scholarly journals Physical mechanisms of the seasonal, subseasonal, and high-frequency variability in the seasonal cycle of summer precipitation in Korea

2010 ◽  
Vol 115 (D14) ◽  
Author(s):  
Kwang-Yul Kim ◽  
Joon-Woo Roh ◽  
Dong-Kyou Lee ◽  
Jong-Ghap Jhun
Keyword(s):  
High Frequency ◽  
Seasonal Cycle ◽  
Summer Precipitation ◽  
Physical Mechanisms ◽  
High Frequency Variability

scholarly journals The Seasonal Cycle of Blocking and Associated Physical Mechanisms in the Australian Region and Relationship with Rainfall

2013 ◽  
Vol 141 (12) ◽  
pp. 4534-4553 ◽  
Author(s):  
M. J. Pook ◽  
J. S. Risbey ◽  
P. C. McIntosh ◽  
C. C. Ummenhofer ◽  
A. G. Marshall ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Seasonal Cycle ◽  
Seasonal Temperature ◽  
Ocean Fronts ◽  
Temperature Changes ◽  
Physical Mechanisms ◽  
Australian Region ◽  
Continental Antarctica ◽  
Positive Correlations ◽  
Blocking Index

Abstract The seasonal cycle of blocking in the Australian region is shown to be associated with major seasonal temperature changes over continental Antarctica (approximately 15°–35°C) and Australia (about 8°–17°C) and with minor changes over the surrounding oceans (below 5°C). These changes are superimposed on a favorable background state for blocking in the region resulting from a conjunction of physical influences. These include the geographical configuration and topography of the Australian and Antarctic continents and the positive west to east gradient of sea surface temperature in the Indo-Australian sector of the Southern Ocean. Blocking is represented by a blocking index (BI) developed by the Australian Bureau of Meteorology. The BI has a marked seasonal cycle that reflects seasonal changes in the strength of the westerly winds in the midtroposphere at selected latitudes. Significant correlations between the BI at Australian longitudes and rainfall have been demonstrated in southern and central Australia for the austral autumn, winter, and spring. Patchy positive correlations are evident in the south during summer but significant negative correlations are apparent in the central tropical north. By decomposing the rainfall into its contributions from identifiable synoptic types during the April–October growing season, it is shown that the high correlation between blocking and rainfall in southern Australia is explained by the component of rainfall associated with cutoff lows. These systems form the cyclonic components of blocking dipoles. In contrast, there is no significant correlation between the BI and rainfall from Southern Ocean fronts.

scholarly journals Interannual modulation of extratropical high frequency variability

1997 ◽  
Vol 40 (4) ◽  
Author(s):  
R. Caballero
Keyword(s):  
Normal Mode ◽  
Time Scales ◽  
High Frequency ◽  
Spherical Geometry ◽  
Simple Explanation ◽  
Space And Time ◽  
High Frequency Variability ◽  
Hemisphere Winter ◽  
Selection Of

A simple explanation is presented for the observed interannual changes in the dominant space and time scales of Northem Hemisphere winter extratropical high frequency variability. It is found that such changes can suc- cessfully be predicted by linearizing a 2-level quasi-geostrophic mode] in spherical geometry around the ob- served zona] mean states. The mechanisms responsible for the selection of the most unstable normal mode are investigated.

Modeling the Conditions for Microdroplets Formation and their Detachment from the Molten Metal on the Electrode

2021 ◽  
Vol 313 ◽  
pp. 1-7
Author(s):  
V.D. Sarychev ◽  
S.A. Solodsky ◽  
Sergey A. Nevskii ◽  
M.A. Kuznetsov ◽  
D.P. Ilyaschenko ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Molten Metal ◽  
High Frequency ◽  
Plasma Discharge ◽  
Pulse Action ◽  
Materials Processing ◽  
Physical Processes ◽  
Micro Scale ◽  
Physical Mechanisms ◽  
Frequency Pulse

Formation of nanostructure states on the surface of materials exposed to concentrated flows of energy is one of the relevant problems of modern materials processing. In the paper the authors describe the mechanism of the micro-scale droplets formation based on the study and modeling of the physical processes and technological aspects of the interaction between the heterogenic plasma flows and the molten substance at the electrode tip. The authors show new physical mechanisms and criteria for micro-and nanoparticles origination, develop a physical-mathematical model of the interaction between the molten metal and the plasma discharge with imposed high-frequency pulse action.

Hyperinsulinemia produces cardiac vagal withdrawal and nonuniform sympathetic activation in normal subjects

1999 ◽  
Vol 276 (1) ◽  
pp. R178-R183 ◽  
Author(s):  
Philippe Van De Borne ◽  
Martin Hausberg ◽  
Robert P. Hoffman ◽  
Allyn L. Mark ◽  
Erling A. Anderson
Keyword(s):  
High Frequency ◽  
Sympathetic Activity ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Low Frequency ◽  
Power Spectral Analysis ◽  
Normal Subjects ◽  
Power Spectral ◽  
Low Frequency Variability ◽  
High Frequency Variability

The exact mechanisms for the decrease in R-R interval (RRI) during acute physiological hyperinsulinemia with euglycemia are unknown. Power spectral analysis of RRI and microneurographic recordings of muscle sympathetic nerve activity (MSNA) in 16 normal subjects provided markers of autonomic control during 90-min hyperinsulinemic/euglycemic clamps. By infusing propranolol and insulin ( n = 6 subjects), we also explored the contribution of heightened cardiac sympathetic activity to the insulin-induced decrease in RRI. Slight decreases in RRI ( P < 0.001) induced by sevenfold increases in plasma insulin could not be suppressed by propranolol. Insulin increased MSNA by more than twofold ( P < 0.001), decreased the high-frequency variability of RRI ( P< 0.01), but did not affect the absolute low-frequency variability of RRI. These results suggest that reductions in cardiac vagal tone and modulation contribute at least in part to the reduction in RRI during hyperinsulinemia. Moreover, more than twofold increases in MSNA occurring concurrently with a slight and not purely sympathetically mediated tachycardia suggest regionally nonuniform increases in sympathetic activity during hyperinsulinemia in humans.

scholarly journals Hard-X-ray-selected active galactic nuclei – I. A radio view at high frequencies

2020 ◽  
Vol 495 (4) ◽  
pp. 3943-3960 ◽  
Author(s):  
E Chiaraluce ◽  
F Panessa ◽  
G Bruni ◽  
R D Baldi ◽  
E Behar ◽  
...  
Keyword(s):  
Radio Emission ◽  
Active Galactic Nuclei ◽  
High Frequency ◽  
Galactic Nuclei ◽  
High Frequencies ◽  
X Ray ◽  
Physical Mechanisms ◽  
Nuclear Contribution ◽  
Hot Corona ◽  
Shed Light

ABSTRACT A thorough study of radio emission in active galactic nuclei (AGNs) is of fundamental importance to understand the physical mechanisms responsible for the emission and the interplay between accretion and ejection processes. High-frequency radio observations can target the nuclear contribution of smaller emitting regions and are less affected by absorption. We present JVLA 22 and 45 GHz observations of 16 nearby (0.003 ≤ z ≤ 0.3) hard-X-ray-selected AGNs at the (sub)-kpc scale with tens μJy beam−1 sensitivity. We detected 15/16 sources, with flux densities ranging from hundreds μJy to tens Jy (specific luminosities from ∼1020 to ${\sim}10^{25}\, \mathrm{ W}\, \mathrm{ Hz}^{-1}$ at 22 GHz). All detected sources host a compact core, with eight being core-dominated at either frequencies, the others exhibiting also extended structures. Spectral indices range from steep to flat/inverted. We interpret this evidence as either due to a core+jet system (6/15), a core accompanied by surrounding star formation (1/15), to a jet oriented close to the line of sight (3/15), to emission from a corona or the base of a jet (1/15), although there might be degeneracies between different processes. Four sources require more data to shed light on their nature. We conclude that, at these frequencies, extended, optically thin components are present together with the flat-spectrum core. The LR/LX ∼ 10−5 relation is roughly followed, indicating a possible contribution to radio emission from a hot corona. A weakly significant correlation between radio core (22 and 45 GHz) and X-ray luminosities is discussed in the light of an accretion–ejection framework.

Response of Seasonal Simulations of a Regional Climate Model to High-Frequency Variability of Soil Moisture during the Summers of 1988 and 1993

2007 ◽  
Vol 8 (4) ◽  
pp. 738-757 ◽  
Author(s):  
Song Yang ◽  
S-H. Yoo ◽  
R. Yang ◽  
K. E. Mitchell ◽  
H. van den Dool ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Water Vapor ◽  
Diurnal Cycle ◽  
High Frequency ◽  
Large Scale ◽  
Climate Model ◽  
Regional Climate ◽  
Water Vapor Transport ◽  
Diurnal Variability ◽  
High Frequency Variability

Abstract This study employs the NCEP Eta Regional Climate Model to investigate the response of the model’s seasonal simulations of summer precipitation to high-frequency variability of soil moisture. Specifically, it focuses on the response of model precipitation and temperature over the U.S. Midwest and Southeast to imposed changes in the diurnal and synoptic variability of soil moisture in 1988 and 1993. High-frequency variability of soil moisture increases (decreases) precipitation in the 1988 drought (1993 flood) year in the central and southern-tier states, except along the Gulf Coast, but causes smaller changes in precipitation along the northern-tier states. The diurnal variability and synoptic variability of soil moisture produce similar patterns of precipitation change, indicating the importance of the diurnal cycle of land surface process. The increase (decrease) in precipitation is generally accompanied by a decrease (increase) in surface and lower-tropospheric temperatures, and the changes in precipitation and temperature are attributed to both the local effect of evaporation feedback and the remote influence of large-scale water vapor transport. The precipitation increase and temperature decrease in 1988 are accompanied by an increase in local evaporation and, more importantly, by an increase in the large-scale water vapor convergence into the Midwest and Southeast. Analogous but opposite-sign behavior occurs in 1993 (compared to 1988) in changes in precipitation, temperature, soil moisture, evaporation, and large-scale water vapor transport. Results also indicate that, in regions where the model simulates the diurnal cycle of soil moisture reasonably well, including this diurnal cycle in the simulations improves model performance. However, no notable improvement in model precipitation can be found in regions where the model fails to realistically simulate the diurnal variability of soil moisture.

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