The Asian Summer Monsoon (ASM) is one of the most dominant circulation systems in boreal summer. During high monsoon season, the highly polluted Asian boundary air is rapidly transported into the Upper Troposphere and Lower Stratosphere (UTLS) by strong convective activities, where they are horizontally retained in the Asian Summer Monsoon Anticyclone (ASMA). Thus, trace gases originating from different sources from the boundary layer as well as through out the UTLS mix and cause different features in the UTLS. With the upwelling motion inside the upper part of the ASMA and the ASMA breaking down in late September, these air pollutants can enter into the global stratosphere, having potential impacts on the worldwide climate. Studying the distribution of trace gases in the ASMA therefore enables better a understanding of important dynamical and chemical processes during the ASM. During the Stratoclim aircraft field campaign from Kathmandu, Nepal, in July/August 2017, we measured gaseous HNO3 and HCN in the ASMA with the innovative Jülich FUNMASS, a Chemical Ionization Time-of-Flight mass spectrometer, on board of the high altitude research aircraft M-55 Geophysica. Comparisons were made between in situ measurements and satellite data (HNO3 from Aura-MLS and HCN from ACE-FTS). Tracer correlations were studied among HNO3, HCN, CO and O3 (from airborne instrument COLD and FOZAN, respectively). Backward trajectories from Lagrangian models TRACZILLA and CLaMS were used to identified HCN structures resulting from convective events. A filament of high HNO3 and high O3 and at the same time high HCN at around 440 K (potential temperature) drew our attention. Missing signature in CO and low water vapor indicate that we are not dealing with a fresh convection injection. The possibility of inmixing of older air from downward transport from tropical stratosphere will be discussed with regards to the formation of the filament in HNO3, O3 and HCN.
A case study on gaseous HNO3 and HCN in the Asian Summer Monsoon Anticyclone based on airborne measurements and Lagrangian model simulations
Fabrizio Ravegnani;Francesco D'Amato;Silvia Viciani;
2019
Abstract
The Asian Summer Monsoon (ASM) is one of the most dominant circulation systems in boreal summer. During high monsoon season, the highly polluted Asian boundary air is rapidly transported into the Upper Troposphere and Lower Stratosphere (UTLS) by strong convective activities, where they are horizontally retained in the Asian Summer Monsoon Anticyclone (ASMA). Thus, trace gases originating from different sources from the boundary layer as well as through out the UTLS mix and cause different features in the UTLS. With the upwelling motion inside the upper part of the ASMA and the ASMA breaking down in late September, these air pollutants can enter into the global stratosphere, having potential impacts on the worldwide climate. Studying the distribution of trace gases in the ASMA therefore enables better a understanding of important dynamical and chemical processes during the ASM. During the Stratoclim aircraft field campaign from Kathmandu, Nepal, in July/August 2017, we measured gaseous HNO3 and HCN in the ASMA with the innovative Jülich FUNMASS, a Chemical Ionization Time-of-Flight mass spectrometer, on board of the high altitude research aircraft M-55 Geophysica. Comparisons were made between in situ measurements and satellite data (HNO3 from Aura-MLS and HCN from ACE-FTS). Tracer correlations were studied among HNO3, HCN, CO and O3 (from airborne instrument COLD and FOZAN, respectively). Backward trajectories from Lagrangian models TRACZILLA and CLaMS were used to identified HCN structures resulting from convective events. A filament of high HNO3 and high O3 and at the same time high HCN at around 440 K (potential temperature) drew our attention. Missing signature in CO and low water vapor indicate that we are not dealing with a fresh convection injection. The possibility of inmixing of older air from downward transport from tropical stratosphere will be discussed with regards to the formation of the filament in HNO3, O3 and HCN.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
