Dehydration in the tropical tropopause layer estimated from the water vapor match
Dehydration in the tropical tropopause layer estimated from the water vapor match
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DOI：
10.5194/acp-13-8623-2013
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发表时间：
2013-09
影响因子：
6.3
通讯作者：
Y. Inai;F. Hasebe;M. Fujiwara;M. Shiotani;N. Nishi;S. Ogino;H. Vömel;S. Iwasaki;T. Shibata
中科院分区：
文献类型：
--
作者：
Y. Inai;F. Hasebe;M. Fujiwara;M. Shiotani;N. Nishi;S. Ogino;H. Vömel;S. Iwasaki;T. Shibata
我们应用多次观测到相同气团的匹配技术来研究与西太平洋热带对流层(TTL)水平平流有关的脱水过程。这些匹配是从赤道区臭氧和水探测(SEWER)活动网络观测所获得的廓线数据中获得的，该观测使用从欧洲中期天气预报中心(ECMWF)业务分析计算的等熵轨迹。对于识别的匹配，进行了广泛的筛选程序，以验证气团的代表性和等熵处理的有效性，并检查可能的深对流注水，探空仪数据与臭氧守恒分析场之间的一致性。在通过筛选试验的匹配中，我们发现了一些与TTL水平平流相关的脱水的第一个量化值相对应的事例。从匹配得到了TTL低层平流的气团脱水的统计特征。在350~360K的海拔范围内，成核阈值为146±19%(1)，而脱水似乎一直持续到约75%±23%(1)。脱水效率由过饱和气团达到饱和所需的松弛时间表示。考虑到第一次观测的水汽量和低TTL平流期间饱和混合比的历史，大约一小时的松弛时间相当好地再现了第二次水汽观测。
We apply the match technique, whereby the same air mass is observed more than once and such cases are termed a "match", to study the dehydration process asso- ciated with horizontal advection in the tropical tropopause layer (TTL) over the western Pacific. The matches are ob- tained from profile data taken by the Soundings of Ozone and Water in the Equatorial Region (SOWER) campaign network observations using isentropic trajectories calculated from European Centre for Medium-Range Weather Fore- casts (ECMWF) operational analyses. For the matches iden- tified, extensive screening procedures are performed to ver- ify the representativeness of the air parcel and the validity of the isentropic treatment, and to check for possible water injection by deep convection, consistency between the sonde data and analysis field referring to the ozone conservation. Among the matches that passed the screening tests, we iden- tified some cases corresponding to the first quantitative value of dehydration associated with horizontal advection in the TTL. The statistical features of dehydration for the air parcels advected in the lower TTL are derived from the matches. The threshold of nucleation is estimated to be 146 ± 19 % (1 ) in relative humidity with respect to ice (RHice), while dehydra- tion seems to continue until RHice reaches about 75± 23 % (1 ) in the altitude region from 350 to 360 K. The efficiency of dehydration expressed by the relaxation time required for the supersaturated air parcel to approach saturation is em- pirically determined from the matches. A relaxation time of approximately one hour reproduces the second water vapor observation reasonably well, given the first observed water vapor amount and the history of the saturation mixing ratio during advection in the lower TTL.