scholarly journals On a simple, data-aided analytic description of the morphology of equatorial F-region zonal plasma drifts

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Samuel A. Shidler ◽  
Fabiano S. Rodrigues
Keyword(s):  
Zonal Wind ◽  
Solar Flux ◽  
Vertical Shear ◽  
Analytic Description ◽  
Horizontal Wind ◽  
Analytic Model ◽  
Vertical Drift ◽  
Plasma Drifts ◽  
December Solstice ◽  
Different Seasons

AbstractWe present results of an effort to evaluate the ability of an analytic model to describe the behavior of the equatorial zonal plasma drifts given inputs provided by readily available climatological models of thermospheric and ionospheric parameters. In a data-model fusion approach, we used vertical drift measurements to drive the model and zonal drift measurements to evaluate its output. Drift measurements were made by the Jicamarca incoherent scatter radar, and model results were evaluated for different seasons and two distinct solar flux conditions. We focused, in particular, on model results for different versions of the Horizontal Wind Model (HWM 97, 07, and 14). We found that, despite its simplicity, the analytic model can reproduce fairly well most of the features in the observed zonal plasma drifts, including the vertical shear associated with the evening plasma vortex. During daytime hours the model predicts similar results for the zonal drifts independently of the HWM used to drive the model. More importantly, the modeled daytime drifts match exceptionally well the behavior and magnitude of the observed drifts for all seasons and solar flux conditions considered. The nighttime results drive the overall performance of the analytic model, and we found that a single HWM cannot provide the best results for all seasons and solar flux conditions. We also examined the main sources of zonal drift variability. Most of the morphology is controlled by the zonal wind dynamo term of the analytic model, but with non-negligible contribution from the vertical drift term. Finally, we examined the contribution from the E- and F-region to the zonal wind dynamo. The morphology of the zonal drifts in the region of observation (240–560 km altitude) is controlled mostly by the F-region winds, but with significant contributions from the daytime E-region particularly during December solstice and low solar flux conditions.

scholarly journals Characteristics of Stratospheric Winds over Jiuquan (41.1°N, 100.2°E) Using Rocketsonde Data in 1967–2004

2017 ◽  
Vol 34 (3) ◽  
pp. 657-667 ◽  
Author(s):  
Z. Sheng ◽  
J. W. Li ◽  
Y. Jiang ◽  
S. D. Zhou ◽  
W. L. Shi
Keyword(s):  
Zonal Wind ◽  
Middle Atmosphere ◽  
Correlation Coefficients ◽  
Meridional Wind ◽  
Horizontal Wind ◽  
Cycle Period ◽  
Observation Data ◽  
Wind Fields ◽  
Zonal Winds ◽  
Model Research

AbstractStratospheric winds play a significant role in middle atmosphere dynamics, model research, and carrier rocket experiments. For the first time, 65 sets of rocket sounding experiments conducted at Jiuquan (41.1°N, 100.2°E), China, from 1967 to 2004 are presented to study horizontal wind fields in the stratosphere. At a fixed height, wind speed obeys the lognormal distribution. Seasonal mean winds are westerly in winter and easterly in summer. In spring and autumn, zonal wind directions change from the upper to the lower stratosphere. The monthly zonal mean winds have an annual cycle period with large amplitudes at high altitudes. The correlation coefficients for zonal winds between observations and the Horizontal Wind Model (HWM) with all datasets are 0.7. The MERRA reanalysis is in good agreement with rocketsonde data according to the zonal winds comparison with a coefficient of 0.98. The sudden stratospheric warming is an important contribution to biases in the HWM, because it changes the zonal wind direction in the midlatitudes. Both the model and the reanalysis show dramatic meridional wind differences with the observation data.

scholarly journals On strongly nonlinear gravity waves in a vertically sheared atmosphere

2020 ◽  
Vol 6 (1) ◽  
pp. 63-74
Author(s):  
Mark Schlutow ◽  
Georg S. Voelker
Keyword(s):  
Gravity Waves ◽  
Lower Layer ◽  
Vertical Shear ◽  
Horizontal Wind ◽  
Necessary Condition ◽  
Mean Flow ◽  
Individual Layer ◽  
Strongly Nonlinear ◽  
The Mean ◽  
The Stability

Abstract We investigate strongly nonlinear stationary gravity waves which experience refraction due to a thin vertical shear layer of horizontal background wind. The velocity amplitude of the waves is of the same order of magnitude as the background flow and hence the self-induced mean flow alters the modulation properties to leading order. In this theoretical study, we show that the stability of such a refracted wave depends on the classical modulation stability criterion for each individual layer, above and below the shearing. Additionally, the stability is conditioned by novel instability criteria providing bounds on the mean-flow horizontal wind and the amplitude of the wave. A necessary condition for instability is that the mean-flow horizontal wind in the upper layer is stronger than the wind in the lower layer.

scholarly journals A Wind Study of Venus’s Cloud Top: New Doppler Velocimetry Observations

Atmosphere ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 2
Author(s):  
Ruben Gonçalves ◽  
Pedro Machado ◽  
Thomas Widemann ◽  
Francisco Brasil ◽  
José Ribeiro
Keyword(s):  
Spatial Variability ◽  
Local Time ◽  
Zonal Wind ◽  
Meridional Wind ◽  
Space Mission ◽  
Horizontal Wind ◽  
Doppler Velocimetry ◽  
Middle Latitudes ◽  
Wind Velocities ◽  
Wind Stability

At Venus’s cloud top, the circulation is dominated by the superroration, where zonal wind speed peaks at ∼100 ms−1, in the low-to-middle latitudes. The constraining of zonal and meridional circulations is essential to understanding the mechanisms driving the superrotation of Venus’s atmosphere, which are still poorly understood. We present new Doppler velocimetry measurements of horizontal wind velocities at Venus’s cloud top, around 70 km altitude. These results were based on March 2015 observations at the Canada–France–Hawaii Telescope (CFHT, Mauna Kea, Hawaii), using ESPaDOnS. The Doppler velocimetry method used has already successfully provided zonal and meridional results in previous works led by P. Machado and R. Gonçalves, proving to be a good reference ground-based technique in the study of the dynamics of Venus’s atmosphere. These observations were carried out between 27 and 29 March 2015, using the Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) which provides simultaneous visible-near IR spectra from 370 to 1050 nm, with a spectral resolution of 81000 allowing wind field characterization in the scattered Franuhofer solar lines by Venus’s cloud top on the dayside. The zonal velocities are consistent with previous results while also showing evidence of spatial variability, along planetocentric latitude and longitude (local-time). The meridional wind circulation presents a notably constant latitudinal structure with null velocities at lower latitudes, below 10∘ N–S, and peak velocities of ∼30 ms−1, centered around 35∘ N–S. The uncertainty of the meridional wind results from ground observations is of the same order as the uncertainty of meridional wind retrieved by space-based observations using cloud-tracking, as also shown by previous work led by R. Gonçalves and published in 2020. These March 2015 measurements present a unique and valuable contribution to the study of horizontal wind at the cloud top, from a period when Doppler velocimetry was the only available method to do so, since no space mission was orbiting Venus between Venus Express ending in January 2015 and Akatsuki’s orbit insertion in December 2015. These results from new observations provide (1) constraints on zonal wind temporal and spatial variability (latitude and local time), (2) constraints on the meridional wind latitudinal profile, (3) additional evidence of zonal and meridional wind stability for the period between 2011 and 2015 (along previous Doppler results) (4) further evidence of the consistency and robustness of our Doppler velocimetry method.

scholarly journals Future Changes in the Ozone Quasi-Biennial Oscillation with Increasing GHGs and Ozone Recovery in CCMI Simulations

2017 ◽  
Vol 30 (17) ◽  
pp. 6977-6997 ◽  
Author(s):  
Hiroaki Naoe ◽  
Makoto Deushi ◽  
Kohei Yoshida ◽  
Kiyotaka Shibata
Keyword(s):  
Zonal Wind ◽  
Climate Model ◽  
Vertical Shear ◽  
Quasi Biennial Oscillation ◽  
The Past ◽  
Meteorological Research Institute ◽  
Climate Simulations ◽  
The Future ◽  
Ozone Depleting Substances ◽  
Biennial Oscillation

The future quasi-biennial oscillation (QBO) in ozone in the equatorial stratosphere is examined by analyzing transient climate simulations due to increasing greenhouse gases (GHGs) and decreasing ozone-depleting substances under the auspices of the Chemistry–Climate Model Initiative. The future (1960–2100) and historical (1979–2010) simulations are conducted with the Meteorological Research Institute Earth System Model. Three climate periods, 1960–85 (past), 1990–2020 (present), and 2040–70 (future) are selected, corresponding to the periods before, during, and after ozone depletion. The future ozone QBO is characterized by increases in amplitude by 15%–30% at 5–10 hPa and decreases by 20%–30% at 40 hPa, compared with the past and present climates; the future and present ozone QBOs increase in amplitude by up to 60% at 70 hPa, compared with the past climate. The increased amplitude at 5–10 hPa suggests that the temperature-dependent photochemistry plays an important role in the enhanced future ozone QBO. The weakening of vertical shear in the zonal wind QBO is responsible for the decreased amplitude at 40 hPa in the future ozone QBO. An interesting finding is that the weakened zonal wind QBO in the lowermost tropical stratosphere is accompanied by amplified QBOs in ozone, vertical velocity, and temperature. Further study is needed to elucidate the causality of amplification about the ozone and temperature QBOs under climate change in conditions of zonal wind QBO weakening.

scholarly journals Influence of Quasi-Periodic Oscillation of Atmospheric Variables on Radiation Fog over A Mountainous Region of Korea

Atmosphere ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 230
Author(s):  
Inyeob La ◽  
Seong Soo Yum ◽  
Ismail Gultepe ◽  
Jae Min Yeom ◽  
Jae In Song ◽  
...  
Keyword(s):  
Periodic Oscillation ◽  
Vertical Shear ◽  
Horizontal Wind ◽  
Simultaneous Increase ◽  
Mountainous Region ◽  
Helmholtz Instability ◽  
Radiation Fog ◽  
Quasi Periodic Oscillation ◽  
Time Frequency ◽  
Atmospheric Variables

To enhance our understanding of fog processes over complex terrain, various fog events that occurred during the International Collaborative Experiments for Pyeongchang 2018 Winter Olympics and Paralympics (ICE-POP) campaign were selected. Investigation of thermodynamic, dynamic, and microphysical conditions within fog layers affected by quasi-periodic oscillation of atmospheric variables was conducted using observations from a Fog Monitor-120 (FM-120) and other in-situ meteorological instruments. A total of nine radiation fog cases that occurred in the autumn and winter seasons during the campaign over the mountainous region of Pyeongchang, Korea were selected. The wavelet analysis was used to study quasi-period oscillations of dynamic, microphysical, and thermodynamic variables. By decomposing the time series into the time-frequency space, we can determine both dominant periods and how these dominant periods change in time. Quasi-period oscillations of liquid water content (LWC), pressure, temperature, and horizontal/vertical velocity, which have periods of 15–40 min, were observed during the fog formation stages. We hypothesize that these quasi-periodic oscillations were induced by Kelvin–Helmholtz instability. The results suggest that Kelvin–Helmholtz instability events near the surface can be explained by an increase in the vertical shear of horizontal wind and by a simultaneous increase in wind speed when fog forms. In the mature stages, fluctuations of the variables did not appear near the surface anymore.

scholarly journals Mountain-Wave Turbulence Encounter of the Research Aircraft HALO above Iceland

2020 ◽  
Vol 59 (3) ◽  
pp. 567-588 ◽  
Author(s):  
Martina Bramberger ◽  
Andreas Dörnbrack ◽  
Henrike Wilms ◽  
Florian Ewald ◽  
Robert Sharman
Keyword(s):  
Polar Front ◽  
Vertical Shear ◽  
Horizontal Wind ◽  
Mountain Wave ◽  
Horizontal Wind Speed ◽  
Wind Speeds ◽  
Research Aircraft ◽  
Strong Surface ◽  
Flight Level ◽  
Thrust Control

AbstractStrong turbulence was encountered by the German High-Altitude Long-Range Research Aircraft (HALO) at flight level 430 (13.8 km) on 13 October 2016 above Iceland. In this event the turbulence caused altitude changes of the research aircraft of about 50 m within a period of approximately 15 s. Additionally, the automatic thrust control of the HALO could not control the large gradients in the horizontal wind speed and, consequently, the pilot had to switch off this system. Simultaneously, the French Falcon of Service des Avions Français Instrumentés pour la Recherche en Environnement (SAFIRE), flying 2 km below HALO, also encountered turbulence at almost the same location. On that day, mountain-wave (MW) excitation and propagation was favored by the alignment of strong surface winds and the polar front jet. We use a combination of in situ observations, ECMWF and empirical turbulence forecasts, and high-resolution simulations to characterize the observed turbulent event. These show that a pronounced negative vertical shear of the horizontal wind favored overturning and breaking of MWs in the area of the encountered turbulence. The turbulent region was tilted upstream and extended over a distance of about 2 km in the vertical. The analyses suggest that HALO was flying through the center of a breaking MW field while the French Falcon encountered the lower edge of this region. Surprisingly, the pronounced gradients in the horizontal wind speeds leading to the deactivation of the automatic thrust control were located north of the breaking MW field. In this area, our analysis suggests the presence of gravity waves that could have generated the encountered modulation of the horizontal wind field.

scholarly journals Vertical and longitudinal electron density structures of equatorial E- and F-regions

2011 ◽  
Vol 29 (1) ◽  
pp. 81-89 ◽  
Author(s):  
P. S. Brahmanandam ◽  
Y.-H. Chu ◽  
K.-H. Wu ◽  
H.-P. Hsia ◽  
C.-L. Su ◽  
...  
Keyword(s):  
Electron Density ◽  
Phase Relation ◽  
F Region ◽  
Good Consistency ◽  
June Solstice ◽  
December Solstice ◽  
Different Seasons ◽  
E Region ◽  
First Time ◽  
Longitudinal Structures

Abstract. From global soundings of ionospheric electron density made with FORMOSAT 3/COSMIC satellites for September 2006–August 2009, day-night variations in vertical and longitudinal structures of the electron densities in equatorial E- and F-regions for different seasons are investigated for the first time. The results reveal that the wavenumber-3 and wavenumber-4 patterns dominated the nighttime (22:00–04:00 LT) F-region longitudinal structures in solstice and in equinox seasons, respectively. In daytime (08:00–18:00 LT) F-region, the wavenumber-4 patterns governed the longitudinal structures in the September equinox and December solstice, and wavenumber-3 in March equinox and June solstice respectively. A comparison of the daytime and nighttime longitudinal electron density structures indicates that they are approximately 180° out of phase with each other. It is believed that this out of phase relation is very likely the result of the opposite phase relation between daytime and nighttime nonmigrating diurnal tidal winds that modulate background E-region dynamo electric field at different places, leading to the day-night change in the locations of the equatorial plasma fountains that are responsible for the formation of the F-region longitudinal structures. Further, a good consistency between the locations of the density structures in the same seasons of the different years for both daytime and nighttime epochs has been noticed indicating that the source mechanism for these structures could be the same.

scholarly journals Nighttime morphology of vertical plasma drifts at Ouagadougou during different seasons and phases of sunspot cycles 20–22

2015 ◽  
Vol 120 (11) ◽  
pp. 10020-10038 ◽  
Author(s):  
B. O. Adebesin ◽  
A. B. Rabiu ◽  
J. O. Adeniyi ◽  
C. Amory‐Mazaudier
Keyword(s):  
Plasma Drifts ◽  
Different Seasons

Tropical cyclone genesis and trajectory characteristics in the western north Pacific

2020 ◽  
Author(s):  
Rui Xiong ◽  
Mengqian Lu
Keyword(s):  
Tropical Cyclone ◽  
Zonal Wind ◽  
Environmental Conditions ◽  
North Pacific ◽  
Western North Pacific ◽  
Data Science ◽  
Clustering Algorithm ◽  
The Philippines ◽  
Vertical Shear ◽  
Gaussian Kernel

<p>The western North Pacific (WNP) is one of the most active tropical cyclone (TC) regions, which can inflict enormous death and massive property damage to surrounding areas. Although many studies about tropical cyclone activities on multi-timescales have been done, most of them focus on the entire basin, variations within the basin deserve more investigations. Besides TC characteristics on different timescales, to investigate the impacts of environment variables on TC and provide informative factors for prediction is another concern in the research community. In this study, we adopt several data science techniques, including Gaussian kernel estimator, wavelet, cross-wavelet coherence and regression analyses, to explore the spatiotemporal variations of TC genesis and associated environmental conditions. Significant semiannual and annual variations of TC genesis have been found in the northern South China Sea (NSCS) and oceanic areas east of the Philippines (OAEP). In the southeast part of WNP (SEWNP), TC genesis shows prominent variations on ENSO time scale. With reconstructed TC series on those frequencies, we further quantify the influences of environmental variables on the primary TC signals over WNP. About 40% of the identified TC variance over NSCS and OAEP can be explained by variability in vertical shear of zonal wind and relative humidity. In the SEWNP, TC genesis reveals strong nonlinear and non-stationary relationships with vertical shear of zonal wind and absolute vorticity. Besides, A probabilistic clustering algorithm is used to describe the TC tracks in the WNP. The best track dataset from JMA is decomposed into three clusters based on genesis location and curvature. For each cluster, we analyze the relationships between TC properties, such as genesis location, trajectory and intensity, and associated environmental conditions using the self-organizing map. The spatial patterns of sea surface temperature have huge impacts on TC genesis location, while the trajectory is largely influenced by geopotential height.</p>

scholarly journals Moving Cellular Structure of Fog Echoes Obtained with a Millimeter-Wave Scanning Doppler Radar at Kushiro, Japan

2005 ◽  
Vol 44 (8) ◽  
pp. 1260-1273 ◽  
Author(s):  
Akihisa Uematsu ◽  
Hiroyuki Hashiguchi ◽  
Michihiro Teshiba ◽  
Hisamichi Tanaka ◽  
Koichi Hirashima ◽  
...  
Keyword(s):  
Millimeter Wave ◽  
Cellular Structure ◽  
Doppler Radar ◽  
Radar Reflectivity ◽  
Vertical Shear ◽  
Horizontal Wind ◽  
Shear Line ◽  
Position Indicator ◽  
Advection Fog

Abstract Observations of fogs with a millimeter-wave scanning Doppler radar were conducted at Kushiro in Hokkaido, Japan, in the summer seasons of 1999 and 2000. Three typical types of plan position indicator (PPI) displays were observed: cellular echoes with high radar reflectivity factors (∼−10 dBZ), uniformly distributed echoes with high reflectivities (∼−10 dBZ), and uniformly distributed echoes with low reflectivities (∼−30 dBZ). The authors focused on advection fog with cellular echoes observed on 5 August 1999 and 31 July 2000. Echoes showed structures of cells with a reflectivity of −10 dBZ and with intervals of about 1 km. This echo pattern moved northward (i.e., from the sea to the land). There was a vertical shear of the horizontal wind at a height around 200 m in both cases, and structures of each cell were upright above the shear line and were leaning below it. The direction and the speed of the echo pattern in both PPI and range–height indicator (RHI) displays agreed well with that of the horizontal wind at heights above the shear (200 m). In the echo cells, existence of drizzle drops is implied.

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