Atlantic hurricane reanalysis

Atlantic hurricane reanalysis

Atlantic hurricane reanalysis is an ongoing project within the National Oceanic and Atmospheric Administration which seeks to correct and add new information about past Atlantic tropical cyclones. It was started around 2000 to update HURDAT, the official hurricane database for the Atlantic Basin, which has become outdated since its creation.

Inaccuracies and omissions in existing data

Errors

HURDAT contains a number of errors which need to be corrected, such demonstrated by the outliers in the a pressure vs. wind speed graph of datapoints in the database (right). Some of these errors have existed since the database's creation during NASA's Apollo Program, where it was used to help produce probabilities of tropical cyclone-induced winds in critical areas such as Cape Kennedy (now Cape Canaveral).

New information

A significant amount of new data for systems between 1851 and 1886 became available after a major basin-wide reanalysis in 1996, a project led by Jose Fernandez-Paratagas with the collaboration of Henry Diaz. The new data was constructed using old newspaper articles and the hemispheric weather map series. Hurricane histories for individual states had been constructed by the 1990s as well, which proposed new storms and increased the knowledge of tropical cyclones already in the database. Due to this profusion of relevant information not included in HURDAT, and evolving definitions for tropical and subtropical cyclones over the decades, the project was started around 2000 to update the official database.

Incompleteness of dataset

As early as 1957, it was recognized that an increasing trend in the amount of tropical cyclones each season in the Atlantic Basin was at least partially tied to increasing observations and better records. By analyzing the density of ship tracks over time, it has been estimated that between 1900 and 1966, an average of two storms per year are missing from HURDAT. This is mainly due to a lack of satellite imagery and lack of reconnaissance aircraft prior to 1943. An additional storm per year is likely missing prior to the advent of new technologies. These technologies include satellite-derived Quikscat winds, satellite-derived temperature profile information, and Robert Hart's cyclone phase space diagrams, which have led to a recent increase in tropical cyclone detection. Quikscat was launched in 1999, and has been credited with allowing Chantal to be named during the 2007 Atlantic hurricane season. The latter two help determine whether or not a low pressure area is an extratropical cyclone, subtropical cyclone, or tropical cyclone.

Christopher Landsea noted that the efforts to reanalyze the Atlantic hurricane database “will not be able to recover observations of openocean tropical cyclones that were just never taken. Researchers cannot assume that the Atlantic tropical cyclone database presents a complete depiction of frequency of events before the advent of satellite imagery in the mid-1960s. Moreover, newly available advanced tools and techniques are also contributing toward monitoring about one additional Atlantic tropical cyclone per year since 2002. Thus large, long-term ‘trends’ in tropical cyclone frequency are primarily manifestations of increased monitoring capabilities and likely not related to any real change in the climate in which they develop.”

Progress

  • In 2001, data for the years 1851-1885 was added to the official database from the Fernandez-Partagas series of publications. Also, a paleotempestology conference was held at the University of South Carolina which proposed to increase the scope of HURDAT from a starting year of 1851 to a start of 1800. The conference also discussed ways of exchanging information for the inclusion of older tropical cyclones, such as via compact disc or a Wikipedia-style website.
  • In 2002, for the tenth anniversary of Hurricane Andrew, the reanalysis was completed for the hurricane, which upgraded the cyclone to a Category 5 hurricane.
  • In 2003, changes suggested by various sources for 1886 to 1910 were approved for the official HURDAT. Work by Michael Chenoweth, in collaboration with Cary Mock, increased knowledge of tropical cyclones in the Caribbean Sea for 1750 to 1786. (from The 18th Century Climate of Jamaica)
  • In 2004, additional corrections for the years 1851 through 1910 were included into the database.
  • In 2005, changes and additions were made for 1911 to 1914. Michael Chenoweth completed a basin-wide reassessment for old source material from the 1700 to 1855 period by using surface weather observations mainly in the form of ship reports, newspapers, and various diaries and journals from the region around the Caribbean Sea.
  • In 2006, four typographical errors were found and corrected in the 1851-1914 time period.
  • In 2008, revisions were completed from 1915 through 1920.

Future plans

The last published plan for the project (currently three years behind this schedule) called for completing the reanalysis for:

  • The years 1911 - 1940 by Spring 2005
  • The years 1941 - 1970 by Spring 2006
  • The years 1971 - 1999 by Spring 2007

By Spring 2008, plans called for investigating trends in the new database and relationship between the statistics and the Atlantic Multidecadal Oscillation and global climate change. If this plan were followed, accounting for the three year delay, the project will have taken twelve years to complete, with the effort of dozens of scientists from multiple disciplines, such as meteorology, geography, archaeology, and climatology.

Future efforts in other basins

There is agreement within tropical cyclone circles of doing an "Atlantic-style" reanalysis for other ocean basins. Some efforts are underway to start similar reanalyses across the Pacific Ocean, but are likely to take longer to complete. This is due to the need for coordination between the multiple Regional Specialized Meteorological Centres, which have the responsibility for tracking and forecasting tropical cyclones across that ocean. These tropical cyclone reanalyses are important, as theories concerning climate change and tropical cyclone trends hinge upon the quality of these databases.

References

World Wide Web

Books

  • Michael Chenoweth. The 18th Century Climate of Jamaica. American Philosophical Society: Philadelphia, 2003.

External links

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