Spectral characteristics of lower-stratospheric gravity waves generated in idealized mei-yu front and tropical cyclone (TC) are compared by performing high-resolution simulations. The results suggest that the systems which organize convection in different forms can generate waves with distinctly different presentation. The mei-yu front appears as a linear zonal wave source and gravity waves are dominated by cross-frontal (meridional) propagating components. The northward (southward) components have dominant meridional wavelengths of 125-333 km (>250 km), periods of 100-200 min (83-143 min), and phase speeds of 0-15 m s −1 (15-20 m s −1 ). The TC appears as a point wave source and gravity waves propagate equally in various horizontal directions. The waves exhibit greater power and broader spectral distributions compared with those in the mei-yu front, with dominant horizontal wavelengths longer than 62.5 km, periods of 33-600 min, and phase speeds slower than~40 m s −1 .Atmosphere 2019, 10, 405 2 of 11 mei-yu front contains lots of convective cells, which successively form along the front and gradually organize into quasi-two-dimensional (2D) precipitation bandings, and thus tends to cause persistent precipitation [28][29][30]. It differs from the common midlatitude front by a weak temperature gradient but a strong moisture gradient, and the frontal zone is characterized by intense equivalent potential temperature gradient [31,32]. Sun [25] analyzed the mesoscale-β-scale gravity-wave activity during a mei-yu front heavy rain process using surface observation data. She identified the waves with wavelength of 200 km, amplitude of 2 hPa, and periods of 6-8 h. Hu [27] discussed the generation, propagation, and dispersion of gravity waves in the mei-yu front based on a linear model with a simple parameterized cumulus heating expression. Based on an idealized model constructed by Peng et al. [33], Wang et al. [34] recently performed high-resolution simulations to investigate the generation mechanism of gravity waves in the mei-yu front system. A mechanical oscillator mechanism was suggested as playing a dominant role in the generation of lower-stratospheric waves.Due to relatively coarse spatiotemporal resolution, most general circulation models (GCMs) have still been unable to resolve short-scale and high-frequency gravity waves precisely. Consequently, representing the effects of gravity waves in GCMs requires parameterization [35]. However, because of the complexity of convection-induced gravity waves, the relevant parameterization remains under development [36][37][38][39][40]. It has been a consensus that a comprehensive knowledge of convective waves is the premise of making a breakthrough in parameterization. Under this background, understanding convective gravity waves and their convective sources is not only a theoretical interest in wave dynamics but also essential to the improvement of gravity-wave parameterization in GCMs. This is because previous studies showed that the lack of an accurate understanding of ...
Under the strategic background of cultural revitalization, it is of great significance to study the evolving characteristics and influencing factors of museums to promote the prosperity and development of urban culture. Take the museums in Shandong province as the research object, based on the data from 1983–2021, the study was conducted by using Kernel Density Analysis, Spatial Autocorrelation, and Geodetector to reveal the spatial and temporal evolutionary characteristics of museums and their influencing factors within the domain of Shandong province. The research found that: 1) the number of museums shows a growth trend and can be divided into four stages: starting, rapid development, small growth, and high-speed development; the difference in the number in each city has a gradient, showing dispersion characteristics in different gradients; museums of historical and cultural themes and non-state museums occupy the main position in terms of quantity, and the trend of diversification of museum types is highlighted. 2) the spatial distribution is the cluster, showing a pattern of one center and multiple centers coexisting; the global distribution has a strong spatial correlation, and local high and low clusters change significantly; the center of gravity is concentrated near the geometric center of Shandong Province in an inverted V-shape migration. 3) The spatial pattern of museums in Shandong Province is formed under the comprehensive influence of policy, tourism, economy, culture, and education factors. The study has certain significance for promoting the development of cultural undertakings in Shandong Province and improving regional cultural competitiveness.
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