2014 CIRA Seminars
The representation of cloud microphysics continues to be a source of uncertainty in atmospheric models. Traditionally, microphysics schemes partition ice-phase particles into pre-defined categories with prescribed bulk characteristics. This approach, used in nearly all existing schemes, is intrinsically restrictive and imposes the need for conversion between categories, which is poorly constrained and often unphysical. A fundamentally different approach is proposed and serves as the basis for a new bulk microphysics scheme.
The upper troposphere and lower stratosphere (UTLS) is a region of complex dynamical, chemical and radiative characteristics, with strong gradients in trace species and enhanced climate sensitivity to changes in water vapor, ozone, aerosols and clouds. The observational studies of this region highlight the complementary relationship between dynamical meteorology and atmospheric chemistry. The knowledge of the dynamics from the global scale to processes in the storm scale is essential for understanding the chemical composition.
In October 2012, Hurricane Sandy went on a costly and deadly rampage that began in the Caribbean, and ended after transitioning to a post-tropical cyclone, making landfall in New York. Along the path of its historically unprecedented track, Sandy caused 147 direct deaths, and in the US impacted 24 states and resulted in excess of $50B in damages. In 2013, as a part of the 'Hurricane Sandy Disaster Relief Supplemental,' Congress included funding for NOAA to enhance and accelerate the development of our global weather modeling systems.
The Volckens group conducts research on air pollution at the interface of engineering and public health. In this talk, I will present preliminary results from the (ongoing) Fort Collins Commuter Study, a 5-year project funded by the National Institutes of Health, that aims to improve our understanding of exposures and health effects from traffic-related air pollution. The daily commute, whether by bicycle, motor vehicle, or other mode, is an experience shared by nearly all working individuals.
About half the CO2 emitted by burning fossil fuels is removed from the atmosphere by sink processes, dramatically reducing the rate of accumulation, but quantifying and predicting future sink behavior (especially on land) has proved difficult. Measurements of small variations in atmospheric CO2 are an important source of information about sinks, requiring an accurate account of the influence of atmospheric transport.
During the lifetime of some intense tropical cyclones (TCs), rainbands in the inner core of the storm coalesce to form a ring of convection around the pre-existing eyewall. The formation of this ring, known as the secondary eyewall, is followed by characteristic changes in storm intensity and structure known as an eyewall replacement cycle. While the general behavior of secondary eyewalls is known once they form, the dynamics of their formation remain unclear.
Abstract coming soon
The Nightfire algorithm detects and characterizes sub-pixel hot sources using multispectral data collected globally each night by the Suomi NPP Visible Infrared Imaging Radiometer Suite (VIIRS). The spectral bands utilized span visible, near-infrared (NIR), short-wave infrared (SWIR) and mid-wave infrared (MWIR). The primary detection band is M10, centered at 1.6 um. Without solar input, the M10 spectral band record sensor noise, punctuated by high radiant emissions associated with gas flares, biomass burning, volcanoes, and industrial sites like steel mills.
Persistent satellite observations are essential for monitoring and understanding Earth's environmentally sensitive and rapidly changing Arctic region. This seminar describes compact wide field of view imagers onboard satellites in a highly elliptical orbit (HEO) that would stare at the Arctic and collect multispectral, high dynamic range visible and near-infrared imagery with sensitivity similar to the VIIRS Day Night Band (DNB).
The second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2), carried out in 2009 and 2010, was designed to obtain simultaneous observations of wind and thermodynamic fields within tornadic and nontornadic supercells using an armada of instrumented vehicles and mobile radars. In addition to understanding tornado formation, VORTEX2 scientists also hoped to learn more about the processes governing tornado maintenance and demise; such knowledge is important for improving tornado warning precision.
Abstract coming soon
A new modeling technique, known as base-state substitution (BSS), is introduced as a novel way to approximate environmental heterogeneity in idealized simulations. After a certain amount of model run time, base-state substitution replaces the original horizontally homogeneous background environment with a new horizontally homogeneous environment while maintaining any perturbations that have developed during the preceding simulation.
Abstract coming soon
Aerosols influence cloud and precipitation development in complex ways due to myriad feedbacks at a variety of scales from individual clouds through entire storm systems. This paper describes the implementation, testing, and results of a newly- modified bulk microphysical parameterization with explicit cloud droplet nucleation and ice activation by aerosols.
In this talk I will show that large-scale afforestation in the northern mid latitudes warms the Northern Hemisphere and alters global circulation patterns in climate model experiments. An expansion of dark forests increases the absorption of solar energy and increases surface temperature, particularly in regions where the land surface is unable to compensate with latent heat flux due to water limitation.
2013 CIRA Seminars
The prediction problem in geophysical fluid dynamics typically relies on two complementary elements: the model and the data. The mathematical model, and its discretized version, embodies our knowledge about the laws governing the system evolution, while the data are samples of the system's state. They give complementary information on the same object. The sequence of operations that merges model and data to obtain a possibly improved estimate of the flow's state is usually known as data assimilation.
Interaction of southwesterly wind surges over South China Sea and the steep terrain of Taiwan during the Meiyu (May and June)period of the East Asian summer monsoon often produce severe heavy rainfall and flash floods. The Southwest Monsoon Experiment (SoWMEX) / Terrain-influenced Monsoon Rainfall Experiment (TiMREX) is a cooperative field observational programs conducted jointly by the scientists of United States and Taiwan to study the mesoscale environment and the precipitation characteristics of these heavy rain storms.
Bark beetles and wildfires are natural components of Rocky Mountain forested landscapes. The increased incidence of drought in the coming decades will both make trees more susceptible to insect infestations and extend the length and severity of the fire season. I will describe how Colorado Front Range landscapes have changed following recent outbreaks and fires, and speculate on what we might expect to see in our future forests.
It is widely acknowledged that there has been only modest improvement in tropical cyclone intensity forecast skill despite ongoing efforts to focus research in that area.
This seminar will provide a discussion in the aerosol-cloud-precipitation interactionsthrough reviewing my past and current works using satellite observations and high-resolution modeling. Topics will coverfrom an aerosol-marine low clouds interaction to an aerosol-deep convective clouds interaction by comparing the observational and modeling studies, and also discuss the issues in these approaches. These issue and solutions has motivated me toward a recent topic: fusion of mesoscale modeling and satellite observations through multi-instrumentsatellite simulators.
The impacts of cloud microphysical processes on prediction of tropical cyclone environments, track, intensity, and structure are examined for two microphysical parameterizations using the Coupled Ocean / Atmosphere Mesoscale Prediction System -Tropical Cyclone model. The control microphysical parameterization is a relatively typical single-moment scheme with five hydrometeor species: cloud water and ice, rain, snow, and graupel. An alternative newer method uses a hybrid approach of double-moment in cloud ice and rain and single moment in the other three species.
Satellite-based retrievals are essential for understanding and monitoring climate. A direct combination of measurements from different satellites through collocations allows for a variety of applications. For similar sensors, we can perform intercalibrations. For sensors based on different techniques, we can learn about different instrument capabilities, we can create new retrievals, and more.
Stratospheric aerosols are important climate forcers as they reflect a part of the incoming solar radiation, thereby cooling the earth surface and troposphere, and absorb a part of the outwelling terrestrial radiation, thereby heating the stratosphere. In addition they are important players in stratospheric ozone chemistry as they reduce the abundance of strato-spheric nitrogen oxide radicals. Volcanic eruptions can modulate the stratospheric aerosol surface area density, which is a measure of these radiative and chemical effects, by more than an order of magnitude.