HALO-20240821a

HALO-20240821a#

Crew#

Cathy Hohenegger, Georgios Dekoutsidis, Tobias Kölling, Helene Glöckner, Kevin Wolf, Zekican Demiralay, Divya Praturi, Julia Windmiller

Track#

track

Conditions#

Very clean air conditions over Sal with island-induced shallow clouds at departure.

The flight was located on the 26.7W longitude. The ITCZ was narrow with a well defined northern band of deep convection and rain at around 9N. The northern edge in terms of deep convective clouds was in ‘c_north’, on its southern half, whereas there was a band of stratocumulus with an edge at its northern boundary. In terms of precipitable water, there was a second edge with a sharp gradient (from 65 to 30 mm) sampled by ‘c_extra’, whereas precipitable water only dropped to 50 mm in ‘c_mid’. Yet there was no deep convective clouds in ‘c_extra’ but clear sky, and few isolated shallow cumuli. There was a secondary NE-SW oriented band of deep convection striking through the northern half of ‘c_south’. Meteor was under this band while HALO sampled this band while flying around ‘c_south’ in its NW quadrant.

On the leg between Sal and 26.7W we crossed regions/patches of clear sky and stratocumuli. Waves patterning on the clouds visible. On the way back, two layers of clouds with altocumulus/cirrus on top and stratocumuli/cumuli at the bottom.

Execution#

The replacement for the emergency light battery did not arrive in time so that the flight was restricted to daylight hours. With a take-off at 12:20 UTC because of runaway restriction, the original flight plan had to be shorten to ensure a landing in daytime hours. The legs to south_tp (including overpass over Meteor) and to Mindelo were abandonned. Also it turned out that choosing 26.7W as longitude for flying was a mistake as it was below the main route of airliners going to south America. We didn’t get clearance to drop sondes on ‘c_mid’. We circled 1 h around it and then got an estimate that it might be possible to drop sondes in 40 min, which we couldn’t wait anymore. We waved to Meteor from ‘c_south’ while Meteor was in the circle. We did CCW circles where possible as this gave better sight for the SpecMacs camera.

Impressions#

Convection was not as deep as on Sunday, probably top around 12 km. While crossing the ITCZ and circling around ‘c_mid2’, we were in a soup of white.

Circles start time (in UTC, first sonde): 14:17 for ‘c_south’ (from N, CW), 15:20 for ‘c_mid’ (from S, CCW), 16:54 for ‘c_north’ (from N) and 17:55 for ‘c_extra’ (from S, CCW)
HAMP measured 100 mm of precipitable water in ‘c_mid’. This seems unrealistically high.

Note

South circle sampled an active convective line, also experienced by Meteor

Crew

Island-induced clouds by take-off (12:26 UTC)

In the ITCZ, entering ‘c_south’ (14:12 UTC)

Hole in the ITCZ (16:44 UTC)

Leaving the ITCZ, southern edge of ‘c_north’ (17:56 UTC)

Stratocumulus edge, southern edge of ‘c_north’ (18:52 UTC)

TOOCAN’s segmented MCSs at 1500 UTC.

Instrument status & quicklooks#

Instrument	Operational	Comment
BACARDI	✅	None
BAHAMAS	✅	None
Dropsondes	✅	Restart needed before first circle. Three no launch detects. No ATC permission to drop sondes on ITCZ center circle
HAMP-Radar	✅	None
HAMP-Radiometer	✅	None
Smart	✅	fully functional
SpecMACS	✅	Some icing on side windows.
VELOX	✅	Some icing on KT-19
WALES	✅	None