scholarly journals Latitudinal variability of the quasi-16-day wave in the middle atmosphere over Brazilian stations

2016 ◽  
Vol 34 (4) ◽  
pp. 411-419 ◽  
Author(s):  
Amitava Guharay ◽  
Paulo Prado Batista ◽  
Barclay Robert Clemesha ◽  
Ricardo Arlen Buriti ◽  
Nelson Jorge Schuch
Keyword(s):  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Reanalysis Data ◽  
Lower Latitude ◽  
Meteor Radar ◽  
Background Wind ◽  
Short Period ◽  
General Preference ◽  
Santa Maria ◽  
Zonal Propagation

Abstract. A comparative study of the quasi-16-day wave (QSDW) in the middle atmosphere using meteor radar observations and reanalysis data from three Brazilian stations, Sao Joao do Cariri (7.4° S, 36.5° W) (CA), Cachoeira Paulista (22.7° S, 45° W) (CP), and Santa Maria (29.7° S, 53.7° W) (SM) has been carried out in the year 2005 to delineate its latitudinal variability characteristics. The broad spectral behavior around 16-day periodicity may indicate multiple modes of the concerned wave component. The wave amplitude shows a number of peaks over the year with the largest one in summer and winter in the case of mesosphere–lower thermosphere (MLT) and stratosphere, respectively. A potential coupling of the concerned wave with other short period planetary waves, especially at CA and CP is evinced. Although zonal propagation exhibits both eastward as well as westward waves there is a general preference of eastward waves at mid-latitude and westward waves at tropical latitudes. The prevailing westerly background wind in the middle atmosphere is conceived to favor the wave filtering of westward propagating Rossby waves at lower latitude.

scholarly journals El Niño influence on the mesosphere/lower thermosphere circulation at midlatitudes as seen by a VHF meteor radar at Collm (51.3 ° N, 13 ° E)

2017 ◽  
Vol 15 ◽  
pp. 199-206 ◽  
Author(s):  
Christoph Jacobi ◽  
Tatiana Ermakova ◽  
Daniel Mewes ◽  
Alexander I. Pogoreltsev
Keyword(s):  
El Niño ◽  
Middle Atmosphere ◽  
El Nino ◽  
Lower Thermosphere ◽  
Circulation Model ◽  
Wind Effect ◽  
Meteor Radar ◽  
Global Circulation Model ◽  
Height Range ◽  
Zonal Winds

Abstract. Mesosphere/lower thermosphere (MLT) zonal winds continuously measured by a VHF meteor radar at Collm, Germany (51.3° N, 13.0° E) in the height range 82 – 97 km from 2004 to date are analyzed with respect to the signature of El Niño. The comparison of Niño3 equatorial SST index and MLT wind time series shows that in January and especially in February zonal winds are positively correlated with the Niño3 index. We note a delay of about one month of the MLT zonal wind effect with respect to equatorial sea surface temperature variability. The signal is strong for the upper altitudes (above 90 km) accessible to the radar observations, but weakens with decreasing height. This reflects the fact that during El Niño years the westerly winter middle atmosphere wind jet is weaker, and this is also the case with the easterly lower thermospheric jet. Owing to the reversal of the absolute El Niño signal from negative to positive with altitude, at the height of the maximum meteor flux, which is around 90 km, the El Niño signal is weak. The experimental results can be qualitatively reproduced by numerical experiments using a mechanistic global circulation model with prescribed tropospheric temperatures and latent heat release for El Niño and La Niña conditions.

scholarly journals Observation of Kelvin-Helmholtz Instabilities and gravity waves in the summer mesopause above Andenes in Northern Norway

2018 ◽  
Author(s):  
Gunter Stober ◽  
Svenja Sommer ◽  
Carsten Schult ◽  
Ralph Latteck ◽  
Jorge L. Chau
Keyword(s):  
Gravity Waves ◽  
Vertical Structure ◽  
Middle Atmosphere ◽  
Meteor Radar ◽  
Helmholtz Instability ◽  
Beam Experiment ◽  
Short Period ◽  
Strong Shear ◽  
Summer Echoes ◽  
Period Wave

Abstract. We present observations obtained with the Middle Atmosphere Alomar Radar System (MAARSY) to investigate short period wave-like features using polar mesospheric summer echoes (PMSE) as tracer for the neutral dynamics. We conducted a multi-beam experiment including 67 different beam directions during a 9-day campaign in June 2013. We identified two Kelvin Helmholtz Instability (KHI) events from the signal morphology of PMSE. The MAARSY observations are complemented by collocated meteor radar wind data to determine the mesoscale gravity wave activity and the vertical structure of the wind field above the PMSE. The KHIs occurred in a strong shear flow with Richardson numbers Ri 

scholarly journals Multi-year observations of gravity wave momentum fluxes at low and middle latitudes inferred by all-sky meteor radar

2015 ◽  
Vol 33 (9) ◽  
pp. 1183-1193 ◽  
Author(s):  
V. F. Andrioli ◽  
P. P. Batista ◽  
B. R. Clemesha ◽  
N. J. Schuch ◽  
R. A. Buriti
Keyword(s):  
Gravity Wave ◽  
Lower Thermosphere ◽  
Data Series ◽  
Meteor Radar ◽  
Meridional Component ◽  
Middle Latitudes ◽  
Zonal Component ◽  
Short Period ◽  
Momentum Fluxes ◽  
Seasonal Analysis

Abstract. We have applied a modified composite day analysis to the Hocking (2005) technique to study gravity wave (GW) momentum fluxes in the mesosphere and lower thermosphere (MLT). Wind measurements from almost continuous meteor radar observations during June 2004–December 2008 over São João do Cariri (Cariri; 7° S, 36° W), April 1999–November 2008 over Cachoeira Paulista (CP; 23° S, 45° W), and February 2005–December 2009 over Santa Maria (SM; 30° S, 54° W) were used to estimate the GW momentum fluxes and variances in the MLT region. Our analysis can provide monthly mean altitude profiles of vertical fluxes of horizontal momentum for short-period (less than 2–3 h) GWs. The averages for each month throughout the entire data series have shown different behavior for the momentum fluxes depending on latitude and component. The meridional component has almost the same behavior at the three sites, being positive (northward), for most part of the year. On the other hand, the zonal component shows different behavior at each location: it is positive for almost half the year at Cariri and SM but predominantly negative over CP. Annual variation in the GW momentum fluxes is present at all sites in the zonal component and also in SM at 89 km in the meridional component. The seasonal analysis has also shown a 4-month oscillation at 92.5 km over SM in the zonal component and over CP at the same altitudes but for the meridional component.

scholarly journals Statistical characteristics of gravity wave activities observed by an OH airglow imager at Xinglong, in northern China

2011 ◽  
Vol 29 (8) ◽  
pp. 1401-1410 ◽  
Author(s):  
Q. Li ◽  
J. Xu ◽  
J. Yue ◽  
W. Yuan ◽  
X. Liu
Keyword(s):  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Northern China ◽  
Lower Atmosphere ◽  
Statistical Characteristics ◽  
Meridional Direction ◽  
Short Period ◽  
Different Seasons ◽  
One Year ◽  
Almost All

Abstract. An all-sky airglow imager (ASAI) was installed at Xinglong, in northern China (40.2° N, 117.4° E) in November 2009 to study the morphology of atmospheric gravity waves (AGWs) in the mesosphere and lower thermosphere (MLT) region. Using one year of OH airglow imager data from December 2009 to November 2010, the characteristics of short-period AGWs are investigated and a yearlong AGW climatology in northern China is first ever reported. AGW occurrence frequency in summer and winter is higher than that in equinoctial months. Observed bands mainly have horizontal wavelengths from 10 to 35 km, observed periods from 4 to 14 min and observed horizontal phase speeds in the range of 30 to 60 m s−1. Most of the bands propagate in the meridional direction. The propagation directions of the bands show a strong southwestward preference in winter, while almost all bands propagate northeastward in summer. Although the wind filtering in the middle atmosphere may control AGW propagations in the zonal direction, the non-uniform distribution of wave sources in the lower atmosphere may contribute to the anisotropy in the meridional direction in different seasons. Additionally, as an indication of local instability, the characteristics of ripples are also analyzed. It also shows seasonal variations, occurring more often in summer and winter and mainly moving westward in summer and eastward in winter.

scholarly journals Intradiurnal wind variations observed in the lower thermosphere over the South Pole

2000 ◽  
Vol 18 (5) ◽  
pp. 547-554 ◽  
Author(s):  
Y. I. Portnyagin ◽  
J. M. Forbes ◽  
E. G. Merzlyakov ◽  
N. A. Makarov ◽  
S. E. Palo
Keyword(s):  
Middle Atmosphere ◽  
Lamb Waves ◽  
Lower Thermosphere ◽  
Winter Season ◽  
Internal Gravity Wave ◽  
Wave Number ◽  
South Pole ◽  
Seasonal Behavior ◽  
Linear Interaction ◽  
Short Period

Abstract. The first meteor radar measurements of meridional winds in the lower thermosphere (about 95 ± 5 km), along four azimuth directions: 0°, 90°E, 180° and 90°W; approximately 2° from the geographic South Pole were made during two observational campaigns: January 19, 1995-January 26, 1996, and November 21, 1996-January 27, 1997. Herein we report analyses of the measurement results, obtained during the first campaign, which cover the whole one-year period, with particular emphasis on the transient nature and seasonal behavior of the main parameters of the intradiurnal wind oscillations. To analyze the data, two complementary methods are used: the well-known periodogram (FFT) technique and the S-transform technique. The most characteristic periods of the intradiurnal oscillations are found to be rather uniformly spread between about 7 h and 12 h. All of these oscillations are westward-propagating with zonal wave number s=1 and their usual duration is confined to several periods. During the austral winter season the oscillations with periods less than 12 h are the most intensive, while during summer season the 12-h oscillations dominate. Lamb waves and internal-gravity wave propagation, non-linear interaction of the short-period tides, excitation in situ of the short period waves may be considered as possible processes which are responsible for intradiurnal wind oscillations in the lower thermosphere over South Pole.Key words: Meteorology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; waves and tides)

scholarly journals Interhemispheric comparison of mesosphere/lower thermosphere winds from GAIA, WACCM-X and ICON-UA simulations and meteor radar observations at mid- and polar latitudes

2021 ◽  
Author(s):  
Gunter Stober ◽  
Ales Kuchar ◽  
Dimitry Pokhotelov ◽  
Huixin Liu ◽  
Hanli Liu ◽  
...  
Keyword(s):  
Climate Model ◽  
Middle Atmosphere ◽  
Spatial Scales ◽  
Lower Thermosphere ◽  
Winter Season ◽  
Meteor Radar ◽  
Radar Observations ◽  
Meridional Winds ◽  
Free Running ◽  
Seasonal Characteristic

<p>There is a growing scientific interest to investigate the forcing from the middle atmosphere dynamics on the thermosphere and ionosphere. This forcing is driven by atmospheric waves at various temporal and spatial scales. In this study, we cross-compare the nudged models Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA) and Whole Atmosphere Community Climate Model Extended</p><p>Version (Specified dynamics) ( WACCM-X(SD)), a free-running version of Upper Atmosphere ICOsahedral Non-hydrostatic (ICON-UA) with six meteor radars located at conjugate polar and mid-latitudes. Mean winds, diurnal and semidiurnal tidal amplitudes and phases were obtained from the radar observations at the mesosphere and lower thermosphere (MLT) and compared to the GAIA, WACCM-X(SD), and ICON-UA data for similar locations applying a harmonized diagnostic.</p><p>Our results indicate that GAIA zonal and meridional winds show a good agreement to the meteor radars during the winter season on both hemispheres, whereas WACCM-X(SD) and ICON-UA seem to reproduce better the summer zonal wind reversal. However, the mean winds also exhibit some deviation in the seasonal characteristic concerning the meteor radar measurements, which are attributed to the gravity wave parameterizations implemented in the models. All three models tend to reflect the seasonality of diurnal tidal amplitudes, but show some dissimilarities in tidal phases. We also found systematic interhemispheric differences in the seasonal characteristic of semidiurnal amplitudes and phases. The free-running ICON-UA apparently shows most of these interhemispheric differences, whereas WACCM-X(SD) and GAIA trend to have better agreement of the semidiurnal tidal variability in the northern hemisphere.</p>

scholarly journals Interannual Variability and Trends in Sea Surface Temperature, Lower and Middle Atmosphere Temperature at Different Latitudes for 1980–2019

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 454
Author(s):  
Andrew R. Jakovlev ◽  
Sergei P. Smyshlyaev ◽  
Vener Y. Galin
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Lower Stratosphere ◽  
Middle Atmosphere ◽  
Southern Oscillation ◽  
Lower Troposphere ◽  
Reanalysis Data ◽  
Sea Surface ◽  
The Arctic ◽  
The Impact

The influence of sea-surface temperature (SST) on the lower troposphere and lower stratosphere temperature in the tropical, middle, and polar latitudes is studied for 1980–2019 based on the MERRA2, ERA5, and Met Office reanalysis data, and numerical modeling with a chemistry-climate model (CCM) of the lower and middle atmosphere. The variability of SST is analyzed according to Met Office and ERA5 data, while the variability of atmospheric temperature is investigated according to MERRA2 and ERA5 data. Analysis of sea surface temperature trends based on reanalysis data revealed that a significant positive SST trend of about 0.1 degrees per decade is observed over the globe. In the middle latitudes of the Northern Hemisphere, the trend (about 0.2 degrees per decade) is 2 times higher than the global average, and 5 times higher than in the Southern Hemisphere (about 0.04 degrees per decade). At polar latitudes, opposite SST trends are observed in the Arctic (positive) and Antarctic (negative). The impact of the El Niño Southern Oscillation phenomenon on the temperature of the lower and middle atmosphere in the middle and polar latitudes of the Northern and Southern Hemispheres is discussed. To assess the relative influence of SST, CO2, and other greenhouse gases’ variability on the temperature of the lower troposphere and lower stratosphere, numerical calculations with a CCM were performed for several scenarios of accounting for the SST and carbon dioxide variability. The results of numerical experiments with a CCM demonstrated that the influence of SST prevails in the troposphere, while for the stratosphere, an increase in the CO2 content plays the most important role.

Diurnal and seasonal variability of short-period gravity waves at ∼40° N using meteor radar wind observations

2021 ◽  
Author(s):  
Caixia Tian ◽  
Xiong Hu ◽  
Alan Z. Liu ◽  
Zhaoai Yan ◽  
Qingchen Xu ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Seasonal Variability ◽  
Meteor Radar ◽  
Short Period

scholarly journals Large-Scale Waves in the Mesosphere and Lower Thermosphere Observed by SABER

2005 ◽  
Vol 62 (12) ◽  
pp. 4384-4399 ◽  
Author(s):  
Rolando R. Garcia ◽  
Ruth Lieberman ◽  
James M. Russell ◽  
Martin G. Mlynczak
Keyword(s):  
Large Scale ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Normal Modes ◽  
Zonal Winds ◽  
Broadband Emission ◽  
Summer Hemisphere ◽  
Mean Structure ◽  
Mesosphere And Lower Thermosphere ◽  
The Tropics

Abstract Observations made by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on board NASA’s Thermosphere–Ionosphere–Mesosphere Energetics and Dynamics (TIMED) satellite have been processed using Salby’s fast Fourier synoptic mapping (FFSM) algorithm. The mapped data provide a first synoptic look at the mean structure and traveling waves of the mesosphere and lower thermosphere (MLT) since the launch of the TIMED satellite in December 2001. The results show the presence of various wave modes in the MLT, which reach largest amplitude above the mesopause and include Kelvin and Rossby–gravity waves, eastward-propagating diurnal oscillations (“non-sun-synchronous tides”), and a set of quasi-normal modes associated with the so-called 2-day wave. The latter exhibits marked seasonal variability, attaining large amplitudes during the solstices and all but disappearing at the equinoxes. SABER data also show a strong quasi-stationary Rossby wave signal throughout the middle atmosphere of the winter hemisphere; the signal extends into the Tropics and even into the summer hemisphere in the MLT, suggesting ducting by westerly background zonal winds. At certain times of the year, the 5-day Rossby normal mode and the 4-day wave associated with instability of the polar night jet are also prominent in SABER data.

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