Professor of Engineering,
Columbia University, USA
Global to Local Hydroclimatic Networks – Dynamics and Predictability
Water makes the world go around. The centrality of the global hydrologic cycle to climate dynamics is self-evident. Yet, temperature as the quasi-equilibrium state of a slowly changing planet emerged as the canary in the mine, and continues to be the focal point of the politico-scientific climate discussion. Hydrologists, perhaps because of their primary focus on terrestrial processes, have failed to rise as the voice of scientific inspiration for understanding planetary climate dynamics through the lens of the hydrologic cycle. Rather, they have unwittingly become consumers of climate change projections, and research in the field is dominated by work on the propagation of these projections through the terrestrial hydrologic cycle. The retrospective analysis of the climate models applied to the 20th century is impressive primarily in the magnitude of the biases in precipitation at regional to local scales relative to observations. It is also impressive in the failure to capture the seasonal to inter-annual to decadal dynamics of atmospheric water vapor transport and precipitation that ultimately determine persistent as well as episodic hydrologic extremes and ecological, pedological, agricultural and economic futures. "Bias correction" of precipitation statistics by hydrologists is a nonsensical and purely operational reaction to this situation, a denigration of basic scientific principles, and with unknown utility for the extrapolation exercises the users engage in. "Fixing" precipitation inputs in this way still does not address the gross errors in temporal dynamics and regimes that the climate models demonstrate that are then carried through into the hydrological predictions.
This talk will strive to introduce the much less popular world of research, in which diagnostic analyses of climate dynamics reveal incredible structure and predictability for global to regional to local aspects of the hydrologic cycle - emergent regime like phenomena in planetary spatio-temporal ocean-atmosphere interactions that lead to dynamic networks of organized moisture transport and precipitation, that then impart spatio-temporal structure to flows on terrestrial drainage networks. These have potential predictability at operational and planning time scales. I will stress the importance of empirical diagnostic and predictive modeling for understanding the nature of the system, for providing benchmarks that newtonian or hybrid statistical-dynamical models of the underlying physics need to consider as performance metrics, and for applications in risk management of water resource systems.
Dr. Upmanu Lall is the Director of the Columbia Water Center and the Alan and Carol Silberstein Professor of Engineering. He has broad interests in hydrology, climate dynamics, water resource systems analysis, risk management and sustainability. He is motivated by challenging questions at the intersection of these fields, especially where they have relevance to societal outcomes or to the advancement of science towards innovative application.
Distinguished Lecture Series 2021
This lecture is part of the GIWS Distinguished Lecture Series 2021. Click below for more information on the series, including a full schedule and an archive of previous years.
- 10:00 AM - 11:00 AM CST