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Measurements of vertical eddy diffusivity across the tropopause using radio acoustic sounding system (RASS)
Author(s) -
Alexander S. P.,
Tsuda T.
Publication year - 2007
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2006gl028753
Subject(s) - tropopause , radiosonde , stratosphere , troposphere , depth sounding , eddy diffusion , atmospheric sciences , radar , environmental science , mesosphere , meteorology , geology , turbulence , physics , telecommunications , computer science , oceanography
A four day high temporal resolution MU radar RASS data set was obtained under light wind conditions in August 1995, enabling retrieval of virtual temperatures up to 20 km. This provided a unique opportunity to study the vertical eddy diffusivity K across the tropopause using RASS Brunt‐Väisälä frequency N and radar spectral width. Co‐located six hourly radiosondes enabled calculation of K using radiosonde N and radar spectral width. RASS K decreased across the WMO tropopause, from (0.39 ± 0.05) m 2 s −1 in the uppermost kilometre of the troposphere to (0.27 ± 0.03) m 2 s −1 in the lowermost kilometre of the stratosphere. The equivalent radiosonde K were (0.43 ± 0.06) m 2 s −1 and (0.31 ± 0.07) m 2 s −1 respectively. The WMO tropopause seems to provide a better definition than the cold‐point tropopause in separating the stratosphere from the troposphere when considering the mixing of minor constituents.