scholarly journals Need for Caution in Interpreting Extreme Weather Statistics

2015 ◽  
Vol 28 (23) ◽  
pp. 9166-9187 ◽  
Author(s):  
Prashant D. Sardeshmukh ◽  
Gilbert P. Compo ◽  
Cécile Penland
Keyword(s):  
Process Model ◽  
Large Scale ◽  
Probability Distributions ◽  
Extreme Weather ◽  
Recent Change ◽  
Atmospheric Variability ◽  
Tail Probabilities ◽  
The North ◽  
Special Cases ◽  
Non Gaussian

Abstract Given the reality of anthropogenic global warming, it is tempting to seek an anthropogenic component in any recent change in the statistics of extreme weather. This paper cautions that such efforts may, however, lead to wrong conclusions if the distinctively skewed and heavy-tailed aspects of the probability distributions of daily weather anomalies are ignored or misrepresented. Departures of several standard deviations from the mean, although rare, are far more common in such a distinctively non-Gaussian world than they are in a Gaussian world. This further complicates the problem of detecting changes in tail probabilities from historical records of limited length and accuracy. A possible solution is to exploit the fact that the salient non-Gaussian features of the observed distributions are captured by so-called stochastically generated skewed (SGS) distributions that include Gaussian distributions as special cases. SGS distributions are associated with damped linear Markov processes perturbed by asymmetric stochastic noise and as such represent the simplest physically based prototypes of the observed distributions. The tails of SGS distributions can also be directly linked to generalized extreme value (GEV) and generalized Pareto (GP) distributions. The Markov process model can be used to provide rigorous confidence intervals and to investigate temporal persistence statistics. The procedure is illustrated for assessing changes in the observed distributions of daily wintertime indices of large-scale atmospheric variability in the North Atlantic and North Pacific sectors over the period 1872–2011. No significant changes in these indices are found from the first to the second half of the period.

scholarly journals Large-Scale Flow and the Long-Lasting Blocking High over Russia: Summer 2010

2012 ◽  
Vol 140 (9) ◽  
pp. 2967-2981 ◽  
Author(s):  
Andrea Schneidereit ◽  
Silke Schubert ◽  
Pavel Vargin ◽  
Frank Lunkeit ◽  
Xiuhua Zhu ◽  
...  
Keyword(s):  
Heat Wave ◽  
Large Scale ◽  
Wave Structure ◽  
Arctic Region ◽  
Stationary Wave ◽  
Boreal Summer ◽  
Atmospheric Variability ◽  
The North ◽  
Blocking High ◽  
Large Scale Flow

Abstract Several studies show that the anomalous long-lasting Russian heat wave during the summer of 2010, linked to a long-persistent blocking high, appears mainly as a result of natural atmospheric variability. This study analyzes the large-scale flow structure based on the ECMWF Re-Analysis Interim (ERA-Interim) data (1989–2010). The anomalous long-lasting blocking high over western Russia including the heat wave occurs as an overlay of a set of anticyclonic contributions on different time scales. (i) A regime change in ENSO toward La Niña modulates the quasi-stationary wave structure in the boreal summer hemisphere supporting the eastern European blocking. The polar Arctic dipole mode is enhanced and shows a projection on the mean blocking high. (ii) Together with the quasi-stationary wave anomaly, the transient eddies maintain the long-lasting blocking. (iii) Three different pathways of wave action are identified on the intermediate time scale (~10–60 days). One pathway commences over the eastern North Pacific and includes the polar Arctic region; another one runs more southward and crossing the North Atlantic, continues to eastern Europe; a third pathway southeast of the blocking high describes the downstream development over South Asia.

scholarly journals Rapid ablation zone expansion amplifies north Greenland mass loss

2019 ◽  
Vol 5 (9) ◽  
pp. eaaw0123 ◽  
Author(s):  
Brice Noël ◽  
Willem Jan van de Berg ◽  
Stef Lhermitte ◽  
Michiel R. van den Broeke
Keyword(s):  
Mass Loss ◽  
Large Scale ◽  
Greenland Ice Sheet ◽  
Recent Change ◽  
Early Summer ◽  
Enhanced Absorption ◽  
The North ◽  
Relative Contribution ◽  
Atmospheric Warming ◽  
North Greenland

Since the early 1990s, the Greenland ice sheet (GrIS) has been losing mass at an accelerating rate, primarily due to enhanced meltwater runoff following atmospheric warming. Here, we show that a pronounced latitudinal contrast exists in the GrIS response to recent warming. The ablation area in north Greenland expanded by 46%, almost twice as much as in the south (+25%), significantly increasing the relative contribution of the north to total GrIS mass loss. This latitudinal contrast originates from a different response to the recent change in large-scale Arctic summertime atmospheric circulation, promoting southwesterly advection of warm air toward the GrIS. In the southwest, persistent high atmospheric pressure reduced cloudiness, increasing runoff through enhanced absorption of solar radiation; in contrast, increased early-summer cloudiness in north Greenland enhanced atmospheric warming through decreased longwave heat loss. This triggered a rapid snowline retreat, causing early bare ice exposure, amplifying northern runoff.

scholarly journals Tropopause referenced ozone climatology and inter-annual variability (1994–2003) from the MOZAIC programme

2006 ◽  
Vol 6 (4) ◽  
pp. 1033-1051 ◽  
Author(s):  
V. Thouret ◽  
J.-P. Cammas ◽  
B. Sauvage ◽  
G. Athier ◽  
R. Zbinden ◽  
...  
Keyword(s):  
Large Scale ◽  
Strong Positive Correlation ◽  
Tropopause Height ◽  
Atmospheric Variability ◽  
Automatic Equipment ◽  
Upper Troposphere ◽  
Annual Variability ◽  
The North ◽  
Nao Index ◽  
The North Atlantic Oscillation

Abstract. The MOZAIC programme collects ozone and water vapour data using automatic equipment installed on board five long-range Airbus A340 aircraft flying regularly all over the world since August 1994. Those measurements made between September 1994 and August 1996 allowed the first accurate ozone climatology at 9–12 km altitude to be generated. The seasonal variability of the tropopause height has always provided a problem when constructing climatologies in this region. To remove any signal from the seasonal and synoptic scale variability in tropopause height we have chosen in this further study of these and subsequent data to reference our climatology to the altitude of the tropopause. We define the tropopause as a mixing zone 30 hPa thick across the 2 pvu potential vorticity surface. A new ozone climatology is now available for levels characteristic of the upper troposphere (UT) and the lower stratosphere (LS) regardless of the seasonal variations of the tropopause over the period 1994–2003. Moreover, this new presentation has allowed an estimation of the monthly mean climatological ozone concentration at the tropopause showing a sine seasonal variation with a maximum in May (120 ppbv) and a minimum in November (65 ppbv). Besides, we present a first assessment of the inter-annual variability of ozone in this particular critical region. The overall increase in the UTLS is about 1%/yr for the 9 years sampled. However, enhanced concentrations about 10–15 % higher than the other years were recorded in 1998 and 1999 in both the UT and the LS. This so-called "1998–1999 anomaly" may be attributed to a combination of different processes involving large scale modes of atmospheric variability, circulation features and local or global pollution, but the most dominant one seems to involve the variability of the North Atlantic Oscillation (NAO) as we find a strong positive correlation (above 0.60) between ozone recorded in the upper troposphere and the NAO index. A strong anti-correlation is also found between ozone and the extremes of the Northern Annular Mode (NAM) index, attributing the lower stratospheric variability to dynamical anomalies. Finally this analysis highlights the coupling between the troposphere, at least the upper one, and the stratosphere, at least the lower one.

Multiplicative Noise and Non-Gaussianity: A Paradigm for Atmospheric Regimes?

2005 ◽  
Vol 62 (5) ◽  
pp. 1391-1409 ◽  
Author(s):  
Philip Sura ◽  
Matthew Newman ◽  
Cécile Penland ◽  
Prashant Sardeshmukh
Keyword(s):  
Large Scale ◽  
Multiplicative Noise ◽  
Probability Distributions ◽  
Joint Probability ◽  
Joint Probability Distribution ◽  
Stochastic Perturbations ◽  
The Past ◽  
State Dependent ◽  
Non Gaussian ◽  
Noise Statistics

Abstract Atmospheric circulation statistics are not strictly Gaussian. Small bumps and other deviations from Gaussian probability distributions are often interpreted as implying the existence of distinct and persistent nonlinear circulation regimes associated with higher-than-average levels of predictability. In this paper it is shown that such deviations from Gaussianity can, however, also result from linear stochastically perturbed dynamics with multiplicative noise statistics. Such systems can be associated with much lower levels of predictability. Multiplicative noise is often identified with state-dependent variations of stochastic feedbacks from unresolved system components, and may be treated as stochastic perturbations of system parameters. It is shown that including such perturbations in the damping of large-scale linear Rossby waves can lead to deviations from Gaussianity very similar to those observed in the joint probability distribution of the first two principal components (PCs) of weekly averaged 750-hPa streamfunction data for the past 52 winters. A closer examination of the Fokker–Planck probability budget in the plane spanned by these two PCs shows that the observed deviations from Gaussianity can be modeled with multiplicative noise, and are unlikely the results of slow nonlinear interactions of the two PCs. It is concluded that the observed non-Gaussian probability distributions do not necessarily imply the existence of persistent nonlinear circulation regimes, and are consistent with those expected for a linear system perturbed by multiplicative noise.

scholarly journals Decadal changes in hydrographic and ecological time-series in the Balearic Sea (western Mediterranean), identifying links between climate and zooplankton

2008 ◽  
Vol 65 (3) ◽  
pp. 311-317 ◽  
Author(s):  
Maria Luz Fernández de Puelles ◽  
Juan Carlos Molinero
Keyword(s):  
Time Series ◽  
Large Scale ◽  
Western Mediterranean ◽  
Zooplankton Abundance ◽  
Atmospheric Variability ◽  
Survey Period ◽  
Climate Effect ◽  
The North ◽  
Western Mediterranean Sea ◽  
Balearic Sea

Abstract Fernández de Puelles, M. L., and Molinero, J. C. 2008. Decadal changes in hydrographic and ecological time-series in the Balearic Sea (western Mediterranean), identifying links between climate and zooplankton. – ICES Journal of Marine Science, 65: 311–317. We investigated possible relationships between climate, hydrography, and zooplankton abundance in the Balearic Sea (BS), during a 10-year survey period spanning January 1994 to December 2003. It was demonstrated that large-scale atmospheric variability in the North Atlantic (NA) Ocean acts as a driver of regional meteorological variations and hydrographic patterns in the BS. The results also revealed that the variability of copepods, appendicularians, cladocerans, siphonophores, doliolids, and ostracods is closely related to variations in water temperature recorded during strong anomalies of the NA climate (>1 s.d.). Although the time-series that we analysed cover a period that is relatively short for investigating climate effects on marine ecosystems, the statistical results reported were consistent enough to emphasize the NA’s climate effect on the BS. The cascade of links identified by these results should be considered and integrated into the assessment and modelling studies of pelagic ecosystem and biogeochemical fluxes in the western Mediterranean Sea.

scholarly journals A Preliminary Study: Marine Biogeography of Nautilus in the Bangka Belitung Seas, Indonesia

2021 ◽  
Vol 26 (3) ◽  
pp. 147-154
Author(s):  
Siti Aisyah ◽  
Josaphat Tetuko Sri Sumantyo ◽  
Aditya Pamungkas ◽  
M Rizza Muftiadi ◽  
Muh Yusuf
Keyword(s):  
Large Scale ◽  
Local Area ◽  
Limiting Factor ◽  
The West ◽  
Living Fossil ◽  
The North ◽  
Surface Temperatures ◽  
Special Cases ◽  
Original Habitat ◽  
West Monsoon

Nautilus is the only surviving genus whose members were numerous and widely dispersed in the oceans throughout the Jurassic and Miocene times. It represents the only living member from the Family Nautilidae and is often considered as a living fossil. Nautilus is found with high biodiversity in Ambon, Indonesia, and were in special cases even found in Bangka Belitung, far from their original habitat. This study aimed to understand the historical component of the habitat and distribution of Nautilus in Bangka Belitung and to determine the depth, temperature, current, and environmental heterogeneity relate to Nautilus. Nautilus samples were found in Bangka Belitung Seas nearby a crack region at 50–75 m deep while the optimal depth of the Nautilus was 150–300 m, depending on the local area. The locations in the Bangka Belitung Seas where Nautilus found have sea surface temperatures between 30-31°C and 27-28°C during the East Monsoon and the West Monsoon respectivelly. The implications of temperature as a limiting factor are fairly significant, as it restricts the upper limit of the living habitat to predictable depths, which vary both geographically and seasonally during the West Monsoon when surface temperatures approach habitable levels. Sea currents at the Bangka Belitung Seas move at 0–0.6 m.s-1 during the East Monsoon and speed up near the North Natuna Sea. During the West Monsoon, currents predominantly flow from the Natuna Sea to the Java Sea at 0–0.5 m.s-1. Large-scale deep-water currents and the effects of smaller currents on scent dispersal influence the directional movements of Nautilus.

scholarly journals Tropopause referenced ozone climatology and inter-annual variability (1994–2003) from the MOZAIC programme

2005 ◽  
Vol 5 (4) ◽  
pp. 5441-5488 ◽  
Author(s):  
V. Thouret ◽  
J.-P. Cammas ◽  
B. Sauvage ◽  
G. Athier ◽  
R. Zbinden ◽  
...  
Keyword(s):  
Large Scale ◽  
Strong Positive Correlation ◽  
Tropopause Height ◽  
Atmospheric Variability ◽  
Automatic Equipment ◽  
Upper Troposphere ◽  
Annual Variability ◽  
The North ◽  
Nao Index ◽  
The North Atlantic Oscillation

Abstract. The MOZAIC programme collects ozone and water vapour data using automatic equipment installed on board five long-range Airbus A340 aircraft flying regularly all over the world since August 1994. Those measurements made between September 1994 and August 1996 allowed the first accurate ozone climatology at 9–12 km altitude to be generated. The seasonal variability of the tropopause height has always provided a problem when constructing climatologies in this region. To remove any signal from the seasonal and synoptic scale variability in tropopause height we have chosen in this further study of these and subsequent data to reference our climatology to the altitude of the tropopause. We define the tropopause as a mixing zone 30 hPa thick across the 2 pvu potential vorticity surface. A new ozone climatology is now available for levels characteristic of the upper troposphere (UT) and the lower stratosphere (LS) regardless of the seasonal variations of the tropopause over the period 1994–2003. More over, this new presentation has allowed an estimation of the monthly mean climatological ozone concentration at the tropopause showing a sine seasonal variation with a maximum in May (120 ppbv) and a minimum in November (65 ppbv). Besides, we present a first assessment of the inter-annual variability of ozone in this particular critical region. The overall increase in the UTLS is about 1%/yr for the 9 years sampled. However, enhanced concentrations about 10–15% higher than the other years were recorded in 1998 and 1999 in both the UT and the LS. This so-called "1998–1999 anomaly'' may be attributed to a combination of different processes involving large scale modes of atmospheric variability, circulation features and local or global pollution, but the most dominant one seems to involve the variability of the North Atlantic Oscillation (NAO) as we find a strong positive correlation (above 0.60) between ozone recorded in the upper troposphere and the NAO index. A strong anti-correlation is also found between ozone and the Northern Annular Mode (NAM) index, attributing the lower stratospheric variability to dynamical anomalies. Finally this analysis highlights the coupling between the troposphere, at least the upper one, and the stratosphere, at least the lower one.

Secondary circulation in shallow ocean straits: Observations and numerical modeling of the Danish Straits

2020 ◽  
Author(s):  
Verena Haid ◽  
Emil Stanev ◽  
Johannes Pein ◽  
Joanna Staneva ◽  
Wei Chen
Keyword(s):  
Large Scale ◽  
Unstructured Grid ◽  
Secondary Circulation ◽  
Atmospheric Variability ◽  
Tidal Straining ◽  
The North ◽  
The North Sea ◽  
Similarities And Differences ◽  
Transport And Mixing ◽  
Resolution Simulation

<p>We study the secondary circulation in the Danish Straits using the unstructured-grid hydrodynamic model SCHISM covering the North Sea and Baltic Sea. The resolution in the straits is up to ~100 m. Since the large-scale atmospheric variability controls the transport in these straits, we focus on the processes with subtidal time scales. We compare the in- and outflows in the straits to flood and ebb flows in estuaries and analyze similarities and differences. Very prominently, the outflow and inflow phases of the Danish Straits feature substantial differences to the tidal straining in estuaries. With a resolution of ~100 m, new transport and mixing pathways, previously unresolved, appear fundamental to the strait dynamics. The variability of the strait bathymetry leads to a strongly differing appearance of secondary circulation. Helical cells, often with a horizontal extension of ~1 km, develop in the deep parts of the channels. A comparison between the high-resolution simulation and a simulation with a coarser grid of ~500 m in the straits suggests that the coarser resolution overestimates the stratification and misrepresents the transport balance. Axial velocities and transport through the Sound are underestimated by ~12%. These differences are explained by the underdeveloped secondary circulation in the coarse-resolution simulation and the associated changes in mixing along the straits. In conclusion, the use of ultrafine resolution grids is essential to adequately resolve secondary flow patterns and two-layer exchange.</p>

Analysis of Riser Measurements in the North Sea

1984 ◽  
Vol 28 (04) ◽  
pp. 272-281
Author(s):  
P. H. J. Verbeek
Keyword(s):  
North Sea ◽  
Active Zone ◽  
Probability Distributions ◽  
Bending Moment ◽  
The North ◽  
Simulation Techniques ◽  
Theoretical Predictions ◽  
Solution Methods ◽  
The North Sea ◽  
Non Gaussian

Riser measurements in the field have provided a variety of data collected from several locations in the North Sea. Data were obtained by means of instrumented riser joints installed in both a 24-in. and a 16-in. drilling riser. Bending moments in the riser, riser tensions, motions of the semisubmersible, and wave heights were recorded simultaneously. The measurement program was aimed at verifying predictions from theoretical riser models in the typical regions of riser response; namely, the wave-active zone at the top, the "boundary layer" at the bottom, and the riser main section in between. In this paper attention is focused on the data obtained for riser response in the wave-active zone. Measured results are compared with theoretical predictions based on both analytical solution methods and numerical time-domain simulation techniques. In particular, the relationship between the standard deviation of riser bending response and significant wave height is discussed, as is the probabilistic nature of riser response. It is concluded that standard deviations of measured bending moment response agree well with theoretical results. The probability distributions of measured response were found to be non-Gaussian and consistent with theoretical predictions based on Morison-type wave loading.

Why Has There Been No People’s Power Rebellion in North Korea?

2018 ◽  
pp. 1-34
Author(s):  
Andrew Jackson
Keyword(s):  
Rural Areas ◽  
North Korea ◽  
Large Scale ◽  
Political Elite ◽  
Information Control ◽  
Al Jazeera ◽  
The North ◽  
New Information ◽  
Effective System ◽  
The Right

One scenario put forward by researchers, political commentators and journalists for the collapse of North Korea has been a People’s Power (or popular) rebellion. This paper analyses why no popular rebellion has occurred in the DPRK under Kim Jong Un. It challenges the assumption that popular rebellion would happen because of widespread anger caused by a greater awareness of superior economic conditions outside the DPRK. Using Jack Goldstone’s theoretical expla-nations for the outbreak of popular rebellion, and comparisons with the 1989 Romanian and 2010–11 Tunisian transitions, this paper argues that marketi-zation has led to a loosening of state ideological control and to an influx of infor-mation about conditions in the outside world. However, unlike the Tunisian transitions—in which a new information context shaped by social media, the Al-Jazeera network and an experience of protest helped create a sense of pan-Arab solidarity amongst Tunisians resisting their government—there has been no similar ideology unifying North Koreans against their regime. There is evidence of discontent in market unrest in the DPRK, although protests between 2011 and the present have mostly been in defense of the right of people to support themselves through private trade. North Koreans believe this right has been guaranteed, or at least tacitly condoned, by the Kim Jong Un government. There has not been any large-scale explosion of popular anger because the state has not attempted to crush market activities outright under Kim Jong Un. There are other reasons why no popular rebellion has occurred in the North. Unlike Tunisia, the DPRK lacks a dissident political elite capable of leading an opposition movement, and unlike Romania, the DPRK authorities have shown some flexibility in their anti-dissent strategies, taking a more tolerant approach to protests against economic issues. Reduced levels of violence during periods of unrest and an effective system of information control may have helped restrict the expansion of unrest beyond rural areas.

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