Abstract. As a result of partial specular reflection from the atmospheric stable
layer, the radar tropopause (RT) can simply and directly be detected by VHF
radars with vertical incidence. Here, the Beijing mesosphere–stratosphere–troposphere (MST) radar measurements are
used to investigate the structure and the variabilities in the tropopause in
Xianghe, China, with a temporal resolution of 0.5 h from November 2011 to
May 2017. The high-resolution radar-derived tropopause is compared with the
thermal lapse-rate tropopause (LRT) that is defined by the World Meteorological
Organization (WMO) criterion from twice-daily radiosonde soundings and with
the dynamical potential vorticity tropopause (PVT) that is defined as the
height of the 2 PVU (PVU – potential vorticity units; 1 PVU = 106 m2 s−1 K kg−1) surface. We only consider tropopauses below 16 km in this
study because of limitations with the radar system. During all the seasons,
the RT and the LRT in altitude agree well with each other, with a correlation
coefficient of ≥0.74. Statistically, weaker (higher)
tropopause sharpness seems to contribute to larger (smaller) difference
between the RT and the LRT in altitude. The RT agrees well with the PVT in
altitude during winter and spring, with a correlation coefficient of
≥0.72, while the correlation coefficient in summer is only
0.33. As expected, the monthly mean RT and LRT height both show seasonal
variations. Lomb–Scargle periodograms show that the tropopause exhibits
obvious diurnal variation throughout the seasons, whereas the semidiurnal
oscillations are rare and are occasionally observed during summer and later
spring. Our study shows the potential of the Beijing MST radar to determine
the tropopause height as well as present its diurnal oscillations.
Internal Gravity Waves and Meso/Submesoscale Currents in the Ocean: Anticipating High-Resolution Observations from the SWOT Swath Altimeter Mission