Observational characteristics of double tropopauses
Observational characteristics of double tropopauses
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DOI：
10.1029/2006jd007904
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发表时间：
2007-04
影响因子：
--
通讯作者：
W. Randel;D. Seidel;L. Pan
中科院分区：
文献类型：
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作者：
W. Randel;D. Seidel;L. Pan
[1]在热带外的温度廓线往往表现出多个对流层顶（定义使用直减率定义）。在这项工作中，我们研究了双对流层顶的观测特征的基础上无线电探空仪，ERA 40再分析，GPS无线电掩星温度廓线。双对流层顶与副热带急流附近的热对流层顶的特征断裂有关，其中低纬度（热带）对流层顶延伸到高纬度，覆盖在低对流层顶上;这种行为可以延伸到极地纬度。从无线电探空仪和全球定位系统数据得出的对流层顶统计数据显示出良好的一致性，全球定位系统数据可以绘制地球仪上的双重对流层顶特征。北半球中纬度地区的出现频率有很强的季节性变化，冬季廓线中的出现频率为50%-70%，夏季半球大部分地区的出现频率为10%（除了亚洲季风反气旋向极地一侧的局部最大值）。SH中纬度统计数据显示，季节变化较小，全年发生频率为100%-50%（冬季最高）。在热带外，气旋环流系统的出现频率要高得多。在热带地区很少观察到双对流层顶。气球和卫星对臭氧的测量表明，具有双对流层顶的剖面在平流层下部的臭氧系统地比具有单对流层顶的剖面少。臭氧观测与气象数据一起确定，双对流层顶是从热带向副热带急流核心上方高纬度地区输送增强的区域。
[1] Temperature profiles in the extratropics often exhibit multiple tropopauses (as defined using the lapse rate definition). In this work we study the observational characteristics of double tropopauses based on radiosondes, ERA40 reanalysis, and GPS radio occultation temperature profiles. Double tropopauses are associated with a characteristic break in the thermal tropopause near the subtropical jet, wherein the low latitude (tropical) tropopause extends to higher latitudes, overlying the lower tropopause; this behavior can extend to polar latitudes. Tropopause statistics derived from radiosondes and GPS data show good agreement, and GPS data allow mapping of double tropopause characteristics over the globe. The occurrence frequency shows a strong seasonal variation over NH midlatitudes, with ∼50-70% occurrence in profiles during winter, and a small fraction (∼10%) over most of the hemisphere during summer (with the exception of a localized maximum over the poleward flank of the Asian monsoon anticyclone). SH midlatitude statistics show a smaller seasonal variation, with occurrence frequencies of ∼30-50% over the year (maximum during winter). Over the extratropics, the occurrence frequency is substantially higher for cyclonic circulation systems. Few double tropopauses are observed in the tropics. Ozone measurements from balloons and satellites show that profiles with double tropopauses exhibit systematically less ozone in the lower stratosphere than those with a single tropopause. Together with the meteorological data, the ozone observations identify double tropopauses as regions of enhanced transport from the tropics to higher latitudes above the subtropical jet cores.