Dr. Orli Lachmy

Discipline: Atmospheric Science

Expert in: Atmosphere dynamics

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Key words: The general circulation of the atmosphere, storm tracks, jet streams, climate variability 

What are you currently researching?
My current research projects deal with the structure of the general atmospheric circulation, specifically the location of the midlatitude storm track and jet stream. The storm tracks are regions of high weather variability and precipitation in the midlatitudes. The variability of storm tracks determines regional climate patterns in the midlatitudes. Climate models predict a poleward shift of the storm tracks and jet stream in response to increased greenhouse gas concentration. This response, in addition to the natural variability of the midlatitude climate, motivates our need to obtain a solid physical understanding of midlatitude dynamics. In my current research, I focus on the effect of moisture on the structure of the midlatitude circulation and on the subtropical jet and its interaction with the midlatitude storm track. 

How did you become involved in your research field?
After my bachelors degree in physics, I was interested in learning more about the world around us. Specifically, I enjoyed studying thermodynamics and fluid dynamics. Luckily, I found a wonderful supervisor in the Geophysics department at Tel Aviv University – Prof. Nili Harnik – who motivated me to get involved in atmosphere dynamics research. I discovered a fascinating field of research, which is both intellectually stimulating and relevant to burning issues concerning human society.     

What inspired you to become a researcher?
The main driver for my work is the intellectual challenge in trying to entangle a physical problem. The dynamics of atmospheric circulation is still, in part, a mystery to us, and new insights are continuously emerging as more observational data and computational capabilities become available. It excites me to take part in the communal effort to unravel the physical mechanisms controlling atmospheric circulation and the structure of Earth’s climate.  

Which of your research findings would you like to highlight?
One of our findings concerns atmospheric jet regimes. An atmospheric jet stream sometimes takes the form of a strong, stable jet in the subtropics, around 10 km above the ground, and sometimes it appears as a meandering, fluctuating jet in the midlatitudes, continuing from the surface to the upper troposphere. We found that the stabilization of storms at low latitudes is essential for the maintenance of the subtropical jet regime, and that an increase in a storm's amplitude triggers a transition of the jet to the midlatitude regime, where it becomes more turbulent. This finding has contributed to understanding the observed transitions in the atmospheric flow regimes, and helped explain observed relations between the storm track properties and the jet properties. A more recent finding from our research revealed the important role of moisture in the midlatitude circulation. We found that latent heat release from midlatitude storms is a significant term in the midlatitude heat budget, which leads to decoupling between the variability of the midlatitude jet and the variability of poleward heat transport by midlatitude storms. We are now investigating the implications of this finding for the response of the atmospheric circulation to climate change.

How does your research link to todays' challenges?
With the growing human population and its impact on the environment and on Earth’s climate, it is crucial for society to have scientific knowledge about climate variability and change, in order to make knowledgeable decisions and planning regarding all aspects of the interface between humanity and climate. In my field of research, we contribute to understanding the processes that control climate variability and its response to anthropogenic forcing. An improved theoretical understanding of these processes leads to better and more accurate predictions, which ultimately serve the decision makers.
What excites you regarding your research field?
I find my research field exciting, because it is continuously evolving, both due of new capabilities and due to the growing need to prepare for the impacts of climate change. As our knowledge progresses, we find more open questions and we discover how much we still don’t know about atmospheric circulation, which is a fascinating dynamical phenomenon.