Seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical station
Long-term VHF radar (53 MHz with 3° beam-width) observations at Gadanki (13.5° N, 79.2° E), India, during the period from September 1995 to August 1999 are used to study monthly, seasonal and annual medians of vertical eddy diffusivity, <i>K</i> in the troposphere, lower stratosp...
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doaj-c18b3b061928416cb429e0b35b358d6a2020-11-25T00:20:19ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762001-08-011997598410.5194/angeo-19-975-2001Seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical stationD. Narayana Rao0M. V. Ratnam1T. N. Rao2S. V. B. Rao3Department of Physics, Sri Venkateswara University, Tirupati 517 502, IndiaDepartment of Physics, Sri Venkateswara University, Tirupati 517 502, IndiaDepartment of Physics, Sri Venkateswara University, Tirupati 517 502, IndiaDepartment of Physics, Sri Venkateswara University, Tirupati 517 502, IndiaLong-term VHF radar (53 MHz with 3° beam-width) observations at Gadanki (13.5° N, 79.2° E), India, during the period from September 1995 to August 1999 are used to study monthly, seasonal and annual medians of vertical eddy diffusivity, <i>K</i> in the troposphere, lower stratosphere and mesosphere. First, the spectral width contribution due to non-turbulent effects has been removed for further analysis and the monthly, seasonal medians of <i>K</i> are calculated. The monthly median of <i>K</i> in the troposphere shows maximum and minimum in June-July and November-December, respectively. In general, large values of <i>K</i> are seen up to 10 km and then decrease with height. Larger values of <i>K</i> are observed during monsoon and post-monsoon than in winter and summer. In general, the maximum and minimum values of the annual median of <i>K</i> (in logarithmic values) in the troposphere are found to be 0.25 and - 1.3 m<sup>2</sup> s<sup>-1</sup> respectively. In the mesosphere, the monthly median of <i>K</i> shows maximum and minimum during June-July and November-December, respectively, similar to the lower atmosphere. The value of <i>K</i> in the mesosphere becomes larger and it increases with height up to 75 km and again decreases above that height. The maximum values are seen during the summer, followed by equinoxes and a minimum during the winter. In general, the maximum and minimum values of <i>K</i> (in logarithmic values) are found to be 0.7 and 0.3 m<sup>2</sup> s<sup>-1</sup>, respectively, in the mesosphere. A comparison of Doppler spectral parameters in different beam directions shows anisotropy in both signal-to- noise ratio (SNR) and spectral widths in the mesosphere, whereas it shows isotropy in SNR and anisotropy in the spectral widths in troposphere and lower stratosphere.<br><br><b>Key words. </b>Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence; waves and tides)https://www.ann-geophys.net/19/975/2001/angeo-19-975-2001.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
D. Narayana Rao M. V. Ratnam T. N. Rao S. V. B. Rao |
spellingShingle |
D. Narayana Rao M. V. Ratnam T. N. Rao S. V. B. Rao Seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical station Annales Geophysicae |
author_facet |
D. Narayana Rao M. V. Ratnam T. N. Rao S. V. B. Rao |
author_sort |
D. Narayana Rao |
title |
Seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical station |
title_short |
Seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical station |
title_full |
Seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical station |
title_fullStr |
Seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical station |
title_full_unstemmed |
Seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical station |
title_sort |
seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical station |
publisher |
Copernicus Publications |
series |
Annales Geophysicae |
issn |
0992-7689 1432-0576 |
publishDate |
2001-08-01 |
description |
Long-term VHF radar (53
MHz with 3° beam-width) observations at Gadanki (13.5° N, 79.2° E), India,
during the period from September 1995 to August 1999 are used to study monthly,
seasonal and annual medians of vertical eddy diffusivity, <i>K</i> in the
troposphere, lower stratosphere and mesosphere. First, the spectral width
contribution due to non-turbulent effects has been removed for further analysis
and the monthly, seasonal medians of <i>K</i> are calculated. The monthly
median of <i>K</i> in the troposphere shows maximum and minimum in June-July
and November-December, respectively. In general, large values of <i>K</i> are
seen up to 10 km and then decrease with height. Larger values of <i>K</i> are
observed during monsoon and post-monsoon than in winter and summer. In general,
the maximum and minimum values of the annual median of <i>K</i> (in logarithmic
values) in the troposphere are found to be 0.25 and - 1.3 m<sup>2</sup> s<sup>-1</sup>
respectively. In the mesosphere, the monthly median of <i>K</i> shows maximum
and minimum during June-July and November-December, respectively, similar to
the lower atmosphere. The value of <i>K</i> in the mesosphere becomes larger
and it increases with height up to 75 km and again decreases above that height.
The maximum values are seen during the summer, followed by equinoxes and a
minimum during the winter. In general, the maximum and minimum values of <i>K</i>
(in logarithmic values) are found to be 0.7 and 0.3 m<sup>2</sup> s<sup>-1</sup>,
respectively, in the mesosphere. A comparison of Doppler spectral parameters in
different beam directions shows anisotropy in both signal-to- noise ratio (SNR)
and spectral widths in the mesosphere, whereas it shows isotropy in SNR and
anisotropy in the spectral widths in troposphere and lower stratosphere.<br><br><b>Key words. </b>Meteorology and
atmospheric dynamics (middle atmosphere dynamics; turbulence; waves and tides) |
url |
https://www.ann-geophys.net/19/975/2001/angeo-19-975-2001.pdf |
work_keys_str_mv |
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