File: README.TXT Weather Station Data Files Center for Exposure Assessment Modeling (CEAM) National Exposure Research Laboratory - Ecosystems Research Division Office of Research and Development (ORD) U.S. Environmental Protection Agency (U.S. EPA) 960 College Station Road Athens, Georgia 30605-2700 706/355-8400 _____________________________________________________________________________ CONTENTS INTRODUCTION DOCUMENTATION INSTALLATION FILE SPECIFICATION CONTACT INFORMATION _____________________________________________________________________________ INTRODUCTION The Weather Station Data Files contain meteorological data measured at 237 U.S. Weather stations for a period extending nominally from 1961 to 1990. Exact collection dates vary by weather station. The files can be used with the U.S. EPA PRZM and EXAMS models. Each data set contains one "Daily Values File" (.DVF), several "Hourly" values files (.Hnn), and one format file (.TXT). _____________________________________________________________________________ DOCUMENTATION ABSTRACT.TXT Summary of data use and applicability. STATION LOCATIONS.PDF List of the available Weather stations. STATION NOTES.PDF Additional detail on station data sources. CITY MAP.PDF Map of station locations with station city names. MLRA-WBAN.PDF Map of station locations overlaid on MLRA. LEGEND.PDF Key to Land Resource Regions (for use with MLRA_WBAN.PDF). MLRA-CODES.PDF Key to MLRA descriptive titles (for use with MLRA-WBAN.PDF). _____________________________________________________________________________ INSTALLATION Weather Station Data Files contain the recorded weather data for 237 meteorological stations. All executable (.exe) files were compressed using a registered copy of WinZip Self-Extractor. No other software is needed to extract the data. Each file can be decompressed or "unzipped" by simply double-clicking the file name in Windows Explorer or My Computer. The WinZip Self-Extractor user interface will allow you to extract the data files to a local or network directory of your choice. The default target directory is C:\metdata. Approximately 45 MB of available disk space is required to decompress each self-extracting weather station data set. _____________________________________________________________________________ FILE SPECIFICATION When decompressed, the data files are stored as ASCII text (non-binary) files and have the DOS file name extension "*.dvf" for daily values file, or "*.hnn" for hourly values file. The hourly data files contain recorded meteorological data from the following sources: #1. Solar and Meteorological Surface Observation Network (SAMSON) 1961-1990 data sets, Version 1.0, Sep 1993 #2. National Solar Radiation Data base (NSRDB) version 1.1; NSRDB Hourly Data Files Text files downloaded from http://rredc.nrel.gov/solar/old_data/nsrdb/hourly/ -- provided updated radiation parameters. #3. EarthInfo NCDC Summary of the Day and Surface Airways, 2001 -- provided daily and hourly values for precipitation, and daily evaporation. Missing evaporation was calculated using the Kohler-Nordenson-Fox Class-A Evaporation Pan version of the Penman- Monteith equations. #4. Evapotranspiration (Et0) formulae based on: Crop Evapotranspiration - Guidelines for Computing Crop water requirements. FAO Irrigation and Drainage Paper 56 by Richard G. Allen, Luis S. Pereira, Dirk Raes, and Martin Smith. Water Resources, Development and Management Service, FAO - Food and Agriculture Organization of the United Nations, Rome, 1998. ISBN 92-5-104219-5. This book may be found online at http://www.fao.org/docrep/X0490E/x0490e00.htm Each directory contains "Hourly" values files (*.hnn), a "Daily Values File" (*.dvf), and a format file (*.txt). The name of the file is of the form "wnnnnn", where "nnnnn" represents the WBAN (Weather Bureau Army Navy) identification number of the weather station. For more information on WBAN numbers see http://lwf.ncdc.noaa.gov/oa/climate/stationlocator.html Gaps in the hourly data record were filled according to methods described in National Solar Radiation Data Base User's Manual (1961-1990), NSRDB Volume 1, September 1991, Section 5.2.1. The document may be downloaded from http://rredc.nrel.gov/solar/pubs/NSRDB/NSRDB_index.html. In general, #1. Gaps of less than 6 hours were filled by linear interpolation between points at both sides of the gap. #2. Gaps of 6 hours to 49 hours were filled by copying data from the previous (or following) day. #3. Longer gaps of 50 hours to 8784 hours (one leap year) were filled by copying data for the same period from some other year. The daily values were obtained by computing the mean over 24 hours, or by adding the values over one day, as appropriate. PRZM and EXAMS can use the "Daily Values File" data files (*.dvf). All decompressed, "Daily Values File" data files (*.dvf) have the following format: Field Columns Description Units Type Format ----- -------- ---------------------- --------------- --------- ------ 1 1 blank N/A Character 1x 2 02 - 07 Date mmddyy Integer 3i2 3 08 - 17 Precipitation cm/day Real f10.2 4 18 - 27 Pan Evaporation cm/day Real f10.2 5 28 - 37 Temperature (mean) degrees Centigrade Real f10.1 6 38 - 47 Wind Speed @10 meter cm/second Real f10.1 7 48 - 57 Solar Radiation Langleys/day Real f10.1 8 58 - 63 FAO Short Grass Eto mm/day Real f6.1 9 64 - 73 Daylight Station kiloPascal Real f10.1 Pressure 10 74 - 77 Daylight Relative percent Integer i4 Humidity 11 78 - 80 Daylight Opaque tenths of sky covered Integer i3 Sky Cover 12 81 - 90 Daylight Temperature degrees Centigrade Real f10.1 13 91 - 96 Daylight Broadband optical depth Real f6.3 Aerosol 14 97 -102 Daylight Prevailing meter/second Real f6.1 Wind Speed @10 meter 15 103 -106 Daylight Prevailing degrees (N=0, E=90, ...) Integer i4 Wind Direction Daily values file format: (1x,3i2, t8,f10.2, t18,f10.2, t28,f10.1, t38,f10.1, & t48,f10.1, t58,f6.1, t64,f10.1, t74,i4, t78,i3, & t81,f10.1, t91,f6.3, t97,f6.1, t103,i4) Fields 03 - 08 represent daily totals or mean values (Wind Speed and Temperature) Fields 03 - 07 units preserved from earlier PRZM met files for compatibility Fields 09 - 15 represent mean values for daylight hours only. Hourly values files (*.hnn) contain hourly data for the year 19nn. For example, w25501.h65 contains 1965 hourly data for Kodiak, AK. The hourly values file has a header containing identifying information. Example: 25501 Kodiak AK +9 N 57 45 W 152 30 5 2002-05-17 22:47:31 Header Field Columns Description Type Format ----- ------- ---------------------- --------- ------ 1 1 blank Character 1x 2 02 - 06 WBAN id Character a5 3 08 - 37 City where the Character a30 station is located. 4 39 - 40 State where the Character a2 station is located. 5 42 - 44 Time Zone Character a3 6 47 - 54 Latitude of the station 47 - 47 N: North of the Equator Character a1 S: South 48 - 51 Degrees Integer i4 53 - 54 Minutes Integer i2 7 57 - 64 Longitude of the station 57 - 57 W: West Character a1 E: East 58 - 61 Degrees Integer i4 63 - 64 Minutes Integer i2 8 67 - 70 Station Elevation(meter) Integer i4 9 74 - 92 Generation date of the Character a19 file, i.e, yyyy-mm-dd hh:mm:ss where yyyy: year mm: month dd: day of the month hh: hour (24-hour clock) mm: minutes ss: seconds Header format: (1x, a5, 1x, a30, 1x, a2, 1x, a3, & 2x, a1, i4, 1x, i2, & 2x, a1, i4, 1x, i2, & 2x, i4, 3x, a19) Field Columns Description Units Type Format ----- --------- ---------------------- --------------- --------- ------ 1 1 blank N/A Character 1x 2 002 - 011 Date yyyy-mm-dd Integer i4,1x,i2,1x,i2 3 012 - 014 *Hour of the day Hour Integer i3 4 016 - 021 Extraterrestrial *Wh/m2 Integer i5,a1 Horizontal Radiation (Ra) 5 023 - 028 Extraterrestrial Wh/m2 Integer i5,a1 Direct Normal Radiation 6 030 - 037 Global Horizontal Wh/m2 Integer i5,a3 Radiation (Rs) 7 039 - 046 Direct Normal Wh/m2 Integer i5,a3 Radiation 8 048 - 055 Diffuse Horizontal Wh/m2 Integer i5,a3 Radiation 9 057 - 059 Total Sky Cover tenths of sky covered Integer i2,a1 10 061 - 063 Opaque_Sky_Cover tenths of sky covered Integer i2,a1 11 065 - 070 Dry Bulb Temperature degrees Centigrade Real f5.1,a1 12 072 - 077 Dew Point Temperature degrees Centigrade Real f5.1,a1 13 079 - 082 Relative_Humidity percent Integer i3,a1 14 084 - 089 Station_Pressure *kPa Real f5.1,a1 15 091 - 094 Wind_Direction degrees(N=0,E=90,...) Integer i3,a1 16 096 - 101 Wind_Speed @10meter m/s Real f5.1,a1 17 103 - 109 Horizontal Visibility km Real f6.1,a1 18 111 - 117 Ceiling Height m Integer i6,a1 19 119 - 120 Observation Indicator N/A Integer i1,a1 20 122 - 131 Present_weather N/A Character a9,a1 21 133 - 136 Precipitable Water mm Integer i3,a1 22 138 - 144 Broadband Aerosol Optical_Depth Real f6.3,a1 23 146 - 150 Snow Depth cm Integer i4,a1 24 152 - 155 Days since last day Integer i3,a1 Snowfall 25 157 - 164 Hourly Precipitation cm Real f6.2,a2 26 166 - 172 Eto, FAO Short Grass mm/day Real f6.2,a1 27 174 - 180 Ep, Class A pan mm/day Real f6.2,a1 Evaporation *Hour of the day: The range of the hour of the day is 1h to 25h: 1h-24h: line contains data for the hour 25: line contains daily values *Wh/m2: Watt hour meter^-2 Watt hour meter^-2 is equivalent to 3.6e-3 MJoule meter^-2 Watt hour meter^-2 is equivalent to 8.59845e-02 Langley *kPa: kiloPascal 1 kiloPascal is equivalent to 10 millibar Fields 26 and 27 represent daily totals. These fields are present only when the hour of the day (field 3) is 25. Generally, each value has one or more character flags associated with it. When possible, the flags associated with the original datum are copied to the Hourly Values File (*.hnn). 'W' = Measured value (SAMSON flag) 'B' = Calibrated (SAMSON flag) 'D' = Deleted (SAMSON flag) 'E' = Estimated. '-' = Missing value 'R' = Datum from EarthInfo data 2001 'S' = Datum from SAMSON version 1.0 'T' = Datum from SAMSON version 1.1 'U' = Unlimited in Visibility or Ceiling Height or Short-gap interpolation with either of the endpoints being Unlimited or Cirroform. 'Z' = Cirroform in Ceiling Height data '?' = Value is undefined, given the context, e.g., Dew point is undefined if the Relative Humidity is zero. '#' = If the station is above the Arctic Circle (Latitude 66.5 degrees North), then the region will be in darkness for a period of the year. This prevents the computation of, e.g., Daylight value of Global Horizontal Radiation and Reference Crop Evapotranspiration (Eto) 'A' = Accumulation (SAMSON flag). The precipitation is distributed in the observation interval. Missing values are denoted by '---' in the numeric value field and flag value of '-' Hourly values file format: (1x,i4,1x,i2,1x,i2, i3, t16,i5,a1, t23,i5,a1, & t30,i5,a3, t39,i5,a3, t48,i5,a3, & t57,i2,a1, t61,i2,a1, t65,f5.1,a1, t72,f5.1,a1, & t79,i3,a1, t84,f5.1,a1, t91,i3,a1, t96,f5.1,a1, & t103,f6.1,a1, t111,i6,a1, t119,i1,a1, t122,a9,a1, & t133,i3,a1, t138,f6.3,a1, t146,i4,a1, t152,i3,a1, & t157,f6.2,a2, t166,f6.2,a1, t174,f6.2,a1) _____________________________________________________________________________ CONTACT INFORMATION For information concerning installation of the Weather Station Data Files, contact the Center for Exposure Assessment Modeling (CEAM): phone: 706/355-8400 fax: 706/355-8104 email: ceam@epamail.epa.gov mail: Center for Exposure Assessment Modeling (CEAM) National Exposure Research Laboratory - Ecosystems Research Division U.S. Environmental Protection Agency (U.S. EPA) 960 College Station Road Athens, Georgia 30605-2700 CEAM software products and their status are available through the World Wide Web (WWW) at the following Uniform Resource Locator (URL): http://www.epa.gov/ceampubl/ _____________________________________________________________________________