Lake-ICE Surface "Specials" Dataset 1.0 General Description This dataset contains the Automated Surface Observing System (ASOS) and National Climatic Data Center (NCDC) Surface Climatic Database (DATSAV2) "Special" observation surface data. Data for the Lake-Induced Convection Experiment (Lake-ICE) domain (37N to 55N latitude and 73W to 104W longitude) and time period (28 November 1997 through 25 January 1998) are contained within this dataset. The ASOS and DATSAV2 "Nominal" hourly surface data for the Lake-ICE domain and time period are included in the Lake-ICE Hourly Surface Composite. This Lake-ICE Surface "Specials" dataset contains data from 781 stations and is similar in format, etc. to the data in the Lake-ICE Hourly Surface Composite. No additional QC was performed by the University Corporation for Atmospheric Research/JOSS. 2.0 Detailed Data Description 2.0.1 Automated Surface Observing System (ASOS) Algorithms The following are descriptions of the algorithms used by ASOS to produce hourly surface data. These algorithms were also used to generate the ASOS specials. Complete details may be found in the ASOS User's Guide (1992). The ASOS hourly values were produced from ASOS 5-minute data by extracting all parameters (except precipitation) from the 55-minute observation of the previous hour and assigning those values to the current hourly observation. The precipitation is the sum of the precipitation values from the 05-minute of the previous hour through the 00-minute of the current hour. The descriptions of the algorithms used by ASOS to produce five minute surface data are given in the Lake-ICE 5-Minute Surface Composite description document. Specials occuring in the 5-Minute ASOS data have been archived at JOSS and are available by request. 2.0.2 National Climatic Data Center (NCDC) DATSAV2 Algorithms The NCDC DATSAV2 Surface Database is composed of worldwide surface weather observations collected and stored from several sources (including from Global Telecommunications System (GTS)) since 1973. Most collected observations are decoded at the Air Force Global Weather Central (AFGWC) then sent to the United States Air Force Environmental Technical applications Center's Operating Location A (OL-A) at Asheville, North Carolina. At OL-A the observations are processed into the DATSAV2 Surface Database format for database storage. DATSAV2 refers to the digital tape format in which decoded weather observations are stored at OL-A. DATSAV2 is the official climatological database for surface observations such as synoptic, airways, Meteorological Aviation Routine Weather Reports (METAR), Aviation Routine Weather Report (AERO), Supplementary Marine Reporting Station (SMARS), as well as observations from automatic weather stations. OL-A sorts the observations into station-date-time order, and validates each block-station number against the Air Weather Service Master Station Catalog (AWSMSC). OL-A merges and sorts the data into monthly and yearly station-ordered files and processes the data through several quality control programs. For more information about the DATSAV2 format and the quality control performed on this data see USAF, 1986. 2.1 Detailed Format Description The Lake-ICE 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 Lake-ICE "Specials", the UTC Nominal and UTC actual times are equal to the time of observation and are always identical. Days begin at UTC 0100 and end at UTC 0000 the following day. The table below details the data parameter 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 Lake-ICE Surface "Special" observation data. The Lake-ICE Hourly Surface Composite contains only the "Nominal" hourly observations for the Lake-ICE data. Specials occuring in the 5-Minute ASOS data have been archived at JOSS and are available by request. 3.0 Quality Control Processing The DATSAV2 portion of this dataset was quality controlled by OL-A. For more information about the DATSAV2 format and the quality control performed see USAF, 1986. No additional QC was performed 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. United States Air Force Environmental Technical Applications Center OL-A, 1986: USAFETAC Climatic Database Users Handbook No. 4. United States Air Force, Asheville, N.C., December 1986. World Meteorological Organization (WMO), 1988: Manual on Codes Volume I, Part B - Binary Codes. WMO, Geneva, Switzerland.