Ice Nuclei Measurements - May 07 Flight
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(Additional information for Oct 15, 1998 progress report - Significant Highlights - )
Two figures are shown for the May 7 flight from 22:05 to 22:40UTC,
ice nuclei / aerosol measurements and
C-130 aircraft sounding .
22:05 - 22:19 Aircraft descended through the surface inversion, through low level cloud, and to surface of ice pack. The cloud top was -20C, at the base of the inversion. Note pronounced dip in CN concentration at 22:18 while in cloud. Ice crystal concentration ~1-3 per liter.
22:20 - 22:29 Aircraft ascended to an altitude of a few hundred meters and penetrated the lower levels of the cloud. Note highly variable CN.
22:29-22:40 Descended to ~30m low level surface transects near ship. CN concentrations near the surface were generally quite small and steady ~300/cc except for occasional brief spikes of higher concentration when the airplane crossed its own exhaust or perhaps the plume from the ship.
The aircraft sounding shows strong changes of aerosol concentration coincided with thermal stratifications.
22:34 and 22:37 large dips in CN were the result of deliberately filtering the sample as a check for air leaks. Filtered air should have zero CN counts, and it does.
During this time period, ice nuclei were measured at -27C and +3% water supersaturation in the CFD chamber. IN concentrations are shown in panels 2, 3 and 4 from the bottom of the ice nuclei / aerosol plot Panel 2 shows IN counts per second, panel 3 is 10 sec average, and panel 4 is 60 second average. IN concentration was very low (< 1 per liter) during descent 22:05 - 22:19. Then, in the surface layer 22:20 - 22:29 IN were more numerous, ~5-10 per liter. At 22:31 the IN concentration rose very rapidly to ~1000 per liter. When the air sample was briefly filtered, 22:34 and 22:37, both CN and IN fell to near zero.
Particle samples for electron microscope analysis were collected for total aerosol 22:21 - 22:39, and ice nuclei 21:41 - 22:40.
Additional analyses will include the cloud microphysics, aerosol, meteorology, surface conditions. Points of special interest during this time include:
What is the origin of the large IN concentrations?
Are there regions in nearby clouds that show occasionally higher crystal concentrations?
What are the sizes and composition of the IN and total aerosol?
