Figure 2. CRE in the FIR and the atmospheric window.

(a) Observations of 3-hour averages of downwelling infrared CRE from Barrow, Alaska; Eureka, Canada and Summit Station, Greenland, plotted as a function of PWV. Only CRE>60 W m⁻² are shown to highlight clouds that are optically thick. (b) Same as a, but plotted as a function of near-surface air temperature. (c,d) are similar to a,b, but are separated into spectral components from the atmospheric window (CRE_AW, red points) and the far-infrared (CRE_FIR, blue points). For reference, the arrows in c are the approximate ranges of PWV for the Arctic, mid-latitudes (M.L.) and Tropics. Curves in c,d are radiative transfer calculations of CRE_FIR (dashed black), CRE_AW (solid black) and their sum CRE=CRE_FIR+CRE_AW (grey).