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  • 1
    In: Quarterly Journal of the Royal Meteorological Society, Wiley, Vol. 143, No. 702 ( 2017-01), p. 69-100
    Kurzfassung: Large‐eddy simulations (LES) with the new ICOsahedral Non‐hydrostatic atmosphere model (ICON) covering Germany are evaluated for four days in spring 2013 using observational data from various sources. Reference simulations with the established Consortium for Small‐scale Modelling (COSMO) numerical weather prediction model and further standard LES codes are performed and used as a reference. This comprehensive evaluation approach covers multiple parameters and scales, focusing on boundary‐layer variables, clouds and precipitation. The evaluation points to the need to work on parametrizations influencing the surface energy balance, and possibly on ice cloud microphysics. The central purpose for the development and application of ICON in the LES configuration is the use of simulation results to improve the understanding of moist processes, as well as their parametrization in climate models. The evaluation thus aims at building confidence in the model's ability to simulate small‐ to mesoscale variability in turbulence, clouds and precipitation. The results are encouraging: the high‐resolution model matches the observed variability much better at small‐ to mesoscales than the coarser resolved reference model. In its highest grid resolution, the simulated turbulence profiles are realistic and column water vapour matches the observed temporal variability at short time‐scales. Despite being somewhat too large and too frequent, small cumulus clouds are well represented in comparison with satellite data, as is the shape of the cloud size spectrum. Variability of cloud water matches the satellite observations much better in ICON than in the reference model. In this sense, it is concluded that the model is fit for the purpose of using its output for parametrization development, despite the potential to improve further some important aspects of processes that are also parametrized in the high‐resolution model.
    Materialart: Online-Ressource
    ISSN: 0035-9009 , 1477-870X
    URL: Issue
    RVK:
    RVK:
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2017
    ZDB Id: 3142-2
    ZDB Id: 2089168-4
    SSG: 14
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 20, No. 9 ( 2020-05-13), p. 5657-5678
    Kurzfassung: Abstract. Clouds and aerosols contribute the largest uncertainty to current estimates and interpretations of the Earth’s changing energy budget. Here we use a new-generation large-domain large-eddy model, ICON-LEM (ICOsahedral Non-hydrostatic Large Eddy Model), to simulate the response of clouds to realistic anthropogenic perturbations in aerosols serving as cloud condensation nuclei (CCN). The novelty compared to previous studies is that (i) the LEM is run in weather prediction mode and with fully interactive land surface over a large domain and (ii) a large range of data from various sources are used for the detection and attribution. The aerosol perturbation was chosen as peak-aerosol conditions over Europe in 1985, with more than fivefold more sulfate than in 2013. Observational data from various satellite and ground-based remote sensing instruments are used, aiming at the detection and attribution of this response. The simulation was run for a selected day (2 May 2013) in which a large variety of cloud regimes was present over the selected domain of central Europe. It is first demonstrated that the aerosol fields used in the model are consistent with corresponding satellite aerosol optical depth retrievals for both 1985 (perturbed) and 2013 (reference) conditions. In comparison to retrievals from ground-based lidar for 2013, CCN profiles for the reference conditions were consistent with the observations, while the ones for the 1985 conditions were not. Similarly, the detection and attribution process was successful for droplet number concentrations: the ones simulated for the 2013 conditions were consistent with satellite as well as new ground-based lidar retrievals, while the ones for the 1985 conditions were outside the observational range. For other cloud quantities, including cloud fraction, liquid water path, cloud base altitude and cloud lifetime, the aerosol response was small compared to their natural variability. Also, large uncertainties in satellite and ground-based observations make the detection and attribution difficult for these quantities. An exception to this is the fact that at a large liquid water path value (LWP 〉 200 g m−2), the control simulation matches the observations, while the perturbed one shows an LWP which is too large. The model simulations allowed for quantifying the radiative forcing due to aerosol–cloud interactions, as well as the adjustments to this forcing. The latter were small compared to the variability and showed overall a small positive radiative effect. The overall effective radiative forcing (ERF) due to aerosol–cloud interactions (ERFaci) in the simulation was dominated thus by the Twomey effect and yielded for this day, region and aerosol perturbation −2.6 W m−2. Using general circulation models to scale this to a global-mean present-day vs. pre-industrial ERFaci yields a global ERFaci of −0.8 W m−2.
    Materialart: Online-Ressource
    ISSN: 1680-7324
    Sprache: Englisch
    Verlag: Copernicus GmbH
    Publikationsdatum: 2020
    ZDB Id: 2092549-9
    ZDB Id: 2069847-1
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 18, No. 23 ( 2018-12-11), p. 17545-17572
    Kurzfassung: Abstract. A regional modeling study on the impact of desert dust on cloud formation is presented for a major Saharan dust outbreak over Europe from 2 to 5 April 2014. The dust event coincided with an extensive and dense cirrus cloud layer, suggesting an influence of dust on atmospheric ice nucleation. Using interactive simulation with the regional dust model COSMO-MUSCAT, we investigate cloud and precipitation representation in the model and test the sensitivity of cloud parameters to dust–cloud and dust–radiation interactions of the simulated dust plume. We evaluate model results with ground-based and spaceborne remote sensing measurements of aerosol and cloud properties, as well as the in situ measurements obtained during the ML-CIRRUS aircraft campaign. A run of the model with single-moment bulk microphysics without online dust feedback considerably underestimated cirrus cloud cover over Germany in the comparison with infrared satellite imagery. This was also reflected in simulated upper-tropospheric ice water content (IWC), which accounted for only 20 % of the observed values. The interactive dust simulation with COSMO-MUSCAT, including a two-moment bulk microphysics scheme and dust–cloud as well as dust–radiation feedback, in contrast, led to significant improvements. The modeled cirrus cloud cover and IWC were by at least a factor of 2 higher in the relevant altitudes compared to the noninteractive model run. We attributed these improvements mainly to enhanced deposition freezing in response to the high mineral dust concentrations. This was corroborated further in a significant decrease in ice particle radii towards more realistic values, compared to in situ measurements from the ML-CIRRUS aircraft campaign. By testing different empirical ice nucleation parameterizations, we further demonstrate that remaining uncertainties in the ice-nucleating properties of mineral dust affect the model performance at least as significantly as including the online representation of the mineral dust distribution. Dust–radiation interactions played a secondary role for cirrus cloud formation, but contributed to a more realistic representation of precipitation by suppressing moist convection in southern Germany. In addition, a too-low specific humidity in the 7 to 10 km altitude range in the boundary conditions was identified as one of the main reasons for misrepresentation of cirrus clouds in this model study.
    Materialart: Online-Ressource
    ISSN: 1680-7324
    Sprache: Englisch
    Verlag: Copernicus GmbH
    Publikationsdatum: 2018
    ZDB Id: 2092549-9
    ZDB Id: 2069847-1
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    In: Reviews of Geophysics, American Geophysical Union (AGU), Vol. 56, No. 2 ( 2018-06), p. 409-453
    Kurzfassung: Satellite cloud droplet concentration uncertainties of 78% for pixel‐level retrievals and 54% for 1 by 1 degree retrievals are estimated The effective radius retrieval is the most important aspect for improvement, and more in situ evaluation is needed Potential improvements using passive and active satellite, and ground‐based instruments are discussed
    Materialart: Online-Ressource
    ISSN: 8755-1209 , 1944-9208
    Sprache: Englisch
    Verlag: American Geophysical Union (AGU)
    Publikationsdatum: 2018
    ZDB Id: 2035391-1
    ZDB Id: 209852-0
    ZDB Id: 209853-2
    SSG: 16,13
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    Online-Ressource
    Online-Ressource
    American Meteorological Society ; 2015
    In:  Journal of Atmospheric and Oceanic Technology Vol. 32, No. 10 ( 2015-10), p. 1813-1828
    In: Journal of Atmospheric and Oceanic Technology, American Meteorological Society, Vol. 32, No. 10 ( 2015-10), p. 1813-1828
    Kurzfassung: This paper presents an experimental analysis of the antenna system effects on polarimetric measurements conducted with cloud radars operating in the linear depolarization ratio (LDR) mode. Amplitude and phase of the copolar and cross-polar antenna patterns are presented and utilized. The patterns of two antennas of different quality were measured at the Hungriger Wolf airport near Hohenlockstedt, Germany, during the period from 28 January to 1 February 2014. For the measurements a test transmitter mounted on a tower and the scanning 35-GHz (Ka band) cloud radar MIRA-35, manufactured by METEK GmbH and operated in the receiving mode, were used. The integrated cross-polarization ratios (ICPR) are calculated for both antennas and compared with those measured in light rain. Correction algorithms for observed LDR and the co-cross-channel correlation coefficient ρ are presented. These algorithms are aimed at removing/mitigating polarization cross-coupling effects that depend on the quality of radar hardware. Thus, corrected LDR and ρ are primarily influenced by scatterer properties. The corrections are based on the decomposition of the coherency matrix of the received signals into fully polarized and nonpolarized components. The correction brings LDR values and the co-cross-channel correlation coefficients from two radars with different antenna systems to a close agreement, thus effectively removing hardware-dependent biases. Uncertainties of the correction are estimated as 3 dB for LDR in the range from −30 to −10 dB. In clouds, the correction of the co-cross-channel correlation coefficient ρ results in near-zero values for both vertically pointed radars.
    Materialart: Online-Ressource
    ISSN: 0739-0572 , 1520-0426
    Sprache: Unbekannt
    Verlag: American Meteorological Society
    Publikationsdatum: 2015
    ZDB Id: 2021720-1
    ZDB Id: 48441-6
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 102, No. 6 ( 2021-06), p. 515-522
    Materialart: Online-Ressource
    ISSN: 0003-0007 , 1520-0477
    Sprache: Unbekannt
    Verlag: American Meteorological Society
    Publikationsdatum: 2021
    ZDB Id: 2029396-3
    ZDB Id: 419957-1
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 100, No. 5 ( 2019-05), p. 841-871
    Kurzfassung: Clouds play an important role in Arctic amplification. This term represents the recently observed enhanced warming of the Arctic relative to the global increase of near-surface air temperature. However, there are still important knowledge gaps regarding the interplay between Arctic clouds and aerosol particles, and surface properties, as well as turbulent and radiative fluxes that inhibit accurate model simulations of clouds in the Arctic climate system. In an attempt to resolve this so-called Arctic cloud puzzle, two comprehensive and closely coordinated field studies were conducted: the Arctic Cloud Observations Using Airborne Measurements during Polar Day (ACLOUD) aircraft campaign and the Physical Feedbacks of Arctic Boundary Layer, Sea Ice, Cloud and Aerosol (PASCAL) ice breaker expedition. Both observational studies were performed in the framework of the German Arctic Amplification: Climate Relevant Atmospheric and Surface Processes, and Feedback Mechanisms (AC)3 project. They took place in the vicinity of Svalbard, Norway, in May and June 2017. ACLOUD and PASCAL explored four pieces of the Arctic cloud puzzle: cloud properties, aerosol impact on clouds, atmospheric radiation, and turbulent dynamical processes. The two instrumented Polar 5 and Polar 6 aircraft; the icebreaker Research Vessel (R/V) Polarstern ; an ice floe camp including an instrumented tethered balloon; and the permanent ground-based measurement station at Ny-Ålesund, Svalbard, were employed to observe Arctic low- and mid-level mixed-phase clouds and to investigate related atmospheric and surface processes. The Polar 5 aircraft served as a remote sensing observatory examining the clouds from above by downward-looking sensors; the Polar 6 aircraft operated as a flying in situ measurement laboratory sampling inside and below the clouds. Most of the collocated Polar 5/6 flights were conducted either above the R/V Polarstern or over the Ny-Ålesund station, both of which monitored the clouds from below using similar but upward-looking remote sensing techniques as the Polar 5 aircraft. Several of the flights were carried out underneath collocated satellite tracks. The paper motivates the scientific objectives of the ACLOUD/PASCAL observations and describes the measured quantities, retrieved parameters, and the applied complementary instrumentation. Furthermore, it discusses selected measurement results and poses critical research questions to be answered in future papers analyzing the data from the two field campaigns.
    Materialart: Online-Ressource
    ISSN: 0003-0007 , 1520-0477
    Sprache: Unbekannt
    Verlag: American Meteorological Society
    Publikationsdatum: 2019
    ZDB Id: 2029396-3
    ZDB Id: 419957-1
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 8
    Online-Ressource
    Online-Ressource
    Springer Science and Business Media LLC ; 2019
    In:  npj Climate and Atmospheric Science Vol. 2, No. 1 ( 2019-10-14)
    In: npj Climate and Atmospheric Science, Springer Science and Business Media LLC, Vol. 2, No. 1 ( 2019-10-14)
    Kurzfassung: The relationship between vertical air velocity at cloud base and primary ice formation has been measured for shallow mixed-phase cloud layers (thickness 〈 380 m) by means of ground-based cloud radar and Doppler lidar. For layers with a cloud-top temperature below −12 °C, an increase of vertical-velocity standard deviation from 0.1 to 1.0 m s −1 leads to an increase in the mass flux of ice water by two orders of magnitude. The cloud layers under study were selected in such a way that secondary ice-formation processes played a minor role, and primary ice formation was the dominant source of ice formation. Phenomenological parameterizations of the ice mass and the ice mass flux as functions of standard deviation of vertical air velocity are given.
    Materialart: Online-Ressource
    ISSN: 2397-3722
    Sprache: Englisch
    Verlag: Springer Science and Business Media LLC
    Publikationsdatum: 2019
    ZDB Id: 2925628-8
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 9
    Online-Ressource
    Online-Ressource
    American Geophysical Union (AGU) ; 2007
    In:  Journal of Geophysical Research Vol. 112, No. D6 ( 2007-03-16)
    In: Journal of Geophysical Research, American Geophysical Union (AGU), Vol. 112, No. D6 ( 2007-03-16)
    Materialart: Online-Ressource
    ISSN: 0148-0227
    Sprache: Englisch
    Verlag: American Geophysical Union (AGU)
    Publikationsdatum: 2007
    ZDB Id: 2033040-6
    ZDB Id: 3094104-0
    ZDB Id: 2130824-X
    ZDB Id: 2016813-5
    ZDB Id: 2016810-X
    ZDB Id: 2403298-0
    ZDB Id: 2016800-7
    ZDB Id: 161666-3
    ZDB Id: 161667-5
    ZDB Id: 2969341-X
    ZDB Id: 161665-1
    ZDB Id: 3094268-8
    ZDB Id: 710256-2
    ZDB Id: 2016804-4
    ZDB Id: 3094181-7
    ZDB Id: 3094219-6
    ZDB Id: 3094167-2
    ZDB Id: 2220777-6
    ZDB Id: 3094197-0
    SSG: 16,13
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 10
    In: The EMBO Journal, EMBO, Vol. 34, No. 3 ( 2015-02-03), p. 379-392
    Materialart: Online-Ressource
    ISSN: 0261-4189 , 1460-2075
    RVK:
    Sprache: Englisch
    Verlag: EMBO
    Publikationsdatum: 2015
    ZDB Id: 1467419-1
    ZDB Id: 586044-1
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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