Downstream baroclinic development among forty‐one cold‐season Eastern North Pacific cyclones

Danielson, Richard E.; Gyakum, John R.; Straub, David

doi:10.3137/ao.420402

Cited by 12 publications

(6 citation statements)

References 41 publications

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“…Moreover, the use of the algorithm facilitates using a larger number of systems for the compositing in comparison to manual procedures used to create composites, for example, in Danielson et al . (2004) and Gan and Dal Piva (2016). For a regional analysis, the main genesis areas are identified and the tracks that have their genesis over a spherical region (radius = 10°) centred on the maxima genesis are selected.…”

Section: Methodsmentioning

confidence: 99%

“…Orlanski and Sheldon (1995) observed that cyclone waves grow initially due to the upstream energy source and later because of the baroclinic conversion (EKE growing with ascent in the warm air and descent in the cold air) referred to as downstream baroclinic development. Motivated by this context, other authors have made use of the concept of downstream energy dispersion to provide a dynamical interpretation of the baroclinic disturbances based on observations (Chang, 1993; 2000; Danielson et al ., 2004; 2006; Decker and Martin, 2005; Dal Piva et al ., 2010; Rivière et al ., 2015) or model simulations (Simmons and Hoskins, 1979; Orlanski and Chang, 1993; Papritz and Schemm, 2013; Schemm et al ., 2013).…”

Section: Introductionmentioning

confidence: 99%

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Contributions of downstream baroclinic development to strong Southern Hemisphere cut‐off lows

Pinheiro

Hodges

Gan

et al. 2021

Quart J Royal Meteoro Soc

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Cut‐Off Lows (COLs) in the Southern Hemisphere and the mechanisms involved in their development are investigated in detail using the eddy kinetic energy (EKE) budget applied to data from the ERA‐Interim reanalysis. This approach considers the most important processes that are typical for the evolution of midlatitude disturbances such as the baroclinic (BRC) and barotropic (BRT) conversions, and the ageostrophic flux convergence (AFC), known as downstream development. Composites of the volume‐integrated EKE and its components are evaluated based on the 200 most intense SH COLs (>98th percentile) observed in a 36‐year period. Results show that the AFC together with the BRC conversion are the most important contributors to the EKE growth for the COLs, characterizing the downstream baroclinic development. The AFC plays an important role in genesis and intensification phases of the COLs, while the BRC conversion is important for the system maintenance. The dissipation of the COLs occurs due to dispersive fluxes (ageostrophic flux divergence) together with other processes not directly computed in the EKE equation, such as friction and latent heat release which are problematic in reanalysis datasets. The BRT conversion contributes negatively to the COL development by transferring EKE to the zonal flow kinetic energy, though this is not enough to dampen the intensification. Regional differences were found in the energetics, indicating that COLs originating upstream of the continents are clearly dominated by ageostrophic fluxes, while the systems over the Australian region are mostly driven by baroclinic processes.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Contributions of downstream baroclinic development to strong Southern Hemisphere cut‐off lows

Pinheiro

Hodges

Gan

et al. 2021

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

show abstract

“…Previous studies employing the K e framework (e.g., Danielson et al 2004;Decker and Martin 2005;Harr and Dea 2009;Cordeira and Bosart 2010) are based on analysis data, available at 10 and more pressure levels (referred to as vertical output resolution in the remainder). However, data from the operational ECMWF EPS is only available at nine pressure levels.…”

Section: A Datamentioning

confidence: 99%

An Eddy Kinetic Energy View of Physical and Dynamical Processes in Distinct Forecast Scenarios for the Extratropical Transition of Two Tropical Cyclones*

Keller

Jones

Harr

2014

Monthly Weather Review

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The extratropical transition (ET) of Hurricane Hanna (2008) and Typhoon Choi-Wan (2009) caused a variety of forecast scenarios in the European Centre for Medium-Range Weather Forecasts (ECMWF) Ensemble Prediction System (EPS). The dominant development scenarios are extracted for two ensemble forecasts initialized prior to the ET of those tropical storms, using an EOF and fuzzy clustering analysis. The role of the transitioning tropical cyclone and its impact on the midlatitude flow in the distinct forecast scenarios is examined by conducting an analysis of the eddy kinetic energy budget in the framework of downstream baroclinic development. This budget highlights sources and sinks of eddy kinetic energy emanating from the transitioning tropical cyclone or adjacent upstream midlatitude flow features. By comparing the budget for several forecast scenarios for the ET of each of the two tropical cyclones, the role of the transitioning storms on the development in downstream regions is investigated. Distinct features during the interaction between the tropical cyclone and the midlatitude flow turned out to be important. In the case of Hurricane Hanna, the duration of baroclinic conversion from eddy available potential into eddy kinetic energy was important for the amplification of the midlatitude wave pattern and the subsequent reintensification of Hanna as an extratropical cyclone. In the case of Typhoon Choi-Wan, the phasing between the storm and the midlatitude flow was one of the most critical factors for the future development.

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“…In nature, individual storms tend to develop just downstream and slightly poleward of the maximum baroclinicity that may be quite localized, as discussed in . Frequently, downstream baroclinic development occurs resulting in a wavetrain along the major storm tracks (Danielson et al, 2004, and references therein). Since climatological basic states are averages of many instantaneous flow fields the local variations in baroclinicity are generally less than for instantaneous basic states.…”

Section: Structures Of Southern Hemisphere Cyclogenesis Modesmentioning

confidence: 99%

Interdecadal changes in southern hemisphere winter storm track modes

Frederiksen

2007

Tellus A: Dynamic Meteorology and Oceanography

108

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A B S T R A C TThe interdecadal changes in southern hemisphere (SH) winter cyclogenesis have been studied using a global twolevel primitive equation instability-model with reanalysed observed July three-dimensional basic states for the periods 1949-1968 and 1975-1994. The early to mid-1970s were a time of quite dramatic reduction in the winter rainfall in the southwest of western Australia (SWWA). We find that the rainfall reduction is associated with a decrease in the vertical mean meridional temperature gradient and in the peak upper tropospheric jet-stream zonal winds near 30 • south throughout most of the SH. These changes are reflected in the properties of the leading SH cyclogenesis modes: for 1975-1994 both the fastest growing mode, and on average the 10 leading SH cyclogenesis modes that cross Australia, have growth rates which are around 30% smaller than for the corresponding modes for 1949-1968. The sensitivity of our results, to the strengths of physical parametrizations and to the choice of basic states based on different data sets, is examined.Our results suggest that a primary cause of the rainfall reduction over SWWA in the period after 1975 is the reduction of the intensity of cyclogenesis and the southward deflection of some storms.

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Downstream baroclinic development among forty‐one cold‐season Eastern North Pacific cyclones

Abstract: A quantification of local energy propagation is employed to distinguish cases of downstream baroclinic development, as described by Orlanski and Sheldon (1995)

Cited by 12 publications

References 41 publications

Contributions of downstream baroclinic development to strong Southern Hemisphere cut‐off lows

Contributions of downstream baroclinic development to strong Southern Hemisphere cut‐off lows

An Eddy Kinetic Energy View of Physical and Dynamical Processes in Distinct Forecast Scenarios for the Extratropical Transition of Two Tropical Cyclones*

Interdecadal changes in southern hemisphere winter storm track modes

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