Characteristics of cyclones following different pathways in the Gulf Stream region

Leonidas Tsopouridis,Thomas Spengler,Clemens Spensberger

doi:10.1002/qj.3924

Leonidas Tsopouridis, Thomas Spengler + Show 1 more

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https://doi.org/10.1002/qj.3924

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Abstract

AbstractThe Northwest Atlantic is a region of strong temperature gradients and hence is a favourable location for wintertime cyclone intensification co‐located with the storm track. The temperature gradient is associated with both the sea surface temperature front along the Gulf Stream and the land–sea contrast. To understand the respective influences of the sea surface temperature (SST) front and land–sea contrast in the Gulf Stream region, as well as the role of upper‐level forcing on cyclone development, we track individual cyclones and categorise them depending on their propagation relative to the SST front. We concentrate on cyclones staying either on the cold (C1) or warm (C2) side of the SST front, and on cyclones that cross the SST front from the warm to the cold side (C3). Comparing these categories, we find that the land–sea contrast is more important for supplying baroclinicity to cyclones in C1, while the strong low‐level baroclinicity in C3 is also partially attributable to the SST front. The propagation of cyclones in C1 and C3 near the left exit region of the North Atlantic jet explains the higher intensification and precipitation.

Highlights

The western North Atlantic region is characterized by both strong sea surface temperature (SST) gradients associated with the Gulf Stream (Tomczak and Godfrey, 2003) and strong land–sea temperature contrasts during winter (Thompson et al, 1988)
We present cyclone-relative composites for category 1 (C1), category 2 (C2), and category 3 (C3) to clarify the potential role of the SST front, the land–sea contrast, and upper-level forcing on the cyclone structure and intensity
We considered cyclones which stay either on the cold (C1) or warm (C2) side of the SST front, and those crossing the SST front from the warm to the cold side (C3)

Summary

Introduction

The western North Atlantic region is characterized by both strong sea surface temperature (SST) gradients associated with the Gulf Stream (Tomczak and Godfrey, 2003) and strong land–sea temperature contrasts during winter (Thompson et al, 1988). The origin of the baroclinicity has been argued to be due to the Gulf Stream SST gradient (Sanders, 1986) and the land-sea contrast (Wang and Rogers, 2001). Several studies have highlighted the importance of diabatic heating and surface heat fluxes on maintaining low-level baroclinicity in the area of strong SST gradients (Kuo et al, 1991; Reed et al, 1993; Nakamura et al, 2004; Hotta and Nakamura, 2011; Papritz and Spengler, 2015). Hotta and Nakamura (2011) underlined the significance of sensible heat fluxes for restoring low-level baroclinicity along oceanic frontal zones, while Papritz and Spengler (2015) emphasised latent heat release as a major contributor maintaining baroclinicity in the Gulf Stream region. de Vries et al (2019) found that cyclones respond to both the low-level baroclinicity associated with the SST front as well as the additional moisture provided by altered surface latent heat fluxes associated with changes in the SSTs

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