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  • 2020-2024  (5)
  • 1
    Keywords: Forschungsbericht
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (70 Seiten, 6,68 MB) , Illustrationen, Diagramme
    Language: German
    Note: Förderkennzeichen BMWi 03ET6095A-E , Verbundnummer 01169189 , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden
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  • 2
    Publication Date: 2023-06-06
    Description: Dusty cirrus clouds are extended optically thick cirrocumulus decks that occur during strong mineral dust events. So far, they have been mostly documented over Europe associated with dust-infused baroclinic storms. Since today's global operational numerical weather prediction models neither predict mineral dust distributions nor consider the interaction of dust with cloud microphysics, they cannot simulate this phenomenon. We have performed ICON-ART limited-area simulations with 2 km grid spacing to understand and predict the formation of dusty cirrus clouds. Based on these simulations, we postulate that the dusty cirrus forms through a mixing instability of moist clean air with drier dusty air. A corresponding sub-grid parameterization is suggested and tested in the ICON-ART model. Only with help of this special sub-grid parameterization ICON-ART is able to simulate the formation of the dusty cirrus, which leads to substantial improvements in cloud cover and radiative fluxes compared to simulations without this parameterization. A statistical evaluation over six Saharan dust events with and without observed dusty cirrus shows robust improvements in cloud and radiation scores. The ability to simulate dusty cirrus formation removes the linear dependency on mineral dust aerosol optical depth from the bias of the radiative fluxes. This suggests that the formation of dusty cirrus clouds is the dominant aerosol-cloud-radiation effect of mineral dust over Europe. At the IUGG we will present first simulations with the dusty cirrus parameterization in the global ICON-ART model and discuss the occurrence of dusty cirrus in Asia.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 3
    Publication Date: 2023-06-06
    Description: For efficient planning and integration of photovoltaic power plants into the power grids, better knowledge of the aerosol-cloud-radiation interaction and more accurate radiation forecasts are needed. However, most operational numerical weather prediction models rely on an aerosol climatology and ignore the spatio-temporal variability of the atmospheric aerosol. In special weather conditions like Saharan dust outbreaks or extended wildfires, this leads to significant deficiencies in the operational forecasts. At Deutscher Wetter­dienst (DWD) and Karlsruhe Institute of Technology (KIT) the project "PermaStrom" aims to improve radiation forecasts. Using the ICON-ART modeling system the emission, transport, and deposition of mineral dust, black carbon from vegetation fires, and sea salt are explicitly simulated. To achieve the project goals and to examine in detail, the effect of Saharan dust on solar radiation, accurate and extensive measurements of the Saharan dust in the atmosphere and of the ground reaching solar radiation is needed. In our presentation, we will show results for several strong dust episodes in Germany. Dust clouds transported from the Saharan region to Germany are detected and tracked using ceilometer, spectroscopic and broadband radiation measurements from several sites within the measurement network of the DWD. We will focus on the direct and indirect aerosol effects and how these affect the solar irradiance at the ground. Furthermore, we will show how the implementation of prognostic mineral dust in the ICON-ART NWP model can improve the radiation forecasts during such events.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 4
    Publication Date: 2023-10-02
    Description: Tropospheric water vapor is one of the most important trace gases of the Earth's climate system, and its temporal and spatial distribution is critical for the genesis of clouds and precipitation. Due to the pronounced dynamics of the atmosphere and the nonlinear relation of air temperature and saturated vapor pressure, it is highly variable, which hampers the development of high-resolution and three-dimensional maps of regional extent. With their complementary high temporal and spatial resolutions, Global Navigation Satellite Systems (GNSS) meteorology and Interferometric Synthetic Aperture Radar (InSAR) satellite remote sensing represent a significant alternative to generally sparsely distributed radio sounding observations. In addition, data fusion with collocation and tomographical methods enables the construction of detailed maps in either two or three dimensions. Finally, by assimilation of these observation-derived datasets with dynamical regional atmospheric models, tropospheric water vapor fields can be determined with high spatial and continuous temporal resolution. In the following, a collection of basic and processed datasets, obtained with the above-listed methods, is presented that describes the state and course of atmospheric water vapor for the extent of the GNSS Upper Rhine Graben Network (GURN) region. The dataset contains hourly 2D fields of integrated water vapor (IWV) and 3D fields of water vapor density (WVD) for four multi-week, variable season periods between April 2016 and October 2018 at a spatial resolution of (2.1 km)2. Zenith total delay (ZTD) from GNSS and collocation and refractivities are provided as intermediate products. InSAR (Sentinel-1A/B)-derived double differential slant total delay phases (ddSTDPs) and GNSS-based ZTDs are available for March 2015 to July 2019. The validation of data assimilation with five independent GNSS stations for IWV shows improving Kling–Gupta efficiency (KGE) scores for all seasons, most notably for summer, with collocation data assimilation (KGE = 0.92) versus the open-cycle simulation (KGE = 0.69). The full dataset can be obtained from https://doi.org/10.1594/PANGAEA.936447 (Fersch et al., 2021).
    Language: English
    Type: info:eu-repo/semantics/article
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  • 5
    Publication Date: 2023-10-02
    Description: The assimilation of observations in limited area models (LAMs) allows to find the best possible estimate of a region’s meteorological state. Water vapor is a crucial constituent in terms of cloud and precipitation formation. Its highly variable nature in space and time is often insufficiently represented in models. This study investigates the improvement of simulated water vapor content within the Weather Research and Forecasting model (WRF) in every season by assimilating temperature, relative humidity, and surface pressure obtained from climate stations, as well as geodetically derived Zenith Total Delay (ZTD) and precipitable water vapor (PWV) data from global navigation satellite system (GNSS) ground stations. In four case studies we analyze the results of high-resolution convection-resolving WRF simulations (2.1 km) between 2016 and 2018 each in every season for a 650 × 670 km domain in the tri-border-area Germany, France and Switzerland. The impact of 3D VAR assimilation of different variables and combinations thereof, background error option, as well as the temporal and spatial resolution of assimilation is evaluated. Both column values and profiles derived from radiosondes are addressed. Best outcome was achieved when assimilating ZTD and synoptic data at an hourly resolution and a spatial thinning distance of 10 km. It is concluded that the careful selection of assimilation options can additionally improve simulation results in every season. Clear effects of assimilation on the water budgets can also be seen.
    Language: English
    Type: info:eu-repo/semantics/article
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