AOS Faculty Profile
Large-Scale Atmospheric Dynamics and Climate Modeling
The goal of my research is to gain a better understanding of such basic aspects of the atmospheric circulation as the pole-to-equator temperature gradient, the climatic distribution of surface easterlies and westerlies, and the location and strength of the jet stream. In this work I use a hierarchy of models ranging from comprehensive and realistic numerical circulation models to very idealized dynamical systems that capture some aspects of the relevant physics. I also try to apply the understanding of fundamental lunderstanding gained from this kind of work to the global warming problem.
Examples of topics on which I have focused include: how best to think of the atmosphere as a whole as a “heat engine” and how best to understand the relatively low efficiency with which the atmosphere generates kinetic energy; how changes in the water vapor distribution in the atmosphere as climate warms produce a positive feedback on this warming; factors that control how the poleward energy transport is partitioned between the atmosphere and the ocean; the way in which large-scale mountain ranges and land-sea heating contrasts create the stationary waves, or deviations from longitudinal symmetry, that we see in the planetary-scale tropospheric wind field, the response of tropical cyclone activity to warming, and the distinctions between transient and equilibrium responses to perturbations in the Earth's energy balance.
Most recently, I have also begun working on idealized models of the organization of turbulent moist convection in the tropics with the aim of improving our understanding of the temperature, relative humidity, and cloud profiles in the tropics.
Some Recent Publications:
Held, Isaac M., and Ming Zhao, October 2011: The response of tropical cyclone statistics to an increase in CO2 with fixed sea surface temperatures. Journal of Climate, 24(20), DOI:10.1175/JCLI-D-11-00050.1.
Held, Isaac M., Michael Winton, K Takahashi, Thomas L Delworth, Fanrong Zeng, and Geoffrey K Vallis, May 2010: Probing the fast and slow components of global warming by returning abruptly to pre-industrial forcing. Journal of Climate, 23(9), 2418-2427.
Winton, Michael, K Takahashi, and Isaac M Held, May 2010: Importance of ocean heat uptake efficacy to transient climate change. Journal of Climate, 23(10), 2333-234
Zhao, Ming, Isaac M Held, Shian-Jiann Lin, and Gabriel A Vecchi, December 2009: Simulations of global hurricane climatology, interannual variability, and response to global warming using a 50km resolution GCM. Journal of Climate, 22(24), DOI:10.1175/2009JCLI3049.1.
Held, Isaac M., and Ming Zhao, June 2008: Horizontally homogeneous rotating radiative–convective Equilibria at GCM resolution. Journal of the Atmospheric Sciences, 65(6), DOI:10.1175/2007JAS2604.1.
Kang, S M., Isaac M Held, D M W Frierson, and Ming Zhao, 2008: The response of the ITCZ to extratropical thermal forcing: Idealized slab-ocean experiments with a GCM. Journal of Climate, 21(14), DOI:10.1175/2007JCLI2146.1.
Chen, G, and Isaac M Held, 2007: Phase speed spectra and the recent poleward shift of Southern Hemisphere surface westerlies. Geophysical Research Letters, 34, L21805, DOI:10.1029/2007GL031200.