Investigation of Transport Processes in Association with the Asian Summer Monsoon Circulation Using Balloons, Lidars, and Aircrafts − Japanese Collaboration with the ACCLIP

It is well known that the Asian Summer Monsoon (ASM) circulation is a planetary-scale, rather isolated airmass in the UTLS in the boreal summer, which contains high concentration of various pollutants of surface origin from China, India, and Southeast Asian countries. The ASM circulation exhibits distinct intra-seasonal variability, including large-scale eastward shedding vortices passing over the Japanese archipelago, with the frequency of about three times per month during the summer. Measuring the airmass of these eastward shedding vortices over Japan enables us to study the long-range transport and chemical processes of airmass originated from the Asian Monsoon countries. There is a planned, USA-led, international field campaign, Asian Summer Monsoon Chemical and Climate Impact Project (ACCLIP) for the summer of 2020 by using two US research aircrafts based on Okinawa and several other instruments and platforms.

In the first half of the presentation, we will introduce a collaborative research plan by the ACCLIP-Japan team with Japan-based researchers, which includes balloon measurements of trace gases and aerosol particles, lidar measurements of aerosol particles, and the CONTRAIL (Comprehensive Observation Network for TRace gases by AIrLiner) passenger aircraft measurements of trace gases, as well as studies using global models and dynamical and chemical reanalysis data sets.

In the rest of the presentation, we will discuss the results of the lidar measurements of UTLS aerosol and cirrus particles at Fukuoka (33.55°N, 130.36°E) and at Tsukuba (36.1°N, 140.1°E), Japan during the period between July and September of 2018. By combining analysis of ECMWF CAMS chemical reanalysis data and backward trajectory calculations, we will discuss the origin of the enhanced aerosol layer just above the tropopause observed over the two stations, in association with the eastward shedding vortices from the ASM circulation.