README file for albedo data measured at Table Mountain SURFRAD site Updated 2012.01.30 Instruments: MFRSR: Multi-Filter Rotating Shadowband Radiometer (also called MFR7) Manufactured by Yankee Environmental Systems, Inc. UVB1: Ultraviolet B Manufactured by Yankee Environmental Systems, Inc. LI-190SA: LI-190SA Manufactured by Li-Cor Broadband: Eppley PSP - Measuring reflected shortwave Eppley NIP - Measuring direct shortwave Eppley 8-48 - Measuring diffuse shortwave Total = Diffuse + (Direct * Cos_Solar_Zenith_Angle) Spectral albedo is obtained with a MFRSR operating in standard fashion, and a MFRSR head mounted on a tower at ~9 m above the surface. The tower instrument is ~100' north of the MFRSR. The same tower hosts the down-pointing UVB and PAR instruments. The up-pointing instruments are adjacent to the MFRSR, so also ~100' apart. The down-pointing broadband instruments are located about 300' to the northwest from the up-pointing instruments. Because of the distance between the up-pointing and down-pointing instruments, and the fact we are using instantaneous samples (generally), the data can be particularly noisy on partly cloudy days. Note that albedo values greater than 2 were set to the missing value (-9.999). Some photos of the tower instruments are available at: ftp://aftp.cmdl.noaa.gov/user/hodges/Pictures/TBL_Albedo_TWR/ The center wavelengths for each instrument are: Nominal: 415: 413.5 415.5 500: 497.4 496.5 615: 615.0 613.6 673: 672.7 671.5 870: 869.8 866.7 940: 939.4 938.5 Calibrations: MFRSR: Calibrated with a Li-Cor standard lamp Tower: Calibrated with a Li-Cor standard lamp UVB (both): Side-by-side calibrations against a reference triad PAR (both): Calibrated with a Li-Cor standard lamp Broadband instruments have calibrations traceable to the WRR Nighttime Offset for the MFRSRs: At least two years of nighttime (zenith > 108 deg) data were analyzed. Correction equations (linear or polynomial) based on head temperature were determined. Analysis of UVB and PAR nighttime data did not indicate a need for correction. Cosine Corrections: The MFRSR data are cosine corrected using the manufacturer's cosine data. Measurement Frequency Prior to 2009.01.01 data were sampled as follows: MFRSR: One-minute instantaneous samples. Tower MFRSR: One-minute instantaneous samples. Tower UVB: One-minute instantaneous samples. Tower PAR: One-minute instantaneous samples. Total UVB: Three-minute average of one-second samples Total PAR: Three-minute average of one-second samples Prior to 2010.01.01 data were sampled as follows: MFRSR: One-minute instantaneous samples. Tower MFRSR: One-minute instantaneous samples. Tower UVB: One-minute instantaneous samples. Tower PAR: One-minute instantaneous samples. Total UVB: One-minute average of one-second samples Total PAR: One-minute average of one-second samples From 2010.01.01 to current: MFRSR: 20s instantaneous samples. Tower MFRSR: 20s instantaneous samples. Tower UVB: One-minute average of 20s samples. Tower PAR: One-minute average of 20s samples. Total UVB: One-minute average of one-second samples Total PAR: One-minute average of one-second samples Data time-stamp is the end of the averaging period. For example: (00:20s + 00:40s + 01:00s) / 3 = 01:00 value The final seven fields are QC, or QC-like, values. Fields 36 and 38 indicate the number of samples making up the UVB and PAR minute averages. Prior to 2010.01.01 when samples were taken once a minute, these fields will be either 0 or 1. From 2010.01.01 forward these fields will be 0 to 3. A value of 2 means for that minute, either the 20, 40, or 00 second sample was missing. A description for the other QC values will be added later. In general though, zero indicates a good measurement. 00 - YYYYMMDDHHMNSS 01 - MFRSR time. Fractional days since 1900.01.01 02 - Decimal YYYYMMDD 03 - Decimal Day-of-Year 04 - Decimal Year - 05 - Air Mass 06 - Solar Azimuth Angle 07 - Solar Zenith Angle 08 - Cosine Solar Zenith Angle - 09 - Albedo: 415nm 10 - Albedo: 500nm 11 - Albedo: 615nm 12 - Albedo: 673nm 13 - Albedo: 870nm 14 - Albedo: 940nm 15 - Albedo: UVB 16 - Albedo: PAR 17 - Albedo: Broadband - 18 - Reflected Irradiance: 415nm 19 - Reflected Irradiance: 500nm 20 - Reflected Irradiance: 615nm 21 - Reflected Irradiance: 673nm 22 - Reflected Irradiance: 870nm 23 - Reflected Irradiance: 940nm - 24 - Total (aka Global) Irradiance: 415nm 25 - Total (aka Global) Irradiance: 500nm 26 - Total (aka Global) Irradiance: 615nm 27 - Total (aka Global) Irradiance: 673nm 28 - Total (aka Global) Irradiance: 870nm 29 - Total (aka Global) Irradiance: 940nm - 30 - Diffuse Irradiance: 415nm 31 - Diffuse Irradiance: 500nm 32 - Diffuse Irradiance: 615nm 33 - Diffuse Irradiance: 673nm 34 - Diffuse Irradiance: 870nm 35 - Diffuse Irradiance: 940nm - 36 - Direct Irradiance: 415nm 37 - Direct Irradiance: 500nm 38 - Direct Irradiance: 615nm 39 - Direct Irradiance: 673nm 40 - Direct Irradiance: 870nm 41 - Direct Irradiance: 940nm - 42 - Reflected Broadband Shortwave 43 - Total (aka Global) Broadband Shortwave 44 - Diffuse Broadband Shortwave 45 - Direct Broadband Shortwave - 46 - Reflected UVB 47 - Total (aka Global) UVB 48 - Reflected PAR 49 - Total (aka Global) PAR - 50 - Number of measurements for Reflected UVB average [0 to 3] 51 - QC Value for Total UVB [x to y] 52 - Number of measurements for Reflected PAR average [0 to 3] 53 - QC Value for Total PAR [x to y] 54 - QC Value for Reflected Broadband Shortwave [x to y] 55 - QC Value for Direct Shortwave (Used for Total Irradiance) [x to y] 56 - QC Value for Diffuse Shortwave (Used for Total Irradiance) [x to y]