Nonlinear forcing mechanisms of the terdiurnal solar tide and their impact on the zonal mean circulation

Abstract. We investigate the forcing mechanisms of the terdiurnal solar tide in the middle atmosphere using a mechanistic global circulation model. In order to quantify their individual contributions, we perform several model experiments and separate each forcing mechanism by switching off the remaining sources. We find that the primary excitation is owing to the terdiurnal component of solar radiation absorption in the troposphere and stratosphere. Secondary sources are nonlinear tide-tide interactions and gravity wave-tide interactions. Thus, although the solar heating clearly dominates the terdiurnal forcing in our simulations, we find that nonlinear tidal and gravity wave interactions contribute in certain seasons and altitudes. By slightly enhancing the different excitation sources, we test the sensitivity of the background circulation on these changes of the dynamics. As a result, the increase of terdiurnal gravity wave drag can strongly affect the middle and upper atmosphere dynamics, including an irregular change of the terdiurnal amplitude, a weakening of neutral winds in the thermosphere, and a significant temperature change in the thermosphere, depending on the strength of the forcing. On the contrary, the influence of nonlinear tidal interactions on the middle atmosphere background dynamics is rather small.

Download Full-text

Nonlinear forcing mechanisms of the migrating terdiurnal solar tide and their impact on the zonal mean circulation

Annales Geophysicae ◽

10.5194/angeo-37-943-2019 ◽

2019 ◽

Vol 37 (5) ◽

pp. 943-953 ◽

Cited By ~ 3

Author(s):

Friederike Lilienthal ◽

Christoph Jacobi

Keyword(s):

Gravity Wave ◽

Middle Atmosphere ◽

Circulation Model ◽

Wave Drag ◽

Radiation Absorption ◽

Global Circulation Model ◽

Secondary Sources ◽

Tidal Interactions ◽

Solar Tide ◽

Forcing Mechanisms

Abstract. We investigate the forcing mechanisms of the terdiurnal solar tide in the middle atmosphere using a mechanistic global circulation model. In order to quantify their individual contributions, we perform several model experiments and separate each forcing mechanism by switching off the remaining sources. We find that the primary excitation is owing to the terdiurnal component of solar radiation absorption in the troposphere and stratosphere. Secondary sources are nonlinear tide–tide interactions and gravity wave–tide interactions. Thus, although the solar heating clearly dominates the terdiurnal forcing in our simulations, we find that nonlinear tidal and gravity wave interactions contribute in certain seasons and at certain altitudes. By slightly enhancing the different excitation sources, we test the sensitivity of the background circulation to these changes of the dynamics. As a result, the increase of terdiurnal gravity wave drag can strongly affect the middle and upper atmosphere dynamics, including an irregular change of the terdiurnal amplitude, a weakening of neutral winds in the thermosphere, and a significant temperature change in the thermosphere, depending on the strength of the forcing. On the contrary, the influence of nonlinear tidal interactions on the middle atmosphere background dynamics is rather small.

Download Full-text

Observations on Cardiac Output and ”Pulmonary Blood Volume” in Normal Man by External Recording of the Intracardiac Flow of 131I Labelled Albumin

Nuklearmedizin ◽

10.1055/s-0037-1621159 ◽

1961 ◽

Vol 1 (04) ◽

pp. 353-379

Author(s):

Jacques Lammerant ◽

Norman Veall ◽

Michel De Visscher

Keyword(s):

Cardiac Output ◽

Blood Volume ◽

Normal Subjects ◽

Published Data ◽

Total Blood Volume ◽

Total Blood ◽

Pulmonary Blood Volume ◽

Intracardiac Flow ◽

Normal Man ◽

Mean Circulation

Summary1. The technique for the measurement of cardiac output by external recording of the intracardiac flow of 131I labelled human serum albumin has been extended to provide a measure of the mean circulation time from right to left heart and hence a new approach to the estimation of the pulmonary blood volume.2. Values for the basal cardiac output in normal subjects and its variations with age are in good agreement with the previously published data of other workers.3. The pulmonary blood volume in normal man in the basal state was found to be 28.2 ± 0.6% of the total blood volume.4. There was no correlation between cardiac output and pulmonary blood volume in a series of normal subjects in the basal state.5. The increase in cardiac output during digestion was associated with a decrease in pulmonary blood volume equal to 6.3 ± 1.2% of the total blood volume, that is, about 280 ml.6. The increase in cardiac output during exercise was associated with a decrease in pulmonary blood volume equal to 4.5 ± 1.0% of the total blood volume, that is, about 200 ml.7. The increase in cardiac output attributed to alarm is not associated with a decrease in pulmonary blood volume, the latter may in fact be increased.8. The total blood volume is advocated as a standard of reference for studies of this type in normal subjects in preference to body weight or surface area.9. The significance of these results and the validity of the method are discussed.

Download Full-text

The Diurnal and the Semidiurnal Atmospheric Solar Tide

Tellus ◽

10.3402/tellusa.v10i4.9269 ◽

1958 ◽

Vol 10 (4) ◽

pp. 415-429

Author(s):

P. Thrane

Keyword(s):

Solar Tide

Download Full-text

Identification of the mechanisms responsible for anomalies in the tropical lower thermosphere/ionosphere caused by the January 2009 sudden stratospheric warming

Journal of Space Weather and Space Climate ◽

10.1051/swsc/2019037 ◽

2019 ◽

Vol 9 ◽

pp. A39 ◽

Cited By ~ 1

Author(s):

Maxim V. Klimenko ◽

Vladimir V. Klimenko ◽

Fedor S. Bessarab ◽

Timofei V. Sukhodolov ◽

Pavel A. Vasilev ◽

...

Keyword(s):

Electric Field ◽

Phase Change ◽

Lower Thermosphere ◽

Upper Atmosphere ◽

Electron Content ◽

Stratospheric Warming ◽

Sudden Stratospheric Warming ◽

Low Latitude ◽

Plasma Drift ◽

Solar Tide

We apply the Entire Atmosphere GLobal (EAGLE) model to investigate the upper atmosphere response to the January 2009 sudden stratospheric warming (SSW) event. The model successfully reproduces neutral temperature and total electron content (TEC) observations. Using both model and observational data, we identify a cooling in the tropical lower thermosphere caused by the SSW. This cooling affects the zonal electric field close to the equator, leading to an enhanced vertical plasma drift. We demonstrate that along with a SSW-related wind disturbance, which is the main source to form a dynamo electric field in the ionosphere, perturbations of the ionospheric conductivity also make a significant contribution to the formation of the electric field response to SSW. The post-sunset TEC enhancement and pre-sunrise electron content reduction are revealed as a response to the 2009 SSW. We show that at post-sunset hours the SSW affects low-latitude TEC via a disturbance of the meridional electric field. We also show that the phase change of the semidiurnal migrating solar tide (SW2) in the neutral wind caused by the 2009 SSW at the altitude of the dynamo electric field generation has a crucial importance for the SW2 phase change in the zonal electric field. Such changes lead to the appearance of anomalous diurnal variability of the equatorial electromagnetic plasma drift and subsequent low-latitudinal TEC disturbances in agreement with available observations. Plain Language Summary – Entire Atmosphere GLobal model (EAGLE) interactively calculates the troposphere, stratosphere, mesosphere, thermosphere, and plasmasphere–ionosphere system states and their response to various natural and anthropogenic forcing. In this paper, we study the upper atmosphere response to the major sudden stratospheric warming that occurred in January 2009. Our results agree well with the observed evolution of the neutral temperature in the upper atmosphere and with low-latitude ionospheric disturbances over America. For the first time, we identify an SSW-related cooling in the tropical lower thermosphere that, in turn, could provide additional information for understanding the mechanisms for the generation of electric field disturbances observed at low latitudes. We show that the SSW-related vertical electromagnetic drift due to electric field disturbances is a key mechanism for interpretation of an observed anomalous diurnal development of the equatorial ionization anomaly during the 2009 SSW event. We demonstrate that the link between thermospheric winds and the ionospheric dynamo electric field during the SSW is attained through the modulation of the semidiurnal migrating solar tide.

Download Full-text

Widespread increase in dynamic imbalance in the Getz region of Antarctica from 1994 to 2018

Nature Communications ◽

10.1038/s41467-021-21321-1 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Heather L. Selley ◽

Anna E. Hogg ◽

Stephen Cornford ◽

Pierre Dutrieux ◽

Andrew Shepherd ◽

...

Keyword(s):

Drainage Basin ◽

Satellite Observations ◽

Driving Mechanism ◽

West Antarctica ◽

Mean Sea Level ◽

The Past ◽

Global Mean Sea Level ◽

Forcing Mechanisms ◽

Global Mean ◽

Term Response

AbstractThe Getz region of West Antarctica is losing ice at an increasing rate; however, the forcing mechanisms remain unclear. Here we use satellite observations and an ice sheet model to measure the change in ice speed and mass balance of the drainage basin over the last 25-years. Our results show a mean increase in speed of 23.8 % between 1994 and 2018, with three glaciers accelerating by over 44 %. Speedup across the Getz basin is linear, with speedup and thinning directly correlated confirming the presence of dynamic imbalance. Since 1994, 315 Gt of ice has been lost contributing 0.9 ± 0.6 mm global mean sea level, with increased loss since 2010 caused by a snowfall reduction. Overall, dynamic imbalance accounts for two thirds of the mass loss from this region of West Antarctica over the past 25-years, with a longer-term response to ocean forcing the likely driving mechanism.

Download Full-text

Springtime Upwelling and Its Formation Mechanism in Coastal Waters of Manaung Island, Myanmar

Remote Sensing ◽

10.3390/rs12223777 ◽

2020 ◽

Vol 12 (22) ◽

pp. 3777

Author(s):

Yuhui Li ◽

Yun Qiu ◽

Jianyu Hu ◽

Cherry Aung ◽

Xinyu Lin ◽

...

Keyword(s):

Surface Layer ◽

Satellite Remote Sensing ◽

Subsurface Layer ◽

World Ocean ◽

Remote Sensing Data ◽

Remote Forcing ◽

Forcing Mechanisms ◽

World Ocean Atlas ◽

The Impact ◽

Local Wind Forcing

Multisource satellite remote sensing data and the World Ocean Atlas 2018 (WOA18) temperature and salinity dataset have been used to analyze the spatial distribution, variability and possible forcing mechanisms of the upwelling off Manaung Island, Myanmar. Signals of upwelling exist off the coasts of Manaung Island, in western Myanmar during spring. It appears in February, reaches its peak in March and decays in May. Low-temperature (<28.3 °C) and high-salinity (>31.8 psu) water at the surface of this upwelling zone is caused by the upwelling of seawater from a depth below 100 m. The impact of the upwelling on temperature is more significant in the subsurface layer than that in the surface layer. In contrast, the impact of the upwelling on salinity in the surface layer is more significant. Further research reveals that the remote forcing from the equator predominantly induces the evolution of the upwelling, while the local wind forcing also contributes to strengthen the intensity of the upwelling during spring.

Download Full-text

Mechanisms Associated with Large Daily Rainfall Events in Northeast Brazil

Journal of Climate ◽

10.1175/2010jcli3457.1 ◽

2011 ◽

Vol 24 (2) ◽

pp. 376-396 ◽

Cited By ~ 16

Author(s):

Brant Liebmann ◽

George N. Kiladis ◽

Dave Allured ◽

Carolina S. Vera ◽

Charles Jones ◽

...

Keyword(s):

Daily Rainfall ◽

Annual Rainfall ◽

Northeast Brazil ◽

Kelvin Wave ◽

Rainfall Events ◽

Independent Events ◽

Precipitation Anomalies ◽

Wave Trains ◽

Using Data ◽

Forcing Mechanisms

Abstract The mechanisms resulting in large daily rainfall events in Northeast Brazil are analyzed using data filtering to exclude periods longer than 30 days. Composites of circulation fields that include all independent events do not reveal any obvious forcing mechanisms as multiple patterns contribute to Northeast Brazil precipitation variability. To isolate coherent patterns, subsets of events are selected based on anomalies that precede the Northeast Brazil precipitation events at different locations. The results indicate that at 10°S, 40°W, the area of lowest annual rainfall in Brazil, precipitation occurs mainly in association with trailing midlatitude synoptic wave trains originating in either hemisphere. Closer to the equator at 5°S, 37.5°W, an additional convection precursor is found to the west, with a spatial structure consistent with that of a Kelvin wave. Although these two sites are located within only several hundred kilometers of each other and the midlatitude patterns that induce precipitation appear to be quite similar, the dates on which large precipitation anomalies occur at each location are almost entirely independent, pointing to separate forcing mechanisms.

Download Full-text

Response of Freshwater Flux and Sea Surface Salinity to Variability of the Atlantic Warm Pool

Journal of Climate ◽

10.1175/jcli-d-12-00284.1 ◽

2013 ◽

Vol 26 (4) ◽

pp. 1249-1267 ◽

Cited By ~ 14

Author(s):

Chunzai Wang ◽

Liping Zhang ◽

Sang-Ki Lee

Keyword(s):

Central America ◽

North Atlantic ◽

Warm Pool ◽

Sea Surface ◽

Sea Surface Salinity ◽

Freshwater Flux ◽

Surface Salinity ◽

Atlantic Warm Pool ◽

Mean Circulation ◽

Circulation Dynamics

Abstract The response of freshwater flux and sea surface salinity (SSS) to the Atlantic warm pool (AWP) variations from seasonal to multidecadal time scales is investigated by using various reanalysis products and observations. All of the datasets show a consistent response for all time scales: A large (small) AWP is associated with a local freshwater gain (loss) to the ocean, less (more) moisture transport across Central America, and a local low (high) SSS. The moisture budget analysis demonstrates that the freshwater change is dominated by the atmospheric mean circulation dynamics, while the effect of thermodynamics is of secondary importance. Further decomposition points out that the contribution of the mean circulation dynamics primarily arises from its divergent part, which mainly reflects the wind divergent change in the low level as a result of SST change. In association with a large (small) AWP, warmer (colder) than normal SST over the tropical North Atlantic can induce anomalous low-level convergence (divergence), which favors anomalous ascent (decent) and thus generates more (less) precipitation. On the other hand, a large (small) AWP weakens (strengthens) the trade wind and its associated westward moisture transport to the eastern North Pacific across Central America, which also favors more (less) moisture residing in the Atlantic and hence more (less) precipitation. The results imply that variability of freshwater flux and ocean salinity in the North Atlantic associated with the AWP may have the potential to affect the Atlantic meridional overturning circulation.

Download Full-text