The Asian Summer Monsoon (ASM) has garnered attention in recent years for its impacts on the composition of the upper troposphere and lower stratosphere (UTLS) via deep convection. A recent observational effort into this mechanism, the Asian summer monsoon Chemical and CLimate Impact Project (ACCLIP), sampled the composition of the ASM UTLS over the northwestern Pacific during boreal summer 2022 using two airborne platforms. In this work, we integrate Lagrangian trajectory modeling with convective cloud top observations to diagnose ASM convective transport which contributed to ACCLIP airborne observations. This diagnostic is applied to explore the properties of convective transport associated with prominent ASM sub-systems, revealing that convective transport along the East Asia Subtropical Front generally contained more pollutants than from South Asia, for species ranging in lifetime from days to months. The convective transport diagnostic is used to isolate three convective transport events over eastern Asia which had distinct chemical tracer relationship slopes, indicating the different economical behaviors of the contributing source regions. One of these transport events is explored in greater detail, where a polluted air mass was sampled from convection over the Northeast China Plain. This event was largely confined to 12-15 km altitude, which may be high enough to impact the composition of the stratosphere. Overall, the presented diagnosis of convective transport contribution to ACCLIP airborne sampling indicates a key scientific success of the campaign and enables process studies of the climate interactions from the two ASM sub-system.

Tropopause-penetrating overshooting convection (OC) can transport tropospheric air into and affect the composition of the lower stratosphere. During the warm season, OC occurs frequently over the contiguous United States, and the transport of plumes from these events is modulated by the flow over North America, which throughout June to August is characterized by a large-scale anticyclone in the upper troposphere and lower stratosphere. This study uses data from the Next Generation Weather Radar (NEXRAD) and the ERA5 reanalysis to locate OC during May–August of 2008 to 2020. Evidence of convective transport is found well above the 380 K isentrope, which is the top of the “lowermost stratosphere” and also the top of the stratospheric middleworld. By initializing massless particles within the volume of OC above the tropopause, we perform trajectory calculations to simulate the transport of OC plumes. With three-dimensional diabatic trajectory modeling in isentropic coordinates using winds from ERA5, we quantify the confinement within the anticyclone and the number of trajectories transported into the tropical and extratropical stratosphere. By evaluating the trajectory residence time in the North American region, we find that July exhibits the strongest confinement, with about a quarter of trajectories staying in the region for more than 11 days. It is shown that, together with sufficient injection height, convective injection that occurs south of the jet and/or into anticyclonic regimes increases the chances of air remaining in the stratosphere. After 30 days, 45% of all air masses injected above the tropopause remain in the global stratosphere.