Flight # 16

April 21, 2004.

Flight Scientist: V. Ramanathan

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Flight #23: Take off about 8:13 am. Landed at about 11:30 am

Flight #24: Take off about 1 pm; Lasted about 3 hours

Objectives: A Major pollution event from East Asia , as per Carmichael 's model, had approached the California coast with maximum concentrations around the CIFEX experiment area. In addition, the front of 18 th was followed by anticyclonic circulation over the east pacific bringing ideal stratus and strato cumulus clouds, that were generally non-precipitating. All in all an ideal situation for CIFEX objectives.

Flight 23: Flew from Arcata in southwest direction to about 150 miles west of San Francisco (to about 36.5 N and 127 East) and then landed in Santa Rosa (about 50 miles east of San Francisco ).

Report: Took off at 8.13 am landed at Santa Rosa at about 11.30 AM . Sampled broken strato cumulus and stratus through the flight. Both CN and CCN were generally on the moderate pollution levels at about 500 to 1000 for CN and about 100 to 200 for CCN. Cloud base was typically at about 2000 to 2500 ft and tops varied from 3000 to 3800 ft. Cloud thickness varied from about 1500 to 2500 ft. Took several samples of cloud base data. In addition took vertical cross sectional data from base to top. Around 9.50 am encountered homogeneous deck of stratus clouds and did profiling around 9.56 am . Aerosols were generally in the nucleation mode(large size) . Saw again some precipitating clouds. Around 10.40 am , decided to climb to 10000 ft and sample the brownish aerosol layer. However saw plenty of nucleation mode aerosols and not much ultra fine particles. The sky appeared very dusty. Almost all the particles were nucleation mode particles with PCASP and CN both registering about 700 per cc.

Flight 24: Took off from Santa Rosa at about 1 pm . In stead of retracing the morning flight path, headed in the north westerly direction (flying north of Sam Francisco). Sampled few stratus over the mountains between Santa Rosa and the coast. The clouds seem to be thinning out compared with morning flight. Both CCN and PCASP were low. Cloud base was at about 3000ft and tops at about 4300 ft. At the turn around point, we were circling the same clouds between 21.17 and 21.30 taking both cloud base, in-cloud and cloud top data. Cloud top CN was as high as 2000 per cc. Both PCASP and CCN were low suggesting most of the CN were new particles. At about 21.45 GMT, since clouds were thinning out, started vertical sampling from 21.45 to 21.56 GMT. Peak CN values were seen at about 4500 ft (3000 per cc with practically no particles larger than 30 nm!). At about 21.58 GMT, did a level flight at 11000 ft to collect albedo data. Descended to cloud level to sample clouds as we approached Arcata.