Chaim I. Garfinkel



  • Garfinkel, C.I., A. Gordon, L. Oman, F. Li, S. Davis, and S. Pawson, Nonlinear response of tropical lower stratospheric temperature and water vapor to ENSO, ACPD
  • Garfinkel, C.I. and C. Schwartz, MJO-related tropical convection anomalies lead to more accurate stratospheric vortex variability in subseasonal forecast models, GRL

  • Paldor N., , I. Fouxon, O. Shamir, and C.I. Garfinkel, Yanai waves on the rotating spherical Earth, J. Atm. Sci

Accepted/In press



    • Shaw, T. A., M. Baldwin, E. A. Barnes, R. Caballero, C. I. Garfinkel, Y-T. Hwang, C. Li, P. A. O'Gorman, G. Riviere, I R. Simpson, and A. Voigt, 2016: Understanding storm tracks and their response to climate change , Nature Geosc, 9, 656-664, doi:10.1038/ngeo2783.

    • Harnik N., C.I. Garfinkel, and O. Lachmy, The Influence of Jet Regimes on Extreme Weather events, In 'Dynamics and Predictability of Large-Scale, High-Impact Weather and Climate Events'. Ed. Li, J., R. Swinbank, H. Volkert and R. Grotjahn. Cambridge University Press.




    • Hurwitz, M.M., C.I. Garfinkel, P.A. Newman, and L.D. Oman (2013), Sensitivity of the atmospheric response to Warm Pool El Nino events to modeled SSTs and future climate forcings**. Journal of Geophysical Research: Atmospheres. 118(24), 13,371--13,382, DOI: 10.1002/2013JD021051.

      summary = {The late 21st century extratropical atmospheric response to WPEN events is investigated using GEOSCCM. GEOSCCM simulations are forced by projected late 21st century concentrations of greenhouse gases (GHGs) and ozone-depleting substances (ODSs) and by SSTs and sea ice concentrations from an existing ocean-atmosphere simulation. The future Arctic vortex response to ENSO is qualitatively similar to that observed in recent decades but is weaker in late winter. This response reflects the weaker SST forcing in the Niño 3.4 region and subsequently weaker Northern Hemisphere tropospheric teleconnections. The Antarctic stratosphere does not respond to WPEN events in a future climate, reflecting a change in tropospheric teleconnections: The meridional wavetrain weakens while a more zonal wavetrain originates near Australia. Sensitivity simulations show that a strong poleward wavetrain response to WPEN requires a strengthening and southeastward extension of the South Pacific Convergence Zone; this feature is not captured by the late 21st century modeled SSTs. Expected future increases in GHGs and decreases in ODSs do not affect the polar stratospheric responses to WPEN.}

    • Garfinkel, C. I., M. M. Hurwitz, L. D. Oman, D. W. Waugh (2013), Contrasting Effects of Central Pacific and Eastern Pacific El Nino on Stratospheric Water Vapor**, GRL, 40, 4115--4120, doi: 10.1002/grl.50677

      summary = {Modeling experiments are used to demonstrate that seasonality and the location of the peak warming of sea surface temperatures dictate the response of stratospheric water vapor to El Niño. Specifically, El Niño leads to a moistening of the stratosphere (1) only in the spring following the events peak, and (2) only for eastern Pacific type events. However, in fall and in early winter, and also during El Niño events in which the sea surface temperature anomaly is found mainly in the central Pacific, the response is qualitatively different: temperature changes in the warm pool region and specifically over the cold point region are nonuniform, and less water vapor enters the stratosphere.}

    • Garfinkel, C.I., D. W. Waugh, L.D. Oman, L. Wang, and M.M. Hurwitz, (2013). Temperature trends in the tropical upper troposphere and lower stratosphere: connections with sea surface temperatures and implications for water vapor and ozone**, Journal of Geophysical Research: Atmospheres, 118(17), 9658-9672, doi: 10.1002/jgrd.50772. Highlighted in this News and Views in Nature Climate Change

      summary = {Satellite observations and chemistry-climate model experiments are used to demonstrate that the zonal structure of tropical lower stratospheric tem- perature, water vapor, and ozone trends has been heavily influence by the SST trend. The zonal variations are stronger than the zonal- mean response in boreal winter. Warming SSTs in the Indian Ocean and in the warm pool region have led to enhanced moist heating in the upper tro- posphere, and in turn to a Gill-like response that extends into the lower stratosphere. The anomalous circulation has led to zonal structure in the ozone and water vapor trends near the tropopause, and subsequently to less water vapor entering the stratosphere. Projected future SSTs appear to drive a temperature and water vapor response whose zonal structure is similar to the historical response.}

    • Garfinkel, C. I., L. D. Oman, E. A. Barnes, D. W. Waugh, M. M. Hurwitz, A. M. Molod (2013), Connections between the Spring Breakup of the Southern Hemisphere Polar Vortex, Stationary Waves, and Air-Sea Roughness*, J. Atmos. Sci., 70, 2137--2151. doi:

      summary = {An updated air-sea roughness parameterization in GEOSCCM leads to a decrease in model biases in Southern Hemispheric ozone, polar cap temperature, stationary wave heat flux, and springtime vortex breakup. A dynamical mechanism is proposed whereby an improved parametrization of drag at the air-sea interface leads to improved stationary waves. Increased surface friction leads to anomalous eddy momentum flux convergence primarily in the Indian Ocean sector (where eddies are strongest climatologically) in September and October. The localization of the eddy momentum flux convergence anomaly in the Indian Ocean sector leads to a zonally asymmetric reduction in zonal wind and, by geostrophy, to a wavenumber-1 stationary wave pattern. This tropospheric stationary wave pattern leads to enhanced heat flux entering the stratosphere. The net effect is an improved Southern Hemisphere vortex: the vortex breaks up earlier in spring (i.e., the spring late-breakup bias is partially ameliorated) yet is no weaker in mid-winter. As many other chemistry-climate models use a similar scheme for their surface layer momentum drag and have similar biases in the stratosphere, we expect that results from GEOSCCM may be relevant for other climate models.}

    • Garfinkel, C. I., D. W. Waugh, E. P. Gerber (2013), The Effect of Tropospheric Jet Latitude on Coupling between the Stratospheric Polar Vortex and the Troposphere*, J. Clim., 26, 2077-2095, doi: 10.1175/JCLI-D-12-00301.1.

      summary = {The tropospheric response to an identical stratospheric vortex configuration is shown to be strongest for a jet centered near 40S and weaker for jets near either 30S or 50S by more than a factor of three. Stratosphere-focused mechanisms based on eddy phase speed, eddy heat flux, stratospheric potential vorticity inversion, planetary wave reflection, and zonal length scale, appear to be incapable of explaining the differences in the magnitude of the jet shift. In contrast, arguments based purely on tropospheric dynamics involving the strength of eddy-zonal mean flow feedbacks and jet persistence, and related changes in the synoptic eddy momentum flux, appear to explain this effect. The dependence of coupling between the stratospheric polar vortex and the troposphere on tropospheric jet latitude is generally consistent with the variability and trends in jets in the North Atlantic, North Pacific, and Southern Hemisphere in observations and comprehensive models. }

    • Garfinkel, C. I., M. M. Hurwitz, D. W. Waugh, A.H. Butler (2013), Are the Teleconnections of Central Pacific and Eastern Pacific El Nino Distinct in Boreal Wintertime?^, Climate Dynamics, doi:10.1007/s00382-012-1570-2.

      summary={ In reanalysis data, the sign of the North Pacific and stratospheric response to Central Pacific El Ni{\~n}o is sensitive to the composite size, the specific Central Pacific El Ni{\~n}o index used, and the month or seasonal average that is examined, highlighting the limitations of the short observational record. Long model integrations suggest that the response to the two types of El Ni{\~n}o are similar in both the extratropical troposphere and stratosphere. Namely, both Central Pacific and Eastern Pacific El Ni{\~n}o lead to a deepened North Pacific low and a weakened polar vortex, and the effects are stronger in late winter than in early winter. However, the long experiments do indicate some differences between the two types of El Ni{\~n}o events regarding the latitude of the North Pacific trough, the early winter polar stratospheric response, surface temperature and precipitation over North America, and globally averaged surface temperature. These differences are generally consistent with, though smaller than, those noted in previous studies. }


    • Hurwitz, M.M., P.A. Newman, and C.I. Garfinkel (2012), On the Influence of North Pacific Sea Surface Temperatures on the Arctic Winter Climate**, J. Geophys. Res. Atmos., 117, D19110, doi:10.1029/2012JD017819.

      summary={Modeling experiments are used to isolate the impact of North Pacific SST anomalies on the vortex. SST anomalies equatorward of 20N are set equal to zero, and thus any influence of ENSO has been removed. Cold SSTs lead to a deepened North Pacific low in the troposphere, which then leads to enhanced upward wave propagation and subsequently a weakened vortex. In addition, more SSW occur during the cold SST experiment. Finally, cold SSTs lead to a negative NAO. }

    • Garfinkel, C. I., A.H. Butler, D. W. Waugh, M. M. Hurwitz, L. M. Polvani (2012), Why might stratospheric sudden warmings occur with similar frequency in El Nino and La Nina winters?**, J. Geophys. Res. Atmos., 117, D19106, doi:10.1029/2012JD017777.

      summary={ The region in the North Pacific most strongly associated with precursors of SSW is not strongly influenced by El Nino and La Nina teleconnections. In the observational record, both La Nina and El Nino lead to similar anomalies in this region and, consistent with this, there is a similar SSW frequency in La Nina and El Nino winters. A similar correspondence between the penetration of ENSO teleconnections into the SSW precursor region and SSW frequency is found in the comprehensive chemistry-climate models. The inability of some of the models to capture the observed relationship between La Nina and SSW frequency appears related to whether the modeled ENSO teleconnections result in extreme anomalies in the region most closely associated with SSW. In contrast, the seasonal mean polar vortex response to ENSO is only weakly related to the relative frequency of SSW during El Nino and La Nina. }

    • Garfinkel C. I., S. B. Feldstein, D. W. Waugh, C. Yoo, S. Lee (2012), Observed Connection between Stratospheric Sudden Warmings and the Madden-Julian Oscillation**, GRL, 39,

      summary={ The MJO influences the tropospheric North Pacific, and in particular the region in the North Pacific most strongly associated with SSWs. Consistent with this, SSWs in the reanalysis record have tended to follow certain MJO phases. The magnitude of the influence of the MJO on the vortex is comparable to that associated with the Quasi-Biennial Oscillation and El Nino. The subsequent weak vortex anomaly propagates down to the troposphere.}

    • Barnes, E. A. and Garfinkel, C. I. (2012), Barotropic impacts of surface friction on eddy kinetic energy and momentum fluxes: an alternative to the barotropic governor*, JAS, 69, doi: 10.1175/JAS-D-11-0243.1.

      summary = { In the model runs from Garfinkel, Molod, Oman, and Son 2011, upper-level zonal winds decrease and eddy- momentum-flux convergence into the jet core increases. Globally-averaged eddy kinetic energy decreases, however, inconsistent with the conventional barotropic governor mechanism whereby increased barotropic shears inhibit baroclinic wave growth. The non-divergent barotropic model on the sphere is used to demonstrate an additional mechanism for the effect of surface drag on eddy momentum fluxes and eddy kinetic energy. Analysis of the pseudomomentum budget shows that increased drag modifies the background meridional vorticity gradient, which allows for enhanced eddy momentum flux convergence in the presence of a constant eddy source. This new mechanism can explain the GEOS finding.}

    • Garfinkel, C.I., T.A. Shaw, D.L. Hartmann, and D.W. Waugh (2012), Does the Holton-Tan Mechanism Explain How the Quasi-Biennial Oscillation Modulates the Arctic Polar Vortex?*, J. Atmos. Sci., 69, doi:10.1175/JAS-D-11-0209.1.

      summary = { The Holton Tan mechanism involving subtropical critical lines does not explain how the QBO modulates the vortex. Rather, the axisymmetric circulation of the QBO required to maintain thermal wind balance influences subpolar Rossby wave propagation and thus leads to a weakened vortex. Linear theory can explain this effect. changes. The effect in the polar stratosphere is driven largely by wavenumber 1, while higher (including synoptic) wavenumbers are influenced by the QBO in the subtropical lower stratosphere. Downward propagation of the QBO in the equatorial stratosphere, upper stratospheric equatorial zonal wind, and changes in the tropospheric circulation, appear to be less important than lower stratospheric easterlies for the polar stratospheric response.}


    • Hurwitz, M. M., Newman, P. A., and Garfinkel, C. I. (2011), The Arctic vortex in March 2011: a dynamical perspective, Atmos. Chem. Phys., 11, 11447-11453, doi:10.5194/acp-11-11447-2011.

      summary = { Record Arctic Ozone loss was observed in March 2011. Unusually low wave driving of the vortex preceded the unusually cold temperatures and low ozone. While ENSO and the QBO likely did not contribute to this event, SSTs in the North Pacific may have.}

    • Garfinkel, C.I., A. M. Molod , L.D. Oman , I-S. Song (2011), Improvement of the GEOS-5 AGCM upon updating the Air-Sea Roughness Parameterization**, GRL, 38, L18702, doi:10.1029/2011GL048802.

      summary = { Updating the air-sea roughness parameterization over the ocean so that it more closely matches recent observations of air-sea exchange improves the GEOS-5 atmospheric general circulation model. Many other GCMs use a similar class of parameterization for their air-sea roughness scheme. We therefore expect that results from GEOS-5 are relevant to other models as well.}

    • Garfinkel, C.I. and D.L. Hartmann (2011), The Influence of the Quasi-Biennial Oscillation on the Troposphere in Wintertime in a Hierarchy of Models, Part 2-Perpetual Winter WACCM runs, J. Atmos. Sci., 68, doi: 10.1175/2011JAS3702.1.

      summary = {Even in the presence of tropical convection anomalies and a variable polar vortex, the QBO influences the troposphere directly through extratropical eddies. The response to the QBO is greatest in the North Pacific, but is present in other regions with eddy driven variability. Response is stronger in February than in January. Response is consistent with the reanalysis data and a coupled WACCM run. }

    • Garfinkel, Chaim I., Dennis L. Hartmann (2011), The Influence of the Quasi-Biennial Oscillation on the Troposphere in Winter in a Hierarchy of Models. Part I: Simplified Dry GCMs. J. Atmos. Sci., 68, 1273--1289, doi: 10.1175/2011JAS3665.1.

      summary = {The QBO can influence the troposphere even in the absence of tropical convection anomalies and a variable polar vortex. QBO anomalies require a meridional circulation to establish thermal wind balance. This circulation extends downwards into the troposphere and induces zonal wind anomalies in the subtropical troposphere. In the presence of extratropical eddies, the zonal wind anomalies are intensified and extend downward to the surface. The tropospheric response differs qualitatively between a strong subtropical jet and a weaker jet, contrary to the predictions of the fluctuation-dissipation theorem. If the extratropical circulation is zonally asymmetric, the response to the QBO is greatest in the exit region of the subtropical jet. Response in dry model is consitent with the reanalysis data and a coupled WACCM run. }


    • Garfinkel, C.I. and D.L. Hartmann (2010), The Influence of the Quasi-Biennial Oscillation on the North Pacific and El-Nino teleconnections, J. Geophys. Res. Atmos , 115, D20116,doi:10.1029/2010JD014181.

      summary = {EQBO at 70hPa leads to a weaker teleconnection in the North Pacific than WQBO in both a model and reanalysis. Part of this may be due to a direct affect of the QBO on the North Pacific, which does not resemble the vortex response in the North Pacific. Part of it may be due to an indirect mechanism by which wind anomalies associated with the EQBO lead to less supportive conditions for the growth of a North Pacific low. Sampling variability and variability in convection cannot be excluded as contributors, however. }

    • Garfinkel, C.I., D.L. Hartmann, and F. Sassi (2010), Tropospheric Precursors of Anomalous Northern Hemisphere Stratospheric Polar Vortices, J. Clim., 23, doi: 10.1175/2010JCLI3010.1.

      summary = {Simple reasoning is used to explain the nature of regional tropospheric variability that affects the vortex. An anomalous low over the North Pacific and an anomalous high over Eastern Europe weaken the vortex nearly immediately, with the effect propagating downwards with time. Perturbations of the vortex due to the two centers add linearly; the two are temporally uncorrelated with each other and with the QBO; the two centers are relevant in both early winter and late winter. Much of the influence of ENSO and October Eurasian snow on the vortex is associated with these two centers. Some 40\% of vortex variance is related to variability of these two and the QBO. }


    Other Items

    • My Ph.D. dissertation: Stratosphere-Troposphere Coupled Variability in the Wintertime Northern Hemisphere.

    • SPARC newsletter number 43 - July 2014, Report on the 5th SPARC General Assembly, 12-17 January 2014, Queenstown, New Zealand

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