GCIP LSA-NW EAOP 2000 LDM WMO Surface "Specials" Data in QC format 1.0 General Description This dataset contains the Unidata Local Data Manager (LDM) World Meteorological Organization (WMO) Surface "Special" observation surface data in Quality Control (QC) format. Data for the GEWEX Continental-Scale International Project (GCIP) Large Scale Area-North West (LSA-NW) Enhanced Annual Observing Period (EAOP) 2000 domain (36N to 51N latitude and 90W to 115W longitude) and time period (01 April 2000 through 31 Mar 2001) are contained within this dataset. The LDM WMO "Nominal" hourly surface data in QC format for the GCIP LSA-NW EAOP 2000 domain and time period are provided as a separate dataset. These data were not quality controlled by the University Corporation for Atmospheric Research/Joint Office for Science Support (UCAR/JOSS). 2.0 Detailed Data Description The Unidata Local Data Manager (LDM) (Unidata, 2002) distributes World Meteorological Organization (WMO) Surface data. This data is ingested by UCAR/JOSS in ascii WMO meteorological message structure format (NOAA/NWS, 2002). 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. This dataset contains special data and METAR data that do not fall on the hour. Hourly METAR data are available separately by ordering the dataset "GCIP LSA-NW EAOP 2000 LDM WMO Hourly Surface Data in QC format". For information on the METAR format see the ASOS User's Guide, 1992. 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. 2.1 Detailed Format Description The GCIP LSA-NW EAOP-00 Surface "Special" observation data contains ten metadata parameters and 38 data parameters and flags. The metadata parameters describe the station location and time at which the data were collected. The time of observation is reported both in Universal Time Coordinated (UTC) Nominal and UTC actual time. For the GCIP LSA-NW EAOP 2000 "Specials", the UTC Nominal and UTC actual times are equal to the time of observation and are always identical. Days begin at UTC hour 0100 and end at UTC hour 0000 the following day. The data parameters are valid for the reported times. Missing values are reported as 9's in the data field. The table below details the data parameters in each record. Several data parameters have an associated Quality Control (QC) Flag Code which are assigned by the Joint Office for Science Support (JOSS). For a list of possible QC Flag values see the Quality Control Section 3.0. No additional QC was performed by UCAR/JOSS. Parameters Units ---------- ----- Date of Observation UTC Nominal Time of Observation UTC Nominal Date of Observation UTC actual Time of Observation UTC actual 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 Station Elevation Meters Station Pressure, QC flag Hectopascals (mb) Reported Sea Level Pressure, QC flag Hectopascals (mb) Computed Sea Level Pressure, QC flag Hectopascals (mb) Dry Bulb Temperature, QC flag Celsius Dew Point, QC flag Celsius Wind Speed, QC flag m/s Wind Direction, QC flag Degrees Total Precipitation, QC flag mm Squall/Gust Indicator Code Value Squall/Gust Value, QC flag m/s Present Weather, QC flag Code Value Visibility, QC flag Meters Ceiling Height (first layer) Hundreds of feet Ceiling Flag (first layer), QC flag Code Value Cloud Amount (first layer), QC flag Code Value Ceiling Height (second layer) Hundreds of feet Ceiling Flag (second layer), QC flag Code Value Cloud Amount (second layer), QC flag Code Value Ceiling Height (third layer) Hundreds of feet Ceiling Flag (third layer), QC flag Code Value Cloud Amount (third layer), QC flag Code Value The list of code values for the Present Weather is too large to reproduce in this document. Refer to WMO, 1988 for a complete list of Present Weather codes. The code values for the Squall/Gust Indicator are: Code Definition ---- ---------- blank No Squall or Gust S Squall G Gust The code values for the Ceiling Flag Indicator are: Code Definition ---- ---------- 0 None 1 Thin 2 Clear below 12,000 feet 3 Estimated 4 Measured 5 Indefinite 6 Balloon 7 Aircraft 8 Measured/Variable 9 Clear below 6,000 feet (AUTOB) 10 Estimated / Variable 11 Indefinite / Variable 12 12-14 reserved 15 Missing The code values for the Cloud Amount Indicator are: Code Definition ---- ---------- 0 0 ( or clear) 1 1 okta or less, but not zero or 1/10 or less, but not zero 2 2 oktas or 2/10-3/10 3 3 oktas or 4/10 4 4 oktas or 5/10 5 5 oktas or 6/10 6 6 oktas or 7/10-8/10 7 7 oktas or more, but no 8 oktas or 9/10 or more, but not 10/10 8 8 oktas or 10/10 (or overcast) 9 Sky obscured by fog and/or other meteorological phenomena 10 Sky partially obscured by fog and/or other meteorological phenomena 11 Scattered 12 Broken 13 13-14 Reserved 15 Cloud cover is indiscernible for reasons other than fog or other meteorological phenomena, or observation is not made. 2.2 Data Remarks This dataset contains the GCIP LSA-NW EAOP 2000 LDM WMO Surface "Special" observation data. The GCIP LSA-NW EAOP 2000 LDM WMO Hourly Surface data contains only the "Nominal" hourly observations for the GCIP LSA-NW EAOP 2000 domain and time period. When not present in the raw data, the dewpoint is computed using the formula from Bolton (1980). Calculated Sea Level pressure is computed from station pressure, temperature, dewpoint, and station elevation using the formula of Wallace and Hobbs (1977). 3.0 Quality Control Processing This data was not quality controlled by UCAR/JOSS. The possible quality control flags are listed in Table 3.1 below. Table 3-1 - Quality Control Flags 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 value exceeds output format field size or was negative precipitation. T Trace precipitation amount recorded I Derived parameter can not be computed due to insufficient data. 4.0 References ASOS User's Guide, ASOS Project Office, NOAA, National Weather Service, Washington D.C., June 1992. Bolton, D., 1980: The computation of equivalent potential temperature., Mon. Wea. Rev., 108, pp 1046-1053. 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/] Wallace, J.M., P.V. Hobbs, 1977: Atmospheric Science, Academic Press, 467 pp. World Meteorological Organization (WMO), 1988: Manual on Codes Volume I, Part B - Binary Codes. WMO, Geneva, Switzerland.