TITLE: Mesonet GTS Surface Hourly Observations [JOSS]


Steve Williams
P.O. Box 3000
Boulder CO 80307-3000
email: sfw@ucar.edu
phone: 303-497-8987

1.0  General Description

The GTS Surface Hourly Observation Data is one of several surface
data sets collected by the University Corporation for Atmospheric
Research/Joint Office for Science Support (UCAR/JOSS) as part of 
the IHOP 2002 project.  Included in the data set are the global 
hourly (and special) surface observations.  These data are 
contained in daily files which are in GEMPAK format.  It may not 
contain data which was removed from the US GTS feed.  The data 
cover the period from 13 May to 25 June 2002.  The data were 
acquired via the UNIDATA Local Data Manager (LDM). 

2.0  Data and Format Information

2.1  GEMPAK Format

GEMPAK, the GEneral Meteorology PAcKage, is a suite of 
applications programs, libraries, graphic routines, and device 
drivers for the decoding, analysis, display and diagnosis of 
geo-referenced and meteorological data. GEMPAK provides a 
comprehensive set of meteorological parameter calculations for 
surface, upper-air, gridded, and remotely sensed data. 

GEMPAK was originally developed by the Severe Storms Laboratory 
at the Goddard Space Flight Center of NASA starting in the early 
1980's. GEMPAK is currently being developed within the National
Weather Service (NWS) by the National Centers for Environmental
Prediction (NCEP). 

For information on GEMPAK see:


2.2  Precipitation data from Iowa AWOS stations

Note the following problem with precipitation observations from Iowa 
AWOS stations.  The 1-min Iowa AWOS data are available from UCAR/JOSS
for the IHOP period at:

Message from Daryl Herzmann (akrherz@iastate.edu)
 * Program Assistant -- Iowa Environmental Mesonet
 * http://mesonet.agron.iastate.edu
Sent 10 April 2003:

Anyway, most (not all) of these stations are outfitted with tipping
buckets.  All of you have been receiving the AWOS precipitation amounts
from the raw METARs, but up until today, there has been a fundamental flaw
with the observations.  The site resets the hourly precipitation counter
at :55 after the hour, but METARs were only relayed at :05, :25 and :45
after the hour.  This would result in 10 minutes of missing
potential rainfall data every hour.

The Iowa Department of Transportation sends us their 1 minute interval
data archive from the network at the end of every month.  While looking at
this dataset, I noticed this timing problem last summer.  The Des Moines
WFO and the Iowa Mesonet have been working closely with the DOT to get
this problem resolved.  And today it has been.  The Iowa AWOS sites are
now reporting at :15, :35 and :55 after the hour, which eliminates the
timing issue.

3.0  Quality Control Procedures

     UCAR/JOSS conducted no quality checks on these data.

4.0  File Naming Convention


sa is the data type hourly sao
yyyy is the four digit year
mm is the two digit month
dd is the two digit day (UTC)

5.0  References