Atmospheric and Oceanic Diagnostics
AER's
activities in the field of Atmospheric and Oceanic Diagnostics
involve a broad range of studies aimed at understanding the variability
of the atmosphere and oceans on time scales ranging from submonthly
to interannual and decadal. Goals for the group are understanding
the way the Earth works as a dynamic system, including knowledge
of interactions among its components, determining how aspects
of climate vary, and characterizing attributes of significant
weather and climate phenomena, such as the El Nino/Southern Oscillation.
The group has developed models and comprehensive data sets relating
to interests in these areas.
Angular momentum
As part of this research, AER scientists have organized and studied major portions of global weather analyses as well as run and analyzed ocean models. Results of such activities have been used to diagnose the global angular momentum budget, involving momentum exchanges between the atmosphere, oceans, and solid Earth. The work demonstrates that an especially close link exists between variations in the overall strength of atmospheric winds and small but measurable changes in Earth's rate of rotation. Relevant data are available from the Special Bureau for the Atmosphere. Other aspects of Earth motions and orientation are closely related to a combination of atmospheric and oceanic influences.
Sea level and ocean circulation
The study of sea level variability, on scales from days to years, and its relation to changes in oceanic circulation and mass fields is another area of active research in the group. Satellite-based ocean observations and ocean circulation models are being utilized, along with data assimilation techniques, to determine how ocean variability relates to surface atmospheric forcing and planetary global dynamics.
Ocean biogeochemical studies
AER scientists are examining the structure and dynamics of ocean
fronts near the continental shelfbreak to study how the physical
variability of the area facilitates the high biological productivity
near the continental shelf.
Predictability of ocean circulation
Efforts in this area relate to determining the fundamental modes
of variability of the ocean circulation, including its major fronts
and jets, and designing improved methods to predict such variability.
Climate fluctuations
Other AER efforts to diagnose the general circulation are concerned with quantifying the changing heating processes that drive the atmosphere' s energy cycle. Diagnosing climate fluctuations extends to extracting signals in atmospheric variability driven by forcings like snow cover variability, volcanic aerosol loading, urban warming, and greenhouse gas increases. Studying whether climate is becoming more variable is a theme in the group. We are also interested in the dynamic workings of the atmosphere, for example, relating seasonal precipitation to the internal structure of the atmosphere that might change from year to year.
Model and system assessment
Analyses based on modern four-dimensional data assimilation techniques are studied at AER to determine the quality of statistics that may be derived to document the atmosphere's general circulation, especially those related to momentum, energy, and moisture. We have concentrated on results of recent projects that have thoroughly reanalyzed the earlier state of the atmosphere over several decades. In a related vein, the group also assesses the capabilities of different general circulation models to produce realistic results, focusing on the momentum and moisture budgets to do so.
The National Science Foundation (NSF), National Aeronautics and Space Administration (NASA), National Oceanic and Atmospheric Administration (NOAA) and the Office of Naval Research are currently supporting research in the Atmospheric and Oceanic Diagnostics Group.
Atmospheric Angular Momentum and Length of
Day
This graph displays the close connection between the global
angular momentum of the atmosphere derived from wind analyses
(red curve, scale on right) and the observed changes in the
length of day (blue curve, scale on left), after removing low
frequencies, for the year 1997. The remarkable agreement demonstrates
that a close coupling exists between motions of the atmosphere
and the solid Earth. The relatively high values in the latter
half of the year were related to the El Nino event that was
unfolding at the time.
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