Review comments on “Formation of sodium layer in lower altitudes associated with passage of multiple mesospheric frontal systems” by Narayanan et al. to ACP

Abstract. We present a detailed investigation of the formation of a secondary sodium layer at altitudes of 79–85 km below the main sodium layer based on sodium lidar and airglow imager measurements made at Ramfjordmoen near Tromsø, Norway on the night of 19 December 2014. The airglow imager observations of OH emission revealed four passing frontal systems that resembled mesospheric bores which typically occur in ducting regions of the upper mesosphere. For about 1.5 hours, the lower altitude sodium layer had densities similar to that of the main layer with a peak around 90 km. The lower altitude sodium layer weakened and disappeared soon after the fourth front had passed. The fourth front had weakened in intensity by the time it approached the region of lidar beams and disappeared soon afterwards. The column integrated sodium densities increased gradually during formation of the lower altitude sodium layer. Temperatures measured with the lidar indicate that there was a strong thermal duct structure between 87 and 93 km. Furthermore, the temperature was enhanced below 85 km. Horizontal wind magnitudes estimated from the lidar showed strong wind shears above 93 km. We conclude that the combination of an enhanced stability region due to the temperature profile and intense wind shears have provided ideal conditions for evolution of multiple mesospheric bores revealed as frontal systems in OH images. The downward motion associated with the fronts appeared to have brought air rich in H and O from higher altitudes into the region below 85 km wherein the temperatures were also relatively high. This would have liberated sodium atoms from the reservoir species and suppressed the re-conversion of atomic sodium into reservoir species so that the lower altitude sodium layer could form and the column abundance could increase. The presented observations also reveal the importance of mesospheric frontal systems in bringing about significant variation of minor species over shorter temporal intervals.

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Formation of an additional density peak in the bottom side of the sodium layer associated with the passage of multiple mesospheric frontal systems

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-2343-2021 ◽

2021 ◽

Vol 21 (4) ◽

pp. 2343-2361

Author(s):

Viswanathan Lakshmi Narayanan ◽

Satonori Nozawa ◽

Shin-Ichiro Oyama ◽

Ingrid Mann ◽

Kazuo Shiokawa ◽

...

Keyword(s):

Horizontal Wind ◽

Main Peak ◽

Strong Wind ◽

Density Peak ◽

Lower Altitude ◽

Sodium Layer ◽

Reservoir Species ◽

Temporal Intervals ◽

Frontal Systems ◽

Wind Shears

Abstract. We present a detailed investigation of the formation of an additional sodium density peak at altitudes of 79–85 km below the main peak of the sodium layer based on sodium lidar and airglow imager measurements made at Ramfjordmoen near Tromsø, Norway, on the night of 19 December 2014. The airglow imager observations of OH emissions revealed four passing frontal systems that resembled mesospheric bores, which typically occur in ducting regions of the upper mesosphere. For about 1.5 h, the lower-altitude sodium peak had densities similar to that of the main peak of the layer around 90 km. The lower-altitude sodium peak weakened and disappeared soon after the fourth front had passed. The fourth front had weakened in intensity by the time it approached the region of lidar beams and disappeared soon afterwards. The column-integrated sodium densities increased gradually during the formation of the lower-altitude sodium peak. Temperatures measured with the lidar indicate that there was a strong thermal duct structure between 87 and 93 km. Furthermore, the temperature was enhanced below 85 km. Horizontal wind magnitudes estimated from the lidar showed strong wind shears above 93 km. We conclude that the combination of an enhanced stability region due to the temperature profile and intense wind shears have provided ideal conditions for evolution of multiple mesospheric bores revealed as frontal systems in the OH images. The downward motion associated with the fronts appeared to have brought air rich in H and O from higher altitudes into the region below 85 km, wherein the temperature was also higher. Both factors would have liberated sodium atoms from the reservoir species and suppressed the reconversion of atomic sodium into reservoir species so that the lower-altitude sodium peak could form and the column abundance could increase. The presented observations also reveal the importance of mesospheric frontal systems in bringing about significant variation of minor species over shorter temporal intervals.

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Mesospheric fronts in airglow images and the variation of the bottomside sodium layer densities measured by a sodium lidar at Tromsø, Norway

10.5194/egusphere-egu2020-5218 ◽

2020 ◽

Author(s):

Viswanathan Lakshmi Narayanan ◽

Satonori Nozawa ◽

Ingrid Mann ◽

Shin-ichiro Oyama ◽

Kazuo Shiokawa ◽

...

Keyword(s):

Signal Strength ◽

Pass Band ◽

Wave Dynamics ◽

Sodium Layer ◽

Lidar Measurements ◽

Intensity Changes ◽

Frontal Systems ◽

The Relationship ◽

Airglow Intensity ◽

Frontal Boundary

Mesospheric frontal systems are waves extending to hundreds of kilometers along their phase fronts and appear like a boundary. They are observed in the upper mesospheric airglow imaging observations of OH, sodium and OI greenline nightglow emissions. It is believed that the fronts result from gravity wave dynamics associated with favorable background conditions like thermal ducting. Many of the frontal systems are identified as mesospheric bores when they are accompanied with sudden airglow intensity changes across the frontal boundary. Most of the frontal systems propagate with phase locked undulations following the leading front, while some induce turbulence behind the front. Though the existence of the frontal systems in the mesosphere is known for more than two decades, their role and importance is not understood properly. In this work, we use airglow data from an all-sky imager located at Troms&#248; to identify the frontal systems, particularly using OH images. Collocated five-beam sodium lidar measurements are used to identify the structuring in sodium densities around time of passage of the frontal systems. The sodium lidar at Troms&#248; is a versatile system capable of measuring sodium densities, temperatures and winds in the upper mesospshere region. Hence, we obtain the wind and temperature information to study the background conditions during passage of the intense frontal systems. Though, mostly we focus on OH airglow images as they are observed with broad pass band resulting in higher signal strength, we also utilize images from other emissions like OI greenline and sodium whenever they are available and free from auroral features. Interestingly, we find formation of some unusual structuring in the bottomside sodium layer around the passage of the frontal systems. We show different cases during winter months of the years 2013-14 and 2014-15 and investigate the relationship between unusual bottomside structuring in the sodium layer and passage of the frontal systems.

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Daytime observation of the sodium layer with a Fabry-Perot spectrometer at Mawson, Antarctica

Geophysical Research Letters ◽

10.1029/gl016i008p00871 ◽

1989 ◽

Vol 16 (8) ◽

pp. 871-874 ◽

Cited By ~ 9

Author(s):

P. Greet ◽

M. Conde ◽

F. Jacka

Keyword(s):

Sodium Layer ◽

Fabry Perot

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Factor Analysis of the Frontal Systems Behavior Scale (FrSBe)

Assessment ◽

10.1177/1073191102250339 ◽

2003 ◽

Vol 10 (1) ◽

pp. 79-85 ◽

Cited By ~ 120

Author(s):

Julie C. Stout ◽

Rebecca E. Ready ◽

Janet Grace ◽

Paul F. Malloy ◽

Jane S. Paulsen

Keyword(s):

Factor Analysis ◽

Factor Structure ◽

Rating Scale ◽

Executive Dysfunction ◽

Behavior Rating Scale ◽

Neurological Patients ◽

Frontal Systems ◽

Behavior Scale ◽

Behavior Disturbances ◽

Modest Level

The Frontal Systems Behavior Scale (FrSBe), formerly called the Frontal Lobe Personality Scale (FLOPS), is a brief behavior rating scale with demonstrated validity for the assessment of behavior disturbances associated with damage to the frontal-subcortical brain circuits. The authors report an exploratory principal factor analysis of the FrSBe–Family Version in a sample including 324 neurological patients and research participants, of which about 63% were diagnosed with neurodegenerative diseases (Huntington's, Parkinson's, and Alzheimer's diseases). The three-factor solution accounted for a modest level of variance (41%) and confirmed a factor structure consistent with the three subscales proposed on the theoretical basis of the frontal systems. Most items (83%) from the FrSBe subscales of Apathy, Disinhibition, and Executive Dysfunction loaded saliently on three corresponding factors. The FrSBe factor structure supports its utility for assessing both the severity of the three frontal syndromes in aggregate and separately.

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The bistatic LGS scheme for sodium layer height characterization (based on the Teide Observatory experimental setup)

10.1117/12.787809 ◽

2008 ◽

Cited By ~ 1

Author(s):

Julio A. Castro-Almazán ◽

Jesús J. Fuensalida ◽

Ángel Alonso ◽

Sergio Chueca

Keyword(s):

Experimental Setup ◽

Layer Height ◽

Sodium Layer

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Oligocene sea-surface temperature gradients in the Southern Ocean related to Tasmanian Gateway widening: New TEX86 paleothermometry, dinoflagellate cyst data and climate model comparisons

10.5194/egusphere-egu21-11103 ◽

2021 ◽

Author(s):

Frida Hoem ◽

Suning Hou ◽

Matthew Huber ◽

Francesca Sangiorgi ◽

Henk Brinkhuis ◽

...

Keyword(s):

Southern Ocean ◽

Surface Temperature ◽

Sea Surface Temperature ◽

Climate Model ◽

Temperature Gradients ◽

Ocean Currents ◽

Sea Surface ◽

Dinoflagellate Cyst ◽

Frontal Systems ◽

Dsdp Site

The opening of the Tasmanian Gateway during the Eocene and further deepening in the Oligocene is hypothesized to have reorganized ocean currents, preconditioning the Antarctic Circumpolar Current (ACC) to evolve into place. However, fundamental questions still remain on the past Southern Ocean structure. We here present reconstructions of latitudinal temperature gradients and the position of ocean frontal systems in the Australian sector of the Southern Ocean during the Oligocene. We generated new sea surface temperature (SST) and dinoflagellate cyst data from the West Tasman margin, ODP Site 1168. We compare these with other records around the Tasmanian Gateway, and with climate model simulations to analyze the paleoceanographic evolution during the Oligocene. The novel organic biomarker TEX86- SSTs from ODP Site 1168, range between 19.6 &#8211; 27.9&#176;C (&#177; 5.2&#176;C, using the linear calibration by Kim et al., 2010), supported by temperate and open ocean dinoflagellate cyst assemblages. The data compilation, including existing TEX86-based SSTs from ODP Site 1172 in the Southwest Pacific Ocean, DSDP Site 274 offshore Cape Adare, DSDP Site 269 and IODP Site U1356 offshore the Wilkes Land Margin and terrestrial temperature proxy records from the Cape Roberts Project (CRP) on the Ross Sea continental shelf, show synchronous variability in temperature&#160;evolution between&#160;Antarctic and&#160;Australian sectors of the Southern Ocean. The SST gradients are around 10&#176;C latitudinally across the Tasmanian Gateway throughout the early Oligocene, and increasing in the Late Oligocene. This increase can be explained by polar amplification/cooling, tectonic drift, strengthening of atmospheric currents and ocean currents. We suggest that the progressive cooling of Antarctica and the absence of mid-latitude cooling strengthened the westerly winds, which in turn could drive an intensification of the ACC and strengthening of Southern Ocean frontal systems.

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On the nature of rainfall intermittency as revealed by different metrics and sampling approaches

Hydrology and Earth System Sciences ◽

10.5194/hess-17-355-2013 ◽

2013 ◽

Vol 17 (1) ◽

pp. 355-369 ◽

Cited By ~ 37

Author(s):

G. Mascaro ◽

R. Deidda ◽

M. Hellies

Keyword(s):

Scale Invariance ◽

Weather Forecasting ◽

Rainfall Variability ◽

Analysis Tool ◽

Systematic Analysis ◽

Local Climate ◽

Rainfall Occurrence ◽

Frontal Systems ◽

Intensity Fluctuations ◽

The Time Domain

Abstract. A general consensus on the concept of rainfall intermittency has not yet been reached, and intermittency is often attributed to different aspects of rainfall variability, including the fragmentation of the rainfall support (i.e., the alternation of wet and dry intervals) and the strength of intensity fluctuations and bursts. To explore these different aspects, a systematic analysis of rainfall intermittency properties in the time domain is presented using high-resolution (1-min) data recorded by a network of 201 tipping-bucket gauges covering the entire island of Sardinia (Italy). Four techniques, including spectral and scale invariance analysis, and computation of clustering and intermittency exponents, are applied to quantify the contribution of the alternation of dry and wet intervals (i.e., the rainfall support fragmentation), and the fluctuations of intensity amplitudes, to the overall intermittency of the rainfall process. The presence of three ranges of scaling regimes between 1 min to ~ 45 days is first demonstrated. In accordance with past studies, these regimes can be associated with a range dominated by single storms, a regime typical of frontal systems, and a transition zone. The positions of the breaking points separating these regimes change with the applied technique, suggesting that different tools explain different aspects of rainfall variability. Results indicate that the intermittency properties of rainfall support are fairly similar across the island, while metrics related to rainfall intensity fluctuations are characterized by significant spatial variability, implying that the local climate has a significant effect on the amplitude of rainfall fluctuations and minimal influence on the process of rainfall occurrence. In addition, for each analysis tool, evidence is shown of spatial patterns of the scaling exponents computed in the range of frontal systems. These patterns resemble the main pluviometric regimes observed on the island and, thus, can be associated with the corresponding synoptic circulation patterns. Last but not least, we demonstrate how the methodology adopted to sample the rainfall signal from the records of the tipping instants can significantly affect the intermittency analysis, especially at smaller scales. The multifractal scale invariance analysis is the only tool that is insensitive to the sampling approach. Results of this work may be useful to improve the calibration of stochastic algorithms used to downscale coarse rainfall predictions of climate and weather forecasting models, as well as the parameterization of intensity-duration-frequency curves, adopted for land planning and design of civil infrastructures.

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