CONCERNING THE INTERPRETATION OF ENHANCED CLOUD SHORTWAVE ABSORPTION USING MONTHLY-MEAN EARTH RADIATION BUDGET EXPERIMENT GLOBAL ENERGY-BALANCE ARCHIVE MEASUREMENTS/

To study the signature of enhanced shortwave absorption in clouds, sev eral recent studies have used monthly-mean shortwave radiation measure ments from the Earth Radiation Budget Experiment (ERBE) together with monthly-mean surface insolation as obtained from the Global Energy Bal ance Archive (GEBA). In this paper we discuss probable causes of incon sistent results, among themselves, from these studies and with other s tudies that have reported enhanced shortwave cloud absorption relative to theoretical model calculations. Two factors are identified as pote ntial contributing sources of inconsistencies. One is the inseparabili ty of the seasonal variations of water vapor and clouds in the contine ntal area of the northern hemisphere when using collocated monthly ERB E/GEBA data. The second is the impact of data collocation errors on th e signature of cloud absorption. Both factors are quantitatively exami ned using observational data and radiative transfer models.