CIFEX Experiment # 9

April 12, 2004.

Flight Scientist: Eric Wilcox

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Flight# 13 : Take off around 9 a.m.. Landed at 12:45 p.m.

Objectives: Sample stratocumulus clouds and aerosols below cloud.

Weak stratocumulus clouds were arranged in bands offshore; the first extending from approx. 150 n. miles to 165 n. miles from Arcata, and the second from 200 n. miles to beyond our endpoint 250 n. miles from Arcata. Additionally, a deck of coastal stratus extended from inland to approx. 60 n. miles offshore. On outbound leg the coastal deck extended from 1400ft to 5800ft with average drop diameters 20-25um and occasional large drops in the 1D probe from 40-45um. Skies were clear above the coastal stratus. Along outbound leg at 1000ft all the way out to 150 n. miles revealed clean boundary layer conditions with CN concentrations 250-350/cc and PCASP concentrations 120/cc. Thin stratus clouds were sampled 150 n. miles from Arcata at 4850ft with drop concentrations 40-50/cc and diameters 15-20um. 200 n. miles offshore at 5150ft; again high concentrations of small drops 70-120/cc at 10-15um. CN concentrations were 250/cc below these clouds. The small drops were likely due in part to weak dynamics. By the end of the flight, the coastal stratus had become thicker. This deck was sampled in several short east-west transects of 10 miles, indicating low concentrations (4-14/cc) of large drops (30um). A pass below this cloud deck revealed CN concentrations of 250/cc.