The Relationship Between Extratropical Cyclone Strength and Atmospheric River Intensity and Position

Zhang, Zhenhai; Ralph, F. Martin; Zheng, Minghua

doi:10.1029/2018gl079071

Cited by 142 publications

(163 citation statements)

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“…It is an indicative that the remote moisture sources may have an important contribution to the subtropical cyclone development as previously discussed by Reference [46]. The role of external moisture sources has been emphasized in tropical [47] and extratropical [48,49] cyclogeneses. The moisture travels from its source to the cyclone region like a corridor in the lower atmosphere [48], which is called conveyor belt or atmospheric river.…”

Section: Synoptic Analysismentioning

confidence: 57%

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Key Features and Adverse Weather of the Named Subtropical Cyclones over the Southwestern South Atlantic Ocean

2018

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This work documents the main features of six subtropical cyclones occurred between the years 2010 and 2016 over the southwestern South Atlantic Ocean, near the Brazilian coast, which received names (with the exception of one) from the Brazilian Navy Hydrographic Center. The fine-resolution ERA5 reanalysis and rainfall estimates from the Tropical Rainfall Measuring Mission (TRMM) were used to describe the synoptic environment and the adverse weather conditions during the six events. The support of a small-amplitude trough at mid-levels or a cut-off low, weak vertical wind shear, and moisture flux convergence are the main features contributing to the subtropical cyclogenesis at the surface. On the other hand, sea surface temperature (SST) presents a secondary contribution since the cyclones develop over the ocean with a wide range of SST values (from 22.5 °C to 28.6 °C in the initial phase of cyclones). The six subtropical cyclones are less deep in the atmosphere column than the tropical ones and, unlike the extratropical cyclones, they have little or no westward tilt with an increase in height. The studied subtropical cyclones produced adverse weather conditions such as (a) strong winds (reaching 17 m·s−1 at 10 m high) for a long period occurring east/southeastward of the cyclone center, and (b) high amounts of rainfall along the southeastern coast of Brazil, where the accumulated rainfall varied between 170 to 350 mm, being in most cases higher than the monthly climatology. Over the continent, the Brazilian states of Rio de Janeiro and Espírito Santo were the most affected by the intense rainfall associated with the cyclones.

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Section: Synoptic Analysismentioning

confidence: 57%

“…The moisture travels from its source to the cyclone region like a corridor in the lower atmosphere [48], which is called conveyor belt or atmospheric river. For extratropical cyclones, the atmospheric rivers contribute to deepening these systems by providing more water vapor for latent heat release [49].…”

Section: Synoptic Analysismentioning

confidence: 99%

Key Features and Adverse Weather of the Named Subtropical Cyclones over the Southwestern South Atlantic Ocean

2018

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“…Atmospheric rivers (ARs) are elongated regions of intense horizontal water vapor transport, which are often associated with a baroclinic midlatitude cyclone (Neiman et al, ; Ralph et al, ; Ralph et al, ; Zhang et al, ; Zhu & Newell, ). Many studies have revealed the important link between ARs and annual precipitation over different regions around the globe (Dettinger et al, ; Lavers et al, ; Ralph & Dettinger ; Neiman et al, ; Lavers & Villarini, ; Lamjiri et al, ; and others), their association with global floods and water availability (Ralph et al, ; Leung & Qian, ; Ralph & Dettinger ; Paltan et al, ; Corringham, ), their relationship to snowpack over the western U.S. (Goldenson et al, ; Guan et al, ; Huning et al, , ), their importance to extratropical climate and hydrology (Gorodetskaya et al, ; Nash et al, ), and their projected changes in a warming climate (e.g., Espinoza et al, ; Guirguis et al, ).…”

Section: Introductionmentioning

confidence: 99%

Experimental Subseasonal‐to‐Seasonal (S2S) Forecasting of Atmospheric Rivers Over the Western United States

et al. 2019

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A multimodel evaluation of subseasonal‐to‐seasonal (S2S) hindcast skill of atmospheric rivers (ARs) out to 4‐week lead over the western United States is presented for three operational hindcast systems: European Centre for Medium‐Range Weather Forecasts (ECMWF; Europe), National Centers for Environmental Prediction (NCEP; U.S.), and Environment and Canada Climate Change (ECCC; Canada). Ensemble mean biases and Brier Skill Scores are examined for no, moderate, and high levels of AR activity (0, 1–2, and 3–7 AR days/week, respectively). All hindcast systems are more skillful in predicting no and high AR activity relative to moderate activity. There are isolated regions of skill at week‐3 over 150–125°W, 25–35°N for the no and high AR activity levels, with larger magnitude and spatial extent of the skill in ECMWF and ECCC compared to NCEP. The spatial pattern of this skill suggests that for high AR activity, a southwest‐to‐northeast orientation is more predictable at subseasonal lead times than other orientations, and for no AR activity, more skill exists in the subtropical North Pacific, upstream of central and southern California. AR hindcast skill along the western U.S. is most strongly increased in hindcasts initialized during Madden‐Julian Oscillation (MJO) Phases 1 and 8, and hindcast skill is substantially decreased over California in hindcasts initialized during MJO Phase 4. Skill modulations in the ECMWF hindcast system conditioned on El Niño‐Southern Oscillation phase are weaker than those conditioned on particular MJO phases. This work provides hindcast skill benchmarks and uncertainty quantification for experimental real‐time forecasts of AR activity during winters 2019–2021 as part of the S2S Prediction Project Real‐time Pilot Initiative in collaboration with the California Department of Water Resources.

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“…dT (26) where ∆T e p is the surface temperature differences between the pole and the equator. First, we consider the partial sensitivity coefficients which reflect the sensitivity of n with respect to T, ∆T e p and Γ:…”

Section: Qualitative Analysismentioning

confidence: 99%

“…One of the main dynamical mechanisms leading to the meridional transport of heat, moisture, and momentum from the tropical to polar latitudes and, thereby to the global redistribution of atmospheric moisture, are the large-scale extratropical eddies (cyclones) [19][20][21][22]. The so-called "atmospheric rivers" that transport water vapor outside of the tropics through the extratropics (middle latitudes) are associated with mid-latitude cyclonic eddies and their frontal zones [25,26]. Recent studies have indicated an increase in intensity of extratropical cyclones and a decrease in their frequency [27][28][29][30][31][32][33][34].…”

Section: Introductionmentioning

confidence: 99%

Estimated Impacts of Climate Change on Eddy Meridional Moisture Transport in the Atmosphere

Soldatenko

2019

Applied Sciences

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Research findings suggest that water (hydrological) cycle of the earth intensifies in response to climate change, since the amount of water that evaporates from the ocean and land to the atmosphere and the total water content in the air will increase with temperature. In addition, climate change affects the large-scale atmospheric circulation by, for example, altering the characteristics of extratropical transient eddies (cyclones), which play a dominant role in the meridional transport of heat, moisture, and momentum from tropical to polar latitudes. Thus, climate change also affects the planetary hydrological cycle by redistributing atmospheric moisture around the globe. Baroclinic instability, a specific type of dynamical instability of the zonal atmospheric flow, is the principal mechanism by which extratropical cyclones form and evolve. It is expected that, due to global warming, the two most fundamental dynamical quantities that control the development of baroclinic instability and the overall global atmospheric dynamics—the parameter of static stability and the meridional temperature gradient (MTG)—will undergo certain changes. As a result, climate change can affect the formation and evolution of transient extratropical eddies and, therefore, macro-exchange of heat and moisture between low and high latitudes and the global water cycle as a whole. In this paper, we explore the effect of changes in the static stability parameter and MTG caused by climate change on the annual-mean eddy meridional moisture flux (AMEMF), using the two classical atmospheric models: the mid-latitude f-plane model and the two-layer β-plane model. These models are represented in two versions: “dry,” which considers the static stability of dry air alone, and “moist,” in which effective static stability is considered as a combination of stability of dry and moist air together. Sensitivity functions were derived for these models that enable estimating the influence of infinitesimal perturbations in the parameter of static stability and MTG on the AMEMF and on large-scale eddy dynamics characterized by the growth rate of unstable baroclinic waves of various wavelengths. For the base climate change scenario, in which the surface temperature increases by 1 °C and warming of the upper troposphere outpaces warming of the lower troposphere by 2 °C (this scenario corresponds to the observed warming trend), the response of the mass-weighted vertically averaged annual mean MTG is -0.2 ℃ per 1000 km. The dry static stability increases insignificantly relative to the reference climate state, while on the other hand, the effective static stability decreases by more than 5.4%. Assuming that static stability of the atmosphere and the MTG are independent of each other (using One-factor-at-a-time approach), we estimate that the increase in AMEMF caused by change in MTG is about 4%. Change in dry static stability has little effect on AMEMF, while change in effective static stability leads to an increase in AMEMF of about 5%. Thus, neglecting atmospheric moisture in calculations of the atmospheric static stability leads to tangible differences between the results obtained using the dry and moist models. Moist models predict ~9% increase in AMEMF due to global warming. Dry models predict ~4% increase in AMEMF solely because of the change in MTG. For the base climate change scenario, the average temperature of the lower troposphere (up to ~4 km), in which the atmospheric moisture is concentrated, increases by ~1.5 ℃. This leads to an increase in specific humidity of about 10.5%. Thus, since both AMEMF and atmospheric water vapor content increase due to the influence of climate change, a rather noticeable restructuring of the global water cycle is expected.

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The Relationship Between Extratropical Cyclone Strength and Atmospheric River Intensity and Position

Cited by 142 publications

References 42 publications

Key Features and Adverse Weather of the Named Subtropical Cyclones over the Southwestern South Atlantic Ocean

Key Features and Adverse Weather of the Named Subtropical Cyclones over the Southwestern South Atlantic Ocean

Experimental Subseasonal‐to‐Seasonal (S2S) Forecasting of Atmospheric Rivers Over the Western United States

Estimated Impacts of Climate Change on Eddy Meridional Moisture Transport in the Atmosphere

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