Downward Propagating Equatorial Kelvin Wave over the Eastern Indian Ocean as Revealed from Radiosonde and GPS Radio Occultation (CHAMP) Data
Abstract: Vertical propagation
of equatorial Kelvin wave and its correlation with convective activity over the
eastern Indian Ocean were investigated through analyses and inter-comparisons
of radiosonde and GPS/CHAMP occultation data. The radiosonde data from 80
balloon launchings were obtained in the period of August 5 to 14, 2005 over the
region of 1.640 N – 6.20 S, 88.20 E– 97.340 E surrounding the cruise track of
R/V Mirai during Tropical Ocean and Climate Study (TOCS) campaigned. Results of
radiosonde data analyses show a variation in the height of cold point tropopause
(CPT) associated with Kelvin wave
activities. In addition, coexisting
strong convective activities were also detected during August 9 to 11,
2005. The characteristics of equatorial
Kelvin wave were further investigated by fitting a sinusoidal approximation by
assuming zonal wave number 1 and 2 to the GPS/CHAMP temperature perturbations
using non linear inversion algorithm. It is found that the periodicity of
observed Kelvin wave is about 5 – 6 days. Inter-comparisons of low-pass
filtered of height-time cross section of perturbation temperature from both
radiosonde and GPS/CHAMP data showed downward propagation Kelvin wave, which
was more pronounced during August 11 to 14, 2005. Furthermore, an increase in
the potential and kinetic energy of the downward propagating Kelvin wave was
observed prior to the occurrence of strong convection, which is believed as convectively
coupled equatorial Kelvin wave.
Keywords: Radiosonde,
GPS/CHAMP occultation, Equatorial Kelvin wave propagation, Convective activity
Author: Noersomadi and Tri
Wahyu Hadi
Journal Code: jpfisikagg100018
