A new perspective of the climatological features of upper-level cut-off lows in the Southern Hemisphere

Pinheiro, Henri Rossi; Hodges, Kevin I.; Gan, Manoel Alonso; Ferreira, Nelson Jesus

doi:10.1007/s00382-016-3093-8

Cited by 40 publications

(61 citation statements)

References 49 publications

(57 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The synoptic pattern for the 19 August 2014 storm is similar to the 24 July 1990 storm documented by McCollum et al (). Previous studies highlight the role of cut‐off lows in producing extreme rainfall and flooding (e.g., Awan & Formayer, ; Knippertz & Martin, ; Marquardt Collow et al, ; Pinheiro et al, ). At 0600 UTC on 19 August, a strong upper‐level trough extended from −130°E to −110°E longitude at 500 hPa and extended toward 30°N latitude, with the 5,820 m contour cut‐off from the main circulation (Figure a).…”

Section: Overview Of the 19 August 2014 Stormmentioning

confidence: 99%

Sensitivity of Extreme Rainfall to Atmospheric Moisture Content in the Arid/Semiarid Southwestern United States: Implications for Probable Maximum Precipitation Estimates

Yang

Smith

2018

JGR Atmospheres

View full text Add to dashboard Cite

Sensitivity of extreme rainfall to atmospheric moisture content for the 19 August 2014 storm in Arizona is investigated based on numerical experiments using the Weather Research and Forecasting model. Analyses are designed to develop an improved understanding of the roles of atmospheric moisture content and complex terrain in controlling spatial and temporal variability of extreme rainfall in the arid/semiarid southwestern United States. The control simulation identifies complex interactions of low‐level moisture transport and orographic lift as key elements in producing extreme rainfall for the first storm episode. Two sensitivity experiments are performed by increasing the relative humidity by 10% and 20% in both initial and boundary conditions used for the control simulation. Changes in atmospheric moisture content modify the storm structure and evolution, instability of the storm environment, and interactions of synoptic flow with complex terrain. The two storm episodes within this event exhibit contrasting responses to the increase of moisture content, with rainfall accumulation and maximum convective available potential energy increased for the second storm episode as opposed to a more complex relationship for the first storm episode. A moisture maximization simulation was also designed to mimic the framework of moisture maximization in probable maximum precipitation estimates. Our results highlight the nonlinear relationship between extreme rainfall and atmospheric moisture content in complex environments where small‐scale convection plays a dominant role. Limitations of probable maximum precipitation estimates based physical models are also discussed.

show abstract

Section: Overview Of the 19 August 2014 Stormmentioning

confidence: 99%

Sensitivity of Extreme Rainfall to Atmospheric Moisture Content in the Arid/Semiarid Southwestern United States: Implications for Probable Maximum Precipitation Estimates

Yang

Smith

2018

JGR Atmospheres

View full text Add to dashboard Cite

show abstract

“…In the Northern Hemisphere, cut-off lows tend to occur over southern Europe and the eastern Atlantic coast, the China-Siberia region, the eastern North Pacific Ocean, and western North America (e.g., Bell and Bosart 1989;Price and Vaughan 1992;Kentarchos and Davies 1998;Nieto et al 2005). On the other hand, Southern Hemisphere cut-off lows are most frequent around the continental landmasses but especially over southeast Australia-New Zealand, southern South America, and southern Africa (e.g., Fuenzalida et al 2005;Reboita et al 2010;Favre et al 2012;Pinheiro et al 2017).…”

Section: Introductionmentioning

confidence: 99%

A Midlatitude Climatology and Interannual Variability of 200- and 500-hPa Cut-Off Lows

2020

View full text Add to dashboard Cite

A climatology of midlatitude 200- and 500-hPa cut-off low systems in the Northern and Southern Hemispheres is constructed from the NCEP–NCAR reanalysis by detecting and tracking, under one consistent method, all of the systems that persisted for more than 36 h for the 58 years of 1960–2017. This method identifies a cut-off low as a cold-core geopotential height minimum that is isolated from the main westerlies and with a strong temperature gradient on its eastern flank. The obtained spatial and seasonal distributions show preferred regions of occurrence and that within these regions there is a level-dependent seasonality of cut-off lows. Whereas 200-hPa systems are more frequent in summer and autumn, 500-hPa systems are more evenly distributed throughout the seasons. Within each region and at each level, the annual number of cut-off lows has been increasing over time, trends that are consistent with documented signals of climate change such as a weakening and poleward shift of the subtropical jets and an increase in blocking frequency. These trends explain as much as 64% of the variance in the annual number of cut-off lows. The contribution of the annular modes and El Niño–Southern Oscillation to the interannual variability of the number of cut-off lows per season in each hemisphere is also investigated. Only the Northern Hemisphere annular mode has a statistically significant negative correlation throughout all seasons that explains 18%–45% of the variance in the yearly number of Northern Hemisphere 500-hPa cut-off lows.

show abstract

“…This criterion has precedents in, for example, Pinheiro et al . (). Even so, and in order to test the threshold sensitivity, the TRACK algorithm was run at 500 hPa, with a set of more restrictive RV threshold values.…”

Section: Methodsmentioning

confidence: 97%

“…This algorithm has been used in numerous studies to track cyclones at a single pressure level not only near sea‐level but also in the upper troposphere (e.g. Hoskins and Hodges, ; ; Mailier et al ., ; Froude et al, ; Catto et al, ; Serra et al, ; Dacre et al, ; Zappa et al, ; 2014; Pinheiro et al, ) and its implementation is well documented. Grieger et al .…”

Section: Methodsmentioning

confidence: 99%

“…The first two density areas are in agreement with cut‐off low (COL) occurrence in Pinheiro et al . (). However, as the authors note, the cyclone centres detected by TRACK in the upper troposphere may include pressure troughs as well as closed circulation systems at upper‐tropospheric pressure levels, and hence further criteria need to be applied to confirm the occurrence of COLs.…”

Section: Validation Studiesmentioning

confidence: 97%

See 1 more Smart Citation

A 4D feature‐tracking algorithm: A multidimensional view of cyclone systems

Lakkis

Canziani

Yuchechen

et al. 2019

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

An objective four-dimensional (4D) algorithm developed to track extratropical relative vorticity anomaly 3D structure over time is introduced and validated. The STACKER algorithm, structured with the TRACKER single-level tracking algorithm as source of the single-level raw tracks, objectively combines tracks from various levels to determine the 3D structure of the cyclone (or anticyclone) events throughout their life cycle. STACKER works progressively, beginning with two initial levels and then adding additional levels to the stack in a bottom-up and/or top-down approach. This allows an iterative stacking approach, adding one level at a time, resulting in an optimized 4D determination of relative vorticity anomaly events. A two-stage validation process is carried out with the ECMWF reanalysis ERA-Interim dataset for the 2015 austral winter. First the overall tracking capability during an austral winter, taking into account a set of climate indicators and their impacts on Southern Hemisphere circulation, was compared to previous climatologies, in order to verify the density and distribution of the cyclone events detected by STACKER. Results show the cyclone density distribution is in very good agreement with previous climatologies, after taking into account potential differences due to climate variability and different tracking methodologies. The second stage focuses on three different long-lived events over the Southern Hemisphere during the winter of 2015, spanning seven different pressure levels. Both GOES satellite imagery, infrared and water vapour channels, and ERA-Interim cloud cover products are used in order to validate the tracks obtained as well as the algorithm's capability and reliability. The observed 3D cyclone structures and their time evolution are consistent with current understanding of cyclone system development. Thus, the two-stage validation confirms that the algorithm is suitable to track multilevel events, and can follow and analyse their 3D life cycle and develop full 3D climatologies and climate variability studies.

show abstract

A new perspective of the climatological features of upper-level cut-off lows in the Southern Hemisphere

Cited by 40 publications

References 49 publications

Sensitivity of Extreme Rainfall to Atmospheric Moisture Content in the Arid/Semiarid Southwestern United States: Implications for Probable Maximum Precipitation Estimates

Sensitivity of Extreme Rainfall to Atmospheric Moisture Content in the Arid/Semiarid Southwestern United States: Implications for Probable Maximum Precipitation Estimates

A Midlatitude Climatology and Interannual Variability of 200- and 500-hPa Cut-Off Lows

A 4D feature‐tracking algorithm: A multidimensional view of cyclone systems

Contact Info

Product

Resources

About