scholarly journals Climatology of Lyapunov exponents: The influence of atmospheric rivers on large-scale mixing variability

2017 ◽  
Author(s):  
Daniel Garaboa-Paz ◽  
Jorge Eiras-Barca ◽  
Vicente Pérez-Muñuzuri
Keyword(s):  
Lyapunov Exponents ◽  
Large Scale ◽  
Southern Oscillation ◽  
Baroclinic Instability ◽  
Storm Track ◽  
Wind Fields ◽  
Atmospheric Rivers ◽  
Finite Time Lyapunov Exponents ◽  
Large Correlation ◽  
Large Ensembles

Abstract. Large-scale tropospheric mixing and Lagrangian transport properties have been analyzed for a long-term period 1979–2014 in terms of the finite-time Lyapunov exponents (FTLE). Wind fields reanalysis from the European Centre for Medium-Range Weather Forecasts were used to calculate Lagrangian trajectories of large ensembles of particles. The FTLE climatology shows large correlation values with the baroclinic instability growth rate. Larger values of the inter and intra-annual mixing variabilities highlight El Niño Southern Oscillation, the storm track or the Intertropical Convergence Zone among other large-scale structures. As a case study, the role that atmospheric rivers have on the large-scale atmospheric mixing and the precipitation rates observed in the Sahara-Morocco and British Isles regions have been analyzed. Atmospheric rivers contribution to tropospheric mixing is found to decrease from 15 % in Sahara-Morocco to less than 5 % for UK-Ireland regions, in agreement to their contribution to precipitation that is 40 % larger in the former than for the latter region.

scholarly journals Climatology of Lyapunov exponents: the link between atmospheric rivers and large-scale mixing variability

2017 ◽  
Vol 8 (3) ◽  
pp. 865-873 ◽  
Author(s):  
Daniel Garaboa-Paz ◽  
Jorge Eiras-Barca ◽  
Vicente Pérez-Muñuzuri
Keyword(s):  
Lyapunov Exponents ◽  
Large Scale ◽  
Southern Oscillation ◽  
Baroclinic Instability ◽  
Storm Track ◽  
Atmospheric Rivers ◽  
Atmospheric River ◽  
Large Ensembles ◽  
The Mean ◽  
The Uk

Abstract. Large-scale tropospheric mixing and Lagrangian transport properties have been analyzed for the long-term period 1979–2014 in terms of the finite-time Lyapunov exponents (FTLEs). Wind field reanalyses from the European Centre for Medium-Range Weather Forecasts were used to calculate the Lagrangian trajectories of large ensembles of particles. Larger values of the interannual and intra-annual mixing variabilities highlight the El Niño Southern Oscillation, the storm track, or the Intertropical Convergence Zone among other large-scale structures. The mean baroclinic instability growth rate and the mean atmospheric river occurrence show large correlation values with the FTLE climatology as an indication of their influence on tropospheric mixing in the midlatitudes. As a case study, the role that land-falling atmospheric rivers have on large-scale tropospheric mixing and the precipitation rates observed in Saharan Morocco and the British Isles has been analyzed. The atmospheric river contribution to tropospheric mixing is found to decrease from 15 % in Saharan Morocco to less than 5 % for the UK and Ireland regions, in agreement with their contribution to precipitation that is 40 % larger in the former than in the latter region.

scholarly journals Influence of finite-time Lyapunov exponents on winter precipitation over the Iberian Peninsula

2017 ◽  
Vol 24 (2) ◽  
pp. 227-235 ◽  
Author(s):  
Daniel Garaboa-Paz ◽  
Nieves Lorenzo ◽  
Vicente Pérez-Muñuzuri
Keyword(s):  
Iberian Peninsula ◽  
Lyapunov Exponents ◽  
Finite Time ◽  
Large Scale ◽  
Winter Precipitation ◽  
Seasonal Forecasts ◽  
Sea Level Pressure ◽  
Teleconnection Patterns ◽  
Finite Time Lyapunov Exponents ◽  
Eastern Atlantic Ocean

Abstract. Seasonal forecasts have improved during the last decades, mostly due to an increase in understanding of the coupled ocean–atmosphere dynamics, and the development of models able to predict the atmosphere variability. Correlations between different teleconnection patterns and severe weather in different parts of the world are constantly evolving and changing. This paper evaluates the connection between winter precipitation over the Iberian Peninsula and the large-scale tropospheric mixing over the eastern Atlantic Ocean. Finite-time Lyapunov exponents (FTLEs) have been calculated from 1979 to 2008 to evaluate this mixing. Our study suggests that significant negative correlations exist between summer FTLE anomalies and winter precipitation over Portugal and Spain. To understand the mechanisms behind this correlation, summer anomalies of the FTLE have also been correlated with other climatic variables such as the sea surface temperature (SST), the sea level pressure (SLP) or the geopotential. The East Atlantic (EA) teleconnection index correlates with the summer FTLE anomalies, confirming their role as a seasonal predictor for winter precipitation over the Iberian Peninsula.

Simulations of Atmospheric Rivers, Their Variability, and Response to Global Warming Using GFDL’s New High-Resolution General Circulation Model

2020 ◽  
Vol 33 (23) ◽  
pp. 10287-10303
Author(s):  
Ming Zhao
Keyword(s):  
Global Warming ◽  
General Circulation ◽  
Large Scale ◽  
Southern Oscillation ◽  
Geographical Location ◽  
Circulation Model ◽  
Teleconnection Pattern ◽  
Width Ratio ◽  
Atmospheric Rivers ◽  
Length Width

AbstractA 50-km-resolution GFDL AM4 well captures many aspects of observed atmospheric river (AR) characteristics including the probability density functions of AR length, width, length–width ratio, geographical location, and the magnitude and direction of AR mean vertically integrated vapor transport (IVT), with the model typically producing stronger and narrower ARs than the ERA-Interim results. Despite significant regional biases, the model well reproduces the observed spatial distribution of AR frequency and AR variability in response to large-scale circulation patterns such as El Niño–Southern Oscillation (ENSO), the Northern and Southern Hemisphere annular modes (NAM and SAM), and the Pacific–North American (PNA) teleconnection pattern. For global warming scenarios, in contrast to most previous studies that show a large increase in AR length and width and therefore the occurrence frequency of AR conditions at a given location, this study shows only a modest increase in these quantities. However, the model produces a large increase in strong ARs with the frequency of category 3–5 ARs rising by roughly 100%–300% K−1. The global mean AR intensity as well as AR intensity percentiles at most percent ranks increases by 5%–8% K−1, roughly consistent with the Clausius–Clapeyron scaling of water vapor. Finally, the results point out the importance of AR IVT thresholds in quantifying modeled AR response to global warming.

scholarly journals Moisture Origin and Meridional Transport in Atmospheric Rivers and Their Association with Multiple Cyclones*

2013 ◽  
Vol 141 (8) ◽  
pp. 2850-2868 ◽  
Author(s):  
Harald Sodemann ◽  
Andreas Stohl
Keyword(s):  
Water Vapor ◽  
North Atlantic ◽  
Large Scale ◽  
Mesoscale Model ◽  
Storm Track ◽  
Conveyor Belt ◽  
Tracer Transport ◽  
Atmospheric Rivers ◽  
The North ◽  
The North Atlantic

Abstract During December 2006 many cyclones traveled across the North Atlantic, causing temperature and precipitation in Norway to be well above average. Large excursions of high vertically integrated water vapor, often referred to as atmospheric rivers, reached from the subtropics to high latitudes, inducing precipitation over western Scandinavia. The sources and transport of atmospheric water vapor in the North Atlantic storm track during that month are examined by means of a mesoscale model fitted with water vapor tracers. Decomposition of the modeled total water vapor field into numerical water vapor tracers tagged by evaporation latitude shows that when an atmospheric river was present, a higher fraction of water vapor from remote, southerly source regions caused more intense precipitation. The tracer transport analysis revealed that the atmospheric rivers were composed of a sequence of meridional excursions of water vapor, in close correspondence with the upper-level flow configuration. In cyclone cores, fast turnover of water vapor by evaporation and condensation were identified, leading to a rapid assimilation of water from the underlying ocean surface. In the regions of long-range transport, water vapor tracers from the southern midlatitudes and subtropics dominated over local contributions. By advection of water vapor along their trailing cold fronts cyclones were reinforcing the atmospheric rivers. At the same time the warm conveyor belt circulation was feeding off the atmospheric rivers by large-scale ascent and precipitation. Pronounced atmospheric rivers could persist in the domain throughout more than one cyclone's life cycle. These findings emphasize the interrelation between midlatitude cyclones and atmospheric rivers but also their distinction from the warm conveyor belt airstream.

scholarly journals Winter And Spring Atmospheric Rivers In High Mountain Asia: Climatology, Dynamics, And Variability

2021 ◽  
Author(s):  
Deanna Nash ◽  
Leila M.V. Carvalho ◽  
Charles Jones ◽  
Qinghua Ding
Keyword(s):  
Large Scale ◽  
Southern Oscillation ◽  
Wave Train ◽  
Water Vapor Transport ◽  
High Mountain ◽  
Spring Precipitation ◽  
Atmospheric Rivers ◽  
Teleconnection Patterns ◽  
Westerly Jet ◽  
Upper Level

Abstract Atmospheric Rivers (ARs) that reach the complex terrain of High Mountain Asia (HMA) cause significant hydrological impacts for millions of people. While ARs are often associated with precipitation extremes and can cause floods and debris flows affecting populated communities, little is known about ARs that reach as far inland as HMA. This paper characterizes AR types and investigates dynamical mechanisms associated with the development of ARs that typically affect HMA. Combined empirical orthogonal function (cEOF) analysis using integrated water vapor transport (IVT) is applied to days where an AR reaches HMA. K-means cluster analysis applied to the first two principal components uncovered three subtypes of AR events with distinct synoptic characteristics during winter and spring months. The first subtype increases precipitation and IVT in the Karakoram and is associated with a zonally oriented wave train propagating within the westerly jet waveguide. The second subtype is associated with enhanced southwesterly IVT, anomalous upper-level cyclonic circulation centered on 45°E, and precipitation in the Pamirs. The third subtype shows anomalous precipitation in the Eastern Himalayas and southwesterly IVT across the Bay of Bengal. Interannual variations in the frequency of HMA ARs and relationships with various teleconnection patterns show that western HMA AR subtypes are sensitive to well-known remote large-scale climate factors, such as the El Niño Southern Oscillation, Arctic Oscillation, and the Siberian High. These results provide synoptic characterization of the three types of ARs that reach HMA and reveal the previously unexplored significance of their contribution to winter and spring precipitation.

scholarly journals Drivers and Impacts of Atmospheric Rivers in New Zealand

2021 ◽  
Author(s):  
◽  
Daemon Kennett
Keyword(s):  
New Zealand ◽  
Water Vapour ◽  
Large Scale ◽  
Southern Oscillation ◽  
Daily Rainfall ◽  
Seasonal Forecasts ◽  
Positive Role ◽  
Atmospheric Rivers ◽  
Synoptic Conditions ◽  
Climate Patterns

<p><b>Atmospheric Rivers (ARs) are long, narrow jets of intense water vapour flux that are a fundamental component of the global atmospheric circulation, transporting moisture and heat from the tropics to higher latitudes. When an AR makes landfall, especially in areas of steep topography, it releases much of its water vapour as precipitation through orographic uplift. Thus, although ARs play a positive role in the distribution and maintenance of water resources in the mid-latitudes, they are also associated with extreme precipitation and flooding. AR events in New Zealand have had major socio-economic consequences with losses to property, farmland, stock, roads and bridges. However, despite knowledge of their occurrence, focused investigations of ARs in New Zealand have received relatively little scientific attention. In particular, little is known about how large-scale climate patterns, such as the Southern Annular Mode (SAM) and El Niño-Southern Oscillation (ENSO), influence ARs and AR-related precipitation extremes.</b></p> <p>The aim of this study is to quantify the impacts and large-scale drivers of AR landfalls in New Zealand. We employ a new AR detection algorithm, developed specifically for the New Zealand case, to investigate landfalling ARs over a 41-year period from 1979-2019. We investigate the general climatology of ARs, and evaluate the synoptic conditions that drive these events. Using a comprehensive daily rainfall dataset comprising 189 stations, we also investigate the impacts of ARs on NZ rainfall and flooding events. For northern and western regions, over 45% of rainfall fell directly under AR conditions, contributing to daily rainfall totals 2.5 times higher on average compared to non-AR days. Further, we find that AR days were associated with up to 70% of daily rainfall totals above the 99th percentile, with insurance damages exceeding NZ $1.4 billion since 1980.</p> <p>Finally, for the first time in New Zealand, we investigate how large-scale climate patterns influence the occurrence of ARs. We find that changes in the leading modes of climate variability can alter seasonal and regional AR frequency by upwards of 30%. The SAM is identified as the dominant driver of AR activity (other than the seasonal cycle), with the positive SAM phase associated with a 16% reduction in AR occurrence during summer (30-35% reduction for the North Island). The links between AR occurrence and ENSO were less clear, though a few statistically significant relationships were found. The Madden-Julian Oscillation (MJO), the leading mode of intraseasonal tropical variability, was found to significantly influence the frequency and timing of AR landfalls (particularly for the northern North Island). Favourable MJO phases were associated with positive AR frequency anomalies +60% above the mean. These results demonstrate potential use of the AR framework in skilful subseasonal-to-seasonal forecasts of extreme rainfall in New Zealand.</p>

scholarly journals Drivers and Impacts of Atmospheric Rivers in New Zealand

2021 ◽  
Author(s):  
◽  
Daemon Kennett
Keyword(s):  
New Zealand ◽  
Water Vapour ◽  
Large Scale ◽  
Southern Oscillation ◽  
Daily Rainfall ◽  
Seasonal Forecasts ◽  
Positive Role ◽  
Atmospheric Rivers ◽  
Synoptic Conditions ◽  
Climate Patterns

<p><b>Atmospheric Rivers (ARs) are long, narrow jets of intense water vapour flux that are a fundamental component of the global atmospheric circulation, transporting moisture and heat from the tropics to higher latitudes. When an AR makes landfall, especially in areas of steep topography, it releases much of its water vapour as precipitation through orographic uplift. Thus, although ARs play a positive role in the distribution and maintenance of water resources in the mid-latitudes, they are also associated with extreme precipitation and flooding. AR events in New Zealand have had major socio-economic consequences with losses to property, farmland, stock, roads and bridges. However, despite knowledge of their occurrence, focused investigations of ARs in New Zealand have received relatively little scientific attention. In particular, little is known about how large-scale climate patterns, such as the Southern Annular Mode (SAM) and El Niño-Southern Oscillation (ENSO), influence ARs and AR-related precipitation extremes.</b></p> <p>The aim of this study is to quantify the impacts and large-scale drivers of AR landfalls in New Zealand. We employ a new AR detection algorithm, developed specifically for the New Zealand case, to investigate landfalling ARs over a 41-year period from 1979-2019. We investigate the general climatology of ARs, and evaluate the synoptic conditions that drive these events. Using a comprehensive daily rainfall dataset comprising 189 stations, we also investigate the impacts of ARs on NZ rainfall and flooding events. For northern and western regions, over 45% of rainfall fell directly under AR conditions, contributing to daily rainfall totals 2.5 times higher on average compared to non-AR days. Further, we find that AR days were associated with up to 70% of daily rainfall totals above the 99th percentile, with insurance damages exceeding NZ $1.4 billion since 1980.</p> <p>Finally, for the first time in New Zealand, we investigate how large-scale climate patterns influence the occurrence of ARs. We find that changes in the leading modes of climate variability can alter seasonal and regional AR frequency by upwards of 30%. The SAM is identified as the dominant driver of AR activity (other than the seasonal cycle), with the positive SAM phase associated with a 16% reduction in AR occurrence during summer (30-35% reduction for the North Island). The links between AR occurrence and ENSO were less clear, though a few statistically significant relationships were found. The Madden-Julian Oscillation (MJO), the leading mode of intraseasonal tropical variability, was found to significantly influence the frequency and timing of AR landfalls (particularly for the northern North Island). Favourable MJO phases were associated with positive AR frequency anomalies +60% above the mean. These results demonstrate potential use of the AR framework in skilful subseasonal-to-seasonal forecasts of extreme rainfall in New Zealand.</p>

scholarly journals Winter and spring atmospheric rivers in High Mountain Asia: climatology, dynamics, and variability

2021 ◽  
Author(s):  
Deanna Nash ◽  
Leila M. V. Carvalho ◽  
Charles Jones ◽  
Qinghua Ding
Keyword(s):  
Large Scale ◽  
Southern Oscillation ◽  
Wave Train ◽  
Water Vapor Transport ◽  
High Mountain ◽  
Spring Precipitation ◽  
Atmospheric Rivers ◽  
Teleconnection Patterns ◽  
Westerly Jet ◽  
Upper Level

AbstractAtmospheric rivers (ARs) that reach the complex terrain of High Mountain Asia (HMA) cause significant hydrological impacts for millions of people. While ARs are often associated with precipitation extremes and can cause floods and debris flows affecting populated communities, little is known about ARs that reach as far inland as HMA. This paper characterizes AR types and investigates dynamical mechanisms associated with the development of ARs that typically affect HMA. Combined empirical orthogonal function (cEOF) analysis using integrated water vapor transport (IVT) is applied to days where an AR reaches HMA. K-means cluster analysis applied to the first two principal components uncovered three subtypes of AR events with distinct synoptic characteristics during winter and spring months. The first subtype increases precipitation and IVT in Western HMA and is associated with a zonally oriented wave train propagating within the westerly jet waveguide. The second subtype is associated with enhanced southwesterly IVT, anomalous upper-level cyclonic circulation centered on 45$$^\circ $$ ∘ E, and precipitation in Northwestern HMA. The third subtype shows anomalous precipitation in Eastern HMA and southwesterly IVT across the Bay of Bengal. Interannual variations in the frequency of HMA ARs and relationships with various teleconnection patterns show that western HMA AR subtypes are sensitive to well-known remote large-scale climate factors, such as the El Niño Southern Oscillation, Arctic Oscillation, and the Siberian High. These results provide synoptic characterization of the three types of ARs that reach HMA and reveal the previously unexplored significance of their contribution to winter and spring precipitation.

scholarly journals Seasonal predictability of the winter precipitation over Iberian Peninsula and its relationship with finite-time Lyapunov exponents

2016 ◽  
Author(s):  
Daniel Garaboa-Paz ◽  
Nieves Lorenzo ◽  
Vicente Pérez-Muñuzuri
Keyword(s):  
Iberian Peninsula ◽  
Lyapunov Exponents ◽  
Finite Time ◽  
Large Scale ◽  
Winter Precipitation ◽  
Seasonal Forecasts ◽  
Sea Level Pressure ◽  
Teleconnection Patterns ◽  
Finite Time Lyapunov Exponents ◽  
Eastern Atlantic Ocean

Abstract. Seasonal forecasts have improved during the last decades, mostly due to an increase of understanding of the coupled ocean-atmosphere dynamics, and the development of models able to predict the atmosphere variability. Correlations between different teleconnection patterns and severe weather in different parts of the world have also evolved during the last years. This paper evaluates the connection between winter precipitation over the Iberian Peninsula and the large-scale tropospheric mixing over the eastern Atlantic ocean. Finite-time Lyapunov exponents (FTLE) have been calculated from 1979 to 2008 to evaluate this mixing. Our study suggests that significant negative correlations exist between summer FTLE anomalies and winter precipitation over Portugal and Spain. To understand the mechanisms behind this correlation, summer anomalies of the FTLE have also been correlated to other circulation and temperature patterns as the sea surface temperature (SST), the sea level pressure (SLP) or the geopotential. The East Atlantic (EA) teleconnection index correlates with the summer FTLE anomalies confirming their role as a seasonal predictor for winter precipitation over the Iberian Peninsula.

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