Observational and Numerical Modeling Study on Low Level Jet, Boundary Layer and Precipitating Cloud Microphysics in Tahope

This project mainly focuses on the cloud and precipitation microphysics processes of the mesoscale convective systems (MCSs) associated with the invaded typhoons and Mei-Yu systems, and the mesoscale atmospheric environment (e.g., the evolution of low-level jet, thermal and dynamical atmospheric boundary layer structures, and the moisture transport) using field campaign observations and numerical simulations. The research will emphasis on the low-level jets, land-sea breezes, mountain-valley breezes, local circulations, atmospheric boundary layer, and terrain effects on the initiation and development of MCSs during a typhoon or Mei-Yu front passes over Taiwan. The evolution of raindrop size distribution and precipitating cloud microphysics, as well as mesoscale conditions and dynamical/physical mechanisms associated with heavy orographic precipitation, will be investigated. For heavy rainfall cases, sensitivity tests of the planetary boundary layer parameterization, microphysics parameterization and terrain effects will be constructed using high-resolution WRF model. In addition, field campaign observations will be used to verify model simulation results. The above related physical processes for the development of heavy rainfall over Taiwan will be discussed using a combination of observations and numerical simulations. We will investigate three kinds of low-level jets (LLJs) that could contribute to heavy rainfall over Taiwan (synoptic-system-related low-level jet/SLLJ, barrier jet, and marine boundary layer jet/MBLJ). (1) The interaction between these LLJs and terrain; (2) the relationship between them and the Mei-Yu system; and (3) their impacts on the development and structure evolution of mesoscale convective systems associated with the Mei-Yu system and physical mechanisms of precipitation will be discussed. In addition, we will compare the development and evolution of thermal and dynamical atmospheric boundary layer structures and the moisture transport characteristics within the southwesterly monsoon flow/low-level jets during TAHOPE/PRECIP2020 (Typhoon and Mei-Yu periods) from soundings and wind profiler observations on Dongsha and Taiwan Islands. We will also analyze the characteristics of the heavy orographic precipitation resulting from the southwesterly flow associated with Typhoon. We will also discuss the evolution of raindrop size distribution and characteristics of other related precipitating cloud microphysics under different weather systems and mesoscale circulations.