资源环境科技发展态势分析平台

Ship measurements collected over the northeast Pacific along transects between the port of Los Angeles (33.7 degrees N, 118.2 degrees W) and Honolulu (21.3 degrees N, 157.8 degrees W) during May to August 2013 were utilized to investigate the covariability between marine low cloud microphysical and aerosol properties. Ship-based retrievals of cloud optical depth (tau) from a Sun photometer and liquid water path (LWP) from a microwave radiometer were combined to derive cloud droplet number concentration N-d and compute a cloud-aerosol interaction (ACI) metric defined as ACI(CCN) = partial derivative ln(N-d)/partial derivative ln(CCN), with CCN denoting the cloud condensation nuclei concentration measured at 0.4% (CCN0.4) and 0.3% (CCN0.3) supersaturation. Analysis of CCN0.4, accumulation mode aerosol concentration (N-a), and extinction coefficient (sigma(ext)) indicates that N-a and sigma(ext) can be used as CCN0.4 proxies for estimating ACI. ACI(CCN) derived from 10 min averaged N-d and CCN0.4 and CCN0.3, and CCN0.4 regressions using N-a and sigma(ext), produce high ACI(CCN): near 1.0, that is, a fractional change in aerosols is associated with an equivalent fractional change in N-d. ACI(CCN) computed in deep boundary layers was small (ACI(CCN) = 0.60), indicating that surface aerosol measurements inadequately represent the aerosol variability below clouds. Satellite cloud retrievals from MODerate-resolution Imaging Spectroradiometer and GOES-15 data were compared against ship-based retrievals and further analyzed to compute a satellite-based ACI(CCN). Satellite data correlated well with their ship-based counterparts with linear correlation coefficients equal to or greater than 0.78. Combined satellite N-d and ship-based CCN0.4 and N-a yielded a maximum ACI(CCN) = 0.88-0.92, a value slightly less than the ship-based ACI(CCN), but still consistent with aircraft-based studies in the eastern Pacific.