Mission Plan:
Primary Mission : First flight in Lagrangian series Alternate Mission: None Future Mission(s): Lagrangian flights possibly extending through 1530 LDT (9 Dec).Aircraft Operations
Take-off Time: Flight #24: 0630 LDT, 8 Dec (1930 UTC, 7 Dec) Flight #25: 1900 LDT, 8 Dec (0800 UTC, 8 Dec) Flight #26: 0630 LDT, 9 Dec (1930 UTC, 8 Dec) Pre-flight Weather Briefing Time: Flight #24: 0430 LDT, 8 Dec (1730 UTC, 7 Dec) Flight #25: 1700 LDT, 8 Dec (0600 UTC, 8 Dec) Flight #26: 0430 LDT, 9 Dec (1730 UTC, 8 Dec) Updates: None scheduled Airborne Mission Scientist: Flight #24: Huebert Flight #25: Clarke Flight #26: Huebert Mission Scientist: Flight #24: Durkee Flight #25: Huebert Flight #26: DurkeeShip Operations
Discoverer: Discoverer located at approx 45S 142 55'E at 1530 LDT 7 Dec (0430 UTC 7 Dec). They are now sampling as they proceed downwind to the Lagrangian starting point.. Soundings are being taken every 6 hours until 0900 UTC this evening when they will resume 3 hourly launches. See catalog reference below for detailed instrument status. Discoverer Lead Scientist: Tim Bates Southern Surveyor: Southern Surveyor position at 0000 UTC 7 Dec is 45 30'S 145 30'E. They are completing a 30 hour process station and aquashuttle test at this location. They will be in port at Hobart early Friday morning. Soundings will continue every 12 hours until arrival. See catalog reference below for detailed instrument status. Southern Surveyor Lead Scientist: Bronte Tilbrook
48 hour MSL P Prognosis is here
72 hour MSL P Prognosis is here
Latest Visible Sat Picture is here
GASP trajectory analysis is here
Synoptic Situation at 0000 UTC:
High 1018 hPa located over Victoria extends a ridge to western Tasmania behind a weak front which extends from eastern Tasmania to well south of New Zealand. A 996 hPa low was centred about 500 nautical miles east of Tasmania and was moving south southeastwards. A broad low pressure area persists over the Southern Ocean well southwest of Western Australia. A cold front was located on the eastern flank of this low pressure area along 40S 126E to 50S 132E, moving eastwards at about 30 knots along 50 deg south. Substantial clear areas are developing behind this front.
Another front was passing through 115E at 50 deg S.
Also of interest is a low pressure area centred over southern parts of Western Australia
Prognoses:
00 to 24 hours: The front along 40S 126E to 50S 132E at 00UTC this morning is expected to cross 46S 145E between 1800 and 2100 UTC 7 Dec (5am to 9am Friday morning local time). All prognoses suggest that the post frontal ridging will be definite but not strong for this period, with dry air in most of the troposphere behind the front.
24-72 hours: However, as the high moves further east it is expected to build up from the north, which together with a developing low upstream, should cause the postfrontal west to southwesterly flow to turn northwest. Hence, the currently identified clear air may cloud over with stratus forming in an airflow tending northwesterly during late Friday over the ACE area.
Additionally, cirrus may well begin streaming southwards from the low centred over the south of Western Australia at some time during Friday, or early Saturday at the latest.
The upstream low pressure area is expected to spawn a major low over the weekend, well south of Australia. However, this will lead to windy conditions over Tasmania with a cold front to cross about Saturday night. An unstable (convective) westerly airflow is likely for the ACE area for Sunday.
DAILY FORECASTS ISSUED : 0700 UTC Thursday 7 December 1995 FOR: Tonight and Friday 8 December 1995
Cape Grim: Cloudy periods but fine. 10 to 15 knot westerly winds to tend north west overnight and then northeast during Friday.
Macquarie Island: Weakening cold front to cross Friday morning. Cloudy with light rain or drizzle overnight and at first Friday. West to south west winds at 20 to 30 knots to become northwest overnight then return west to southwest after the front.
R/V Discoverer Overcast with light rain developing this evening but mostly clearing to fine with little cloud following the passage of the cold front between about 5am and 9am Friday morning. West to south west winds of 10/20 knots follwing the front, turning northwest by Friday afternoon.
R/V Southern Surveyor: Cloudy with drizzle or light rain developing overnight. West to northwest winds 15/20 knots.
REVIEW OF PREVIOUS DAY's FORECASTS: By and large the prognoses gave good guidance.
Reporter: Barry Huebert
Much of the discussion today concerned what appears to be our last opportunity to conduct a Lagrangian experiment. The front which will pass 140 E late Thursday night may well be our last chance, since a deep low is developing to the southwest. We have abandoned the idea of doing a stratoQ mission on the 7th, to ensure the best chance of success with this Lagrangian experiment.
We hope to fly a total of four flights, three with the balloons. After Don Thornton expressed strong opposition to using the four flights as originally scheduled for this Lagrangian (there has not been much change in SO2 in the boundary layer flights to date, and he feels that the inability to measure DMSO and DMSO2 invalidates sulfur budget studies), we finally took a vote on the use of the remaining hours. It was overwhelmingly in favor of trying to coordinate four flights, if we can do so, with only one or two votes to the contrary among those scientists who elected to attend the meeting.
To minimize the chance that Friday's daytime flight will be in cloudy air, we have decided to do a pre-Lagrangian survey flight Thursday night in (approximately) the postfrontal air that we will be studying Friday. We will launch the balloons Friday morning into what is clear air at that time. The pre-Lagrangian flight will include a series of level legs into the frontal region, looking for high CN concentrations and mapping the dynamics, potential vorticity, and aerosol microphysics well enough (hopefully) to define the altitudes from which the high postfrontal CN concentrations come. While we don't know whether these postfrontal nuclei represent a globally-important source of particle number in the boundary layer, they certainly are a reproduceable phenomenon which Bates, Covert, Kapustin, et al. have observed and which deserve further study. Hopefully Thursday night's flight will give us an idea of their origins. Clarke and Businger will lead that flight.
Friday norning we will then tag a parcel of air and follow it for at most three flights. Our intention is to locate Disco such that the C-130 is already in the air before the balloons are launched, but that may or may not work, given the uncertainty in timing from frontal passage and clear-air passage forecasting. The nominal launch time would be 2200-2300 CUT Friday morning, with the C-130 on station doing circles slightly to the north of Disco from 2000 to 0300 Friday. We would again try to place the circles 4-5 miles to the north of the balloon track. (Once those circles are begun, it will be important that Disco not move north!) At present it loks like 45 S 145 E is a good launch point, but we hope to refine that tomorrow afternoon.
Disco would actually launch the balloons when the large clear patch arrives (whatever time that happens to be). Jim Moore explained that it is common to have a small clearing behind fronts (in which the undisturbed high CN concentrations are probably located), but that that air almost certainly clouds up prior to the onset of broader subsidence farther behind the front. Our best potential for maintaining a clear study area, then, is in the larger clear area, not where the high CN first appear. Since this launch will almost certainly be in the daytime, it seems best to have the launch time chosen in close consultation with the people making satellite observations of clear areas.
All three balloons should be used in this mission, since no other opportunities seem likely prior to the end of the experiment. The closer they can be launched to the same time, the better. We recognize that the normal fill-and-ballast time is about an hour, but any efforts that can be made to get a couple of balloons out within 15 minutes of one another will increase the value of the data. Three quite close would permit an independent computation of divergence, for comparison with the aircraft measurements. Obviously, we'll take what we can get in this regard.
On one of the flights in this series, we will fly a stack of two 60 minute circles and a stack of four 30 minute circles. This will allow a test of Lenschow's theory that larger circles can greatly reduce the uncertainty in entrainment calculations. Clearly this will put us into a slightly larger airmass than the 30 minute circles, but in the context of the uncertainty in airmass identity that we already face, it may not be too serious.
If we fly four 9 hour flights in this series, we will have 20 hours remaining. Today we also spent a fair amount of time discussing the best way to understand the apparent production of aerosols at the tops of stratoQ. Clearly the stratoQ mission needs to focus more on the air just above the inversion than we have in the past, but with continuing attention to measuring the boundary layer fluxes and entrainment rates. Since early next week may offer opportunities to study cumulus detrainment and its contribution to the production of aerosols in the free troposphere, it is likely that we will use virtually all our remaining flight hours on these last two objectives.
Tentative schedule (CUT):
Thursday: 0800 C-130 T/O for Pre-Lagrangian Postfrontal Aerosol Study (Flt 23) Friday: 1700 Land Hobart 1930 C-130 T/O for first Lagrangian flight (Flt 24) 22-2300 Nominal balloon launch window 0430 Land Hobart 0800 C-130 T/O for second Lagrangian fight (Flt 25) Saturday: 1700 Land Hobart 1930 C-130 T/O for third Lagrangian flight (Flt 26) 0430 Land Hobart
Due to the Lagrangian flights there will be NO 11:00am meeting tomorrow. We will do the update exercise at the pre-flight briefings.
