Lack of closure between dry and wet aerosol measurements: Results from ACE-2

Using data from the ACE-2 field experiment we examine observed and predicted particle size spectra at relative humidities that are representative of the region immediately below the base of marine stratocumulus clouds. The comparison consists of airborne particle size distribution measurements made with an FSSP-300, at ambient relative humidities and north of Tenerife, Spain, and inferred wet aerosol spectra derived using Kohler theory. The theory was initialized with both aerosol size distribution (measured at RH=20%) and aerosol composition measurements made at the Punto del Hidalgo (PDH) site, located on the north coast of Tenerife. The comparison shows that the FSSP-300 reported substantially lower concentrations in the tail of the wet size distribution (wet diameter greater than 0.38 μm) compared to that inferred using the PDH data and Kohler theory.