The Effect of Sea Surface Temperature Fronts on Atmospheric Frontogenesis

Abstract

It is thought that the sensible heat fluxes associated with sea surface temperature (SST) fronts can affect the genesis and evolution of atmospheric fronts. An analytic model is developed and used to explore this idea. The model predictions are compared with climatologies of atmospheric fronts over the North Atlantic Ocean identified in reanalyses. The climatologies are divided into times when fronts are detected at a point and times when they are not, and compared with model results with and without fronts in their initial conditions.In airstreams with fronts, both the climatologies and model show that adiabatic frontogenesis is much more important than diabatic frontogenesis. They also show that there is weak diabatic frontogenesis associated with differential sensible heating over the SST front and frontolysis either side of it. Because of the upstream and downstream frontolysis, the SST front has relatively little net effect on atmospheric fronts in the model. This result holds true as the width and strength of the SST front changes.In airstreams initially without fronts, a combination of adiabatic and diabatic frontogenesis is important for the local genesis of atmospheric fronts over the SST front. The model shows sustained frontogenesis only when the deformation is sufficiently strong or when the translation speed is low, as advection otherwise weakens the potential temperature gradient. This strong localized diabatic frontogenesis, which is amplified by adiabatic frontogenesis, can result in a front, which is consistent with atmospheric fronts in the region being most frequently located along the SST front.

The role of atmospheric fronts in austral winter precipitation changes across Australia

“…Figure 1) can significantly alter atmospheric frontogenesis through diabatic heating effects. Further studies by Masunaga et al (2020) and Reeder et al (2021) suggest that any such effect would likely manifest in changes to the very weakest, or quasi‐stationary fronts, as is found here. As such, one possibility is that precipitation changes in Northwest Australia may be influenced by direct SST impacts on atmospheric frontal frequency.…”

A Monthly Index for the Large‐Scale Sea Surface Temperature Gradient Across the Separated Gulf Stream

“…It would also be interesting to explore the relationship between the GS SST gradient index and the latitudinal and path length variability of the GS, although preliminary analysis suggests no obvious co‐variability on a monthly timescale (not shown). Application of an analogous methodology for daily timescales is also warranted, given that several studies have noted the importance of the GS SST gradient on daily timescales or shorter (Parfitt & Seo, 2018; Reeder et al., 2021). In relation to this last point, it may also be prudent to investigate whether the SST itself can be used to define such a GS SST gradient metric, which would provide the benefit of a longer record (1982‐present for SST vs. 1993‐present for SSH) and also all analysis would be limited to one data product.…”

From a Shapiro–Keyser extratropical cyclone to the subtropical cyclone Raoni: An unusual winter synoptic situation over the South Atlantic Ocean

“…F was computed at 850 and 700 hPa and then averaged. F has been commonly applied in studies related to fronts and extratropical cyclones, such as Reboita et al (2009), Brâncuş et al (2019), Zhao et al (2020), andReeder et al (2021).…”