The USDA ultraviolet radiation network currently includes four high-resolution spectroradiometers, located at Table Mountain, Colorado (deployed November 1998); the Atmospheric Radiation Measurement Climate Research Facility in Oklahoma (October 1999); Beltsville, Maryland (November 1999); and Fort Collins, Colorado (October 2002). These spectroradiometers contain Jobin Yvon's 1-m Czerny-Turner double additive spectrometers. The instruments measure total horizontal radiation in the 290- to 371-nm range, once every 30 min, with a nominal FWHM of 0.1 nm. We describe data quality control techniques as well as the data processing required to convert the raw data into calibrated irradiances. The radiometric calibration strategies using Central UV Calibration Facility FEL lamps that are directly NIST-traceable, portable field calibrators, and vicarious calibrations using data from UV multifilter rotating shadowband radiometers (MFRSRs) are discussed. Using direct-to-diffuse ratios from UV MFRSRs, we derive direct and diffuse high-resolution horizontal spectra from the collocated UV spectroradiometers of the USDA network. The direct-beam spectra can be used in a Langley regression that leads to spectroradiometric in situ calibration and to ozone column and aerosol optical depth retrievals. The high-resolution direct spectra are used to obtain the ozone column and aerosol optical depth in the 290- to 360-nm range at 0.1-nm resolution. A statistical summary of network performance is presented.
The data from the UV-RSS deployed at Table Mountain, Boulder Colorado since June 2003 are used to retrieve ozone column and aerosol Angstrom coefficients in the 290nm-380nm range. Retrievals are performed from Langley regression and from direct normal instantaneous irradiance.
From direct-to-diffuse ratios from UV Multifilter Rotating Shadowband Radiometers (MFRSR) we derive direct and diffuse high resolution total horizontal spectra from the collocated UV spectroradiometer of the USDA network. The direct beam spectra can be used in Langley regression that leads to spectroradiometric in situ calibration and to ozone column and aerosol optical depth retrievals. The high resolution direct spectra are used to obtain ozone column, and aerosol optical depth in the 290nm-360nm range at 0.1nm resolution.
KEYWORDS: Calibration, Ultraviolet radiation, Lamps, Mercury, Free electron lasers, Data processing, Diffusers, Spectroscopy, Data conversion, Received signal strength
The USDA UV radiation network currently consists of four high resolution spectroradiometers located at Table Mountain, Colorado (deployed 11/1998); the Atmospheric Radiation Measurement testbed site at Southern Great Plains, Oklahoma (deployed 10/1999); Beltsville, Maryland (deployed 11/1999); and Fort Collins, Colorado (deployed 10/2002). These spectroradiometers contain Jobin Yvon’s one meter asymmetric Czerny-Turner double additive spectrometer. The instruments measure total horizontal radiation in the 290nm to 360nm range, once every 30 minutes, with a nominal full-width at half-maximum (FWHM) of 0.1nm. We describe data quality control techniques as well as the data processing required to convert the raw data into calibrated irradiances. The radiometric calibration strategies using NIST FEL lamps, portable field calibrators, and vicarious calibrations using UVMFRSR data are discussed and a statistical summary of network performance is presented. All results are presented in the context of data processing and analysis tools including software and database systems.
At present the United States Department of Agriculture (USDA) Reference Spectroradiometric Network consists of 4 sites: Table Mt. CO, Ft. Collins CO, Lamont OK (The ARM program SGP site), and Beltsville MD. At each site we operate a 1-meter cascaded additive-double Czerny-Turner scanning monochromator with a bi-alkali Photomultiplier and photon-counting detection. Irradiance calibrations are provided for the instrument at Table Mt CO by NOAA's Central Ultraviolet Calibration Facility (CUCF) from NIST-traceable standards. Calibrations are transferred from this instrument to others in the network (and additional stability monitoring of the primary instrument conducted) using shippable transfer calibrators we have designed. Here we describe these transfer calibrators, and our operational experience seen at the Table Mt. Site in 2002 and 2003 to date.
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