scholarly journals Relative Contributions of Synoptic and Low-Frequency Eddies to Time-Mean Atmospheric Moisture Transport, Including the Role of Atmospheric Rivers

2012 ◽  
Vol 25 (21) ◽  
pp. 7341-7361 ◽  
Author(s):  
Matthew Newman ◽  
George N. Kiladis ◽  
Klaus M. Weickmann ◽  
F. Martin Ralph ◽  
Prashant D. Sardeshmukh
Keyword(s):  
Moisture Transport ◽  
Low Frequency ◽  
The Arctic ◽  
Moisture Budget ◽  
Atmospheric Moisture ◽  
Atmospheric Rivers ◽  
Low Frequency Variability ◽  
The Mean ◽  
Mean Circulation ◽  
Atmospheric Moisture Transport

The relative contributions to mean global atmospheric moisture transport by both the time-mean circulation and by synoptic and low-frequency (periods greater than 10 days) anomalies are evaluated from the vertically integrated atmospheric moisture budget based on 40 yr of “chi corrected” NCEP–NCAR reanalysis data. In the extratropics, while the time-mean circulation primarily moves moisture zonally within ocean basins, low-frequency and synoptic anomalies drive much of the mean moisture transport both from ocean to land and toward the poles. In particular, during the cool-season low-frequency variability is the largest contributor to mean moisture transport into southwestern North America, Europe, and Australia. While some low-frequency transport originates in low latitudes, much is of extratropical origin due to large-scale atmospheric anomalies that extract moisture from the northeast Pacific and Atlantic Oceans. Low-frequency variability is also integral to the Arctic (latitudes > 70°N) mean moisture budget, especially during summer, when it drives mean poleward transport from relatively wet high-latitude continental regions. Synoptic variability drives about half of the mean poleward moisture transport in the midlatitudes of both hemispheres, consistent with simple “lateral mixing” arguments. Extratropical atmospheric transport is also particularly focused within “atmospheric rivers” (ARs), relatively narrow poleward-moving moisture plumes associated with frontal dynamics. AR moisture transport, defined by compositing fluxes over those locations and times where column-integrated water vapor and poleward low-level wind anomalies are both positive, represents most of the total extratropical meridional moisture transport. These results suggest that understanding potential anthropogenic changes in the earth ’s hydrological cycle may require understanding corresponding changes in atmospheric variability, especially on low-frequency time scales.

scholarly journals Atmospheric moisture transport: the bridge between ocean evaporation and Arctic ice melting

2015 ◽  
Vol 6 (2) ◽  
pp. 583-589 ◽  
Author(s):  
L. Gimeno ◽  
M. Vázquez ◽  
R. Nieto ◽  
R. M. Trigo
Keyword(s):  
Climate Change ◽  
Sea Ice ◽  
Moisture Transport ◽  
The Arctic ◽  
Atmospheric Moisture ◽  
Ice Melting ◽  
Moisture Sources ◽  
The North ◽  
Arctic Ice ◽  
Atmospheric Moisture Transport

Abstract. Changes in the atmospheric moisture transport have been proposed as a vehicle for interpreting some of the most significant changes in the Arctic region. The increasing moisture over the Arctic during the last decades is not strongly associated with the evaporation that takes place within the Arctic area itself, despite the fact that the sea ice cover is decreasing. Such an increment is consistent and is more dependent on the transport of moisture from the extratropical regions to the Arctic that has increased in recent decades and is expected to increase within a warming climate. This increase could be due either to changes in circulation patterns which have altered the moisture sources, or to changes in the intensity of the moisture sources because of enhanced evaporation, or a combination of these two mechanisms. In this short communication we focus on the more objective assessment of the strong link between ocean evaporation trends and Arctic Sea ice melting. We will critically analyse several recent results suggesting links between moisture transport and the extent of sea ice in the Arctic, this being one of the most distinct indicators of continuous climate change both in the Arctic and on a global scale. To do this we will use a sophisticated Lagrangian approach to develop a more robust framework on some of these previous disconnecting results, using new information and insights. Results reached in this study stress the connection between two climate change indicators, namely an increase in evaporation over source regions (mainly the Mediterranean Sea, the North Atlantic Ocean and the North Pacific Ocean in the paths of the global western boundary currents and their extensions) and Arctic ice melting precursors.

scholarly journals Short Communication: Atmospheric moisture transport, the bridge between ocean evaporation and Arctic ice melting

2015 ◽  
Vol 6 (1) ◽  
pp. 1033-1045
Author(s):  
L. Gimeno ◽  
M. Vázquez ◽  
R. Nieto ◽  
R. M. Trigo
Keyword(s):  
Sea Ice ◽  
Moisture Transport ◽  
Short Communication ◽  
Global Climate ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Atmospheric Moisture ◽  
Ice Melting ◽  
Moisture Sources ◽  
Atmospheric Moisture Transport

Abstract. If we could choose a region where the effects of global warming are likely to be pronounced and considerable, and at the same time one where the changes could affect the global climate in similarly asymmetric way with respect to other regions, this would unequivocally be the Arctic. The atmospheric branch of the hydrological cycle lies behind the linkages between the Arctic system and the global climate. Changes in the atmospheric moisture transport have been proposed as a vehicle for interpreting the most significant changes in the Arctic region. This is because the transport of moisture from the extratropical regions to the Arctic has increased in recent decades, and is expected to increase within a warming climate. This increase could be due either to changes in circulation patterns which have altered the moisture sources, or to changes in the intensity of the moisture sources because of enhanced evaporation, or a combination of these two mechanisms. In this short communication we focus on the assessing more objectively the strong link between ocean evaporation trends and Arctic Sea ice melting. We will critically analyze several recent results suggesting links between moisture transport and the extent of sea-ice in the Arctic, this being one of the most distinct indicators of continuous climate change both in the Arctic and on a global scale. To do this we will use a sophisticated Lagrangian approach to develop a more robust framework on some of these previous disconnect ng results, using new information and insights. Among the many mechanisms that could be involved are hydrological (increased Arctic river discharges), radiative (increase of cloud cover and water vapour) and meteorological (increase in summer storms crossing the Arctic, or increments in precipitation).

scholarly journals Atmospheric rivers in the Australia-Asian region: a BoM–CMA collaborative study

2020 ◽  
Author(s):  
Chengzhi Ye ◽  
Huqiang Zhang ◽  
Aurel Moise ◽  
Ruping Mo
Keyword(s):  
Water Vapour ◽  
Moisture Transport ◽  
Weather Prediction ◽  
Boreal Summer ◽  
Atmospheric Moisture ◽  
Atmospheric Rivers ◽  
Extreme Precipitation Events ◽  
Set Up ◽  
Atmospheric Moisture Transport

The name ‘atmospheric river’ (AR) could easily be misinterpreted to mean rivers flowing in the sky. But, ARs actually refer to narrow bands of strong horizontal water vapour transport that are concentrated in the lower troposphere. These bands are called ‘atmospheric rivers’ because the water vapour flux they carry is close to the volume of water carried by big river systems on the ground. ARs can cause heavy rainfall events if some physical mechanisms, such as orographic enhancement, exist to set up the moisture convergence and vertical motions necessary to produce condensation. In recent decades, these significant moisture plumes have attracted increasing attention from scientific communities, especially in North America and western Europe, to further understand the connections between ARs and extreme precipitation events which can trigger severe natural disasters such as floods, mudslides and avalanches. Yet very limited research has been conducted in the Australia-Asian (A-A) region, where the important role of atmospheric moisture transport has long been recognised for its rainfall generation and variations. In this paper, we introduce a collaborative project between the Australian Bureau of Meteorology and China Meteorological Administration, which was set up to explore the detailed AR characteristics of atmospheric moisture transport embedded in the A-A monsoon system. The project in China focused on using AR analysis to explore connections between moisture transport and extreme rainfall mainly during the boreal summer monsoon season. In Australia, AR analysis was used to understand the connections between the river-like Northwest Cloud Band and rainfall in the region. Results from this project demonstrate the potential benefits of applying AR analysis to better understand the role of tropical moisture transport in rainfall generation in the extratropics, thus achieve better rainfall forecast skills at NWP (Numerical Weather Prediction), sub-seasonal and seasonal time scales. We also discuss future directions of this collaborative research, including further assessing potential changes in ARs under global warming.

Atmospheric moisture transport between mid‐latitudes and the Arctic: Regional, seasonal and vertical distributions

2019 ◽  
Vol 39 (6) ◽  
pp. 2862-2879 ◽  
Author(s):  
Tuomas Naakka ◽  
Tiina Nygård ◽  
Timo Vihma ◽  
Joseph Sedlar ◽  
Rune Graversen
Keyword(s):  
Moisture Transport ◽  
The Arctic ◽  
Atmospheric Moisture ◽  
Vertical Distributions ◽  
Atmospheric Moisture Transport

From Amazonia to southern Africa: atmospheric moisture transport through low-level jets and atmospheric rivers

2018 ◽  
Vol 1436 (1) ◽  
pp. 217-230 ◽  
Author(s):  
Alexandre M. Ramos ◽  
Ross C. Blamey ◽  
Iago Algarra ◽  
Raquel Nieto ◽  
Luis Gimeno ◽  
...  
Keyword(s):  
Southern Africa ◽  
Moisture Transport ◽  
Atmospheric Moisture ◽  
Atmospheric Rivers ◽  
Low Level ◽  
Low Level Jets ◽  
Atmospheric Moisture Transport

scholarly journals Information Theory and Predictability for Low-Frequency Variability

2005 ◽  
Vol 62 (1) ◽  
pp. 65-87 ◽  
Author(s):  
Rafail Abramov ◽  
Andrew Majda ◽  
Richard Kleeman
Keyword(s):  
Information Flow ◽  
Relative Entropy ◽  
Low Frequency ◽  
The Arctic ◽  
Cross Term ◽  
Lack Of Information ◽  
Low Frequency Variability ◽  
Wide Range ◽  
The Mean ◽  
Mean State

Abstract A predictability framework, based on relative entropy, is applied here to low-frequency variability in a standard T21 barotropic model on the sphere with realistic orography. Two types of realistic climatology, corresponding to different heights in the troposphere, are used. The two dynamical regimes with different mixing properties, induced by the two types of climate, allow the testing of the predictability framework in a wide range of situations. The leading patterns of empirical orthogonal functions, projected onto physical space, mimic the large-scale teleconnections of observed flow, in particular the Arctic Oscillation, Pacific–North American pattern, and North Atlantic Oscillation. In the ensemble forecast experiments, relative entropy is utilized to measure the lack of information in three different situations: the lack of information in the climate relative to the forecast ensemble, the lack of information by using only the mean state and variance of the forecast ensemble, and information flow—the time propagation of the lack of information in the direct product of marginal probability densities relative to joint probability density in a forecast ensemble. A recently developed signal–dispersion–cross-term decomposition is utilized for climate-relative entropy to determine different physical sources of forecast information. It is established that though dispersion controls both the mean state and variability of relative entropy, the sum of signal and cross-term governs physical correlations between a forecast ensemble and EOF patterns. Information flow is found to be responsible for correlated switches in the EOF patterns within a forecast ensemble.

scholarly journals Linking warm Arctic winters, Rossby waves and Cold Spells: an idealized numerical study

2021 ◽  
Author(s):  
Emilien Jolly ◽  
Fabio D’Andrea ◽  
Gwendal Rivière ◽  
Sebastien Fromang
Keyword(s):  
Rossby Waves ◽  
Numerical Study ◽  
Extreme Temperature ◽  
Low Frequency ◽  
The Arctic ◽  
Mean Temperature ◽  
Power Shift ◽  
Low Frequency Variability ◽  
The Mean

AbstractThe changes of midlatitude Rossby waves and cold extreme temperature events (cold spells) during warm Arctic winters are analysed using a dry three-level quasi-geostrophic model on the sphere. Two long-term simulations are compared: the first run has the observed wintertime climatology, while the second run includes the composite of the global anomalies associated with the six hottest Arctic winters. A spectral analysis shows a large increase in wave amplitude for near-zero and westward phase speeds and a more moderate decrease for high eastward phase speeds. The increase in low-frequency variability (periods greater than a week) associated with the power shift to slower waves is largely responsible for an increase in mid-latitude long-lasting cold spells. In mid-latitude regions, in presence of a mean warming, that increase in low-frequency variance compensates the increase of the mean temperature, resulting at places in a frequency of cold spells that remains by and large unaltered. In presence of mean cooling, both the increase in variance and the decrease in the mean temperature participate in an increased frequency of cold spells. Sensitivity experiments show that the power shift to slower waves is mainly due to the tropical anomalies that developed during those particular winters and less importantly to changes in the background flow at higher latitudes associated with the Arctic Amplification pattern.

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