@article{Weather:1366,
      recid = {1366},
      author = {Plotkin, David Ariel},
      title = {Rare Events in Weather and Climate},
      publisher = {University of Chicago},
      school = {Ph.D.},
      address = {2018-12},
      pages = {95},
      abstract = {Rare and/or extreme events in weather and climate often  have particularly important implications for human welfare.  Despite this, these events are often poorly understood  since they are difficult to simulate and are, by  definition, rarely observed. In this thesis, we present and  apply rare event algorithms to both better characterize and  better simulate specific rare events in the ocean and  atmosphere systems.

First, we use diffusion maps and  spectral clustering, a machine learning technique, to  better characterize the large and small meanders of the  Kuroshio current near Japan. This current has long been  considered to be bimodal; however, there have been few  data-driven efforts to confirm this bimodality or to  characterize the predominant states. By applying the  diffusion maps and spectral clustering algorithm in an  oceanographic context for the first time, we show that the  Kuroshio is indeed bimodal but that the two most common  states are characterized by high and low variability rather  than by current location (as was previously thought to be  the case). We also show that the meanders correlate with  the location of a nearby recirculation gyre, thereby  providing evidence for a meander transition mechanism that  depends on the movement of this gyre.

Second, we apply  action minimization to the study of tropical cyclone rapid  intensification by perturbing the Weather Research and  Forecasting model into forming more intense storms than it  otherwise would. We show that, compared to ensemble methods  commonly used in the study of intensification, this method  yields significant computational savings in accessing the  tail of the intensification distribution. Action  minimization generates maximum likelihood pathways of  intensification, thereby allowing us to characterize the  preferred intensification mechanisms in the model. We find  that action minimization chooses physically realistic  intensification mechanisms including low-level heating and  the reduction of vertical wind shear. Further, we show that  asymmetric heating can cause significantly more  intensification than purely symmetric heating and discover  a regime of non-linear storm response to asymmetric heating  that has not been previously observed.},
      url = {http://knowledge.uchicago.edu/record/1366},
      doi = {https://doi.org/10.6082/uchicago.1366},
}