2010 CIRA Seminars
The range of scales and complexity in multiscale, multiphysics systems means that obtaining accurate numerical simulations is extremely difficult. Consequently, there is an increasing - even strident - demand for quantification of error and uncertainty in model predictions. I will describe a powerful general approach for computing accurate estimates and the use of such estimates to mitigate the effects of error, e.g. through adaptive mesh refinement. I will explain the approach in the context of three interesting applications.
2009 CIRA Seminars
The stratospheric circulation (often referred to as Brewer-Dobson circulation) is a mechanically driven global scale circulation that transports mass and constituents (e.g. ozone and water vapor) from the cold tropical tropopause to the warmer extratropical regions. This circulation induces adiabatic cooling within its tropical upwelling branch and adiabatic warming within its extratropical downwelling branch. In the first part of this talk it will be shown that these dynamical effects significantly modify the global tropopause structure.
During the morning of 8 May, 2009, a large bow echo system developed over Kansas and proceeded eastward, producing an extensive swath of severe wind damage from eastern Kansas through southern illinois. During its most intense phase, the bow echo occluded, producing an eyelike structure similar in many respects to tropical cyclones. Indeed, much of the wind damage with this system was associated with an intense (10 mb) mesolow located at the tip of the occlusion, well behind the leading gust front.
Avalanches are significant natural hazards that affect people living in and traveling through most mountainous regions of the world. In Colorado, avalanches kill more people annually that any other natural hazard. Avalanches also have a significant impact on the state's economy as they affect winter recreation, close roads, and limit the movement of goods and services. Each winter the seasonal snowpack develops as a layered structure. Under the right conditions, fractures can propagate along the layer interfaces producing large and destructive avalanches.
The variability of climate features has significant human impacts but is difficult to model and predict. Recent theoretical developments in nonequilibrium statistical mechanics cover a class of simple stochastic models that are often used for climate phenomena. The theory for entropy production is developed for simple stochastic climate models and applied to observed tropical sea surface temperatures (SST). The results show that tropical SST variability is approximately consistent with fluctuations about a nonequilibrium steady-state.
Nitrogen oxides (NOx = NO + NO2) of anthropogenic origin are produced primarily from fossil fuel combustion by motor vehicles, electrical power generation, and industrial processes. Accurate accounting of NOx emissions is crucial for the prediction of the atmospheric formation of ozone and particulate matter. Each of these pollutants is subject to air quality standards in most of the industrialized world.
The geologic record is a fascinating source for surprising information on past warm climates. The climate of the Cretaceous and Eocene (146-34 Million years ago) was exceptionally warm. Crocodiles and Palm trees, which cannot survive a few nights of sub freezing temperatures, could be found in the waters of Greenland and in the middle of present day Northern North America, where current winter temperatures can drop to -30C.
The Madden-Julian oscillation is a robust, well-observed, and easily resolvable (large scale) phenomenon that global atmosphere models are notoriously poor at simulating. Analysis tendencies (ATs) in data assimilation can be interpreted essentially as model physics error fields. Systematic errors in precipitation melting and re-evaporation are easily spotted using time-averaged ATs. Of course, the same information is clear simply from mean state biases.
Societies have been 'at war' with their climate regimes, most likely since the beginning of humankind. They had to devise ways to find or make shelter appropriate to their local climates, find and store foods for long periods on time across the seasons, find and store water, protect themselves from natural climate, water and weather related hazards. That so-called war continues today. But now there are more than 6 billion people on the planet and societies are engaged in activities to feed and improve their well being that have taken a toll on the planet's resources.
The Tropical Tropopause Layer (TTL) is an important region forstratospheric chemistry and tropospheric climate. An overview of the TTLand critical processes is presented, with some recent work on simulatedchanges to the TTL. The TTL is the source region for most stratosphericair, and sets the 'boundary condition' for the stratosphere. Transportpathways may regulate how species get into the stratosphere.
The spatially and temporally coincident Atmospheric Infrared Sounder (AIRS), CloudSat, and CALIPSO instruments observe vertically resolved profiles of key thermodynamic properties like temperature and water vapor (from AIRS), cloud/clear sky discrimination and cloud type and microphysical properties (from CloudSat and CALIPSO). Two avenues of research will be discussed. First, variance spectra of temperature and water vapor are derived and shown to have strong variations with height, latitude, season and surface type.
ENSO is known to affect climate and weather patterns throughout theworld. This influence of ENSO is typically communicated via disturbancesthat travel through the atmospherecommunications which are generallytermed atmospheric teleconnections; however, the precise processesresponsible for these ENSO atmospheric teleconnections are often notfully understood. Here we explore the dynamics of the ENSO atmosphericteleconnection with the North African-Asian (NAA) jet. The NAA jetextends from the subtropical North Atlantic, across North Africa and Asia,to the North Pacific.
The Asian monsoon anticyclone dominates the global circulation in the upper troposphere - lower stratosphere (UTLS) during NH summer, and is linked to persistent maxima in tropospheric pollutants transported upwards by deep convection and confined by the anticyclonic circulation. Satellite observations from the Microwave Limb Sounder (MLS) and the Atmospheric Chemistry Experiment (ACE) are used to document the space-time behavior of carbon monoxide and other pollutants associated with the anticyclone.
Present-day shortcomings in the representation of upper tropospheric ice clouds in general circulation models (GCM) lead to errors in weather and climate forecasts as well as account for a source of uncertainty in climate change projections. An ongoing challenge in rectifying these shortcomings has been the availability of adequate, high-quality, global observations targeting ice clouds and related precipitating hydrometeors.
Sudden stratospheric warmings (SSWs) are dynamically driven events in the polar winter stratosphere that are associated with abrupt regime shifts from strong westerly flow, around the so-called polar vortex, to weak westerlies or even easterlies, as well as a sudden increase in polar cap temperature. SSWs lead to as much as 50 K warming within a few days with important consequences for ozone chemistry amongst other things.
Convective clouds forming over or near large wildfires, sometimes referred to as "Pyro-cumulonimbi", or "PyroCbs," have only recently begun to receive attention in the literature. PyroCbs form in a conditionally unstable environment which is often too stable to support "regular" convection. Aerosols from the fires are lofted by the storm's updraft and can easily be sent into the lower stratosphere, where they may persist for days due to the strong static stability. Although smaller in magnitude, these
Observations show large and coordinated changes are occurring in theArctic climate system. Perhaps the most dramatic of these is a significantdecline in the summer Arctic ice cover. The summer of 2007 wasparticularly striking, being 23% lower than the previous minimum set in2005. Model projections suggest continued and possibly accelerated iceloss into the future.
Everyone knows that climate has always changed. The most recent Intergovernmental Panel on Climate Change (IPCC) assessment report has convinced most climate scientists that humankind is changing the earth's climate and that significant global warming is taking place. For this scientific assessment the IPCC (including our group) recently shared the Nobel Peace Prize with Al Gore.
While tropospheric ozone is only about 10% of the total amount of ozone present in the Earth atmosphere, it is nevertheless exceedingly important for the multiple roles it plays. However, the global height resolved distribution of ozone in the troposphere is largely unknown. The launch on July 15, 2004, of NASA's third of the Earth Observing System (EOS) series, the Aura observatory, carried with it the Tropospheric Emission Spectrometer (TES).
There are many climate change concerns that should be on the radar screen of Americans, but perhaps the two most troubling are related to the sea level rise and drought. The former will be a growing issue for coastal areas, whereas the latter already is an issue for much of the U.S. West, particularly the southern half of the region. The paleoclimatic record highlights that future change could be substantially more challenging than commonly believed.
I will begin with the lectures given in 1962 by Harry Wexler, head of research at the weather bureau, "On the Possibilities of Climate Control." Wexler based his studies of geo-engineering on GCM modeling and recent satellite heat budget measurements. He explained techniques to cool and warm the planet, ways to destroy the ozone layer either inadvertently or with possible harmful intent, and warned about the dangers of climate control.
I will then bring the story up to date to provide historical perspectives on today's climate engineers.
The alpha dicarbonyl compounds glyoxal and methylglyoxal will react with amine compounds such as amino acids and methylamine, all present in clouds and aerosol. These reactions are studied by NMR, SMPS, ESI-MS, and AMS at concentrations down to the uM range. Results indicate that stable N-derivatized imidazole and light-absorbing products form when lab-generated cloud droplets evaporate. Droplets containing either methylamine or methylglyoxal and a corresponding amine / carbonyl reaction partner also form oligomers upon drying with masses observed by HR-ToF-AMS up to m/z = 661.
2008 CIRA Seminars
We use aircraft data on ice particle and water droplet size distributions from seven field campaigns, combined with remote sensing data and a numerical model, to characterize the microphysical properties and processes in deep, tropical maritime clouds. Convection is sampled in pristine to heavily dust laden maritime environments and in single updrafts to hurricanes with peak updraft velocities reaching 25 m/s. Precipitation efficiency and the influence of dust on the microphysical and radiative properties are evaluated.