Home Page 

Dr. Orli Lachmy, Lecturer

Contact Info

The Open University of Israel Department of Natural Sciences 1 University Road, P. O. Box 808, Raanana 43107, Israel
Office:(+972) 9-7782128 Email:orlila@openu.ac.il

Areas Of Interest
  • Atmosphere dynamics
  • Climate variability
  • Geophysical fluid dynamics
  • Midlatitude jet streams and storm tracks

I am a lecturer for Earth Sciences at the Department of Natural Sciences in the Open University of Israel. I study the dynamics of the atmospheric general circulation and its role in the climate system.

I am fascinated by the atmospheric flow, which obeys simple physical rules, yet exhibits complex nonlinear behavior that is very difficult to predict. Using numerical modeling and observational analysis we are able to advance the theoretical understanding of the atmospheric general circulation dynamics and its role in the transport of energy, heat, moisture and momentum around the globe.

My research focuses on the dynamics of the midlatitude jet stream and storm tracks, which control climate and weather patterns in the midlatitudes (between 30 and 60 degrees latitude) as well as the transport of heat and moisture from the tropics to polar regions. The structure and intensity of the jet stream and storm track are expected to change in response to climate change, affecting the local patterns of precipitation and weather variability, yet there is no robust theoretical understanding of this response. My work aims at improving the theoretical understanding of this dynamical system, as part of the communal effort for improving the reliability of climate predictions.

2017 - present
Lecturer at the Department of Natural Sciences, The Open University of Israel.
2015 - 2017
Postdoctoral researcher under the guidance of Prof. Tiffany Shaw at the Department of Geophysical Sciences, University of Chicago.
2015
Ph.D. Atmospheric Sciences
Tel Aviv University, Tel Aviv, Israel
Topic: “Atmospheric extratropical wave-mean flow interactions
maintaining the different flow regimes of the jet stream”
Advisor: Prof. Nili Harnik
2008
M.Sc. Atmospheric Sciences
Tel Aviv University, Tel Aviv, Israel
Topic: “A wave amplitude transition in a quasi-geostrophic wavemean
flow interaction system”
Advisor: Prof. Nili Harnik
2004
B.Sc. Physics
The Hebrew University, Jerusalem, Israel

2018 Israel Science Foundation, new faculty equipment grant. Title: "High performance computer for general circulation models".

2018​  Israel Science Foundation , individual research grant. Title: " The role of midlatitude latent heating in the maintenance of the extratropical atmospheric circulation and its response to climate change".

2012 Scholarship for promoting women in science from the Israel Ministry of Science and Technology.

2009 President and rector scholarship for excellent doctoral students, Tel Aviv University.​

2008 Graduation of M.Sc. with special distinction, Tel Aviv University.​

2006 Scholarship for excellent research students, Tel Aviv University.​

Lachmy, O. and Y. Kaspi (2020), The role of diabatic heating in Ferrel cell dynamics, submitted to Geophysical Research Letters.

Messori, G., N. Harnik, E. Madonna, O. Lachmy and D. Faranda, A dynamical systems characterisation of atmospheric jet regimes, under revision in Earth System Dynamics, https://doi.org/10.5194/esd-2020-8​.

Afargan-Gerstman, H., O. Lachmy and Y. Kaspi, The storm track response to subtropical jet strengthening in an idealized GCM with a seasonal cycle, under revision in Journal of the Atmospheric Sciences.

Lachmy, O. and N. Harnik (2020), Tropospheric jet variability in different flow regimes, Quarterly Journal of the Royal Meteorological Society, Vol. 146, 327-347. doi.org/10.1002/qj.3678

Tan Z., O. Lachmy and T. A. Shaw (2019), The sensitivity of the jet stream response to climate change to radiative assumptions , Journal of Advances in Modeling Earth Systems, Vol. 11, 934-956. ​ 

Lachmy, O. and T. A. Shaw (2018), Connecting the energy and momentum flux response to climate change using the Eliassen and Palm relation, Journal of Climate, Vol. 31, 7401-7416.

Lachmy, O. and N. Harnik (2016), Wave and jet maintenance in different flow regimes, Journal of the Atmospheric Sciences, Vol. 73, 2465-2484.

Harnik, N., C. Garfinkel and O. Lachmy (2016), The influence of jet regimes on extreme weather events, in Dynamics and Predictability of Large-Scale, High-Impact Weather and Climate Events 2, 79. Edited by J. Li, R. Swinbank, H. Volkert and R. Grotjahn, Cambridge University Press.

Lachmy, O. and N. Harnik (2014), The transition to a subtropical jet regime and its maintenance, Journal of the Atmospheric Sciences, Vol. 71, 1389-1409.

Lachmy, O. and N. Harnik (2009), A wave amplitude transition in a quasi-linear model with radiative forcing and surface drag, Journal of the Atmospheric Sciences, Vol. 66, 3479-3490.

​Lachmy O. and N. Harnik (2019), The role of planetary waves in determining the properties of the annular mode, In AGU fall meeting 2019, AGU.

Lachmy O. and N. Harnik (2018), A transition between a quasi-linear and nonlinear regime of the tropospheric jet stream, In EGU General Assembly Conference Abstracts, Vol. 20, p. 3222.

Harnik N., G. Messori, D. Farnada and O. Lachmy (2018), Characterizing the dynamical regimes of the global atmospheric circulation using local persistence measures, In EGU General Assembly Conference Abstracts, Vol. 20, p.14786. 

Harnik, N., and O. Lachmy (2016), Maintenance, internal variability, and dynamical regimes of an idealized global atmospheric circulation, In EGU General Assembly Conference Abstracts, Vol. 18, p. 6895.

Lachmy, O., T. Shaw and Z. Tan (2018), ​Connecting the energy budget response to climate change and the midlatitude jet shift, May 2018, Earth Science Institute, The Hebrew University, Jerusalem, Israel.

Lachmy, O., T. Shaw and Z. Tan (2018), Understanding the response of the atmospheric circulation to climate change from an energetic perspective, April  2018, Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, Israel.

Lachmy, O. and N. Harnik (2016), Flow regimes of the atmospheric jet stream and their maintenance, November 2016, Department of Meteorology, the Pennsylvania State University, PA, USA.

Lachmy, O. and N. Harnik (2014), The maintenance of the subtropical and eddy-driven jets, March 2014, Earth Science Institute, The Hebrew University, Jerusalem, Israel.

Lachmy, O. (2019), The effect of moisture on the Ferrel circulation (oral presentaion), The symposium on Geophysical Fluid Dynamics, January 2019, Ben Gurion University, Sede Boqer, Israel

Lachmy, O. and N. Harnik (2018), A transition between a quasi-linear and nonlinear regime of the tropospheric jet stream (oral presentation), European Geosciences Union general assembly 2018, April 2018, Vienna, Austria

Lachmy, O. and T. A. Shaw (2017), Connecting the energy and momentum flux response to climate change using the Eliassen and Palm relation (oral presentation), 21st Conference on Atmospheric and Oceanic Fluid Dynamics, The American Meteorological Society, June 2017, Portland OR, USA.

Lachmy, O. and N. Harnik (2015), Variability patterns and eddy feedbacks in different flow regimes of the jet stream (oral presentation), 20th Conference on Atmospheric and Oceanic Fluid Dynamics, The American Meteorological Society, June 2015, Minneapolis MN, USA.

Lachmy, O. and N. Harnik (2015), Equilibration of the wave energy spectrum in different jet regimes (poster), Theoretical Advances in Planetary Flows and Climate Dynamics, March 2015, Ecole De Physique, Les Houches, France.

Lachmy, O. and N. Harnik (2015), Equilibration of the wave spectrum in different jet regimes (oral presentation), The Symposium on Geophysical Fluid Dynamics, January 2015, Ben Gurion University, Sede Boqer, Israel.

Lachmy, O. and N. Harnik (2014), Flow regimes of the jet stream and their maintenance (poster), The Latsis Symposium on Atmosphere and Climate Dynamics, June 2014, ETH Zurich, Switzerland.

Lachmy, O. and N. Harnik (2014), Characteristics of three flow regimes of the upper tropospheric jet stream (oral presentation), Symposium on Physical Aspects of Global and Regional Climate Dynamics, January 2014, Ben Gurion University, Sede Boqer, Israel.

Lachmy, O. and N. Harnik (2013), Flow regimes of the upper tropospheric jet stream (oral presentation), Bifurcations and Instabilities in Fluid Dynamics, July 2013, Technion, Haifa, Israel.

Lachmy, O. and N. Harnik (2012), Wave-mean flow interactions maintaining subtropical and midlatitude jets (oral presentation), Symposium on Physical Aspects of Global and Regional Climate Dynamics, November 2012, Ben Gurion University, Sede Boqer, Israel.

Lachmy, O. and N. Harnik (2011), Extratropical wave-mean flow dynamical feedbacks and their interaction with the Hadley circulation (poster), Hierarchical Modeling of Climate, July 2011, ICTP Trieste, Italy.

Lachmy, O. and N. Harnik (2009), A wave amplitude transition in a quasi-linear two-layer model (poster), Reducing the Uncertainty in the Prediction of Global Warming, January 2009, The Hebrew University, Jerusalem, Israel.

Rossbypalooza, Climate Meets Statistics at the University of Chicago, July 2016, Chicago IL, USA.

Alpine Summer School on Fronts, Waves and Vortices, June 2006, Valsavarenche, Italy.

Member of the American Meteorological Society, 2015 - 2016.

Reviewer for the Quarterly Journal of the Royal Meteorological Society, 2017 - present

Reviewer for the Journal of Geophysical Research, 2015 - present.

Reviewer for the Journal of the Atmospheric Sciences, 2009 - present.

Research

Flow regimes of the atmospheric jet stream

​The atmospheric jet stream appears sometimes as a region of strong zonal winds concentrated at the upper tropospheric subtropics, referred to as the subtropical jet, and sometimes it appears as a meandering band of winds in the midlatitudes, associated with surface westerlies, known as the eddy driven jet. The two types of jets sometimes merge to a single jet and sometimes separate. The dominant type of jet depends on the location, season and year. 
 

In my PhD research with Prof. Nili Harnik​ we have revealed the mechanisms that control the regime transition between the subtropical, merged and eddy driven jet states in an idealized configuration. Our ongoing work is concerned with the dynamics that control changes in the variability characteristics of the jet as it transitions between the different regimes. 


The response of the atmospheric circulation to climate change 

​Climate models generally predict a poleward shift of the eddy driven jet stream in response to increased greenhouse gas concentration. However, there is a large spread in the jet shift between different models and the physical reasons for this shift are not fully understood. The storm tracks associated with the eddy driven jet are also expected to shift poleward in response to climate change. Several theories have been proposed to explain the storm track shift and the eddy driven jet shift, yet there is no complete theory that connects the latitudes of the storm track and eddy driven jet.

 

In collaboration with Prof. Tiffany Shaw​ we have studied the connection between the latitudes of the storm track and eddy driven jet using the Eliassen and Palm relation, which connects the eddy energy and momentum fluxes. We found that differences in the climatological mean flow can lead to opposite eddy driven jet shifts, while the poleward storm track shift is more robust. The analysis of the terms in the Eliassen and Palm relation showed that the eddy phase speed and the response of the mean flow to climate change are not necessary for predicting the eddy driven jet shift, given the eddy energy flux response. 


The effect of latent heating on the general circulation of the atmosphere 

Latent heat release associated with midlatitude storms is an important component of the midlatitude heat budget. Latent heating, radiative cooling, meridional and vertical heat fluxes as well as adiabatic heating or cooling due to the mean vertical wind are the major components of the heat budget. Since adiabatic cooling and heating by the vertical motion of air is related to the location of the mean circulation cells, any change in the heat budget affects the general circulation of the atmosphere. In warmer climate conditions latent heating increases, due to the increase of saturation specific humidity with temperature. Warming would therefore increase the contribution of latent heating to the heat budget, potentially affecting the circulation. In collaboration with prof. Yohai Kaspi​, we study the midlatitude heat budget and the effect of latent heating on the structure of the Ferrel cell, the jet stream and the storm tracks and the relations between them.

  • 2017-present: Head of the Earth Sciences field in the Department of Natural Sciences, the Open University of Israel. Academic responsibility for the courses: "Introduction to Meteorology", "Synoptic Meteorology Laboratory" and "Modern Problems in Atmospheric Sciences".
  • 2007-2008: Teaching assistant in the courses “Atmosphere Dynamics” and “The General Circulation of the Atmosphere” at the Department of Geosciences, Tel Aviv University.
  • 2004-2005: Laboratory instructor for third year undergraduate physics students, The Racah Institute of Physics, The Hebrew University.

Student / Research assistant oppotunities

M.Sc. and Ph.D. student as well as reserach assistant opportunities are available in my group. For more details please send me an e-mail to: orlila@openu.ac.il.

Postdoctoral Researcher

I am searching for a postdoctoral researcher to work on a collaborative project with me and Prof. Yohai Kaspi from the Weizmann Institute of Science.

 

The project investigates the effect of midlatitude latent heat release on the general circulation of the atmosphere. Commonly accepted theories of the midlatitude atmospheric circulation are based on dry dynamics, assuming that dry eddy heat flux divergence and convergence balance the adiabatic heating and cooling by the mean meridional circulation. However, latent heat release associated with midlatitude storms turns out to be an important component of the midlatitude heat budget, potentially affecting the latitudinal structure of the storm track and eddy-driven jet. Latent heating is expected to increase in response to increased greenhouse gas concentration. While the effect of increased tropical latent heating on the general atmospheric circulation has been extensively studied, the effect of midlatitude latent heating has received little attention.

 

The postdoctoral researcher will be required to set up a series of numerical simulations using an idealized general circulation model and to analyze comprehensive climate model output and reanalysis data, in order to assess the role of midlatitude latent heating in the atmospheric circulation of the present climate and under climate change conditions.

 

The position requires:

  • A PhD in atmospheric science or a related field.
  • Strong background in atmosphere dynamics, numerical modeling and data analysis.
  • Excellent communication skills and the ability to work both independently and collaboratively. 

 

The position is available immediately. Applications will be accepted until the position is filled. Full funding is available for the suitable candidate. The position is initially for one year, with the possibility of an extension for additional one or two year, subject to satisfactory progress.

 

Please send the application material, including a cover letter, curriculum vitae, publication list and contact details of at least two academic references to: orlila@openu.ac.il.