HALO-20240912a

HALO-20240912a#

Crew#

Georgios Dekoutsidis, Sabrina Zehlau, Janina Bömeke, Jakob Deutloff, Michael Schäfer, Anja Stallmach, Felix Ament, Manfred Wendisch

Track#

track

Conditions#

The ITCZ was forecast to be very broad, with not well-defined edges for the circles to be placed as usual. This prompted us to take a step back and look into other potentially interesting parameters and phenomena to be probed. A wide area of low surface-windspeeds (doldrums) appeared to be one of the more interesting features. And it was decided to place circles inside and around this area in order to measure the doldrums, the trade winds south and north of it and potentially some increased moisture in the outflow of a convective system in the Northwest.

On the day of the flight the forecast was confirmed with only slight changes. The broad ITCZ became evident from the very beginning as high values of IWV were measured close to its southern edge, along with a great variety of convective and stratiform clouds at low, mid and high levels. Cloud-free areas with very well-defined edges identified as cold pools were frequently seen. The conditions at the second circle were slightly different as we entered the doldrums. Cloudiness consisted mostly of high cirrus at and around flight Level, with virtually no convection even at lower levels. Clear indications of doldrums from dropsonde measurements. The third circle had some convection to the North with more clear indications of doldrums in the southern part, such as mirroring of clouds on the sea surface. On the EarthCARE underpass we exited the doldrum region and had stratiform mid-level cloud patches with the picture getting more convective to the south and the last circle, where we met again the southern trade winds. Well-defined cloud-free cold pools were frequently observed. Situation remained similar on the way back with deep convection including overshooting tops and anvils around Barbados.

Execution#

Take-off was a few minutes early as everything worked out well on the ground with no delays. Soon HALO was centered on track and climbed up to FL410. Just before entering the first circle (SE) all instruments were go, having resolved the trouble with the dropsondes. We entered the SE circle at its northern entry point and flew in a CW direction. After completing the circle, we transited to the second one creating a figure 8 and climbed up to FL430. On the entry to the NE circle the plane briefly adjusted its course until it was established on course. The circle was flown CCW. NE circle was completed with no problems. On the way to the 3rd circle (NW) we climbed to FL450. Due to traffic around us the clearance to drop sondes would be delayed and we were some minutes ahead of plan. To counteract we performed a short waiting circle in CCW direction. We then entered the NW circle, flew in CCW direction and soon after got clearance. In order to then complete the circle, we overshot our exit point by a few nm and then turned sharply onto the EarthCARE track. The EarthCARE underflight worked out well and after reaching the southernmost point of the track we immediately initiated the last circle (SW) in a CW direction. The circle was completed without problems. After completing the last circle, we came back to land.

Impressions#

11:25 Takeoff and heading towards first waypoint
11:35 Flying over a few fair cumuli; some congestus are visible; a few high convective clouds with outflow anvils to the south. No cirrus above us, but some patches of old outflow cirrus around us.
11:43 Approaching high convective clouds with anvil south of HALO
11:47 Turn to get back on planned track
11:50 High IWV of about 60kg/m2
11:51 Cirrus shelf over us. HALO at 11 km
11:54 Great variety of convective clouds – from shallow cumuli, up to some small stratocumulus patches, congestus, and some nimbus clouds reaching almost up to flight height; and anvil cirrus.
11:59 Transition to much less cloudy Region.
12:01 Reached FL410
12:08 Troubleshooting with the dropsondes still ongoing.
12:20 Shallow cumulus all around
12:59 Dropsonde green lights
13:04 Entry southeast circle
13:20 Flying over cold pool. Only few shallow cumuli partly organized in short line
13:32 Two convective cells with anvil to the south
13:40 To the left: almost cloud free; to the right: inside the circle some patches of ice clouds (cirrus at lower levels), some shallow cumulus and a hand off higher reaching congestus
13:49 Back into shallow low-level convective clouds
13:52 Flying over some stratiform cirrus patches a midlevel ~5km height
14:01 Last sonde out. Turn to second circle climb to FL430.
14:13 Into second circle (northeast). Plane adjusted itself briefly. Dropsonde operation start; cloud free within the circle; stratiform remnants of convection (old outflows at all levels) to the right.
14:19 much more stratiform cloud patches
14:25 Sargassum patch in wind direction
14:35 Flying over a congestus system, and dropping a sonde! NE05
14:43 Flying in Cirrus occasionally
14:53 Thin cirrus right below us; huge cirrus decks to the left and right of HALO
14:57 Old cirrus but almost no PBL or midlevel clouds
15:00 Some very light turbulence
15:10 Last sonde out. Leaving circle and flying through
15:12 In cloud free air
15:23 Sea surface very calm. Doldrums.
15:25 Some shallow and congestus convection to the right of HALO. Huge stratiform Cirrus deck to the left.
15:46 Waiting circle due to early Arrival for EC and delayed dropsonde clearance
15:50 Deep convection to the NW
16:02 Entering circle
16:08 Clearance and first sonde
16:12 Crossing boundary into cloud-free air
16:15 Back over a great variety of convective clouds: some shallow cumulus, some decks of altostratus, a few taller congestus system, no cumulus nimbus through the full troposphere
16:19 Patches of midlevel stratiform clouds
16:30 more intense boundary layer convection; deep convection with anvil cirrus to the north
16:34 Getting into a cirrus
16:41 Doldrums. Clouds reflected on sea surface.
16:50 inside circle random shallow trade wind cumuli; a few clusters of more vigorous convection but all limited to lower troposphere
17:03 Last sonde out and leaving circle a bit further west that planned
17:06 Deep convection to the north
17:11 Level wings on EarthCARE track
17:30 boundary layer convection topped by a lot of stratiform outflows at inversion height. Taller system only to the Southwest
17:35 Earth Care Underpass – Halo flying over patch of stratocumulus like outflows of boundary layer convection. Deeper congestus like convection further to the South
17:48 Cold pool
17:53 leaving ec track starting circle; West of transect: infinite Zoo of trade wind shallow cumuli; east of transect: slightly more organized shallow convection with some cloud wholes.
17:56 Shallow convection not topped by any outflows, rarely organized into clusters or line
18:25 top of convection is much more stratiform- inversion capped, larger patches of almost stratiform outflows; less boundary layer convection below.
18:27 Reaching a high cirrus
18:34 Almost cloud free, just a few thin low cirrus
18:45 Directly next to a tall convective tower to our right
18:49 Cloud whole (cold pool generated)
18:55 Last sonde out; heading back
19:02 Nice stratiform clouds to the south
19:11 flying home through again an ocean of scattered shallow trade wind cumuli partly overlayed by thin layers of midlevel cirrus; cloud cover is overall low
19:37 band of deep convection to the south great overshooting tops
19:43 Crossing South-North-Line of deep convection with tall nimbus towers
20:06 Landing

Our crew before the flight

High IWV and a great Variety of convective Clouds on our way to the first circle

Icy Patches inside the first circle with a vast Cloud free area outside

Calm sea-surface and Cloud mirroring on the way to the 3rd circle

Deep convection North of the third circle

Fancy Johny Bravo anvil

Cloud hole with sharp edges under the almost-full moon

Crew in-flight

Another very clear Cloud hole

Happy Clouds on the way back

Instrument status & quicklooks#

Instrument	Operational	Comment
BACARDI	✅	None
BAHAMAS	✅	None
Dropsondes	✅	Trouble detecting RH in HALO and then GPS Signal. Delayed clearance for NW circle.
HAMP	✅	None
PI-Camera	✅	None
Smart	✅	None
SpecMACS	✅	None
VELOX	✅	None
WALES	✅	None