Transport pathways from the Northern Hemisphere surface into the North American upper troposphere‐lower stratosphere (NA UTLS) during summertime are diagnosed from Boundary Impulse Response idealized tracers implemented at the Northern Hemisphere surface. In ensemble average, air masses enter the NA UTLS region via deep convection above Central America, and then slowly mix into the higher latitudes. However, fast transport pathways with a modal age around two weeks are evident in some tracer ensembles. For these rapid transport pathways, the tracers first reach the UTLS region over the eastern Pacific and the Gulf of Mexico as a result of enhanced deep convection and vertical advection, followed by horizontal transport over the United States by a stronger than normal UTLS anticyclone circulation.

中文翻译：

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夏季北美平流层和低平流层的不频繁，快速运输途径

从北半球表面实现的边界冲激响应理想示踪剂可以诊断出夏季从北半球表面到北美对流层-低平流层（NA UTLS）的运输途径。在总体平均水平上，气团通过中美洲上方的深对流进入NA UTLS地区，然后缓慢地混入较高的纬度。但是，在某些示踪团中，模式运输年龄大约为两周的快速运输途径是显而易见的。对于这些快速运输路径，由于深度对流和垂直对流的增强，示踪剂首先到达东太平洋和墨西哥湾的UTLS地区，然后通过比正常的UTLS反气旋流通更强的美国水平运输。