PELTI Flight Report for RF05 and RF06, 16 July 2000

   The objective of this flight was to vary the parameters that control the
LTI's performance to see how the efficiency varies with these things.  We
intended to use dry dust as the test aerosol (haziness and AVHRR indicated
moderate dust), but on our sounding found that all the dust was confined
to the MBL.  We made the LTI {isokinetic/superisokinetic/ subisokinetic},
{turbulent/laminar}, and varied the suction percentage that controls both
enhancement and bend losses in the same way we did with sea salt in RF03.
At the end of each APS period the turbulence profile was measured by moving
the probe into the flow.
   We also arranged to fly horizontal legs at 6 altitudes near the PRIDE
experiment's lidar site on Cabras Island, Roosevelt Roads, Puerto Rico.
We then stopped at Rosie Roads to visit the PRIDE sites and show them our
package of equipment.  The short return flight to STX (on which we did our
common-inlet calibrations) was numbered separately as RF06.


 UTC
15:18   Takeoff for RF05

15:22 to
15:29:36   Sounding up to 2400 m (ENE)
           FSSP concentrations dropped steadily: Dust mostly below 4000'
           Mixed layer about 600 m

15:29:36 to
15:38      Level at 2400 m for LTI flow/pressure-drop test

15:38 to
15:43   Descent to 300 m and turn to the East

Isokinetic LTI with various target sample flow rates
15:59   35 lpm - Minimum bend velocity, Laminar

15:58:18 to
16:13:27?  APS Runs

16:13   Turn to West, still at 300 m

16:15:45 to
16:44:20   120 lpm - Barely laminar, Max bend velocity

16:21:24 to
16:44:20   APS Runs
           Filters exposed, Nuclepore in TAS
           Turn to East, still at 300 m

16:53:20 to
17:21:35   200 lpm -Turbulent

16:59:48 to
17:20?     APS Runs
           Filters exposed, Nuclepore in TAS
           Turn to West, still at 300 m

Subisokinetic LTI - about 50% below isokinetic
17:39 to
17:41   120 lpm - Barely laminar

17:30:18 to
17:41?     APS Runs

Superisokinetic LTI - about 13% above isokinetic
17:43:30 to
17:58      120 lpm - Barely laminar

17:47:445 to
17:52:50    APS Runs
            Fly towards Roosevelt Roads, PR

Lidar Profile 
Six 40 mile NE/SW Legs, 1/2 Mile off Cabras Island, Rosey Roads

18:14:56 to
18:24:30   300 m MSL, nearest lidar at 18:19:28

18:15:14   APS start

18:27:38 to
18:38:46   30 m MSL, nearest lidar at 18:33

18:41:47 to
18:51:50   150 m MSL

18:54:56 to
19:07:00   300 m MSL

19:11:05 to
19:19:20   900 m MSL

19:12:18   Stopped APS average briefly due to cloud encounter

19:22:00 to
19:30      1800 m MSL

19:24:12   APS start.  May be only one 5-minute average

19:31:40   Descent to Land at Rosey Roads, PR End of RF05

20:00 to
22:00   Equipment tours with PRIDE at Hangar 200 
        Jeff Reid showed us the Navajo, set up primarily for radiation obs
        Hal Maring toured us through the Cabras Island in situ and lidar site
   
22:06   Takeoff for Return to STX, Start of RF06

22:11:30   At 2300 m MSL

22:25 to
22:30   Common-inlet Calibration of APSs and Nephs

20:35   Landed STX


Notes:

The DU LTI sample flow readings are again erratic.  John Mullen believes he
can fix this bug with reprogramming Tuesday AM.

We dodged rain shafts frequently at 300 m, so there are numerous small turns
in those legs.  Lynn Russell worked with the pilots to vector near the rain
but not in it to look for small particle Na.

A new approach to sealing the exit flow from the cabin FSSP seems to have
reduced leakage.

The FSSPs again showed very little Wing/Cabin difference when the LTI was
turbulent, but apparent enhancement of the largest particles when laminar.

The APSs again showed that the LTI produces only modestly higher large
particle concentrations  than the other inlets when turbulent, but much
higher concentrations when laminar.

The nephelometers didn't agree very well in the common-inlet cal, and will
need to be recalibrated before the next flight.


Commentary:

   Although we weren't able to test the LTI parameters in dry air as we
had intended due to the low altitude of the dust, we have now done a pretty
complete test of the factors that should control the inlet's performance.
(We may try getting much more superisokinetic in a later flight, however.)
The LTI performs very consistently relative to the other inlets, with higher
concentrations of larger particles.  What we need to look for now in the
last two flights from STX is variable dust concentrations (to see if we can
identify size differences in different layers) and variable sea salt sizes
with altitude above the ocean.  A very deep (up to 250 mbar) dust storm
is predicted for 20-21 July, so we should have an opportunity to look
for different dust distributions.

Barry Huebert
17 July 2000