Comparison of column ozone retrievals obtained by UV multifilter rotating shadowband radiometer with those from Brewer and Dobson spectrophotometers

Abstract

A limited evaluation of Ultraviolet Multifilter Rotating Shadowband Radiometer (UVMFRSR) based monitoring was conducted for instruments operated at the Mauna Loa Observatory, Hawaii 2/1/04 - 5/31/04. Two UV radiometers were installed, an UVMFRSR (shadowband) and a tracker mounted UVMFR (no shadowband). Measurements from the two UVMFR's, collocated Brewer and Dobson UV spectrophotometers, and the TOMS satellite, allowed a number of intercomparisons. The Langley-Forgan calibration technique proved more effective than lamp or Langley-SLR (simple linear regression) techniques when applied to an UVMFR that exhibited substantial change in response. Direct irradiance from an UVMFRSR compared very well with direct irradiance measured by a tracker mounted UVMFR for full-sun days (r²'s = 1). Mean ratios of the UV-MFRSR column ozone retrievals to the collocated Dobson and Brewer were 1.015 and 1.011 respectively. The mean ratio of UVMFRSR ozone to TOMS satellite ozone was 0.907. The UVMFRSR advantages of relatively low cost, unattended operation, automated calibration stability checks using Langley plots, and minimal maintenance make it a unique instrument for column ozone measurement.