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Following up on our initial submission last January, we’ve just resubmitted our paper on using machine learning to represent un(der)resolved gravity waves in atmospheric models.
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The kitchen has been busy: two papers are now in press. First, Marianna Linz’s paper on mixing in the stratosphere was just accepted by the Journal of Geophysical Research: Atmospheres. We show how the vertical gradients in age allow us to quantify the exchange of air between the tropics and extratropics. Increased mixing leads to better baking, right? In this case, it’s very important for transporting ozone and water vapor through the stratosphere, two trace gases that impact us on the surface, protecting us from UV radiation and keeping us a bit warmer, respectively.
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To conserve the number of papers in my queue, Justin Finkel submitted a new manuscript just as our MWR paper was accepted. Exploring stratospheric rare events with transition path theory and short simulations, submitted to the Journal of the Atmospheric Sciences, takes a deeper dive into the idealized Holton and Mass (1976) model of Sudden Stratospheric Warming events using Transition Path Theory, TPT for short.
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While I was returning from summer travels, the journals went into overdrive and three papers were accepted and/or came out in press!
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The SPARC Reanalysis Intercomparison Project report has been published in an early online release! This has been nearly a decade in the making – I had only one child when I first got involved – but the long effort has really paid off. I am of course partial to Chapter 6, Extratropical Stratosphere-troposphere Coupling, but the entire report is full of information about the reanalyses and the stratosphere.
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Our monsoon paper was just accepted for publication in Geophyiscal Research Letters. See my December post for more details.
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Please see our paper exploring the role of “isentropic mixing” on the transport of trace gases through the stratosphere, just submitted to the Journal of Geophysical Research: Atmospheres. 
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Please see our on the impact of stratospheric ozone loss on the atmosphere across the latest reanalysis products, just accepted in Atmospheric Chemistry and Physics. 
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A fun article on NYU’s new Greene supercomputer and how it allows us to explore climate change came out in NYU IT’s Download Newsletter.
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Please see our new paper providing a recipe for generating and optimizing a Quasi-Biennial Oscillation in your very own GCM, just submitted to JAMES. 
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Check out our new paper exploring the origin of tracer transport biases in atmospheric models, just submitted to the Journal of the Atmospheric Sciences. 
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Please see our new paper adopting a novel prediction framework from computational chemistry to forecast extreme meteorological events, just submitted to Monthly Weather Review. The paper, led by Justin Finkel, presents a proof of concept study using a stochastically forced version of the classic Holton and Mass (1976) model of Sudden Stratospheric Warming events. We establish the “committor”, which provides the ideal combination of variables for predicting SSWs (where an SSW is a transition between the two fixed points in the Holton-Mass model). We also establish a method to compute it from relatively short integrations, i.e., integrations that are short relative to the time scale of the event, and much shorter than the return time scale of events. 
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The newly minted Institute for Mathematical and Statistical Innovation has organized a virtual conference on climate change from 1-5 March, 2021. Speakers including experts in applied mathematics and climate research – and both, including my colleague Laure Zanna! It’s my understanding that the meeting is free to atttend, but that you must register in advance.
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As my family and I cannibalize each other on our solitary descent into the abyss that is remote elementary education, intrepid collaborators will be hitting the virtual road to present at the vEGU this April! Check out these presentations:
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Despite tremendous advances in our understanding of the atmosphere and our capability to simulate it with numerical models on the fastest computers in the world, their remain processes that we can not accurately represent from basic physical principles. In some cases, it is an issue of computational power: we cannot resolve all relevant scales for climate prediction, from planetary scale weather systems (10^6=1,000,000’s of meters) to cloud and aerosol particles on the microscale (10^-6=0.000001 m). In other cases, we do not yet know all the relevant physics! We still need to do our best to represent these processes based on what we can simulate. Traditionally this has been done with physically motivated schemes, but there’s growing in interest in using machine learning to help. Here we take the first steps of using an artificial neural network to help parameterize atmospheric gravity waves.
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Suppose you could build your own planet: create continents, lift mountains, carve out the bathymetry of the ocean to help direct its currents! What would you need to do to create the monsoonal circulation on Earth, the sharp seasonal transitions in rainfall that play such a huge role in the climate of South and East Asia?
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The short answer is: no! For a longer, more complete answer, please see our new paper on the representation of the stratospheric ozone hole on the Southern Hemisphere in the four latest atmospheric reanalyses, just submitted to Atmospheric Chemistry and Physics.
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Our review article on Sudden Stratospheric Warmings, led by Mark Baldwin and Blanca Ayarzuguena, was just accepted for publication in Reviews in Geophysics. We’ve learned a great deal about “explosionartigen Stratosphärenerwärmungen” since they were first discovered by Prof. Dr. Scherhag almost 70 years ago!
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A number of postdoctoral positions are available through a project funded by NSF’s Cyberinfrastructure for Sustained Scientific Inquiry (CSSI) program. This highly collaborative project between four institutions will develop data-driven parameterizations of atmospheric gravity waves and explore their impact on climate variability and change. The project will involve novel balloon-based observations, high-resolution atmospheric model simulations, machine learning, and atmospheric modeling.
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I am aware that things have been rather quiet on my blog in the last months. In addition to my new found profession as an elementary school teacher (alas, not a very good one, but our efforts to get the kids transferred to another class were fruitless), we’ve been hard at work on revisions. Some very detailed and careful reviews allowed us to make two good papers even better!
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After a month in editorial system purgatory, just submitted to Geophysical Research Letters, our paper on “Downward migration of the zonal-mean circulation in the tropical atmosphere”, led by Kevin DallaSanta.
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(*but were afraid to ask!) Please see our review paper, just submitted to Reviews of Geophysics, “Sudden Stratospheric Warmings”, led by Mark Baldwin and Blanca Ayarzuguena.
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Just submitted to the Journal of Climate, our paper on “The impact of SST biases in the tropical east Pacific and Agulhas current region on atmospheric stationary waves in the Southern Hemisphere”.
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A quick update on an earlier post: our paper exploring the impact of global warming stratosphere-troposphere coupling, was just accepted for publication in the Journal of Geophysical Research: Atmospheres. Look here for more details!
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Please see our new paper exploring stationary waves in the Northern Hemisphere, just accepted in the Journal of Climate. What are stationary waves, you ask? In laymen’s terms, they are variations in climate with longitude, for example, the reason why the weather in Madrid is quite different from that here in New York, even though we’re both situated at nearly the exact same latitude.
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Please see our new paper exploring the impact of global warming stratosphere-troposphere coupling, just submitted to the Journal of Geophysical Research: Atmospheres.
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Aman Gupta is defending his thesis on Wednesday 18 December at 1:15 in Warren Weaver 1302. Come see the world’s leading expert on trace gas transport through the stratosphere by the dynamical cores of atmospheric models!
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Please see our new paper exploring the role of model numerics on trace gas transport, just submitted to the Quarterly Journal of the Royal Meteorological Society.
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Please see our new paper on the tropospheric response to extreme events in the stratosphere, just submitted to the Journal of Climate. Update: this paper was accepted for publication in January 2020!
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Our commentary for the Journal of Advances in Modeling Earth Systems, “Imagining Simpler Worlds to Understand the Complexity of our Own”, was just accepted for publication. It follows on a nice paper by Zhihong Tan, Orli Lachmy, and Tiffany Shaw that recently appeared in the same journal.
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Please see our chapter on extratropical stratosphere-troposphere coupling, just submitted as Chapter 6 of the SPARC Reanalysis Intercomparison Project, S-RIP. I’m quite pleased by the final (or at least, submitted) product! Kudos to Patrick Martineau, my co-lead on this 17 author effort which started over 6 years ago. Six years ago, a far away time when I only had one kid. To say that I’m very relieved to have this submitted is an understatement!
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An updated on our workshop on the Atmospheric Circulation in a Changing Climate, 22-25 October 2019, Madrid, a joint DynVarMIP, SPARC DynVar, and SNAP meeting, hosted by Universidad Complutense Madrid, Instituto de Geociencias.
Check out our line up of invited speakers!
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Just submitted to JAMES: our commentary on a nice paper by Zhihong Tan, Orli Lachmy, and Tiffany Shaw that recently appeared in the same journal. We make the case that models of simpler atmospheres – which are distinct from simple models of our atmosphere – can help us understand the circulation response of our atmosphere to global warming, and enable us to build better climate prediction models!
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Please come to our workshop on the Atmospheric Circulation in a Changing Climate.
22-25 October 2019, Madrid
A joint DynVarMIP, SPARC DynVar, and SNAP meeting, hosted by Universidad Complutense Madrid, Instituto de Geociencias. A substantial amount of travel support is available for Early Career Scientists and participants from underrepresented nations!
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Our manuscript for Reviews of Geophysics, Model hierarchies for understanding atmospheric circulation, was just accepted! Way to go Penny! In particular, I like our new figure illustrating the web of models around state-of-the-art Atmospheric General Circulation Models (AGCMs). These hierarchies of simpler models enables us to understand and improve our weather and climate prediction systems. 
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While Rome and New York receive the same amount of energy from the sun (being situated at the same latitude), the former experiences a much warmer climate, particularly in the winter months. This is due to large variations in the atmospheric flow with longitude, known as “stationary waves”. It has long been known that these variations are generated by differences between land and sea, topography, and variations in sea surface temperatures. But just how do these different components add up to produce our climate?
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The whole group is hitting the road. Check out talks in Boulder, Palo Alto, and uptown, to be helf over the next couple weeks!
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Coming to the AMS Annual Meeting in Phoenix next week (6-10 January)? Check out these presentations!
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Please see our paper Quantifying the variability of the annular modes: Reanalysis uncertainty vs. sampling uncertainty, just accepted in Atmospheric Chemistry and Physics. Patrick Martineau and I show that reanalyses have gotten quite good, and we are chiefly limited by the finite length of the observational records. In this sense, we are starved for data, not model physics!
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Deterministic weather forecast are only possible for one to two weeks. (Or in other words, we just can’t predict whether it will be sunny or rainy 14 days from now.) But can we say something about the weather over the next few weeks, for example, will it be warmer and drier than average, even if we can’t say exactly which days will be sunny?
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Why do some Sudden Stratospheric Warmings appear to influence the troposphere, shifting the jet stream equatorward over the next 2-3 months, while others don’t? Much of the issue is tropospheric variability, which can overwhelm the influence of the stratosphere. However, our recent study, The Downward Influence of Sudden Stratospheric Warmings: Association with Tropospheric Precursors shows that there are regional patterns that can help us predict whether a Sudden Warming is more likely to have an influence on the troposphere!
