Observing Climate Effect on Hurricanes Through Hurricane Clustering Methods

When measuring hurricane variability, there are different variables taken into account when measuring the data. Storm intensity, duration, frequency, genesis location, and track all contribute in part to the observed data. In addition to these direct effects that change the thermodynamic state of the storm, there are also indirect effects, most notably climate variations that affect circulation patterns such as the El Niño Southern Oscillation Event (ENSO) (Kossin et al., 2010). The changes in atmospheric currents and vertical wind sheer affect North Atlantic hurricane activity by altering the storm duration. There is an increasingly important need to examine hurricane track in order to determine if there is a correlative relationship between climate change and storm intensity. The results suggest that it is not beneficial to utilize Atlantic tracks when observing hurricane models when attempting to quantify the global effects of climate change and track.  It is necessary to include different variables for each track in order to determine how tropical storms and hurricanes have responded to changes in climate variability.  According to projections, systematic increases in landfall and statistics and distributions of storm intensity are likely to occur, which makes it difficult to predict climate activity.—Brian Nadler
Kossin, J.P., Camargo, S.J., and Sitkowski, M. Climate Modulation of North Atlantic Hurricane Tracks. Journal of Climate, Vol.23. 3057 – 3078.

          The possibility is raised that climate change might significantly affect storm frequency in areas such as the North Atlantic. In order to further explore such a possibility, Kossin et al. separated tracks from the North Atlantic hurricane database ranging from 1950 to 2007 and clustered them into four groups based on techniques used in other ocean basins. The composites of each group vary from each other and are remarkably similar, demonstrating that the different oscillation events have influential holds on North Atlantic tropical storms and hurricanes.
          J.P. Kossin and colleagues conducted this research at the University of Wisconsin. Data were obtained through the hurricane database (HURDAT) that is maintained by the National Oceanic and Atmospheric Administration (NOAA). A range of 58 years was covered, from 1950 to 2007, and composite analysis of the sea surface temperatures at those times were recorded using a reconstructed database. Any other regional composites were performed at the National Centers for Environmental Prediction—National Center for Atmospheric Research (NCEP—NCAR). The results showed that when considered by individual clusters, the largely documented increase in North Atlantic hurricanes is confined to deep tropical systems, correlated to regions that display positive SST trends.

          Throughout the study there were various differences in tropical storm longevity and intensity, and the proportion and destructiveness of landfalling storms were indentified. The results of the study suggest that it is not useful to consider Atlantic tracks in their entirety when quantifying the climatic control of tropical cyclogenesis and track, which storm activity is dependent on.  This adds to the challenge of predicting future hurricane or tropical storm activity because it requires that climate models do two things: capture systematic changes in circulation patterns throughout the atmospheric region, and observe mean thermodynamic state changes. More in-depth research will be necessary to improve these attempts at clustering data, for at best, the analyses in this study are only useful as a rough tool for separating tropical storm and hurricane tracks, and it is stated that caution must be used when relating differences within a tropical storm cluster to actual physical mechanisms. 

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