Mesoscale Meteorology

Reeder, Michael J.; Smith, Roger K.

doi:10.1007/978-1-935704-10-2_8

Cited by 33 publications

(25 citation statements)

References 267 publications

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“…The second type of cold front in Australia is often preceded by a well-defined prefrontal trough. These systems are particularly common in summer when they are referred to as ''cool changes'' (Reeder and Smith 1998), but are less common in the growing season. However, early autumn and late spring are occasionally associated with this type of system, as well.…”

Section: Methodsmentioning

confidence: 99%

The Synoptic Climatology of Cool-Season Rainfall in the Central Wheatbelt of Western Australia

Pook

Risbey

McIntosh

2012

Monthly Weather Review

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Synoptic weather systems form an important part of the physical link between remote large-scale climate drivers and regional rainfall. A synoptic climatology of daily rainfall events is developed for the Central Wheatbelt of southwestern Australia over the April-October growing season for the years 1965-2009. The climatology reveals that frontal systems contribute approximately one-half of the rainfall in the growing season while cutoff lows contribute about a third. The ratio of frontal rainfall to cutoff rainfall varies throughout the growing season. Cutoff lows contribute over 40% of rainfall in the austral autumn and spring, but this falls to about 20% in August when frontal rainfall climbs to more than 60%. The number of cutoff lows varies markedly from one growing season to another, but does not exhibit a significant long-term trend. The mean rainfall per cutoff system is also highly variable, but has gradually declined over the analysis period, particularly in the past decade. The decline in rainfall per frontal system is less significant. Cutoff low rainfall has contributed more strongly in percentage terms to the recent decline in rainfall in the Central Wheatbelt than the frontal component and accounts for more than half of the overall trend. Atmospheric blocking is highly correlated with rainfall in the region where cutoff low rainfall makes its highest proportional contribution. Hence, the decline in rain from cutoff low systems is likely to have been associated with changes in blocking and the factors controlling blocking in the region.

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Section: Methodsmentioning

confidence: 99%

The Synoptic Climatology of Cool-Season Rainfall in the Central Wheatbelt of Western Australia

Pook

Risbey

McIntosh

2012

Monthly Weather Review

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“…Descriptions of these synoptic types can be found in Pook et al (2006), and an example of an autumn break event associated with a cutoff low (2 June 1981) is given in Figure 9. The significance of the cutoff low as a rainproducing system in the Australian context has been demonstrated by numerous authors (see, for example : Hill, 1969;Wright, 1989;Mills and Wu, 1995;Sturman and Tapper, 1996;Griffiths et al, 1998;Reeder and Smith, 1998; Qi et al, 1999;Pook et al, 2006). In the two years where the second criterion of the ideal break definition applied (viz.…”

Section: Synoptic Climatology Of Autumn Breaksmentioning

confidence: 98%

The autumn break for cropping in southeast Australia: trends, synoptic influences and impacts on wheat yield

Pook

Lisson

Risbey

et al. 2008

Intl Journal of Climatology

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ABSTRACT:The autumn break is the first significant rainfall event of the winter growing season. Two definitions of the autumn break have been developed for northwestern Victoria; a so-called ideal break and a minimum rainfall condition for sowing a wheat crop termed a minimal break. Application of the ideal break definition for an eight-station average reveals that 41 autumn breaks occurred in the first half of the record and 34 in the second half ) with a trend towards breaks occurring later in the season. In the decade to 2006, there have been only 3 ideal breaks (1999, 2000 and 2005) and none of the selected rainfall stations has recorded an 'extreme' wet autumn over the last 11 years, the longest period recorded for this criterion. A synoptic analysis for the period 1956-2006 has established that breaks are predominantly associated with systems known as cutoff lows. The influence of these systems has varied markedly throughout the analysis period and only one autumn break has been caused by a cutoff low in the final decade of the analysis. Additionally, the total rainfall associated with cutoff lows in the April to June period has declined significantly over the past 30 years.A farming system model has been employed to simulate a wheat crop in northwestern Victoria under historical conditions for a range of management options. Average yield across all years of the simulation declines with delay in the sowing date after late April, but there is a marked interannual variability in yield response to the sowing date which is related to rainfall distribution in the growing season in each year. The simulated in-crop rainfall indicates that the most recent drought in southeastern Australia is comparable in severity with the two major droughts in the 20th Century.

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“…During the dry season the clouds are mostly capped by the trade wind inversion at about 3 km, but during the moist season they may develop as lines of thunderstorms that pose a significant forecasting problem in the region. A recent review of the various cloud lines is given by Reeder and Smith (1998).…”

Section: Introductionmentioning

confidence: 99%

The Importance of the Boundary Layer Parameterization in the Prediction of Low-Level Convergence Lines

Thomsen¹,

Smith²

2008

Monthly Weather Review

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The importance of the boundary layer parameterization in the numerical prediction of low-level convergence lines over northeastern Australia is investigated. High-resolution simulations of convergence lines observed in one event during the 2002 Gulf Lines Experiment are carried out using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5). Calculations using five different parameterizations are compared with observations to determine the optimum scheme for capturing these lines. The schemes that give the best agreement with the observations are the three that include a representation of countergradient fluxes and a surface layer scheme based on MoninObukhov theory. One of these, the Medium-Range Forecast scheme, is slightly better than the other two, based on its ability to predict the surface pressure distribution. The findings are important for the design of mesoscale forecasting systems for the arid regions of Australia and elsewhere.

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Mesoscale Meteorology

Cited by 33 publications

References 267 publications

The Synoptic Climatology of Cool-Season Rainfall in the Central Wheatbelt of Western Australia

The Synoptic Climatology of Cool-Season Rainfall in the Central Wheatbelt of Western Australia

The autumn break for cropping in southeast Australia: trends, synoptic influences and impacts on wheat yield

The Importance of the Boundary Layer Parameterization in the Prediction of Low-Level Convergence Lines

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