Daily Summary for 6 December 2006

The third in a series of small systems passed over Southern Ontario. Like the one before, it provided a lot of mid-level moisture and cloud cover, making it the first good opportunity for a solo CLEX flight.

Today was the first solo CLEX flight during the experiment. Numerical cloud models had a good handle on upper level cloud coverage and timing, allowing us to focus our attention on the instrumented ground site, CARE, toward the west today. Coordinated measurements with the CARE ground site were conducted. Air-to-ground communications were good.

While above all clouds enroute to CARE, downward lidar was turned on and revealed cloud structure below with promising supercooled layers. At CARE, mixed phase and supercooled water clouds were present at low levels over the site. SW to NE transits directly over CARE were implemented.

The clouds were first sampled with a level transit from above using lidar. We descended on straight track to minimum altitude to profile clouds quickly. Mixed phase layer was present above water cloud. We could not get to base of water cloud due to altitude restrictions. Decision was made to focus our attention on mixed phase cloud above.

We got block from 6-9 kft. We porpoised through the mixed phase cloud for multiple passes along the SW to NE transit above CARE. Cloud top temperatures were about -10°C. Liquid water present at and near cloud top (up to 0.2-0.3 g/m3 peak near top). Mixed phase conditions were present with low concentrations of ice particles (stellars, dendrites, and irregulars) in and below the water. Ice thickness varied from few hundred meters to almost 1 km deep. Deeper ice present on eastern extent of transit.

We then descended to the lower deck with cloud tops at -5°C that was mostly water, profiling the mixed phase cloud above with Ka-band radar from minimum altitude. Water cloud had measurable signal with Ka-band dBZ. Probes suggested larger droplet sizes there. Generating cells and virga ice from mixed phase cloud above was still present on Ka-band.

CLEX requested a balloon launch immediately after the Convair left CARE air space. We were over CARE for just over 90 minutes. Enroute back to Ottawa we then porpoised through a mixed phase cloud with tops at -12°C with high liquid water content at cloud top (up to 0.3-0.4 g/m3).

Conditions were mixed phase (stellar, dendrites). From probes and radar, ice was detected below cloud in low concentrations until we hit another cloud layer with mostly water at the bottom of the porpoise layer. In ice virga there was a visual gap between clouds in places (between fall streaks?). We continued porpoising mixed phase cloud for about 30 minutes.

Convair instrument issues:

Ka-band downward pointing radar was not usable, likely due to water in the waveguide attenuating signal severely.

2D-C was noisy at times.

All in all, it was a very good CLEX case. Total flight time about 3.75 hours. Thanks to all!