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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 36, issue 5 | Copyright
Ann. Geophys., 36, 1403-1417, 2018
https://doi.org/10.5194/angeo-36-1403-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Regular paper 19 Oct 2018

Regular paper | 19 Oct 2018

Strong downdrafts preceding rapid tropopause ascent and their potential to identify cross-tropopause stratospheric intrusions

Feilong Chen1, Gang Chen1, Chunhua Shi2, Yufang Tian3, Shaodong Zhang1, and Kaiming Huang1 Feilong Chen et al.
  • 1School of Electronic Information, Wuhan University, Wuhan 430072, China
  • 2Key Laboratory of Meteorological Disaster, Ministry of Education, Nanjing University of Information Science &Technology, Nanjing 210044, China
  • 3Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China

Abstract. The capability of measuring three-dimensional wind and tropopause structure with relatively high time and vertical resolution makes very-high-frequency (VHF) radars a potentially important tool for studying various processes of the atmosphere. However, at present several unanswered questions remain regarding the use of VHF radars to identify possible stratospheric intrusions. Here the potential detection of stratospheric intrusion events is discussed using the Beijing MST (mesosphere–stratosphere–troposphere) radar located at Xianghe (39.75°N, 116.96°E). During the passage of a cutoff low in late November 2014, a deep V-shaped tropopause structure and strong downdrafts (>0.8ms−1) immediately preceding the rapid tropopause ascent (>0.2kmh−1) were observed. Within the height region of the downdrafts, the stability of the radar tropopause seems to be weakened. Analysis results from global reanalysis and the satellite data, as well as the trajectory model, have shown clear evidence of downward stratospheric intrusions (dry ozone-rich and depleted methane air) associated with the strong downdrafts. A total of 20 typical cases of such strong downdrafts, occurring during various synoptic processes in different seasons, have been presented, and 15 of them are exactly associated with some form of stratospheric intrusions. Four years (2012–2015) of such downdrafts are further discussed. The observations reveal that the strong downdrafts preceding the rapid tropopause ascent can be a valuable diagnostic for monitoring intrusion events, which helps us to gain a better understanding of stratospheric intrusions in VHF radar observations.

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Downward stratospheric intrusions are well known as an important source of tropospheric ozone. In the light of the present understanding, several unanswered questions remain regarding the use of VHF radars to identify stratospheric intrusions. Our study found that the radar-observed strong downdrafts preceding the rapid tropopause ascent are a strong diagnostic for possible intrusions. This will have important implications for air-quality monitoring and long-term estimation of troposphere ozone.
Downward stratospheric intrusions are well known as an important source of tropospheric ozone....
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