Ryuhei Yoshida

Convective Instability Associated with the Eastward-Propagating Rainfall Episodes over Eastern China during the Warm Season

AbstractAnalysis of the latest satellite rainfall and reanalysis datasets from 1998 to 2012 demonstrates that eastward-propagating rainfall episodes, which typically occur in late night and morning, are determinant factors for the rainfall diurnal cycle and climate anomalies over eastern China. The episode growth and propagation are facilitated by an elevated layer of conditionally unstable air in a mesoscale zone at their eastern leading edge. The convective available potential energy (CAPE), despite convection consumption and nocturnal cooling, decreases only from a high value to a moderate one during episode duration. An estimate of the CAPE generation budget suggests that low-level horizontal advection and vertical lifting of the warm moist air can produce sufficient CAPE to balance other stabilization effects, sustaining the mesoscale maximum of convective instability ahead of rainfall episodes. These instability geneses are pronounced at the convection growth stage and linked closely to a mesoscale ...

Influence of Land Cover Change on Regional Water Cycles in Eastern Siberia

AbstractThis study evaluated the effect of recent eastern Siberian land surface changes, such as water surface expansion, on water-energy fluxes and precipitation and focused on land surface parameters using a three-dimensional atmospheric model [the Japan Meteorological Agency Nonhydrostatic model (JMA-NHM)]. Five parameters were set (viz., surface albedo, evaporative efficiency, roughness length, heat capacity, and thermal conductivity), and a response of evaporation and precipitation was evaluated. Increased precipitation corresponded to 75% of the increased evaporation on interparameter average, indicating strong land–atmosphere coupling. Water-energy flux and precipitation responses to water surface expansion were evaluated by two methods: JMA-NHM and the parameter sensitivity method. The latter method used a linear combination of parameter sensitivity on the fluxes and precipitation and parameter changes with land surface change. JMA-NHM demonstrated an increase in evaporation and precipitation and ...

An Application of a Physical Vegetation Model to Estimate Climate Change Impacts on Rice Leaf Wetness

AbstractA physical vegetation model [the Two-Layer Model (2LM)] was applied to estimate the climate change impacts on rice leaf wetness (LW) as a potential indicator of rice blast occurrence. Japan was used as an example. Dynamically downscaled data at 20-km-mesh resolution from three global climate models (CCSM4, MIROC5, and MRI-CGCM3) were utilized for present (1981–2000) and future (2081–2100) climates under the representative concentration pathway 4.5 scenario. To evaluate the performance of the 2LM, the LW and other meteorological variables were observed for 108 days during the summer of 2013 at three sites on the Pacific Ocean side of Japan. The derived correct estimation rate was 77.4%, which is similar to that observed in previous studies. Using the downscaled dataset, the changes in several precipitation indices were calculated. The regionally averaged ensemble mean precipitation increased by 6%, although large intermodel differences were found. By defining a wet day as any day in which the daily...