University of Wisconsin-Madison /Atmospheric and Oceanic Sciences Research Areas
Areas of research activity in AOS can be classified in three ways, according to disciplinary area, methods, and applications. The following short descriptions and associated faculty names can be used to guide your choices on the interest checklist submitted with your application.
The study of the fluid motions of the atmosphere associated with weather and climate. In atmospheric dynamics, the fluid is regarded as a continuous medium, and the fundamental laws of fluid mechanics and thermodynamics are expressed in terms of partial differential equations involving the fluid velocity, density, pressure, and temperature. Atmospheric dynamics is often subclassified according to the scale of the motion. For example, mesoscale dynamics pertains to circulations on scales of 10s to 100s of km, often in association with convective storm systems, including tropical cyclones; synoptic dynamics usually pertains to the structure and evolution of extratropical cyclones and other circulations having a horizontal scale of 100s to many 1000s of km; global scale dynamics pertains to circulations on scales of 10,000 km and above.
The study of the chemical constituents of the atmosphere, their sources, sinks, and reactions, and their role in pollution, radiation, cloud physics, the ozone layer. The discipline of atmospheric chemistry includes fields measurements, computer modeling, and laboratory measurements, and requires and understanding of the interaction of the atmosphere with the biosphere and anthropogenic influences.
A subfield of meteorology generally concerned with physical processes not explicitly involving atmospheric motions. The principal areas of atmospheric physics addressed in this department include atmospheric radiative transfer and the physics of clouds and precipitation. Atmospheric radiation plays two very distinct roles: it is involved in the exchange of energy between the earth and the rest of the universe and between levels of the atmosphere; it also carries information about the state of the earth's surface and atmosphere to remote sensing instruments on weather satellites. Cloud and precipitation physics covers the processes by which particles of condensed water in the atmosphere evolve and, possibly, fall out as rain or snow. Cloud processes are important both for the water cycle and for atmospheric energetics (including radiative transfer) on scales ranging from individual thunderstorms to the global climate.
The biosphere -- the living shell that surrounds our planet -- interacts with the atmosphere and oceans in profound ways. Shifts in weather and climate can have strong effects on organisms and whole ecological systems, ranging from local farm fields to global ecosystems. However, we are increasingly realizing that changes in ecosystems -- whether from our land use practices, such as deforestation, or naturally occurring shifts in vegetation cover -- can also affect the chemistry and physics of the atmosphere and the whole earth system. Research in this area focuses on the two-way linkages between the biosphere and the atmosphere, using a variety of techniques -- numerical modeling, remote sensing and field observations. Current graduate research projects in this area range from local field-level studies in Wisconsin, to field campaigns in the Amazon Basin, and global modeling and remote sensing studies. Other aspects of this work connect to other, real-world environmental problems in water resources, food security, and human health. Much of our work in this area is done collaboratively with the Center for Sustainability and the Global Environment (SAGE), the Center for Climatic Research (CCR) , the Department of Soil Science, and the Department of Forest Ecology and Management.
Boundary layer, including air-sea interaction
The boundary layer is the thin "skin" through which heat, moisture, and momentum are exchanged between land or ocean surfaces and the free atmosphere. The primary mode of transport through the boundary layer is via turbulent motions, which in turn are influenced by a combination of wind, surface roughness and surface-air temperature differences. Boundary layer research often focuses on accurately measuring and parameterizing the rates of turbulent exchange as functions of the above variables.
Climate dynamics and climate change
Climate research involves defining the physics of many components of the climate system, including the atmosphere, the ocean and the land, observing, modeling and understanding these components as an interactive system, and obtaining appropriate observational information to define the climate and its changes. We have ongoing studies of El Nino and the Southern Oscillation (ENSO), Pacific Decadal Oscillation, North Atlantic Oscillation and other climate variability. We study paleoclimate changes going back thousands to hundreds of millions of years into the past; we investigate future climate changes and their possible societal impacts; we also study paleoclimate and recent climate observations and use these in conjunction with comprehensive climate system models to try to understand the characteristics and physics of climate variations on many time scales. Much of the work on climate research is carried out in collaboration with the Center for Climatic Research (CCR) .
Marine biogeochemical cycles
Important atmospheric constituents are constantly exchanged with seawater and the ocean biosphere. For example, about 25% of the carbon dioxide accumulating in the atmosphere due to human activities is removed from the atmosphere by dissolution in the ocean. In addition, carbon is actively cycled through ocean ecosystems and circulated in ocean currents. Oxygen, nitrogen, and phoshorus are other critical components of ocean biogeochemical and carbon cycles, but these are generally less well understood. Among other things, this research is expected to lead to an improved understanding of the role of biogeochemistry in past, present, and future climate. More information about the global carbon cycle can be found at: http://carboncycle.aos.wisc.edu
Ocean circulation and dynamics
The ocean occupies over 70% of the earths surface. The ocean is the "flywheel" of the climate system, because it can store heat thousands of times that of the atmosphere; it is also a major sink for global carbon. The ocean has been known to play a fundamental role in climate variability of various times scales, from interannual ENSO to thousands of years of glacial-interglacial cycles. Current research in ocean circulation and dynamics involves the modeling and observational analysis of the ocean currents, temperature and salinity and how their changes affect the heat transport and climate variability. Much of the work on ocean dynamics is carried out in collaboration with the Center for Climatic Research (CCR) .
Diagnostic analysis of observational data
The starting point for any forecast, and for that matter any investigation into atmospheric or oceanic behavior, is measurements. Sometimes we are concerned with data obtained from the global network of operational weather stations; at other times, we might be working with a set of highly specialized surface, aircraft, and satellite observations obtained during a field campaign. Either way, the purpose is to diagnose the state of the atmosphere or ocean and to shed light on the relevant processes. Diagnostic analysis also involves making allowances for the quality of the data, and developing new techniques for combining measurements in a way that illuminates physical and dynamical processes without reading more into the measurements than is really there. Most of the time, diagnostic analysis is undertaken in support of theoretical or modeling studies.
Instrument design and evaluation
Although basic measurements of temperature, humidity, wind, and other common variables have long been possible using very simple technologies, modern meteorological research increasingly relies on highly specialized measurements using sophisticated instruments. Many of the most significant recent advances have occurred in the area of remote sensing instrumentation for ground-, aircraft-, or satellite-based observations of the atmosphere and ocean. The design and testing of measurement systems often requires a combination of meteorological insight and engineering know-how, as well as an aptitude for "hands-on" work with hardware and test instruments. Examples of important new research instruments developed in this building include the Atmospheric Emitted Radiance Interferometer (AERI) and advanced lidar systems for observing atmospheric structure and cloud and aerosol properties.
The use of computer programs to simulate complex physical processes by way of numerical approximations to the relevant equations. Examples in AOS include
- Chemical Transport Modeling (Hitchman, Holloway)
- Climate and earth system modeling (Holloway, Vimont)
- Cloud modeling (Back, Tripoli, Wang)
- Ecosystem and biosphere modeling (Desai, Kucharik)
- Numerical weather prediction (NWP) models and assimilation (Martin, Morgan, Tripoli)
- Ocean modeling
- Radiative transfer modeling (Ackerman, Key, L'Ecuyer, Petty)
Atmospheric remote sensing refers to the estimation of atmospheric properties from a distance, often by reference to the intensity of naturally emitted radiation or reflected sunlight at selected wavelengths. Common examples include the estimation of atmospheric temperature and humidity profiles and other variables from infrared or microwave instruments on satellites. The development and application of new remote sensing techniques is an important research activity in AOS and in the closely associated Cooperative Institute for Meteorological Satellite Studies( CIMSS).
Historically, a great deal of insight into atmospheric and oceanic processes has been achieved via physical arguments (conservation of energy, momentum, etc.) and mathematical analyses applied to highly idealized systems. Nowadays, detailed numerical models are increasingly necessary for the study of complex systems. However, numerical models are only as good as the physical relationships on which they're based. Furthermore, the full value of numerical simulations is only realized when their results can be understood in terms of a few clearly stated and reasonably general physical principles. Fundamental theoretical investigations therefore remain a cornerstone of the study of atmospheric and oceanic dynamics, radiative transfer, climate dynamics, and many other disciplinary areas.
Often, the purpose of atmospheric/oceanic research has no immediate practical application but arises mainly from the desire for a deeper understanding of how the atmosphere and ocean work. Such research is termed "basic" rather than "applied." Of course, basic research is important because advances in fundamental understanding often do have important practical applications in the long term.
The application of meteorological, oceanic, and climatological insights, observations, and principles to any problem of immediate practical importance for society, industry, agriculture, etc. Our department is actively involved in the following:
- Weather forecasting, nowcasting, data assimilation
The preparation of weather analyses and forecasts for use by the general public, aviation, and/or industry. Modern operational meteorology relies heavily on output from numerical weather prediction (NWP) models, in conjunction with other regional and global data sources, such as satellite and radar imagery and surface and balloon observations. An important area of research in AOS is the optimal assimilation of such data sources into the NWP models.
- Climate impacts and assessment (Desai, Holloway, Vimont)
- Air pollution assessment and policy
Designing strategies to manage air quality demands a knowledge of atmospheric chemistry and transport. These processes are fundamental to the study of atmospheric science, but also link to energy analysis, land use, public health, and regulatory policy. Between AOS and the Center for Sustainability and the Global Environment (SAGE), state-of-the-art methods in atmospheric science are being used to address the challenges of maintaining clean air.
Scientific data products
An important activity in the Cooperative Institute for Meteorological Satellite Studies (CIMSS) is the processing of vast quantities of raw satellite and other data into high quality meteorological data sets that can be archived and distributed to other scientific users, both to meet the needs of basic research and for operational applications, such as forecasting. A key part of this process is the development, refinement, and validation of relevant remote sensing techniques, followed by their application to regional or global data streams from selected satellites.