scholarly journals Influence of solar forcing, climate variability and atmospheric circulation patterns on summer floods in Switzerland

2014 ◽  
Vol 11 (12) ◽  
pp. 13843-13890 ◽  
Author(s):  
J. C. Peña ◽  
L. Schulte ◽  
A. Badoux ◽  
M. Barriendos ◽  
A. Barrera-Escoda
Keyword(s):  
Solar Activity ◽  
North Atlantic Oscillation ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
Low Frequency ◽  
Flood Damage ◽  
Negative Phase ◽  
Atmospheric Circulation Patterns ◽  
Circulation Patterns ◽  
The Alps

Abstract. The higher frequency of severe flood events in Switzerland in recent decades has given fresh impetus to the study of flood patterns and their possible forcing mechanisms, particularly in mountain environments. This paper presents an index of summer flood damage that considers severe and catastrophic summer floods in Switzerland between 1800 and 2009, and explores the influence of solar and climate forcings on flood frequencies. In addition, links between floods and low-frequency atmospheric circulation patterns are examined. The flood damage index provides evidence that the 1817–1851, 1881–1927, 1977–1990 and 2005–present flood clusters occur mostly in phase with palaeoclimate proxies. The cross-spectral analysis documents that the periodicities detected in the coherency and phase spectra of 11 (Schwabe cycle) and 104 years (Gleissberg cycle) are related to a high frequency of flooding and solar activity minima, whereas the 22 year cyclicity detected (Hale cycle) is associated with solar activity maxima and a decrease in flood frequency. The analysis of atmospheric circulation patterns shows that Switzerland lies close to the border of the summer principal mode: the Summer North Atlantic Oscillation. The Swiss river catchments situated on the centre and southern flank of the Alps are affected by atmospherically unstable areas defined by the positive phase of the Summer North Atlantic Oscillation pattern, while those basins located in the northern slope of the Alps are predominantly associated with the negative phase of the pattern. Furthermore, a change in the low-frequency atmospheric circulation pattern related to the major floods occurred over the period from 1800 to 2009: the Summer North Atlantic Oscillation persists in negative phase during the last cool pulses of the Little Ice Age (1817–1851 and 1881–1927 flood clusters), whereas the positive phases of SNAO prevail during warmer climate of the last four decades (flood clusters from 1977 to present).

scholarly journals The sensitivity of snowfall to weather states over Sweden

2017 ◽  
Author(s):  
Lars Norin ◽  
Abhay Devasthale ◽  
Tristan S. L'Ecuyer
Keyword(s):  
North Atlantic Oscillation ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
Cyclonic Circulation ◽  
Satellite Observations ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Circulation Patterns ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract. For a high latitude country like Sweden snowfall is an important contributor to the regional water cycle. Furthermore, snowfall impacts surface properties, affects atmospheric thermodynamics, has implications for traffic and logistics management, disaster preparedness, and also impacts climate through changes in surface albedo and turbulent heat fluxes. For Sweden it has been shown that large-scale atmospheric circulation patterns, or weather states, are important for precipitation variability. Although the link between atmospheric circulation patterns and precipitation has been investigated for rainfall there are no studied focused on the sensitivity of snowfall to weather states over Sweden. In this work we investigate the response of snowfall to eight selected weather states. These weather states consist of four dominant wind directions together with cyclonic and anti-cyclonic circulation patterns and enhanced positive and negative phases of the North Atlantic oscillation. The presented analysis is based on multiple data sources, such as ground-based radar measurements, satellite observations, spatially-interpolated in situ observations, and reanalysis data. The data from these sources converge to underline the sensitivity of falling snow over Sweden to the different weather states. In this paper we examine both average snowfall intensities and snowfall accumulations associated with the different weather states. It is shown that even though the heaviest snowfall intensities occur during conditions with winds from the southwest, the largest contribution to snowfall accumulation arrives from winds from the southeast. Large differences in snowfall due to variations in the North Atlantic oscillation are shown as well as a strong effect of cyclonic and anti-cyclonic circulation patterns. Satellite observations are used to reveal the vertical structures of snowfall during the different weather states.

scholarly journals Strengthened Linkage between November/December North Atlantic Oscillation and Subsequent January European Precipitation after the Late 1980s

2020 ◽  
Vol 33 (19) ◽  
pp. 8281-8300
Author(s):  
Yang Liu ◽  
Shengping He
Keyword(s):  
North Atlantic Oscillation ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
Storm Track ◽  
Low Frequency ◽  
Early Winter ◽  
Atmospheric Circulation Patterns ◽  
Internal Climate Variability ◽  
The North ◽  
The North Atlantic

AbstractThis work investigates the nonsynchronous relationship between the North Atlantic Oscillation (NAO) and winter European precipitation. The results indicate that the linkage between early-winter (November and December) NAO and the following January precipitation and atmospheric circulation over the North Atlantic and European sectors became statistically significant after the late 1980s. Before the late 1980s, January precipitation and atmospheric circulation are weakly correlated with early-winter NAO. After the late 1980s, by contrast, the positive phase of the early-winter NAO is generally followed by an anomalous meridional dipole pattern with barotropic structure over the North Atlantic, which provides conditions for more (less) precipitation south of Iceland (east of the Azores). Further analysis elucidates that this regime shift may be partly attributed to the change of early-winter NAO, which is concurrent with significant change in the intensity of the synoptic and low-frequency eddy interaction over the Atlantic–European sectors. Anomalous positive sea level pressure and geopotential height, along with zonal wind anomalies associated with a positive early-winter NAO over the North Atlantic, are more significant and extend more northeastward after the late 1980s, which may be induced by an intensified transient eddy feedback after the late 1980s, as well as the enhanced storm-track activity over the North Atlantic. Thus, early-winter NAO can induce significant ocean temperature anomalies in the North Atlantic after the late 1980s, which extend downward into the middle parts of the thermocline and persist until the following January to trigger NAO-like atmospheric circulation patterns. Analyses from the Community Earth System Model large ensemble simulations indicate the effects of internal climate variability on such a strengthened linkage.

scholarly journals Influence of solar forcing, climate variability and modes of low-frequency atmospheric variability on summer floods in Switzerland

2015 ◽  
Vol 19 (9) ◽  
pp. 3807-3827 ◽  
Author(s):  
J. C. Peña ◽  
L. Schulte ◽  
A. Badoux ◽  
M. Barriendos ◽  
A. Barrera-Escoda
Keyword(s):  
Solar Activity ◽  
Damage Index ◽  
Low Frequency ◽  
Flood Damage ◽  
Flood Frequency ◽  
Ice Age ◽  
Negative Phase ◽  
Atmospheric Variability ◽  
The Alps ◽  
Fresh Impetus

Abstract. The higher frequency of severe flood events in Switzerland in recent decades has given fresh impetus to the study of flood patterns and their possible forcing mechanisms, particularly in mountain environments. This paper presents a new index of summer flood damage that considers severe and catastrophic summer floods in Switzerland between 1800 and 2009, and explores the influence of external forcings on flood frequencies. In addition, links between floods and low-frequency atmospheric variability patterns are examined. The flood damage index provides evidence that the 1817–1851, 1881–1927, 1977–1990 and 2005–present flood clusters occur mostly in phase with palaeoclimate proxies. The cross-spectral analysis documents that the periodicities detected in the coherency and phase spectra of 11 (Schwabe cycle) and 104 years (Gleissberg cycle) are related to a high frequency of flooding and solar activity minima, whereas the 22-year cyclicity detected (Hale cycle) is associated with solar activity maxima and a decrease in flood frequency. The analysis of low-frequency atmospheric variability modes shows that Switzerland lies close to the border of the principal summer mode. The Swiss river catchments situated on the centre and southern flank of the Alps are affected by atmospherically unstable areas defined by the positive phase of the pattern, while those basins located in the northern slope of the Alps are predominantly associated with the negative phase of the pattern. Furthermore, a change in the low-frequency atmospheric variability pattern related to the major floods occurred over the period from 1800 to 2009; the summer principal mode persists in the negative phase during the last cool pulses of the Little Ice Age (1817–1851 and 1881–1927 flood clusters), whereas the positive phases of the mode prevail during the warmer climate of the last 4 decades (flood clusters from 1977 to present).

scholarly journals The sensitivity of snowfall to weather states over Sweden

2017 ◽  
Vol 10 (9) ◽  
pp. 3249-3263 ◽  
Author(s):  
Lars Norin ◽  
Abhay Devasthale ◽  
Tristan S. L'Ecuyer
Keyword(s):  
North Atlantic Oscillation ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
Satellite Observations ◽  
Anticyclonic Circulation ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Circulation Patterns ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract. For a high-latitude country like Sweden snowfall is an important contributor to the regional water cycle. Furthermore, snowfall impacts surface properties, affects atmospheric thermodynamics, has implications for traffic and logistics management, disaster preparedness, and also impacts climate through changes in surface albedo and turbulent heat fluxes. For Sweden it has been shown that large-scale atmospheric circulation patterns, or weather states, are important for precipitation variability. Although the link between atmospheric circulation patterns and precipitation has been investigated for rainfall there are no studies focused on the sensitivity of snowfall to weather states over Sweden.In this work we investigate the response of snowfall to eight selected weather states. These weather states consist of four dominant wind directions together with cyclonic and anticyclonic circulation patterns and enhanced positive and negative phases of the North Atlantic Oscillation. The presented analysis is based on multiple data sources, such as ground-based radar measurements, satellite observations, spatially interpolated in situ observations, and reanalysis data. The data from these sources converge to underline the sensitivity of falling snow over Sweden to the different weather states.In this paper we examine both average snowfall intensities and snowfall accumulations associated with the different weather states. It is shown that, even though the heaviest snowfall intensities occur during conditions with winds from the south-west, the largest contribution to snowfall accumulation arrives with winds from the south-east. Large differences in snowfall due to variations in the North Atlantic Oscillation are shown as well as a strong effect of cyclonic and anticyclonic circulation patterns. Satellite observations are used to reveal the vertical structures of snowfall during the different weather states.

scholarly journals Seasonal temperatures over Italy and their relationship with low-frequency atmospheric circulation patterns

2009 ◽  
Vol 99 (1-2) ◽  
pp. 211-227 ◽  
Author(s):  
Andrea Toreti ◽  
Franco Desiato ◽  
Guido Fioravanti ◽  
Walter Perconti
Keyword(s):  
Atmospheric Circulation ◽  
Low Frequency ◽  
Atmospheric Circulation Patterns ◽  
Circulation Patterns

scholarly journals Recent Trends in the Recurrence of North Atlantic Atmospheric Circulation Patterns

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Pascal Yiou ◽  
Julien Cattiaux ◽  
Aurélien Ribes ◽  
Robert Vautard ◽  
Mathieu Vrac
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Emerging Trends ◽  
Circulation Patterns ◽  
Long Term Trends ◽  
Recent Trends ◽  
The Stability ◽  
Climate Events

A few types of extreme climate events in the North Atlantic region, such as heatwaves, cold spells, or high cumulated precipitation, are connected to the recurrence of atmospheric circulation patterns. Understanding those extreme events requires assessing long-term trends of the atmospheric circulation. This paper presents a set of diagnostics of the intra- and interannual recurrence of atmospheric patterns. Those diagnostics are devised to detect trends in the stability of the circulation and the return period of atmospheric patterns. We detect significant emerging trends in the winter circulation, pointing towards a potential increased predictability. No such signal seems to emerge in the summer. We find that the winter trends in the dominating atmospheric patterns and their recurrences do not depend of the patterns themselves.

Linkages between atmospheric circulation, climate and streamflow in the northern North Atlantic: research prospects

2006 ◽  
Vol 30 (2) ◽  
pp. 143-174 ◽  
Author(s):  
D. G. Kingston ◽  
D. M. Lawler ◽  
G. R. McGregor
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Analytical Techniques ◽  
Eastern Canada ◽  
Natural Systems ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Circulation Patterns ◽  
Northwest Europe ◽  
The North Atlantic Oscillation

This paper evaluates the relationships between atmospheric circulation, climate and streamflow in the northern North Atlantic region over the last century and especially the last 50 years. Improved understanding of climatic influences on streamflow is vital given the great importance of fluvial processes to natural systems and water resources, especially in the light of recent and predicted climate change. The main focus lies with climatic and hydrologic implications of the major circulation patterns in the northern North Atlantic, namely the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). The studies reviewed here reveal key relationships between circulation, climate and streamflow across the northern North Atlantic, allowing the construction of a simple conceptual model for this system. Generally positive NAO/AO-streamflow relationships are found in northwest Europe and northeast USA, with both positive and negative NAO/AO-streamflow linkages apparent for parts of eastern Canada. To help promote a better understanding of the system, several research gaps are identified and critically examined, including: the spatial scope and coverage of investigations; data quality and homogeneity; appropriateness of analytical techniques; and the need for greater knowledge and technique sharing between hydrology and climatology, particularly regarding the rigorous characterization of atmospheric circulation patterns. Among these, the development of seasonally varying, or mobile, NAO indices, to capture variations in subseasonal, seasonal and annual movements in the centres of action, and the need to develop analyses of more hydrologically meaningful climate variables beyond conventional time averaged statistics, are deemed particularly important.

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