Langley DAAC Version Number: LD_xxxxxxxx FIRE_ACE_C130_RAMS Readme File 1.0 Introduction This file contains information about the data provided by Scripps' Radiation Measurement System (RAMS) flown onboard the NCAR C-130 aircraft during the FIRE ACE field campaign. Additional information about the RAMS data set and preliminary quicklook images are available from the project home page: http://cloud.ucsd.edu The document also includes the following sections: Section 2.0 - Data Set Description Section 3.0 - Data Format and Packaging Section 4.0 - Science Parameter Information Section 5.0 - Description of Sample Read Software Section 6.0 - Implementing Sample Read Software Section 7.0 - Sample Output Section 8.0 - References For any questions regarding this file or the sample read software, please contact the Langley DAAC Science, Users and Data Services Office at: EOSDIS Langley DAAC Science, Users and Data Services Office NASA Langley Research Center Mail Stop 157D 2 South Wright Street Hampton, Virginia 23681-2199 U.S.A. Email: larc@eos.nasa.gov Phone: (757)864-8656 FAX: (757)864-8807 URL: http://eosweb.larc.nasa.gov 2.0 Data Set Description This data set consists of radiant flux measurements collected by four different radiometers mounted on the NCAR C-130. Data were collected on flights that took place at least once per week May 4-28, 1998 and July 8-29, 1998 departing from Fairbanks, Alaska. 2.1 Instrumentation Description Total Solar Broadband Radiometers (TSBR) have an effective bandwidth covering the spectral range from 0.224 to 3.91 microns. Infrared Broadband Radiometers (IRBR) have an effective bandwidth covering the spectral range from 4.125 to 48.25 microns. The Total-Direct-Diffuse Radiometer (TDDR) and Multi-Channel Radiometer (MCRV) each have seven narrowband spectral channels centered at 500, 425, 475, 525, 575, 625, and 675 nm with corresponding square bandpasses of 10, 50, 50, 50, 50, 50, and 50 nm. These radiometers all have hemispherical fields-of-view. A TSBR, IRBR, and TDDR were mounted on the top of the C-130, while a TSBR, IRBR, and MCRV were mounted on the bottom of the aircraft. The zenith TDDR has a shadow band that continually scans back and forth over the aperture of the instrument periodically occulting the sun. 2.2 Data Quality Data have been removed during extreme ascents and decents and where the aircraft roll angle exceeds approximately 3-4 degrees. Data were also previewed for unphysical quantities. 2.3 Science Contacts Data Set Contact: Brett C. Bush 9500 Gilman Dr. Dept 0242, Atmospheric Research Laboratory Scripps Institution of Oceanography University of California, San Diego La Jolla, CA 92093-0242 USA Email: fvalero@ucsd.edu Phone: (619) 822-0514 FAX: (619) 822-0517 Principle Investigator: Francisco P.J. Valero 9500 Gilman Dr. Dept 0242, Atmospheric Research Laboratory Scripps Institution of Oceanography University of California, San Diego, La Jolla, CA 92093-0242 USA Phone: (619) 534-2701 FAX: (619) 822-0517 Email: fvalero@ucsd.edu 3.0 Data Format and Packaging RAMS data are distributed in zip files. Each zip file contains two RAMS data files and a navigation file for one flight. Upwelling and downwelling broadband and infrared radiometric measurements are contained in the *bbr* file. Upwelling and downwelling narrowband (7 channels) radiometric spectral measurements are contained in the *tddr* file. To read the files, first unzip them with Info-Zip software. Information about downloading and using this freeware is available at the following URL: http://www.cdrom.com/pub/infozip/ All data files are in NetCDF format. Further information about NetCDF(network Common Data Form) can be found at the UNIDATA web site: http://www.unidata.ucar.edu/packages/netcdf/. 3.1 File Naming Convention The zip files are named for the day on which the flight took place. For example, fire_ace_rams_19980708.zip contains the data collected on the July 7, 1998 flight. When this file is unzipped it produces three files with a total size approximately double the size of the original zip file. The files produced are fire_ace_rams_bbr_19980708.cdf, fire_ace_rams_tddr_19980708.cdf and fire_ace_c130_nav_19980708.cdf. The first file contains the broadband fluxes and the second file contains the narrowband fluxes. The third file contains the navigational parameters as provided by NCAR. 4.0 Science Parameter Information The science parameters are described in the table below. All fluxes are expressed in watts per meter squared. Parameter Fill Min Max Instrument File --------- ---- --- --- ---------- ---- Downwelling Total Solar Flux -99999. 0 1400 TSBR bbr Upwelling Total Solar Flux -99999. 0 1400 TSBR bbr Downwelling Infrared Flux -99999. 0 600 IRBR bbr Upwelling Infrared Flux -99999. 0 600 IRBR bbr Downwelling Narrowband Flux -99999. 0 100 TDDR tddr Upwelling Narrowband Flux -99999. 0 100 MCRV tddr Base time -99999. 0 --- ---- all time offset -99999. 0 --- ---- all time -99999. 0 --- ---- all GPS Latitude -32767. -90 90 ---- nav GPS Longitude -32767. -180 180 ---- nav Geometric Altitude (radar) -32767. 0 --- ---- nav Inertial Altitude -32767. 0 --- ---- nav inertial Latitude -32767. -90 90 ---- nav Inertial Longitude -32767. -180 180 ---- nav NACA pressure Altitude -32767. 0 --- ---- nav Aircraft Pitch Angle -32767. -180 180 ---- nav Aircraft Roll Angle -32767. -180 180 ---- nav True Heading -32767. 0 360 ---- nav For instrument descriptions see section 2.1; for file name descriptions see section 3.1. All times are in seconds and are referenced to a base time. The navigational parameters in the *nav* files were extracted from the NCAR C-130, low rate navigation files. The complete SHEBA project data files are available from the following URL: http://raf.atd.ucar.edu. 5.0 Description of Sample Read Software An IDL procedure called read_fire_ace_c130_rams.pro is provided to read RAMS data. The program reads either the tddr or the bbr file, along with the navigational data, for one flight. It prints every 10000th value to the screen. When the program is run, the user selects whether tddr or bbr files are to be read. A dialog box then displays the data file names for user selection. The dialog box is created with a call to the dialog_pickfile procedure which assumes that the data files are in the current working directory. The "Path" parameter in the call to dialog_pickfile may be modified to specify an alternative data directory. Just below the call to dialog_pickfile, a string variable, called navPath, is set to specify the directory which contains the navigation files. The navPath variable is also initially set to the current working directory. After the data file is selected and read, the procedure constructs the navigation file name based on the date taken from the data file name and the navPath variable. If the filenames are changed, the procedure will not be able to find the correct navigation file. The procedure finds the matching navigation record for every 10000th data point, using the base times and time offsets, and outputs the values to the screen. 6.0 Implementing Sample Read Software The file read_fire_ace_c130_rams.pro contains several procedures, so the entire file must be compiled before it can be run. To do this, the user must first start up idl by typing "idl". At the IDL prompt, type ".compile read_fire_ace_c130_rams", then type the program name, "read_fire_ace_c130_rams" to start the program Alternatively, the IDL development environment can be used. To start IDL this way, type "idlde" at the prompt. Under file, choose "open" and then select the file read_fire_ace_c130.pro. Under Run, choose "compile read_fire_ace_c130_rams.pro". Finally, under Run, choose "run read_fire_ace_c130_rams". 7.0 Sample Output Example of bbr file read ------------------------ IDL> .COMPILE read_fire_ace_c130_rams.pro % Compiled module: READ_FIRE_ACE_C130_RAMS. % Compiled module: READ_RAMS_BBR. % Compiled module: READ_RAMS_TDDR. IDL> read_fire_ace_c130_rams Enter "1" to read broadband data (bbr), or "2" for multi-channel narrowband radiometers (tddr) 1 fire_ace_rams_bbr_19980723.cdf START DATE: 23 Jul 1998 % Compiled module: STR_SEP. fire_ace_c130_nav_19980723.cdf Date Time Alt Lat Lon Zentsbrflux Nadtsbrflux Zenirbrflux Nadirbrflux -------------------------------------------------------------------------------------------------------------- 23 Jul 1998 18:27:37 6175.11 65.97 -150.01 683.31 415.46 164.03 -99999 23 Jul 1998 21:26:09 403.08 78.43 -166.00 472.92 291.75 -99999.00 327.2 24 Jul 1998 00:19:18 134.08 77.33 -160.95 502.28 195.44 -99999.00 -99999 24 Jul 1998 02:47:37 5847.57 67.16 -151.58 468.43 96.40 147.71 281.9 Done Example of tddr file read ------------------------ IDL> .COMPILE read_fire_ace_c130_rams.pro % Compiled module: READ_FIRE_ACE_C130_RAMS. % Compiled module: READ_RAMS_BBR. % Compiled module: READ_RAMS_TDDR. IDL> read_fire_ace_c130_rams Enter "1" to read broadband data (bbr), or "2" for multi-channel narrowband radiometers (tddr) 2 fire_ace_rams_tddr_19980524.cdf START DATE: 24 May 1998 fire_ace_c130_nav_19980524.cdf Date Time Alt Lat Lon ----------------------------------------------- 24 May 1998 18:31:21 6210.67 65.97 -149.85 Zenflux = 5.90 25.24 32.49 31.30 27.93 22.87 20.71 Nadflux = 1.43 7.25 7.56 6.60 6.10 5.69 5.51 Date Time Alt Lat Lon ----------------------------------------------- 24 May 1998 21:18: 1 4001.38 76.50 -167.54 Zenflux = 9.80 44.14 53.49 49.06 44.71 40.50 37.16 Nadflux = 7.69 33.13 39.43 36.74 34.13 31.63 29.78 Date Time Alt Lat Lon ----------------------------------------------- 25 May 1998 0: 4:41 6008.78 75.29 -163.67 Zenflux = 9.64 43.25 52.43 48.09 43.56 39.27 36.25 Nadflux = 8.57 37.23 43.76 40.52 37.06 34.37 31.64 Date Time Alt Lat Lon ----------------------------------------------- 25 May 1998 2:51:20 7685.98 67.03 -149.88 Zenflux = 8.99 39.28 48.40 44.99 40.09 36.66 34.13 Nadflux = 8.60 36.83 43.61 40.52 37.28 34.63 32.91 Done 8.0 References Valero et al., 1997, Atmospheric Radiation Measurements Enhanced Shortwave Experiment (ARESE): Experimental and data details, Journal of Geophysical Research 102, No. D25, pp. 29,929-29,937. Valero and Pilewskie, 1992, Latitudinal Survey of Spectral Optical Depths of the Pinatubo Volcanic Cloud, Geophysical Research Letters 19, p. 163. Valero, et al., 1982, Radiative Flux Measurements in the Troposphere, Applied Optics 21, p. 831. Last Updated: September 24, 1999