Midlatitude Storm Track Dynamics on a Cloudy Earth

California Institute Of Technology, Pasadena CA

Investigators

Abstract

Large-scale wind storms in the extratropics occur preferentially in regions known as storm tracks. In the Northern Hemisphere, storm tracks span the North Pacific and North Atlantic, and the storms in them shape the regional weather, for example, in the Pacific Northwest, the eastern United States, and Europe. Because storm tracks are the principal conduit through which energy and moisture are transported in the climate system, they are also crucially important for controlling climatic features such as the global distributions of rainfall and surface temperature. Recent observations and simulations with numerical atmosphere models have revealed that climate changes modulate various aspects of storm tracks. For example, storm tracks generally shift poleward as the climate warms and equatorward as the climate cools. However, fundamental questions about the structure and variability of storm tracks and their response to climate changes remain unanswered. For example, it is unclear what controls where storm tracks terminate over the North Pacific and North Atlantic, what their observed low-frequency variations depend on, and how these and other aspects respond to climate changes. Answering such questions requires an improved understanding of how storm tracks interact with stationary weather patterns, such as the Aleutian Low, and how they interact with clouds which on one hand are products of storms and on the other hand modify, through their absorption/reflections/emission, the environments where storm tracks operate. This project aims to answer such questions, using observational data and targeted experiments with idealized atmosphere models that serve as a computational laboratory. The project will examine the processes responsible for controlling storm tracks by analyzing observations and simulations with an atmosphere model that is simplified in some respects (e.g., it may simplify or eliminate continental effects altogether) but contains relatively sophisticated representations of clouds. The goal is study the fundamental processes controlling the structure and variability of storm tracks and their interactions clouds, culminating in theories and conceptual models of storm track dynamics. This research will bridge the gap between state-of-the-art comprehensive climate models and fundamental physical understanding. The conceptual models to be developed under this project will provide a framework for assessing weather forecasting and climate models and will suggest ways for improving them. The project will assess and potentially enhance predictability of major weather hazards in mid-latitudes, including extreme storms, droughts, and floods, on sub-seasonal and longer timescales. It will also train a new generation of scientists who are fluent in the use of the full breadth of state-of-the-art tools in atmosphere and climate dynamics, from theory to comprehensive numerical models. This will be achieved by directly funding a postdoctoral scholar, who, by the end of this project, will be ready to commence her independent career in climate and large-scale dynamics; by partially funding a graduate student at the start of his or her research career; and by disseminating results through publications, conference presentations, colloquia, and classroom teaching. The research project will also broaden the range of available research tools by making the program code of models used and developed in this research publicly available. 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.