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STP12 Abstracts Berlin, 12 - 16 July 2010 SCOSTEP Symposium 2010 Study of Mesospheric Temperature Inversions and their Generation Mechanisms using Rayleigh Lidar and Satellite observations over a Sub-tropical Location Sharma Som Kumar , Chandra H. , Lal S. , Acharya Y. B. Physical Research Laboratory Characteristics of Mesospheric Temperature Inversions (MTIs) have been studied using more than 250 nights of Rayleigh Lidar data collected at Gurushikhar, Mt. Abu (24.5 o N, 72.7 o E, msl 1.7 km) from 1997 to 2003. Strong MTI event on 30 December 2003 and two episodes of mesospheric temperature inversion during December and March 2000 are described along with a detailed statistical analysis of MTI characteristics. Case studies revealed that MTI persists for few days and its amplitude increases gradually. Both the episodes exhibit different characteristics viz., height of occurrence, magnitude of inversion and the separation between upper and lower levels of MTIs. Mesospheric zonal winds observed by TIMED Doppler Interferometer (TIDI), onboard Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED), were also found to be strongly perturbed on 30 December 2003 over Mt. Abu. Ozone, observed by Halogen Occultation Experiment (HALOE) onboard Upper Atmospheric Research Satellite (UARS), shows significantly higher variability during strong MTIs. Statistical study revealed that the frequency of occurrence of MTIs is maximum during winter months and minimum during summer. These features are in contrast to the low-latitude observations. The average magnitude of MTI is about more than 20 K and has prominent seasonal variability and the average height of occurrence of MTIs has been found to be lower over Mt. Abu than that observed over low-latitudes. Furthermore, using NCEP wind data, we have found a good correlation between occurrence of MTI events and strong wave activity in the troposphere over Mt. Abu. These observed features are discussed in terms of possible source mechanisms and impact on mesospheric processes.
STP12 Abstracts Berlin, 12 - 16 July 2010 SCOSTEP Symposium 2010 Middle Atmospheric Gravity Wave Activity over a Sub-tropical Location, Mt. Abu (24.5oN, 72.7oE): Implication on Coupling Processes Sharma Som Kumar 1 , Chandra H. 1 , Lal S. 1 , Acharya Y. B. 1 Physical Research Laboratory, 2 Gravity Waves (GWs) play an important role in energy and momentum transport from troposphere to the upper atmosphere. Strong convective activity over tropical and sub-tropical regions plays an important role for the generation of GWs. Mt. Abu (24.5°N, 72.7°E) is located in sub-tropical, hilly region where a large number of convective phenomena occur. GWs study at Mt. Abu may contribute to a better understanding of middle atmosphere on seasonal and long term scales and in delineating vertical coupling between lower, middle and upper atmosphere. Rayleigh lidar is in operation at Mt. Abu since 1997. We make use of ~11 years (1997-2008) of high resolution Rayleigh lidar measurements for the present study. Temperature profiles are derived from raw data (photon count profiles) in the height range of 30-65 km with a vertical resolution of ~480 m. Temperature profiles are further analyzed to extract and delineate the GWs features. The present study is focused on the GWs characteristics in terms of time (frequency) and height (wave-number), associated Potential Energy (P.E.) and their seasonal dependences. The frequency and wave-number spectra are obtained, where continuous data sets of ~4 hours are available. Generally, the temporal evolution of temperature profile illustrates the downward phase propagation indicating that the energy is propagating upward. The dominant time period of GW is found to be greater than 2.3 hours in the mesosphere at the 60-65 km height region. The lower periodicity of less than ~2 hours are found in the upper stratosphere (30-45 km). The P.E. for 3 different height regions (35-40 km, 45-50 km and 55-60 km) are calculated and analyzed. The seasonal variation of GWs characteristics and associated P.E. has also been investigated. It shows two distinguished maxima during May and November months. Further, the obtained results are compared with models and the other reported results from different locations.
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scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

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