scholarly journals An Identification of the Mechanisms that Lead to Arctic Warming During Planetary-Scale and Synoptic-Scale Wave Life Cycles

2017 ◽  
Vol 74 (6) ◽  
pp. 1859-1877 ◽  
Author(s):  
Cory Baggett ◽  
Sukyoung Lee
Keyword(s):  
Life Cycle ◽  
Life Cycles ◽  
Tropical Convection ◽  
The Arctic ◽  
Stationary Waves ◽  
Composite Analysis ◽  
Synoptic Scale ◽  
Arctic Warming ◽  
Planetary Scale ◽  
The Western Pacific

Abstract The dynamical mechanisms that lead to wintertime Arctic warming during the planetary-scale wave (PSW) and synoptic-scale wave (SSW) life cycles are identified by performing a composite analysis of ERA-Interim data. The PSW life cycle is preceded by localized tropical convection over the western Pacific. Upon reaching the midlatitudes, the PSWs amplify as they undergo baroclinic conversion and constructively interfere with the climatological stationary waves. The PSWs flux large quantities of sensible and latent heat into the Arctic, which produces a regionally enhanced greenhouse effect that increases downward IR and warms the Arctic 2-m temperature. The SSW life cycle is also capable of increasing downward IR and warming the Arctic 2-m temperature, but the greatest warming is accomplished in the subset of SSW events with the most amplified PSWs. Consequently, during both the PSW and SSW life cycles, wintertime Arctic warming arises from the amplification of the PSWs.

scholarly journals An Investigation of the Presence of Atmospheric Rivers over the North Pacific during Planetary-Scale Wave Life Cycles and Their Role in Arctic Warming

2016 ◽  
Vol 73 (11) ◽  
pp. 4329-4347 ◽  
Author(s):  
Cory Baggett ◽  
Sukyoung Lee ◽  
Steven Feldstein
Keyword(s):  
Life Cycle ◽  
Latent Heat ◽  
Rossby Wave ◽  
North Pacific ◽  
Tropical Convection ◽  
The Arctic ◽  
Synoptic Scale ◽  
Atmospheric Rivers ◽  
Planetary Scale ◽  
The North

Abstract Heretofore, the tropically excited Arctic warming (TEAM) mechanism put forward that localized tropical convection amplifies planetary-scale waves, which transport sensible and latent heat into the Arctic, leading to an enhancement of downward infrared radiation and Arctic surface warming. In this study, an investigation is made into the previously unexplored contribution of the synoptic-scale waves and their attendant atmospheric rivers to the TEAM mechanism. Reanalysis data are used to conduct a suite of observational analyses, trajectory calculations, and idealized model simulations. It is shown that localized tropical convection over the Maritime Continent precedes the peak of the planetary-scale wave life cycle by ~10–14 days. The Rossby wave source induced by the tropical convection excites a Rossby wave train over the North Pacific that amplifies the climatological December–March stationary waves. These amplified planetary-scale waves are baroclinic and transport sensible and latent heat poleward. During the planetary-scale wave life cycle, synoptic-scale waves are diverted northward over the central North Pacific. The warm conveyor belts associated with the synoptic-scale waves channel moisture from the subtropics into atmospheric rivers that ascend as they move poleward and penetrate into the Arctic near the Bering Strait. At this time, the synoptic-scale waves undergo cyclonic Rossby wave breaking, which further amplifies the planetary-scale waves. The planetary-scale wave life cycle ceases as ridging over Alaska retrogrades westward. The ridging blocks additional moisture transport into the Arctic. However, sensible and latent heat amounts remain elevated over the Arctic, which enhances downward infrared radiation and maintains warm surface temperatures.

scholarly journals Dynamics of Eddy-Driven Low-Frequency Dipole Modes. Part I: A Simple Model of North Atlantic Oscillations

2007 ◽  
Vol 64 (1) ◽  
pp. 3-28 ◽  
Author(s):  
Dehai Luo ◽  
Anthony R. Lupo ◽  
Han Wan
Keyword(s):  
Life Cycle ◽  
Theoretical Model ◽  
North Atlantic ◽  
Low Frequency ◽  
Positive Phase ◽  
Negative Phase ◽  
Synoptic Scale ◽  
Planetary Scale ◽  
The North ◽  
The North Atlantic Oscillation

Abstract A simple theoretical model is proposed to clarify how synoptic-scale waves drive the life cycle of the North Atlantic Oscillation (NAO) with a period of nearly two weeks. This model is able to elucidate what determines the phase of the NAO and an analytical solution is presented to indicate a high similarity between the dynamical processes of the NAO and zonal index, which is not derived analytically in previous theoretical studies. It is suggested theoretically that the NAO is indeed a nonlinear initial-value problem, which is forced by both preexisting planetary-scale and synoptic-scale waves. The eddy forcing arising from the preexisting synoptic-scale waves is shown to be crucial for the growth and decay of the NAO, but the preexisting low-over-high (high-over-low) dipole planetary-scale wave must be required to match the preexisting positive-over-negative (negative-over-positive) dipole eddy forcing so as to excite a positive (negative) phase NAO event. The positive and negative feedbacks of the preexisting dipole eddy forcing depending upon the background westerly wind seem to dominate the life cycle of the NAO and its life period. An important finding in the theoretical model is that negative-phase NAO events could be excited repeatedly after the first event has decayed, but for the positive phase downstream isolated dipole blocks could be produced after the first event has decayed. This is supported by observed cases of the NAO events presented in this paper. In addition, a statistical study of the relationship between the phase of the NAO and blocking activity over Europe in terms of the seasonal mean NAO index shows that blocking events over Europe are more frequent and long-lived for strong positive-phase NAO years, indicating that the positive-phase NAO favors the occurrence of European blocking events.

Life cycles of four species of Pseudocalanus in Nova Scotia

1989 ◽  
Vol 67 (3) ◽  
pp. 552-558 ◽  
Author(s):  
I. A. McLaren ◽  
Estelle Laberge ◽  
C. J. Corkett ◽  
J.-M. Sévigny
Keyword(s):  
Life Cycle ◽  
Nova Scotia ◽  
First Generation ◽  
Early Summer ◽  
Life Cycles ◽  
The Arctic ◽  
Late Winter ◽  
Early Winter ◽  
Temperature Dependent ◽  
Scotian Shelf

The primarily arctic Pseudocalanus acuspes, relict in Bedford Basin, Nova Scotia, produces a first generation (G1) in late winter; most G1 individuals mature in late spring. The G1 then produces a G2, most of which "rest" in copepodite stages III and IV until early winter. These stages store large amounts of lipid in early summer, which slowly diminish subsequently. A small number of G2 individuals continue to develop at temperature-dependent rates, maturing in early autumn and producing G3 adults in November. Copepodites developing in winter and spring store less lipid. The primarily arctic Pseudocalanus minutus, rare in Bedford Basin and on the Scotia Shelf, is strictly annual, developing to a lipid-filled copepodite stage V after spawning in late winter. The arctic–temperate Pseudocalanus newmani is abundant on the Scotian Shelf, but may not be self-sustaining when advected into Bedford Basin. It stores little lipid and appears to have at least three mature generations at temperature-dependent intervals over Browns Bank between May and November. It may rest in winter, or its life-cycle synchrony by spring could result from food-limited development during winter. The temperate Pseudocalanus moultoni appears to have a life cycle similar to that of P. newmani, but was less common during summer on Browns Bank. These life cycles are appropriately adapted to the geographical ranges of the species, and show some parallels with species of Calanus.

scholarly journals Exploring the Tropically Excited Arctic Warming Mechanism with Station Data: Links between Tropical Convection and Arctic Downward Infrared Radiation

2016 ◽  
Vol 73 (3) ◽  
pp. 1143-1158 ◽  
Author(s):  
Matthew D. Flournoy ◽  
Steven B. Feldstein ◽  
Sukyoung Lee ◽  
Eugene E. Clothiaux
Keyword(s):  
Water Vapor ◽  
Rossby Wave ◽  
Infrared Radiation ◽  
Wave Train ◽  
Tropical Convection ◽  
The Arctic ◽  
Water Vapor Flux ◽  
Arctic Warming ◽  
Vapor Flux ◽  
Wave Trains

Abstract The Tropically Excited Arctic Warming (TEAM) mechanism ascribes warming of the Arctic surface to tropical convection, which excites poleward-propagating Rossby wave trains that transport water vapor and heat into the Arctic. A crucial component of the TEAM mechanism is the increase in downward infrared radiation (IR) that precedes the Arctic warming. Previous studies have examined the downward IR associated with the TEAM mechanism using reanalysis data. To corroborate previous findings, this study examines the linkage between tropical convection, Rossby wave trains, and downward IR with Baseline Surface Radiation Network (BSRN) downward IR station data. The physical processes that drive changes in the downward IR are also investigated by regressing 300-hPa geopotential height, outgoing longwave radiation, water vapor flux, ERA-Interim downward IR, and other key variables against the BSRN downward IR at Barrow, Alaska, and Ny-Ålesund, Spitsbergen. Both the Barrow and the Ny-Ålesund station downward IR anomalies are preceded by anomalous tropical convection and poleward-propagating Rossby wave trains. The wave train associated with Barrow resembles the Pacific–North America teleconnection pattern, and that for Ny-Ålesund corresponds to a northwestern Atlantic wave train. It is found that both wave trains promote warm and moist advection from the midlatitudes into the Arctic. The resulting water vapor flux convergence, multiplied by the latent heat of vaporization, closely resembles the regressed ERA-Interim downward IR. These results suggest that the combination of warm advection, latent heat release, and increased cloudiness all contribute toward an increase in downward IR.

scholarly journals Decadal changes of wintertime poleward heat and moisture transport associated with the amplified Arctic warming

2021 ◽  
Author(s):  
Xiaozhuo Sang ◽  
Xiu-Qun Yang ◽  
Lingfeng Tao ◽  
Jiabei Fang ◽  
Xuguang Sun
Keyword(s):  
Heat Transport ◽  
Moisture Transport ◽  
Stationary Wave ◽  
The Arctic ◽  
Stationary Waves ◽  
High Latitudes ◽  
Arctic Warming ◽  
Poleward Heat Transport ◽  
Heat And Moisture ◽  
Moisture Transports

Abstract The Arctic warming, especially during winter, has been almost twice as large as the global average since the late 1990s, which is known as the Arctic amplification. Yet linkage between the amplified Arctic warming and the midlatitude change is still under debate. This study examines the decadal changes of wintertime poleward heat and moisture transports between two 18-yr epochs (1999–2016 and 1981–1998) with five atmospheric reanalyses. It is found that the wintertime Arctic warming induces an amplification of the high latitude stationary wave component of zonal wavenumber one but a weakening of the wavenumber two. These stationary wave changes enhance poleward heat and moisture transports, which are conducive to further Arctic warming and moistening, acting as a positive feedback onto the Arctic warming. Meanwhile, the Arctic warming reduces atmospheric baroclinicity and thus weakens synoptic eddy activities in the high latitudes. The decreased transient eddy activities reduce poleward heat and moisture transports, which decrease the Arctic temperature and moisture, acting as a negative feedback onto the Arctic warming. The total poleward heat transport contributes little to the Arctic warming, since the increased poleward heat transport by stationary waves is nearly canceled by the decreased transport by transient eddies. However, the total poleward moisture transport increases over most areas of the high latitudes that is dominated by the increased transport by stationary waves, which provides a significant net positive feedback onto the Arctic warming and moistening. Such a poleward moisture transport feedback may be particularly crucial to the amplified Arctic warming during winter when the ice-albedo feedback vanishes.

Arctic climate response to extreme events in synoptic and planetary scale atmospheric energy transport

2020 ◽  
Author(s):  
Johanne H. Rydsaa ◽  
Rune G. Graversen ◽  
Patrick Stoll
Keyword(s):  
Energy Transport ◽  
Winter Season ◽  
Arctic Climate ◽  
The Arctic ◽  
Synoptic Scale ◽  
Near Surface ◽  
Latent Energy ◽  
Atmospheric Energy ◽  
Planetary Scale ◽  
Atmospheric Energy Transport

<p>Atmospheric energy transport into the Arctic (>70° N) has been shown to greatly alter the Arctic temperatures and the development of the Arctic weather and climate. Recent research suggests that latent energy transport into the Arctic by large, planetary-scale atmospheric systems cause a stronger and more long-lasting impact on near surface temperatures, than energy transported by smaller, synoptic scale systems. This implies that Rossby waves impact Arctic climate more than synoptic cyclones. Therefore, shifts in circulation patterns driving atmospheric energy transport into the Arctic on different scales have a potential to change Arctic climate.</p><p>Here, we show that the annual mean impact of latent energy transport on Arctic temperatures is dominated by the winter season transport. Furthermore, by examining the ERA5 dataset for the years 1979-2018, we find that over the past four decades, there has been a shift in the mean winter season latent energy transport, from smaller, synoptic scale systems (-0.03 PW/decade), towards larger, planetary scale systems (+0.05 PW/decade) which as mentioned, have a larger climatic impact. As a consequence, this shift is estimated to have increased the Arctic temperatures. We find that the trends are driven by an increase in the extreme transport events (here we examine the upper 97.5<sup>th</sup> percentile). The upper extremes have increased more than the average on the planetary scale, and decreased more on the synoptic scale. The decrease in extreme synoptic scale transport at 70° N has been confirmed in other analyses of high vorticity weather systems. By examining the extreme transport events on seasonal scales, we reveal differences in the temporal distribution of planetary vs. synoptic scale extreme events, and identify areas of the Arctic that receive the strongest impact with respect to increases in near-surface temperatures.</p>

A 7-year life cycle for two Chironomus species in arctic Alaskan tundra ponds (Diptera: Chironomidae)

1982 ◽  
Vol 60 (1) ◽  
pp. 58-70 ◽  
Author(s):  
Malcolm G. Butler
Keyword(s):  
Life Cycle ◽  
Slow Growth ◽  
Larval Growth ◽  
Standing Stock ◽  
Open Water ◽  
Life Cycles ◽  
The Arctic ◽  
Larval Size ◽  
Larval Stages ◽  
Tundra Ponds

The life cycles of two sibling Chironomus species inhabiting tundra ponds on the arctic coast of Alaska are interpreted from larval and adult data collected over 3 years. Emergence of adults was highly synchronous within each species, and the two emergence periods were always discrete. Larvae of the two species could not be separated morphologically and were treated as a single population through most of the life cycle. Analysis of larval size and development toward pupation indicated that seven cohorts coexist on nearly all sampling dates. A 7-year developmental period for each cohort is hypothesized and is supported by larval growth rates observed in the habitat and by the rates at which apparent cohorts progressed through the larval stages. Ten cohorts observed during the study period showed very similar schedules of growth and development, but cohort abundances varied considerably.This life cycle is among the longest reported for an arctic insect. It results from slow growth during an annual open-water season of about 90 days, though neither food nor temperature limitation could be definitely implicated in causing such slow growth. Coexistence of up to seven cohorts in each species stabilized Chironomus production and standing stock and may be important to benthic-feeding waterfowl which use these ponds.

Two Types of Baroclinic Life Cycles during the Southern Hemisphere Summer

2009 ◽  
Vol 66 (5) ◽  
pp. 1401-1417 ◽  
Author(s):  
Woosok Moon ◽  
Steven B. Feldstein
Keyword(s):  
Life Cycle ◽  
Southern Hemisphere ◽  
Lower Troposphere ◽  
Wave Activity ◽  
Life Cycles ◽  
Initial Growth ◽  
Horizontal Shear ◽  
Synoptic Scale ◽  
Anomalous Wave ◽  
Wave Activity Flux

Abstract Baroclinic eddy life cycles of the Southern Hemisphere (SH) summer are investigated with NCEP–NCAR reanalysis data. A composite analysis is performed for the years 1980 through 2004. Individual life cycles are identified by local maxima in synoptic-scale eddy energy. Two types of baroclinic life cycles are examined, each defined by the strength of the barotropic energy conversion 2 days prior to the maximum baroclinic growth. For one life cycle, the barotropic conversion is anomalously weak before the maximum baroclinic growth; for the other, the barotropic conversion is anomalously strong. These two life cycles are referred to as the weak barotropic (WB) and strong barotropic (SB) life cycles. The analyses for the WB life cycle find that a poleward anomalous wave activity flux is observed within the SH tropics and subtropics just before the initial growth of the synoptic-scale eddies. In contrast, the SB life cycle exhibits an equatorward anomalous wave activity flux prior to the initial wave development. For the WB life cycle, these changes in the wave activity flux are shown to induce a mean meridional circulation that weakens and broadens the midlatitude zonal mean jet and reduces the baroclinicity in the midlatitude lower troposphere. Opposite characteristics are observed for the SB life cycle. Since the eddy growth rate is found to be greater in the WB life cycle, these results suggest that the influences of the barotropic governor mechanism (a reduction in horizontal shear coinciding with more rapidly growing baroclinic eddies) and the midlatitude baroclinicity oppose each other at the beginning of the life cycle, with the former being dominant. Both the WB and SB life cycles coincide with anomalous tropical convection. For the WB life cycle, there is a strengthening of the convection over the Maritime Continent, and for the SB life cycle there is a weakening in the convection over the same region. These results suggest that the two types of baroclinic life cycles are ultimately triggered by convection in the tropics.

scholarly journals Metadata Life Cycles, Use Cases and Hierarchies

2018 ◽  
Author(s):  
Ted Habermann
Keyword(s):  
Life Cycle ◽  
Software Development ◽  
Life Cycles ◽  
Use Cases ◽  
The Arctic ◽  
Research Projects ◽  
Metadata Standard ◽  
Incremental Approach ◽  
Spiral Model ◽  
Project Life

The historic view of metadata as “data about data” is expanding to include data about other items that must be created, used and understood throughout the data and project life cycles. In this context, metadata might better be defined as the structured and standard part of documentation and the metadata life cycle can be described as the metadata content that is required for documentation in each phase of the project and data life cycles. This incremental approach to metadata creation is similar to the spiral model used in software development. Each phase also has distinct users and specific questions they need answers to. In many cases, the metadata life cycle involves hierarchies where latter phases have increased numbers of items. The relationships between metadata in different phases can be captured through structure in the metadata standard or through conventions for identifiers. Metadata creation and management can be streamlined and simplified by re-using metadata across many records. Many of these ideas are being used in metadata for documenting the life cycle of research projects in the Arctic.

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