The Vorticity Budgets of North Atlantic Winter Extratropical Cyclone Life Cycles in MERRA Reanalysis. Part I: Development Phase*

Azad, Roohollah; Sorteberg, Asgeir

doi:10.1175/jas-d-13-0267.1

Cited by 19 publications

(20 citation statements)

References 43 publications

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“…On the basis of the information of timing and position of low-pressure centers, we make composites of different parameters. The composite methodology consists of centering a radial coordinate system on the center of the low and rotating it in the propagation direction [Bengtsson et al, 2007;Azad and Sorteberg, 2014; SS2015a]. The Journal of Geophysical Research: Atmospheres 10.1002/2015JD024658 composites have a radius of 5°, which we will call the cyclone-related area.…”

Section: Analysis Methodsmentioning

confidence: 99%

Precipitation response of monsoon low‐pressure systems to an idealized uniform temperature increase

et al. 2016

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The monsoon low-pressure systems (LPSs) are one of the most rain-bearing synoptic-scale systems developing during the Indian monsoon. We have performed high-resolution, convection-permitting experiments of 10 LPS cases with the Weather Research and Forecasting regional model, to investigate the effect of an idealized uniform temperature increase on the LPS intensification and precipitation. Perturbed runs follow a surrogate climate change approach, in which a uniform temperature perturbation is specified, but the large-scale flow and relative humidity are unchanged. The differences between control and perturbed simulations are therefore mainly due to the imposed warming and moisture changes and their feedbacks to the synoptic-scale flow. Results show that the LPS precipitation increases by 13%/K, twice the imposed moisture increase, which is on the same order as the Clausius-Clapeyron relation. This large precipitation increase is attributed to the feedbacks in vertical velocity and atmospheric stability, which together account for the high sensitivity. In the perturbed simulations the LPSs have higher propagation speeds and are more intense. The storms intensification to the uniform temperature perturbation can be interpreted in terms of the conditional instability of second kind mechanism where the condensational heating increases along with low-level convergence and vertical velocity in response to temperature and moisture increases. As a result, the surface low deepens.

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Section: Analysis Methodsmentioning

confidence: 99%

Precipitation response of monsoon low‐pressure systems to an idealized uniform temperature increase

et al. 2016

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“…Because SLP was not a direct result from the PPVI analysis, the 900-hPa (above the terrain of the Japanese archipelago) geopotential height was used as an alternative (Azad & Sorteberg, 2014). Because SLP was not a direct result from the PPVI analysis, the 900-hPa (above the terrain of the Japanese archipelago) geopotential height was used as an alternative (Azad & Sorteberg, 2014).…”

Section: Representative Factor and Key Region For The Eecmentioning

confidence: 99%

“…As described in section 2.3.2, PPVI analysis was used to investigate the deepening of Cyclone A. Because SLP was not a direct result from the PPVI analysis, the 900-hPa (above the terrain of the Japanese archipelago) geopotential height was used as an alternative (Azad & Sorteberg, 2014). During the maximum development…”

Section: Representative Factor and Key Region For The Eecmentioning

confidence: 99%

Investigating the Mechanisms Associated With the Evolutions of Twin Extratropical Cyclones Over the Northwest Pacific Ocean in Mid‐January 2011

Sun

et al. 2018

JGR Atmospheres

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Twin extratropical cyclones that appeared over the northwest Pacific Ocean in mid‐January 2011 experienced significantly different transitions: the northern cyclone dissipated rapidly, whereas the southern cyclone developed into an extreme example of an explosive (i.e., rapidly deepening) extratropical cyclone. This event was reasonably reproduced by the fifth‐generation Mesoscale Model, and its associated mechanisms were investigated using piecewise potential vorticity inversion and the Zwack‐Okossi vorticity budget. Main results are as follows. (i) The extratropical cyclone‐included twin cyclone event showed a Fujiwhara effect, during which the two cyclones orbited cyclonically about a midpoint, approached each other, and finally merged. The twin cyclone interactions enhanced the northern cyclone, but weakened the southern cyclone, by inducing warm advection and cold advection, respectively. (ii) Although upper level tropopause folding contributed the most to deepening of the twin cyclones, significant differences in their deepening rates were due predominantly to the contrast between lower level temperature advection and precipitation‐related latent heating. (iii) Stronger upper tropospheric positive absolute‐vorticity advection and warm advection associated with an upper level jet, and larger latent heating, made geostrophic vorticity of the southern cyclone increase more rapidly than that of the northern cyclone. (iv) Explosive deepening of the southern cyclone showed insensitive responses to its relative configuration with the upper level jet, whereas its rotation enhancement was faster when the cyclone was embedded within the upper level jet. (v) The upper level forcing had a greater influence on the large‐scale flow associated with the twin cyclones, whereas the middle‐level and lower level forcings were more dominant close to the cyclone core regions.

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“…The vorticity equation has also been extensively used in previous investigations of extratropical cyclones (e.g. Lupo et al , 1992; Grotjahn, 1996; Azad and Sorteberg, 2014a, 2014b), tropical cyclones (e.g. Karyampudi and Pierce, 2002; Raymond and López Carrillo, 2011) and even hurricanes that underwent extratropical transition (e.g.…”

Section: Introductionmentioning

confidence: 99%

Structure and evolution of subtropical cyclone Anita as evaluated by heat and vorticity budgets

Dutra

Rocha

Lee

et al. 2017

Quart J Royal Meteoro Soc

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This article explores the evolution of subtropical cyclone Anita, which occurred near the east coast of Brazil (∼19°S–37°W) in March 2010. Thermodynamic and dynamic processes during Anita's life cycle are investigated using the heat and vorticity budget equations. The cyclone developed with hybrid characteristics and moved anomalously to the southwest, where it coupled with an upper‐level cut‐off low during the mature phase. This coupling was the main dynamical mechanism for further cyclone deepening. Anita then remained quasi‐stationary at about 30°S–47°W for 2 days, due to an upper‐level dipole pattern, which prevented earlier displacement of the upper‐level low counterpart. When the dipole pattern dissipated, the cyclone moved southeast and underwent extratropical transition whilst merging with a midlatitude frontal cyclone. Diabatic heating and horizontal temperature advection are found to be essential for subtropical development. During extratropical transition, instead it is diabatic cooling together with adiabatic cooling and warm‐air advection that act as the main mechanisms to influence the local temperature tendencies at low levels. Low‐level cyclonic tendencies were mostly due to convergent flow and the residual vorticity partially destroyed the vorticity tendencies produced by the divergence term. Moreover, in regions and levels where convection could explain some of the vorticity tendencies, it is found that apparent sinks of cyclonic vorticity were related to negative vorticity due to divergence (i.e. convergent flow), whilst apparent sources were related to positive vorticity due to divergence (i.e. divergent flow).

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The Vorticity Budgets of North Atlantic Winter Extratropical Cyclone Life Cycles in MERRA Reanalysis. Part I: Development Phase*

Cited by 19 publications

References 43 publications

Precipitation response of monsoon low‐pressure systems to an idealized uniform temperature increase

Precipitation response of monsoon low‐pressure systems to an idealized uniform temperature increase

Investigating the Mechanisms Associated With the Evolutions of Twin Extratropical Cyclones Over the Northwest Pacific Ocean in Mid‐January 2011

Structure and evolution of subtropical cyclone Anita as evaluated by heat and vorticity budgets

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