WISG

We propose that the ASR developed by Philipona be brought back to full operation for a four-week experiment conducted at the SGP where the IRIS, ACP, and ASR, will make coincident and simultaneous measurements. Late October through mid November is ideal for such a comparison based on climatological conditions at the SGP site at this time of the year. Often the sky is clear and the water vapor column is both below and above the 1 cm level that is crucial for ferreting out the water vapor dependence noted in Gröbner et al. (JGR, 119, 7083, 2014).

The goal, of course, is to determine whether the next improvement in infrared radiometry uncertainty can be made with confidence based on comparisons of three independently developed absolute instruments, a long-term goal of the Baseline Surface Radiation Network (BSRN) and ARM.