Figure 8. CCN spectrum taken march 25 in "dirty" Northern Hemisphere air. The measured CCN are dramatically different from the CCN spectrum calculated from the aerosol number disribution, assuming a composition of ammonium sulfate. The dotted line is the CCN spectrum calculated from the aerosol distribution, assuming a soluble fraction of only 0.05. The measured and calculated CCN concentrations have increased by an order of magnituded over the "pristine" case.