Unidata Local Data Manager (LDM) World Meteorological Organization (WMO) (LDMSFCMETR) Algorithms

1.0 General Description

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).

2.0 Detailed Data Description

This dataset contains ASOS, AWOS, and MANUAL stations. Station ID's are 3 characters long. Some networks use the 4-character ID to refer to these stations. To obtain the 4-character id, prepend a "K". For example, station ABR could also be referred to as station KABR.

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 (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.

2.1 Detailed Format Description

The primary feedset name is "WMO" which includes Public Product Service (PPS), Domestic Data Service (DDS), High resolution Data Service (HDS), and International Data Service (IDS) feedtypes. Only products that match the patterns ^S[AP].* .... ([0-3][0-9])([0-2][0-9]) and ^SX..81 .... ([0-3][0-9])([0-2][0-9]) are collected. In these patterns, S stands for surface, A for Aviation Routine Reports (FM 15 - METAR), P for Special aviation weather reports (FM 16 - SPECI), and X for miscellaneous text records. For information on the METAR format see the ASOS User's Guide ( NOAA, 2003).

3.0 Quality Control Processing

This dataset was not quality controlled by UCAR/JOSS.

4.0 References

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/].