Scientific Objectives in Atmospheric Chemistry
A significant component of research in the Anderson Group for the past three decades has been the development of in situ measurement techniques for the mesosphere, stratosphere and troposphere using aircraft and high-altitude balloons.
The factors that set our strategy for field missions stem from the following considerations:
- The primary questions are selected for their scientific importance and their societal importance;
- An analysis of current scientific progress extracted from aircraft, satellite, and modeling efforts;
- An analysis of emerging and currently existing observational techniques, both in situ and remote, as well as developments in modeling structures;
- An analysis of platforms available on which to deploy these remote and in situ instruments
- The selection of specific hypotheses to be tested by the proposed combination of observations and modeling.
We believe that the strategy for selection of deployments and the tactics of aircraft trajectory selection must be built on the elements stated above. Thus, we have constructed what we believe are key hypotheses by considering the combination of key questions, the current state of understanding, and the available observational and modeling techniques. These hypotheses then set the structure of the missions. On the one hand, the selection of these specific hypotheses represent a judgment on our part that is intendedis offeredas one voice in the debate. On the other hand we have for many years been engaged in the debate over mission selection, are strongly invested in missions such as TC4, and thus these hypotheses are kindred to the primary questions put forward in the latest TC4 document (Toon et al., 2003). Those questions are:
- What mechanisms maintain the humidity of the stratosphere? What are the relative roles of large-scale transport and convective transport and how are these processes coupled?
- What are the physical mechanisms that control (and cause) long-term changes in the humidity of the upper troposphere in the tropics and subtropics?
- What controls the formation and distribution of thin cirrus in the Tropical Tropopause Layer (TTL), and what is the influence of thin cirrus on radiative heating and cooling rates, and on vertical transport?
- What are the chemical fates of short-lived compounds transported from the tropical boundary layer into the TTL (i.e., what is the chemical boundary condition for the stratosphere?)
- What are the mechanisms that control ozone within and below the TTL?
- How do convective intensity and aerosol properties affect cirrus anvil properties?
- How do cirrus anvils, and tropical cirrus in general, evolve over their life cycle? How do they impact the radiation budget and ultimately the circulation?
- How can space-based measurements of geophysical parameters, particularly those known to possess strong variations on small spatial scales (e.g., H2O, cirrus), be validated in a meaningful fashion?