Intensive radiosonde observations of the diurnal tide and planetary waves in the lower atmosphere over Yichang (111°18' E, 30°42' N), China

Abstract

Abstract. The characteristics of diurnal tide and planetary waves (PWs) in the troposphere and lower stratosphere (TLS) over Yichang (111 • 18 E, 30 • 42 N) were studied by using the data from intensive radiosonde observations in August 2006 (summer month) and January 2007 (winter month) on an eight-times-daily basis. The radiosonde observations of the diurnal tide and PWs in the TLS in the mid-latitudes have seldom been reported. We find that there exists dominant diurnal oscillations in the TLS over Yichang. The observed diurnal tide consists of significant nonmigrating components, which may be owning to the local latent heat release. Since the nonmigrating tides are usually composed of high order modes with smaller vertical wavelengths, which are prone to dissipation in comparison with the low order modes, the observational tidal amplitudes decrease sharply at several heights. Some evident discrepancies between the observations and the GSWM-02 are found, which may result mainly from the inaccurate prediction of the nonmigrating tidal components by the GSWM-02. And, due to the evident seasonal differences of the water vapor mixing ratio disturbance and the tropospheric jet induced turbulence in winter, the diurnal tides in the summer and winter months have some different characteristics. Besides the diurnal tide, obvious quasi 7-day PW (QSDPW) and quasi 10-day PW (QTDPW) are also recognized from our observations in both the summer and winter months. The QSDPWs in the troposphere in both the summer and winter months show a standing wave structure, while the QTDPWs generally exhibit traveling wave characteristics. Spectral analyses reveal that some waves with periods around that of the diurnal tide Correspondence to: S. D. Zhang (zsd@whu.edu.cn) are generated due to the interactions of the diurnal tide and PWs and the tidal amplitudes are modulated by the PWs, indicating the extensive coupling between the diurnal tide and PWs. Moreover, our observations manifest that the PWs can exert great impacts on the tropospheric jet in winter and the tropopause in both the summer and winter months.

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

“…Generally speaking, in the lower stratosphere (above 17 km), the observed wind amplitude profiles agree well with the GSWM-02 but show obvious departure below 9 km, where the observed amplitudes are evidently larger than the GSWM-02 predictions but much closer to the MERRA results. The observed tide displays fairly significant height variations, which has been revealed by previous intensive radiosonde observations (Tsuda et al, 1994a;Huang et al, 2009). In the winter and spring months, there exist remarkable maximums below 8 km in the zonal and meridional winds, which agrees with our previous radiosonde observations at middle latitudes (Huang et al, 2009) and the MERRA results.…”

“…The observed tide displays fairly significant height variations, which has been revealed by previous intensive radiosonde observations (Tsuda et al, 1994a;Huang et al, 2009). In the winter and spring months, there exist remarkable maximums below 8 km in the zonal and meridional winds, which agrees with our previous radiosonde observations at middle latitudes (Huang et al, 2009) and the MERRA results. However, possibly because only 14-day continuous observations in March could not fully reflect the real DT characteristics in this month, the maximum of DT below 8 km in March was absent in our observations but shown in both zonal and meridional winds in MERRA data.…”

“…As suggested by previous investigations (Beard et al, 1997(Beard et al, , 1999(Beard et al, , 2001Mayr et al, 2005aMayr et al, , 2005bHuang et al, 2009Huang et al, , 2012, the coupling between PWs and tides can also lead to tidal variability. For identifying the PW signatures, we detrended the raw time series for each month at each height by subtracting a linear background in time domain and performed a Lomb-Scargle periodogram analysis on the resultant time series.…”

“…As the most widely accepted tidal models, the global-scale wave models (GSWMs) can provide the monthly averaged tides in the height range of 0-124 km and clearly display the latitude and season variability of tides. However, some observational and numerical studies also verify that tides, especially the diurnal tide, also exhibit remarkable local variability, e.g., prominent amplitude peaks in the middle troposphere (Huang et al, 2009), as well as short-term (shorter than 1 month) variability arising from wave-wave interactions (Beard et al, 1999(Beard et al, , 2001Pancheva et al, 2002;Pancheva, 2006). The local and short-term variability of tides can influence not only the local dynamics but also the dynamics in a wider region in both the vertical and horizontal spatial scales by modulating the activity of GWs or interaction with PWs.…”

“…Radiosonde observations can provide horizontal wind and temperature from the ground up to about 30 km , but routine measurements on a twice-daily basis have rarely been used to reveal the characteristics of tides (Wallace and Hartranft, 1969;Wallace and Tadd, 1974). Some intensive radiosonde campaigns (Tsuda, et al, 1994a(Tsuda, et al, , 1994bSeidel et al, 2005;Zhang et al, 2008;Huang et al, 2009) can make a contribution to our understanding of local tides and their variability. However, these intensive observations are generally sparse and there are no long-term continuous intensive observations at all.…”