NASA06. January 26, 2006. – Flight scientist’s notes
Crew: Tom Drew (pilot), Jeff French (tech seat), Brent Glover (aerosol), Dave Leon (flight scientist)
In the 1-2 hours preceding the scheduled takeoff at 12 noon the clouds developed considerably, with the typical wall of cloud downwind of the Snowy Range and with intermittent high cloud over the Laramie valley.
The King Air took off just after 12 noon and did a spiral climb up to 20kft (?) to obtain a sounding over the Laramie Valley. We then climbed up to ~ 24kft on the E-W leg over GLEES in order to reach (near) the top of the upper cloud layer and to see if there was an obvious reason that the tops of the clouds were so flat. The top of this climb was reached near the GLEES site. At this time there was a slight gap between the upper and lower cloud layers. Brent Glover reported spikes in the CCN Vdet during the ascent – something that was noted intermittently during the rest of the flight.
We then began the descent into the Saratoga valley. Unlike the flight on the 18th there was no well-defined leading edge to the liquid cloud. Instead, broken clouds stretched out over much of the valley. The base of the lower cloud layer sloped steeply downward towards the North. Cloud-base was at 11-12 kft around Medicine Bow peak (only the top of the ridgeline was obscured by the cloud layer) but was at ~9.5 kft upwind of Elk Mtn.
The upwind leg of the H-pattern was flown at an altitude of 9 kft. The aircraft track angle was changed about 1/3 of the way from the Northern end of the leg. The aircraft track angle for the southern end of the leg more closely followed the valley. This deviation allowed us to stay closer to the edge of the cloud layer (to the extent that there was a defined edge). A similar pattern was flown for the Northbound, return leg.
The aircraft then made a short sounding up to about 17kft, during which Jeff F. and I both noted a large # of little plates on the 2D-C including a large # of images with holes. We then flew the along-wind leg over GLEES at 14kft during which the 2D probes showed columsn and some dendrites. The aircraft emerged out of the cloud layer well to the west of GLEES consistent with the WCR cross-sections which showed that the cloud-top sloped dramatically downward from West to East over the Snowy range. Unlike the previous flight (Jan 18th) we encountered relatively little liquid water on this or subsequent passes. Even where liquid water was encountered, it was transient – little wisps rather than extensive layers. Some turbulence was noted downwind of GLEES.
We then descended to 9kft for the downwind leg of the H. Despite comparable winds, this leg was far more turbulent than on the 18th. The upper cloud layer became more broken during this leg, and stack of lenticular clouds that would remain for the rest of the flight became visible over Elk mtn (these may have been present earlier, but obscured by the upper cloud layer).
We then climbed to 17kft for the remaining along-wind legs over the Snowy range (the 14kft flight level seemed marginal as it did not put us into the liquid cloud). Radar echoes over GLEES for the first upwind leg were weak and broken and it appeared that the conditions for the flight were rapidly deteriorating. The liquid cloud over the Snowy range and the Sierra Madre were shallow and broken with distinctly lumpy tops (again in contrast to the solid, smooth-topped liquid cloud layers encountered on the 18th). The downwind leg (also at 18 kft) was similar to the upwind one, but the wave-cloud downwind of the Snowy Range (over Sheep Mtn.) evolved dramatically during this leg and could be seen to fill in rapidly, with a strange vortex near the flight level and dramatic cross-wind undulations along the top of the cloud layer.
We then preformed another pair of legs over the Snow range (both at 17 kft) during which the cloud layer over the Snowy range remained relatively weak while the downwind wave clouds continued to develop.
Overall, the conditions encountered during this were far more complex than for the flight on the 18th and will probably be harder to interpret. The complexity of the upper cloud layer was particularly striking (with up to 4 distinct cloud layers above the aircraft at some times) as was how rapidly the conditions could evolve (evidenced by the rapid development of the downwind wave cloud during a ~2 minute period from when the aircraft passed over GLEES to when it crossed the 1st downwind wave.
----------------------------------------------------------------------------------------------------------
Literal flight notes
185107 Preparing for takeoff. Clouds have built up over the past ~2 hours. thick echoes to >3km above.
185432 Engines on.
185848 Taxiing
190025 Takeoff
190134 Off the ground
190212 Brent to back to open port
190352 Starting radar, mode up+dual down.
190442 Spiral climbout
190550 13kft, 10 deg dewpoint depression
190647 Precip over Laramie.
190700 (From Jeff F.) Terry K. will take off @ 2pm and will fly around us to the north.
190733 In cloud over the Snowy’s
190814 12+kft in ice cloud. Can barely see to surface. Bumpier than previous day.
190923 Turbulence drops
191041 Radar echo to 3km above. Echo tops are amazingly flat
191130 Touch of ice on leading edge of wing (liquid cloud?).
191152 Sunny. Out of mid-level layer. 16.5 kft.
191310 Echoes more broken above. Sunny in cockpit.
191446 Sounding shows cld base @ < 10kft (?).
191623 Discussion Jeff/Brent. Problems with the CCN. Spikes.
198132 Echo-tops @ 24kft, very well defined.
192023 Heading towards GLEES. Clouds/echoes clear below.
192200 Heading towards GLEES @ 23kft & still climbing slightly.
192625 Starting down again. Over GLEES. Solid echoes below, can’t see to sfc.
192803 20kft. Descending
192907 Can see LE of water cloud below (photo)
193116 Entering cloud layer @ 16.8 kft
193208 In cloud. Nice & smooth.
193245 (Jeff F.) liquid water.
193259 (Brent) Lost spike in Vdet on CCN.
193416 More wisps of liquid.
193522 Can see to sfc.
193623 In the Saratoga valley @ ~12kft
193725 Jeff stopping radar file. Crud on 2D-C/P.
193837 Cloud-base @ 9.5 kft.
194036 @ N. end of H. Brent is wetting pads.
Will fly H @ 9kft.
194218 Orbiting near cloud base. Layers above on radar. Weak echo to near sfc.
194317 Waiting for CCN.
194458 Still waiting, Clear above.
194500-194700 (Jeff F) Passed through our exhaust plume.
195154 Change in (track) angle. Now heading down the valley
1954 winds 240 in valley (magnetic)
1955 2-layer structure layer above.
195817 Turn @ S. end of H.
195947 End of turn. Heading north.
200345 Centerpoint of H
200720 In cloud (thin). Cloud base much lower here.
200925 End of leg & into small clouds.
201152 Heading S. to center of leg. in cloud. Did we move to the East ? (probably)
201425 Near liquid cloud wisps.
201608 End of H.
201630 Sounding to 17kft. Then over @ 14kft.
201830 Still in sounding.
202311 Lots o’ little plates ? Lots of 2d-c images have holes in them.
202407 Out of cloud. Smooth tops.
202611 End of turn. Coming over GLEES1 @ 14kft.
202935 Columns & dendrites (Jeff F.)
203112 Out of cloud. Cloud-tops @ 14kft.
203245 Over GLEES, can see to Sheep mtn.
203433 Some turbulence
203500 Some virga from upper layer
203600 ~12nmi from GLEES for downwind leg of H
203811 Descending to 9kft for leg
204018 Passing E of Jelm mtn.
204118 Almost looks like mammatus from upper layer to south
204213 Starting H from S. end.
202649 clouds more broken above. Passing N. end of Sheep mtn.
204809 Funky cloud (lenticular) over Elk mtn.
205309 Bumpy approaching N. end of H
205756 Echo to sfc. Blowing snow (?) (Jeff F.)
205942 End of H. Climbing.
210152 Passing over LAR.
210814 Over GLEES, echoes weak. Conditions getting marginal.
213808 Echo separating from ground.
211355 Nice stellars (2D-C)
211551 Edge of water cloud below. Over (Saratoga) valley
211817 90-270 @ end of leg. @ 17kft can barely see to sfc.
211944 Starting E-bound leg/ new radar file started., @17kft again.
212137 Can see cloud tops heading down above us (on radar).
212374 Sunny
212342 Wave cloud downwind & over Elk mtn. (to left)
213152 Turn @ East end of leg
213419 Starting pass over the mountains
214406 Entering cloud.
214835 Upper level cloud still thick. Can see to sfc.
215058 90-270. Starting new radar file
215407 End of leg.
Returning to LAR.