The Unidata Local Data Manager (LDM) (Unidata, 2002) distributes World Meteorological Organization (WMO) Surface data. These data are ingested by the University Corporation for Atmospheric Research/Joint Office for Science Support UCAR/JOSS in ASCII WMO meteorological message structure format (NOAA/NWS, 2002).
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: http://www.joss.ucar.edu/cgi-bin/codiac/dss?77.099 20 Iowa AWOS stations (ADU, AIO, AWG, CBF, CNC, CSQ, DNS, EOK, FFL, FSW, HNR, ICL, IKV, MPZ, MUT, OXV, PEA, RDK, SDA, TNU) had bad precipitation values. The correct values were calculated by UCAR/JOSS from 1 minute IOWA AWOS data obtained separately.
Message from Daryl Herzmann (email@example.com)
* Program Assistant -- Iowa Environmental Mesonet
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.
NOAA, National Weather Service, Automated Surface Observing System (ASOS), cited 2003: ASOS User's Guide [Available online from http://www.nws.noaa.gov/asos]
NOAA/NWS, cited 2002: WMO Message structure 2000 Paraphrased Version [Available from http://www.nws.noaa.gov/tg/head.html].
Unidata, Cited 2002: Unidata LDM [Available online from http://www.unidata.ucar.edu/packages/ldm/].