Mechanisms - global circulation variabil

Mechanisms driving the variability of the global circulation

Our studies focus on the large scale circulation patterns and variability that arise from a range of interactions within this system, at varying degrees of complexity. A general theme of research is to obtain a mechanistic "building-block" understanding of multi-scale interactions.

For example, the simplest model of the global tropospheric circulation involves the nonlinear coupling of three main components - the mean overturning circulation, the jet streams, and mid-latitude synoptic scale waves. The global circulation results from a balance of these components with external forcing and damping, giving rise to dynamical regimes (Lachmy and Harnik, 2014, 2016, 2020). Other studies have taken into account other processes, including planetary scale Rossby waves driven by stationary forcings, medium scale Rossby waves, arising spontaneously and propagating along the upper tropospheric jet-stream wave guides, tropical dynamics, and the effects of diabatic heating and moisture.

For more information on our studies on dynamical jet regimes see here.

Select publications:

Submitted/in preparation:

T. Tamarin-Brodsky and N. Harnik, “The three-way feedback between North-Atlantic circulation regimes, Rossby wave breaking, and surface weather” (in preparation)

Sandler D., H. Saaroni, B. Ziv, T. Tamarin-Brodsky, and N. Harnik, 2024: The Impacts of Wintertime North Atlantic Storm Track Regimes on Cyclonic Activity Downstream: An Extreme Test Case over the Eastern Mediterranean. Submitted to Weather Clim. Dynam.

White, I. P., O. Lachmy, and N. Harnik, 2024: Influence of diabatic heating on the maintenance of the midlatitude jet. In revision for Q J R Meteorol Soc.

Thakur, ABS, J. Sukhatme, and N. Harnik. 2024: Investigating the role of tropical and extra-tropical waves in the Hadley circulation via present-day Earth-like to globally uniform SST forcing. Revision under review, Q J R Meteorol Soc.

Published:

T. Tamarin-Brodsky and N. Harnik, 2024: The relation between Rossby Wave Breaking events and low-level weather systems, Weather Clim. Dynam. 5, 87–108.

Schröttle, J., Suhas, D., Harnik, N. and Sukhatme, J. (2022), Turbulence and equatorial waves in moist and dry shallow-water flow, excited through mesoscale stochastic forcing. Q J R Meteorol Soc. 148, 599–619.

Messori, G., Harnik, N., Madonna, E., Lachmy, O., and Faranda, D., 2021: A dynamical systems characterization of atmospheric jet regimes, Earth Syst. Dynam., 12, 233–251

Lachmy, O, and Harnik, N. 2020: Tropospheric jet variability in different flow regimes. Quart. J. Roy. Meteor. Soc., 146, 327– 347.

Lachmy O. and N. Harnik, 2016: Wave and jet maintenance in different flow regimes. J. Atmos. Sci., 73 2465-2484.

Lachmy O. and N. Harnik, 2014: The Transition to a Subtropical Jet Regime and its Maintenance. J. Atmos. Sci., 71, 1389-1409

Harnik, N., E. Galanti, O. Martius, and O. Adam, 2014. The anomalous merging of the African and North Atlantic jet streams during Northern Hemisphere winter of 2010. J. Clim. 27, 7319–7334.

Harnik N, R. Seager, N. Naik, M. Cane, and M. Ting, 2010. The role of linear wave refraction in the transient eddy-mean flow response to tropical Pacific SST anomalies. Quart. J. Roy. Meteor. Soc., 136: 2132–2146. doi: 10.1002/qj.688

Seager R., N. Naik, M. Ting, M. A. Cane, N. Harnik and Y. Kushnir, 2010: Adjustment of the atmospheric circulation to tropical Pacific SST anomalies: Variability of transient eddy propagation in the Pacific-North America sector. Quart. J. Roy. Meteor. Soc. 136, 277-296.

Seager, R., N. Harnik, Y. Kushnir, M. Ting, H.-P. Huang, and J. Velez, 2005. Mechanisms of ENSO-forcing of hemispherically symmetric precipitation variability. Quart. J. Roy. Meteor. Soc. 131 1501-1528

Harnik, N., and E. K. M. Chang, 2004: The effects of variations in jet width on the growth of baroclinic waves: Implications for midwinter Pacific stormtrack variability. JAS 61, 23-40

Seager, R., N. Harnik, Y. Kushnir, W. Robinson, and J. Miller, 2003: Mechanisms of hemispherically symmetric climate variability. J. Clim 16,2960-2978.

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