Characterizing large-scale circulation triggering heavy precipitation amounts over the northern French Alps

2020 ◽  
Author(s):  
Antoine Blanc ◽  
Juliette Blanchet ◽  
Jean-Dominique Creutin
Keyword(s):  
Large Scale ◽  
Western Europe ◽  
Heavy Precipitation ◽  
Geostrophic Wind ◽  
Time Step ◽  
French Alps ◽  
Circulation Patterns ◽  
Combined Use ◽  
Applied Meteorology ◽  
Low Dimensional

<p><span>Large-scale circulations (LSCs) explain a significant part of Alpine precipitations. Characterizing circulations triggering heavy precipitation is usually done using weather-type classifications. A different characterization is implemented here, based on analogy using the atmospheric descriptors proposed in Blanchet et al 2018, 2019. These descriptors are both related to the dynamics of LSC and to their relative position in the atmospheric space. </span><span>This work is applied to the Isère river catchment for the 1950-2011 period, considering a 3-</span><span>day time step. The 500 hPa and 1000 hPa geopotential heights covering part of the western Europe are used separately to represent LSC. Two analogy criteria are investigated for constructing the atmospheric descriptors, namely TWS and RMSE.</span></p><p>Our results reveal that LSCs triggering heavy precipitation amounts correspond to strong geostrophic wind with quasi constant direction during the three days, corresponding to blocking situations in altitude. Moreover, those patterns of circulation are among the least singulars, and they show the highest degree of clustering in the atmospheric space. We interpret the latest results by the fact that heavy precipitation LSCs feature twin circulation patterns. In addition, the 500 hPa geopotential height appears to discriminate better heavy precipitation situations than the 1000 hPa one. Finally, our work points out the benefit of a combined use of TWS and RMSE. TWS gives information about the direction of geostrophic wind, while RMSE -combined with TWS- informs about its strength.</p><p>References:</p><p>Blanchet, J., Stalla, S., and Creutin, J.-D. (2018). Analogy of multi-day sequences of atmospheric circulation favoring large rainfall accumulation over the French Alps. Atmospheric Science Letters.</p><p>Blanchet, J., Creutin, J-D. <span>(2019). Modelling rainfall accumulations over several days in the French Alps using low-dimensional atmospheric predictors based on analogy. Journal of Applied Meteorology and Climatology.</span></p>

Predictability of large scale drivers leading intense Mediterranean cyclones

2020 ◽  
Author(s):  
M. Carmen Alvarez-Castro ◽  
Silvio Gualdi ◽  
Pascal Yiou ◽  
Mathieu Vrac ◽  
Robert Vautard ◽  
...  
Keyword(s):  
Climate Change ◽  
Large Scale ◽  
Human Life ◽  
Heavy Precipitation ◽  
Mediterranean Area ◽  
Frequency Of Occurrence ◽  
Large Scale Circulation ◽  
Mediterranean Cyclones ◽  
Circulation Patterns ◽  
Anthropogenic Forcings

<p>Windstorms, extreme precipitations and instant floods seems to strike the Mediterranean area with increasing frequency. These events occur simultaneously during intense tropical-like Mediterranean cyclones. These intense Mediterranean cyclones are frequently associated with wind, heavy precipitation and changes in temperature, generating high risk situations such as flash floods and large-scale floods with significant impacts on human life and built environment. Although the dynamics of these phenomena is well understood, little is know about their climatology. It is therefore very difficult to make statements about the frequency of occurrence and its response to climate change. Thus, intense Mediterranean cyclones have many different physical aspects that can not be captured by a simple standard approach. </p><p>The first challenge of this work is to provide an extended catalogue and climatology of these phenomena by reconstructing a database of intense Mediterranean cyclones dating back up to 1969 using the satellite, the literature and reanalyses. Applying a method based on dynamical systems theory we analyse and attribute their future changes under different anthropogenic forcings by using future simulations within CMIP framework. Preliminary results show a decrease of the large-scale circulation patterns favoring intense Mediterranean cyclones in all the seasons except summer.</p>

scholarly journals Trends and variability in extreme precipitation indices over Maghreb countries

2013 ◽  
Vol 13 (12) ◽  
pp. 3235-3248 ◽  
Author(s):  
Y. Tramblay ◽  
S. El Adlouni ◽  
E. Servat
Keyword(s):  
Atmospheric Circulation ◽  
Large Scale ◽  
Heavy Precipitation ◽  
Climate Indices ◽  
Atmospheric Circulation Patterns ◽  
Circulation Patterns ◽  
Precipitation Indices ◽  
Precipitation Records ◽  
Mediterranean Oscillation ◽  
Large Scale Atmospheric Circulation

Abstract. Maghreb countries are highly vulnerable to extreme hydrological events, such as floods and droughts, driven by the strong variability of precipitation. While several studies have analyzed the presence of trends in precipitation records for the Euro-Mediterranean basin, this study provides a regional assessment of trends on its southernmost shores. A database of 22 stations located in Algeria, Morocco and Tunisia with between 33 and 59 yr of daily precipitation records is considered. The change points and trends are analyzed for eleven climate indices, describing several features of the precipitation regime. The issue of conducting multiple hypothesis tests is addressed through the implementation of a false discovery rate procedure. The spatial and interannual variability of the precipitation indices at the different stations are analyzed and compared with large-scale atmospheric circulation patterns, including the North Atlantic Oscillation (NAO), western Mediterranean Oscillation (WEMO), Mediterranean Oscillation (MO) and El Niño–Southern Oscillation (ENSO). Results show a strong tendency towards a decrease of precipitation totals and wet days together with an increase in the duration of dry periods, mainly for Morocco and western Algeria. On the other hand, only a few significant trends are detected for heavy precipitation indices. The NAO and MO patterns are well correlated with precipitation indices describing precipitation amounts, the number of dry days and the length of wet and dry periods, whereas heavy precipitation indices exhibit a strong spatial variability and are only moderately correlated with large-scale atmospheric circulation patterns.

scholarly journals Patterns of extreme weather associated with observed and proxy River Ammer flood records

2017 ◽  
Author(s):  
Norel Rimbu ◽  
Monica Ionita ◽  
Markus Czymzik ◽  
Achim Brauer ◽  
Gerrit Lohmann
Keyword(s):  
Solar Activity ◽  
Radiative Forcing ◽  
Large Scale ◽  
Western Europe ◽  
Extreme Temperature ◽  
Heavy Precipitation ◽  
Flood Frequency ◽  
Discharge Data ◽  
Blocking High ◽  
Northeastern Europe

Abstract. We investigate the relationship between the variability in the frequency of River Ammer floods (southern Germany) and temperature/precipitation extremes over Europe using observational River Ammer discharge data back to 1926 and the 5500-year-long flood layer record from varved Lake Ammersee sediments. We show that observed River Ammer flood frequency variability is not only related with local extreme precipitation, but also with large-scale temperature extreme anomalies. Less (more) extreme high temperatures over central and western (northeastern) Europe are recorded during periods of increased River Ammer flood frequency. We argue that changing radiative forcing due to cloudiness anomaly patterns associated with River Ammer floods induce these extreme temperature anomalies. Consistent patterns are obtained using observed discharge and proxy flood layer frequency data. Furthermore, a higher frequency of observed River Ammer floods and flood layers is associated with enhanced blocking activity over northeastern Europe. A blocking high over this region increases the probability of wave breaking and associated heavy precipitation over western Europe. A similar blocking pattern is associated with periods of reduced solar activity. Consequently, solar modulated changes in blocking frequency over northeastern Europe could explain the connection between River Ammer floods and solar activity, as also identified in previous studies. We argue that multi-decadal to millennial flood frequency variations in the Mid- to Late Holocene flood layer record from Lake Ammersee characterizes also the extreme temperatures in northeastern Europe.

scholarly journals Explaining Rainfall Accumulations over Several Days in the French Alps Using Low-Dimensional Atmospheric Predictors Based on Analogy

2020 ◽  
Vol 59 (2) ◽  
pp. 237-250
Author(s):  
Juliette Blanchet ◽  
Jean-Dominique Creutin
Keyword(s):  
Large Scale ◽  
Western Europe ◽  
Cumulative Distribution ◽  
New Approach ◽  
Pressure Fields ◽  
Topology Mapping ◽  
Alpine Watershed ◽  
Low Dimensional ◽  
Local Topology ◽  
Classical Analogy

AbstractWe propose a new approach to explain multiday rainfall accumulation over a French Alpine watershed using large-scale atmospheric predictors based on analogy. The classical analogy framework associates a rainfall cumulative distribution function (CDF) with a given atmospheric situation from the precipitation accumulations yielded by the closest situations. The analogy may apply to single-day or multiday sequences of pressure fields. The proposed approach represents a paradigm shift in analogy. It relies on the similarity of the local topology mapping the pressure field sequences, somehow forgetting the pressure fields per se. This topology is summarized by the way the sequences of pressure fields resemble their neighbors (dimensional predictors) and how fast they evolve in time (dynamical predictors). Although some information—and hence predictability—is expected to be lost when compared with classical analogy, this approach provides new insight on the atmospheric features generating rainfall CDFs. We apply both approaches to geopotential heights over western Europe in view of assessing 3-day rainfall accumulations over the Isère River catchment at Grenoble, France. Results show that dimensional predictors are the most skillful features for predicting 3-day rainfall—bringing alone 60% of the predictability of the classical analogy approach—whereas the dynamical predictors are less explicative. These results open new directions of research that the classical analogy approach cannot handle. They show, for instance, that both dry sequences and strong rainfall sequences are associated with singular 500-hPa geopotential shapes acting as local attractors—a way of explaining the change in rainfall CDFs in a changing climate.

scholarly journals Characterizing Large-Scale Circulations Driving Extreme Precipitation in the Northern French Alps

2021 ◽  
Author(s):  
Antoine Blanc ◽  
Juliette Blanchet ◽  
Jean-Dominique Creutin
Keyword(s):  
High Pressure ◽  
Pattern Classification ◽  
Extreme Precipitation ◽  
Large Scale ◽  
Western Europe ◽  
Medium Size ◽  
Moist Air ◽  
Southern France ◽  
French Alps ◽  
The Mediterranean

<p>Extreme precipitation in the Northern French Alps are mainly associated with large-scale circulations (LSCs) bringing moist air from the Atlantic Ocean and the Mediterranean Sea - two atmospheric influences that are very frequent in the climatology. In this work, we investigate what characterizes the Atlantic/Mediterranean circulations driving extreme precipitation in the Northern French Alps in comparison to "random" Atlantic/Mediterranean circulations. We focus on extreme 3-day precipitation over two medium size neighboring catchments from 1950 to 2017. Atlantic and Mediterranean circulations are identified using an existing weather pattern classification established for Southern France. Every single LSC is characterized using three atmospheric descriptors based on analogy in geopotential shapes at 500hPa over Western Europe that were introduced in previous works. They are i) the celerity, characterizing the stationary nature of a geopotential shape, and ii) the singularity and relative singularity, characterizing the resemblance of a geopotential shape to its analogs, in other words the way this geopotential shape is closely reproduced in the climatology. We add to these analogy-based descriptors a new (non analogy) descriptor accounting for the strength of the low and high pressure systems. We show that Atlantic/Mediterranean circulations driving extreme 3-day precipitation in the Northern French Alps are the Atlantic/Mediterranean circulations featuring the strongest centers of action as well as the most stationary and the most reproducible geopotential shapes - characteristics that are rare for both atmospheric influences. In the Atlantic case, these characteristics appear to be even more pronounced and rare with regard to the whole climatology, pointing LSC as an important driver of extreme precipitation. In the Mediterranean case, these characteristics appear to be more random with regard to the whole climatology, pointing a more balanced contribution between specific LSC and humidity in driving extreme precipitation.</p>

scholarly journals Trends and variability in extreme precipitation indices over Maghreb countries

2013 ◽  
Vol 1 (4) ◽  
pp. 3625-3658 ◽  
Author(s):  
Y. Tramblay ◽  
S. El Adlouni ◽  
E. Servat
Keyword(s):  
Atmospheric Circulation ◽  
Large Scale ◽  
Heavy Precipitation ◽  
Climate Indices ◽  
Atmospheric Circulation Patterns ◽  
Circulation Patterns ◽  
Precipitation Indices ◽  
Precipitation Records ◽  
Mediterranean Oscillation ◽  
Large Scale Atmospheric Circulation

Abstract. Maghreb countries located in North Africa are highly vulnerable to extreme hydrological events, such as floods and droughts, driven by the strong variability of precipitation. While several studies have analyzed the presence of trends in precipitation records for the Euro-Mediterranean Basin, this study provides the first regional assessment of trends on its southernmost shores. A database of 22 stations located in Algeria, Morocco and Tunisia with between 33 and 59 yr of daily precipitation records is considered. The change points and trends are analyzed for eleven climate indices describing several features of the precipitation regime. The issue of conducting multiple hypothesis tests is addressed through the implementation of a false discovery rate procedure. The spatial and inter-annual variability of the precipitation indices at the different stations are analyzed and compared with large scale atmospheric circulation patterns, including the North Atlantic Oscillation (NAO), Western Mediterranean Oscillation (WEMO), Mediterranean Oscillation (MO) and El Niño Southern Oscillation (ENSO). Results show a strong tendency towards a decrease of precipitation totals and wet days together with an increase in the duration of dry periods, mainly for Morocco and western Algeria. On the opposite, only a few significant trends are detected for heavy precipitation indices. The NAO and MO patterns are well correlated with precipitation indices describing precipitation amounts, the number of dry days and the length of wet and dry periods, whereas heavy precipitation indices exhibit a strong spatial variability and are only moderately correlated with large scale atmospheric circulation patterns.

scholarly journals Linking Large-scale Circulation Descriptors to Precipitation Variability in the Northern French Alps

2021 ◽  
Author(s):  
Antoine Blanc ◽  
Juliette Blanchet ◽  
Jean-Dominique Creutin
Keyword(s):  
Pressure Difference ◽  
Large Scale ◽  
Western Europe ◽  
Precipitation Variability ◽  
Medium Size ◽  
Maximum Pressure ◽  
Large Scale Circulation ◽  
French Alps ◽  
Mountainous Catchment ◽  
The North

<p>This work analyses the link between Western Europe large-scale circulation and precipitation variability in the Northern French Alps from 1950 to 2017. We consider simple descriptors characterizing the daily 500hPa geopotential height fields. They are the Maximum Pressure Difference - representing the range of geopotential heights over Western Europe -, and the singularity - representing the mean distance between a geopotential shape and its closest analogs, i.e. the way this geopotential shape is reproduced in the climatology. These descriptors are compared to the occurrence of different atmospheric influences - Atlantic, Mediterranean, Northeast, Anticyclonic - and to the leading mode of large-scale circulation variability over Europe - the North Atlantic Oscillation (NAO) - for explaining precipitation variability in the Isère River catchment from one day to 10 years. We show that the Maximum Pressure Difference and the singularity of geopotential shapes explain a significant part of precipitation variability in the Northern French Alps from 10 days to 10 years, especially in winter (correlation values of 0.7). These descriptors provide much better performance than NAO and the same performance as the occurrence of the Atlantic influence, which is the best performing atmospheric influence. This means that simple characteristics of large-scale circulation - that are easy to implement - provide as much information as weather pattern classification to explain precipitation variability over a medium size mountainous catchment. Furthermore, we show that NAO does not drive the pressure gradient in a domain spreading from the Iberic Peninsula to Southern Great Britain and weakly explains precipitation variability in the Northern French Alps.</p>

Linking Large-scale Circulation Descriptors to Precipitation Variability in the Northern French Alps

2021 ◽  
Author(s):  
Antoine Blanc ◽  
Juliette Blanchet ◽  
Jean-Dominique Creutin
Keyword(s):  
Pressure Difference ◽  
Large Scale ◽  
Western Europe ◽  
Precipitation Variability ◽  
Maximum Pressure ◽  
Large Scale Circulation ◽  
French Alps ◽  
The North ◽  
Height Fields ◽  
The North Atlantic Oscillation

<p>This work analyses the link between Western Europe large-scale circulation and precipitation variability in the Northern French Alps from 1950 to 2017. We consider simple descriptors characterizing the daily 500hPa geopotential height fields. They are the Maximum Pressure Difference - representing the range of geopotential heights over Western Europe -, and the singularity - representing the mean distance between a geopotential shape and its closest analogs, i.e. the way this geopotential shape is reproduced in the climatology. These descriptors are compared to the occurrence of different atmospheric influences - Atlantic, Mediterranean, Northeast, Anticyclonic - and to the leading mode of large-scale circulation variability over Europe - the North Atlantic Oscillation (NAO) - for explaining precipitation variability in the Isère River catchment from one day to 10 years. We show that the Maximum Pressure Difference and the singularity of geopotential shapes explain a significant part of precipitation variability in the Northern French Alps from 10 days to 10 years, especially in winter (correlation values of 0.7). These descriptors provide much better performance than NAO and the same performance as the occurrence of the Atlantic influence, which is the best performing atmospheric influence. This means that simple characteristics of large-scale circulation - that are easy to implement - provide as much information as weather pattern classification to explain precipitation variability in the Northern French Alps.</p>

Going the Distance

2020 ◽  
Author(s):  
Ron Harris
Keyword(s):  
Large Scale ◽  
Western Europe ◽  
Family Firms ◽  
Global Trade ◽  
Long Distance ◽  
Business Corporation ◽  
Modern Economy ◽  
Key Factor ◽  
Silk Route ◽  
Passive Investors

Before the seventeenth century, trade across Eurasia was mostly conducted in short segments along the Silk Route and Indian Ocean. Business was organized in family firms, merchant networks, and state-owned enterprises, and dominated by Chinese, Indian, and Arabic traders. However, around 1600 the first two joint-stock corporations, the English and Dutch East India Companies, were established. This book tells the story of overland and maritime trade without Europeans, of European Cape Route trade without corporations, and of how new, large-scale, and impersonal organizations arose in Europe to control long-distance trade for more than three centuries. It shows that by 1700, the scene and methods for global trade had dramatically changed: Dutch and English merchants shepherded goods directly from China and India to northwestern Europe. To understand this transformation, the book compares the organizational forms used in four major regions: China, India, the Middle East, and Western Europe. The English and Dutch were the last to leap into Eurasian trade, and they innovated in order to compete. They raised capital from passive investors through impersonal stock markets and their joint-stock corporations deployed more capital, ships, and agents to deliver goods from their origins to consumers. The book explores the history behind a cornerstone of the modern economy, and how this organizational revolution contributed to the formation of global trade and the creation of the business corporation as a key factor in Europe's economic rise.

Sign in / Sign up

Export Citation Format

Share Document