scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Global distribution and seasonal variations of convective instabilities occurring in the
mesosphere
Viswanathan Lakshmi Narayanan 1 , Subramanian Gurubaran 1 , James M Russell III 2
1 Equatorial Geophysical Research Laboratory, Indian Institute of Geomagnetism, 2 Center for
Atmospheric Sciences, Hampton University
Convective instabilities are important short scale features occurring during the cascade of
energy from larger to smaller scales. Their presence is inferred in the Mesosphere Lower
Thermosphere region with the help of rocket soundings, lidar observations and optical
imaging techniques. Such observations provide information about convective instabilities
only over a few selected locations. Their global distribution, seasonal variations, occurrence
frequency and maximum occurrence altitudes are not well known. In this study, we have
utilized SABER\TIMED temperature measurements for the years 2003 and 2008
(corresponding to solar maximum and minimum respectively) to infer the occurrence
frequency, global distribution, day night, seasonal, solar cycle variations and any local time
dependence of convective instabilities occurring in the mesosphere. The occurrences of
convective instabilities are more or less equal during day and night time. It is found that the
occurrence of convective instabilities peak at 94 to 96 km altitudes with presence of
instabilities for about 16% of observation time. In summer high latitude mesosphere, the peak
occurrence decreases to a height of 80 to 81 km. Winter and equinoctical periods show more
or less similar pattern. Overall occurrence is high at low latitudes followed by mid latitudes
and high latitudes. No significant longitudinal differences are seen in the occurrence of such
instabilities. No definitely attributable solar cycle dependence is deduced from this study.