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STP12 Abstracts Berlin, 12 - 16 July 2010 SCOSTEP Symposium 2010 VHF radar observed characteristics of convectively generated gravity waves during wet and dry spells of Indian summer monsoon Uma K. N 1 , Karanam Kishore Kumar 2 , Rao T. Narayana 3 1 Space Physics Laboratory, Trivandrum, India, 2 Space Physics Laboratory, Trivandrum, India, 3 National Atmospheric Research Laboratory, Tirupati, India A powerful VHF radar observed characteristics of convectively generated gravity waves (CGW) excited during the wet and dry spells of Indian summer monsoon over a tropical station Gadanki (13.5 0 N, 79.2 0 E) are discussed. The characteristics of gravity waves in the lower stratosphere during these two spells are discussed in terms their wavelet spectra along with height-time sections of vertical velocities. In most of the cases, the lower stratospheric gravity wave amplitudes were found to be relatively more in dry spell compared to wet spell. The wavelet analysis of lower stratospheric vertical velocities showed a dominant periodicity of about ~20- 40 min in wet spell and ~15-20 min in dry spell. The analyses also showed clearly that wet spell is found to be more conducive for the generation of gravity waves. However, the propagation of these waves to the stratosphere is found to be more efficient during dry spell of monsoon. The strengthening/weakening of the tropical easterly jet during wet/dry spell of monsoon is found to be the main reason for the inhibited/enhanced wave activity in the lower stratosphere during wet/dry spell. The present analysis also suggests that the static stability of the mid and upper troposphere during dry and wet spell have implications in the observed frequency of the CGW. Thus, the present analyses brought out for the first time the features of CGW during two distinctive regimes of convective systems and emphasized the importance of prevailing background conditions in exciting them.
STP12 Abstracts Berlin, 12 - 16 July 2010 SCOSTEP Symposium 2010 Study of Greenline Dayglow Emission Upadhayaya Arun The study deals with the reanalysis of morphological (volume emission rate as a function of altitude and latitude) study of greenline dayglow emission under equinox conditions in light of Solar 2000 V2.25 model. The morphology is obtained from the emission profiles of greenline dayglow emission using the updated glow model. The glow model is updated by incorporating temperature dependent rate coefficient of the reaction N2(A 3 ∑u + ) +O. The proposed correction for the atomic oxygen density in MSIS-90 neutral atmosphere model is also included at mesospheric altitudes to achieve the consistency with the WINDII measurements. The modeled morphology of greenline dayglow emission is presented between 50˚S and 50˚N latitudes for the months of March and April using Solar 2000 V2.25 model. It has been found that this emission shows less asymmetry between the northern and the southern hemispheres in comparison to previous study which was carried out using Hinteregger Solar EUV flux model. The Glow model is further updated to study the influence of geomagnetic activity on this emission and it has been simulated and influence of the activity is clearly seen on thermospheric peak intensity. The intensity of greenline thermospheric peak can hence be considered as a potential candidate for thermospheric proxy.
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scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

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