2018-2019 USAP Field Season
Measurement of stratospheric aerosol to altitudes above 35 km in Austral autumn
Dr. Terry Deshler
Supporting Stations: McMurdo Station
Particles in the atmosphere play key roles in controlling the Earth's hydrologic, chemical, and radiation balances. In the troposphere aerosols provide surfaces for cloud formation, for the absorption of trace gas pollutants, and they either warm or cool the Earth depending on their optical properties. In the stratosphere they provide surfaces for the conversion of chlorine from a passive to an active state which will catalytically destroy ozone, crucial as a filter against damaging UV radiation. Numerous observations of particle formation and dissipation processes have been made from McMurdo Station at 78 S. Recent modeling however has predicted the formation of a previously unobserved particle layer forming in the polar winter stratosphere during the austral polar fall, April-May. This project seeks to test this prediction by completing in situ measurements of the aerosol concentration, volatility, and size in the stratosphere over McMurdo in the austral fall. In addition, the project seeks to assess the contribution of meteoritic smoke particles to aerosol in the middle stratosphere, a contribution for which there are few measurements to confirm. This project takes advantage of recent developments permitting year-round access to McMurdo Station, and the development of smaller, lighter, lower cost condensation nuclei counters allowing (balloon borne) profiles to higher altitudes (>35km).
Field Season Overview
A four-person field team will deploy to McMurdo Station to launch medium sized sounding balloons during two successive austral fall periods. They will launch up to nine balloons during each campaign. The duration and timing of the field deployment is dependent on the winter flight schedule. The preferred launch site - in town, at the north and northwest side of the water treatment plant (WWTP) – will be made available and kept as clear of obstacles as possible to accommodate this science activity. Launch times will have to be coordinated so as not to interfere with SOPP launches at 00Z and 12Z.
During the summer, following each winter balloon campaign, a two-person team and a helicopter will recover payloads. The recoveries are non-technical in nature, so an evaluation will be made during the annual SIP/RSP processes to determine whether two team members will be required to double deploy, or others can be committed to this task. The recovery sites will be on the permanent ice shelf to the south, south-east, of the station and within helo distance of the station.
Year 1 (Winter 2019): During Winter 2019, the team will launch up to nine balloons between April and June 2019.
Year 2 (Summer 2019-20 and Winter 2020): Team members will recover payloads, which were launched during the previous winter, as early as possible in the 2019-20 summer season. Recovery of the instruments and their return to the PI’s institution as early as possible is essential to permit them to be refurbished and returned them to McMurdo Station prior to station close in February 2020. During Winter 2020, the team will again launch up to nine balloons between April and June 2020.
Year 3 (Summer 2020-21): Team members will recover payloads, which were launched during the previous winter.
Major support considerations for this project include: • Winter deployments of four-person team • Second (double) deployment of two-person payload recovery team • Helium Gas – 7000 CF (for nine balloons) • Iridium service • Crary Laboratory space • Vehicle support • Helicopter support
Deploying Team Members