Surface wind and vertical extent features of the explosive cyclones in the Northern Hemisphere based on the ERA‐I reanalysis data

Abstract

Although explosive cyclones (ECs) have long been a focus of research, there remains a lack of knowledge of the statistical characteristics of their associated maximum surface winds and vertical extents. This study fills this gap by conducting a targeted statistical analysis of ECs in the Northern Hemisphere using the ERA-I reanalysis data during a 40-year period. Some new findings are obtained: (a) The average location of formation of ECs undergoes a notable westward and equatorward shift from September to April in the next year which is consistent with the location variations of sea surface temperature's strong gradients in subtropical regions. (b) Extreme ECs with a deepening rate more than 2.0 Bergeron or with a longer lifespan more than 10 days tend to have a larger occurrence number over the Northern Atlantic Ocean than over the Northern Pacific. (c) The maximum surface wind associated with an EC tends to appear between the EC reaching its maximum deepening rate and reaching its minimum central pressure. (d) The northeastern quadrant of ECs accounts for the highest proportion of maximum surface wind and strongest wind speed, as the baroclinic energy conversion is generally strongest in this quadrant. (e) Over 60% of ECs belong to a type of vertically deep cyclone (ECs' top levels show close relationship to ascending motions within their central regions), and they tend to reach their maximum vertical extent around the time when they reach their minimum central pressures. (f ) The highest top levels of ECs exhibit an overall upward extending trend as their minimum central pressure decreases or their maximum deepening rate increases.

Increasing risks of the explosive extratropical cyclones over the North Atlantic storm track: a perspective from their surface wind maxima

“…field correlation) to track the cyclone structures. After manual verifications (which had removed almost all errors that could not be solved by the objective detecting/tracking algorithms themselves), Jiang et al (2021a) determined a total of 961 EECs over the NAST. We used the method proposed by Yoshida and Asuma (2004) to calculate the deepening rate of an EEC:…”

“…In meteorology, the winter storms called the explosive extratropical cyclones (EECs) are defined as the extratropical cyclones that deepen in their central pressure by at least 24 hPa (relative to the equivalent latitude of 60 • ) in one day (Sanders and Gyakum 1980). Generally, the radii of the EECs are ranging from 500 km to 2000 km during their mature stage (Jiang et al 2021a). The EECs' rapid intensification causes strong winds surrounding the cyclones' centers.…”

“…The EECs' rapid intensification causes strong winds surrounding the cyclones' centers. Although most of the EECs-associated strong winds appear over ocean (Zhang et al 2017, Jiang et al 2021a, 2021b, a few of them occur over land and coastal regions, which poses a great threat to these areas (Browning 2004, Knox et al 2011, Fu et al 2014, Booth et al 2015, Brâncus ¸et al 2019, Jiang et al 2021a, 2021b. Of the EEC-associated strong surface winds, there is a maximum value during the cyclone's whole lifespan.…”

“…Of the EEC-associated strong surface winds, there is a maximum value during the cyclone's whole lifespan. Jiang et al (2021a) define it as the maximum surface wind (MSW) of the EEC, which has the greatest destructive power among all strong winds associated with the EEC. Although the EECs have been investigated for almost a century (e.g.…”

“…It roughly corresponds to the cyclones' trajectories. After analyzing the strong winds associated with 961 EECs in this area, Jiang et al (2021a) found that, the EECs over the NAST had a mean MSW ranging from 27.3 m s −1 to 30.4 m s −1 , which was higher than the threshold of 26 m s −1 for a high-wind event defined by the US National Weather Service (Lacke et al 2007, Knox et al 2011, Booth et al 2015. Strong winds of this intensity can induce huge ocean waves with a wave-height of ∼10 m, which is fatal to most ships in the ocean.…”