scholarly journals The role of Pc1-2 waves in spectral broadening of SuperDARN echoes from high latitudes

2003 ◽  
Vol 30 (3) ◽  
Author(s):  
Pavlo V. Ponomarenko
Keyword(s):  
High Latitudes ◽  
Spectral Broadening

The role of subpolar North Atlantic as a source of predictability

2021 ◽  
Author(s):  
Shuting Yang ◽  
Tian Tian ◽  
Yiguo Wang ◽  
Torben Schmith ◽  
Steffen M. Olsen ◽  
...  
Keyword(s):  
North Atlantic ◽  
Decadal Variability ◽  
Model Systems ◽  
The Arctic ◽  
Ocean Temperature ◽  
High Latitudes ◽  
Cold Anomaly ◽  
Prediction Systems ◽  
The Impact

<p>The subpolar North Atlantic (SPNA) is a region experiencing substantial decadal variability, which has been linked to extreme weather impacts over continents. Recent studies have suggested that the connectivity with the SPNA may be a key to predictions in high latitudes. To understand the impact of the SPNA on predictability of North Atlantic-European sectors and the Arctic, we use two climate<strong> </strong>prediction systems, EC-Earth3-CPSAI and NorCPM1, to perform ensemble pacemaker experiments with a focus on the subpolar extreme cold anomaly event in 2015. This 2015 cold anomaly event is generally underestimated by the decadal prediction systems. In order to force the model to better represent the observed anomaly in SPNA, we apply nudging in a region of the SPNA (i.e., 51.5°W - 13.0°W, 30.4°N - 57.5°N, and from surface to 1000 m depth in the ocean). Here ocean temperature and salinity is restored to observed conditions from reanalysis in both model systems. All other aspects of the setup of this pacemaker experiment follow the protocol for the CMIP6 DCPP-A hindcasts and initialized on November 1, 2014. The restoration is applied during the hindcasts from November 2014 to December 2019. Multi-member ensembles of 10-year hindcasts are performed with 10 members for the EC-Earth3-CPSAI and 30 members for the NorCPM1.</p><p>The time evolution of ensembles of the initialized nudging hindcasts (EXP1) is compared with the initialized DCPP-A hindcast ensembles (EXP2) and the uninitialized ensembles (EXP3). The prediction skills of the three sets of experiments are also assessed. It can be seen that restoring the ocean temperature and salinity in the SPNA region to the reanalysis improves the prediction in the region quickly after the simulation starts, as expected. On the interannual to decadal time scales, the areas with improved prediction skills extend to over almost the entire North Atlantic for both models. The improved skill over Nordic Seas is particularly significant, especially for EC-Earth3-CPSAI. For NorCPM, the regions with improved skills extend to the entire Arctic. Our results suggest the possible role of the SPNA as a source of skillful predictions on interannual to decadal time scale, especially for high latitudes. The ocean pathways are the critical source of skill whereas our results imply a limited role of coupled feedbacks through the atmosphere.  </p>

scholarly journals High-latitude ocean ventilation and its role in Earth's climate transitions

2017 ◽  
Vol 375 (2102) ◽  
pp. 20160324 ◽  
Author(s):  
Alberto C. Naveira Garabato ◽  
Graeme A.  MacGilchrist ◽  
Peter J. Brown ◽  
D. Gwyn Evans ◽  
Andrew J. S. Meijers ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
High Latitude ◽  
Climate System ◽  
High Latitudes ◽  
Overturning Circulation ◽  
Ocean Ventilation ◽  
Earth’S Climate ◽  
Warming World ◽  
Climate Transitions

The processes regulating ocean ventilation at high latitudes are re-examined based on a range of observations spanning all scales of ocean circulation, from the centimetre scales of turbulence to the basin scales of gyres. It is argued that high-latitude ocean ventilation is controlled by mechanisms that differ in fundamental ways from those that set the overturning circulation. This is contrary to the assumption of broad equivalence between the two that is commonly adopted in interpreting the role of the high-latitude oceans in Earth's climate transitions. Illustrations of how recognizing this distinction may change our view of the ocean's role in the climate system are offered. This article is part of the themed issue ‘Ocean ventilation and deoxygenation in a warming world’.

Unexpected role of winter precipitation in determining heat requirement for spring vegetation green-up at northern middle and high latitudes

2014 ◽  
Vol 20 (12) ◽  
pp. 3743-3755 ◽  
Author(s):  
Yongshuo H Fu ◽  
Shilong Piao ◽  
Hongfang Zhao ◽  
Su-Jong Jeong ◽  
Xuhui Wang ◽  
...  
Keyword(s):  
Winter Precipitation ◽  
High Latitudes ◽  
Heat Requirement

scholarly journals The role of ice in N<sub>2</sub>O<sub>5</sub> heterogeneous hydrolysis at high latitudes

2008 ◽  
Vol 8 (4) ◽  
pp. 12595-12624 ◽  
Author(s):  
R. L. Apodaca ◽  
D. M. Huff ◽  
W. R. Simpson
Keyword(s):  
Steady State ◽  
Nitric Acid ◽  
Surface Area ◽  
High Latitude ◽  
Acid Production ◽  
High Latitudes ◽  
Air Masses ◽  
Mixing Ratios ◽  
Reactive Surfaces

Abstract. We report evidence for ice catalyzing N2O5 heterogeneous hydrolysis from a study conducted near Fairbanks, AK in November 2007. Mixing ratios of N2O5, NO, NO2, and ozone are reported and are used to determine steady state N2O5 lifetimes. When air masses are sub-saturated with respect to ice, the data show longer lifetimes (≈20 min) and elevated N2O5 levels, while ice-saturated air masses show shorter lifetimes (≈6 min) and suppressed N2O5 levels. We also report estimates of aerosol surface area densities that are on the order of 50 μm2/cm3, a surface area density that is insufficient to explain the rapid losses of N2O5 observed in this study, reinforcing the importance of other reactive surfaces such as ice. Ice-saturated pollution plumes are ubiquitous in high latitudes; therefore, catalysis on these surfaces is largely responsible for nocturnal processing of N2O5 leading to nitric acid production and loss of NOx in high latitude plumes.

scholarly journals Geologic isolation of nuclear waste at high latitudes: the role of ice sheets

Geofluids ◽  
2012 ◽  
Vol 12 (1) ◽  
pp. 1-6 ◽  
Author(s):  
M. Person ◽  
J. McIntosh ◽  
N. Iverson ◽  
C. E. Neuzil ◽  
V. Bense
Keyword(s):  
Nuclear Waste ◽  
Ice Sheets ◽  
High Latitudes

Experiments on the role of amplitude and phase modulations during transition to turbulence

1982 ◽  
Vol 123 ◽  
pp. 1-29 ◽  
Author(s):  
R. W. Miksad ◽  
F. L. Jones ◽  
E. J. Powers ◽  
Y. C. Kim ◽  
L. Khadra
Keyword(s):  
Dominant Role ◽  
Modulation Frequency ◽  
Power Spectra ◽  
Transition Process ◽  
Transition To Turbulence ◽  
Nonlinear Interactions ◽  
Spectral Broadening ◽  
Energy Redistribution ◽  
Difference Mode

The transition of a laminar two-dimensional wake is studied experimentally to establish the role of amplitude and phase modulations in the spectral-broadening and energy-redistribution process. Multiple instability modes fo and fi are triggered by acoustic excitation. The spectrum of the fluctuating velocity field formed by the growing and interacting instabilities shows the development of a complicated side- band structure reminiscent of amplitude- and phase-modulated waves. Digital com- plex demodulation techniques are used to obtain quantitative measurements of local instantaneous amplitude and phase modulations. Measurements of the modulation time traces, their modulation indices, the lag between phase and amplitude modula- tions, and the power spectra of the modulations are presented. Our results show that both phase and amplitude modulation play a role in the transition process. The dominant modulation frequency of both amplitude and phase is that of the difference mode fv = f1−f0 produced by the interaction of the two excited instabilities. Phase modulation becomes progressively more important as transition proceeds down- stream, and seems to play the dominant role in the spectral-broadening and energy- redistribution process. Measurements of the bicoherency spectrum indicate that sideband structures, and accompanying modulations, are produced by nonlinear interactions between the low-frequency difference mode and higher-frequency in- stability modes. Some limited measurements indicate that finite-amplitude induced nonlinear dispersion effects ω(k, a2) may provide a physical mechanism by which amplitude modulations generated by nonlinear interactions can induce simultaneous phase modulations.

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