TITLE: Surface Kosan Radiation Radiometers (Valero)

AUTHOR(S): PI: Francisco P.J. Valero
               University of California, San Diego
               Scripps Institution of Oceanography
               9500 Gilman Drive, Dept 0242
               La Jolla, CA 92092-0242
               Phone: 858-534-2701
                 FAX: 858-822-0517
               email: fvalero@ucsd.edu

           Co-PI: Brett C. Bush
               (Same address as above)
               Phone: 858-822-0514
               email: bcbush@ucsd.edu

           Co-PI: Shelly K. Pope
               (Same address as above)
               Phone: 858-534-9619
               email: spope@ucsd.edu

1.0 DATA SET OVERVIEW: 
       This data set contains radiation measurements made during ACE-ASIA at
       the surface site on Kosan, Cheju Island, Republic of Korea. Archived
       data consists of three broadband radiometers and one spectral narrowband
       radiometer. Two of the broadbands (TSBR or Total Solar Broadband
       Radiometer) measured the "total" solar bandpass (roughly 0.3 to 3.8
       microns) and the third (FSBR or Fractional Solar Broadband Radiometer)
       measured the "fractional" solar bandpass (about 0.68 to 3.3 microns).
       One TSBR and the FSBR had hemispherical fields-of-view (Global) and
       the remaining TSBR was mounted on a solar tracker and measured the
       direct solar flux with a field-of-view of roughly 5.7 degree full
       angle (Direct). The narrowband spectral instrument (TDDR or Total-
       Direct-Diffuse Radiometer) also had a hemispherical field-of-view,
       and a scanning shadowband was used to regularly block the sun thus
       allowing determination of the total, direct, and diffuse components
       of the radiation field. The TDDR consisted of seven unique channels
       measuring the following spectral regions: 495-505 nm, 400-450 nm,
       450-500 nm, 500-550 nm, 550-600 nm, 600-650 nm, and 650-700 nm.

       RAMS measurements at the Kosan site were made on the following days
       during the intensive field phase of ACE-ASIA in 2001:
        March 26, 27, and 30
        April 1, 2, 4, 6, 8, 10-27, and 30
        May 1-4

       All of the radiometers were mounted on the southeast corner of the roof
       of the METRI #1 trailer. The location of the site is as follows:
               Kosan Latitude: 33.29244 North
               Kosan Longitude: 126.16181 East
               Kosan Elevation: approximately 100 meters

2.0 INSTRUMENT DESCRIPTION: 

       The accuracy of the global broadband broadband measurements is
       typically 1-2% whereas that of the direct broadband instruments
       is roughly 0.5 to 1%. The accuracy of the TDDR measurements is
       about 3%.  All radiometric measurements are acquired at approximately
       5Hz. The broadband measurements are averaged into 5 second intervals
       where the time stamp indicates the END of the averaging period. The
       TDDR data is archived at the full time resolution so as to permit
       proper analysis of the shadowband effects.

3.0 DATA COLLECTION AND PROCESSING: 

       All radiometric measurements are acquired using the RAdiation
       Measurement System (RAMS). The raw measurements are converted to
       downwelling fluxes using the following steps, briefly summarized
       below:
        1) Subtract "dark" signal
        2) Apply calibration constant
        3) Correct for slight deviations of the angular response from
           an ideal cosine using estimates of the direct:total ratio.

       Data quality control consists of eliminating periods of data deemed
       unsuitable for flux measurements (i.e. warm up periods, instrument
       maintenance, obstructions within the field-of-view, etc.)

       Although not released in the accompanying data files, aerosol optical
       depths are calculated from the TDDR measurements (on clear days) using
       a shadowband analysis developed at the Atmospheric Research Laboratory,
       Scripps Institution of Oceanography, University of California, San
       Diego. Anyone interested in obtaining these calculations should contact
       the PI or either one of the Co-PIs listed above. 

4.0 DATA FORMAT: 

       All data is archived in NetCDF format. A list of the variables is
       summarized below:
        base_time - "seconds since 00:00:00 1 Jan 1970 GMT" ;
        time_offset_bb - "seconds since base time (for BB1, BB2, and BB4)" ;
        time_offset_tddr - "seconds since base time (for TDDR)" ;
        BB1 - "Direct Total Solar Broadband (W/m2)"
        BB2 - "Global Total Solar Broadband (W/m2)"
        BB4 - "Global Fractional Solar Broadband (W/m2)"
        wavelength - "Nominal Central Wavelength of Spectral Channel (nm)"
        bandwidth - "Nominal Bandwidth of Spectral Channel (nm)"
        TDDR - "ARL-Scripps Total-Direct-Diffuse Radiometer (W/m2/nm)"
        TDDR_ring - "TDDR Shadow Ring Operation"

       The "base_time" variable is always defined to be an integral number
       of whole days so that all time offsets ("time_offset_bb" and
       "time_offset_tddr" are also offsets from 00:00:00 GMT on the given
       measurement day.

       Bad broadband fluxes are flagged with a value of "-999.99" and bad
       TDDR fluxes are flagged with a value of "-99.999".

5.0 DATA REMARKS: 

       Any questions or comments regarding this data set should be addressed
       to the the PI or Co-PIs listed at the top of this README file.

6.0 REFERENCES:

       Broadband Reference:
         Valero et al. 1982, Radiative Flux Measurements in the Troposphere,
         Applied Optics 21, p. 831

       TDDR Reference:
        Valero and Pilewskie, 1992, Latitudinal Survey of Spectral Optical
        Depths of the Pinatubo Volcanic Cloud,
        Geophysical Research Letters 19,p. 163