Deep moist atmospheric convection is a key element of the weather and climate system for transporting mass, momentum, thermal energy. It has been challenging to simulate realistically in global models because large gap spatial scales between (10 0 km) motions 4 km). We conducted first ever subkilometer simulation described features convection. Through series grid‐refinement resolution testing, we found that an essential change statistics occurred around 2 km grid spacing. The structure,...

Abstract. We examine the influence of grid aspect ratio horizontal to vertical spacing on turbulence in planetary boundary layer (PBL) a large-eddy simulation (LES). In order clarify and distinguish them from other artificial effects caused by numerical schemes, we used fully compressible meteorological LES model with explicit scheme temporal integration. The influences are investigated series sensitivity tests parameter sweeps spatial resolution ratio. confirmed that mixing length eddy...

This study investigated the impact of several cloud microphysical schemes on trade wind cumulus in large eddy simulation model. To highlight differences due to component, we developed a fully compressible model, which excluded implicit scheme and approximations as much possible. The three schemes, one-moment bulk, two-moment spectral bin were used for sensitivity experiments other components fixed. Our new model using successfully reproduced cumuli, reliable performance was confirmed....

This study statistically investigates the characteristics of tropical cyclones (TCs) undergoing rapid intensification (RI) in western North Pacific 37 years from 1979 to 2015 and relevant atmospheric oceanic environments. Among 900 TCs, 201 TCs RI (RI-TCs) are detected by our definition as a wind speed increase 30 kt (15.4 m s −1 ) or more 24-h period. RI-TCs potentially occur throughout year, with low variation RI-TC occurrence rate among seasons. Conversely, annual varies widely. In El...

Abstract A mechanism for the transition of tropical cyclones (TCs) to spontaneous rapid intensification (RI) phase is proposed based on numerical results a three-dimensional full-physics model. The simulated TC divided into three subphases according rate intensification: 1) slowly intensifying phase, 2) an RI and 3) adjustment toward quasi-steady state. evolution vortex diagnosed by energy budget analysis degree axisymmetric structure vortex, determined be axisymmetrized 12 h before onset...

Abstract Structural changes that precede rapid intensification (RI) of tropical cyclones (TCs) are examined in a full-physics model by conducting large ensemble (270) idealized TC simulations. The processes leading to RI representative case with moderate shear consistent previous studies for weakly sheared cases. most distinct the vortex tilt and size begin decrease more rapidly 6 h before onset RI. A vorticity budget analysis upper layer around low-level center reveals vertical is increased...

Triggering processes for the rapidly intensifying phase of a tropical cyclone (TC) were investigated on basis numerical experiments using three-dimensional nonhydrostatic model. The results revealed that rapid intensification simulated TC commenced following formation circular cloud, which occurred about 12 h after became essentially axisymmetric. cloud (eyewall) evolved from cloudy convective cell was originally generated near radius maximum wind speed (RMW). development in eyewall closely...

This article reviews the major outcomes of a 5-year (2011–2016) project using K computer to perform global numerical atmospheric simulations based on non-hydrostatic icosahedral model (NICAM). The was made available public in September 2012 and used as primary resource for Japan's Strategic Programs Innovative Research (SPIRE), an initiative investigate five strategic research areas; NICAM fell under area climate weather simulation sciences. Combining with high-performance computing has...

The success of sub-kilometer global atmospheric simulation opens the door for resolving deep convections, which are fundamental elements cloudy disturbances that drive circulation. A previous study found essential change in simulated convection properties occurred at a grid spacing about 2 km as mean. In grid-refinement experiments, we conducted further comprehensive analysis global-mean state and characteristics convection, to clarify difference by location environment. We was different...

Resolution dependence was found in the simulated diurnal precipitation cycle over land tropics. We conducted a series of grid refinement experiments atmosphere from 14 km to 0.87 using global high-resolution model without any convection parameterizations. In experiment, peak earlier and at higher. The characteristics changed spacing around 2-3 km. started increase morning experiments, suggesting that small-scale moist became active late morning. lower-resolution began afternoon. As well as...

Abstract. Multi-frequency radars offer enhanced detection of clouds and precipitation compared to single-frequency systems, are able make more accurate retrievals when several frequencies available simultaneously. An evaluation a spaceborne three-frequency Ku-/Ka-/W-band radar system is presented in this study, based on modeling reflectivities from the results global cloud-resolving model with 875 m grid spacing. To produce reflectivities, scattering has been developed for each hydrometeor...

Abstract The degree of gradient wind balance was investigated in a number tropical cyclones (TCs) simulated under realistic environments. results global-scale numerical simulations without cumulus parameterization were used, with horizontal mesh size 7 km. On average, azimuthally averaged maximum tangential velocities at 850 (925) hPa the TCs 0.72% (1.95%) faster than wind–balanced velocity (GWV) during quasi-steady periods. Of TCs, 75% satisfied radius speed (RMW) and 925 to within about...

The relationship of tropical cyclone (TC) future intensity change to current and axisymmetricity deduced from hourly Global Satellite Mapping Precipitation (GSMaP) data was investigated. Axisymmetricity is a metric that correlates positively with the magnitude axisymmetric component rainfall rate negatively asymmetric component. samples used were all TCs existed in western North Pacific basin during years 2000–15. results showed that, development stage, intensification at time, 6 12 h after...

Abstract This study analyzed the observed data of precipitation and PM 2.5 concentration collected over two a half years at Tsujido, Fujisawa City, to examine quantitative relationship between quantities. It was that decreased as increased. A composite analysis revealed on average decreases by 20.99% 1 h after onset compared before, which is statistically significant based paired t ‐test. The concentrations 8 period from 5 (−5 h) before 3 (+3 precipitation, with particularly dramatic...

Abstract This study found that there is a radius within which the sea surface flux for moist enthalpy plays vital role in determining intensity of tropical cyclone. From results numerical experiments using an axisymmetric nonhydrostatic model, it was shown when fluxes are modified radius, suddenly changes on short timescale. As long as diminishes outside this cyclone does not decrease. In simulated cyclone, locates 7–8 times maximum wind speed. Copyright © 2010 Royal Meteorological Society

Abstract Deep moist convection is an element of cloud disturbances such as Madden‐Julian oscillation ( MJO ), tropical cyclones TCs mid‐latitudinal low depressions MDL and fronts FRT ). However, differences in characteristics remain unclear. We first clarified the statistical features (structure, intensity, environmental parameters) various simulated by a global simulation with sub‐kilometre grid spacing. The TC ) was tall strong (weak) upward motion, driven large convective available...

Abstract An analytical model of maximum potential intensity (PI) for tropical cyclones (TCs) incorporating wind‐induced ocean cooling is developed on the basis Emanuel's PI theory. The consists a one‐dimensional and an axisymmetric TC vortex that translating at constant speed. advances upon previous approaches by accounting size shape. determined radius winds radially integrating effect mixing using specified wind profile. resulting analytic agrees well with numerical solutions, new better...

The environmental conditions for tropical cyclone genesis are examined by numerical experiment.We focus on the case of a non-developing disturbance showed features in Pacific Area Long-term Atmospheric observation Understanding climate change 2010 (PALAU2010) campaign over western North Pacific.We clarify importance presence abundant moisture around continuous convection and demonstrate that collocation mid-level vortex low-level vortex, i.e., persistence an upright structure vortices, is...

We investigated the temporal evolution of two types diagram produced by a three-dimensional large-eddy simulation: Contoured Frequency Optical Depth Diagram (CFODD) and correlation pattern between cloud droplet effective radius optical thickness (RE-COT pattern). The CFODD obtained statistically method, in past study, suggested that transition stages were included diagram, but this paper is first confirms similar structure time-series analysis. Our results suggest part lifecycle; from...

Abstract To clarify the effect of fluctuations in surface stress and heat fluxes on intensity a mature-state hurricane, sensitivity analysis is performed by using cloud-permitting nonhydrostatic axisymmetric adjoint model. The response function our experiment tangential velocity at top boundary layer eyewall. As result an integration backward to 4 min prior specified time, dipole pattern appears fields with respect vertical velocity, potential temperature, mixing ratio water vapor. A...