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Downscaling Seasonal Precipitation Forecasts over East Africa with Deep Convolutional Neural Networks

Advances in Atmospheric Sciences 2024年第3期41卷 449-464页

作者： Temesgen Gebremariam ASFAW Jing-Jia LUO institute for Climate and Application research(ICAR)/CIC-FEMD/KLME/ILCEC Nanjing University of Information Science and TechnologyNanjing 210044China institute of geophysics Space Science and astronomy Addis Ababa UniversityAddis Ababa 1176Ethiopia

This study assesses the suitability of convolutional neural networks(CNNs) for downscaling precipitation over East Africa in the context of seasonal forecasting. To achieve this, we design a set of experiments that compare different CNN configurations and deployed the best-performing architecture to downscale one-month lead seasonal forecasts of June–July–August–September(JJAS) precipitation from the Nanjing University of Information Science and Technology Climate Forecast System version 1.0(NUIST-CFS1.0) for 1982–2020. We also perform hyper-parameter optimization and introduce predictors over a larger area to include information about the main large-scale circulations that drive precipitation over the East Africa region, which improves the downscaling results. Finally, we validate the raw model and downscaled forecasts in terms of both deterministic and probabilistic verification metrics, as well as their ability to reproduce the observed precipitation extreme and spell indicator indices. The results show that the CNN-based downscaling consistently improves the raw model forecasts, with lower bias and more accurate representations of the observed mean and extreme precipitation spatial patterns. Besides, CNN-based downscaling yields a much more accurate forecast of extreme and spell indicators and reduces the significant relative biases exhibited by the raw model predictions. Moreover, our results show that CNN-based downscaling yields better skill scores than the raw model forecasts over most portions of East Africa. The results demonstrate the potential usefulness of CNN in downscaling seasonal precipitation predictions over East Africa,particularly in providing improved forecast products which are essential for end users.

关键词： East Africa seasonal precipitation forecasting downscaling deep learning convolutional neural networks(CNNs)

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Three dimensional velocity model and its tectonic implications at China Seismic Experimental Site,eastern margin of the Tibetan Plateau

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Science China Earth Sciences 2024年第7期67卷 2268-2290页

作者： Jianping WU Yan CAI Wei WANG Weilai WANG Changzai WANG Lihua FANG Yaning LIU Jing LIU institute of geophysics China Earthquake AdministrationBeijing 100081China Beijing Baijiatuan Earth Science national Observation and research Station Beijing 1095China Beijing Earthquake Agency Beijing 100080China

The China Seismic Experimental Site(CSES)is located at the intersection of the Tibetan Plateau,South China Block,and Indian Plate and has complex geological settings and intense crustal deformation,making it one of the most seismically active areas in Chinese mainland.A high-resolution,three-dimensional(3D)crust-mantle velocity structure is crucial for understanding seismotectonic environments,lithospheric deformation mechanisms,and deep dynamic *** first constructed a high-vertical-resolution 3D initial velocity model using the joint inversion of receiver functions and surface waves and then obtained a 3D P-and S-wave velocity model(CSES-VM1.0)with the highest lateral resolution of 0.25°for the CSES using double-difference *** to the limitations of the Sn observation data,the resolution of the S-wave velocity model in the lower crust and upper mantle was reduced,making it closer to the initial model provided by joint inversion.A comparison with explosive-source seismic data showed that the synthetic P-wave first-arrival travel times of the new model were closer to the observations than those of the previous velocity *** velocity cross-sections across the source areas of the 2022 Lushan MS6.1 and Ludian MS6.8 earthquakes reveal that the former earthquake occurred near a weak contact zone between the Tibetan Plateau and Sichuan Basin,and the rupture of the latter earthquake occurred in a granitic area,with the northern end blocked by rigid high-velocity bodies.A clear high-velocity anomaly zone is distributed along the western margin of the Yangtze Block,revealing the spatial distribution of Neoproterozoic intermediate-basic *** high-velocity zone significantly controls the morphology of fault zones and influences the rupture processes of major *** northeast-southwest and north-south trending high-velocity anomalies were found near Panzhihua,potentially related to Neoproterozoic and Middle-Late Permian intermediate

关键词： Eastern Tibetan Plateau China Seismic Experimental Site Yangtze Block Velocity model Double-difference tomography

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Toward a Direct Measurement of the Cosmic Acceleration: The Pilot Observation of HI 21 cm Absorption Line at FAST

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research in astronomy and Astrophysics 2024年第7期24卷 50-58页

作者： Jiangang Kang Chang-Zhi Lu Tong-Jie Zhang Ming Zhu institute for Frontiers in astronomy and Astrophysics Beijing Normal University School of Physics and astronomy Beijing Normal University national Astronomical Observatories Chinese Academy of Sciences

This study presents results on detecting neutral atomic hydrogen（H I） 21 cm absorption in the spectrum of PKS PKS1413+13 at redshift z = 0.24670041. The observation was conducted by FAST, with a spectral resolution of10 Hz, using 10 minutes of observing time. The global spectral profile is examined by modeling the absorption line using a single Gaussian function with a resolution of 10 kHz within a 2 MHz bandwidth. The goal is to determine the rate of the latest cosmic acceleration by directly measuring the redshift evolution of the H I 21 cm absorption line with Hubble flow toward a common background quasar over a decade or longer time span. This will serve as a detectable signal generated by the accelerated expansion of the Universe at redshift z < 1, referred to as redshift drift z（5） or the SL effect. The measured H I gas column density in this DLA system is approximately equivalent to the initial observation value, considering uncertainties of the spin temperature of a spiral host galaxy. The high signal-to-noise ratio of 57,obtained at a 10 kHz resolution, strongly supports the feasibility of using the H I 21 cm absorption line in DLA systems to accurately measure the redshift drift rate at a precision level of around 10-10per decade.

关键词： (cosmology:) cosmological parameters (cosmology:) dark energy cosmology: observations cosmology: theory ISM: clouds radio lines: galaxies radio lines: ISM

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What is the Role of Gravity,Turbulence and Magnetic Fields in High-mass Star Formation Clouds?

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research in astronomy and Astrophysics 2024年第6期24卷 21-27页

作者： An-Xu Luo Hong-Li Liu Guang-Xing Li Sirong Pan Dong-Ting Yang School of Physics and astronomy Yunnan UniversityKunming 650091China South-Western institute for astronomy research Yunnan UniversityKunming 650500China

To explore the potential role of gravity,turbulence and magnetic fields in high-mass star formation in molecular clouds,this study revisits the velocity dispersion–size(σ–L)and density–size(ρ–L)scalings and the associated turbulent energy spectrum using an extensive data *** sample includes various hierarchical density structures in high-mass star formation clouds,across scales of 0.01–100 *** observeσ∝L^(0.26)andρ∝L^(-1.54)scalings,converging toward a virial equilibrium state.A nearly flat virial parameter–mass(α_(vir)-M)distribution is seen across all density scales,withα_(vir)values centered around unity,suggesting a global equilibrium maintained by the interplay between gravity and turbulence across multiple *** turbulent energy spectrum(E(k))analysis,based on theσ–L andρ–L scalings,yields a characteristic E(k)∝k^(-1.52).These findings indicate the potential significance of gravity,turbulence,and possibly magnetic fields in regulating dynamics of molecular clouds and high-mass star formation therein.

关键词： ISM:clouds stars:formation stars:kinematics and dynamics

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Lithospheric strength of the Anatolian plateau and implications for strong earthquake activity in Turkey

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Geodesy and Geodynamics 2024年第3期15卷 209-218页

作者： Yuhang Pan Shi Chen Wen Shi institute of geophysics China Earthquake AdministrationBeijing 100081China Beijing Baijiatuan Earth Science national Observation and research Station Beijing 100095China

On February 6, 2023, the doublet earthquake including two main shocks with magnitudes M_(W)7.8 and M_(W)7.5, occurred near the western side of the East Anatolian Fault at the southeast boundary of the Anatolian Plateau in Turkey. Based on the WGM2012 Bouguer gravity anomaly data and the Etopo1topography data, this study first introduced a joint inversion of admittance and coherence functions and used the Bayesian optimal parameter estimation method to obtain the effective elastic thickness Teand loading ratio F of the lithosphere for various tectonic units in the Anatolian Plateau. Secondly, we discussed the characteristics and influencing factors of the lithospheric mechanical strength and analyzed its relationship with seismic activity. The lithospheric mechanical strength of the Anatolian Plateau showed clear lateral heterogeneity and a "weak-strong-weak" spatial pattern from east to west,reflecting various tectonic processes. At last, the strong seismic activity was found where the lithospheric strength was low in the Anatolian Plate. We also incorporated GPS strain rate and other results to investigate the tectonic background and primary causes of the M_(W)7.8 and M_(W)7.5 doublet earthquakes in Turkey. The results have a good insight into urban safety design in the Turkish region, including postdisaster rehabilitation, earthquake hazard assessment, and loss reduction.

关键词： Effective elastic thickness Anatolian plateau Turkey doublet earthquakes Bayesian optimization

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On the Performances of Estimating Stellar Atmospheric Parameters from CSST Broad-band Photometry

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research in astronomy and Astrophysics 2024年第4期24卷 161-173页

作者： Rui-Feng Shi Yang Huang Xin-Yi Li Hua-Wei Zhang School of astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China South-Western institute for astronomy research Yunnan UniversityKunming 650500China CAS Key Lab of Optical astronomy Key Laboratory of Space Astronomy and TechnologyNational Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China College of Physics and Electronic Engineering Qilu Normal UniversityJinan 250200China Department of astronomy School of PhysicsPeking UniversityBeijing 100871China Kavli institute for astronomy and Astrophysics Peking UniversityBeijing 100871China

Deriving atmospheric parameters of a large sample of stars is of vital importance to understand the formation and evolution of the Milky *** surveys,especially those with near-ultraviolet filters,can offer accurate measurements of stellar parameters,with the precision comparable to that from low/medium resolution *** this study,we explore the capability of measuring stellar atmospheric parameters from Chinese Space Station Telescope(CSST)broad-band photometry(particularly in the near-ultraviolet bands),based on synthetic colors derived from model *** find that colors from the optical and near-ultraviolet filter systems adopted by CSST show significant sensitivities to the stellar atmospheric parameters,especially the *** to our mock data tests,the precision of the photometric metallicity is quite high,with typical values of0.17 and 0.20 dex for dwarf and giant stars,*** precision of the effective temperature estimated from broad-band colors are within 50 K.

关键词： methods:data analysis stars:abundances surveys

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3D and 2D topographic correction to estimated geothermal gradient from the base of gas hydrate stability zone in the Andaman Forearc Basin

Energy Geoscience

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Energy Geoscience 2024年第2期5卷 314-320页

作者： Uma Shankar Department of geophysics Institute of ScienceBHUVaranasiIndia

Methane gas hydrate related bottom-simulating reflectors(BSRs)are imaged based on the in-line and cross-line multi-channel seismic(MCS)data from the Andaman Forearc *** depth of the BSR depends on pressure and temperature and pore water *** these assumptions,the BSR depth can be used to estimate the geothermal gradient(GTG)based on the availability of in-situ temperature *** calculation is done assuming a 1D conductive model based on available in-situ temperature measurement at site NGHP-01-17 in the study ***,in the presence of seafloor topography,the conductive temperature field in the subsurface is affected by lateral refraction of heat,which focuses heat in topographic lows and away from topographic *** 1D estimate of GTG in the Andaman Forearc Basin has been validated by drilling results from the NGHP-01 expedition.2D analytic modeling to estimate the effects of topography is performed earlier along selected seismic profiles in the study *** study extended to estimate the effect of topography in 3D using a numerical *** corrected GTG data allow us to determine GTG values free of topographic *** difference between the estimated GTG and values corrected for the 3D topographic effect varies up to~5℃/*** conclude that the topographic correction is relatively small compared to other uncertainties in the 1D model and that apparent GTG determined with the 1D model captures the major features,although the correction is needed prior to interpreting subtle features of the derived GTG maps.

关键词： Gas hydrate BSR Geothermal gradient 3D and 2D topographic modeling Andaman Forearc Basin

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Methodology for local correction of the heights of global geoid models to improve the accuracy of GNSS leveling

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Geodesy and Geodynamics 2024年第1期15卷 42-49页

作者： Stepan Savchuk Alina Fedorchuk institute of Navigation Military University of AviationDeblinPoland Department of Higher Geodesy and astronomy Lviv Polytechnic National UniversityLvivUkraine

At present,one of the methods used to determine the height of points on the Earth’s surface is Global Navigation Satellite System(GNSS)*** is possible to determine the orthometric or normal height by this method only if there is a geoid or quasi-geoid height model *** paper proposes the methodology for local correction of the heights of high-order global geoid models such as EGM08,EIGEN-6C4,GECO,and XGM2019e_*** methodology was tested in different areas of the research field,covering various relief *** dependence of the change in corrected height accuracy on the input data was analyzed,and the correction was also conducted for model heights in three tidal systems:"tide free","mean tide",and"zero tide".The results show that the heights of EIGEN-6C4 model can be corrected with an accuracy of up to 1 cm for flat and foothill terrains with the dimensionality of 1°×1°,2°×2°,and 3°×3°.The EGM08 model presents an almost identical *** EIGEN-6C4 model is best suited for mountainous relief and provides an accuracy of 1.5 cm on the 1°×1°*** height correction accuracy of GECO and XGM2019e_2159 models is slightly poor,which has fuzziness in terms of numerical fluctuation.

关键词： GNSS leveling Global geoid model Gravity anomaly Weight data Correcting data

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Assembly of functional carboxymethyl cellulose/polyethylene oxide/anatase TiO_(2) nanocomposites and tuning the dielectric relaxation, optical, and photoluminescence performances

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Journal of Semiconductors 2024年第7期45卷 26-38页

作者： Asmaa M.Ismail Abeer A.Reffaee Fawzy G.El Desouky Spectroscopy Department Physics Research InstituteNational Research CentreGizaCairo 12622Egypt Microwave Physics and Dielectrics Department National Research CentreDokkiCairoEgypt Solid State Physics Department Physics Research InstituteNational Research CentreGizaCairo 12622Egypt

Nanocomposite films consisting of carboxymethyl cellulose,polyethylene oxide(CMC/PEO),and anatase titanium diox-ide(TO)were produced by the use of sol-gel and solution casting ***2 nanocrystals were effectively incorporated into CMC/PEO polymers,as shown by X-ray diffraction(XRD)and attenuated total reflectance fourier transform infrared(ATR-FTIR)*** roughness growth is at high levels of TO nanocrystals(TO NCs),which means increasing active sites and defects in CMC/*** differential scanning calorimetry(DSC)thermograms,the change in glass transition temperature(Tg)val-ues verifies that the polymer blend interacts with TO *** increment proportions of TO NCs have a notable impact on the dielectric performances of the nanocomposites,as *** electrical properties of the CMC/PEO/TO nanocomposite undergo significant *** nanocomposite films exhibit a red alteration in the absorption edge as the concentration of TO NCs increases in the polymer *** decline in the energy gap is readily apparent as the weight percentage of TO NCs *** photoluminescence(PL)emission spectra indicate that the sites of the luminescence peak maximums show slight variation;peaks get wider,while their intensities decrease dramatically as the concentration of TO *** nanocomposite materials show potential for multifunctional applications including optoelectronics,antireflection coatings,pho-tocatalysis,light emitting diodes,and solid polymer electrolytes.

关键词： anatase TiO_(2) CMC/PEO nanocomposites optical photoluminescent electrical optoelectronics

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Scintillation Arc from FRB 20220912A

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Science China(Physics,Mechanics & astronomy) 2024年第1期67卷 134-142页

作者： Zi-Wei Wu Robert AMain Wei-Wei Zhu Bing Zhang Peng Jiang Jia-Rui Niu Jin-Lin Han Di Li Ke-Jia Lee Dong-Zi Li Yuan-Pei Yang Fa-Yin Wang Rui Luo Pei Wang Chen-Hui Niu Heng Xu Bo-Jun Wang Wei-Yang Wang Yong-Kun Zhang Yi Feng De-Jiang Zhou Yong-Hua Xu Can-Min Deng Yu-Hao Zhu national Astronomical Observatories Chinese Academy of SciencesBeijing 100101China Max-Planck-Institut für Radioastronomie Bonn 53121Germany institute for Frontier in astronomy and Astrophysics Beijing Normal UniversityBeijing 102206China Nevada Center for Astrophysics and Department of Physics and astronomy University of NevadaLas VegasNV 89154USA CAS Key Laboratory of FAST National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China School of astronomy University of Chinese Academy of SciencesBeijing 100049China NAOC-UKZN Computational Astrophysics Centre University of KwaZulu-NatalDurban 4000South Africa Department of astronomy Peking UniversityBeijing 100871China Kavli institute for astronomy and Astrophysics Peking UniversityBeijing 100871China Cahill Center for astronomy and Astrophysics California Institute of TechnologyPasadena 91125USA South-Western institute For astronomy research Yunnan UniversityKunming 650504China School of astronomy and Space Science Nanjing UniversityNanjing 210093China Key Laboratory of Modern astronomy and Astrophysics(Nanjing University) Ministry of EducationNanjing 210023China CSIRO Space and astronomy Epping 1710Australia Department of astronomy School of Physics and Materials ScienceGuangzhou UniversityGuangzhou 510006China research Center for Intelligent Computing Platforms Zhejiang LaboratoryHangzhou 311100China Yunnan Observatories Chinese Academy of SciencesKunming 650011China Guangxi Key Laboratory for Relativistic Astrophysics Department of PhysicsGuangxi UniversityNanning 530004China

We present the interstellar scintillation analysis of fast radio burst(FRB)20220912A during its extremely active episode in 2022using data from the Five-hundred-meter Aperture Spherical Radio Telescope(FAST).We detect a scintillation arc in the FRB’s secondary spectrum,which describes the power in terms of the scattered FRB signals’time delay and Doppler *** arc indicates that the scintillation is caused by a highly localized *** analysis favors a Milky Way origin of the ionized interstellar medium(IISM)for the localized scattering medium but cannot rule out a host galaxy *** present our method for detecting the scintillation arc,which can be applied generally to sources with irregularly spaced bursts or *** methods could help shed light on the complex interstellar environment surrounding the FRBs and in our Galaxy.

关键词： fast radio burst scintillation FRB 20220912A

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