Section 2.0 contains a detailed description of the
instrumentation, siting, and algorithms used by the source network to collect
the data. Section 2.1 contains a detailed
description of the format of the composite dataset. See Section 2.2 for information on data processing, and Section 3.0 below for the quality control processing
performed by the National Center for Atmospheric Research/Earth Observing
Laboratory (NCAR/EOL) on this dataset. Section 4.0
contains references.
The CLICOM daily precipitation dataset was formed by extracting the
precipitation data values (element code=5) from CLICOM surface daily data.
These CLICOM data are from the Servicio Meteorologico Nacional de Mexico
(SMN)--the Mexican meteorological service--and have not been modified.
Observations at each of the stations were made at 08:00 LST. The value
reported for the daily observation represents data collected during the
previous 24 hours, ending at 08:00. The CLICOM data set is the final
station report per paper copy reports (one month entered on one summary
page). It is the final official data set.
The data, which are generally key entered from paper copy sheets at state
offices of the Mexican Water Commission (Comission Nacional de Agua, CNA),
contain observations from stations throughout Mexico. Observers in each
state send the data to state offices, which then digitizes the data from
the paper copies. The CLICOM surface data update for Mexico for 2004 was
provided by Lic Alejandro Gonzales Serratos of the SMN, and Art Douglas of
Creighton University. CLICOM is a WMO acronym for a climate data management
software system developed by the United Nations for developing countries.
The NAME precipitation data set is called the GASIR data set and it is
maintained by the CNA. Reporting of data is very poor on the weekends and data
is often missing when observers are away from their post. The CNA has a
relatively active ongoing effort to recover missing data after the cutoff time
for the morning reports. The CNA officially closes the monthly rainfall data set
6 months after the end of the month.
In contrast the SMN daily operational rainfall product (which NCEP ingests)
often shows data gaps due to problems with weekend reporting or due to problems
with data not being received from particular regional CNA offices. The latter
problem arises when a regional office fails to transmit its rainfall reports to
the central office in Mexico City. As the SMN daily rainfall report is prepared
each morning, late data is frequently not reentered into the data files on a
consistent basis. Instead, the SMN chooses to replace its operational rainfall
data set with the GASIR data set approximately one to two months after the close
of the month.
A final cautionary note needs to be added about missing data that may be
erroneously indicated with a "0" rather than missing. It has been found that
the SMN operational data set shows a dry bias country wide because many of the
regional collecting agencies will place a "0" into a station report that
actually was missing. This inconsistency has been a real problem in past years,
but the state agencies working with the SMN have tried to differentiate between
missing rainfall reports versus a station actually reporting no precipitation.
Again, the CNA data set appears not to suffer as much from this problem as does
the SMN operational product. The use of the "0" for missing data apparently
developed out of a need for a "place holder" in data sets that were used with
older computer software programs at the SMN.
The TD3200 data contained many sequences of missing days with no indication that
they were part of an accumulation period, followed by a day with a value marked
as an end accumulation total. Since there is no way to know when the
accumulation period began in these instances, missing days in the TD3200 dataset
that are not marked as being part of an accumulation period and which are
followed by an end accumulation total, are recorded simply as missing days in
this composite dataset with a "7" quality control flag. For more information,
see NCDC, 1991. The data also contained sequences of non-missing accumulation
values that did not terminate with an accumulation code. These values were
recorded as questionable in this composite with a "4" quality control flag.
There were also instances where there was a sequence of valid accumulation
values that did not terminate with the accumulation code. The value following
the sequence was marked as the accumulation end in this composite with a
question able quality control flag of "4".
The NCEP/EMC daily precipitation dataset was formed by
extracting data with NCEP/EMC element codes of PC and PP that fall on
the hour. The NCEP/EMC observations of daily precipitation can include
multiple measurements for a given day. When this occurs, the precipitation
for that day is set to missing in this NCAR/EOL NAME 2004 Daily
Precipitation Composite. The value reported for any daily observation
represents data collected during the previous 24 hours.
All raw precipitation data can be found on codiac in the
GCIP/EOP Surface: Precipitation NCEP/EMC Gage Only Daily Dataset.
NCEP/EMC excludes any precipitation value greater than 20 inches from the
NCEP/EMC daily precipitation dataset. The information above was
gathered from personal correspondence with NCEP/EMC during 1997 and
1998.
Data from cooperators networks such as NCEP/EMC has hundreds of
reporting locations which change from incremental to accumulator and back
to incremental. Others changed a couple of times and have now
settled on accumulators.
Anyone using this data must be aware of the dynamic changes in the
network of sites that are processed by HADS and be aware of the potential
lag time from when a change is implemented to when NCEP/EMC becomes aware of the
change. This is far, far from a stable environment.
To help users in identifying these changes, NCAR/EOL checks the
NCEP/EMC daily precipitation data for possible accumulated values and
resets the NCAR/EOL Quality Control flags for all "unchecked", "good",
and "trace" accumulated precipitation values in the NCEP/EMC network to
"questionable". For this purpose, NCAR/EOL defines accumulated
precipitation to be six identical, sequential daily precipitation values
potentially followed by additional identical values or values that
increase over time.
The user should pay close attention to the observation hour included with
each daily value. The observation hour indicates the ending hour
on the day the data were collected. Beware that this composite includes
both the daily precipitation extracted from NCEP/EMC hourly stations via the
"Daily Extract from NAME Precipitation Hourly Multi-Network Composite" and
daily precipitation from "Precipitation NCEP/EMC Gage Only Daily Dataset".
The daily NCEP/EMC values from the extraction have a observation hour of 23 while
the "Precipitation NCEP/EMC Gage Only Daily Dataset" daily values have
a observation hour of 0.
"The tipping bucket raingages used in NERN are the Texas Electronics TR-525USW
which are calibrated at 0.01 inches per tip. Each tip of the bucket
or "event", triggers an electronic signal which is then stored on an Onset
Computer Corporation HOBO Event datalogger. Rainfall events are
stored on the datalogger until manually downloaded. As of this writing there are
no remote communication devices attached to the raingages. The HOBO datalogger
has an 8000 event storage capacity which results in the effective storage of
2032 mm of precipitation. This quantity is substantially higher than the
mean annual precipitation in the NAME region. However, it is not guaranteed
that this capacity will never be exceeded in a particular year. Thus, the
entire network is scheduled to be downloaded at least twice a year to preserve
as much data as possible. Technical specifications on both
the raingage and the datalogger can be obtained from the vendor's websites
at the following URL's:
More information about the network can be found in a technical document
provided by the authors:
Gochis, D.G., J.-C. Leal, W.J. Shuttleworth, C. Watts, 2005:
NAME Surface Raingage Network Station Files. Technical document available
from the authors.
DATA COLLECTION AND PROCESSING
"Rainfall data is collected at a minimum of twice per year. As each gage is
visited the data is downloaded to a laptop computer and the gage is visually
inspected for damage, obstruction or anything that may inhibit the proper
function of the gage. A instrument log is kept which details the status and any
observed problems with each raingage. "
"The raw rainfall data is stored as rainfall events which correspond to tips
of the tipping bucket mechanism. This data is reprocessed into the
following equal interval periods:
"Quality control of the tipping bucket gage data is performed by visual
screening of the raw data time series and by direct comparison with manually
operated cooperative raingages which are collocated at approximately 25% of the
gage sites."
"As of Feb. 2005, an automated gross error check has been implemented into
the data processing algorithms. This routine flags 05min rainfall values
which are in excess of 12mm (=144 mm/hr). These 'extreme' events are then
manually examined in order to determine whether or not the event was in
fact plausible. Additional details of the gross error check methodology
and full details of the quality control procedures and the results
of the quality control assessment can be found in a Quality Control
Document prepared by the investigators:"
"Gochis, D.G., J.-C. Leal, A. Jimenez, 2005: NAME Tipping
Bucket Raingage Network Quality Control Log. Technical Document
available from the authors or from NCAR/EOL."
(NERN, 2006)
Only daily precipitation values from 86 NERN sites are included in
this NAME 2004 Daily Precipitation Composite.
The NCDC Summary of Day Co-operative data have observation hours that vary by
station. Data values are valid for the 24 hours preceding the observation hour
given for the day.
NCAR/EOL also checks the NCEP/EMC daily precipitation data for possible
accumulated values and resets the NCAR/EOL Quality Control flags for all
"unchecked", "good", and "trace" accumulated precipitation values in the
NCEP/EMC network to "questionable".
The user should pay close attention to the observation hour included with
each daily value. The observation hour indicates the ending hour
on the day the data were collected. Beware that this composite includes
both the daily precipitation extracted from NCEP/EMC hourly stations via the
"Daily Extract from NAME Precipitation Hourly Multi-Network Composite" and
daily precipitation from "Precipitation NCEP/EMC Gage Only Daily Dataset".
The daily NCEP/EMC values from the extraction have a observation hour of 23 while
the "Precipitation NCEP/EMC Gage Only Daily Dataset" daily values have
a observation hour of 0.
Duplicate stations between or within networks were not removed, but may be
identified via the occurrence value setting in the NAME 2004 Ancilliary
Station List which can be downloaded separately from the NAME Master Table
of Datasets.
Gross limit checks were also applied by NCAR/EOL to determine
the quality of the data in
the Precipitation Daily Multi-Network Composite [NCAR/EOL]. Data values
less than 180 millimeters were flagged as good. Any data value greater
than or equal to 180 millimeters but less than 220 millimeters was flagged
as questionable. Any data value greater than or equal to 220 millimeters
was flagged as unlikely. Several questionable and unlikely data values were
also manually inspected. After inspection, the quality control code and
flag may have been manually updated to better reflect the likelihood of the
actual occurrence of the precipitation value based on an isohyet analysis.
NCAR/EOL checks the NCEP/EMC daily precipitation data for possible
accumulated values and resets the NCAR/EOL Quality Control flags
for all "unchecked", "good", and "trace" accumulated precipitation
values in the NCEP/EMC network to "questionable". For this purpose,
NCAR/EOL defines accumulated precipitation to be six identical, sequential
hourly precipitation values potentially followed by additional identical
values or values that increase over time. The data were never changed, only
flagged. Tables 1 and 2 contain the quality control flags and codes,
respectively. Table 3 lists the applies gross limit values.
After the datasets were merged to form the NAME 2004
Precipitation Daily Multi-Network Composite [NCAR/EOL], a statistics
program was executed to ensure that the quality of the individual datasets
had been retained.
NERN, cited 2006: NAME Event Rain gauge Network [Available online from
http://data.eol.ucar.edu/datafile/nph-get/82.141/NAME_sfc_raingages_20050215.txt2.0 Detailed Data Description
2.0.1 Climate Computing Project (CLICOM) Algorithms
2.0.2 Mexican GASIR-CNA Rain Gage Network Data
The Mexican government maintains a wide network of climate stations across the
country. A majority of climate stations only record daily 24 hour precipitation
amounts. The nationwide climate network is primarily supported by the Mexican
Meteorological Service (Servicio Meteorólogico Nacional,SMN), the
Mexican Water Commission (Comisión Nacional de Agua, CNA) or local
county and state government agencies (Delegaciones). Readings are standardized
to be taken at 8:00 LST each morning and do not switch to and from Daylight
Savings Time. All equipment is standard WMO equipment.
2.0.3 NAME Supplemental Raingauge Nework [CNA/IMTA]
The network consists of a low-tech raingauge network installed at 113 high
elevation sites and 97 mean and low elevation sites in the state of Sonora.
Daily rainfall values are reported for most of the sites. The network utilizes
the existing infrastructure (radio and personnel) of the Civil Protection Agency
for the state of Sonora as well as of their agencies (police, army, highway) and
volunteers. Each station reports via radio or telephone to its municipality,
the municipality reports rain from their stations. Under special cases, data is
quality controlled and validated. At the headquarters of CP-SON there is one
person that contacts all the sites every day. Data are captured on a PC and
sent to IMTA, SMN, local government and states users, and used for operational
activities at CP-SON. The data are collected at 8:00 LST and do not switch to
and from Daylight Savings Time.
2.0.4 NCDC COOP NWS Cooperative Observer Daily Observations
The NWS Cooperative Observer Daily Precipitation dataset was formed by
extracting the daily incremental and accumulative precipitation values provided
in the National Climatic Data Center (NCDC) TD 3200 dataset
(NCDC, 1991). Both incremental
and accumulative values are included in this NAME 2004 Daily Precipitation
Composite. The incremental value reported for any daily observation represents
data collected during the previous 24 hours. The accumulative value is a total
of precipitation over one or more days when the observer made no measurements.
The days on which no measurements were made in an accumulation period are
represented with the missing value of -999.99, but flagged with a quality
control flag "1" to differentiate them from non-accumulation period missing
data. The day which has a data value of the accumulated total of precipitation
during all of the accumulation days is flagged with a quality control flag "2".
(For a description of the quality control flags, see section
3.0 below.)
2.0.5 Precipitation NCEP/EMC Gage Only Daily Dataset
The Environmental Modeling Center (EMC), previously the Climate Prediction
Center (CPC), is a component of the National Centers for Environmental
Prediction (NCEP).
2.0.6 Northwest Mexico NAME Event Raingage Network (NERN) Daily Data
"The NAME Event-Based raingage network (NERN) consists of 87 tipping
bucket raingages that have been installed in primarily east-west transects
across the Sierra Madre Occidental in Northwest Mexico. 50 gages were installed
in 2002 and 31 were installed in 2003 and 6 were installed in 2004. The
objectives of the network are to improve the sampling of precipitation at a
variety of elevations across the complex terrain of the Sierra Madre as well as
to provide event based data which permits the calculation of instantaneous rain
rates. Nearly 25% of the new event gages are collocated with existing manually
measured daily precipitation gages operated by the cooperative network of the
Comisión Nacional del Agua (CNA) of Mexico. Collocation permits
cross-validation, quality-control and helps to ensure the safety of the gages.
Detailed logs of the instruments, installation and downloading procedures, and
quality control information are distributed with each data archive submission
and are available from the investigators."
www.texaselectronics.com
www.onsetcomp.com"
5 min
15 min
30 min
1 hr
3 hr
12 hr
24 hr"
2.0.7 Daily Extract from NAME 2004 Precipitation Hourly Multi-Network Composite
Each daily precipitation incremental value in this dataset was formed
by summing the 24 hourly precipitation values extracted from each
NAME 2004 Hourly Precipitation Composite record. The hourly values
are summed from hour 0100 through hour 2400 (0000 UTC next day). The
value reported for any daily observation represents data collected
during the previous 24 hours.
This dataset is formed by extracting precipitation data from the
NAME 2004 Precipitation Hourly Multi-Network Composite .
2.1 Detailed Format Description
The NAME 2004 Precipitation Daily Multi-Network Composite contains six metadata
parameters and four data parameters. The metadata parameters describe the
station location and time at which the data were collected. The four data
parameters repeat once for each day in the monthly record. Every record has 31
days reported, regardless of the actual number of days in the month. For months
with less than 31 days, the extra days are reported as missing
(i.e., '-999.99 7 M'). Each 24 hour precipitation value has an associated
observation hour. The observation hour is the ending UTC hour for the 24 hour
period for which the precipitation value is valid. Data values are valid for
the 24 hours preceding the observation hour given for the day. A Quality Flag
and a Quality Control (QC) Code are assigned to each data value during gross limit
checking. For a list of possible Quality Flag and QC Code values see
the Quality Control section 3.0. The table below
details each parameter.
Parameters Units
---------------------- ----------------------------------
Date of Observation UTC
Time of Observation UTC
Network Identifier Abbreviation of platform name
Station Identifier Network Dependent
Latitude Decimal degrees, South is negative
Longitude Decimal degrees, West is negative
Station Occurrence Unitless
Hourly Precip Value Millimeters
Quality Flag See list of Definitions
QC Code See list of Definitions
Observation hour Ending UTC hour for 24 hour period
for which value is valid.
2.2 Data Remarks
Negative precipitation and values too large to be
represented in the output format were changed to missing
('-999.99') and were assigned the 'C' QC code.
3.0 Quality Control Processing
This precipitation composite was formed from several data
sources. Some of these datasets may have been Quality Controlled
independently by the data sources.
Section 2.0 Detailed Data Description
above indicates which data sources quality controlled their data sets
and whether or not the QC flags assigned by the data source were
carried forward into the NCAR/EOL QC formatted data.
If the QC flags assigned
by the data source are provided in the final composite data set, they
were not overwritten by any gross limit checking done at NCAR/EOL.
Table 1
Quality Control Flag Description
--------------------------- --------------------------------------------
0 No qualifier required
1 Accumulation period
2 End of Accumulation period
3 Deleted value. Original data was unreadable.
4 Trace of precipitation.
5 Probable amount as a result of melting frozen
precipitation.
6 Suspect amount relative to time or period of
occurrence.
7 Missing value
Table 2
QC Code Description
----------------- ------------------------------------------
U Unchecked
G Good
M Normally recorded but missing
D Questionable
B Unlikely
N Not available or Not observed.
X Glitch
E Estimated
C Reported value exceeds output format field
size or was negative precipitation.
T Trace precipitation amount recorded.
I Derived parameter can not be computed due
to insufficient data.
Table 3 - Precipitation Gross Limit Values
Parameter Good Questionable Unlikely
--------- ---- ------------ --------
Daily Precipitation < 180.0 mm >= 180.0 mm >= 220.0 mm
4.0 References
National Climatic Data Center, 1991: Surface Land Daily Cooperative;
Summary of the Day TD 3200. National Climatic Data Center, Asheville, NC, 25 pp.