Madden-Julian Oscillation:  The oscillation is the most important tropical climatic phenomenon only second to the El Niño, and yet is still a big challenge for climate models to properly simulate. HHH and collaborators made a breakthrough in early 2010s by demonstrating that coupling a high-resolution one-column ocean mixed-layer model (named SIT) to the atmospheric general circulation model AGCM dramatically improves the simulation of the MJO to have realistic strength, period, and propagation speed. Better resolving the fine structure of upper ocean temperature, especially the warm layer, produces more vigorous atmosphere-ocean interaction and strengthens intraseasonal variations in both SST and atmospheric circulation. HHH was one of the first few researchers to systematically investigate the orographic effect of the Maritime Continent on the MJO, which is an important mechanism having been largely neglected in the MJO research and recently receiving more attention because of the Year of Maritime Continent field campaign.

Multiscale Interaction in the Western North Pacific:  HHH and collaborators explored the multiscale interaction between tropical cyclone (TC), submonthly perturbation, and intraseasonal oscillation in the western North Pacific (WNP) during the boreal summer. They found that the existence of TCs significantly enhanced the monsoon trough and weakened the subtropical high in the WNP, and amplified the intraseasonal–interannual climate variability by 40–60 percent. This finding suggests that TC is a part of climate system and should be considered as an integral component to understand climate variability and climate change.

Weather and climate extremes:  HHH and collaborators conducted a series of studies on record-breaking extreme events and proposed that the compound effect of various influencing factors caused the weather and climate extremes. Each seemingly random event might be caused by different combination of various factors. This randomness is seemingly the reason for the low predictability of the extremes and why statistical study such as composite or correlation analysis often failed to explain the extremes. Global warming would result in an increase in the probability of synchronization of various influencing factors and increase the occurrence probability of weather and climate extremes.

Climate model development:  HHH organized an effort at climate model development in 2011 under the support of the MOST to nurture local talents in climate modeling and develop/implement climate models for the use in Taiwan. Since 2011, a climate model team has been established with the ability in modifying the existing climate models and implementing new modules developed locally. This effort has led to the implementation of Taiwan Earth System Model (TaiESM) developed locally, the High-resolution Atmospheric Model (GFDL, 25 and 50 km) developed by the GFDL and the extremely high-resolution (13 km) fvGFS-tw with a nested domain (3 km) over Taiwan.

Climate change projection under RCP emission scenarios:  Using the high-resolution projection data from the HiRAM and MRI-AGCM (including d4PDF data) and also coarser-resolution CMIP5/6 models (including TaiESM) to conduct a series of climate change studies with the focus on East Asian monsoon and climate systems (e.g., front, drought, atmospheric river) that affect Taiwan.