Flight Scientist Notes – NASA-06: January 27, 2006: double cross-leg only mission

 

Crew: Kevin Fagerstrom, Bart Geerts, Larry Oolman, Perry Wechsler.

 

two flights:

(a) 21:33-22:59 UTC (~2:30-4 pm) and

(b) 23:58-03:01 UTC (~5-8 pm, only the first ~30 min in daylight)


ground instruments:

Glees: hotplate and WV-1500 (5-channel)

N. Platte Ranch: WV-1100 (2-channel) N41º15’36’’, W106º46’42’’


Flight (a) 21:33-22:59 UTC


waypoints: LAR-14GLEES14-14BAGS13-13GLEW14-14GLEE-14GLEW14-14GLEE14-LAR (2 long legs at 14/13 kft, and 2 short legs at 14 kft)

where:


The wind direction at 14 kft generally was from a southerly direction relative to the flight track: the track was 25-30º clockwise relative to the wind. Wind speed 15-20 kts at 14 kft. Temperature was about -16.5ºC at 14 kft. and -15.0ºC at 13 kft.


Weather: at T/O, light snow over Snowy Range, but Centenial Ridge is visible. A deep cloud producing light snow even over the valley moves to the NE. We intersect the tail end of it on the first Snowy Range traverse. From centennial east, shallow Cu-form clouds dominate, with some WCR echoes, mostly below flt level. Thickening stratiform cloud over Sierra Madre. The sun itself and sundogs are visible. Light snow above and below, especially near the W end (reached at 22:07 UTC). On the way back, the Saratoga is remarkably clear, sun out, and shallow clouds build nicely over the slope of the Snowy Range. The cu-form clouds deepen to flight level near Glees, and the echo intensity increases rapidly along the upslope. The same is observed along the next to flight legs at 14 kft over the Snowy Range, both W-bound and E-bound, although the clouds become more shallow, more broken, and the echoes weaker. Clearly this shallow Cu is NOT seeded from above during the last 3 legs over the Snowy Range. Later, during the LAR ground phase (4-5 pm), some deeper Cu tops are seen poking above the ill-defined stratiform cloud tops (these are shallow or more distant to the W). The flight was generally smooth, with occasional light turbulence in the Cu and in a rotor-like cloud encountered near GLEE just before landing. No liquid water recorded (<0.01 g/kg) except occasionally in the oro-Cu (~0.02 g/kg at most).


Instruments: CCN performance questioned shortly after take-off. At 21:46 UTC it is determined that CCN is not working at all. WC100R data (LWC) are not recorded for a while (till 21:58 UTC?). Al Rodi reported the following GPS issue: PDOPS >3.5 ..."questionable" between 22:10 - 22:24 UTC


Coordination with WMI Cheyenne aircraft (N234K): they took off ~2.5 hrs before us and flew between Baggs and Battle Peak (i.e. east of Sierra Madre). On our long leg out towards BAGS, we fly 1000 ft above them within a few km, at 21:53 UTC. On our return long leg, we fly at 13 kft while N234K moves off to the N and to higher altitude.

17kft. The 17kft altitude was chosen as the approximate top of the solid cloud layer based on the WCR data, although generating heads frequently extended 1km or more above this level. I would also consider including an along-wind, above-cloud pass (if possible) with the radar in dual-downward looking mode to document the flow throughout the cloud layer.


Flight (b) 23:58-03:01 UTC


Waypoints: LAR-14GLEES14-14GLEW13-13BAGS13-13GLEW14-14GLEE-14GLEW14-14GLEE14-14GLEW14-14GLEE17-17GLEW-SRT-14GLEW14-GLEE-LAR (2 long legs at 14/13 kft, and 7 short legs at 14 kft, and 1 short leg at 17 kft).


The points are the same as defined for flight (a). GLEE, GLEES, GLEW, and BAGS are all aligned along 73.5º-253.5º true. SRT is Saratoga approach down to 7800 ft MSL. The track was 20-25º clockwise relative to the wind direction at 14 kft. Wind speed 15-25 kts at 14 kft. Temperature was about -17.5ºC at 14 kft and -15.5ºC at 13 kft.


Weather: only the first 30 min were in daylight (all 3 hrs of forward video were recorded). Very smooth flight, occasionally some very light turbulence. Very little cloud liquid water (<0.05 g/kg).


1. long leg E-W from GLEE: 00:06-00:33 UTC: very stratified echoes, shallow over GLEES and deep (~19 kft or 6 km) near BAGS. Over SRT valley, upper echo belt persists, precip does not reach ground; near BAGS echoes remain elevated as well. This long leg should show double ridge with shallow echoes over upwind side of both ranges.


2. long leg W-E from BAGS: 00:35-00:57 UTC. Echoes stronger, even at ~600 m AGL, but still do not make it to the ground over SRT valley. Deep echo layer (topping near 6 km MSL now stretches further E, but still just shallow echoes over GLEES.


3. short leg E-W 14 kft: 01:00-01:11 UTC: still mostly shallow echoes, with nice orographic echoes below, and clear echo tops.


4. short leg W-E 14 kft: 01:14-01:23 UTC: echo belt aloft stronger, and snow down to ground over part of the SRT valley. Nice orographic enhancement, LWC up to 0.05 g/kg.


5. short leg E-W 14 kft: 01:26-01:37 UTC. deeper echoes over Snowy Range, SRT valley mostly snowfree at low-levels, upper-level echo belt persists


6. short leg W-E 14 kft: 01:39-01:48 UTC: again nice shallow orographic enhancement on upwind side of Snowy Range., and echo extending further east on lee side.


7. short leg E-W 14 kft: 01:51-02:02 UTC: highly stratified deep echoes over Snowy Range, clearing near GLEW, upper echo band persists.


8. short leg W-E 14 kft: 02:04-02:14 UTC: again nice shallow orographic enhancement on upwind side of Snowy Range, and echo extending further east on lee side. No low-level echo in SRT valley.


9. short leg E-W 17 kft: 02:16-02:25 UTC: solid echo below us, and ~ 200m echo tops above us. The echo tops are not sharply defined, and stars are clearly visible above us. T=-24ºC, wind 20 kts from 228º. No low-level echo in SRT valley.


10. SRT approach: we have a down ramp/turn sounding from 17 kft to 7.8 kft between 02:25:37 UTC- 02:35:50 UTC (about 1000 ft/min), and an up spiral sounding from 7.8-14 kft between 02:35:50 UTC – 02:41:40 UTC.


11. short leg W-E 14 kft: 02:45-02:54 UTC: deep highly stratified precip, again nice shallow orographic enhancement on upwind side of Snowy Range, echoes peter out gradually on E side.


Coordination with N234K: none


Instruments: CCN counter worked, although the air appeared quite clear (except above SRT); very little signal at 1.0 supersaturation; more at 1.5 SS. PSPup (downwelling radiance) did not record. No other problems observed.


WCR data: Probably the most interesting observation from the WCR was the very fine layering of reflectivity, first only in the deeper layer aloft, and later extending to 14 kft and lower. Also remarkable are the persistent, relatively weak upper-level echo belt and the low-level stronger echoes over the upwind side and crest of the mountain ridges. This layer merges with the upper layer over higher terrain but the echo separation at earlier times suggests that seeding may be limited on the upwind side.

 

The upward + dual-downward looking configuration of the WCR was used exclusively for this flight. The number of range gates recorded (150 gates or 4.5 km recorded range) was overkill for this flight.