On the Solar Radiation Budget and the Cloud Absorption Anomaly Debate

Abstract

This paper reviews the current state of knowledge, advances and challenges in short-wave earth radiation budget (ERB) studies and the cloud absorption anomaly (CAA) debate. The ERB issues deal exclusively with the solar energy disposition between the atmosphere, clouds and the surface. The ERB and its disposition have been derived from surface observations, satellite remote sensing and general circulation modeling. Major sources of uncertainties and discrepancies between observations and modeling are highlighted. Reported discrepancies between the ERB data sets obtained by various means are discussed, especially within the context of the recent debate concerning the CAA. This debate is documented thoroughly and critically in four stages: before and after the mid-1990s, and following two dedicated field experiments: the Atmospheric Radiation Measurement Enhanced Shortwave Experiment (ARESE I and II). An attempt is made to shed light on the causes of some controversial findings. It is now clear that the CAA is largely an artifact which does not emerge from a carefully designed closure test using the state-of-the-art radiative transfer models.

Atmospheric Radiation Measurement Program Science Plan. Current Status and Future Directions of the ARM Science Program

“…Several sets of spectral and broadband radiometers were deployed and intercompared, and all generally agreed to within 10 Wm -2 . For the four observed extensive cloud cases, independent investigations (Li et al 2004; did not find a cloud absorption anomaly close to those found previously, although there remains a small instantaneous discrepancy on the order of 20 Wm -2 . While one cannot negate an absorption anomaly of much smaller magnitude, if it exists, it should be viewed within the framework of the various uncertainties in the measurements (~10 W m -2 ), the mismatch between ground and aircraft observations (<20 W m -2 ), model calculations (<20 W m -2 ), and errors in input data, particularly the variation of the underlying surface albedo.…”

Solar absorption over Europe from collocated surface and satellite observations

“…Still, the GCM‐simulated atmospheres appear too transparent with respect to solar irradiance [ Wild et al , , , ]. The highly debated effect of anomalous cloud absorption [e.g., Stephens and Tsay , ; Cess et al , ; Li et al , ; Li , , and references therein] and its possible underestimation in GCMs constitutes yet another source of uncertainty.…”