weights applied to
the GPCP monthly precipitation totals. Note that the NMC Reanalysis
precipitation is used only to derive weights for temporal partitioning,
so that the derived time series sum up over one month to the original
monthly GPCP amounts.
The NMC Reanalysis provides an opportunity to estimate not only
the 6-hourly time series of total precipitation, but also the
time series of convective precipitation, since both total and
convective precipitation amounts at 6-hourly intervals are
routine products of the Reanalysis. Here we embrace this
opportunity and derive a time series of 6-hourly convective
precipitation from the 6-hourly total precipitation by applying
in each 6-hour period the Reanalysis ratio of convective to total
precipitation. The user must bear in mind that the above ratio
is a product of the physical parameterizations for stable and
convective precipitation in the GCM of the NMC Reanalysis.
4. THEORY OF MEASUREMENTS
The derivation of this data set begins with the GPCP gauge-based monthly
precipitation analyses. See the GPCP documentation (GPCP_PRC.DOC), for a
description of the gauge measurements.
5. EQUIPMENT
See comment in Sec. 4.
5.1 Instrument Description.
Not applicable.
5.1.1 Platform.
Not applicable.
5.1.2 Mission Objectives.
Not applicable.
5.1.3 Key Variables.
Not applicable.
5.1.4 Principles of Operation.
Not applicable.
5.1.5 Instrument Measurement Geometry.
Not applicable.
5.1.6 Manufacturer of Instrument.
Not applicable.
5.2 Calibration.
5.2.1 Specifications.
Not applicable.
5.2.1.1 Tolerance.
Not applicable.
5.2.2 Frequency of Calibration.
Not applicable.
5.2.3 Other Calibration Information.
Not applicable.
6. PROCEDURE
6.1 Data Acquisition Methods.
Four input data sets were acquired to derive the final dataset described
in this document. See Sec. 9 for a description of how these input data
sets were processed to derive the final data set.
The four input sets are:
1) The GPCP global 1-degree gauge-based monthly precipitation
analyses for 1987 & 1988 (available and documented on this CD-ROM
set).
2) The NMC Reanalysis global 1.875-degree 4DDA-based 6-hourly
total precipitation analyses for 1987 & 1988, available from NMC,
(Kalnay et al., 1993, Kalnay et al., 1995).
3) The NMC Reanalysis global 1.875-degree 4DDA-based 6-hourly
convective precipitation analyses for 1987 & 1988, available from
NMC, (Kalnay et al., 1993, Kalnay et al., 1995).
4) The NASA/GSFC global 4x5 degree gauge-based daily precip
analyses for Dec 1978 through Nov 1979, available from NASA/GSFC,
(G. Walker, private communication, NASA/GSFC,
greg@rootboy.gsfc.nasa.gov; see also Liston et al., 1993,
specifically Sec. 2.c, page 13). Sec. 9.2.1 below provides
more details on this data set.
6.2 Spatial Characteristics.
For each of the four input data sets listed in Sec. 6.1,
the spatial characteristics are as follows:
1) GPCP Monthly Precipitation: global 1-degree latitude by
longitude.
2) NMC Reanalysis 6-Hourly Total Precipitation: global
1.875-degree latitude by longitude.
(Specifically a 192 x 94 Gaussian grid, commonly used in
global spectral models; the longitude increment is 1.875
degree, the latitude increment is slightly variable, but
nearly 1.915 degree.)
3) NMC Reanalysis 6-Hourly Convective Precipitation:
same as 2) above.
4) NASA/GSFC Daily Precipitation: global 4x5 degree latitude
by longitude (Dec 1978 - Nov 1979 only)
Again, we emphasize that the final derived data set is derived
from the above four input data sets as described in Sec. 9.
The spatial characteristics of the final derived data set is
global 1-degree latitude by longitude. This is described in
more detail next in Secs. 6.2.1 and 6.2.2.
6.2.1 Spatial Coverage.
The coverage is global. Data in each file are ordered from North
to South and from West to East beginning at 180 degrees West and
90 degrees North. Point (1,1) represents the grid cell centered
at 89.5 N and 179.5 W (see section 8.4).
Only land-mass grid points have non-zero values. All values over
water are zero (as in GPCP). The 1-degree land/water mask is
available in this CD-ROM collection.
6.2.2 Spatial Resolution.
The final data set is given on an equal-angle grid that has
a spatial resolution of 1 X 1 degree lat/long.
6.3 Temporal Characteristics.
6.3.1 Temporal Coverage.
The final data set covers the period Jan 1987 through Dec 1988.
6.3.2 Temporal Resolution.
The final data set is 6-hourly.
7. OBSERVATIONS
7.1 Field Notes.
See Sec. 3.3.
8. DATA DESCRIPTION
8.1 Table Definition With Comments.
Not applicable.
8.2 Type of Data.
------------------------------------------------------------------------------
| 8.2.1 | | | |
|Parameter/Variable Name | | | |
------------------------------------------------------------------------------
| | 8.2.2 | 8.2.3 | 8.2.4 | 8.2.5 |
| |Parameter/Variable Description |Range |Units |Source |
------------------------------------------------------------------------------
|TOTAL PRECIP | | |GPCP gauge |
| |The total amount of |min = 0., |[MM] |analysis and |
| |precipitation over a six hour |max = 1000., | |NMC 4DDA |
| |period. |over sea = 0. | |Reanalysis |
| | | | | |
------------------------------------------------------------------------------
|CONVECTIVE PRECIP | | |GPCP gauge |
| |The convective precipitation |min = 0., |[MM] |analysis and |
| |over a six hourly period. |max = 1000., | |NMC 4DDA |
| | |over sea = 0. | |Reanalysis |
| | | | | |
------------------------------------------------------------------------------
8.3 Sample Data Base Data Record.
Not applicable.
8.4 Data Format.
Compressed format:
The ECMWF data has been compressed using Unix Compress. Compress uses
the modified Lempel-Ziv algorithm popularized in "A Technique for High
Performance Data Compression", Terry A. Welch, IEEE Computer, vol. 17,
no. 6 (June 1984), pp. 8-19. Common substrings in the file are first
replaced by 9-bit codes 257 and up. When code 512 is reached, the
algorithm switches to 10-bit codes and continues to use more bits until
the limit specified by the -b flag is reached (default 16). Bits must be
between 9 and 16. The default can be changed in the source to allow
compress to be run on a smaller machine.
The amount of compression obtained depends on the size of the input, the
number of bits per code, and the distribution of common substrings. The
ECMWF data has been reduced by approximately 85%. So watch out!!!
The data described here can be de-compressed using the platform specific
programs listed below.
DOS MAC UNIX VMS
----------------------------------------------------
u16.zip MacGzip0.3b2 gzip1-2-3 gzip-1-2-3
These programs are located in the SOFTWARE directory on this CD-ROM. The
programs are also available via FTP from many archival data bases on the
Internet. Information on anonymous FTP sites which supply these software
can be obtained via anonymous FTP at ftp.cso.uiuc.edu in the directory
/doc/pcnet in the file compression.
Uncompressed format:
The CD-ROM file format is ASCII, and consists of numerical fields of
varying length, which are space delimited and arranged in columns and
rows. Each column contains 180 numerical values and each row contain 360
numerical values.
Grid arrangement
ARRAY(I,J)
I = 1 IS CENTERED AT 179.5W
I INCREASES EASTWARD BY 1 DEGREE
J = 1 IS CENTERED AT 89.5N
J INCREASES SOUTHWARD BY 1 DEGREE
90N - | - - - | - - - | - - - | - -
| (1,1) | (2,1) | (3,1) |
89N - | - - - | - - - | - - - | - -
| (1,2) | (2,2) | (3,2) |
88N - | - - - | - - - | - - - | - -
| (1,3) | (2,3) | (3,3) |
87N - | - - - | - - - | - - - |
180W 179W 178W 177W
ARRAY(360,180)
8.5 Related Data Sets.
1) The ECMWF data on ISLSCP Initiative I CD-ROMs 2, 3, and 4,
2) The GPCP global 1-degree gauge-based monthly precipitation
analyses for 1987 & 1988 (available and documented on the ISLSCP
Initiative I, Volume 1 CD-ROM).
3) The NMC Reanalysis global 1.875-degree 4DDA-based 6-hourly
total precipitation analyses for 1987 & 1988, available from NMC,
(Kalnay et al., 1993, Kalnay et al. 1995).
4) The NMC Reanalysis global 1.875-degree 4DDA-based 6-hourly
convective precipitation analyses for 1987 & 1988, available from
NMC, (Kalnay et al., 1993, Kalnay et al. 1995).
4) The NASA/GSFC global 4x5 degree gauge-based daily precip
analyses for Dec 1978 through Nov 1979, available from NASA/GSFC,
(G. Walker, private communication, NASA/GSFC,
greg@rootboy.gsfc.nasa.gov; see also Liston et al., 1993,
specifically Sec. 2.c, page 13). Sec. 9.2.1 below provides
more details on this data set.
9. DATA MANIPULATIONS
9.1 Formulas.
9.1.1 Derivation.
See Sec. 9.2.1.
9.1.2 Techniques/Algorithms.
See Sec. 9.2.1.
9.2 Data Processing Sequence.
9.2.1 Processing Steps and Data Sets.
For a given month in 1987 & 1988, and for a given global 1-degree
grid land mass point denoted (i,j), we denote the following
relative to the first three input data sets in Sec. 6.2:
GP(i,j) - original monthly GPCP precipitation amount
NMC Reanalysis total precip amount for day k of month for
RPT06(i,j,k,1) - first 6-hour period
RPT06(i,j,k,2) - second 6-hour period
RPT06(i,j,k,3) - third 6-hour period
RPT06(i,j,k,4) - fourth 6-hour period
RPT24(i,j,k) - summation of above four 6-hour amounts
RPTMM(i,j) - monthly total from summation of RPT24(i,j,k)
over all days k of given month
NMC Reanalysis convective precip for day k of month for
RPC06(i,j,k,1) - first 6-hour period
RPC06(i,j,k,2) - second 6-hour period
RPC06(i,j,k,3) - third 6-hour period
RPC06(i,j,k,4) - fourth 6-hour period
RPC24(i,j,k) - summation of above four 6-hour amounts
We note that RPCtt convective precip amount is always less
than or equal to the corresponding RPTtt total precip amount.
The desired partitioned 6-hourly GPCP total precipitation amount
GPT06(i,j,k,1) - first 6-hour period
GPT06(i,j,k,2) - second 6-hour period
GPT06(i,j,k,3) - third 6-hour period
GPT06(i,j,k,4) - fourth 6-hour period
The desired partitioned 6-hourly GPCP convective precipitation
amount
GPC06(i,j,k,1) - first 6-hour period
GPC06(i,j,k,2) - second 6-hour period
GPC06(i,j,k,3) - third 6-hour period
GPC06(i,j,k,4) - fourth 6-hour period
In Section 6.2, we noted that the original NMC Reanalysis fields
are provided on a 192 x 94 global Gaussian grid at 1.875 by
1.915 degree. Our first operation is to bilinearly interpolate
these horizontally to the 1-degree grid of the GPCP fields.
The above notation of RPTtt or RPCtt denotes 1-degree Reanalysis
fields after this interpolation.
Before applying the above 1-degree Reanalysis precipitation
fields, we first filtered the fields, as described next, to
eliminate an identified tendency for the Reanalysis to generate
too many days of measurable daily rainfall in the warm months over
the southeast portions of both the North American and Asian
continents. This tendency is a product of the convective
parameterization scheme in the GCM of the Reanalysis system. The
hydrological modelers who expect to apply the final 6-hourly
precipitation data set firmly urged us to take care in reproducing
observed frequencies of measurable daily precipitation.
To accomplish the filter, we needed a gauge-based, global,
land-mass analysis of DAILY rainfall. Such fields are not
easily available on a global basis. (Indeed it is the lack of
such gauge-based global daily precipitation analyses that led
to this very project to apply Reanalysis to monthly GPCP.) One
exception is the data set 4) in Section 6.1 and Section 6.2,
namely the NASA/GSFC gauge-based global 4x5 degree daily
precipitation analysis spanning the FGGE months of Dec 1978
through Nov 1979 (used in Liston et al., 1993). Even though the
above analysis is for 1979, we decided its frequency of measurable
daily rainfall was more representative than that of Reanalysis.
Note that we apply below only the FREQUENCY in 1979 as a filter
threshold. We do NOT use the order of precipitation events in the
1979 daily series as a source for the order of events in the final
1987 & 1988 data set here. Rather the Reanalysis time series
(filtered below) will determine the order of 6-hourly precip
events.
Thus for the same FGGE calendar month as the given month
in 1987 & 1988 assumed above, we denote the daily, 24-hour
precipitation amount from the NASA/GSFC gauge-based global
analysis as
NP24(i,j,k) - 24-hour precipitation amount for day k
Following earlier practice, the above denotes the NASA/GSFC
analysis after bilinear interpolation from 4x5 degree to the
GPCP 1-degree grid.
To accomplish the frequency filter, for each (i,j) land
mass point, we compute for the given month a) the number of
days, NR(i,j), in which RPT24(i,j,k) exceeded 1 mm and
b) the number of days, NF(i,j), in which NP24(i,j,k) exceeded
1 mm. If NF(i,j) > 10 (in order to target convective regions
for the most part) and NR(i,j) > NF(i,j) then we iterated
to determine a threshold daily precipitation amount, E(i,j), such
that if RPT24(i,j,k) < E(i,j), then we set RPT24(i,j,k)=0
and RPC24(i,j,k)=0 and hence also we set
RPT06(i,j,k,1)=RPT06(i,j,k,2)=RPT06(i,j,k,3)=RPT06(i,j,k,4)=0
RPC06(i,j,k,1)=RPC06(i,j,k,2)=RPC06(i,j,k,3)=RPC06(i,j,k,4)=0
for each such day k of the month satisfying the threshold,
with the result that after such filtering (month by month)
then NR(i,j)=NF(i,j) whenever NF(i,j) > 10. Thus, at a given
grid point (i,j), if RPT24(i,j,k) is less than the threshold
E(i,j), then ALL Reanalysis precipitation amounts for that day
were set to zero. Note that the threshold field E(i,j) was
determined separately for each of the 48 months in 1987 & 1988.
With few exceptions, the values of E(i,j) were less than several
millimeters.
We denote all such filtered Reanalysis fields as follows
(for tt=06 and tt=24):
RPTttF = filtered counterpart to RPTtt
RPCttF = filtered counterpart to RPCtt
RPTMMF = filtered counterpart to RPTMM
At last, it is straightforward to derive the desired
temporally partitioned GPCP analyses.
First, the 6-hourly partitioned GPCP total precipitation
is derived for each day k of given month from
GPT06(i,j,k,m) = [RPT06F(i,j,k,m)/RPTMMF(i,j)] * GP(i,j)
for each 6-hourly period m=1,2,3,4. In the above we see that
the Reanalysis 6-hourly amount, scaled by the Reanalysis
monthly total, acts as the temporal partitioning or weighting
coefficient. (Note: If GP(i,j)=0, then we set GPT06(i,j,k,m)=0.
If GP(i,j) is nonzero and RPTMMF(i,j) is zero, we search for
and substitute for RPT06F and RPTMMF from the nearest land
mass (i,j) at which RPTMMF is nonzero.)
Secondly, the 6-hourly partitioned GPCP convective precipitation
is derived for each day k of given month from
GPC06(i,j,k,m)=[RPC06F(i,j,k,m)/RPT06F(i,j,k,m)]*GPT06(i,j,k,m)
for each 6-hourly period m=1,2,3,4. In the above we see that
the Reanalysis 6-hourly convective amount, scaled by the
Reanalysis 6-hourly total amount, acts as the convective
partitioning or weighting coefficient. (Note: If
GPT06(i,j,k,m) is zero, then we set GPC06(i,j,k,m)=0.
If GPT06(i,j,k,m) is nonzero, then RPT06F(i,j,k,m) is
nonzero and hence GPC06(i,j,k,m) is well defined.)
9.2.2 Processing Changes.
None at the time of this first revision.
9.3 Calculations.
9.3.1 Special Corrections/Adjustments.
See Sec. 9.2.1 above.
9.4 Graphs and Plots.
See Mo et al. (1995), Kalnay et al. (1993), and Kalnay et al. (1995).
10. ERRORS
10.1 Sources of Error.
The final data set inherits errors from the four input data
sets of Section 6.1.
First, the monthly totals obtained by summing the derived
6-hourly time series agree with the input GPCP monthly
precipitation. Hence these monthly totals reflect the
accuracy of the GPCP analyses.
In particular, the procedures of Section 9 were specifically
designed to avoid having the monthly totals of this 6-hourly
data set reflect any of the biases in monthly totals in the
NMC Reanalysis.
The sources of error in the input GPCP monthly precipitation
analyses are discussed in Section 10 of the GPCP documentation
in this CD-ROM set. The reader should review all of that
information.
Within a given month, the temporal character of the
precipitation time series is dependent on the temporal character
of the NMC Reanalysis precipitation.
In the NMC Reanalysis, stringent care was given to quality
control (see Kalnay et al., 1993, and Kalnay et al., 1995).
Nevertheless, as in any modern state-of-the-art multi-variant
four-dimensional data assimilation system (4DDA), the NMC
Reanalysis inevitably embodies some systematic errors.
The precipitation fields from the NMC Reanalysis have been
examined by external researchers and presented at the recent
Nineteenth Annual Climate Diagnostics Workshop, sponsored
during 14-18 Nov 94 at College Park, MD by the Cooperative
Institute for Climate Studies at the University of Maryland.
The results showed, for example, that the diurnal character
of the precipitation fields from the NMC Reanalysis compared
favorably with observations in the spring season over the
central U.S. and that this diurnal character was significantly
better than an alternative non-NMC reanalysis product.
On the other hand, in the NMC Reanalysis, researchers have found
that the frequency of measurable daily precipitation is too high
over the southeast portions of the North American and Asian
continents. Hence the frequency filter described in Section 9.2
was applied.
The resultant temporal character of the 6-hourly time series,
though having some of the limitations of a global 4DDA system,
are nevertheless superior in our view for many applications to
the alternative of a researcher having to take the GPCP monthly
amounts and arbitrarily distributing these amounts across the
monthly period (e.g., a constant mean 6-hourly amount for
the whole month). Furthermore, the Reanalysis-based time
series are strongly linked to the regular progression of
synoptic weather systems and convective triggers that
characterize the real atmosphere.
As cited earlier, the data set includes the 6-hourly time
series for both total and convective precipitation. Of
the two, the total precipitation time series is more
reliable, as the temporal character and relative magnitude
of the convective time series is heavily tied to the
convective parameterization scheme in the GCM of the
NMC Reanalysis system. Some sensitivities of the Reanalysis
precipitation to choice of convective parameterization scheme
are presented in Kalnay et al. (1993). Despite some NMC
reluctance to provide the convective time series, GEWEX modelers
strongly urged this present attempt, because their land surface
process models often require a partitioning between non-convective
and convective precipitation, and once again 4DDA, or its
Reanalysis equivalent, was viewed as the best reasonably
available means for providing this separation.
10.2 Quality Assessment.
10.2.1 Data Validation by Source.
See Section 10.2.1 of the GPCP documentation for
information on that source.
The NMC Reanalysis precipitation has been compared
on a global monthly basis with GPCP monthly analyses,
with other precipitation climatologies, and with
other Reanalysis products from other centers. Regional,
diurnal, and water budget characteristics have been
studied by both internal and external NMC researchers.
Since the Reanalysis products are very new, much of the
above research is not yet available in the commonly
available literature. One exception is the study by
Mo et al. (1995), who examined the sensitivity of the
Reanalysis, including global precipitation analyses, to
the use or omission of satellite data in the Reanalysis.
Other very recent examples of Reanalysis fields are given
in Kalnay et al. (1995).
10.2.2 Confidence Level/Accuracy.
See previous Sec. 10 subsections above.
10.2.3 Measurement Error for Parameters and Variables.
Not applicable.
10.2.4 Additional Quality Assessment Applied.
In the final data set, the following checks were applied.
1 - No negative values.
2 - The summation over one month of the 6-hourly time
series of total precipitation agrees at every
grid point with the original GPCP monthly amount.
3 - The convective precipitation amount is always less
than or equal to the total precipitation amount.
4 - All over water values (sea) are zero.
5 - No missing flags (-99999.99) are present in either
the input GPCP monthly analyses or the final output
6-hourly time series.
11. NOTES
11.1 Known Problems With The Data.
See Section 10 above and Section 11.1 in the companion documentation
for the GPCP monthly precipitation analyses.
11.2 Usage Guidance.
In data void or sparse continental areas, the quality of the
analysis results will be less reliable.
11.3 Other Relevant Information.
Not available.
12. REFERENCES
12.1 Satellite/Instrument/Data Processing Documentation.
WCRP, 1990. The Global Precipitation Climatology Project -
Implementation and Data Management Plan. WMO/TD-No. 367, Geneva,
June 1990, 47 pp. and appendices.
Kalnay, E., M. Kanamitsu, R. Kistler, W. Collins, D. Deaven, L. Gandin,
S. Saha, G. White, J. Woollen, M. Chelliah, J. Janowiak, K.C. Mo, J.
Wang, A. Leetmaa, R. Reynolds, R. Jenne, E. Kung, and D. Salstein,
1993. The NMC/NCAR CDAS/Reanalysis Project, NMC Office Note 401,
Washington, DC, October 1993, 42 pp. and figures.
12.2 Journal Articles and Study Reports.
Dirmeyer, P.A., 1995. Summary of Meeting on Problems in Initializing
Soil Wetness, submitted to Bull. Amer. Meteor. Soc. (also available
as COLA Report No. 9, January 1995, COLA, Calverton, MD).
Kalnay, E., M. Kanamitsu, R. Kistler, W. Collins, D. Deaven, L. Gandin,
M. Iredell, S. Saha, G. White, J. Woollen, Y. Zhu, M. Chelliah, W.
Ebisuzaki, W. Higgins, J. Janowiak, K.C. Mo, C. Ropelewski, A.
Leetmaa, R. Reynolds, R. Jenne, 1995. The NMC/NCAR Reanalysis
Project. Submitted to the Bull. Amer. Meteor. Soc.
Kalnay, E., and R. Jenne, 1991. Summary of the NMC/NCAR reanalysis.
Bull. Amer. Meteor. Soc., 72:1897-1904.
Liston, G.E., Y.C. Sud, and G.K. Walker, 1993. Design of a Global Soil
Moisture Initialization Procedure for the Simple Biosphere Model,
NASA Tech Memo 104590, NASA Goddard Space Flight Center, Greenbelt,
MD, 130 pp.
Mo, K.C., X.L. Wang, R. Kistler, M. Kanamitsu, and E. Kalnay, 1995.
Impact of satellite data on the CDAS-Reanalysis System, Mon. Wea.
Rev., 123:124-139.
12.3 Archive/DBMS Usage Documentation.
Contact the EOS Distributed Active Archive Center (DAAC) at NASA Goddard
Space Flight Center (GSFC), Greenbelt Maryland (see Section 13 below).
Documentation about using the archive or information about access to the
on-line information system is available through the GSFC DAAC User
Services Office.
13. DATA ACCESS
13.1 Contacts for Archive/Data Access Information.
GSFC DAAC User Services
NASA/Goddard Space Flight Center
Code 902.2
Greenbelt, MD 20771
Phone: (301) 286-3209
Fax: (301) 286-1775
Internet: daacuso@eosdata.gsfc.nasa.gov
13.2 Archive Identification.
Goddard Distributed Active Archive Center
NASA Goddard Space Flight Center
Code 902.2
Greenbelt, MD 20771
Telephone: (301) 286-3209
FAX: (301) 286-1775
Internet: daacuso@eosdata.gsfc.nasa.gov
13.3 Procedures for Obtaining Data.
Users may place requests by accessing the on-line system, by sending
letters, electronic mail, FAX, telephone, or personal visit.
Accessing the GSFC DAAC Online System:
The GSFC DAAC Information Management System (IMS) allows users to
ordering data sets stored on-line. The system is open to the public.
Access Instructions:
Node name: daac.gsfc.nasa.gov
Node number: 192.107.190.139
Login example: telnet daac.gsfc.nasa.gov
Username: daacims
password: gsfcdaac
You will be asked to register your name and address during your first
session.
Ordering CD-ROMs:
To order CD-ROMs (available through the Goddard DAAC) users should
contact the Goddard DAAC User Support Office (see section 13.2).
13.4 GSFC DAAC Status/Plans.
The ISLSCP Initiative I CD-ROM is available from the Goddard DAAC.
14. OUTPUT PRODUCTS AND AVAILABILITY
14.1 Tape Products.
None.
14.2 Film Products.
None.
14.3 Other Products.
None.
15. GLOSSARY OF ACRONYMS
4DDA four dimensional data assimilation
COLA Center for Ocean-Land-Atmosphere Studies
DAAC Destributed Active Archive Center
DOC Department of Commerce
EOS Earth Observation System
EOS-DIS EOS data and Information System
GCIP GEWEX Continental Scale Project
GCM General Circulation Model
GEWEX Global Energy and Water Cycle Experiment
GNEP GEWEX Numerical Experimentation Project
GPCP Global Precipitation Climatology Project
GSFC Goddard Space Flight Center
GTS Global Telecommunications System
ISLSCP International Satellite Land Surface Climatology Project
NASA National Aeronautics and Space Administration
NMC National Meteorological Center
NOAA National Oceanic and Atmospheric Administration
PILPS Project for Intercomparison of Land-Surface Process Schemes
UCAR University Corporation for Atmospheric Research
