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  • 1
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    Resonant Rossby waves in the north and south hemispheres (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
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    Publication Date: 2023-06-13
    Description: Rossby waves, present in both the Northern and Southern hemispheres, have a significant impact on severe weather patterns. The North Atlantic Oscillation (NAO) affects climate and weather in Europe and North America, and has been linked to extreme weather events (e.g., Hurrell et al., JC, 2003). Additionally, recurrent Rossby wave packets (RRWP) that possess strong zonal wavenumber 4 and 5 components have been associated with heatwaves in southeastern Australia (Mubashshir et al., WCD, 2022). Despite extensive research over the last century, fundamental questions regarding the nature of these high-impact Rossby waves remain unanswered. This study investigates their resonant characteristics, revealing that the NAO exhibits resonant behavior over a 35-day period, while the variability of the aforementioned RRWPs is linked to a quasi-mode (Zadra et al., JAS, 2002) resonating around 10 days. We will discuss the implications of these resonant behaviors in terms of teleconnections and forcing frequencies.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 2
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    Optimized Alternate Mapping Correlated K-distribution Method for Atmospheric Longwave Radiative Transfer (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
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    Publication Date: 2023-07-31
    Description: Radiative transfer models are widely applied in climate models to simulate vertical temperature perturbations caused by external radiative forcings. A large part of radiative transfer models is the infrared gaseous spectral transmittance scheme, which quantifies the longwave atmospheric absorption. A rapid infrared gaseous spectral transmittance scheme, called the optimized alternate mapping correlated K-distribution model (OMCKD), is introduced in this paper. To improve the accuracy of our scheme without increasing pseudo-monochromatic calculations, we introduce the optimal iteration method to automatically tune the equivalent absorption coefficients in the cumulative probability subspace. In addition, a new expression weighted by black-body radiation is introduced to calculate the equivalent absorption coefficient. The OMCKD simulates heating rate and radiation flux with errors of less than 0.12 K d-1 and 0.35 W m-2, respectively, below stratopause for standard atmospheric profiles. The OMCKD is also evaluated and compared with the rapid radiative transfer model for general circulation models (RRTMG) in realistic atmospheric profiles. We found that OMCKD can accurately produce heating rates and generally captures radiative forcings associated with large perturbations to the concentrations of main greenhouse gases. Furthermore, the number of pseudo-monochromatic calculations in OMCKD is 11.4% less than that in RRTMG, which indicates less computational cost.
    Language: English
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  • 3
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    A method for measuring gravitational potential on satellite’s orbit using frequency signal transfer technique between satellites (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-07-05
    Description: We proposed an approach to directly measure the gravitational potential (GP) along the orbit of a satellite, especially for the Low-Earth Orbit (LEO) satellite. The LEO satellite is connected with several Geosynchronous Equatorial Orbit (GEO) satellites through frequency signal links. Arming all the LEO and GEO satellites with precise atomic clocks, the GP difference between LEO and GEO can be measured at any time based on the gravity frequency shift approach. Supposing that the GP of GEO satellites is given, then the GP along the orbit of the LEO satellite can be determined. In this study, we conducted simulation experiments, considering the GRACE-type satellite as the LEO satellite, connected with three evenly distributed GEO satellites. The results show that the precision of the obtained GP along the orbit of the LEO satellite is mainly determined by the precision of onboard atomic clocks. If optical atomic clocks reach an instability level of 1×10〈sup〉−17〈/sup〉τ〈sup〉−1/2〈/sup〉 (τ in second), the gravitational potential along the orbit of the LEO satellite can be determined at the decimeter level with a resolution of 5'×5'. The GP information along the orbit of an LEO satellite is valuable, for it can be utilized to improve the Earth’s gravity models. This study is supported by the National Natural Science Foundation of China (NSFC) (Grant Nos. 42030105, 41721003, 42274011), and Fundamental Research Funds for the Central Universities.
    Language: English
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  • 4
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    Dark Energy Survey Year 3 Results: Deep Field optical + near-infrared images and catalogue (2021)
    Oxford University Press
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    Publication Date: 2021-10-27
    Description: We describe the Dark Energy Survey (DES) Deep Fields, a set of images and associated multi-wavelength catalogue (ugrizJHKs) built from Dark Energy Camera (DECam) and Visible and Infrared Survey Telescope for Astronomy (VISTA) data. The DES Deep Fields comprise 11 fields (10 DES supernova fields plus COSMOS), with a total area of ∼30 square degrees in ugriz bands and reaching a maximum i-band depth of 26.75 (AB, 10σ, 2″). We present a catalogue for the DES 3-year cosmology analysis of those four fields with full 8-band coverage, totalling 5.88 sq. deg. after masking. Numbering 2.8million objects (1.6million post masking), our catalogue is drawn from images coadded to consistent depths of r = 25.7, i = 25, z = 24.3 mag. We use a new model-fitting code, built upon established methods, to deblend sources and ensure consistent colours across the u-band to Ks-band wavelength range. We further detail the tight control we maintain over the point-spread function modelling required for the model fitting, astrometry and consistency of photometry between the four fields. The catalogue allows us to perform a careful star-galaxy separation and produces excellent photometric redshift performance (NMAD = 0.023 at i 〈 23). The Deep-Fields catalogue will be made available as part of the cosmology data products release, following the completion of the DES 3-year weak lensing and galaxy clustering cosmology work.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press on behalf of The Royal Astronomical Society.
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