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
University Corporation for Atmospheric Research/Joint Office for Science Support
(UCAR/JOSS) on this dataset. Section 4.0 contains
references.
2.0 Detailed Data Description
2.0.1 NCDC Fifteen Minute Precipitation Algorithms
The NCDC Fifteen Minute Precipitation dataset (TD 3260) is
formed by retaining both incremental and accumulative precipitation values
from the raw precipitation data. Both incremental and accumulative values
are contained in the BAMEX 2003 15-minute precipitation composite. If an
accumulation period began prior to but continued into the beginning of the
BAMEX 2003 time period, the precipitation values in that accumulation
period were reset to missing values. An accumulation period that began
near the end of the BAMEX 2003 time period, but continued after the end
of the BAMEX 2003 time period would also have its precipitation values
reset to missing. (NCDC, 1986)
2.0.2 15-Minute Precipitation extracted from the BAMEX 2003 Mesonet
1-Minute Surface Meteorological Composite
Each 15-minute precipitation incremental value in this dataset was
formed by summing the 1-minute precipitation values extracted from the
BAMEX 2003 Mesonet 1-Minute Surface Meteorological Composite. For
example,
the incremental value at 0015, is the sum of the 0001-0015 values from the
one minute surface data. The value reported at any 15-minute observation
represents data collected during the previous 15 minutes.
2.1 Detailed Format Description
The BAMEX 2003 Fifteen Minute Precipitation Composite contains
seven metadata parameters and three data parameters. The metadata
parameters describe the date/time, network, station and location at which
the data were collected. The three data parameters repeat once for each
fifteen minutes from UTC 0000 through UTC hour 2345. Data reported
for a designated 15-minute observation represents data collected during the
previous 15-minutes. All times are reported in UTC, and precipitation data
values are reported in millimeters. A Quality Flag and a QC Code are
assigned to each data value during the University Corporation for
Atmospheric Research/Joint Office for Science Support (UCAR/JOSS)
quality control processing. 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
15 Minute Precip Value Millimeters
Quality Flag See list of Definitions
QC Code See list of Definitions
Gross limit checks were used to determine the quality of the data in the BAMEX 2003 Fifteen Minute Precipitation Composite. Data values less than 12 millimeters were flagged as good. Any data value greater than or equal to 12 millimeters but less than 24 millimeters was flagged as questionable. Any data value greater than or equal to 24 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. The data were never changed, only flagged. Tables 1 and 2 contain the quality control codes and flags, respectively.
After the two datasets were merged to form the BAMEX 2003 Fifteen Minute Precipitation Composite, a statistics program was executed to ensure that the quality of the individual datasets had been retained.
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 precipitation value exceeds 9999.99
millimeters or was negative.
T Trace precipitation amount recorded.
I Derived parameter can not be computed due
to insufficient data.