Asymmetric Distribution of Convection Associated with Tropical Cyclones Making Landfall along the South China Coast

Chan, Johnny C. L.; Liu, K. S.; Ching, Simon E.; Lai, Edwin S. T.

doi:10.1175/1520-0493(2004)132<2410:adocaw>2.0.co;2

Cited by 84 publications

(64 citation statements)

References 17 publications

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“…Australian examples include the hazardous impacts from tropical cyclone Larry (2006) and tropical cyclone Yasi (2011) to the State of Queensland, and tropical cyclone landfalls were responsible for an average of four casualties per year during the 1960-1989 period (Ryan 1993). Knowledge of the region along the coast where the heaviest precipitation will be experienced is therefore crucial to reduce the losses (Chan et al 2004). However, the rainfall patterns in tropical cyclones are complex and vary from case to case (Lonfat et al 2007).…”

Section: Introductionsupporting

confidence: 87%

“…For the land-leaving tropical cyclone Billy, the rainfall maximum was located at its left side where the winds also went offshore. The observations for these five tropical cyclones in northwestern Australia are consistent with previous studies such as Chan et al (2004) and Liu et al (2007). By using satellite and radar data, Chan et al (2004) examined the landfalls of three typhoons on the south China coast, and identified enhanced convection to the western side of the tropical cyclones (i.e.…”

Section: General Considerationmentioning

confidence: 99%

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Rainfall distribution of five landfalling tropical cyclones in the northwestern Australian region

Li¹,

Cheung²,

Chan³

et al. 2013

AMOJ

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Rain gauge data, satellite IR brightness temperature and radar-estimated rain rate for five tropical cyclones from the 2005-06 to 2009-10 seasons that made landfall along the northwestern coast of Australia are analysed. It is the first time that the spatial rainfall distribution of landfalling tropical cyclones in the southern hemisphere has been systematically investigated. It is found that the distributions of rainfall are more concentrated in the right side of the track of the landfall tropical cyclones, which is the offshore flow position. Potential mechanisms responsible for this observed asymmetry in rainfall distribution are discussed. These include the tropical cyclone motion direction, deep-tropospheric vertical wind shear and land-sea contrast in surface properties. Topography is considered to have less effect since Western Australia is relatively flat. The rainfall maxima are found in the front and downshear quadrants for these tropical cyclones, which is consistent with previous studies. The changes in vertical wind shear when these tropical cyclones moved to the south are largely attributed to the prevailing environmental flow. Three numerical simulations are performed; one with a realistic land surface, one with all topography removed and one with all land removed. These simulations show that the land surface effects play an important role in determining the asymmetry in rainfall distribution, which explains why in some cases the observed maximum rainfall does not follow closely the vertical wind shear direction when making landfall.

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Section: Introductionsupporting

confidence: 87%

Section: General Considerationmentioning

confidence: 99%

Rainfall distribution of five landfalling tropical cyclones in the northwestern Australian region

Li¹,

Cheung²,

Chan³

et al. 2013

AMOJ

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“…Whether and by which means storms are detrimentally impacted by vertical shear on their periphery has not been well established. In most previous studies of vertical wind shear impacts on tropical cyclones, the ''detrimental'' shear was thought to be that existing over the core (the center and out to some specified radius) of the storm (Marks et al 1992;Franklin et al 1993;Reasor et al 2000;Black et al 2002;Corbosiero andMolinari 2002, 2003;Rogers et al 2003;Chan et al 2004;Braun et al 2006;Braun and Wu 2007;Chen et al 2006) and was often assumed to be horizontally uniform in modeling studies (Jones 1995;Frank andRitchie 1999, 2001;Wong and Chan 2004). For this study, we assume that the presence of an AEJ near the periphery of a storm is not necessarily detrimental to storm development.…”

Section: Vertical Shear and Increased Stabilitymentioning

confidence: 99%

Reevaluating the Role of the Saharan Air Layer in Atlantic Tropical Cyclogenesis and Evolution

Braun

2010

Monthly Weather Review

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The existence of the Saharan air layer (SAL), a layer of warm, dry, dusty air frequently present over the tropical Atlantic Ocean, has long been appreciated. The nature of its impacts on hurricanes remains unclear, with some researchers arguing that the SAL amplifies hurricane development and with others arguing that it inhibits it. The potential negative impacts of the SAL include 1) vertical wind shear associated with the African easterly jet; 2) warm air aloft, which increases thermodynamic stability at the base of the SAL; and 3) dry air, which produces cold downdrafts. Multiple NASA satellite datasets and NCEP global analyses are used to characterize the SAL's properties and evolution in relation to tropical cyclones and to evaluate these potential negative influences. The SAL is shown to occur in a large-scale environment that is already characteristically dry as a result of large-scale subsidence. Strong surface heating and deep dry convective mixing enhance the dryness at low levels (primarily below ;700 hPa), but moisten the air at midlevels. Therefore, mid-to-upper-level dryness is not generally a defining characteristic of the SAL, but is instead often a signature of subsidence. The results further show that storms generally form on the southern side of the jet, where the background cyclonic vorticity is high. Based upon its depiction in NCEP Global Forecast System meteorological analyses, the jet often helps to form the northern side of the storms and is present to equal extents for both strengthening and weakening storms, suggesting that jet-induced vertical wind shear may not be a frequent negative influence. Warm SAL air is confined to regions north of the jet and generally does not impact the tropical cyclone precipitation south of the jet.Composite analyses of the early stages of tropical cyclones occurring in association with the SAL support the inferences from the individual cases noted above. Furthermore, separate composites for strongly strengthening and for weakening storms show few substantial differences in the SAL characteristics between these two groups, suggesting that the SAL is not a determinant of whether a storm will intensify or weaken in the days after formation. Key differences between these cases are found mainly at upper levels where the flow over strengthening storms allows for an expansive outflow and produces little vertical shear, while for weakening storms, the shear is stronger and the outflow is significantly constrained.

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“…Before the skill of dynamical models is improved to an acceptable level for operational applications, forecasters usually rely on various statistical models for rainfall estimation and issuing warnings. The fact that the distributions of convection and rainfall in TCs have certain characteristic patterns both when they are over open oceans (Lonfat et al, 2004) and when making landfall (Chan et al, 2004) allows the application of statistical descriptions and predictions based on climatology. For instance, Lonfat et al (2004) found from microwave imageries that generally the maximum rainfall of a TC is located in the front quadrants (relative to storm motion), and this location shifts from the front-left quadrant for weaker TCs to the front-right quadrant for stronger TCs.…”

Section: K K W Cheung Et Al: Tropical Cyclone Rainfall Characterimentioning

confidence: 99%

“…For instance, Lonfat et al (2004) found from microwave imageries that generally the maximum rainfall of a TC is located in the front quadrants (relative to storm motion), and this location shifts from the front-left quadrant for weaker TCs to the front-right quadrant for stronger TCs. Based on satellite and radar observations of four TCs that made landfall along the south China coast in 1999, Chan et al (2004) also found that stronger convection generally appeared in the front and then the left quadrant of a TC but vertical wind shear might influence the distribution of convection (Corbosiero and Molinari, 2002). The purpose of this study is to provide a detailed statistical analysis of the characteristics of TC-related rainfall in the Taiwan area and illustrate the skill level of a simple climatology-based statistical model for TC rainfall prediction.…”

Section: K K W Cheung Et Al: Tropical Cyclone Rainfall Characterimentioning

confidence: 99%

Characteristics of rainfall during tropical cyclone periods in Taiwan

Cheung

Huang

Lee

2008

Nat. Hazards Earth Syst. Sci.

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Abstract. Due to the Central Mountain Range with an elevation up to about 4 km, the amount and distribution of rainfall in Taiwan associated with typhoons or tropical cyclones (TCs) depends not only on the distribution of convection within the TCs (internal structure) and influences from monsoon-scale environmental flow, but also on the orographic effect. This study analyzes the spatial and temporal characteristics of rainfall associated with 62 TC cases that affected Taiwan by using observations from the 371 automatic rain stations available in the period 1989-2002. It is found from the climatology maps that highly different rainfall distributions occurred for TCs that approached the Taiwan area from different directions. By performing objective clustering analysis of the rainfall time series of all the rain gauges, several characteristic temporal rainfall profiles are obtained. The geographic distribution of rain gauges that possess a particular temporal profile is also consistent with the possible TC track types that bring maximum rain to the Taiwan area at different times.Based on data in the 1989-2002 period, the development of a TC rainfall climatology-persistence (CLIPER) model is described. CLIPER is an optimized combination of climatology and persistence with different relative weighting for different forecast periods. Independent cases (other than the model development database) during 2003-2004 are used to validate the model. Objective measures like equitable threat score and bias score show that CLIPER's skill is acceptable for practical applications for 24-h rain threshold below 100 mm. However, the underestimation bias for more heavy rainfall is serious and CLIPER seems to have better performance for the northwestern Taiwan than for the other locations. Future directions for improvement of the CLIPER model are discussed.

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Asymmetric Distribution of Convection Associated with Tropical Cyclones Making Landfall along the South China Coast

Cited by 84 publications

References 17 publications

Rainfall distribution of five landfalling tropical cyclones in the northwestern Australian region

Rainfall distribution of five landfalling tropical cyclones in the northwestern Australian region

Reevaluating the Role of the Saharan Air Layer in Atlantic Tropical Cyclogenesis and Evolution

Characteristics of rainfall during tropical cyclone periods in Taiwan

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