Abstract
Abstract. Several works concerning the dynamical and thermal structures and inertial gravity wave activities in the troposphere and lower stratosphere (TLS) from the radiosonde observation have been reported before, but these works were concentrated on either equatorial or polar regions. In this paper, background atmosphere and gravity wave activities in the TLS over Wuhan (30° N, 114° E) (a medium latitudinal region) were statistically studied by using the data from radiosonde observations on a twice daily basis at 08:00 and 20:00 LT in the period between 2000 and 2002. The monthly-averaged temperature and horizontal winds exhibit the essential dynamic and thermal structures of the background atmosphere. For avoiding the extreme values of background winds and temperature in the height range of 11-18km, we studied gravity waves, respectively, in two separate height regions, one is from ground surface to 10km (lower part), and the other is within 18-25km (upper part). In total, 791 and 1165 quasi-monochromatic inertial gravity waves were extracted from our data set for the lower and upper parts, respectively. The gravity wave parameters (intrinsic frequencies, amplitudes, wavelengths, intrinsic phase velocities and wave energies) are calculated and statistically studied. The statistical results revealed that in the lower part, there were 49.4% of gravity waves propagating upward, and the percentage was 76.4% in the upper part. Moreover, the average wave amplitudes and energies are less than those at the lower latitudinal regions, which indicates that the gravity wave parameters have a latitudinal dependence. The correlated temporal evolution of the monthly-averaged wave energies in the lower and upper parts and a subsequent quantitative analysis strongly suggested that at the observation site, dynamical instability (strong wind shear) induced by the tropospheric jet is the main excitation source of inertial gravity waves in the TLS.
Highlights
Gravity waves and their associated momentum transportation and energy propagation are believed to have a significant impact on local tropospheric and lower stratospheric climatology (Alexander and Pfister, 1995; Alexander, 1998)
Many radiosonde observations suggested that the dominant gravity wave disturbances in the troposphere and lower stratosphere (TLS) were inertial gravity waves, usually having a vertical wavelength of several kilometers, horizontal wavelength of several hundreds of kilometers, and a horizontal wind disturbance amplitudes of several ms−1
Restricted by the height coverage of radiosonde observations and the nature of the adopted hodograph analysis method, we can only study the properties of gravity waves with lower frequencies and vertical wavelengths of several kilometers, which was discussed by Alexander (1996)
Summary
Gravity waves and their associated momentum transportation and energy propagation are believed to have a significant impact on local tropospheric and lower stratospheric climatology (Alexander and Pfister, 1995; Alexander, 1998). It is well known that in the middle and upper atmosphere, gravity waves play an important role in determining the global dynamic and thermal structures (Lindzen, 1981; Holton, 1982, 1983; Garcia and Solomon, 1985), and are responsible for local short-term variability of background atmosphere and large-scale atmospheric waves (Fritts and Vincent, 1987). Gravity waves in the middle and upper atmosphere are believed to be excited mainly in the troposphere and lower stratosphere (TLS) and propagate upward (Alexander, 1996), resulting in energy coupling between the lower and upper atmosphere. Many radiosonde observations suggested that the dominant gravity wave disturbances in the TLS were inertial gravity waves, usually having a vertical wavelength of several kilometers, horizontal wavelength of several hundreds of kilometers, and a horizontal wind disturbance amplitudes of several ms−1
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
