scholarly journals Dynamics of Landfalling Atmospheric Rivers over the North Pacific in 30 Years of MERRA Reanalysis

2014 ◽  
Vol 27 (18) ◽  
pp. 7133-7150 ◽  
Author(s):  
Ashley E. Payne ◽  
Gudrun Magnusdottir
Keyword(s):  
Rossby Wave ◽  
West Coast ◽  
Wave Breaking ◽  
Moisture Transport ◽  
Large Scale ◽  
Eastern Pacific ◽  
The West ◽  
Atmospheric Rivers ◽  
Rossby Wave Breaking ◽  
Upper Level

Abstract A large-scale analysis of landfalling atmospheric rivers (ARs) along the west coast of North America and their association with the upper-tropospheric flow is performed for the extended winter (November–March) for the years 1979–2011 using Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis data. The climatology, relationship to the El Niño–Southern Oscillation and the Madden–Julian oscillation, and upper-level characteristics of approximately 750 landfalling ARs are presented based on the 85th percentile of peak daily moisture flux. AR occurrence along the West Coast is dominated by early season events. In composites of upper-level fields during AR occurrences, certain characteristics stand out irrespective of the tropical climate indices. This suggests that extratropical dynamical processes play a key role in AR dynamics. The influence of the large-scale circulation on AR intensity prior to landfall is examined by objectively selecting an extreme subset of 112 landfalling AR dates representing the 95th percentile of strongest cases. Each landfalling AR date that is identified is traced backward in time using a novel semiautomated tracking algorithm based on spatially and temporally connected organized features in integrated moisture transport. Composites of dynamical fields following the eastward progression of ARs show a close relationship of the location of the jet, Rossby wave propagation, and anticyclonic Rossby wave breaking in the upper troposphere of the eastern Pacific and moisture transport in the lower troposphere. Comparison between the strongest and the weakest ARs within the most extreme subset shows differences in both the intensity of moisture transport and the scale and development of anticyclonic Rossby wave breaking in the eastern Pacific.

scholarly journals A global climatological perspective on the importance of Rossby wave breaking and intense moisture transport for extreme precipitation events

2021 ◽  
Author(s):  
Andries Jan De Vries
Keyword(s):  
Rossby Wave ◽  
Extreme Precipitation ◽  
Wave Breaking ◽  
Moisture Transport ◽  
Synoptic Scale ◽  
Rossby Wave Breaking ◽  
Extreme Precipitation Events ◽  
The World ◽  
Upper Level ◽  
Precipitation Events

<p>Extreme precipitation events (EPEs) frequently cause flooding with dramatic socioeconomic impacts in many parts of the world. Previous studies considered two synoptic-scale processes, Rossby wave breaking and intense moisture transport, typically in isolation, and their linkage to such EPEs in several regions. This study presents for the first time a global and systematic climatological analysis of these two synoptic-scale processes, in tandem and in isolation, for the occurrence of EPEs. To this end, we use 40-year ERA-Interim reanalysis data (1979-2018) and apply object-based identification methods for (i) daily EPEs, (ii) stratospheric potential vorticity (PV) streamers as indicators of Rossby wave breaking, and (iii) structures of high vertically integrated horizontal water vapor transport (IVT). First, the importance of these two synoptic-scale processes is demonstrated by case studies of previously documented flood events that inflicted catastrophic impacts in different parts of the world. Next, a climatological quantification shows that Rossby wave breaking is associated with > 90 % of EPEs near high topography and over the Mediterranean, whereas intense moisture transport is linked to > 95 % of EPEs over many coastal zones, consistent with findings of atmospheric river-related studies. Combined Rossby wave breaking and intense moisture transport contributes up to 70 % of EPEs in several subtropical and extratropical regions, including (semi)arid desert regions where tropical-extratropical interactions are of key importance for (heavy) rainfall. A detailed analysis shows that five categories with different combinations of wave breaking and intense moisture transport can reflect a large range of EPE-related weather systems across various climate zones. Odds ratios of EPEs linked to the two synoptic-scale processes suggest that intense moisture transport is stronger associated with the occurrence of EPEs than wave breaking. Furthermore, the relationship between the PV and IVT characteristics and the precipitation volumes shows that the depth of the wave breaking and moisture transport intensity are intimately connected with the extreme precipitation severity. Finally, composites reveal that subtropical and extratropical EPEs, linked to Rossby wave breaking, go along with the formation of upper-level troughs and cyclogenetic processes near the surface downstream, reduced static stability beneath the upper-level forcing (only over water), and dynamical lifting ahead (over water and land). This study concludes with a concept that reconciles well-established meteorological principles with the importance of Rossby wave breaking and intense moisture transport for extreme precipitation events. The findings of this study may contribute to an improved understanding of the atmospheric processes that lead to EPEs, and may find application in climatic studies on extreme precipitation changes in a warming climate.</p>

scholarly journals A global climatological perspective on the importance of Rossby wave breaking and intense moisture transport for extreme precipitation events

2020 ◽  
Author(s):  
Andries Jan De Vries
Keyword(s):  
Rossby Wave ◽  
Extreme Precipitation ◽  
Wave Breaking ◽  
Moisture Transport ◽  
Synoptic Scale ◽  
Rossby Wave Breaking ◽  
Extreme Precipitation Events ◽  
Upper Level ◽  
High Topography ◽  
Precipitation Events

Abstract. Extreme precipitation events (EPEs) cause frequently flooding with dramatic socioeconomic impacts in many parts of the world. Previous studies considered two synoptic-scale processes, Rossby wave breaking and intense moisture transport, typically in isolation, and their linkage to such EPEs in several regions. This study presents for the first time a global and systematic climatological analysis of these two synoptic-scale processes, in tandem and in isolation, for the occurrence of EPEs. To this end, we use 40-year ERA-Interim reanalysis data (1979–2018) and apply object-based identification methods for (i) daily EPEs, (ii) stratospheric potential vorticity (PV) streamers as indicators of Rossby wave breaking, and (iii) structures of high vertically integrated horizontal water vapor transport (IVT). First, the importance of these two processes is demonstrated by case studies of previously documented flood events that inflicted catastrophic impacts in different parts of the world. Next, a climatological quantification shows that Rossby wave breaking is associated with > 90 % of EPEs near high topography and over the Mediterranean, intense moisture transport is linked to > 90 % of EPEs over many coastal zones, and their combined occurrence contributes to > 70 % of EPEs in several subtropical and extratropical regions. A more detailed analysis shows that a majority of EPEs associated with (1) only Rossby wave breaking are confined to higher-latitude regions that are deprived from remote moisture supplies by high topography and deserts, (2) only intense moisture transport are found circumglobally at the outer tropics, associated with tropical cyclones, tropical easterly waves, and monsoon lows, (3) combined Rossby wave breaking and intense moisture transport dominate a large part of the globe, in particular over dry subtropical regions where tropical-extratropical interactions are of key relevance, (4) remote, far upstream Rossby wave breaking and intense moisture transport occur over mountainous extratropical west coasts, reminiscent of landfalling atmospheric rivers, and (5) neither of the two synoptic-scale processes are concentrated over the inner tropics and high topography at lower latitudes, where EPEs arise under the influence of local forcing. Accordingly, different combinations of wave breaking and intense moisture transport can reflect a large range of weather systems with relevance to EPEs across various climate zones. Furthermore, the relationship between the PV and IVT characteristics and the precipitation volumes shows that the strength of the wave breaking and moisture transport intensity are intimately connected with the extreme precipitation severity. Finally, composites reveal that subtropical and extratropical EPEs, linked to Rossby wave breaking, go along with the formation of upper-level troughs and cyclogenetic processes near the surface downstream, reduced static stability beneath the upper-level forcing (only over water), and dynamical lifting ahead (over water and land). This study concludes with a concept that reconciles well-established meteorological principles with the importance of Rossby wave breaking and intense moisture transport for extreme precipitation events. The findings of this study may contribute to an improved understanding of the atmospheric processes that lead to EPEs, and may find application in climatic studies on extreme precipitation changes in a warming climate.

Characteristics of long-duration heavy precipitation events along the West Coast of the United States

2021 ◽  
Author(s):  
Benjamin J. Moore ◽  
Allen B. White ◽  
Daniel J. Gottas
Keyword(s):  
Rossby Wave ◽  
West Coast ◽  
Bering Sea ◽  
North Pacific ◽  
Wave Breaking ◽  
Heavy Precipitation ◽  
The West ◽  
Rossby Wave Breaking ◽  
Long Duration ◽  
Precipitation Events

AbstractProlonged periods (e.g., several days or more) of heavy precipitation can result in sustained high-impact flooding. Herein, an investigation of long-duration heavy precipitation events (HPEs), defined as periods comprising ≥ 3 days with precipitation exceeding the climatological 95th percentile, is conducted for 1979–2019 for the U.S. West Coast, specifically Northern California. An objective flow-based categorization method is applied to identify principal large-scale flow patterns for the events. Four categories are identified and examined through composite analyses and case studies. Two of the categories are characterized by a strong zonal jet stream over the eastern North Pacific, while the other two are characterized by atmospheric blocking over the central North Pacific and the Bering Sea–Alaska region, respectively. The composites and case studies demonstrate that the flow patterns for the HPEs tend to remain in place for several days, maintaining strong baroclinicity and promoting occurrences of multiple cyclones in rapid succession near the West Coast. The successive cyclones result in persistent water vapor flux and forcing for ascent over Northern California, sustaining heavy precipitation. For the zonal jet patterns, cyclones affecting the West Coast tend to occur in the poleward jet exit region in association with cyclonic Rossby wave breaking. For the blocking patterns, cyclones tend to occur in association with anticyclonic Rossby wave breaking on the downstream flank of the block. For Bering Sea–Alaska blocking cases, cyclones can move into this region in conjunction with cyclonically breaking waves that extend into the eastern North Pacific from the upstream flank of the block.

scholarly journals A global climatological perspective on the importance of Rossby wave breaking and intense moisture transport for extreme precipitation events

2021 ◽  
Vol 2 (1) ◽  
pp. 129-161
Author(s):  
Andries Jan de Vries
Keyword(s):  
Rossby Wave ◽  
Extreme Precipitation ◽  
Wave Breaking ◽  
Moisture Transport ◽  
Synoptic Scale ◽  
Rossby Wave Breaking ◽  
Extreme Precipitation Events ◽  
The World ◽  
Upper Level ◽  
Precipitation Events

Abstract. Extreme precipitation events (EPEs) frequently cause flooding with dramatic socioeconomic impacts in many parts of the world. Previous studies considered two synoptic-scale processes, Rossby wave breaking and intense moisture transport, typically in isolation, and their linkage to such EPEs in several regions. This study presents for the first time a global and systematic climatological analysis of these two synoptic-scale processes, in tandem and in isolation, for the occurrence of EPEs. To this end, we use 40-year ERA-Interim reanalysis data (1979–2018) and apply object-based identification methods for (i) daily EPEs, (ii) stratospheric potential vorticity (PV) streamers as indicators of Rossby wave breaking, and (iii) structures of high vertically integrated horizontal water vapour transport (IVT). First, the importance of these two synoptic-scale processes is demonstrated by case studies of previously documented flood events that inflicted catastrophic impacts in different parts of the world. Next, a climatological quantification shows that Rossby wave breaking is associated with >90 % of EPEs over central North America and the Mediterranean, whereas intense moisture transport is linked to >95 % of EPEs over many coastal zones, consistent with findings of atmospheric river-related studies. Combined Rossby wave breaking and intense moisture transport contributes up to 70 % of EPEs in several subtropical and extratropical regions, including (semi)arid desert regions where tropical–extratropical interactions are of key importance for (heavy) rainfall. Odds ratios of EPEs linked to the two synoptic-scale processes suggest that intense moisture transport has a stronger association with the occurrence of EPEs than Rossby wave breaking. Furthermore, the relationship between the PV and IVT characteristics and the precipitation volumes shows that the depth of the wave breaking and moisture transport intensity are intimately connected with the extreme precipitation severity. Finally, composites reveal that subtropical and extratropical EPEs, linked to Rossby wave breaking, go along with the formation of upper-level troughs and cyclogenetic processes near the surface downstream, reduced static stability beneath the upper-level forcing (only over water), and dynamical lifting ahead (over water and land). This study concludes with a concept that reconciles well-established meteorological principles with the importance of Rossby wave breaking and intense moisture transport for the formation of EPEs. Another conclusion with major implications is that different combinations of Rossby wave breaking and intense moisture transport can reflect a large range of EPE-related weather systems across climate zones and can thus form the basis for a new classification of EPE regimes. The findings of this study may contribute to an improved understanding of the atmospheric processes that lead to EPEs and may find application in climatic studies on extreme precipitation changes in a warming climate.

Method for Identifying and Clustering Rossby Wave Breaking Events in the Northern Hemisphere

2021 ◽  
pp. 17-28
Author(s):  
A. V. Gochakov ◽  
◽  
O. Yu. Antokhina ◽  
V. N. Krupchatnikov ◽  
Yu. V. Martynova ◽  
...  
Keyword(s):  
Rossby Wave ◽  
Potential Vorticity ◽  
Wave Breaking ◽  
Large Scale ◽  
Method Development ◽  
Spatial Clustering ◽  
Potential Temperature ◽  
Reanalysis Data ◽  
Rossby Wave Breaking ◽  
Dynamic Phenomena

Many large-scale dynamic phenomena in the Earth’s atmosphere are associated with the processes of propagation and breaking of Rossby waves. A new method for identifying the Rossby wave breaking (RWB) is proposed. It is based on the detection of breakings centers by analyzing the shape of the contours of potential vorticity or temperature on quasimaterial surfaces: isentropic and iserthelic (surfaces of constant Ertel potential vorticity (PV)), with further RWB center clustering to larger regions. The method is applied to the set of constant PV levels (0.3 to 9.8 PVU with a step of 0.5 PVU) at the level of potential temperature of 350 K for 12:00 UTC. The ERA-Interim reanalysis data from 1979 to 2019 are used for the method development. The type of RWB (cyclonic/anticyclonic), its area and center are determined by analyzing the vortex geometry at each PV level for every day. The RWBs obtained at this stage are designated as elementary breakings. Density-Based Spatial Clustering of Applications with Noise algorithm (DBSCAN) was applied to all elementary breakings for each month. As a result, a graphic dataset describing locations and dynamics of RWBs for every month from 1979 to 2019 is formed. The RWB frequency is also evaluated for each longitude, taking into account the duration of each RWB and the number of levels involved, as well as the anomalies of these parameters.

scholarly journals Dynamical Evolution of North Atlantic Ridges and Poleward Jet Stream Displacements

2011 ◽  
Vol 68 (5) ◽  
pp. 954-963 ◽  
Author(s):  
Tim Woollings ◽  
Joaquim G. Pinto ◽  
João A. Santos
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Wave Breaking ◽  
Large Scale ◽  
Wave Train ◽  
Jet Stream ◽  
Rossby Wave Breaking ◽  
The North ◽  
The North Atlantic ◽  
Circulation Anomalies

Abstract The development of a particular wintertime atmospheric circulation regime over the North Atlantic, comprising a northward shift of the North Atlantic eddy-driven jet stream and an associated strong and persistent ridge in the subtropics, is investigated. Several different methods of analysis are combined to describe the temporal evolution of the events and relate it to shifts in the phase of the North Atlantic Oscillation and East Atlantic pattern. First, the authors identify a close relationship between northward shifts of the eddy-driven jet, the establishment and maintenance of strong and persistent ridges in the subtropics, and the occurrence of upper-tropospheric anticyclonic Rossby wave breaking over Iberia. Clear tropospheric precursors are evident prior to the development of the regime, suggesting a preconditioning of the Atlantic jet stream and an upstream influence via a large-scale Rossby wave train from the North Pacific. Transient (2–6 days) eddy forcing plays a dual role, contributing to both the initiation and then the maintenance of the circulation anomalies. During the regime there is enhanced occurrence of anticyclonic Rossby wave breaking, which may be described as low-latitude blocking-like events over the southeastern North Atlantic. A strong ridge is already established at the time of wave-breaking onset, suggesting that the role of wave-breaking events is to amplify the circulation anomalies rather than to initiate them. Wave breaking also seems to enhance the persistence, since it is unlikely that a persistent ridge event occurs without being also accompanied by wave breaking.

scholarly journals Linking Atmospheric River Hydrological Impacts on the U.S. West Coast to Rossby Wave Breaking

2017 ◽  
Vol 30 (9) ◽  
pp. 3381-3399 ◽  
Author(s):  
Huancui Hu ◽  
Francina Dominguez ◽  
Zhuo Wang ◽  
David A. Lavers ◽  
Gan Zhang ◽  
...  
Keyword(s):  
United States ◽  
Water Vapor ◽  
Rossby Wave ◽  
West Coast ◽  
Wave Breaking ◽  
The United States ◽  
Rossby Wave Breaking ◽  
Southwest Coast ◽  
Local Topography ◽  
The U.S

Atmospheric rivers (ARs) have significant hydrometeorological impacts on the U.S. West Coast. This study presents the connection between the characteristics of large-scale Rossby wave breaking (RWB) over the eastern North Pacific and the regional-scale hydrological impacts associated with landfalling ARs on the U.S. West Coast (36°–49°N). ARs associated with RWB account for two-thirds of the landfalling AR events and >70% of total AR-precipitation in the winter season. The two regimes of RWB—anticyclonic wave breaking (AWB) and cyclonic wave breaking (CWB)—are associated with different directions of the vertically integrated water vapor transport (IVT). AWB-ARs impinge in a more westerly direction on the coast whereas CWB-ARs impinge in a more southwesterly direction. Most of the landfalling ARs along the northwestern coast of the United States (states of Washington and Oregon) are AWB-ARs. Because of their westerly impinging angles when compared to CWB-ARs, AWB-ARs arrive more orthogonally to the western Cascades and more efficiently transform water vapor into precipitation through orographic lift than CWB-ARs. Consequently, AWB-ARs are associated with the most extreme streamflows in the region. Along the southwest coast of the United States (California), the southwesterly impinging angles of CWB-ARs are more orthogonal to the local topography. Furthermore, the southwest coast CWB-ARs have more intense IVT. Consequently, CWB-ARs are associated with the most intense precipitation. As a result, most of the extreme streamflows in southwest coastal basins are associated with CWB-ARs. In summary, depending on the associated RWB type, ARs impinge on the local topography at a different angle and have a different spatial signature of precipitation and streamflow.

scholarly journals Linking air stagnation in Europe with the synoptic- to large-scale atmospheric circulation

2021 ◽  
Vol 2 (3) ◽  
pp. 675-694
Author(s):  
Jacob W. Maddison ◽  
Marta Abalos ◽  
David Barriopedro ◽  
Ricardo García-Herrera ◽  
Jose M. Garrido-Perez ◽  
...  
Keyword(s):  
Rossby Wave ◽  
Wave Breaking ◽  
Large Scale ◽  
Climate Models ◽  
Large Scale Circulation ◽  
Rossby Wave Breaking ◽  
The North ◽  
Northern Regions ◽  
Climatic Impacts ◽  
Large Scale Atmospheric Circulation

Abstract. The build-up of pollutants to harmful levels can occur when meteorological conditions favour their production or accumulation near the surface. Such conditions can arise when a region experiences air stagnation. The link between European air stagnation, air pollution and the synoptic- to large-scale circulation is investigated in this article across all seasons and the 1979–2018 period. Dynamical indices identifying atmospheric blocking, Rossby wave breaking, subtropical ridges, and the North Atlantic eddy-driven and subtropical jets are used to describe the synoptic- to large-scale circulation as predictors in statistical models of air stagnation and pollutant variability. It is found that the large-scale circulation can explain approximately 60 % of the variance in monthly air stagnation, ozone and wintertime particulate matter (PM) in five distinct regions within Europe. The variance explained by the model does not vary strongly across regions and seasons, apart from for PM when the skill is highest in winter. However, the dynamical indices most related to air stagnation do depend on region and season. The blocking and Rossby wave breaking predictors tend to be the most important for describing air stagnation and pollutant variability in northern regions, whereas ridges and the subtropical jet are more important to the south. The demonstrated correspondence between air stagnation, pollution and the large-scale circulation can be used to assess the representation of stagnation in climate models, which is key for understanding how air stagnation and its associated climatic impacts may change in the future.

Linking air stagnation in Europe with the large-scale atmospheric circulation

2021 ◽  
Author(s):  
Jacob Maddison ◽  
Marta Abalos ◽  
David Barriopedro ◽  
Ricardo Garcia Herrera ◽  
José Manuel Garrido Pérez ◽  
...  
Keyword(s):  
Air Quality ◽  
Health Risks ◽  
Rossby Wave ◽  
Wave Breaking ◽  
Large Scale ◽  
Climate Models ◽  
Large Scale Circulation ◽  
Rossby Wave Breaking ◽  
The North ◽  
Weak Winds

<div>Air stagnation refers to a period when a stable air mass becomes settled over a region and remains quasi-stationary for an extended amount of time. Weak winds in the lower- to mid-troposphere and the absence of precipitation during air stagnation prohibit the ventilation and washout of particles so pollutants can accumulate near the surface. This allows for such pollutants to reach levels harmful to humans, and poses severe health risks. Understanding the development of stagnant conditions is therefore crucial for studying poor air quality and its societal impact. </div><p><br>Here, the linear relationship between European air stagnation and the large-scale circulation is explored across all seasons and during the 1979--2018 period. Dynamical based indices identifying atmospheric blocking, Rossby wave breaking, subtropical ridges, and the North Atlantic eddy-driven and subtropical jets are used to describe the large-scale circulation as predictors in a statistical model of air stagnation variability. It is found that the large-scale circulation can explain approximately 60% of the variance in monthly air stagnation in five distinct regions within Europe. The variance explained by the model does not vary strongly across regions and seasons. However, the dynamical indices most related to air stagnation do depend on region and season. The blocking and Rossby wave breaking predictors tend to be the most important for describing air stagnation variability in northern regions whereas ridges and the subtropical jet are more important to the south. The demonstrated correspondence between air stagnation and the large-scale circulation can be used to assess the representation of air stagnation in climate models, which is key for understanding how air quality and its associated health risks may change in the future.</p>

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