Table of Contents - The Atmospheric Studies Group at TRC

Section 6: SMERGE Surface Data Meteorological Preprocessor
6. SMERGE SURFACE DATA METEOROLOGICAL PREPROCESSOR
SMERGE processes and reformats hourly surface observations, and creates either a formatted or an
unformatted file which is used as input by the CALMET model. It is assumed that the observations have
been validated by METSCAN (for CD144 formatted data) or similar utility. SMERGE reads "N" data
files containing surface data from the following formats: (1) NCDC 80-column format (CD144 format),
(2) NCDC Solar and Meteorological Surface Observational Network (SAMSON) CD-ROM format, (3)
NCDC Hourly U.S. Weather Observations (HUSWO) CD-ROM format, (4) NCDC’s ISHWO, Integrated
Surface Hourly Weather Observations, (5) NCDC’s TD-3505 data – Integrated Surface Hourly Data
(ISHD) format, (6) NCDC’s Air Force Datasav3 surface hourly data (TD-9956), (7) Generic data format
of the type comma delimited file which will process hourly observational data which is not of the form of
any of 1-6 above. Note that for (3) all parameters need to be extracted from the CD-ROM datasets, and
if the HUSWO CD-ROM data are used, they must be extracted using the “English” units options. Finally,
there is a further ‘stand-alone’ program, SURFCSV which will process any incremental time interval
from sub-hourly data to multi-hour data. This utility is not currently part of SMERGE and is discussed in
Section 6.1.2.
The output file (e.g., SURF.DAT) contains the processed hourly data for all the stations. SMERGE can
also add stations to an existing formatted or unformatted output file. A free-formatted SURF.DAT file
can be created by the user and read by CALMET. This option relieves the user of the need to run the
preprocessor for short CALMET runs for which the surface data can easily be input manually, or when
non-standard data sources (e.g., site-specific meteorological observations) are used.
SMERGE extracts the following variables from the NCDC surface data files: wind speed, wind direction,
air temperature, ceiling height, cloud cover, surface pressure, relative humidity, and precipitation type
code.
An option is provided to allow the surface data stored in the unformatted output file to be "packed."
Packing reduces the size of the data file by storing more than one variable in each word. If the packing
option is used, the eight hourly meteorological variables for each station are stored in three words:
Word 1: TTTTPCRRR -- TTTT = temp. (XXX.X deg. K)
PC
= precipitation code (XX)
RRR = relative humidity (XXX. %)
Word 2: pPPPPCCWWW -- pPPPP = station pressure (pXXX.X mb,
with p = 0 or 1 only)
CC
= opaque sky cover (XX tenths)
WWW = wind direction (XXX. deg.)
Word 3: HHHHSSSS -- HHHH = ceiling height (XXXX. hundreds
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