An Automated Method of MFRSR Calibration for Aerosol Optical Depth Analysis with Application to an Asian Dust Outbreak Over the United States
Modern robotic spectral solar instruments designed for retrievals of aerosol optical depth (AOD), such as the Multi-Filter Rotating Shadowband Radiometer (MFRSR ) (Harrison et al. 1994), usually operate in an unattended mode. Thus their raw data sets sample a wide range of atmospheric conditions, most of which are undesirable for aerosol optical depth analysis. In addition, these instruments are often not calibrated for absolute irradiance, and must be calibrated for AOD analysis from their own operational data. For AOD retrievals, this involves extrapolation to the value that the instrument would measure before the sun's beam enters the earth's atmosphere, i.e., the extraterrestrial, or zero air mass signal (I 0). This value is inferred via the Langley method (Shaw 1983). Recently, a method that utilizes component solar measurements (direct and diffuse) to identify totally clear-sky and non-hazy periods (Long and Ackerman 2000) has been used successfully to screen MFRSR data for spectral solar measurements suitable for calibration Langley plots. This method was tested in a proof-of-concept mode on a two-month period during the Spring of 2001 with data from the Table Mountain SURF RAD station near Boulder, Colo. The resultant calibration is subsequently applied to an Asian dust event that occurred within that period, and verified with independent aerosol optical depth measurements from a nearby MFRSR and an automated sun photometer.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 15010096
- Report Number(s):
- PNNL-SA-37800; KP1201030
- Journal Information:
- Journal of Applied Meteorology, 42(2):266-278, Journal Name: Journal of Applied Meteorology, 42(2):266-278
- Country of Publication:
- United States
- Language:
- English
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