CIFEX Experiment # 12

April 15, 2004.

Flight Scientist: Greg Roberts

Flight #17

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Objective:  Sample stratus clouds and profile developed cumulus cell

Times are local time (GMT = Local Time + 7)

Take-off:  12:01

Land: 15:33

Multiple layers observed at take-off and climbed to 15000ft to look for

cloud systems.  Encountered cumulus cloud with top near 15000ft and a

stratus deck below attached to the developed cell and stretched

northwards.

12:30 - passed through aerosol layer en route to cumulus cell

12:38 - 12:50:  made several passes through cell while descending to lower

stratus layer.  Ice crystals and precipitation observed on 2DC and radar.

12:54 - begin track north in cloud deck.  Clouds were ca. 200m thick and

base rose during the leg.  Conducted two passes in/below clouds before

finding new cloud system.

o CN - < 500

o PCASP - 25

o CCN - 50

13:37 - Changed course towards developed cumulus band

13:42 - Samples below cloud base.  Heavy precipitation observed.  In

non-precipitating regions aerosol concentrations were relatively low.

o CN - 400

o PCASP - 26

o CCN - 50

13:46 to 14:35 - cloud passes at 3500, 6500 and 12000ft.  Heavy rains

observed on aircraft radar and skirted the cores to avoid potentially

dangerous downdrafts.  Ice melting layer at 3600 ft.

o FSSP: ca. 88 /cc

o 1DC: 400 /L

o CN: 200 /cc near cloud tops

14:37 - Begin vertical profile down through cloud at 500 ft/min.

14:46 - 11500 ft observed supercooled. Water

15:04 - melting layer at 3500ft

15:06 - through cloud base at 1200ft

Below cloud aerosol concentrations were high at

o CN - 1500 - 2000

o PCASP - 61

15:28 - CCN not working during return

15:30 - Trinidad Head fly-over

o CN - 2000