My research interests include retrieving polar trace gas concentrations and cloud properties using measurements of downwelling infrared radiation.
The Polar ENgagement through GUided INquiry (PENGUIN) project brings real-world data into the classroom through computational modules in Python, Excel, and R.
Measuring black carbon in the Chilean Andes, Antarctica, and U.S. mountains helps understand how it increases snowmelt and loss of glaciers.
Polar Research: Clouds and trace gases
I study the greenhouse effects of clouds and trace gases in the Arctic and Antarctic to understand their contributions to the energy budget.
My graduate work involved infrared spectroscopy of water vapor, especially absorption between strong lines, or the water vapor continuum. This work was done as part of the South Pole Atmospheric Radiation and Cloud Lidar Experiment (SPARCLE) in 2000-2001 with Profs. Steve Warren and Von Walden.
This work also included retrievals of temperature and water vapor from downwelling infrared radiance spectra, which is an ongoing interest.
Recent work involves improving radiative transfer calculations of supercooled liquid cloud absorption and emission of infrared radiation. This improvement relies on incorporating the temperature dependence of the complex refractive indices of supercooled water.
My work also includes retrieving cloud properties from infrared radiation. I have investigated algorithms (such as optimal estimation) for retrieving cloud properties, including instrumental considerations such as calibration and instrument responsivity, sources of error such as biases, noise and error in knowledge of the atmospheric state, and limited spectral resolution. Microphysical cloud properties include optical depth, thermodynamic phase, and effective radius. I’m also interested in improving algorithms for cloud base-height retrieval.
My work also seeks to improve our understanding of the atmosphere over the Antarctic Peninsula and Southern Ocean, using measurements made at Escudero Station, as part of the Antarctic Research Group of the University of Santiago of Chile.
Black carbon is an anthropogenic pollutant that decreases the albedo of ice and snow. In the Chilean Andes, black carbon on glaciers enhances the melt rate. Because glaciers are an important source of drinking water in Chile, glacier loss is a topic of major concern. I participated in field expeditions (led by Steven Neshyba, in collaboration with Steve Warren of the University of Washington and Raul Cordero of the University of Santiago of Chile) to sample black carbon on snow in the Chilean Andes in July 2015 and 2016. Our group at the University of Santiago of Chile continues to measure black carbon in the Chilean Andes, as well as in Antarctica.
During the summer of 2020, we expanded our black carbon measurements to include locations in Colorado and on Mt. Rainier, in Washington, as part of a virtual summer Research Experience for Undergraduates (REU) program. Two students sampled snow, while two additional students measured the impurity concentrations using the Light Absorbing Measurement (LAM) developed by Prof. Carl Schmitt.
Roughening on ice crystal surfaces
Advances in scanning electron microscopy (SEM) have made it possible to monitor the growth and ablation of ice crystals on the surfaces of ice crystals at resolutions not previously possible. In collaboration with Steven Neshyba, our work has revealed horizontal corrugations, or “trans-prismatic strands”, visible on SEM images of ice taken at the University of Puget Sound in collaboration with Steven Neshyba. We also examine consequences of the roughening for light-scattering properties affecting radiative flux and remote sensing.
Molecular dynamics at the ice-vapor interface
Other research includes studying surface roughness on ice crystals through SEM images and molecular dynamics, and using molecular dynamics to explore a possible role for RNA on ice in the origins of life on Earth.