Abstracts for the 6th International GAME Conf.
3-5 December 2004
Kyoto Japan
Nonlinear influence of diurnal variations upon time-mean fields
Yoshihiro Tachibana (1), Eisho Azuma (2), Shin-Ya Ogino (3), Akira Watanabe (4)
(1) JAMSTEC / Tokai University
(2) Tokai University
(3) Kobe University
(4) Fukushima University
It is widely known that diurnal variations of temperature, humidity and wind in the tropics are large through the troposphere. We evaluated influence of these diurnal variations upon the atmospheric time-mean thermodynamic fields by using GPS radiosonde special observation network data covering Indochina Peninsula in 1998. GPS radiosondes launched every six hours in three observatories for about two weeks in rainy and dry seasons. By using these data, daily mean horizontal advections of temperature and moisture were evaluated through the troposphere. The daily mean horizontal advection term can be divided into two sub processes; daily-mean temperature advection by daily mean wind and daily mean temperature, and daily mean temperature advection by perturbation wind and perturbation temperature. Each perturbation field is approximated by sinusoidal cycle with a twenty-four-hour period by using the least squares methods based on the 4-times-a-day GPS observation data. This approximation mathematically enables us to evaluate the nonlinear influence of the pure diurnal time-scale terms on the time-mean fields. The contribution of the nonlinear terms to the daily mean temperature tendency in both dry and rainy seasons were large through the troposphere especially in the lower and middle troposphere. The results suggest that objective analysis data and numerical forecast models do not accurately portray the time-mean fields if they cannot properly represent the diurnal variations.
Submittal Information
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JAMSTEC / Tokai University | |
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Liberal Arts Education Center, Tokai Univ. Hiratsuka 2591292 | |
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