Computer Science – Sound
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.a31c0110i&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #A31C-0110
Computer Science
Sound
3300 Atmospheric Processes, 3311 Clouds And Aerosols, 3364 Synoptic-Scale Meteorology, 3374 Tropical Meteorology, 3389 Tides And Planetary Waves
Scientific paper
Stratospheric water vapor is controlled by the degree of dehydration the air parcels experienced on their entry into the stratosphere. The dehydration takes place in the tropical tropopause layer (TTL) over the western Pacific, where the air parcels are exposed to the lowest temperature during horizontal advection (cold trap hypothesis (Holton and Gettelman, 2001; Hatsushika and Yamazaki, 2003)). While, simplified treatment of the dehydration processes combined with trajectories reproduce water vapor variations reasonably well (Fueglistaler et al., 2005), extreme super saturation has been often observed in the TTL (Peter et al., 2006). Thus observational data are needed to quantify the efficiency of dehydration. We have been conducting the project Soundings of Ozone and Water in the Equatorial Region (SOWER) using chilled-mirror hygrometers in the western Pacific. Hasebe et al. (2007) suggested that the water content in the observed air parcels on many occasions was about twice as much as that expected from the minimum saturation mixing ratio during horizontal advection prior to sonde observation. To make this argument more quantitative, however, it is necessary to estimate the changed amount of water vapor by repeated observation of the same air parcel, the water vapor match. The match pairs are sought from the SOWER campaign network observations with the use of isentropic trajectories. For those pairs identified, extensive screening procedures are performed to verify the representativeness of the air parcel and to check possible water injection by deep convection. The match pairs are rejected when the sonde-observed temperature does not agree with spatio-temporary interpolated temperature of the ECMWF analysis field within a reasonable range, or the ozone mixing ratio is not conserved between the paired observations. Among those survived, we sought the cases which showed statistically significant dehydration. We estimated the ratios of the water mixing ratio observed by the first and the second sondes and the minimum saturation mixing ratio during advection. This gives the range of the maximum value of relative humidity with respect to ice. The range of 1.5 - 2.6 was found for the match pair on 362 K that showed a dehydration from 6.0 to 3.5 ppmv.
Fujiwara Motoyasu
Hasebe Fumio
Inai Y.
Nishi Nobuyuki
Ogino Satoshi
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