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Masaki Satoh - One of the best experts on this subject based on the ideXlab platform.
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intraseasonal variability and tropical cyclogenesis in the western north pacific simulated by a global nonhydrostatic Atmospheric Model
Geophysical Research Letters, 2015Co-Authors: Masuo Nakano, Masaki Satoh, Tomoe Nasuno, Masahiro SawadaAbstract:Thirty-one successive daily experiments for extended-range (30 day) forecasts are conducted using a global nonhydrostatic Atmospheric Model without convective parameterization. The Model successfully reproduces tropical cyclogenesis (TCG) in six out of eight cases in the western North Pacific in August 2004, up to 2 weeks prior to cyclone formation. Detailed analyses reveal that Typhoon Songda's genesis is related to the eastward extension of the monsoon trough associated with the intraseasonal variability (ISV). The successful simulation of the migration and extension of the monsoon trough leads to a 2 week forecast for Songda's genesis. These findings highlight the need for a Model capable of predicting the modulation of large-scale fields by ISV for TCG forecasts and that a global nonhydrostatic cloud-system-resolving Model is a promising tool for TCG forecasts.
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The Non-hydrostatic Icosahedral Atmospheric Model: description and development
Progress in Earth and Planetary Science, 2014Co-Authors: Masaki Satoh, Hirofumi Tomita, Hiroaki Miura, Hisashi Yashiro, Chihiro Kodama, Tatsuya Seiki, Akira T Noda, Yohei Yamada, Daisuke Goto, Masahiro SawadaAbstract: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.
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nonhydrostatic icosahedral Atmospheric Model nicam for global cloud resolving simulations
Journal of Computational Physics, 2008Co-Authors: Masaki Satoh, Taroh Matsuno, Hirofumi Tomita, Hiroaki Miura, Tomoe NasunoAbstract:A new type of ultra-high resolution Atmospheric global circulation Model is developed. The new Model is designed to perform ''cloud resolving simulations'' by directly calculating deep convection and meso-scale circulations, which play key roles not only in the tropical circulations but in the global circulations of the atmosphere. Since cores of deep convection have a few km in horizontal size, they have not directly been resolved by existing Atmospheric general circulation Models (AGCMs). In order to drastically enhance horizontal resolution, a new framework of a global Atmospheric Model is required; we adopted nonhydrostatic governing equations and icosahedral grids to the new Model, and call it Nonhydrostatic ICosahedral Atmospheric Model (NICAM). In this article, we review governing equations and numerical techniques employed, and present the results from the unique 3.5-km mesh global experiments-with O(10^9) computational nodes-using realistic topography and land/ocean surface thermal forcing. The results show realistic behaviors of multi-scale convective systems in the tropics, which have not been captured by AGCMs. We also argue future perspective of the roles of the new Model in the next generation Atmospheric sciences.
Bin Wang - One of the best experts on this subject based on the ideXlab platform.
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comparison of three ice cloud optical schemes in climate simulations with community Atmospheric Model version 5
Atmospheric Research, 2018Co-Authors: Wenjie Zhao, Bin Wang, Yiran Peng, Bingqi Yi, Jiangnan LiAbstract:Abstract A newly implemented Baum-Yang scheme for simulating ice cloud optical properties is compared with existing schemes (Mitchell and Fu schemes) in a standalone radiative transfer Model and in the global climate Model (GCM) Community Atmospheric Model Version 5 (CAM5). This study systematically analyzes the effect of different ice cloud optical schemes on global radiation and climate by a series of simulations with a simplified standalone radiative transfer Model, Atmospheric GCM CAM5, and a comprehensive coupled climate Model. Results from the standalone radiative Model show that Baum-Yang scheme yields generally weaker effects of ice cloud on temperature profiles both in shortwave and longwave spectrum. CAM5 simulations indicate that Baum-Yang scheme in place of Mitchell/Fu scheme tends to cool the upper atmosphere and strengthen the thermodynamic instability in low- and mid-latitudes, which could intensify the Hadley circulation and dehydrate the subtropics. When CAM5 is coupled with a slab ocean Model to include simplified air-sea interaction, reduced downward longwave flux to surface in Baum-Yang scheme mitigates ice-albedo feedback in the Arctic as well as water vapor and cloud feedbacks in low- and mid-latitudes, resulting in an overall temperature decrease by 3.0/1.4 °C globally compared with Mitchell/Fu schemes. Radiative effect and climate feedback of the three ice cloud optical schemes documented in this study can be referred for future improvements on ice cloud simulation in CAM5.
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different contact angle distributions for heterogeneous ice nucleation in the community Atmospheric Model version 5
Atmospheric Chemistry and Physics, 2014Co-Authors: Corinna Hoose, Bin Wang, Yong WangAbstract:Abstract. In order to investigate the impact of different treatments for the contact angle (α) in heterogeneous ice nucleating properties of natural dust and black carbon (BC) particles, we implement the classical-nucleation-theory-based parameterization of heterogeneous ice nucleation (Hoose et al., 2010) in the Community Atmospheric Model version 5 (CAM5) and then improve it by replacing the original single-contact-angle Model with the probability-density-function-of-α (α-PDF) Model to better represent the ice nucleation behavior of natural dust found in observations. We refit the classical nucleation theory (CNT) to constrain the uncertain parameters (i.e., onset α and activation energy in the single-α Model; mean contact angle and standard deviation in the α-PDF Model) using recent observation data sets for Saharan natural dust and BC (soot). We investigate the impact of the time dependence of droplet freezing on mixed-phase clouds and climate in CAM5 as well as the roles of natural dust and soot in different nucleation mechanisms. Our results show that, when compared with observations, the potential ice nuclei (IN) calculated by the α-PDF Model show better agreement than those calculated by the single-α Model at warm temperatures (T; T > −20 °C). More ice crystals can form at low altitudes (with warm temperatures) simulated by the α-PDF Model than compared to the single-α Model in CAM5. All of these can be attributed to different ice nucleation efficiencies among aerosol particles, with some particles having smaller contact angles (higher efficiencies) in the α-PDF Model. In the sensitivity tests with the α-PDF Model, we find that the change in mean contact angle has a larger impact on the active fraction at a given temperature than a change in standard deviation, even though the change in standard deviation can lead to a change in freezing behavior. Both the single-α and the α-PDF Model indicate that the immersion freezing of natural dust plays a more important role in the heterogeneous nucleation than that of soot in mixed-phase clouds. The new parameterizations implemented in CAM5 induce more significant aerosol indirect effects than the default parameterization.
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two moment bulk stratiform cloud microphysics in the grid point Atmospheric Model of iap lasg gamil
Advances in Atmospheric Sciences, 2013Co-Authors: Xiangjun Shi, Bin Wang, Xiaohong Liu, Minghuai WangAbstract:A two-moment bulk stratiform microphysics scheme, including recently developed physically-based droplet activation/ice nucleation parameterizations has been implemented into the Grid-point Atmospheric Model of IAP LASG (GAMIL) as an effort to enhance the Model’s capability to simulate aerosol indirect effects. Unlike the previous one-moment cloud microphysics scheme, the new scheme produces a reasonable representation of cloud particle size and number concentration. This scheme captures the observed spatial variations in cloud droplet number concentrations. Simulated ice crystal number concentrations in cirrus clouds qualitatively agree with in situ observations. The longwave and shortwave cloud forcings are in better agreement with observations. Sensitivity tests show that the column cloud droplet number concentrations calculated from two different droplet activation parameterizations are similar. However, ice crystal number concentration in mixed-phased clouds is sensitive to different heterogeneous ice nucleation formulations. The simulation with high ice crystal number concentration in mixed-phase clouds has less liquid water path and weaker cloud forcing. Furthermore, ice crystal number concentration in cirrus clouds is sensitive to different ice nucleation parameterizations. Sensitivity tests also suggest that the impact of pre-existing ice crystals on homogeneous freezing in old clouds should be taken into account.
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evaluation of grid point Atmospheric Model of iap lasg version 2 gamil2
Advances in Atmospheric Sciences, 2013Co-Authors: Lijuan Li, Bin Wang, Yong Wang, Li Dong, Si Shen, Ning Hu, Wenyu Huang, Ye Pu, Guangwen YangAbstract:The Grid-point Atmospheric Model of IAP LASG version 2 (GAMIL2) has been developed through upgrading the deep convection parameterization, cumulus cloud fraction and two-moment cloud microphysical scheme, as well as changing some of the large uncertain parameters. In this paper, its performance is evaluated, and the results suggest that there are some significant improvements in GAMIL2 compared to the previous version GAMIL1, for example, the components of the energy budget at the top of atmosphere (TOA) and surface; the geographic distribution of shortwave cloud radiative forcing (SWCF); the ratio of stratiform versus total rainfall; the response of Atmospheric circulation to the tropical ocean; and the eastward propagation and spatiotemporal structures of the Madden Julian Oscillation (MJO). Furthermore, the indirect aerosols effect (IAE) is −0.94 W m−2, within the range of 0 to −2 W m−2 given by the IPCC 4th Assessment Report (2007). The influence of uncertain parameters on the MJO and radiation fluxes is also discussed.
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sensitivity of the grid point Atmospheric Model of iap lasg gamil1 1 0 climate simulations to cloud droplet effective radius and liquid water path
Advances in Atmospheric Sciences, 2008Co-Authors: Yuqing Wang, Bin Wang, Tianjun ZhouAbstract:This paper documents a study to examine the sensitivity to cloud droplet effective radius and liquid water path and the alleviation the energy imbalance at the top of the atmosphere and at the surface in the latest version of the Grid-point Atmospheric Model of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (IAP) (GAMIL1.1.0). Considerable negative biases in all flux components, and thus an energy imbalance, are found in GAMIL1.1.0. In order to alleviate the energy imbalance, two modifications, namely an increase in cloud droplet effective radius and a decrease in cloud liquid water path, have been made to the cloud properties used in GAMIL. With the increased cloud droplet effective radius, the single scattering albedo of clouds is reduced, and thus the reflection of solar radiation into space by clouds is reduced and the net solar radiation flux at the top of the atmosphere is increased. With the reduced cloud optical depth, the net surface shortwave radiation flux is increased, causing a net warming over the land surface. This results in an increase in both sensible and latent heat fluxes over the land regions, which is largely balanced by the increased terrestrial radiation fluxes. Consequently, the energy balance at the top of atmosphere and at the surface is achieved with energy flux components consistent with available satellite observations.
Tomoe Nasuno - One of the best experts on this subject based on the ideXlab platform.
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intraseasonal variability and tropical cyclogenesis in the western north pacific simulated by a global nonhydrostatic Atmospheric Model
Geophysical Research Letters, 2015Co-Authors: Masuo Nakano, Masaki Satoh, Tomoe Nasuno, Masahiro SawadaAbstract:Thirty-one successive daily experiments for extended-range (30 day) forecasts are conducted using a global nonhydrostatic Atmospheric Model without convective parameterization. The Model successfully reproduces tropical cyclogenesis (TCG) in six out of eight cases in the western North Pacific in August 2004, up to 2 weeks prior to cyclone formation. Detailed analyses reveal that Typhoon Songda's genesis is related to the eastward extension of the monsoon trough associated with the intraseasonal variability (ISV). The successful simulation of the migration and extension of the monsoon trough leads to a 2 week forecast for Songda's genesis. These findings highlight the need for a Model capable of predicting the modulation of large-scale fields by ISV for TCG forecasts and that a global nonhydrostatic cloud-system-resolving Model is a promising tool for TCG forecasts.
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nonhydrostatic icosahedral Atmospheric Model nicam for global cloud resolving simulations
Journal of Computational Physics, 2008Co-Authors: Masaki Satoh, Taroh Matsuno, Hirofumi Tomita, Hiroaki Miura, Tomoe NasunoAbstract:A new type of ultra-high resolution Atmospheric global circulation Model is developed. The new Model is designed to perform ''cloud resolving simulations'' by directly calculating deep convection and meso-scale circulations, which play key roles not only in the tropical circulations but in the global circulations of the atmosphere. Since cores of deep convection have a few km in horizontal size, they have not directly been resolved by existing Atmospheric general circulation Models (AGCMs). In order to drastically enhance horizontal resolution, a new framework of a global Atmospheric Model is required; we adopted nonhydrostatic governing equations and icosahedral grids to the new Model, and call it Nonhydrostatic ICosahedral Atmospheric Model (NICAM). In this article, we review governing equations and numerical techniques employed, and present the results from the unique 3.5-km mesh global experiments-with O(10^9) computational nodes-using realistic topography and land/ocean surface thermal forcing. The results show realistic behaviors of multi-scale convective systems in the tropics, which have not been captured by AGCMs. We also argue future perspective of the roles of the new Model in the next generation Atmospheric sciences.
Hirokazu Endo - One of the best experts on this subject based on the ideXlab platform.
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changes in precipitation extremes projected by a 20 km mesh global Atmospheric Model
Weather and climate extremes, 2016Co-Authors: Akio Kitoh, Hirokazu EndoAbstract:Abstract High-resolution Modeling is necessary to project weather and climate extremes and their future changes under global warming. A global high-resolution Atmospheric general circulation Model with grid size about 20 km is able to reproduce climate fields as well as regional-scale phenomena such as monsoonal rainfall, tropical and extratropical cyclones, and heavy precipitation. This 20-km mesh Model is applied to project future changes in weather and climate extremes at the end of the 21st century with four different spatial patterns in sea surface temperature (SST) changes: one with the mean SST changes by the 28 Models of the Coupled Model Intercomparison Project Phase 5 (CMIP5) under the Representative Concentration Pathways (RCP)-8.5 scenario, and the other three obtained from a cluster analysis, in which tropical SST anomalies derived from the 28 CMIP5 Models were grouped. Here we focus on future changes in regional precipitation and its extremes. Various precipitation indices averaged over the Twenty-two regional land domains are calculated. Heavy precipitation indices (maximum 5-day precipitation total and maximum 1-day precipitation total) increase in all regional domains, even where mean precipitation decrease (Southern Africa, South Europe/Mediterranean, Central America). South Asia is the domain of the largest extreme precipitation increase. In some domains, different SST patterns result in large precipitation changes, possibly related to changes in large-scale circulations in the tropical Pacific.
T N Palmer - One of the best experts on this subject based on the ideXlab platform.
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interannual tropical rainfall variability in general circulation Model simulations associated with the Atmospheric Model intercomparison project
Journal of Climate, 1996Co-Authors: K R Sperber, T N PalmerAbstract:Abstract The interannual variability of rainfall over the Indian subcontinent, the African Sahel, and the Nordeste region of Brazil have been evaluated in 32 Models for the period 1979–88 as part of the Atmospheric Model Intercomparison Project (AMIP). The interannual variations of Nordeste rainfall are the most readily captured, owing to the intimate link with Pacific and Atlantic sea surface temperatures. The precipitation variations over India and the Sahel are less well simulated. Additionally, an Indian monsoon wind shear index was calculated for each Model. Evaluation of the interannual variability of a wind shear index over the summer monsoon region indicates that the Models exhibit greater fidelity in capturing the large-scale dynamic fluctuations than the regional-scale rainfall variations. A rainfall/SST teleconnection quality control was used to objectively stratify Model performance. Skill scores improved for those Models that qualitatively simulated the observed rainfall/El Nino- Southern Osc...
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interannual tropical rainfall variability in general circulation Model simulations associated with the Atmospheric Model intercomparison project
Journal of Climate, 1996Co-Authors: Kenneth R. Sperber, T N PalmerAbstract:Abstract The interannual variability of rainfall over the Indian subcontinent, the African Sahel, and the Nordeste region of Brazil have been evaluated in 32 Models for the period 1979–88 as part of the Atmospheric Model Intercomparison Project (AMIP). The interannual variations of Nordeste rainfall are the most readily captured, owing to the intimate link with Pacific and Atlantic sea surface temperatures. The precipitation variations over India and the Sahel are less well simulated. Additionally, an Indian monsoon wind shear index was calculated for each Model. Evaluation of the interannual variability of a wind shear index over the summer monsoon region indicates that the Models exhibit greater fidelity in capturing the large-scale dynamic fluctuations than the regional-scale rainfall variations. A rainfall/SST teleconnection quality control was used to objectively stratify Model performance. Skill scores improved for those Models that qualitatively simulated the observed rainfall/El Nino- Southern Osc...