TITLE:
Wind Motions around the Tropical Cirrus Using Simultaneous Radar and Lidar Observations over Gadanki (13.45°N, 79.18°E), India
AUTHORS:
C. Dhananjaya Rao, M. Arunachalam Srinivasan, M. Krishnaiah, Y. Bhavani Kumar, S. V. B. Rao
KEYWORDS:
Cirrus Cloud, LDR, Winds, TEJ, Lidar, Radar
JOURNAL NAME:
International Journal of Geosciences,
Vol.5 No.11,
October
13,
2014
ABSTRACT: The
present study describes variation of peak linear depolarization ratio (LDR)
with wind around the cloud altitude using simultaneous observation of winds and
cirrus cloud for the first time using Indian MST radar and polarization lidar
co-located over a low latitude station Gadanki (13.7°N and 79.2°E). Three
different cases of passage of the cirrus at different altitudes are noticed,
one during a North-East monsoon day and other two during South-West monsoon days.
The zonal wind below the cloud height has shown similar variation with LDR
during 02 November 2006 and the meridional wind within the cloud height during
25 July 2007 and 08 June 2006 has shown opposite variation with LDR. Even
though there is a significant increase in zonal wind due to the existence of
tropical easterly jet (TEJ) above cloud height during 25 July 2007 and 08 June
2006, also, the vertical wind is found to be continuously varying during 25
July 2007 and it is upward dominant in the initial stage and is mostly downward
in the later stage of observation on 08 June 2006, there is a slight descent in
cloud altitude only during 25 July 2007. Thus, the wind above the cloud height
alone may not affect the ascent/descent of the cloud top altitude. The
potential temperature gradient is high within the cloud heights when the cirrus
present near the cold point tropopause indicates the maximum air-mass mixing
near the tropopause.