Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： The nightly and seasonal variability of gravity wave activity and spectra in the mesopause over Beijing are studied with 3 years of sodium lidar observations. From the linear layer density response to gravity wave forcing, the lidar data were analyzed to get the atmospheric density perturbations and their spectra. The atmospheric density perturbation, density variance for fluctuations with vertical scales between 2 and 10 km, and amplitudes of density perturbation spectra at m = 2pi/8, 2pi/4, m = 2pi/1.5, m = 2pi/1,and omega = 2pi/60,omega = 2pi/40,2pi/25 all exhibit large nightly variability as well as large seasonal variations, with the semiannual maxima occurring near the solstice. The mean RMS atmospheric density perturbation over Beijing are 5.8%, which are obviously larger in summer than that in winter and the maxima occur near the solstice. The m spectra show power law shapes, and their range of variation is between -1.97 and -3.67 with an annual mean value of -3.02, and omega spectra is between -1.06 and -2.08 with an annual mean value of -1.92, respectively. It is concluded that the reaction of the Qinghai-Tibet Plateau and the background wind may be the main reason of the gravity wave behaviors at Beijing.
Peer Review Status:
Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： Sodium lidar observations of Sporadic Sodium Layers (SSL) in 2010 at a low-latitude location (Haikou, China, 20.0癗, 110.3癊) are reported in this paper. The wavelength of the dye laser is set to 589 nm by a sodium fluorescence cell. The energy and divergence of the beam are about 45 mJ and 1mrad,respectively. The repetition rate of Nd:YAG laser is 30 Hz. The backscattered fluorescence photons from the sodium layer are collected by a telescope with a 1000 mm diameter primary mirror. From 38 SSLs events detected in about 458 h of observation, an SSL occurrence rate of 1 event every 12 h at our location was obtained. This result, combined with previous studies at a mid-latitude location (Wuhan, China, 31癗, 114癊), and compared with the SSLs at a low-latitude location (Brazil, 23癝, 46癢), reveals that the SSL occurrence can be frequent at a low-latitude location of Haikou, China. The profiles of a peak density of the SSL were very spatial symmetry on Dec. 30, 2010. With respect to the correlation with sporadic E, the ionosphere data obtained by an ionosonde operated at Danzhou, China (19.5癗, 109.1癊), about 160km southwest of Haikou lidar station, have been examined. By statistical analysis of 13 events, when simultaneous SSL data and ionograms are available, a considerable correlation was found between sporadic E layers and the SSLs. The sporadic sodium layers have average downward vertical velocities at Haikou, China.
Peer Review Status:Awaiting Review
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