My expertise is in atmospheric sciences. I have been studying transport processes of atmospheric constituents, climatic variations in association with volcanic eruptions, and development and evaluation of various balloon-borne instruments. Internationally, I am involved in coordinated activities on evaluation of climate data sets and on climate observation networks. Recently, I re-started to be involved in ozone layer observations.
Transport processes of atmospheric constituents: I have done several studies focusing on the tropical tropopause layer (TTL) under the projects such as the regular ozone observation project in Indonesia (my Ph.D study), Southern Hemisphere ADditional OZonesondes (SHADOZ), and Soundings of Ozone and Water in the Equatorial Region (SOWER). Currently, my focus is on the Asian summer monsoon circulation.
Climatic variations with volcanic eruptions: This was originally motivated by the geoengineering proposals. Currently, using modern global atmospheric reanalysis data sets, re-evaluation of climatic variations in association with the past large-scale tropical eruptions is being made.
Development and evaluation of balloon-borne instruments: I was involved in development of water vapor sonde (Skydew), carbon-dioxide sonde, and cloud particle sondes (CPS, Cloudscope, and Rainscope), and in evaluation of water vapor sondes (Snow White, and CFH) and radiosondes (RS-11G, iMS-100, etc.).
Internationally coordinated activities: I have been leading the SPARC Reanalysis Intercomparison Project (S-RIP) since 2011, and been involved in SHADOZ since 1999 and GCOS Reference Upper Air Network (GRUAN) since 2006. I have also been involved in WCRP Task Team for Intercomparison of ReAnalyses (TIRA) since 2018.
Ozone layer observations: Since 2022, I have started regular ozone layer observations at Hokkaido University, Sapporo, Japan.
I am a faculty member of Course in Atmosphere-Ocean and Climate Dynamics, Graduate School of Environmental Sciences, Hokkaido University as well as School of Science (Earth and Planetary Sciences), Hokkaido University.