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Author Topic: Extreme weather event attribution  (Read 2190 times)

crandles

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Extreme weather event attribution
« on: December 29, 2016, 06:08:32 PM »
A couple of papers arising from climatepredition.net / weather@home

Real-time extreme weather event attribution with forecast seasonal SSTs
K Haustein et al 2016

Quote
Here we present a new method which can assess the fraction of attributable risk of a severe weather event due to an external driver in real-time. The method builds on a large ensemble of atmosphere-only general circulation model simulations forced by seasonal forecast sea surface temperatures (SSTs). Taking the England 2013/14 winter floods as an example, we demonstrate that the change in risk for heavy rainfall during the England floods due to anthropogenic climate change, is of similar magnitude using either observed or seasonal forecast SSTs. Testing the dynamic response of the model to the anomalous ocean state for January 2014, we find that observed SSTs are required to establish a discernible link between a particular SST pattern and an atmospheric response such as a shift in the jetstream in the model. For extreme events occurring under strongly anomalous SST patterns associated with known low-frequency climate modes, however, forecast SSTs can provide sufficient guidance to determine the dynamic contribution to the event.

Assessing mid‑latitude dynamics in extreme event attribution systems
Daniel Mitchell et al 2016
http://link.springer.com/article/10.1007/s00382-016-3308-z
Quote
Atmospheric modes of variability relevant for
extreme temperature and precipitation events are evaluated
in models currently being used for extreme event attribution.
A 100 member initial condition ensemble of the global circulation
model HadAM3P is compared with both the multimodel
ensemble from the Coupled Model Inter-comparison
Project, Phase 5 (CMIP5) and the CMIP5 atmosphere-only
counterparts (AMIP5). The use of HadAM3P allows for huge
ensembles to be computed relatively fast, thereby providing
unique insights into the dynamics of extremes. The analysis
focuses on mid Northern Latitudes (primarily Europe) during
winter, and is compared with ERA-Interim reanalysis.
The tri-modal Atlantic eddy-driven jet distribution is remarkably
well captured in HadAM3P, but not so in the CMIP5 or
AMIP5 multi-model mean, although individual models fare
better. The well known underestimation of blocking in the
Atlantic region is apparent in CMIP5 and AMIP5, and also,
to a lesser extent, in HadAM3P. Pacific blocking features
are well produced in all modeling initiatives. Blocking duration
is biased towards models reproducing too many shortlived
events in all three modelling systems. Associated storm
tracks are too zonal over the Atlantic in the CMIP5 and
AMIP5 ensembles, but better simulated in HadAM3P with
the exception of being too weak over Western Europe. In all
cases, the CMIP5 and AMIP5 performances were almost
identical, suggesting that the biases in atmospheric modes
considered here are not strongly coupled to SSTs, and perhaps
other model characteristics such as resolution are more
important. For event attribution studies, it is recommended
that rather than taking statistics over the entire CMIP5 or
AMIP5 available models, only models capable of producing
the relevant dynamical phenomena be employed.

logicmanPatrick

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Re: Extreme weather event attribution
« Reply #1 on: January 03, 2017, 12:47:32 AM »
Yes, Some Extreme Weather Can Be Blamed on Climate Change

Article on attribution science in Scientific American.

Quote
Scientific American spoke with Friederike Otto, deputy director of the Environmental Change Institute at the University of Oxford, about how attribution science works and why it’s a critical part of helping communities prepare for and adapt to climate change.

https://www.scientificamerican.com/article/yes-some-extreme-weather-can-be-blamed-on-climate-change/
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Archimid

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Re: Extreme weather event attribution
« Reply #2 on: January 03, 2017, 06:02:30 PM »
Title: New technique predicts frequency of heavy precipitation with global warming

Link: http://phys.org/news/2017-01-technique-frequency-heavy-precipitation-global.html

Extract:
Quote
Now MIT scientists have found that such extreme precipitation events in California should become more frequent as the Earth's climate warms over this century. The researchers developed a new technique that predicts the frequency of local, extreme rainfall events by identifying telltale large-scale patterns in atmospheric data.

Referenced paper: http://globalchange.mit.edu/files/document/MITJPSPGC_Rpt302.pdf
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vox_mundi

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Re: Extreme weather event attribution
« Reply #3 on: November 16, 2018, 06:12:13 PM »
It seems like precipitation follows the power law

Half of the World's Annual Precipitation Falls In Just 12 Days
https://phys.org/news/2018-11-world-annual-precipitation-falls-days.html


An analysis of rainfall measured at weather stations across the globe between 1999 and 2014 found that the median time it took for half of a year's precipitation to fall was just 12 days. A quarter of annual precipitation fell in just six days, and three-quarters fell in 27 days.

These results are published in Geophysical Research Letters, a journal of the American Geophysical Union.

To look forward, the scientists used simulations from 36 of the world's leading climate models that had data for daily precipitation. Then they pinpointed what the climate model projections for the last 16 years of this century would translate to for the individual observation stations.

They found that total annual precipitation at the observation stations increased slightly in the model runs, but the additional precipitation did not fall evenly. Instead, half of the extra rain and snow fell over just six days.

This contributed to total precipitation also falling more unevenly than it does today, with half of a year's total precipitation falling in just 11 days by 2100, compared to 12 in the current climate.


"While climate models generally project just a small increase in rain in general, we find this increase comes as a handful of events with much more rain and, therefore, could result in more negative impacts, including flooding," Pendergrass said. "We need to take this into account when we think about how to prepare for the future."

Open Access: Angeline G. Pendergrass et al, The Uneven Nature of Daily Precipitation and Its Change, Geophysical Research Letters (2018)

Quote
The change in precipitation in response to warming is more uneven than present‐day precipitation, and it occurs primarily during events often considered extreme.

In contrast to temperature, where climate change can be thought of as a simple shift of the distribution, the shape of the distribution of precipitation changes with warming so that the heaviest events make up a larger fraction of total precipitation. The uneven nature of precipitation increase could exacerbate impacts like flooding and drought. Rather than assuming more rain in general, society needs to take measures to deal with little change most of the time and a handful of events with much more rain.
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vox_mundi

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Re: Extreme weather event attribution
« Reply #4 on: May 25, 2019, 02:54:40 AM »
Climate Change is Destroying a Barrier That Protects the U.S. East Coast from Hurricanes 
https://m.phys.org/news/2019-05-climate-barrier-east-coast-hurricanes.html

A new paper, published today in Scientific Reports, finds that climate change could alter wind shear in a way that could deliver more powerful hurricanes to the East Coast. ... as hurricanes move northwestward out of the tropical Atlantic, a strong vertical wind shear along the East Coast prevents the storm from gaining strength, thus providing a protective barrier to strong landfalling hurricanes.

Ting and Kossin, along with Lamont researchers Suzana Camargo and Cuihua Li, used model simulations to examine the effects of climate change on hurricanes in the United States. The group found that these hurricanes will be affected in two different ways. As earlier studies have shown, rising sea surface temperatures will lead to an increase in hurricane intensity. But this study was the first to find that rising anthropogenic greenhouse gases in the atmosphere will weaken the vertical wind shear along the East Coast which will, in turn, enable further intensification of hurricanes that make landfall in this region.

"Once the natural protection is eroded by greenhouse gas warming, we may experience unprecedented hurricane intensification along the East Coast that can lead to stronger landfalling storms and higher storm surges in the future," Ting explains. "This is on top of the stronger tropical cyclone strength expected from the warmer sea surface temperature that we are already aware of. Home owners and policy makers have to take this into account when planning for coastal development and protections." 

Although climate change is typically a slow process, the models point to the possibility of these anthropogenic effects emerging quickly. One of the models with a larger number of simulations indicated that these effects could start to be seen around the year 2040. A timeline like that only gives us about 20 years to try to change course by taking actions to reduce climate change and, at the very least, prepare for more extreme weather events.



Open Access: Mingfang Ting et al. Past and Future Hurricane Intensity Change along the U.S. East Coast, Scientific Reports (2019)
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

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vox_mundi

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Re: Extreme weather event attribution
« Reply #5 on: June 04, 2019, 06:27:43 PM »
Loss of Arctic Sea Ice Stokes Summer Heat Waves in Southern U.S.   
https://m.phys.org/news/2019-06-loss-arctic-sea-ice-stokes.html


Composites of summer extreme (left panels) and oppressive heat wave (right panels) frequency during summers of low (top), neutral (middle) and high (bottom) Hudson Bay sea ice extent. Credit: AGU   

A new study in AGU's Journal of Geophysical Research: Atmospheres explores how seasonal fluctuations of sea ice coverage trigger changes in atmospheric circulation patterns during the boreal summer.

The study draws upon four decades of satellite data of Arctic sea ice coverage collected between 1979 and 2016, overlapped with heat wave frequency data across the United States during the same time period.

The team found evidence for a strong statistical relationship between the extent of summer sea ice in the Hudson Bay and heat waves across the southern Plains and southeastern U.S 

Quote
... "The latest research on this topic suggests that declining Arctic sea ice may be linked to increased incidence of extreme weather patterns across the northern hemisphere," said Dagmar Budikova, a climatologist at Illinois State University in Normal and lead author of the new study. "Our results confirm this hypothesis by offering further evidence that Arctic sea ice variability has the potential to influence extreme summer temperatures and the frequency of heat waves across the southern U.S."

The new study finds the loss of sea ice across the Arctic begins with warmer-than-usual spring temperatures in the Hudson Bay and Labrador regions in the southeastern Canadian Arctic.

"This process starts when temperatures across the southeastern Canadian Arctic and northwestern Atlantic are 2 degrees [Celsius] warmer than expected in March, April and May," Budikova said.

This springtime warming lessens the north-to-south change in temperature between the high and middle latitudes of eastern North America, leading to a reduction in the strength of regional wind patterns. These conditions are symptomatic of weakened large-scale movements of air that appear to persist into the summer months, Budikova said.

Dagmar Budikova et al. United States Heat Wave Frequency and Arctic Ocean Marginal Sea Ice Variability, Journal of Geophysical Research: Atmospheres (2019)
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late