Day: 321 (17 November 1995)
Mission:
Primary Mission : DMS Photochemistry in Cold Air Alternate Mission: Radioactive Closure Profile Future Mission(s) : Possible Sunday (19 Nov 95) flightAircraft Operations
. Take-off Time:Primary 0930 LDT (17th, 2230 UTC) Alternate 1030 LDT (17h, 2330 UTC) Pre-flight Weather Briefing Time: 0730 LDT (17th, 2030 UTC) Updates: 0830 LDT deision, primary vs. Alternate Airborne Mission Scientist: Primary, Huebert Alternate, Clarke Mission Scientist: BoersShip Operations
Discoverer: Discoverer arrives in Macquarie Is. At 1400 UTC 17 Nov. All instrumentation are operational except CO and ammonia. Detailed msmt samples available on catalog. ISS soundings being taken every six hours. Discoverer Lead Scientist: Tim Bates Southern Surveyor: Southern Surveyor in route to Cape Grim. Soundings taken every 12 hours. Trouble with Email link precludes forwarding of status messages but soundings into Melbourne OK.. Southern Surveyor Lead Scientist: Bronte TilbrookSystems Status:
Aircraft: PMS probes are operational. Lidar working on one channel. Work continues on ammmonia sensors ammonia sensors. Discoverer: All major systems on Discoverer are operational. Ammonia and CO systems still being worked on. So. Surveyor: All major systems operational on Southern Surveyor. Cape Grim: Cape Grim installation continues. Most systems are operational and work continues on ammonia, SO2 and The ISS hasoperational OMEGA and profiler. RASS system is down..
GASP trajectory analysis is here
ISSUED :05Z Friday 17/11/95
VALID TILL: 12Z Saturday 18/11/95
Synoptic Situaton at: 00Z Friday 17/11/95.
High 1026 hPa near 41S 146E moving east at 25 knots forecast to be near 37S 170E by 00z tomorrow and east of NZ by tomorrow night.
Low 1006 hPa near 46S 136E moving eastsoutheast at 30 knots forecast to be near 46S 152E at 00Z tomorrow, central pressure 1000 hPa, 48S 162E 12Z Friday night with central pressure about 992 hPa and east of 180E by 12Z Sunday night.
High 1022 hPa near 41S 119E moving east at 20 knots extends a ridge to the far south around 60S 130E. The high is forecast to move to near 45S 126E by 00Z tomorrow , 45S 132E by 12Z Saturday night and 45S 140E by 12Z Sunday night. The ridge to the south is expected to persist and move east slowly with the high.
The strong westerly stream persists south of about 53S with a front expected to pass through Macvquarie about Z.
Prognoses:
0-24 hour progs:
The progs are now quite consistent for the next 24 hours showing the low passing south of Tasmania overnight and some very cold, dry air moving into the southern portion of the ACE area tomorrow morning in the wake of a front likely to move through Macquarie during the early hours of Saturday morning. The high south of Australia is intensifying and the ridge to the far south where there is a significant area of clear (cloud free) air is forecast to move towards 50S 132E by 00Z tomorrow morning. The area of clear air by then, is likely to be closer to 52S 140E.
24-72 hours:
The high looks set to become the dominant feature over the ACE area, intensifying and probably producing a significant area of stratiform cloud west of Tasmania and north of about 50S. Further south, strong to gale force west to southwesterlies are likely to continue, with another front likely to cross Macquarie on Saturday night.
FORECASTS:
Cape Grim:
Weather:
Some light rain developing overnight, easing to a shower or two tomorrow morning.
Wind:
East to Northeast winds 20/30 knots easing to 15/20 knots this evening and turning northwest to westerly. Winds turning southwesterly at 15/25 knots overnight and increasing to 20/30 knots, with a further strengthening to 30/40 knots possible later in the morning. Southwesterlies turning more southerly during the afternoon and moderating slowly.
Macquarie Island:
Weather:
Showers, possibly of sleet or snow at times, increasing overnight and tomorrow morning with the front.
Winds: Chiefly westerly winds 25/35 knots backing cold southwesterly overnight at similar strength. West to southwesterly winds 25/35 knots possibly easing slightly tomorrow morning but likely to tend west to northwesterly later and restrengthen to 25/35 knots.
R/V Discoverer
Similar to Macquarie with winds increasing to 25 to 35 knots this evening. Seas rising 3 to 5 metres. West to southwest swell rising 4 to 6 metres. Beware of the change tonight. If it goes more S/SW'ly it can make the anchorage more susceptible to the swell.
R/V Southern Surveyor
Similar to Cape Grim, although the southwesterlies may not be quite as strong on Southern Surveyor as at Cape Grim.
ACE area:
The cloud free area is forecast to be near 50-52S 139-142E around 00z tomorrow, although the area maybe modified somewhat during the next 12 hours. Extensive areas of stratiform cloud are expected to develop west of Tasmania later Saturday and during Sunday, under the influence of the high pressure system.
REVIEW OF PREVIOUS DAYS FORECASTS: Winds and weather look much as forecast for the Discoverer, but the E/NE'lies at Cape Grim are about 5 knots stronger than forecast with a little more cloud there than was forecast. The GASP prog did a good job for the day.
Reporter Barry Huebert
The primary C-130 mission will be a study of sulfur chemistry in cold, dry air. This mission is aimed at evaluating the partitioning when OH radical attacks DMS at low temperatures. Theories suggest that little SO2, H2SO4 vapor, and NSS should be formed, because at low temperatures the OH addition branch is favored. Our flight profile is designed to observe both mean concentrations and the fluxes of at least DMS and SO2. We will fly four 30 min circular patterns in the boundary layer, in addition to a lidar leg above the study area, two soundings, and porpoising across the diameter at the inversion. Time permitting, we will repeat our lowest circle at 100' above the surface.
This mission depends on being able to reach the clear, cold airmass which is forecast to be at 50-52 S tomorrow. We need minimal stratus cloud, no more than 30% cumulus cloud, and a ferry time of 3 hours or less. Based on the latest satellite picture, a decision will be made at 0830 local whether to take off at 0930. Huebert will be lead scientist.
The alternate mission is a 1030 takeoff for a column closure mission, on which Tony Clarke would serve as lead scientist. This mission depends on finding a clear patch of air within a 2 hour ferry of Hobart. A clear band now south and west of Hobart would suffice if it persists that long. This T/O time would result in missing the morning satellite overpasses, but would be on station for a 1540 local overpass that is quite desirable.
The forecast for Sunday suggests that it will be a good day for a stratocumulus mission west of Tasmania. Since the winds at Cape Grim are likely to have an easterly component, though, it may not be useful for an intercomparison with Cape Grim. Saturday we will begin looking at forward trajectories to assess the likelihood of starting a Lagrangian experiment on 22 November.
