Midlevel Cyclonic Vortices Generated by Mesoseale Convective Systems

Bartels, Diana L.; Maddox, Robert A.

doi:10.1175/1520-0493(1991)119<0104:mcvgbm>2.0.co;2

Cited by 145 publications

(132 citation statements)

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“…This PV maximum is similar to the mid-troposphere vortex generated by MCSs (see e.g. Bartels and Maddox 1991, Chen and Frank 1993, Fritsch et al 1994, Houze 2004. The composite horizontal wind structures, however, reveal that the extreme rainfall composites in the Australian tropics are similar MCSs, whereas in the north African tropics, they are similar to the easterly waves.…”

Section: Discussionmentioning

confidence: 53%

Coherent Potential Vorticity Maxima and Their Relationship to Extreme Summer Rainfall in the Australian and North African Tropics

Hoang¹,

Reeder²,

Berry

et al. 2017

JSHESS

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Extreme rainfall in the tropics is frequently linked with coherent synoptic-scale potential vorticity (PV) disturbances. Here, an objective technique is used to identify coherent synoptic-scale cyclonic PV maxima with a focus on those that occur during summer over the African and Australian tropics. These two regions are chosen for comparison because of their geographical and climatological similarities. In particular, in both regions oceans lie equatorward and extensive deserts lie poleward, a juxtaposition that produces a reversal in the mean north-south temperature gradient and, through thermal wind, a low level easterly jet.In general, in the lower troposphere there are more coherent PV maxima in the tropics in the summer hemisphere than the winter hemisphere. These coherent PV maxima generally move with the background flow in the lower troposphere. The largest meridional flux of coherent PV maxima lies along eastern Australia with about half of the coherent PV maxima generated through the filamentaton and eventual isolation of midlatitude PV. In contrast, in the north African tropics, coherent PV maxima are generated mostly in the tropics and move westward through the west African monsoon region.Composites based on the extreme rainfall days for two regions are broadly similar with large, statistically significant PV maxima to the east of the maximum positive rainfall anomalies. The vertical structures of the PV fields in the two regions reveal a cyclonic PV maximum in the mid-troposphere collocated with the maximum of diabatic heating. The composite horizontal wind structures in the Australian tropics show structures similar to mesoscale convective systems (MCSs), whereas in the African tropics, they are similar to easterly waves.

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Section: Discussionmentioning

confidence: 53%

Coherent Potential Vorticity Maxima and Their Relationship to Extreme Summer Rainfall in the Australian and North African Tropics

Hoang¹,

Reeder²,

Berry

et al. 2017

JSHESS

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“…14b) appears to be a result of Ekman pumping, with frictionally induced convergence within the boundary layer and divergence immediately above the boundary layer. Midlevel convergence was collocated with the midlevel vorticity feature to the south, typical of a mesoscale convective vortex (MCV; Raymond and Jiang 1990;Bartels and Maddox 1991;Houze 2004). In addition, there was a positive temperature anomaly in the SAMURAI analysis above 6.5-km height over a negative low-level temperature anomaly (not shown), which is also characteristic of the thermal structure of a balanced midlevel vortex (Chen and Frank 1993).…”

Section: Mesoscale Analysis Of In Situ Observationsmentioning

confidence: 99%

Observations of a Nondeveloping Tropical Disturbance in the Western North Pacific during TCS-08 (2008)

Penny

Harr

Bell

2015

Monthly Weather Review

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Large uncertainty still remains in determining whether a tropical cloud cluster will develop into a tropical cyclone. During The Observing System Research and Predictability Experiment (THORPEX) Pacific Asian Regional Campaign (T-PARC)/Tropical Cyclone Structure-2008 (TCS-08) field experiment, over 50 tropical cloud clusters were monitored for development, but only 4 developed into a tropical cyclone. One nondeveloping tropical disturbance (TCS025) was closely observed for potential formation during five aircraft research missions, which provided an unprecedented set of observations pertaining to the large-scale and convective environments of a nondeveloping system. The TCS025 disturbance was comprised of episodic convection that occurred in relation to the diurnal cycle along the eastern extent of a broad low-level trough. The upper-level environment was dominated by two cyclonic cells in the tropical upper-tropospheric trough (TUTT) north of the low-level trough in which the TCS025 circulation was embedded. An in-depth examination of in situ observations revealed that the nondeveloping circulation was asymmetric and vertically misaligned, which led to larger system-relative flow on the mesoscale. Persistent environmental vertical wind shear and horizontal shearing deformation near the circulation kept the system from becoming better organized and appears to have allowed low equivalent potential temperature (u e ) air originating from one of the TUTT cells to the north (upshear) to impact the thermodynamic environment of TCS025. This in turn weakened subsequent convection that might otherwise have improved alignment and contributed to the transition of TCS025 to a tropical cyclone.

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“…They suggested that an environment of weak middle level shear but stronger low level shear (as observed in MCV environments [Bartels and Maddox, 1991]) could support a mesoscale rotational circulation in an MCS. The postulated circulation consisted of a warm core vortex characterized by a positive potential vorticity anomaly (i.e., MCV) in middle levels beneath a negative potential vorticity anomaly at upper levels.…”

Section: Middle Level Mesoscale Vorticesmentioning

confidence: 99%

Mesoscale Convective Systems

Markowski

Richardson

2010

Mesoscale Meteorology in Midlatitudes

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[1] Mesoscale convective systems (MCSs) have regions of both convective and stratiform precipitation, and they develop mesoscale circulations as they mature. The upward motion takes the form of a deep-layer ascent drawn into the MCS in response to the latent heating and cooling in the convective region. The ascending layer overturns as it rises but overall retains a coherent layer structure. A middle level layer of inflow enters the stratiform region of the MCS from a direction determined by the large-scale flow and descends in response to diabatic cooling at middle-to-low levels. A middle level mesoscale convective vortex (MCV) develops in the stratiform region, prolongs the MCS, and may contribute to tropical cyclone development. The propagation of an MCS may have a discrete component but may further be influenced by waves and disturbances generated both in response to the MCS and external to the MCS. Waves of a larger scale may affect the propagation velocity by phase locking with the MCS in a cooperative mode. The horizontal scale of an MCS may be limited either by a balance between the formation rate of convective precipitation and dissipation of stratiform precipitation or by the Rossby radius of the MCV. The vertical redistribution of momentum by an MCS depends on the size of the stratiform region, while the net vertical profile of heating of the largescale environment depends on the amount of stratiform rain. Regional variability of the stratiform rain from MCSs affects the large-scale circulation's response to MCS heating.

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Midlevel Cyclonic Vortices Generated by Mesoseale Convective Systems

Cited by 145 publications

References 0 publications

Coherent Potential Vorticity Maxima and Their Relationship to Extreme Summer Rainfall in the Australian and North African Tropics

Coherent Potential Vorticity Maxima and Their Relationship to Extreme Summer Rainfall in the Australian and North African Tropics

Observations of a Nondeveloping Tropical Disturbance in the Western North Pacific during TCS-08 (2008)

Mesoscale Convective Systems

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