Research Overview

The group's primary research objective is to understand the variability of the atmosphere to better interpret and predict changes within a range of climates. To reach this end, we use multiple data types: observations, reanalyses, 2-D models, idealized general circulation models (GCMs) and state-of-the-art climate models. Please see below for details on some previous as well as ongoing research.

Current Research Projects

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Visualization of an atmospheric river impacting Alaska on August 12, 2002.
The red outline denotes the area identified as an atmospheric river by
Bryan Mundhenk's detection algorithm.

Title: Forecasting North Pacific Blocking and Atmospheric River Probabilities: Sensitivity to Model Physics and the MJO
Funding Body: National Oceanic and Atmospheric Administration, Climate Program Office, MAPP
Brief Description: Atmospheric rivers (ARs) are intense synoptic-scale plumes of tropospheric water vapor that can lead to extreme precipitation and flooding when they make landfall. These features cause extreme flooding events not only along the west coast of the contiguous United States (CONUS), but also in Canada and Alaska (see figure on the right). The ability to forecast ARs would provide society with advanced knowledge of their extreme impacts. Recent work by the our team demonstrates an inverse relationship between winter-time ARs hitting Alaska and CONUS, driven by the presence of a blocking anticyclone over the east Pacific that acts to divert the ARs away from CONUS and into the Gulf of Alaska. The potential exists to forecast the probabilities of North Pacific blocking and AR occurrence through knowledge of the Madden-Julian oscillation (MJO). The overarching goal of the proposed work is to quantify the extent to which east Pacific blocking and AR probabilities can be skillfully forecast at lead times of multiple weeks through their dynamical link with the MJO, including an explicit investigation of how AR prediction skill varies with a model's ability to forecast the MJO.

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Location of Lake Mendocino and the Russian River.
Figure from the CW3E FIRO website.

Title: AR detection algorithm application and synoptic influences to support FIRO
Funding Body: funded by CW3E sub-award under the Lake Mendocino Forecast Informed Reservoir Operations (FIRO) Preliminary Viability Assessment Work Plan
Brief Description: FIRO (Forecast-Informed Reservoir Operations) is a proposed management strategy that uses data from watershed monitoring and modern weather and water forecasting to help water managers selectively retain or release water from reservoirs in a manner that reflects current and forecasted conditions. FIRO is being developed and tested as a collaborative effort focused on Lake Mendocino that engages experts in civil engineering, hydrology, meteorology, biology, economics and climate from several federal, state and local agencies, universities and others. Our group is supporting FIRO, through a subward under the UCSD Scripps Institution of Oceanography and CW3E, by designing an atmospheric river detection algorithm assessment and comparison methodology and investigating the dynamical links between atmospheric rivers impacting Lake Mendocino and atmospheric variability over the North Pacific.

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The Northern Hemimsphere eddy-driven jet stream put together by the NASA
Scientific Visulatization Studio. A video of the jet-stream's' evolution can be found here.

Title: Seasonal Sensitivity of the Midlatitude Circulation to Future Climate Warming
Funding Body: National Science Foundation, AGS
Brief Description: The climate change induced by increases in greenhouse gas concentrations is generally characterized as an increase in globally averaged temperature, but the climate impacts experienced locally will be determined in part by the changes in atmospheric circulation that are induced by global warming. In particular, climate model simulations suggest that the westerly jet streams found at upper levels in the middle latitudes will shift towards the poles, so that the mean Northern Hemisphere jet stream will migrate northward, with a corresponding southward shift for its the Southern Hemisphere counterpart. These shifts are small but consequential, as patterns of rainfall and storminess in the middle latitudes are determined in large part by the positions of the jet streams. One issue to be considered is that the pattern of greenhouse warming generally includes a deep tropospheric warming maximum in the tropics together with surface trapped warming near the poles (referred to as polar amplification). The jet shifts can be regarded as a combined response to the tropical and polar influences, which are likely to have opposing effects and very different seasonalities. How this "jet-stream tug-of-war" between the tropics and the poles plays-out in different seasons will be the topic of this work. The picture on the right shows an image of the Northern Hemisphere jet-stream.

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The mixing of a stratospheric tracer (orange) and tropospheric tracer (blue)
by Rossby wave breaking. Figure made by Chengji Liu.

Title: Variability of Midlatitude Transport and Mixing In a Warmer World
Funding Body: National Science Foundation, AGS
Brief Description: Air quality over the western United States is determined not only by local emissions, but also by the transport of pollutants from outside the region, for example, by stratospheric intrusion events that bring naturally-occurring ozone-rich air to the surface. Quantifying the contribution of the large-scale atmospheric transport to present-day air quality is of vital importance for policy makers, since the ability of an area to be in compliance with current air quality standards is partly a function of the background meteorological conditions. Furthermore, increasing greenhouse gas concentrations over the next century are expected to drive large changes in the midlatitude circulation, but the effects of these changes on pollutant transport are not well understood. The two aims of the proposed research are (1) to gain a fundamental understanding of the dynamical mechanisms that couple synoptic variability and pollutant transport and (2) to explore how changes in synoptic variability with increased greenhouse gas concentrations may modify this transport. One way we are addressing these aims is to study how large-scale Rossby wave breaking mixes stratospheric and tropospheric air, as shown in the figure at the right.

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A smoke plume from the High Park Fire taken on June 9, 2012 south of Fort Collins.
Photo taken by CSU graduate student Steven Brey.

Title: Planning for an Unkown Future: Incorporating Meteorological Uncertainty into Predictions of the Impact of Fires and Dust on U.S. Particulate Matter
Funding Body: Environmental Protection Agency
Brief Description: Emissions of wildfire smoke and dust will likely increase over the western US with climate change. The focus of this work is to determine how model uncertainty in future meteorology translates into uncertainty in the contributions of smoke and dust to future particulate matter (PM) episodes. We will answer the following questions: 1) Do major synoptic events capture the variability in emissions and concentrations of PM from fires and dust over the western US? 2) What is the spread in future projections of air-quality-relevant synoptic conditions over the western US in state-of-the-art coupled atmosphere-ocean climate models? 3) How does this spread in future meteorology propagate to uncertainty in A) emissions of PM from fires and dust sources, and B) the resulting PM concentrations?

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Return period of very dangerous heat waves in 2076-2095 from the CMIP5 models.

Title: The Future of Very Dangerous Heat Waves and Community Health
Funding Body: CSU Office of the Vice President for Research
Brief Description: A small percent of all heat waves are catastrophic to human health, causing hundreds to thousands of excess deaths. Little is known about how the frequency of this type of very dangerous heat wave will change with climate change. Previous work applied an epidemiological model that predicts the frequency and mortality of very dangerous heat waves to a climate model to project their impacts into the future. While a major step forward, this study was limited to a single climate model, however, climate models differ substantially in their future projections of the meteorological conditions that can lead to heat waves, and thus, it is unknown how sensitive the findings are to the choice of model. Our work will apply this epidemiological model to projections from dozens of state-of-the-art climate models to determine the range of future projections of very dangerous heat waves and their impacts on mortality. This work will additionally consider the ability of the U.S. population to adapt to a changing climate in determining the future frequency of these extreme events. The figure on the right showns preliminary results of the return period of very dangerous heat waves at the end of the 21st Century assuming no adaptation of the communities to a changing climate.

Previous Research Projects

Title: Response of Tropospheric Transport and Stratosphere-Troposphere Exchange to Anthropogenic Climate Change
Funding Body: National Oceanic and Atmospheric Administration Climate Program Office, NOAA Climate and Global Change Postdoctoral Fellowship
Brief Description: The goal of this research is to describe and quantify the response of stratosphere-troposphere transport and midlatitude boundary-layer ventilation to future changes in climate. We propose to analyze reanalyses and coupled climate model output as well as design idealized model ex- periments to quantify changes in transport with increased greenhouse gases and to determine the relevant mechanisms at play.