Mission Plan:
Primary Mission : Pre-Langrangian Post Frontal Characterization (Flight #23) Alternate Mission: None Future Mission(s): Lagrangian flights beginning 0630 LDT Friday (8 Dec), possibly extending through 1530 LDT (9 Dec).Aircraft Operations
Take-off Time: Flight #23: 1900 LDT, 7 Dec (0800 UTC, 7 Dec) 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 #23: 1700 LDT, 7 Dec (0600 UTC, 7 Dec) 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: ****IMPORTANT NOTE***** There will be no 1100 AM meeting tomorrow. The international flight from Singapore will occupy the terminal from approx. 1000 to 1200 (noon). Next scheduled meeting is the normal 1400 Daily Planning Meeting. Airborne Mission Scientist: Flight #23: Clarke Flight #24: Huebert Flight #25: Clarke Flight #26: Huebert Mission Scientist: Flight #23: Huebert Flight #24: Durkee Flight #25: Huebert Flight #25: DurkeeShip Operations
Discoverer: Discoverer located at approx 41 24'S 138 25'E at 1200 LDT 6 Dec (0100 UTC 6 Dec). They are now sampling conditions headed southwset bound toward 45S 135E. Soundings have resumed the 6 hourly launch sequence following 3 hourly launches in support of the aircraft closure experiment. The ship is scheduled to move downwind to 145E in support of Lagrangian flights friday morning. See catalog reference below for detailed instrument status. Discoverer Lead Scientist: Tim Bates Southern Surveyor: Southern Surveyor position at 0000 UTC 6 Dec is 46 35'S 149 14'E. They are continuing a 30 hour process station at this location. They will be returning to Hobart beginning late Thursday afternoon. Soundings will continue every 12 hours. 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
Surface Wind 24-h forecast is here
GASP trajectory analysis is here
Synoptic Situaton at 00 UTC Wednesday 6/12/95:
High 1019 hPa south west of Adelaide extends a ridge over southern Tasmania. A 997 hPa low was centred about 350 nautical miles north east of Tasmania and was moving south southeastwards at about 20 knots. The high/low combination consitute a semi-block in our region.
A broad low pressure area persists over the Southern Ocean south of Western Australia. A cold front was located on the eastern flank of this low pressure area along 40S 120E to 50S 143E, moving eastwards at about 30 knots along 50 deg south. Another front was passing through 113E at 50 deg S.
Prognoses:
0-24 hours: The front along 40S 120E to 50S 143E at 00UTC this morning is expected to cross Tasmania and Macquarie Island longitudes overnight with a small but well defined postfrontal ridge. Stratocumulus is likely with this ridge in the ACE area, however, cirrus from the next upstream front is forecast to develop over Tasmania late Thursday.This next front itself is forecast to be 350-400 nautical miles west of Hobart at 0700UTC Thursday.
24-72 hours: By about 1100-1400UTC Thursday the front should have crossed 140E near 45S with the potential for clear air in the post frontal ridge. However, as the ridge moves further east it is expected to build up from the north, which together with a developing low upstream, may cause the postfrontal southwesterly flow to turn northwest. Hence, if a clear air slot does form it may only last 12 to 15 hours with stratus forming in an airflow tending northwesterly during Friday over the ACE area.
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.
FORECASTS FOR TONIGHT AND WEDNESDAY:
Cape Grim: Weather: Chance of drizzle tomorrow morning otherwise dry. Wind: Easing overnight to be westerly/southwesterly tomorrow at around 20 knots.
Macquarie Island: Weather: Rain overnight with the passage of a cold front.Showers following the front, becoming less frequent during the afternoon. Wind: NW winds of about 30/40knots turning Westerly 20/30knots overnight.
R/V Discoverer Weather: Drizzle periods tonight mostly clearing for the day. Light rain possible late tomorrow ahead of the next front. Wind: Northwest winds 20/30 knots to turn south west 10/20knots overnight but then become northwest again late tomorrow morningat 20/30knots ahead of the next front. The next southwest change is likely late Thursday evening.
R/V Southern Surveyor Weather: Light rain periods tonight mostly clearing for the day. Light rain possible late tomorrow ahead of the next front Wind: Northwest winds 20/30 knots to turn south west 20/30knots overnight but then become northwest again tomorrow at 20/30knots as the next front approaches. The next southwest change is likely late Thursday evening.
REVIEW OF PREVIOUS DAY's FORECASTS:
The progs again did fairly well predicting the ridge to move over Tasmania and the approach of a complex of weak fronts into the southwest part of the ACE area. GASP and RASP have had some difficulty with the depth of the low off the NSW coast, but over the ACE area, even these two models have not done badly. As a result, the forecasts have gone much according to plan, with winds and weather being close to forecast on all platforms.
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 Singapore Airlines flight tomorrow morning. There will be NO 11:00am meeting. We will do the update exercise once, at 2:00pm.
