A global evaluation of fronts and precipitation in the ACCESS model

Catto, Jennifer L.; Jakob, Christian; Nicholls, Neville

doi:10.22499/2.6301.012

Cited by 38 publications

(38 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Catto et al (2013) found that although rainfall associated with fronts was underestimated, the major precipitation errors were associated with non -frontal rainfall, which might derive from systems such as cutoff lows. Since cutoff lows are important for rainfall across southern Australia, and their decline in number have contributed to the autumn rainfall reduction in the southeast , the poor representation of cutoffs in models (Grose et al, 2012) might explain that, even if the observed autumn rainfall decline is a forced signal and not simply driven by natural variabil ity, models are less likely to capture it.…”

Section: Discussion and Synthesismentioning

confidence: 96%

“…Frontal systems are very important for rainfall in southern Australia (Berry et al, 2011;Simmonds et al, 2012) particularly in the southeast in autumn (Catto et al, 2012) and the southwest in winter, where they have been found to be declining in number (Hope et al, 2014). Fronts in an example GCM, ACCESS1.3, tend to be well represented in their frequency and the proportion of precipitation associated with them (Catto et al, 2013), although the intensity of that precipitation is underestimated. Frontal systems tend to intensify via a confluence of subtropical and polar jets, and thus the observed and projected large-scale meridional shifts in pressure and the polar jet align with a reduction in the number of fronts impacting upon southern Australia Hope, 2006).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Seasonal and regional signature of the projected southern Australian rainfall reduction

Hope¹,

Grose²,

Timbal³

et al. 2015

AMOJ

View full text Add to dashboard Cite

A projected drying of the extra-tropics under enhanced levels of atmospheric greenhouse gases has large implications for natural systems and water security across southern Australia. The drying is driven by well studied changes to the atmospheric circulation and is consistent across climate models, providing a strong basis from which adaptation planners can make decisions. However, the magnitude and seasonal expression of the drying is expected to vary across the region. Here we describe the spatial signature of the projected change from the new CMIP5 climate models and downscaling of those models, and review various lines of evidence about the seasonal expression.Winter rainfall is projected to decline across much of southern Australia with the exception of Tasmania, which is projected to experience little change or a rainfall increase in association with projected increases in the strength of the westerlies. Projected winter decrease is greatest in southwest Western Australia. A 'seasonal paradox' between observations and CMIP5 model projections in the shoulder seasons is evident, with strong and consistent drying projected for spring and less drying projected for autumn, the reverse of the observed trends over the last 50 years. The models have some biases in the simulation of certain synoptic types (e.g. cutoff lows), the rainfall brought by those synoptic types, and the mechanism of rainfall production. Rainfall projections based on statistical downscaling are examined in relation to some of these biases, projecting stronger future declines in some regions of southeast Australia in autumn than indicated by the host models, as well as little change to the magnitude of the projected declines in spring. Apart from Tasmania in winter, the decline of rainfall in southern Australia during the cool season remains a confident projection but the seasonal expression of change remains an ongoing research topic.

show abstract

Section: Discussion and Synthesismentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Seasonal and regional signature of the projected southern Australian rainfall reduction

Hope¹,

Grose²,

Timbal³

et al. 2015

AMOJ

View full text Add to dashboard Cite

show abstract

“…Frontal systems are often associated with rainfall, and the strength of this association is of interest in many climatological studies (e.g., Pook et al 2012;Catto et al 2012). To explore this, the rainfall associated with fronts will be assessed in this section.…”

Section: E Cwb Rainfall and Frontsmentioning

confidence: 99%

“…A number of automated algorithms have now been applied to large-scale fields available from reanalyses in order to generate climatologies of fronts [McIntosh et al (2008) for southwest Western Australia, Berry et al (2011a) for the globe, and Simmonds et al (2012) for the Southern Hemisphere]. The ability of these methods to identify fronts from relatively low-resolution data suggests that they can also be applied to climate model output, and this has recently been demonstrated by Catto et al (2013). The focus of the Berry et al and Simmonds et al studies was on the climatologies, whereas here our interest centers on the synoptics of the fronts and their consequences.…”

Section: Introductionmentioning

confidence: 99%

A Comparison of Automated Methods of Front Recognition for Climate Studies: A Case Study in Southwest Western Australia

Hope

Keay

Pook

et al. 2014

Monthly Weather Review

View full text Add to dashboard Cite

The identification of extratropical fronts in reanalyses and climate models is an important climate diagnostic that aids dynamical understanding and model verification. This study compares six frontal identification methods that are applied to June and July reanalysis data over the Central Wheatbelt of southwest Western Australia for . Much of the winter rainfall over this region originates from frontal systems. Five of the methods use automated algorithms. These make use of different approaches, based on shifts in 850-hPa winds (WND), gradients of temperature (TGR) and wet-bulb potential temperature (WPT), pattern matching (PMM), and a self-organizing map (SOM). The sixth method was a manual synoptic technique (MAN). On average, about 50% of rain days were associated with fronts in most schemes (although methods PMM and SOM exhibited a lower percentage). On a daily basis, most methods identify the same systems more than 50% of the time, and over the 28-yr period the seasonal time series correlate strongly. The association with rainfall is less clear. The WND time series of seasonal frontal counts correlate significantly with Central Wheatbelt rainfall. All automated methods identify fronts on some days that are classified as cutoff lows in the manual analysis, which will impact rainfall correlations. The front numbers identified on all days by the automated methods decline from 1979 to 2006 (but only the TGR and WPT trends were significant at the 10% level). The results here highlight that automated techniques have value in understanding frontal behavior and can be used to identify the changes in the frequency of frontal systems through time.

show abstract

“…Where attention is paid to shorter-term variability, studies have adopted a phenomenological approach, analyzing precipitation associated with synoptic features, such as mesoscale fronts and convective systems (e.g., Brown et al, 2010;Catto et al, 2013;Van Weverberg et al, 2013), or sub-seasonal modes, such as the Madden-Julian Oscillation (MJO; e.g., Hung et al, 2013). Yet the processes that produce precipitation in GCMs -the interactions between the sub-gridscale parameterizations and the resolved dynamicsfunction on the native gridscale and time step of the models, not on a 3 h or daily mean basis or on a regional average.…”

Section: Introductionmentioning

confidence: 99%

ASoP (v1.0): a set of methods for analyzing scales of precipitation in general circulation models

2017

View full text Add to dashboard Cite

Abstract. General circulation models (GCMs) have been criticized for their failure to represent the observed scales of precipitation, particularly in the tropics where simulated daily rainfall is too light, too frequent and too persistent. Previous assessments have focused on temporally or spatially averaged precipitation, such as daily means or regional averages. These evaluations offer little actionable information for model developers, because the interactions between the resolved dynamics and parameterized physics that produce precipitation occur at the native gridscale and time step.We introduce a set of diagnostics ("Analyzing Scales of Precipitation", version 1.0 -ASoP1) to compare the spatial and temporal scales of precipitation across GCMs and observations, which can be applied to data ranging from the gridscale and time step to regional and sub-monthly averages. ASoP1 measures the spectrum of precipitation intensity, temporal variability as a function of intensity and spatial and temporal coherence. When applied to time step, gridscale tropical precipitation from 10 GCMs, the diagnostics reveal that, far from the "dreary" persistent light rainfall implied by daily mean data, most models produce a broad range of time step intensities that span 1-100 mm day −1 . Models show widely varying spatial and temporal scales of time step precipitation. Several GCMs show concerning quasi-random behavior that may influence and/or alter the spectrum of atmospheric waves. Averaging precipitation to a common spatial (≈ 600 km) or temporal (3 h) resolution substantially reduces variability among models, demonstrating that averaging hides a wealth of information about intrinsic model behavior. When compared against satellite-derived analyses at these scales, all models produce features that are too large and too persistent.

show abstract

A global evaluation of fronts and precipitation in the ACCESS model

Cited by 38 publications

References 33 publications

Seasonal and regional signature of the projected southern Australian rainfall reduction

Seasonal and regional signature of the projected southern Australian rainfall reduction

A Comparison of Automated Methods of Front Recognition for Climate Studies: A Case Study in Southwest Western Australia

ASoP (v1.0): a set of methods for analyzing scales of precipitation in general circulation models

Contact Info

Product

Resources

About