Takeshi Horinouchi

A three‐dimensional simulation was conducted with a cloud‐resolving model to investigate mesoscale gravity waves generated by cumulus convection that propagate to the mesospheric and lower thermospheric (MLT) region. It is found that both individual convective turrets and mesoscale convective systems excite gravity waves, resulting in a broad scale distribution. Waves excited by the former have conically shaped phase surfaces as previously reported and are conspicuous up to around the stratopaus

It is recognized that the resolved tropical wave spectrum can vary considerably among general circulation models (GCMs) and that these differences can have an important impact on the simulated climate. A comprehensive comparison of low-latitude waves is presented for the December-January-February period using highfrequency data from nine GCMs participating in the GCM Reality Intercomparison Project for Stratospheric Processes and Their Role in Climate (GRIPS; SPARC). Quantitative measures of the

The interaction between convectively excited waves and the mean zonal wind in the equatorial lower stratosphere is investigated with a simplified general circulation model (GCM). The model has T42 truncation, and the vertical resolution is about 700 m in the stratosphere. Although it is an "aquaplanet" model with uniform sea surface temperature, cumulus convection in low latitudes has realistic hierarchical structures with reasonable space–time spectral distributions. The model produced an oscil

Venus is covered with thick clouds. Ultraviolet (UV) images at 0.3–0.4 microns show detailed cloud features at the cloud-top level at about 70 km, which are created by an unknown UV-absorbing substance. Images acquired in this wavelength range have traditionally been used to measure winds at the cloud top. In this study, we report low-latitude winds obtained from the images taken by the UV imager, UVI, onboard the Akatsuki orbiter from December 2015 to March 2017. UVI provides images with two fi

Venus has a thick atmosphere that rotates 60 times as fast as the surface, a phenomenon known as super-rotation. We use data obtained from the orbiting Akatsuki spacecraft to investigate how the super-rotation is maintained in the cloud layer, where the rotation speed is highest. A thermally induced latitudinal-vertical circulation acts to homogenize the distribution of the angular momentum around the rotational axis. Maintaining the super-rotation requires this to be counteracted by atmospheric

Abstract Through extensive modeling efforts, it has been established that the ongoing global warming will increase the overall precipitation associated with the East Asian summer monsoon, but the future change of its spatial distribution has not reached a consensus. In this study, meridional shifts of the mei-yu–baiu rainband are studied in association with the subtropical jet by using outputs from atmosphere–ocean coupled climate models provided by CMIP5. The models reproduce observed associati

Abstract It has been revealed that in summertime, precipitation is enhanced to the south of the upper-level tropopausal potential vorticity contours, which are accompanied by instantaneous jets, over the eastern coastal region of China to the northwestern Pacific. It is frequently exhibited as precipitation bands ranging in size from over a thousand to several thousands of kilometers long. In this study, an analysis was conducted to quantify the relationship depending on the phase of upper-level

Atmospheric transport between the tropics and the extratropics, in the lowest part of the stratosphere during Northern Hemisphere winter, is investigated. The role of synoptic‐scale disturbances that propagate laterally into the tropics is examined using the middle atmosphere version of the National Center for Atmospheric Research Community Climate Model Version 3 general circulation model. In the lower stratosphere, synoptic‐scale Rossby waves propagate vigorously from the northern (i.e., winte

A prolonged heavy rainfall event occurred in Kyushu in early July 2020. Its large-scale environmental factors are investigated with observational and reanalysis data. Seven-day precipitation and moisture flux convergence around Kyushu were the greatest among the last 30 years. This pronounced convergence was maintained by nearly steady moisture influx, and the persistent upper-level trough to the northwest enhanced the ratio of moisture convergence to the influx. The magnitude of instantaneous m

A number of studies have investigated atmospheric gravity waves (GWs) using temperature profiles from GPS radio occultation (RO). This study is the first to report the horizontal structures of GWs obtained directly by using multiple profiles based on the GPS RO data from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC)/FORMOSAT‐3 mission. It was found that the horizontal locations of profiles obtained from successive passages of multiple COSMIC satellites were

Correlation-based cloud tracking has been extensively used to measure atmospheric winds, but still difficulty remains. In this study, aiming at developing a cloud tracking system for Akatsuki, an artificial satellite orbiting Venus, a formulation is developed for improving the relaxation labeling technique to select appropriate peaks of cross-correlation surfaces which tend to have multiple peaks. The formulation makes an explicit use of consistency inherent in the type of cross-correlation meth