Exploring Radiation's Spectral Dimension

The flow of electromagnetic energy through the atmosphere and its interaction with Earth's surface underly an enormous range of weather and climate phenomena. Fluxes of radiation almost entirely determine Earth's temperature, act as a strong constraint on global precipitation and the height of the tropopause, and shape atmospheric motions from the global scale to the cloud scale. The laws of physics for electromagnetic radiation are very well known, particularly for the visible and infrared radiation relevant to Earth, but the application of these laws to the Earth's atmosphere and surface requires complex and intensive calculations, thus the field has relied heavily on computer simulations which are not easy to understand. The last eight years, however, have seen a resurgence of efforts to use the laws of physics in simplified form to build understanding of the influence of radiation on atmospheric phenomena. These advances in understanding have been achieved by embracing the spectral variation, or wavelength dependence, of the flow of radiation through the atmosphere: the world is not black-and-white, nor even grey, but shaped by radiation in all the colors of the rainbow and beyond. In addition to its contributions to the basic science of radiative transfer the project will enrich the workforce by providing support and training to a postdoc or PhD student. This project seeks to build on these recent insights to develop theories and conceptual models in two distinct areas. One set of questions will focus on problems in atmospheric physics: why does the stratosphere cool when carbon dioxide concentrations are increased but warm slightly when the concentration of water vapor increases? How do the tight links between temperature and water vapor mediate the impact of clouds on the radiation leaving the atmosphere at the upper or lower boundaries? How can insights obtained by dramatically simplifying the spectral opacity of greenhouse gases be applied to the absorption of solar radiation? The second set of questions will concern how radiation sculpts atmospheric circulations at all scales by developing a richer hierarchy of simplifications for radiation for dynamical models. The spectroscopy of gases will be replaced by few-parameter idealizations; clouds will be spectrally-uniform and scatter solar radiation in simplified ways; radiative transfer itself may be approximated by focusing on the dominant terms in the relevant equations. These idealized treatments of radiation will be coupled to dynamical models of the atmosphere and used to explore the essential elements of radiation-circulation coupling in a range of increasing complex circumstances. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2536164 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Robert Pincus | Institution: Columbia University, NEW YORK, NY | Award Amount: $823,336 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2536164 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2536164.html