I have been working on regular ozonesonde sounding in Indonesia since I was a graduate student. I have been making reprocessing/quality control of these ozonesonde data steadily. At the graduate school, I investigated two problems based on these data: One is a regional-scale air pollution issue, i.e., tropospheric ozone enhancement by extensive forest fire events during the El Nino events, and the other is stratosphere-to-troposphere ozone transport process in association with equatorial Kelvin waves. These researches directed me to two grand challenges, i.e., "Atmospheric Processes in the Tropical Tropopause Layer (TTL)" and "Climate Observations," which are my current research areas.
For the Atmospheric Processes in the TTL, I conducted several field observations of ozone, water vapor, cloud particles, temperature, wind, turbulence, etc. mainly under an international project, the Soundings of Ozone and Water Vapor in the Equatorial Region (SOWER). I also used various types of global climate models to understand the TTL processes. Currently, I am going back to the basics of the Earth science, i.e., the measurements, and developing new balloon-borne instruments for water vapor and cloud particles. The TTL is the pathway for tropospheric air to the stratosphere, and thus determines the initial conditions for the stratospheric composition. Also, the TTL is directly linked to the tropical meteorology. In the TTL, all the key atmospheric processes (dynamics, transport, photochemistry, microphysics, and radiation) are coupled; this makes the TTL region complicated and fascinating.
For the Climate Observations, I am developing new instruments mentioned above, and also working as an active member of two international observation networks, the Southern Hemisphere Additional Ozonesondes (SHADOZ) and GCOS Reference Upper Air Network (GRUAN). Accurate measurement of climatic variability in the upper air is not an easy task from the viewpoint of technology and international situation, and needs dedicated effort by many experts worldwide. Also, in 2013 I started an international reanalysis intercomparison project, the SPARC Reanalysis Intercomparison Project (S-RIP). The reanalysis datasets are provided by some meteorological agencies and are used as one of the key climate datasets to understand the climate variability. However, there had been few systematic and coordinated activities for intercomparison and validation of different reanalysis datasets before. In the S-RIP, we focus on diagnostics related to the stratospheric processes (including coupling processes with the troposphere and the surface) and inter-compare and validate several reanalysis datasets by collaborating with many researchers and reanalysis centers. Furthermore, since 2016, I have been working as a core member in the WCRP Task Team for Intercomparison of ReAnalyses (TIRA) that covers wider fields such as energy budget and water cycle.
I am a faculty member of Course in Atmosphere-Ocean and Climate Dynamics, Graduate School of Environmental Sciences, Hokkaido University.