scholarly journals Influence of Northern Hemispheric Winter Warming on the Pacific Storm Track

2021 ◽  
Author(s):  
Hyung-Ju Park ◽  
Kwang-Yul Kim
Keyword(s):  
Heat Flux ◽  
Global Warming ◽  
Energy Conversion ◽  
Storm Track ◽  
The Arctic ◽  
Late Winter ◽  
Turbulent Heat ◽  
Early Winter ◽  
Eddy Heat Flux ◽  
Northern Hemispheric

AbstractEffect of global warming on the sub-seasonal variability of the Northern Hemispheric winter (NDJFM) Pacific storm-track (PST) activity has been investigated. Previous studies showed that the winter-averaged PST has shifted northward and intensified, which was explained in terms of energy exchange with the mean field. Effect of global warming exhibits spatio-temporal heterogeneity with predominance over the Arctic region and in the winter season. Therefore, seasonal averaging may hide important features on sub-seasonal scales. In this study, distinct sub-seasonal response in storm track activities to winter Northern Hemispheric warming is analyzed applying cyclostationary empirical orthogonal function analysis to ERA5 data. The key findings are as follows. Change in the PST is not uniform throughout the winter; the PST shifts northward in early winter (NDJ) and intensifies in late winter (FM). In early winter, the combined effect of weakened baroclinic process to the south of the climatological PST and weakened barotropic damping to the north is responsible for the northward shift. In late winter, both processes contribute to the amplification of the PST. Further, change in baroclinic energy conversion is quantitatively dominated by eddy heat flux, whereas axial tilting of eddies is primarily responsible for change in barotropic energy conversion. A close relationship between anomalous eddy heat flux and anomalous boundary heating, which is largely determined by surface turbulent heat flux, is also demonstrated.

scholarly journals Influence of Early Winter Upward Wave Activity Flux on Midwinter Circulation in the Stratosphere and Troposphere

2004 ◽  
Vol 17 (22) ◽  
pp. 4443-4452 ◽  
Author(s):  
Alexei Karpetchko ◽  
Grigory Nikulin
Keyword(s):  
Heat Flux ◽  
Reanalysis Data ◽  
Wave Activity ◽  
Heat Fluxes ◽  
Early Winter ◽  
Polar Night ◽  
Wave Refraction ◽  
Eddy Heat Flux ◽  
Wave Flux

Abstract Using NCEP–NCAR reanalysis data the authors show that the November–December averaged stratospheric eddy heat flux is strongly anticorrelated with the January–February averaged eddy heat flux in the midlatitude stratosphere and troposphere. This finding further emphasizes differences between early and midwinter stratospheric wave flux behavior, which has recently been found in long-term variations. Analysis suggests that the intraseasonal anticorrelation of stratospheric heat fluxes results from changes in the upward wave propagation in the troposphere. Stronger (weaker) upward wave fluxes in early winter lead to weaker (stronger) upward wave fluxes from the troposphere during midwinter. Also, enhanced equatorward wave refraction during midwinter (due to the stronger polar night jet) is associated with weak heat flux in the early winter. It is suggested that the effect of enhanced midwinter upward wave flux from the troposphere in the years with weak early winter heat flux overcompensates the effect of increased equatorward wave refraction in midwinter, leading to a net increase of midwinter upward wave fluxes into the stratosphere.

scholarly journals Vertical Structure and Energetics of the Western Pacific Teleconnection Pattern

2016 ◽  
Vol 29 (18) ◽  
pp. 6597-6616 ◽  
Author(s):  
Sho Tanaka ◽  
Kazuaki Nishii ◽  
Hisashi Nakamura
Keyword(s):  
Heat Flux ◽  
North Pacific ◽  
Thermal Gradient ◽  
Far East ◽  
Storm Track ◽  
Lower Troposphere ◽  
Western Pacific ◽  
Mean Flow ◽  
Eddy Heat Flux ◽  
The Western Pacific

Abstract The western Pacific (WP) pattern, characterized by north–south dipolar anomalies in pressure over the Far East and western North Pacific, is known as one of the dominant teleconnection patterns in the wintertime Northern Hemisphere. Composite analysis reveals that monthly height anomalies exhibit baroclinic structure with their phase lines tilting southwestward with height in the lower troposphere. The anomalies can thus yield not only a poleward heat flux across the climatological thermal gradient across the strong Pacific jet but also a westward heat flux across the climatological thermal gradient between the North Pacific and the cooler Asian continent. The resultant baroclinic conversion of available potential energy (APE) from the climatological-mean flow contributes most efficiently to the APE maintenance of the monthly WP pattern, acting against strong thermal damping effects by anomalous heat exchanges with the underlying ocean and anomalous precipitation in the subtropics and by the effect of anomalous eddy heat flux under modulated storm-track activity. Kinetic energy (KE) of the pattern is maintained through barotropic feedback forcing associated with modulated activity of transient eddies and the conversion from the climatological-mean westerlies, both of which act against frictional damping. The net feedback forcing by transient eddies is therefore not particularly efficient. The present study suggests that the WP pattern has a characteristic of a dynamical mode that can maintain itself through efficient energy conversion from the climatological-mean fields even without external forcing, including remote influence from the tropics.

scholarly journals Mechanism of Seasonal Arctic Sea Ice Evolution and Arctic Amplification

2016 ◽  
Author(s):  
Kwang-Yul Kim ◽  
Benjamin D. Hamlington ◽  
Hanna Na ◽  
Jinju Kim
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Air Temperature ◽  
Surface Air Temperature ◽  
Longwave Radiation ◽  
The Arctic ◽  
Turbulent Heat ◽  
Arctic Amplification ◽  
Ice Melting ◽  
Downward Longwave Radiation

Abstract. Sea ice melting is proposed as a primary reason for the Artic amplification, although physical mechanism of the Arctic amplification and its connection with sea ice melting is still in debate. In the present study, monthly ERA-interim reanalysis data are analyzed via cyclostationary empirical orthogonal function analysis to understand the seasonal mechanism of sea ice melting in the Arctic Ocean and the Arctic amplification. While sea ice melting is widespread over much of the perimeter of the Arctic Ocean in summer, sea ice remains to be thin in winter only in the Barents-Kara Seas. Excessive turbulent heat flux through the sea surface exposed to air due to sea ice melting warms the atmospheric column. Warmer air increases the downward longwave radiation and subsequently surface air temperature, which facilitates sea surface remains to be ice free. A 1 % reduction in sea ice concentration in winter leads to ~ 0.76 W m−2 increase in upward heat flux, ~ 0.07 K increase in 850 hPa air temperature, ~ 0.97 W m−2 increase in downward longwave radiation, and ~ 0.26 K increase in surface air temperature. This positive feedback mechanism is not clearly observed in the Laptev, East Siberian, Chukchi, and Beaufort Seas, since sea ice refreezes in late fall (November) before excessive turbulent heat flux is available for warming the atmospheric column in winter. A detailed seasonal heat budget is presented in order to understand specific differences between the Barents-Kara Seas and Laptev, East Siberian, Chukchi, and Beaufort Seas.

scholarly journals Total ozone trends and variability during 1979–2012 from merged datasets of various satellites

2013 ◽  
Vol 13 (11) ◽  
pp. 30407-30452 ◽  
Author(s):  
W. Chehade ◽  
J. P. Burrows ◽  
M. Weber
Keyword(s):  
Heat Flux ◽  
Solar Cycle ◽  
Trend Analysis ◽  
Total Ozone ◽  
Montreal Protocol ◽  
The Other ◽  
The Arctic ◽  
Eddy Heat Flux ◽  
Other Hand

Abstract. The study presents a~long term statistical trend analysis of total ozone datasets obtained from various satellites. A multi-variate linear regression was applied to annual mean zonal mean data using various natural and anthropogenic explanatory variables that represent dynamical and chemical processes which modify global ozone distributions in a changing climate. The study investigated the magnitude and zonal distribution of the different atmospheric chemical and dynamical factors to long-term total ozone changes. The regression model included the equivalent effective stratospheric chlorine (EESC), the 11 yr solar cycle, the Quasi-Biennial Oscillation (QBO), stratospheric aerosol loading describing the effects from major volcanic eruptions, the El Niño/Southern Oscillation (ENSO), the Arctic and Antarctic Oscillation (AO/AAO), and accumulated eddy heat flux (EHF), the latter representing changes due to the Brewer–Dobson circulation. The total ozone column dataset used here comprises the SBUV/TOMS/OMI merged data (1979–2012) MOD V8.0, the SBUV/SBUV-2 merged V8.6 and the merged GOME/SCIAMACHY/GOME-2 (GSG) WFDOAS merged data (1995–2012). The trend analysis was performed for twenty six 5° wide latitude bands from 65° S to 65° N, the analysis explained most of the ozone variability. The results show that QBO dominates the ozone variability in the tropics (±7 DU) while at higher latitudes, the dynamical indices, AO/AAO and eddy heat flux, have substantial influence on total ozone variations by up to ±10 DU. Volcanic aerosols are only prominent during the eruption periods and these together with the ENSO signal are more evident in the Northern Hemisphere. The signature of the solar cycle is evident over all latitudes and contributes about 10 DU from solar maximum to solar minimum. EESC is found to be a main contributor to the long-term ozone decline and the trend changes after the end of 1990s. A positive significant trend in total ozone columns is found after 1997 (between 1 and 8.2 DU decade−1) which points at the slowing of ozone decline and the onset of ozone recovery. The EESC based trends are compared with the trends obtained from the statistical piecewise linear trend (PWLT or hockey stick) model with a turnaround in 1997 to examine the differences between both approaches. Similar and significant pre-turnaround trends are observed. On the other hand, our results do indicate that the positive PWLT turnaround trends are larger than indicated by the EESC trends, however, they agree within 2-sigma, thus demonstrating the success of the Montreal Protocol phasing out of the ozone depleting substances (ODS). A sensitivity study is carried out by comparing the regression results, using SBUV MOD 8.0 merged time series (1979–2012) and a merged dataset combining TOMS/SBUV (1979–June 1995) and GOME/SCIAMACHY/GOME-2 ("GSG") WFDOAS (Weighting Function DOAS) (July 1995–2012) as well as SBUV/SBUV-2 MOD 8.6 (1979–2012) in the regression analysis in order to investigate the uncertainty in the long-term trends due to different ozone datasets and data versions. Replacing the late SBUV merged data record with GSG data (unscaled and adjusted) leads to very similar results demonstrating the high consistency between satellite datasets. However, the comparison of the new SBUV merged Mod V8.6 with the V8.0 data showed somewhat smaller sensitivities with regard to several proxies, however, the EESC and PWLT trends are very similar. On the other hand, the new MOD 8.6 data in the PWLT model revealed a~reduced ODS related upward trend after 1997.

scholarly journals The Life Cycle of the North Atlantic Storm Track*

2015 ◽  
Vol 72 (2) ◽  
pp. 821-833 ◽  
Author(s):  
Lenka Novak ◽  
Maarten H. P. Ambaum ◽  
Rémi Tailleux
Keyword(s):  
Heat Flux ◽  
Life Cycle ◽  
North Atlantic ◽  
Storm Track ◽  
High Heat ◽  
High Heat Flux ◽  
Dominant Type ◽  
The North ◽  
Eddy Heat Flux ◽  
The North Atlantic

Abstract The North Atlantic eddy-driven jet exhibits latitudinal variability with evidence of three preferred latitudinal locations: south, middle, and north. Here the authors examine the drivers of this variability and the variability of the associated storm track. The authors investigate the changes in the storm-track characteristics for the three jet locations and propose a mechanism by which enhanced storm-track activity, as measured by upstream heat flux, is responsible for cyclical downstream latitudinal shifts in the jet. This mechanism is based on a nonlinear oscillator relationship between the enhanced meridional temperature gradient (and thus baroclinicity) and the meridional high-frequency (periods of shorter than 10 days) eddy heat flux. Such oscillations in baroclinicity and heat flux induce variability in eddy anisotropy, which is associated with the changes in the dominant type of wave breaking and a different latitudinal deflection of the jet. The authors’ results suggest that high heat flux is conducive to a northward deflection of the jet, whereas low heat flux is conducive to a more zonal jet. This jet-deflecting effect was found to operate most prominently downstream of the storm-track maximum, while the storm track and the jet remain anchored at a fixed latitudinal location at the beginning of the storm track. These cyclical changes in storm-track characteristics can be viewed as different stages of the storm track’s spatiotemporal life cycle.

scholarly journals Thermal Regime of Ice Covered Swedish Lakes

1996 ◽  
Vol 27 (1-2) ◽  
pp. 39-56 ◽  
Author(s):  
Lars Bengtsson ◽  
Thorbjörn Svensson
Keyword(s):  
Heat Flux ◽  
Solar Radiation ◽  
Heat Source ◽  
Lake Water ◽  
Heat Budget ◽  
Heat Content ◽  
Heat Fluxes ◽  
Late Winter ◽  
Temperature Profiles ◽  
Early Winter

Temperature conditions and heat fluxes in ice covered lakes are discussed analyzing measurements in eight Swedish lakes. Heat fluxes from sediments and heat fluxes from water to ice are determined from temperature profiles. The contribution of solar radiation is estimated from heat-budget calculations. It is found that the heat content of most of the lakes changes very little when they are ice covered, but that the lake-water temperature slightly increases. All heat fluxes are small. The heat flux from the sediments is the highest flux in early winter, but is later in the winter balanced by the heat loss from the water to the underside of the ice. Solar radiation is an important heat source in late winter, when the snow cover is thin.

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 Modulation of Atmospheric Response to North Pacific SST Anomalies under Global Warming: A Statistical Assessment

2012 ◽  
Vol 25 (19) ◽  
pp. 6554-6566 ◽  
Author(s):  
Bolan Gan ◽  
Lixin Wu
Keyword(s):  
Global Warming ◽  
North Pacific ◽  
Climate Model ◽  
Storm Track ◽  
Early Winter ◽  
The North ◽  
Basin Scale ◽  
Climate Model Simulations ◽  
The North Pacific ◽  
Sst Anomalies

Abstract In this study the modulation of ocean-to-atmosphere feedback over the North Pacific in early winter from global warming is investigated based on both the observations and multiple climate model simulations from a statistical perspective. It is demonstrated that the basin-scale atmospheric circulation displays an equivalent barotropic ridge in response to warm SST anomalies in the Kuroshio–Oyashio Extension (KOE) region. This warm SST–ridge response in early winter can be enhanced significantly by global warming, indicating a strengthening of air–sea coupling over the North Pacific. This enhancement is likely associated with the intensification of storm tracks and, in turn, the amplification of atmospheric transient eddy feedback in a warm climate, although the secular trend of enhanced storm-track activity over the North Pacific is suggested to be biased in reanalysis product.

scholarly journals Estimating subpixel turbulent heat flux over leads from MODIS thermal infrared imagery with deep learning

2021 ◽  
Vol 15 (6) ◽  
pp. 2835-2856
Author(s):  
Zhixiang Yin ◽  
Xiaodong Li ◽  
Yong Ge ◽  
Cheng Shang ◽  
Xinyan Li ◽  
...  
Keyword(s):  
Heat Flux ◽  
Spatial Resolution ◽  
Arctic Region ◽  
Open Water ◽  
Turbulent Heat Flux ◽  
The Arctic ◽  
Turbulent Heat ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Thermal Infrared Imagery ◽  
Ice Surface Temperature

Abstract. The turbulent heat flux (THF) over leads is an important parameter for climate change monitoring in the Arctic region. THF over leads is often calculated from satellite-derived ice surface temperature (IST) products, in which mixed pixels containing both ice and open water along lead boundaries reduce the accuracy of calculated THF. To address this problem, this paper proposes a deep residual convolutional neural network (CNN)-based framework to estimate THF over leads at the subpixel scale (DeepSTHF) based on remotely sensed images. The proposed DeepSTHF provides an IST image and the corresponding lead map with a finer spatial resolution than the input IST image so that the subpixel-scale THF can be estimated from them. The proposed approach is verified using simulated and real Moderate Resolution Imaging Spectroradiometer images and compared with the conventional cubic interpolation and pixel-based methods. The results demonstrate that the proposed CNN-based method can effectively estimate subpixel-scale information from the coarse data and performs well in producing fine-spatial-resolution IST images and lead maps, thereby providing more accurate and reliable THF over leads.

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