Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder

Ryuji Yoshida

Research Interests

  • Climate dynamics
  • Mesoscale convective systems
  • Tropical cyclone genesis
  • Large-scale Circulation
  • Numerical Modeling

In the past, the largescale environment was a large focus to understand tropical cyclone genesis. However, none of the past studies successfully provide a clear link between largescale and mesoscale processes of tropical cyclone genesis because the mesoscale process has large variability. This motivated me to investigate the intermediate scale environment of tropical cyclone genesis. I developed a new objective analysis method of low-level flow patterns, and I have found that the intermediate scale environment mainly consists of shear line, confluence region of zonal winds, and easterly waves. More importantly, I have revealed that the flow patterns are modulated by inter-seasonal oscillation like MJO. These results have largely contributed to advance our understanding of tropical cyclone genesis by connecting largescale and mesoscale.

I have been involved in the projects for deep convection and convective systems, regional
climatology, and regional atmospheric model development. I joined the G8-call ICOMEX project, which is a collaborative project for global model development. I examined the performances of several global atmospheric models. Furthermore, I have developed model
frameworks for the regional model SCALE-RM. Especially, I have innovated a new
cost-effective online nesting procedure named as CONeP. It can reduce about
30% of elapsed time for calculation.

Current Research

Solar energy is a fundamental energy source for the atmosphere. A part of the incoming solar energy is reflected by clouds and does not reach the surface. Therefore, global cloud coverage is an important parameter to understand climate and its energy balance. However, clouds, especially shallow clouds are poorly represented in climate models. One of the causes is the low resolution, and several assumptions in cloud parameterization schemes used in climate models. For better understanding and projection of climate, an improvement of cloud representation is necessary. My supervisor, Dr. Takanobu Yamaguchi, found that vertical resolution enhancement improves the representation of shallow clouds, and developed an innovative scheme named the Framework for Improvement by Vertical Enhancement (FIVE; Yamaguchi et al. 2017). FIVE will be incorporated into the Energy Exascale Earth System Model (E3SM) developed by DOE. In this project, one of my goals is to study the advantageous effects of FIVE in climate simulations. Since a global climate simulation is very expensive, in the development stage a simple framework representing Earth’s general circulation is required. It has to have attributes like low cost of computation, and suitable for time integration over a climate-relevant period. Toward this goal, I started to build a two-dimensional (2D) simulation framework after arriving at my current post. 2D simulation can represent basic characteristics of Earth’s general circulation and is far less costly than three-dimensional simulation. I already succeeded in developing the framework of the 2D simulation and have started to execute 2D simulation of the general circulation with high resolution.

Honors and Awards

  • Young Scientists Encourage Prize, Numerical simulation of organization process of Vortical Disturance in PALAU2010 project, JAMSTEC Blue Earth 2011 (03, 2011).
  • 2017 JMSJ Award: Yoshida, R., Y. Miyamoto, H. Tomita, and Y. Kajikawa, "The effect of water vapor on tropical cyclone genesis: A numerical experiment of a non-developing disturbance observed in PALAU2010".