Location
East-West Center, University of Hawai'i at Manoa (Honolulu, Hawai'i)
Start Date
16-10-2012 5:30 PM
End Date
16-10-2012 7:30 PM
Document Type
Poster
Description
The match method is applied to the quantification of the dehydration process in the tropical tropopause layer (TTL) over the western Pacific. The match pairs are sought from the Soundings of Ozone and Water in the Equatorial Region (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 the validity of the isentropic treatment and to check possible water injection by deep convection, consistency between the sonde data and analysis field, and conservation of the ozone content. Among those pairs remaining, we found some cases corresponding to the first quantitative value of dehydration associated with horizontal advection in the TTL. The statistical features on the dehydration for the air parcels advected in the lower TTL are derived from the match pairs. Match analysis indicates that ice nucleation starts before the relative humidity with respect to ice (RHice) reaches the value of 207 ± 81% (1σ) and that the air mass is dehydrated until the RHice reaches 83 ± 30% (1σ). The efficiency of dehydration is estimated as the relaxation time of the relative humidity for the supersaturated air parcel to approach the saturation state. This is empirically estimated from the match pairs as the quantity that reproduces the second water vapor observation given the first observed water vapor amount and the sequence of the saturation mixing ratio of the match air mass exposed during the advection. The relaxation time is found to range from 2 to 3 hours, which agrees with those reported from previous studies.
Dehydration in the TTL estimated from the water vapor match
East-West Center, University of Hawai'i at Manoa (Honolulu, Hawai'i)
The match method is applied to the quantification of the dehydration process in the tropical tropopause layer (TTL) over the western Pacific. The match pairs are sought from the Soundings of Ozone and Water in the Equatorial Region (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 the validity of the isentropic treatment and to check possible water injection by deep convection, consistency between the sonde data and analysis field, and conservation of the ozone content. Among those pairs remaining, we found some cases corresponding to the first quantitative value of dehydration associated with horizontal advection in the TTL. The statistical features on the dehydration for the air parcels advected in the lower TTL are derived from the match pairs. Match analysis indicates that ice nucleation starts before the relative humidity with respect to ice (RHice) reaches the value of 207 ± 81% (1σ) and that the air mass is dehydrated until the RHice reaches 83 ± 30% (1σ). The efficiency of dehydration is estimated as the relaxation time of the relative humidity for the supersaturated air parcel to approach the saturation state. This is empirically estimated from the match pairs as the quantity that reproduces the second water vapor observation given the first observed water vapor amount and the sequence of the saturation mixing ratio of the match air mass exposed during the advection. The relaxation time is found to range from 2 to 3 hours, which agrees with those reported from previous studies.
