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Analysis of the annual cycle of intensity, extent, and width of the Hadley circulation across a 31-yr period (1979-2009) from all existent reanalyses reveals a good agreement among the datasets. All datasets show that intensity is at a maximum in the winter hemisphere and at a minimum in the summer hemisphere. Maximum and minimum values of meridional extent are reached in the respective autumn and spring hemispheres. While considering the horizontal momentum balance, where a weakening of the Hadley cell (HC) is expected in association with a widening, it is shown here that there is no direct relationship between intensity and extent on a monthly time scale. All reanalyses show an expansion in both hemispheres, most pronounced and statistically significant during summer and autumn at an average rate of expansion of 0.55° decade−1 in each hemisphere. In contrast, intensity trends are inconsistent among the datasets, although there is a tendency toward intensification, particularly in winter and spring. Correlations between the HC and tropical and extratropical large-scale modes of variability suggest interactions where the extent of the HC is influenced by El Niño-Southern Oscillation (ENSO) and the annular modes. The cells tend to shrink (expand) during the warm (cold) phase of ENSO and during the low (high) phase of the annular modes. Intensity appears to be influenced only by ENSO and only during spring for the southern cell and during winter for the northern cell. [ABSTRACT FROM AUTHOR]

Much of southeast Australia has experienced rainfall substantially below the long-term average since 1997. This protracted drought is particularly noticeable in those parts of South Australia and Victoria which experience a winter (May through October) rainfall peak. For the most part, the recent meteorological drought has affected the first half of the rainfall season May-June-July (MJJ), while rainfall during the second half August-September-October (ASO) has been much closer to the long term average. The recent multi-year drought is without precedent in the instrumental record, and is qualitatively similar to the abrupt decline in rainfall which was observed in the southwest of Western Australia in the 1960 and 1970s. Using a statistical downscaling technique, the rainfall decline is linked to observed changes in large-scale atmospheric fields (mean sea level pressure and precipitable water). This technique is able to reproduce the statistical properties of rainfall in southeast Australia, including the interannual variability and longer time-scale changes. This has revealed that the rainfall recent decline may be explained by a shift to higher pressures and lower atmospheric precipitable water in the region. To explore the likely future evolution of rainfall in southeast Australia under human induced climate change, the same statistical downscaling technique is applied to five climate models forced with increasing greenhouse gas concentrations. This reveals that average rainfall in the region is likely to decline in the future as greenhouse gas concentrations increase, with the greatest decline occurring during the first half of winter. Projected declines vary amongst models but are generally smaller than the recent early winter rainfall deficits. In contrast, the rainfall decline in late winter-spring is larger in future projections than the recent rainfall deficits have been. We illustrate the consequences of the observed and projected rainfall declines on water supply to the major city of Melbourne, using a simple rainfall run-off relationship. This suggests that the water resources may be dramatically affected by future climate change, with percentage reductions approximately twice as large as corresponding changes in rainfall. [ABSTRACT FROM AUTHOR]

A statistical method, based on the idea of analogous synoptic situations, is used to study the observed rainfall trends in the SW of Western Australia. The method has been developed and optimised by relating patterns of atmospheric fields (predictors) to station records of rainfall (predictands), for both rain occurrences and daily rain amounts. When tested on observational data, the analogue method is able to reproduce the trend observed globally during the past 50 yr, showing the sensitivity of the statistical approach to changed climatic conditions. The choice of predictor has an important impact on the results: mean sea level pressure (MSLP) and vertically integrated precipitable water (PWTR) are both important in explaining the observed local rainfall trend. The model is then applied to 3 coupled models' simulations of the current climate. The improvement gained when using the statistical downscaling tool over direct model grid-average outputs is substantial. Most of the model biases are removed and realistic probability distribution functions at the station level are obtained. The method is then applied to altered climate conditions; the impact of model sensitivities on large-scale responses is quantified using the various coupled models. Future trends for rainfall, estimated by direct climate model outputs, are compared with downscaled projections. A general agreement is found; uncertainties are smaller amongst projections when the downscaling technique is used. All projections agree on a mean reduction of total rainfall in winter and spring. The possible impact of future drying trends induced by global warming is compounded by changes in mean and extreme rainfall, such as long wet spells and large yearly totals. [ABSTRACT FROM AUTHOR]

The article explores the anomalous activities of typhoon in the Northwestern Pacific and the Northern Japan's extreme precipitation in August 2016. Topics mentioned include the formation of typhoons in the northwestern Pacific basin back in August 2016 that made landfalls, the stark contrast when the first six months of the year have suppressed tropical cyclone activity and the association of the active typhoons in August with the lower troposphere's cyclonic circulation anomalies.