title: MODIS comparisons with northeastern Pacific in situ stratocumulus microphysics.
abstract: Vertical sounding measurements within stratocumuli during two aircraft field campaigns, Marine Stratus/stratocumulus Experiment (MASE) and Physics of Stratocumulus Top (POST), are used to validate Moderate Resolution Imaging Spectroradiometer (MODIS) cloud optical thickness (COT), cloud liquid water path (LWP), and cloud effective radius (re). In situ COT, LWP, andrewere calculated using 5 m vertically averaged droplet probe measurements of complete vertical cloud penetrations. MODIS COT, LWP, andre1 km pixels were averaged along these penetrations. COT comparisons in POST showed strong correlations and a near 1:1 relationship. In MASE, comparisons showed strong correlations; however, MODIS COT exceeded in situ COT, likely due to larger temporal differences between MODIS and in situ measurements. LWP comparisons between two cloud probes show good agreement for POST but not MASE, giving confidence to POST data. Both projects provided strong LWP correlations but MODIS exceeded in situ by 14-36%. MODIS in siturecorrelations were strong, but MODIS 2.1 µmreexceeded in siture, which contributed to LWP bias; in POST, MODISrewas 20-30% greater than in siture. Maximum in siturenear cloud top showed comparisons nearer 1:1. Other MODISrebands (3.7 µm and 1.6 µm) showed similar comparisons. Temporal differences between MODIS and in situ measurements, airplane speed differences, and cloud probe artifacts were likely causes of weaker MASE correlations. POST COT comparison was best for temporal differences under 20 min. POST data validate MODIS COT but it also implies a positive MODISrebias that propagates to LWP while still capturing variability.
authors.affiliation: Desert Research Institute Nevada System of Higher Education Reno Nevada USA.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Noble
authors.affiliation: Desert Research Institute Nevada System of Higher Education Reno Nevada USA.
authors.forename: James G
authors.initials: JG
authors.lastname: Hudson
keywords: cloud liquid water path; cloud microphysics; northeastern Pacific stratocumulus; remote sensing validation; stratocumulus effective radius; stratocumulus optical depth