A Potential Vorticity-Based Study of the Role of Diabatic Heating and Friction in a Numerically Simulated Baroclinic Cyclone

Using satellite and reanalysis data to evaluate the representation of latent heating in extratropical cyclones in a climate model

“…12, with the implication that the PV modification from latent heating plays a role in the divergent evolution of PV at upper levels. These results are consistent with case study analysis of the relationship between diabatic processes in the WCB and upper-level flow (e.g., Stoelinga 1996;Grams et al 2011;. The representation of the upper-tropospheric circulation around ETCs has implications for downstream development of ETCs, Rossby waves and blocking (e.g., Chagnon et al 2012;Rodwell et al 2013;Gray et al 2014;Martínez-Alvarado et al 2015;Pfahl et al 2015).…”

“…It is well known that latent heating can play a significant role in the evolution of ETCs (e.g., Manabe 1956;Sanders and Gyakum 1980;Davis et al 1993;Zhu and Newell 1994;Stoelinga 1996;Pomroy and Thorpe 2000) though this can vary substantially on a case-to-case basis (e.g., Kuo and Low-Nam 1990;Smith 2000;Wernli et al 2002;Dacre and Gray 2009;Fink et al 2012;Dearden et al 2016). It has been shown that latent heating can significantly influence the evolution and deepening of some of the most damaging storms (e.g., Ulbrich et al 2001;Liberato et al 2011) and has been shown to influence frontal structure and propagation around ETCs (see Posselt and Martin 2004;Reeves and Lackmann 2004).…”

“…Cyclonic PV anomalies below the heating maxima can act to enhance the low level circulation (Plant et al 2003) and strengthen flow in and downstream of the warm conveyor belt (WCB, Grams et al 2011), a band of ascending moist air responsible for much precipitation in ETCs. Anticyclonic PV generation above the heating maxima can help to slow the movement of the upper level PV maxima (the trough), thus maintaining the vertical tilt of the ETC (Stoelinga 1996), and can also enhance downstream ridging (Davis et al 1993). Capturing both the location and magnitude of diabatic processes is therefore necessary to realistically reproduce the evolution of the flow around ETCs and their consequent interaction with the background environment and flow (Pomroy and Thorpe 2000;Massacand et al 2001;Dirren et al 2003;Methven 2013).…”

Quantifying the climatological relationship between extratropical cyclone intensity and atmospheric precursors

“…These errors may be due to errors in the storms' vertical potential vorticity (PV) structure. For example, Stoelinga [1996] showed in his case study that latent heating was responsible for creating a significant positive PV anomaly above the surface warm front. This PV anomaly enhanced the eastward propagation of the surface wave and slowed the propagation of the upper-level wave thus keeping the upper-level PV wave coupled to the low-level surface wave.…”

The use of potential vorticity inversion to evaluate the effect of precipitation on downstream mesoscale processes

“…As documented in Hoskins et al (1985), Hertenstein and Schubert (1991), Fritsch et al (1994), Ritchie and Holland (1997), and Rogers and Fritsch (2001), there is a large amount of variability in the efficiency with which PV will be generated diabatically, corresponding to the magnitude and type (stratiform or convective) of diabatic heating, the vertical and horizontal distribution of the heating, the persistence of the heating, the amount of ambient absolute vorticity, and the environment in which the heating takes place. PV anomalies associated with diabatic heating have been shown to have an important impact upon cyclogenesis (Davis and Emanuel, 1991;Stoelinga, 1996;Posselt and Martin, 2004;Moore et al, 2008), and an influence on the distribution of precipitation associated with a midlatitude cyclone. Lackmann (2002) used a quasi-geostrophic PV inversion to show that a diabatically produced PV anomaly was associated with an enhanced low-level jet ahead of the cold front.…”