Mission Plan:
Primary Mission : "Ecumenical" stratocumulus (wi Discoverer) Alternate Mission: None Future Mission(s): NoneAircraft Operations
Take-off Time: Mission #28: 0900 LDT, 12 Dec (2200 UTC, 11 Dec) Pre-flight Weather Briefing Time: Mission #28: 0700 LDT, 12 Dec (2000 UTC, 11 Dec) Updates: None Airborne Mission Scientist: Mission #28: Durkee Mission Scientist: Mission #28: HuebertShip Operations
Discoverer: Discoverer reached its final sampling site (45S, 145E) at approximately 1100 LDT today (0000 UTC, 11 Dec). Atmospheric and seawater sampling will continue in this vicinity until 1700 LDT Tuesday (0600 UTC, 12 Dec) when Discoverer departs for Hobart. They will arrive in Hobart Wednesday morning. A regular 4/day sounding schedule will be maintained with the possibility of extra soundings during the intercomparisons with the aircraft. See catalog reference below for detailed instrument status. Discoverer Lead Scientist: Tim Bates Southern Surveyor: Southern Surveyor has completed its cruise and is in port in Hobart. 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 00Z Monday 11/12/95:
Broad trough of low pressure lies near a line 40S 150E to a 988 hPa low just W of Macquarie Island. Trough moving eastwards slowly. The low is directing a strong, cold west to southwest stream over the Tasmania/Discoverer region and northwesterlies over Macquarie Island.
A 1032 hPa high near 40S 108E extends ridges towards 35S 133E and 55S 135E. A high is forecast to form in the northern ridge near 35S 130E whilst the southern most ridge extends across Tasmania during the day.
A cold front near 55S 120E moving northeast at 35knots forecast to be near 46S 130E.50S 142E at 00z and near 46S 140E/52S 150E at 12Z.
The longwave trough appears to be reforming in the area around 130E.
Prognoses:
0-24 hours: The progs are all expecting a strong northwest to southwest stream to redevelop tomorrow, essentially ahead of the next cold front tomorrow afternoon. However, a weak ridge is expected to extend across Tasmania during the morning and this may supress the cumulus field sufficiently to get a deck of SC south of the state. The front will cross the ACE area later in the day.
24-72 hours: The longwave trough appears to be moving only very slowly eastwards and so further fronts are likely to move northeastwards towards Tasmania Tuesday night and Wednesday. A ridge is forecast to redevelop in the Bight region later in the week, gradually moderating winds over the ACE area.
FORECASTS FOR TONIGHT AND TUESDAY:
Cape Grim:
Weather: Showers gradually tending to drizzle in the afternoon. Wind: Chiefly southwest easing to 20/25 knots this evening and 15/20 knots overnight, before turning west to northwesterly tomorrow and gradually increasing to 20/30 knots by tomorrow night.
Macquarie Island:
Weather: A few showers, possibly of hail tonight, easing tomorrow morning and changing to drizzle. Drizzle increasing to rain tomorrow night. Wind: Westerly winds 15/25 knots turning northwest to northerly tomorrow and increasing to 20/30 knots during the afternoon and possibly 35 knots towards evening.
R/V Discoverer:
Weather: Showers with occasional sleet or hail tonight, easing to occasional drizzle tomorrow morning. Drizzle increasing again tomorrow night. Wind: West to southwest winds 15/25 knots tending west to northwesterly tomorrow morning and gradually increasing to 20/30 knots during the afternoon and evening. Northwesterlies possibly reaching 35 knots tomorrow night ahead of the next front. Seas to 2.5 metres, rising to 3 metres tomorrow night. West to southwest swell 3 to 4 metres decreasing overnight but increasing again tomorrow afternoon.
REVIEW OF PREVIOUS DAY's FORECASTS:
The progs successfully picked the position of the thermal trough and as a result, the cumuliform cloud that was predicted for today's mission maintained its form and structure for the duration of the flight. The front near Macquarie moved a little quicker than was anticipated and thus Macquarie had a slightly better day than forecast with little in the way of shower activity. However, hail was reported from near Cape Grim today and the wind forecast was also accurate there, with winds on the Discoverer being slightly lighter than expected - something for which I'm sure they'll be eternally grateful.
Reporter: Barry Huebert
Early this morning, the RAF pilots contacted the company that makes arrangements for fuel at Christmas Island, and were unable to get a response today. (This is not surprising, since during the original arrangements it took two weeks to get a response from the people on the island.) Since we were therefore unable to give RAF an assurance that we could get the fuel for an extra transect flight, and since RAF needed an absolute answer tonight in order to schedule their staff time for maintenance and preparation for departure, we elected to stick with the original schedule of flight days and fly another 9 hour flight from Hobart. We were able to add 2 hours to the return total, however, without violating the pilots' 35-hours-in-7-days rule. Most of thta will be used to extend the flights near Xmas and into the Kilauea plume.
The flight which Phil Durkee has proposed for tomorrow should meet a diverse set of objectives. It is to be flown near Disco (145 E 45 S) in what we hope will be a stratocumulus deck. We will examine soundings from 5 and 8 AM and satellite photos to see if the conditions are right, prior to a 9 AM takeoff. The T/O could be delayed an hour if that would help get the right conditions. It is our last chance to fly near Disco, which comes into port Wednesday.
The flight would include the following:
1. Four level 10 minute radiation legs for Buchholz (above, below, and two in the cloud). This should provide another data point for the "anomalous absorption" debate.
2. 30 minutes of porpoising between cloud bottom and top for Hudson. This will provide good statistics on the variation of droplet number and size with height in cloud.
3. Early and late (different solar intensity) legs just above cloud top, but never entering the cloud. This will help us determine whether stratiform clouds can produce particles in the same manner that today's flight found near cumulus.
4. One 100' circle early and a stack of four circles later in the mixed layer, combined with porpoising across the mixed-layer top and a shorter leg in the next layer up. This flux stack is to take place near Disco, and will serve as an intercomparison of flux measurement methods in winds that may reach 25-35 knots. Shortly after doing the intercomparison, Disco will traverse the area in which we made the measurements, to assess the seawater variability on their way into Hobart.
According to Tony Clarke's report, today's flight was apparently a major success on several fronts:
1. They flew upwind legs and vertical profiles near Cape Grim, in addition to an instrument intercomparison leg adjacent to the station.
2. They did a satellite intercomparison which John Porter had requested.
3. They flew near cumulus early and found no evidence of either sulfuric acid vapor or new particle production, even around 16-18,000' clouds. When they returned after the solar intensity had increased, though, they saw sulfuric acid of 5 x 10+7/cc and large numbers of ultrafine particles. It appears that this flight really nailed the issue of where new nuclei are produced!
If tomorrow's flight occurs as planned, there will be no further meetings nor flights in Hobart. The planned departure time for the C-130 is 8 AM local time on Saturday the 16th.
Of course, we won't know for certain what we learned until we clean up our data and examine it critically. Although there was much less SO2 than we had expected and the boundary layers tended to be multilayered, we have assembled a remarkable data set for assessing the formation and chemistry of tropospheric particles. I'm betting that the ACE-1 dataset will for years be the best characterization of the behavior of particles in the unpolluted troposphere.
I'm really proud of the way this team worked, from the great pilots who could set the C-130 down within a few miles of a balloon, to the RAF crews who achieved a degree of reliability I have never before encountered in a flight program, to the forecasters and dynamicists who repeatedly found us flyable conditions in areas with almost no observations, to the operations people who managed the details of moving people, materials, and data around, and of course to the dozens of scientific groups who kept showing up at 3 AM to go out and make the highest quality measurements that anyone ever has. With rare exceptions this was done with good humor, a high degree of professionalism, and consideration for the needs of people with different talents and training.
Thanks for letting me work with you all.
Barry
