CASES 1999 National Climatic Data Center (NCDC) DATSAV3 Dataset 1.0 General Description The National Climatic Data Center (NCDC) Surface Climatic Database (DATSAV3) Dataset is one of several surface datasets provided for the Cooperative Atmospheric Surface Exchange Study October 1999 (CASES 1999) project. This NCDC DATSAV3 dataset contains data from seven stations within the CASES 1999 time period (25 September 1999 through 5 November 1999) and in the CASES 1999 domain (approximately 95.7438W to 97.7438W longitude and 36.6501N to 38.6501N latitude). 2.0 Detailed Data Description National Climatic Data Center (NCDC) DATSAV3 Algorithms The University Corporation for Atmospheric Research/Joint Office for Science Support (UCAR/JOSS) was given data in the NCDC Surface Hourly Abbreviated Format, which is derived by NCDC from their DATSAV3 formatted data. This "Abbreviated" format data was used by UCAR/JOSS to produce hourly surface data. These data were also used to generate the surface CASES99 "Specials" dataset. The following are descriptions of the algorithms used by NCDC to produce their NCDC DATSAV3 formatted data. The NCDC DATSAV3 Surface Database is composed of worldwide surface weather observations from about 10,000 currently active stations, collected and stored from several sources such as the Automated Weather Network (AWN) and the Global Telecommunications System (GTS). Most collected observations are decoded at the Air Force Global Weather Central (AFGWC) at Offutt Air Force Base (AFB), Nebraska, and then sent electronically to the United States Air Force (USAF) Combat Climatology Center (AFCCC), collocated with NCDC in the Federal Climate Complex in Asheville, North Carolina. AFCCC builds the final database through decode, validation, and quality control software. All data are stored in a single ASCII format. The database is used in climatological applications by numerous Department of Defense (DoD) and civilian customers. DATSAV3 refers to the digital tape format in which decoded weather observations are stored. The DATSAV3 format conforms to Federal Information Processing Standards (FIPS). The DATSAV3 database includes data originating from various codes such as synoptic, airways, Meteorological Aviation Routine Weather Reports (METAR), and Supplementary Marine Reporting Station (SMARS), as well as observations from automatic weather stations. The users handbook provides complete documentation for the database and its format. AFCCC sorts the observations into station-date-time order, validates each station number against the Air Weather Service Master Station Catalog (AWSMSC), runs several quality control programs, and then merges and sorts the data further into monthly and yearly station-ordered files. AFCCC then provides the data to the collocated National Climatic Data Center (NCDC). For more information about the DATSAV3 format and the quality control performed on this data see NCDC, 1999a. For more information on the Abbreviated Format see NCDC, 1999b. UCAR/JOSS converts the DATSAV3 altimeter reading to station pressure using the information from Smithsonian Meteorological Tables, 1949. 2.1 Detailed Format Description The National Climatic Data Center (NCDC) DATSAV3 Hourly Surface Dataset 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. 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 is 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 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). This dataset contains only the "nominal" records for the DATSAV3 datasets. The special records for the DATSAV3 dataset are located in the CASES99 "Specials" Dataset. 3.0 Quality Control Processing This dataset was quality controlled by AFCCC. For more information about the DATSAV3 format and the quality control performed see NCDC, 1999a. 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 Bolton, D., 1980: The computation of equivalent potential temperature., Mon. Wea. Rev., 108, pp 1046-1053. National Climatic Data Center, 1999a: Data documentation for DATSAV3 surface, TD-9956, April 20, 1999, National Climatic Data Center, 151 Patton Ave, Asheville, NC 28801-5001 USA. National Climatic Data Center, 1999b: Surface Hourly Abbreviated Format, 09/02/99 National Climatic Data Center, 151 Patton Ave, Asheville, NC 28801-5001 USA. Smithsonian Meteorological Tables, Table No. 65, p.269. Smithsonian Institution Press, Washington, D.C., September, 1949. 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.