Latitudinal and seasonal variations of inertial gravity wave activity in the lower atmosphere over central China

Abstract

[1] Gravity wave activities and background dynamical structure in the troposphere and lower stratosphere (TLS) over five stations at latitudes from 10°N to 40°N were statistically studied by using the data from Radiosonde observation on a twice daily basis at 0800 and 2000 LT. The background dynamical structure exhibits evident latitudinal and seasonal variations and has a profound influence on inertial gravity waves in the TLS. In the analyses of inertial gravity waves, according to the background structures, the observation height coverage is divided into two segments, which are the tropospheric (0-10 km) and lower-stratospheric segments (18-25 km). The observational results indicate that the tropospheric jet is the most important excitation source for gravity waves both in the troposphere and lower stratosphere, and it plays different roles in determining the morphology of gravity waves in these two segments. The jet-excited gravity waves in the troposphere can propagate both upward and downward, and only part of the upward-propagating waves can penetrate into the stratosphere because of the Doppler shifting by the jet, while in the lower stratosphere, gravity waves excited by the tropospheric jet propagate upward. Most differences between the tropospheric and lowerstratospheric results can be explained from the linear dispersion relations of gravity waves and the Doppler shifting by the strong tropospheric jet. However, such an explanation is qualitative rather than quantitative. Generally, the observations reveal that the tropospheric gravity waves are mainly controlled by their excitation sources, implying the wave characteristics may be regarded as (at least an indicator of) the wave excitation source characteristics. These results suggest that in order to attain a more realistic source parameterization for gravity waves propagating in the middle and upper atmosphere, more attention should be paid to the gravity waves in the troposphere. Moreover, the causes of the pronounced peak of lower-stratospheric gravity wave intensity at tropical latitudes revealed by previous observations are also discussed.Citation: Zhang, S. D., and F. Yi (2007), Latitudinal and seasonal variations of inertial gravity wave activity in the lower atmosphere over central China,

WHU VHF radar observations of the diurnal tide and its variability in the lower atmosphere over Chongyang (114.14° E, 29.53° N), China

“…The strongest northward wind occurs at 17.39 km in July, with a maximum value of 8.75 m s −1 , while the strongest southward wind occurs at 11.01 km in January, with a minimum value of −19.77 m s −1 . The characteristics of the background horizontal winds are similar to those revealed by radiosonde observations at middle latitudes (Zhang and Yi, 2007;.…”

Latitudinal and seasonal variations of lower atmospheric inertial gravity wave energy revealed by US radiosonde data

“…Moreover, radiosonde observations usually have wide land coverage and long term accumulation, thus, multistation radiosonde observations should be favorable to reveal the latitudinal variation of GW energy densities. Up to now several multi-station radiosonde observations have been reported (Allen and Vincent, 1995;Wang and Geller, 2003;Wang et al, 2005;Zhang et al, 2006;Zhang and Yi, 2007;Gong et al, 2008). However, some limitations of these previous observations should be noted: 1) Narrow latitude coverage or too few stations were included.…”

“…Wang and Geller (2003) have investigated both E P and E K from 4 years (1998)(1999)(2000)(2001) of US high vertical resolution radiosonde observations over more than 90 stations and found that E T of stratospheric GWs have very large value sin winter in middle latitudes. Recently, Zhang and Yi (2007) analyzed the radiosonde observations from five stations located in latitudes of 20 • N-40 • N and found that although the E P has a maximum value at Haikou station (110 • 12 E, 20 • 12 N), which is in the lowest latitude among these five stations, the E K and E T exhibited maximum value in latitudes about 30 • N due to the strong tropospheric jet, which is thought to be an important GW source. Thus, a question arises: Do the kinetic energy and the total energy in the lower stratosphere really have completely identical latitudinal and seasonal variations as those of the potential energy?…”

Aircraft measurements of gravity waves in the upper troposphere and lower stratosphere during the START08 field experiment

“…Recent studies have demonstrated that satellites such as Microwave Limb Sounder (MLS) and Advanced Microwave Sounding Unit-A (AMSU-A) offer quantitative information of gravity waves in the middle atmosphere (Alexander and Rosenlof, 2003;Wu and Zhang, 2004;Zhang et al, 2013). In addition to satellite measurements, gravity waves are also observed by surface observations (Einaudi et al, 1989;Grivet-Talocia et al, 1999;Koppel et al, 2000), high-resolution radiosonde networks (Vincent and Alexander, 2000;Wang and Geller, 2003;Zhang and Yi, 2007;Gong and Geller, 2010), radars Worthington, 2000, 2007), and super-pressure balloons (Hertzog and Vial, 2001).…”