The
faculty, staff and students in the Department of Atmospheric Sciences at the
University of Washington are engaged in the study of a broad range of
atmospheric phenomena and processes, using methods ranging from mathematical
analysis to field experimentation.
Research projects range in size from small studies involving individual
scientists to large national and international programs involving teams of
scientists.
Research
groups in the department are concerned with Atmospheric Chemistry, Atmospheric
Dynamics, Boundary Layer Processes, Cloud and Aerosol Research, Glaciology and Planetary
Atmospheres, Cloud Dynamics, Precipitation Processes, Storms, Weather Analysis
and Forecasting, Climate, Global change, Airflow over mountains, and other
topics. Some groups maintain
special research facilities for the use of their students. In some of these activities, there is
close cooperation with the nearby Pacific Marine Environmental Laboratories at
the National Oceanic and Atmospheric Administration (NOAA) Regional Center
through the Joint Institute for the Study of the Atmosphere and Ocean (JISAO).
Faculty members often have interests in more than one area, and research
projects frequently involve questions of broad scope which do not fall neatly
into a single category. This is
particularly true of research projects directed toward understanding the
chemical and physical modification of the environment by human activities.
The
major research groups within the Department are described below. A number of specific research topics
currently under study are also highlighted.
Atmospheric
Chemistry
The atmosphere
is chemically complex and evolving due to natural events, biological and
anthropogenic activities; it has fundamental chemical links to the oceans, the
solid earth and the biota.
Anthropogenic perturbations such as land-use and industrial activities
have profoundly modified the chemical composition of the troposphere and
stratosphere, with potentially important consequences on future climate and
living organisms. Examples of such
changes include the formation of an ozone hole over Antarctica since the late
1970s, the observed trends in long-lived greenhouse gases, the change in the
concentrations of tropospheric ozone and acidic deposition due to growing
emissions of hydrocarbons, nitrogen oxides and sulfur dioxide in industrialized
regions.
Laboratory
studies, field experiments and modeling activities by atmospheric chemists at
the University of Washington are directed at determining chemical composition
and chemical processes in the atmosphere and in turn their effects on the
atmosphere, and on a larger scale the biogeochemistry of the earth. The laboratory and experimental
research deals with trace gas measurements and physical, chemical and optical
properties of particles. Global
models of atmospheric chemistry and climate use these observations to improve
their predictions of future changes in atmospheric composition, and also guide
the development of analytical techniques and the logistics of large-scale field
measurement programs.
Atmospheric
dynamics involves observational and theoretical analysis of all motion systems
of meteorological significance, including such diverse phenomena as
thunderstorms, tornadoes, gravity waves,tropical hurricanes, extratropical
cyclones, jet streams, and global-scale circulations. The immediate goal of dynamical studies is to explain the
observed circulations on the basis of
fundamental physical principles. The practical objectives of such
studies include improving weather prediction, developing methods for prediction
of short-term (seasonal and interannual) climate fluctuations, and
understanding the implications of human-induced perturbations (e.g., increased
carbon dioxide concentrations or
depletion of the ozone layer) on the global climate.
The Department has
active research programs studying problems on the global scale, the synoptic
scale, and the mesoscale. Research
on global-scale problems includes many topics related to climate change and
climate variability, stratospheric dynamics, and the general circulation. Research on the synoptic scale focuses
on the development of extratropical cyclones, the dynamical influence of the tropopause, rotating
stratified turbulence, and data assimilation. On the mesoscale our efforts are concentrated on topographically
induced flows, orographic precipitation, gravity waves and
stratospheric-troposphere exchange through mixing at the top of deep
cumulonimbus clouds. These
problems are attacked with a combination of theory, numerical simulation and
observational analysis.
(not updated yet) Boundary Layer
Research
The
structure and dynamics of the lowest layer of the atmosphere which comprises
the planetary boundary layer (PBL) are of vital importance for the
understanding of weather and climate, the dispersion of pollutants, and the
exchange of heat, water vapor and momentum with the underlying surface. Processes of special interest within
the PBL include the vertical transfer of momentum, heat and water vapor by turbulence,
and the absorption and emission of radiation at the surface and within the
atmosphere. One focus of the
Boundary Layer Research Group's efforts is on the development and testing of
instrumentation for measuring the turbulent fluctuations of velocity
components, temperature and humidity.
Another focus is on the theoretical analysis and interpretation of
turbulent statistics and flow dynamics.
The importance of instabilities, secondary flows, and coherent
structures has been an important part of this study. The area of air-sea interaction has been a primary area of
research. Several large
experiments have been conducted by the department. Present emphasis is on the role of the boundary layer in the
growth and decay of cyclones and satellite capabilities in ocean measurements.
Faculty
and students are engaged in a variety of field and theoretical projects
including the study of surface fluxes, mesoscale variations in boundary layer
structure, and effects of variable terrain and variable seastate. Observations have been made from fixed
towers, floating buoys, ships, tethered balloons, aircraft and satellites. Data from satellite instruments such as
scatterometers and multichannel scanning microwave radiometers are being used
to infer the global structure of the marine planetary boundary layer. Field studies are made jointly with
teams from other universities and research institutes. Departmental researchers have
participated in many international research programs in many parts of the
globe, from the tropics to the Arctic.
Climate Change
As human activity
continues to alter atmospheric composition and begins to change climate on a
global scale, the challenge of understanding the global system comprised of the
atmosphere, oceans, ice and vegetation takes on a heightened sense of urgency.
Climate research is also motivated by substantial economic benefits from
improved weather and climate prediction on time scales ranging from weeks to
seasons or longer.
Faculty and
students in the department are engaged in a number of projects directed toward
a better understanding of climate variability and long-term climate change,
including: dynamics of atmospheric
variability on time scales of weeks or longer and its relation to extreme
events such as droughts and unseasonable warmth or cold; the El Nino phenomenon
in the equatorial Pacific and its effects on global climate; decadal and
century variability in the mid-latitude and polar regions; the predictability
of El Nino and other natural climate phenomenon; long term variability of the
deep ocean circulations driven by gradients of heat and salt and their role in
the uptake of heat and carbon; the role of clouds, aerosols, sea-ice and land
vegetation in determining the sensitivity of the climate system; the problem of
distinguishing between natural climate variability and climate change induced
by human activity; and climates of the past including ice ages and equable warm
climates. The research involves
the analysis of global data sets of all kinds, including in situ data, remotely
sensed data, and data that have been assimilated into a model in order to
produce a consistent global analysis; testing and improvement of global climate
system models; and experiments with an array of numerical models of the various
components of the climate system.
Cloud
and Aerosol Research
Cloud
and Aerosol Research is concerned with three broad areas of research that
overlap in many important ways:
atmospheric aerosols and trace gases, the physics and chemistry of clouds and
precipitation, and mesoscale processes associated with cloud and precipitation
systems.
The
atmospheric aerosol and trace gas studies are concerned with the origins of
various particles and gases in the air and their effects on the atmosphere on
local, regional and global scales.
This has involved the group in airborne measurements in many locations
around the world and in studies of the emissions of particles and gases from
the ocean, volcanos, forest fires
and industries. Recent field
projects have been carried out in Brazil,
the Arctic, The Marshal Islands, Southern
Africa , as well as North America.
For
many years the department has been engaged in studies of the structures of
clouds and the various processes that can lead to precipitation. Although rooted in field observations,
this work includes conceptual and numerical model development. Current studies include the effects of
clouds on the radiative balance of the earth and climate as well as mesoscale studies of cloud
and precipitation systems. One of
the unique aspects of these studies is the blending of synoptic, mesoscale and
microscale analyses. These studies
have led to new conceptual models for the structures of winter cyclones on the west
coast, east coast and central United States. Current projects include the
analysis of a large data set on the structure of clouds in the pacific
Northwest with the goal of improving the representation of cloud and
precipitation processes in mesoscale models (The IMPROVE Project).
These studies are concerned with the
organization of air motions and precipitation processes in all types of clouds,
ranging from oceanic stratus clouds to tropical convection to fronts passing
over mountain ranges.
This area of research emphasizes the analysis of observations of storms
by aircraft, radar and satellite and interpretation of the data via numerical
modeling of the clouds. These
studies aim to help understand the role of clouds and precipitation in the
global atmospheric circulation and climate and to improve the forecasting of
precipitation and severe weather.
Students and faculty often
participate in field experiments to study precipitating cloud systems in
various locations around the world. Recent projects in midlatitudes focus on
the physics and dynamics of rainfall over the European Alps and the Oregon
Cascades. Current work on tropical precipitation includes analysis of
observations with satellite-borne radars and microwave sensors on the TRMM
satellite. Ground based observations at Kwajalein Atoll in the Marshall Islands
are being used to validate and understand the satellite observations. Shipborne
radar is being used to study precipitation in the Indian Monsoon and the
Intertropical Convergence Zone. A project is planned to use aircraft radar data
to study rainband/eyewall interactions in hurricanes.
The
glaciological research in the Department is aimed at understanding local and
small-scale processes related to snow and ice and predicting their role in
regional and global climate. The
structural and optical properties of snow, sea ice, and pure ice and their
interaction with radiation across the solar spectrum and the thermal infrared
are being studied in cold-room laboratories and field projects carried out in
both the Arctic and Antarctic.
Microwave properties of sea ice are being investigated experimentally
and theoretically for application to satellite remote sensing. The heat and mass exchanges involved in
the growth and decay of sea ice, and air/sea interaction in the presence of an
ice cover, are studied by experiments in the Arctic Ocean and by computer
modeling. The wind-driven
circulation of sea ice is studied using drifting buoys. Changes in the statistical distribution
and overall thickness of Arctic
sea ice are being investigated using upward-looking submarine sonar
observations. Researchers from the
Department have been conducting multiplidisciplinary fieldwork in the Arctic
Ocean and adjacent seas since 1957.
Students
in the Department are part of the large and active glaciological community at
the University, which includes members in the Department of Earth and Space
Sciences (glacier dynamics), the Quaternary Research Center (glacial geology,
permafrost, isotope chemistry of polar ice cores), and the Oceanography
Department (polar oceanography).
The Polar Science Center, a branch of the Applied Physics Laboratory, is
dedicated to research in high-latitude oceanography, sea ice processes,
air-sea-ice interaction, and remote sensing of ice and snow, and climate
change.
Mesoscale
Meteorology
Mesoscale
meteorology is the study of atmospheric phenomena with typical spatial scales
between 10 and 1000 km. Examples
of mesoscale phenomena include thunderstorms, gap winds, downslope windstorms,
land-sea breezes, and squall lines.
Many of the weather phenomena that most directly impact human activity
occur on the mesoscale. Research in mesoscale meteorology has been spurred by
recent advances in observational and numerical modeling capabilities that have
greatly
improved the tools used by atmospheric scientists to study mesoscale weather
systems.
Faculty and students in the department
are actively involved in a large number of different research projects in
mesoscale meteorology. These include studies of convective cloud clusters and
squall lines in the tropics and mid-latitudes, studies of precipitation bands
along fronts, the investigation of marine stratus and strato-cumulus over the
sub-tropical oceans, and research on topographically forced flows such as downslope windstorms, the
blocking and channeling of the winds by orography, mountain-wave induced
rotors, and the prediction of precipitation in complex terrain. These phenomena are studied using in
situ observations, remote sensing, and both idealized and highly realistic
mathematical models. Many local
weather phenomena of the Pacific Northwest are also under study in the
department, where a very high resolution weather forecast model for the Puget
Sound region is run twice daily on an operational basis.
Middle Atmosphere Meteorology
The
middle atmosphere (stratosphere and mesosphere) is the region of the atmosphere
between about 12 and 80 km altitude. Studies of dynamical and chemical
processes in this region have greatly expanded in recent years owing to the
impact of human activities on the stratospheric ozone layer, and the coupling
between stratospheric changes and surface climate. The University of Washington has a distinguished record of
research on the meteorology of the middle atmosphere. Research efforts are divided between analysis of
observational data and theoretical studies based on numerical models. A primary area of emphasis is study of
the dynamical interactions between the troposphere and the stratosphere,
including the transfer of momentum and trace constituents across the
tropopause. This effort requires
understanding of the influence of both large- and small-scale wave motions on
the momentum balance and mass circulation of the middle atmosphere. Members of the department are active in
analysis and interpretation of middle atmosphere data from NASA research
satellites. Students and faculty also employ a variety of models, ranging from
global scale circulation models to mesoscale convective storm models, to study
the links between the troposphere and the stratosphere.
Planetary Atmospheres
The behavior of the atmospheres of other planets is of interest in its own right and may provide insights of value in the study of our own atmosphere and climate system. Efforts are focused primarily on Mars. We use computer models and data from recent spacecraft (such as NASA's Mars Global Surveyor) to improve our understanding of the atmospheric dynamics and climate system of Mars. A small effort is also devoted to developing instrumentation for future space missions to measure Martian weather and climate.
The evolution of planetary
atmospheres is a further area of research. Here the goal is to understand the
nature of past atmospheres from the signatures they have left behind. These
signatures can be physical or chemical. For example, on Mars such signatures arise
from the effects of wind erosion of the planet's surface, chemical interaction
of the atmosphere with the surface, and atmospheric loss to space. The chemical
evolution of the Earth's atmosphere is also studied within such a broad,
planetary context. The Earth's
atmosphere is chemically coupled to the biosphere because all the important
atmospheric gases, with the sole exception of argon, are biologically mediated
to some extent. Computer models that incorporate climate and biogeochemical
feedbacks are being developed to understand the past evolution of Earth's
atmosphere. This effort is part of the cross-campus Astrobiology (AB) Program
and benefits from the expertise of AB Program faculty, which covers a wide
variety of relevant disciplines from astronomy to oceanography to microbiology.
Radiative Transfer and Remote Sensing
The rapid growth in atmospheric radiation studies in
recent years is a result both of the increasing use of satellites to monitor atmospheric
phenomena and of the increased emphasis on climate modeling. Because satellites measure only
radiation, the interpretation of their data requires the study of radiative
transfer in the atmosphere.
Because the transfer of solar and terrestrial radiation represents the
prime physical process that drives the circulation of the atmosphere and the
ocean, an understanding of climate and the mechanisms of climatic changes also
requires detailed understanding of radiative processes and the radiative energy
balance in the earth-atmosphere system.
Current and recent research projects include the use of satellite data for microwave remote sensing of sea-surface temperatures, winds, humidity and liquid and ice water content of clouds, infrared remote sensing of upper atmosphere composition and dynamics, evaluation of the influence of clouds on the regional and interannual variations of the earth's radiation budget, and investigation of cloud-radiation interactions and their feedback to the climate system. Surface and aircraft fieldwork includes studies of solar and infrared radiation over the sea surface, microwave properties of sea ice, and light-absorption properties of atmospheric aerosols as well as the evaluations of GCM cloud and radiation parameterizations using ground-based remote sensing and in-situ aircraft observations. Theoretical work is underway to understand the light scattering by
nonspherical ice particles and
aerosols, to explain the radiative properties of snow and sea ice surfaces, to
examine radiative processes in the upper atmosphere, and to study the influence
of radiation on the maintenance of stratus clouds.
Synoptic Meteorology
Synoptic
meteorology deals with the analysis and prediction of medium to large-scale
weather systems, such as extratropical cyclones and their associated fronts and
jet streams. An important aim of
synoptic training is to acquaint the student with the structure and behavior of
the real atmosphere. This is
accomplished formally through coursework and informally through viewing
real-time displays of weather information such as surface reports, satellite
and radar imagery, as well as a wide variety of weather maps and prognostic
charts. The department posseses a
large synoptic facility which includes treal-time access to a wide range of
weather data, sofware systems for their display, a map room with paper maps and terminals, a synoptic
laboratory, and a computer lab with workstations. The department also maintains an extensive weather data
archive, both in digital and paper forms.
Recent
synoptic research in the Department has dealt with such diverse subjects as the
large-scale tropical and subtropical disturbances, extratropical cyclones,
coherent structures in the upper troposphere, numerical weather prediction,
polar lows, the interactions between tropical and extratropical systems, and
the influence of orography on cyclone evolution. Modeling and observational analyses are combined in an
integrated approach to synoptic meteorology.