This article reviews the development of a global non-hydrostatic model, focusing on the pioneering research of the Non-hydrostatic Icosahedral Atmospheric Model (NICAM). Very high resolution global atmospheric circulation simulations with horizontal mesh spacing of approximately O (km) were conducted using recently developed supercomputers. These types of simulations were conducted with a specifically designed atmospheric global model based on a quasi-uniform grid mesh structure and a non-hydrostatic equation system. This review describes the development of each dynamical and physical component of NICAM, the assimilation strategy and its related models, and provides a scientific overview of NICAM studies conducted to date.

This study presents the projected urban climate for the 2070s’ August in the three largest urban areas, Tokyo, Osaka, and Nagoya in Japan. To accurately evaluate the urban climate, the simulations use the Weather Research and Forecast (WRF) model with 3-km grid increment coupled to an urban canopy model (UCM). To project future urban climate, the simulations apply dynamical downscaling to three GCMs (MIROC3.2-medres, MRI-CGCM2.3.2a, CSIRO-Mk3.0) and use the ensemble average for results. The results provide estimates of the heat stress to future residents of Tokyo, Osaka, and Nagoya.The WRF-UCM model reproduces the observed spatial distribution of the surface air temperature in the 2000s’ August, giving an all-domain mean bias of -1.2°C and RSME of 2.7°C. For Tokyo, Nagoya, and Osaka, these biases are -0.6, -0.1, and -0.4°C. Moreover, the diurnal temperature variations at these urban stations are well reproduced. The projected monthly average August temperatures in the 2070s are about 2.3°C higher than those in the 2000s at the three urban areas and comparable to those in the record-breaking hot summer of 2010. (Predictions by individual ensemble members differ by 0.8-1.2°C.) As a result, urban areas will experience uncomfortable sleeping nights nearly every day in August, with roughly as many heat-induced sleeping-discomfort nights as those in 2010. Moreover, application of the wet-bulb globe temperature (WBGT) shows that people in Tokyo will be warned not to strenuously exercise outdoors for 62% of the daytime hours in the 2070s, a sharp increase from the 30% of the 2000s. (Predictions by individual ensemble members range from 54-67%). Osaka and Nagoya will have even more restrictions on outdoor exercise. Finally, the urban heat island intensity is 1.5°C in Tokyo of the 2070s, comparable to the background climate warming of 2.3°C

Precipitation measurements from the Tropical Rainfall Measuring Mission satellite indicate that annual rainfall over the sea in the vicinity of western Sumatra Island is among the highest on the earth, and most of this rainfall occurs during nighttime. Surface meteorological observations at Tabing on the western coast of the island show frequent occurrences of sudden offshore winds accompanied by an abrupt drop in surface temperatures in the late afternoon and evening. Model simulations for a 1-month period during the rainy season of the region successfully simulate the satellite-observed regional distribution and diurnal variation of rainfall. The simulation results show that convection develops across a wide area over the mountainous areas of the island at similar times in the afternoon with the development of thermally induced local circulations. At these times of the day, convection over the sea along the western coast of the island is suppressed by the thermally and topographically induced diurnal changes in the boundary layer flow. When convection over the mountains of the island dissipates in the late afternoon and evening, a zone of cold surface outflow along the western coast results from the mountain convection breaking out to the sea. Meanwhile, the convective inhibition offshore is reduced in the evening, and the offshore flow causes regular occurrences of convection over the sea near the coast. The triggered convective systems propagate offshore and westward in multicell cluster storms during nighttime, bringing heavy rainfall over the sea off the western coast of the island. Sensitivity experiments with a flat-topography model demonstrate that the frequent occurrence of offshore flow in the late afternoon and evening on the western coast is caused by the mountainous topography of the island and its induced afternoon convection. The mountains on the island and the resultant thermally and convectively induced local circulations can play an important role in the formation of nocturnal abundant rainfall over the sea west of Sumatra Island.