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17 years of storms and hurricanes tracked by scatterometers

Wednesday 20 August 2008

Scatterometers are satellite embedded microwave radar specially designed to measure the sea surface wind speed and direction under all weather and cloud conditions. Since the launch of ERS-1 in 1991, sea surface winds have been continuously measured at global scale thanks to an uninterrupted series of missions such as ERS-2; ADEOS-1, QuikSCAT, ADEOS-2 and now METOP-A. We have scanned the complete archive of some of these missions (currently ERS-1, ERS-2, QuikSCAT and METOP-A) in order to identify and register a complete index of all storm observations. Users with a focus on extreme wind events can now access through Naiad this extensive catalogue which spans over more than 17 years. This work was supported by ESA, as part of the enhancement of the legacy of ERS missions.

Several years orbit swath files of scatterometer measurements were parsed in order to detect any strong wind event. The identified swath sections matching a storm have been registered as an index into Naiad system for each processed scatterometer, namely AMI-Wind onboard ERS-1 and ERS-2, SeaWinds onboard QuikSCAT and ASCAT onboard METOP. For each identified section featuring a (supposed) storm, some properties describing it are computed (that can be used later as search filters), such as :

  • maximum measured wind speed
  • maximum vorticity and divergence
  • correponding wind speed estimated by weather model (ECMWF analysis)
  • hurricane or typhoon name, propagation velocity and direction, maximum wind speed, storm stage if available (as provided by NHC and JMA reports)
  • ....

For a complete description of the methodology and content of the index, refer to the following article.

This index can now be used for more focused data queries on storm observations. The methodology developed to extract these wind features is fully applicable to any other scatterometer and we plan a similar processing of NSCAT onboard ADEOS-1 and SeaWinds onboard ADEOS-2 data. Our longer term goal is to correlate thesel atmospheric features with other extreme events or anomalies of the ocean surface dynamic like high energy swell systems or strong local currents that can be observed with other sensors (such as SAR). This index will then be updated with information provided by swell spectra by tracking them from their observation to their generation location. This new type of information will make possible to assess the storm detection from scatterometer and will complement them to allow a more accurate estimation of the total energy transfered from the atmosphere to the ocean during a given storm.

To use this index, select one of the processed scatterometer products in the catalogue, modify the default index by choosing the 'StormWatch' index. Check also the video tutorial here.