Rainfall reductions over Southern Hemisphere semi-arid regions: the role of subtropical dry zone expansion

Cai, Wenju; Cowan, Tim; Thatcher, Marcus

doi:10.1038/srep00702

Cited by 123 publications

(145 citation statements)

References 28 publications

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“…2 (with a pattern correlation coefficient of 0.46, statistically significant at the 95% level): the rainfall increase over the high latitudes is still apparent, but there are larger zonal asymmetries compared with the warm season. Over the midlatitudes, the REwens depicts drying regions over the central Pacific and the Indian Oceans and over southern South America and southeastern Australia, in agreement with both GPCP data and with results from regional studies (for Australia, Delworth and Zeng 2014;Cai et al 2012). Note that there is a strong agreement between regions where rainfall increases (decreases) and the eddy activity and moisture availability increase (decrease).…”

Section: A the Climate Change Signal In The Sh As Depicted By The Resupporting

confidence: 72%

Climate Change over the Extratropical Southern Hemisphere: The Tale from an Ensemble of Reanalysis Datasets

Solman

Orlanski

2016

Journal of Climate

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In this study, a set of five reanalysis datasets [ERA-Interim, NCEP-DOE AMIP-II reanalysis (R2), MERRA, the Twentieth Century Reanalysis (20CR), and the CFS Reanalysis (CFSR)] is used to provide a robust estimation of precipitation change in the middle-to-high latitudes of the Southern Hemisphere during the last three decades. Based on several metrics accounting for the eddy activity and moisture availability, an attempt is also made to identify the dynamical mechanisms triggering these changes during extended summer and winter seasons. To that aim, a weighted reanalysis ensemble is built using the inverse of the variance as weighting factors for each variable. Results showed that the weighted reanalysis ensemble reproduced the observed precipitation changes at high and middle latitudes during the two seasons, as depicted by the GPCP dataset. For the extended summer season, precipitation changes were dynamically consistent with changes in the eddy activity, attributed mostly to ozone depletion. For the extended winter season, the eddy activity and moisture availability both contributed to the precipitation changes, with the increased concentration of greenhouse gases being the main driver of the climate change signal.In addition, output from a five-member ensemble of the high-resolution GFDL CM2.5 for the period 1979-2010 was used in order to explore the capability of the model in reproducing both the observed precipitation change and the underlying dynamical mechanisms. The model was able to capture the rainfall change signal. However, the increased availability of moisture from the lower levels controls the precipitation change during both summer and winter.

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Section: A the Climate Change Signal In The Sh As Depicted By The Resupporting

confidence: 72%

Climate Change over the Extratropical Southern Hemisphere: The Tale from an Ensemble of Reanalysis Datasets

Solman

Orlanski

2016

Journal of Climate

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“…This persistent rainfall deficit has been shown to be associated with changes in the global atmospheric circulation via the expansion of the Hadley circulation (estimated at 50 km per decade) and associated increase in pressure in the subtropical ridge, resulting in mid-latitude storm tracks being "pushed" further south (CSIRO, 2012;Whan et al, 2014). Cai et al (2012) also related the observed expansion of the Hadley Cell to a poleward progression of the tropical belt and subtropical dry zone, which they claim can explain most of the southeastern Australian rainfall decline. The expansion of the Hadley Cell can only be reproduced by global climate models when human influences (in the form of greenhouse gases, aerosols and stratospheric ozone) are included, leading to the assertion that the expansion is at least partially attributed to anthropogenic climate change (CSIRO, 2012;Lucas et al, 2012).…”

Section: The Big Dry In the Context Of Other Southern Hemisphere Droumentioning

confidence: 99%

Links between the Big Dry in Australia and hemispheric multi-decadal climate variability – implications for water resource management

Verdon‐Kidd

Kiem²,

Moran³

2014

Hydrol. Earth Syst. Sci.

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Abstract. Southeast Australia (SEA) experienced a protracted drought during the mid-1990s until early 2010 (known as the Big Dry or Millennium Drought) that resulted in serious environmental, social and economic effects. This paper analyses a range of historical climate data sets to place the recent drought into context in terms of Southern Hemisphere inter-annual to multi-decadal hydroclimatic variability. The findings indicate that the recent Big Dry in SEA is in fact linked to the widespread Southern Hemisphere climate shift towards drier conditions that began in the mid-1970s. However, it is shown that this link is masked because the large-scale climate drivers responsible for drying in other regions of the mid-latitudes since the mid-1970s did not have the same effect on SEA during the mid-to late 1980s and early 1990s. More specifically, smaller-scale synoptic processes resulted in elevated autumn and winter rainfall (a crucial period for SEA hydrology) during the mid-to late 1980s and early 1990s, which punctuated the longer-term drying. From the mid-1990s to 2010 the frequency of the synoptic processes associated with elevated autumn/winter rainfall decreased, resulting in a return to drier than average conditions and the onset of the Big Dry. The findings presented in this paper have marked implications for water management and climate attribution studies in SEA, in particular for understanding and dealing with "baseline" (i.e. current) hydroclimatic risks.

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“…Frequent drought events over the Southern Hemisphere subtropics have been mainly attributed to the recent poleward expansion and intensification of the descending branch of the Hadley Circulation [4]. Indeed, widespread droughts have affected recently several regions in the Southern Hemisphere.…”

Section: Introductionmentioning

confidence: 99%

Spatio-Temporal Patterns of the 2010–2015 Extreme Hydrological Drought across the Central Andes, Argentina

Rivera

Penalba

Villalba

et al. 2017

Water

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During the period 2010-2015, the semi-arid Central Andes in Argentina (CAA) experienced one of the most severe and long-lasting hydrological droughts on record. Since the snowmelt is the most important source of water, the reduced snowfall over the mountains propagated the drought signal through the streamflows in the adjacent foothills east of the Andes ranges. Motivated by the widespread impacts on the socio-economic activities in the region, this study aims to characterize the recent hydrological drought in terms of streamflow deficits. Based on streamflow data from 20 basins, we used the standardized streamflow index (SSI) to characterize hydrological droughts during the period 1971-2016. We found that the regional extent of the 2010-2015 hydrological drought was limited to the basins located north of 38 • S, with mean duration of 67 months and maximum drought severity exhibiting a heterogeneous pattern in terms of spatial distribution and time of occurrence. The drought event reached extreme conditions in 14 of the 15 basins in the CAA, being record-breaking drought in six of the basins. This condition was likely driven by a cooling in the tropical Pacific Ocean resembling La Niña conditions, which generated a decrease in snowfall over the Andes due to suppressed frontal activity.

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Rainfall reductions over Southern Hemisphere semi-arid regions: the role of subtropical dry zone expansion

Cited by 123 publications

References 28 publications

Climate Change over the Extratropical Southern Hemisphere: The Tale from an Ensemble of Reanalysis Datasets

Climate Change over the Extratropical Southern Hemisphere: The Tale from an Ensemble of Reanalysis Datasets

Links between the Big Dry in Australia and hemispheric multi-decadal climate variability – implications for water resource management

Spatio-Temporal Patterns of the 2010–2015 Extreme Hydrological Drought across the Central Andes, Argentina

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