Water vapour and the equatorial mesospheric semi-annual oscillation (MSAO)

Abstract. Observations of the mesospheric semi-annual oscillation (MSAO) in the equatorial region have been reported dating back several decades. Seasonal variations in both species densities and airglow emissions are well documented. The extensive observations available offer an excellent case study for comparison with model simulations. A broad range of MSAO measurements is summarised with emphasis on the 80–100 km region. The objective here is not to address directly the complicated driving forces of the MSAO, but rather to employ a combination of observations and model simulations to estimate the limits of some of the underlying dynamical processes. Photochemical model simulations are included for near-equinox and near-solstice conditions, the two times with notable differences in the observed MSAO parameters. Diurnal tides are incorporated in the model to facilitate comparisons of observations made at different local times. The roles of water vapour as the "driver" species and ozone as the "response" species are examined to test for consistency between the model results and observations. The simulations suggest the interactions between vertical eddy diffusion and background vertical advection play a significant role in the MSAO phenomenon. Further, the simulations imply there are rigid limits on vertical advection rates and eddy diffusion rates. For August at the Equator, 90 km altitude, the derived eddy diffusion rate is approximately 1 × 106 cm2 s−1 and the vertical advection is upwards at 0.8 cm s−1. For April the corresponding values are 4 × 105 cm2 s−1 and 0.1 cm s−1. These results from the current 1-D model simulations will need to be verified by a full 3-D simulation. Exactly how vertical advection and eddy diffusion are related to gravity wave momentum as discussed by Dunkerton (1982) three decades ago remains to be addressed.

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Comparison of Global Datasets of Sodium Densities in the Mesosphere and Lower Thermosphere from GOMOS, SCIAMACHY and OSIRIS Measurements and WACCM Model Simulations from 2008 to 2012

10.5194/amt-2016-416 ◽

2017 ◽

Author(s):

Martin P. Langowski ◽

Christian von Savigny ◽

John P. Burrows ◽

Didier Fussen ◽

Erin C. M. Dawkins ◽

...

Keyword(s):

Seasonal Cycle ◽

Lower Thermosphere ◽

Temporal Variations ◽

Equatorial Region ◽

Local Times ◽

Vertical Column ◽

Model Simulations ◽

Mesosphere And Lower Thermosphere ◽

Summer Minimum ◽

Global Datasets

Abstract. During the last decade, multiple limb sounding satellites have measured the global sodium (Na) number densities in the mesosphere and lower thermosphere (MLT).Datasets are now available from GOMOS, SCIAMACHY (both on Envisat) and OSIRIS/Odin. Furthermore, global model simulations of the Na layer in the MLT simulated with WACCM-Na are available. In this paper, we compare these global datasets. Globally, there is an agreement in the observed and simulated monthly average of Na vertical column densities that were compared with each other. They show a clear seasonal cycle with a summer minimum most pronounced at the poles. They also show signs of a semi-annual oscillation in the equatorial region. The vertical column densities vary between 0.5 × 109 cm−2 to 7 × 109 cm−2 near the poles and between 3 × 109 cm−2 to 4 × 109 cm−2 at the equator. The phase of the seasonal cycle and semi-annual oscillation shows small differences between the different instruments. The full width at half maximum of the profiles is 10 to 16 km for most latitudes, but significantly smaller in the polar summer. The centroid altitudes of the measured sodium profiles range from 89 to 95 km, while the model shows on average 2 to 4 km lower centroid altitudes. This coincides with a 3 km lower mesopause altitude in the WACCM simulations compared to measurements, which may be the reason for the low centroid altitudes. Despite this global 2 to 4 km shift, the model captures latitudinal and temporal variations. The variation of the WACCM dataset during the year at different latitudes is similar to the one of the measurements. Furthermore, the differences between the measured profiles with different instruments and therefore different local times are also present in the model simulated profiles. This capturing of latitutinal and temporal variations is also found for the vertical column densities and profile widths.

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Comparison of global datasets of sodium densities in the mesosphere and lower thermosphere from GOMOS, SCIAMACHY and OSIRIS measurements and WACCM model simulations from 2008 to 2012

Atmospheric Measurement Techniques ◽

10.5194/amt-10-2989-2017 ◽

2017 ◽

Vol 10 (8) ◽

pp. 2989-3006 ◽

Cited By ~ 2

Author(s):

Martin P. Langowski ◽

Christian von Savigny ◽

John P. Burrows ◽

Didier Fussen ◽

Erin C. M. Dawkins ◽

...

Keyword(s):

Seasonal Cycle ◽

Climate Model ◽

Lower Thermosphere ◽

Temporal Variations ◽

Equatorial Region ◽

Local Times ◽

Vertical Column ◽

Model Simulations ◽

Mesosphere And Lower Thermosphere ◽

Scanning Imaging

Abstract. During the last decade, several limb sounding satellites have measured the global sodium (Na) number densities in the mesosphere and lower thermosphere (MLT). Datasets are now available from Global Ozone Monitoring by Occultation of Stars (GOMOS), the SCanning Imaging Absorption spectroMeter for Atmospheric CHartography (SCIAMACHY) (both on Envisat) and the Optical Spectrograph and InfraRed Imager System (OSIRIS) (on Odin). Furthermore, global model simulations of the Na layer in the MLT simulated by the Whole Atmosphere Community Climate Model, including the Na species (WACCM-Na), are available. In this paper, we compare these global datasets.The observed and simulated monthly averages of Na vertical column densities agree reasonably well with each other. They show a clear seasonal cycle with a summer minimum most pronounced at the poles. They also show signs of a semi-annual oscillation in the equatorial region. The vertical column densities vary from 0. 5 × 109 to 7 × 109 cm−2 near the poles and from 3 × 109 to 4 × 109 cm−2 at the Equator. The phase of the seasonal cycle and semi-annual oscillation shows small differences between the Na amounts retrieved from different instruments. The full width at half maximum of the profiles is 10 to 16 km for most latitudes, but significantly smaller in the polar summer. The centroid altitudes of the measured sodium profiles range from 89 to 95 km, whereas the model shows on average 2 to 4 km lower centroid altitudes. This may be explained by the mesopause being 3 km lower in the WACCM simulations than in measurements. Despite this global 2–4 km shift, the model captures well the latitudinal and temporal variations. The variation of the WACCM dataset during the year at different latitudes is similar to the one of the measurements. Furthermore, the differences between the measured profiles with different instruments and therefore different local times (LTs) are also present in the model-simulated profiles. This capturing of latitudinal and temporal variations is also found for the vertical column densities and profile widths.

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Cultural societies and information needs: Croats in New Zealand

Global Knowledge Memory and Communication ◽

10.1108/gkmc-02-2019-0017 ◽

2019 ◽

Vol 68 (8/9) ◽

pp. 652-673 ◽

Cited By ~ 1

Author(s):

Maja Krtalić ◽

Ivana Hebrang Grgić

Keyword(s):

Content Analysis ◽

New Zealand ◽

Significant Role ◽

Social Life ◽

Information Dissemination ◽

Home Country ◽

Immigrant Communities ◽

Technological Changes ◽

Content Type

Purpose The purpose of this paper was to explore how small immigrant communities in host countries collect, disseminate and present information about their home country and their community, and the role of formal societies and clubs in it. Design/methodology/approach This paper presents the results of a case study of the Croatian community in New Zealand. To illustrate how cultural and technological changes affected information dissemination and communication within the community, the case study presents both historical and current situations. Methods used in this case study included a content analysis of historical newspapers published in New Zealand by the Croatian community, content analysis of current webpages and social networking sites, and interviews with participants who have management roles in Croatian societies and communities in New Zealand. Data were collected from December 2018 to February 2019. Findings Formally established clubs and societies, but also informal groups of immigrants and their descendants can play a significant role in providing their members with information about the culture, social life and events of the home country. They also play a significant role in preserving part of the history and heritage which is relevant, not only for a specific community but also for the history and culture of a home country. Originality/value The methodology used in the research is based on data from community archives and can be used for studying other small immigrant communities in New Zealand or abroad. The case study presented in the paper illustrates how the information environment of small immigrant communities develops and changes over the years under the influence of diverse political, social and technological changes.

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Indoor Thermal Comfort Analysis: A Case Study of Modern and Traditional Buildings in Hot-Arid Climatic Region of Ethiopia

Urban Science ◽

10.3390/urbansci5030053 ◽

2021 ◽

Vol 5 (3) ◽

pp. 53

Author(s):

Haven Hailu ◽

Eshetu Gelan ◽

Yared Girma

Keyword(s):

Thermal Comfort ◽

Significant Role ◽

Indoor Environment ◽

Thermal Sensation ◽

Climatic Region ◽

Contributing Factors ◽

Objective Measurements ◽

Indoor Thermal Comfort ◽

Adaptive Comfort

Indoor thermal comfort is an essential aspect of sustainable architecture and it is critical in maintaining a safe indoor environment. Expectations, acceptability, and preferences of traditional and modern buildings are different in terms of thermal comfort. This study, therefore, attempts to evaluate the indoor thermal comforts of modern and traditional buildings and identify the contributing factors that impede or facilitate indoor thermal comfort in Semera city, Ethiopia. This study employed subjective and objective measurements. The subjective measurement is based on the ASHRAE seven-point thermal sensation scale. An adaptive comfort model was employed according to the ASHRAE standard to evaluate indoor thermal comfort. The results revealed that with regards to thermal sensational votes between −1 and +1, 88% of the respondents are satisfied with the indoor environment in traditional houses, while in modern houses this figure is 22%. Likewise, 83% of occupants in traditional houses expressed a preference for their homes to remain the same or be only slightly cooler or warmer. Traditional houses were, on average, in compliance with the 80% acceptability band of the adaptive comfort standard. The study investigated that traditional building techniques and materials, in combination with consideration of microclimate, were found to play a significant role in regulating the indoor environment.

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On the isotopic composition of precipitation in tropical stations (*).

Acta Amazonica ◽

10.1590/1809-43921985152139 ◽

1985 ◽

Vol 15 (1-2) ◽

pp. 121-140 ◽

Cited By ~ 20

Author(s):

Roberto Gonfiantini

Keyword(s):

Isotopic Composition ◽

Water Vapour ◽

Seasonal Variations ◽

Pacific Islands ◽

Continental Effect ◽

The Mean

Some of the trends and characteristics of the isotopic composition oh precipitation in tropical stations are discussed. Stations in small Pacific islands show a variation with latitude, with lower 8-values between 15°N and 1S°S and higher values at higher. Inland stations are depleted in heavy isotopes with respect to coastal stations but sometimes this continental effect is rather complex, as f,or instance in África. Mean monthly 8-values show a remarkable correlation with the amount of precipitation, but the slope variations do not show a clear dependence on the mean long term 8-value,as should be expected theoretically. In Southern American stations the seasonal variations of the meanmonthly 5-values are correlated and they are greater in inland stations due to con-tinentaly. The possible effects of recycling of water vapour by evapotranspiration are also discussed.

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Twin mesospheric bores observed over Brazilian equatorial region

Annales Geophysicae ◽

10.5194/angeo-34-91-2016 ◽

2016 ◽

Vol 34 (1) ◽

pp. 91-96 ◽

Cited By ~ 6

Author(s):

A. F. Medeiros ◽

I. Paulino ◽

M. J. Taylor ◽

J. Fechine ◽

H. Takahashi ◽

...

Keyword(s):

Equatorial Region ◽

Temperature Profiles ◽

Meteor Radar ◽

Airglow Emissions

Abstract. Two consecutive mesospheric bores were observed simultaneously by two all-sky cameras on 19 December 2006. The observations were carried out in the northeast of Brazil at two different stations: São João do Cariri (36.5° W, 7.4° S) and Monteiro (37.1° W, 7.9° S), which are by about 85 km apart. The mesospheric bores were observed within an interval of ∼  3 h in the NIR OH and OI557.7 nm airglow emissions. Both bores propagated to the east and showed similar characteristics. However, the first one exhibited a dark leading front with several trailing waves behind and progressed into a brighter airglow region, while the second bore, observed in the OH layer, was comprised of several bright waves propagating into a darker airglow region. This is the first paper to report events like these, called twin mesospheric bores. The background of the atmosphere during the occurrence of these events was studied by considering the temperature profiles from the TIMED/SABER satellite and wind from a meteor radar.

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Bisnis Vlogging dalam Industri Media Digital di Indonesia

Jurnal ILMU KOMUNIKASI ◽

10.24002/jik.v15i1.1007 ◽

2018 ◽

Vol 15 (1) ◽

Author(s):

Jimi Narotama Mahameruaji ◽

Lilis Puspitasari ◽

Evi Rosfiantika ◽

Detta Rahmawan

Keyword(s):

Social Media ◽

Digital Media ◽

Media Studies ◽

Significant Role ◽

Support Systems ◽

Media Industry ◽

Video Content ◽

New Business ◽

Digital Media Studies

This study explores the phenomenon of Vlogger as a new business in the digital media industry in Indonesia. Vlogger refer to social media users who regularly upload a variety of video content with various themes. We used case study to describe and analyze Youtube’s significant role in managing Vlogger communities, and also design support systems to make the communities growth and sustainable. We also explore Vlogger role as Online Influencer. This study is expected to be one of the references related to Vlogger phenomenon in the context of digital media studies in Indonesia.

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SACRALISATION AND THE COLONIAL-INDIGENOUS ENCOUNTER IN SOUTHERN AFRICAN CHRISTIAN HISTORY: THE MEMORY AND LEGACY OF JOHANNES DU PLESSIS AS CASE STUDY

Studia Historiae Ecclesiasticae ◽

10.25159/2412-4265/375 ◽

2015 ◽

Vol 41 (2) ◽

pp. 82-99 ◽

Cited By ~ 1

Author(s):

Retief Muller

Keyword(s):

Twentieth Century ◽

Indigenous Knowledge ◽

Significant Role ◽

Dutch Reformed ◽

Reformed Theology ◽

Early Twentieth Century ◽

Biblical Scholar ◽

Christian History

The role of the Dutch Reformed Church’s mission policies in the development of apartheid ideology has in recent times come under increased scrutiny. In terms of the formulation of missionary theory within the DRC, the controversial figure of Johannes du Plessis played a significant role in the early twentieth century. In addition to his work as a mission theorist, Du Plessis was a biblical scholar at Stellenbosch University who was found guilty of heresy by his church body, despite having much support from the rank and file membership. This article asks questions regarding the ways in which his memory and legacy are often evaluated from the twin, yet opposing perspectives of sacralisation and vilification. It also considers the wider intellectual influences on Du Plessis such as the missiology of the German theologian, Gustav Warneck. Du Plessis’s missionary theory helped to lay the groundwork for the later development of apartheid ideology, but perhaps in spite of himself, he also introduced a subverting discourse into Dutch Reformed theology. Some of the incidental consequences of this discourse, particularly in relation to the emerging theme of indigenous knowledge, are furthermore assessed here.

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