Atmospheric Sensing Using GNSS RO - GNSS Remote Sensing: Theory, Methods and Applications - page 139

Fig. 6.2 Temperature comparison of radiosonde at Lihue, Hawaii (12UTC, black ) with the near-
coincident COSMIC (LEO#4 RO sounding (11:50UTC, blue ) and NCEP analysis (12UTC, green )
on December 10, 2006. Note the tangent point of the COSMIC RO sounding is about 147 km away
from the radiosonde site

6.3.1 Tropopause and Stratospheric Waves

Starting with GPS/MET, the high accuracy and high vertical resolution temperature
in the upper troposphere and lower stratosphere (UTLS) gained immediate attention
from the broad research community. Figure 6.2 shows the COSMIC RO sounding
is capable of resolving the fine vertical structure temperature variations near the
cold-point tropopause ( 18 km) as seen in the near-coincident radiosonde sounding.
Note the NCEP analysis temperature profile is much smoothed and is likely due to
its lower vertical resolution.
The gravity wave signatures in the RO temperature profiles were soon revealed by
Tsuda et al. ( 2000 ) and Steiner and Kirchengast ( 2000 ). The global map of gravity
waves climatology were successfully developed based on GPS/MET data (Tsuda
et al. 2000 ). Various propagating waves in the stratosphere, including Kelvin waves,
Rossby-gravity waves, as well as waves associated with Quasi-Biennial-Oscillation
were identified (Randel et al. 2003 ; Randel and Wu 2005 ). Schmidt et al. ( 2005 )
further derive a 9-year record of QBO based on the long-term CHAMP and SAC-C
RO soundings.
The global soundings of highly accurate and high vertical resolution RO
temperature observations are ideal for tropopause and related UTLS research (e.g.,
Randel et al. 2003 ; Borsche et al. 2007 ; Schmidt et al. 2006 , 2008 , 2010 ; Steiner
et al. 2009 ). Randel et al. ( 2003 ) firstly demonstrate that the GPS/MET data is