Fig. 1: Liquid water path (LWP) vs cloud droplet number concentration (CDNC) relationships obtained from satellite data over decreasing spatiotemporal scales.
Similar increasing and then decreasing paired LWP vs CDNC relationships are observed in all cases indicating that processes occurring at small spatiotemporal scales are causing the relationships. Panel a shows a 2D histogram of LWP and CDNC 1 × 1° daily datapoints taken over 1825 days for the whole of the Pacific North region (20–35° N, 110–150° W; ocean only) with colors showing the number of datapoints and the circles/bars showing the mean LWP ± the standard deviation for specific CDNC bins. Panel b shows LWP binned by CDNC for the same area and period, but now using only daily snapshot data for each line in order to limit meteorological variability over time. Additionally, the daily standard deviation of the Aerosol Index is limited to below 0.04 in order to limit the impact of aerosol changes on the observed relationships. N shows the number of days in the plot and only those days are shown for which the number of datapoints Nday exceeds 150. Only those points are shown for which the number of datapoints per CDNC bin exceeds 4. Lines are colored by the area mean AI. Panel c shows the same as for b except that a much smaller region (5 × 5°) is used in order to limit meteorological variability, and thresholds Nday > 100 and NB > 3 are used. MODIS data aggregated to 0.25 × 0.25° scale was used in c to increase the number of datapoints.
