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  • American Meteorological Society  (32)
  • 1
    Online Resource
    Online Resource
    The Dynamical Tropopause Location as a Potential Predictor for North Atlantic Tropical Cyclone Activity
    American Meteorological Society ; 2023
    In:  Journal of Climate Vol. 36, No. 8 ( 2023-04-15), p. 2515-2533
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 36, No. 8 ( 2023-04-15), p. 2515-2533
    Abstract: Tropical cyclones are among the most devastating natural phenomena that can cause severe damage when undergoing landfall. In the wake of the poorly forecast 2013 North Atlantic hurricane season, Rossby wave breaking on the 350-K isentropic surface has been linked to tropical cyclone activity measured by the accumulated cyclone energy (ACE). Here, ERA5 data and HURDAT2 tropical cyclone data are used to argue that the latitude of the 2 potential vorticity unit (PVU; 1 PVU = 10 −6 K kg −1 m 2 s −1 ) contour on the 360-K isentropic surface in the western North Atlantic is linked to changes in vertical wind shear and relative humidity during the month of September. A more equatorward position of the 2-PVU contour is shown to be linked to an increase in vertical wind shear and a reduction in relative humidity, as manifested in an increased ventilation index, in the tropical western North Atlantic during September. The more equatorward position is further linked to a reduction in the number of named storms, storm and hurricane days, hurricane lifetime, and number of tropical cyclones making landfall. Changes in genesis location are shown to be of importance for the changes in landfall frequency and hurricane lifetime. In summary, the 2-PVU contour latitude in the western North Atlantic can, therefore, potentially be used as a predictor in seasonal and subseasonal forecasting. Significance Statement Forecasts for the North Atlantic hurricane season are operationally produced. Their aim is to predict the number of tropical cyclones and their total energy throughout the season. This study proposes to include the tropopause latitude in these forecasts, as it is shown to be linked to vertical wind shear and midtropospheric relative humidity in the western tropical North Atlantic. The tropopause latitude is thereby linked to the number of tropical cyclones, their lifetime, and the total energy throughout the season. This link is particularly strong during September.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-22-0479.1
    RVK:
    UA 4548
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2023
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 2
    Online Resource
    Online Resource
    GCM Aerosol Radiative Effects Using Geographically Varying Aerosol Sizes Deduced from AERONET Measurements
    American Meteorological Society ; 2003
    In:  Journal of the Atmospheric Sciences Vol. 60, No. 22 ( 2003-11), p. 2747-2764
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 60, No. 22 ( 2003-11), p. 2747-2764
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    URL: Article
    DOI: 10.1175/1520-0469(2003)060〈2747:GAREUG〉2.0.CO;2
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2003
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 3
    Online Resource
    Online Resource
    Formation and Development of Orographic Mixed-Phase Clouds
    American Meteorological Society ; 2017
    In:  Journal of the Atmospheric Sciences Vol. 74, No. 11 ( 2017-11-01), p. 3703-3724
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 74, No. 11 ( 2017-11-01), p. 3703-3724
    Abstract: Orographic forcing can stabilize mixed-phase clouds (MPCs), which are thermodynamically unstable owing to the different saturation vapor pressure over liquid water and ice. This study presents simulations of MPCs in orographically complex terrain over the Alpine ridge with the regional model COSMO using a horizontal resolution of 1 km. Two case studies provide insights into the formation of Alpine MPCs. Trajectory studies show that the majority of the air parcels lifted by more than 600 m are predominantly in the liquid phase even if they originate from glaciated clouds. The interplay between lifted and advected air parcels is crucial for the occurrence of MPCs. Within a sensitivity study, the orography is reduced to 80%, which changed both the total barrier height and steepness. The changes in total water path (TWP), liquid water path (LWP), and ice water path (IWP) vary in sign and strength as the affected precipitation does. LWP can experience changes up to 500% resulting in a transformation from an ice-dominated MPC to a liquid-dominated MPC. In further simulations with increased steepness and maintained surface height at Jungfraujoch, TWP experiences a reduction between 25% and 40% during different time periods, which results in reduced precipitation by around 30%. An accurate representation of the steepness and the height of mountains in models is crucial for the formation and development of MPCs.
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    URL: Article
    DOI: 10.1175/JAS-D-16-0348.1
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2017
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 4
    Online Resource
    Online Resource
    A Comparison of Model- and Satellite-Derived Aerosol Optical Depth and Reflectivity
    American Meteorological Society ; 2002
    In:  Journal of the Atmospheric Sciences Vol. 59, No. 3 ( 2002-02), p. 441-460
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 59, No. 3 ( 2002-02), p. 441-460
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    URL: Article
    DOI: 10.1175/1520-0469(2002)059〈0441:ACOMAS〉2.0.CO;2
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2002
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 5
    Online Resource
    Online Resource
    Nonlinear Aspects of the Climate Response to Greenhouse Gas and Aerosol Forcing
    American Meteorological Society ; 2004
    In:  Journal of Climate Vol. 17, No. 12 ( 2004-06), p. 2384-2398
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 17, No. 12 ( 2004-06), p. 2384-2398
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/1520-0442(2004)017〈2384:NAOTCR〉2.0.CO;2
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2004
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 6
    Online Resource
    Online Resource
    Contribution of Changes in Sea Surface Temperature and Aerosol Loading to the Decreasing Precipitation Trend in Southern China
    American Meteorological Society ; 2005
    In:  Journal of Climate Vol. 18, No. 9 ( 2005-05-01), p. 1381-1390
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 18, No. 9 ( 2005-05-01), p. 1381-1390
    Abstract: The effects of increasing sea surface temperature (SST) and aerosol loading in a drought region in Southern China are studied using aerosol optical depth (AOD), low-level cloud cover (LCC), visibility, and precipitation from observed surface data; wind, temperature, specific humidity, and geopotential height from the NCEP–NCAR reanalysis fields; and SST from the NOAA archive data. The results show a warming of the SST in the South China Sea and the Indian Ocean, and a strengthening of the West Pacific Subtropical High (WPSH) in the early summer during the last 40 yr, with the high pressure system extending farther westward over the continent in Southern China. Because the early summer average temperature contrast between the land and ocean decreased, the southwesterly monsoon from the ocean onto mainland China weakened and a surface horizontal wind divergence anomaly occurred over Southern China stabilizing the boundary layer. Thus, less moisture was transported to Southern China, causing a drying trend. Despite this, surface observations show that AOD and LCC have increased, while visibility has decreased. Precipitation has decreased in this region in the early summer, consistent with both the second aerosol indirect effect (reduction in precipitation efficiency caused by the more numerous and smaller cloud droplets) and dynamically induced changes from convective to more stratiform clouds. The second aerosol indirect effect and increases in SST and greenhouse gases (GHG) were simulated separately with the ECHAM4 general circulation model (GCM). The GCM results suggest that both effects contribute to the changes in LCC and precipitation in the drought region in Southern China. The flooding trend in Eastern China, however, is more likely caused by strengthened convective precipitation associated with increases in SST and GHG.
    Type of Medium: Online Resource
    ISSN: 1520-0442 , 0894-8755
    URL: Article
    DOI: 10.1175/JCLI3341.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2005
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 7
    Online Resource
    Online Resource
    Possible Aerosol Effects on Ice Clouds via Contact Nucleation
    American Meteorological Society ; 2002
    In:  Journal of the Atmospheric Sciences Vol. 59, No. 3 ( 2002-02), p. 647-656
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 59, No. 3 ( 2002-02), p. 647-656
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    URL: Article
    DOI: 10.1175/1520-0469(2001)059〈0647:PAEOIC〉2.0.CO;2
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2002
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 8
    Online Resource
    Online Resource
    The Impact of Warm and Moist Airmass Perturbations on Arctic Mixed-Phase Stratocumulus
    American Meteorological Society ; 2020
    In:  Journal of Climate Vol. 33, No. 22 ( 2020-11-15), p. 9615-9628
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 33, No. 22 ( 2020-11-15), p. 9615-9628
    Abstract: The Arctic is known to be particularly sensitive to climate change. This Arctic amplification has partially been attributed to poleward atmospheric heat transport in the form of airmass intrusions. Locally, such airmass intrusions can introduce moisture and temperature perturbations. The effect of airmass perturbations on boundary layer and cloud changes and their impact on the surface radiative balance has received increased attention, especially over sea ice with regard to sea ice melt. Utilizing cloud-resolving model simulations, this study addresses the impact of airmass perturbations occurring at different altitudes on stratocumulus clouds for open-ocean conditions. It is shown that warm and moist airmass perturbations substantially affect the boundary layer and cloud properties, even for the relatively moist environmental conditions over the open ocean. The cloud response is driven by temperature inversion adjustments and strongly depends on the perturbation height. Boundary layer perturbations weaken and raise the inversion, which destabilizes the lower troposphere and involves a transition from stratocumulus to cumulus clouds. In contrast, perturbations occurring in the lower free troposphere lead to a lowering but strengthening of the temperature inversion, with no impact on cloud fraction. In simulations where free-tropospheric specific humidity is further increased, multilayer mixed-phase clouds form. Regarding energy balance changes, substantial surface longwave cooling arises out of the stratocumulus break-up simulated for boundary layer perturbations. Meanwhile, the net surface longwave warming increases resulting from thicker clouds for airmass perturbations occurring in the lower free troposphere.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-20-0163.1
    RVK:
    UA 4548
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 9
    Online Resource
    Online Resource
    Precipitation Susceptibility and Aerosol Buffering of Warm- and Mixed-Phase Orographic Clouds in Idealized Simulations
    American Meteorological Society ; 2018
    In:  Journal of the Atmospheric Sciences Vol. 75, No. 4 ( 2018-04-01), p. 1173-1194
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 75, No. 4 ( 2018-04-01), p. 1173-1194
    Abstract: The sensitivity of warm- and mixed-phase orographic precipitation to the aerosol background with simultaneous changes in the abundance of cloud condensation nuclei and ice nucleating particles is explored in an idealized, two-dimensional modeling study. The concept of precipitation susceptibility dlnP/dlnN, where P is the precipitation mixing ratio and N the cloud droplet number, is adapted for orographic clouds. Precipitation susceptibility is found to be low because perturbations to different precipitation formation pathways compensate each other. For mixed-phase conditions, this in particular means a redistribution between warm and cold pathways. The compensating behavior is described as a consequence of a balance equation for the cloud water along parcel trajectories that constrains the total precipitation formation to match the drying from condensation and vapor deposition on ice-phase hydrometeors caused by the mountain flow. For an aerosol-independent condensation rate (saturation adjustment), this balance requirement limits aerosol impacts on orographic precipitation (i) to the evaporation of hydrometeors and (ii) to the glaciation state of the cloud, which controls the contribution of vapor deposition to drying. The redistribution of precipitation formation pathways is coupled to a redistribution of the total hydrometeor mass between hydrometeor categories. Aerosol effects on the glaciation state of the cloud enhance this redistribution effect such that liquid and ice adjustments do not compensate. For the externally constrained, fully adjusted steady-state situation studied, precipitation susceptibility quantifies the redistribution effect rather than changes in precipitation production as in previous studies.
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    URL: Article
    DOI: 10.1175/JAS-D-17-0254.1
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2018
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 10
    Online Resource
    Online Resource
    Sensitivity Studies of the Role of Aerosols in Warm-Phase Orographic Precipitation in Different Dynamical Flow Regimes
    American Meteorological Society ; 2008
    In:  Journal of the Atmospheric Sciences Vol. 65, No. 8 ( 2008-08-01), p. 2522-2542
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 65, No. 8 ( 2008-08-01), p. 2522-2542
    Abstract: Aerosols serve as a source of cloud condensation nuclei (CCN) and influence the microphysical properties of clouds. In the case of orographic clouds, it is suspected that aerosol–cloud interactions reduce the amount of precipitation on the upslope side of the mountain and enhance the precipitation on the downslope side when the number of aerosols is increased. The net effect may lead to a shift of the precipitation distribution toward the leeward side of mountain ranges, which affects the hydrological cycle on the local scale. In this study aerosol–cloud interactions in warm-phase clouds and the possible impact on the orographic precipitation distribution are investigated. Herein, simulations of moist orographic flow over topography are conducted and the influence of anthropogenic aerosols on the orographic precipitation formation is analyzed. The degree of aerosol pollution is prescribed by different aerosol spectra that are representative for central Switzerland. The simulations are performed with the Consortium for Small-Scale Modeling’s mesoscale nonhydrostatic limited-area weather prediction model (COSMO) with a horizontal grid spacing of 2 km and a fully coupled aerosol–cloud parameterization. It is found that an increase in the aerosol load leads to a downstream shift of the orographic precipitation distribution and to an increase in the spillover factor. A reduction of warm-phase orographic precipitation is observed at the upslope side of the mountain. The downslope precipitation enhancement depends critically on the width of the mountain and on the flow dynamics. In the case of orographic precipitation induced by stably stratified unblocked flow, the loss in upslope precipitation is not compensated by leeward precipitation enhancement. In contrast, flow blocking may lead to leeward precipitation enhancement and eventually to a compensation of the upslope precipitation loss. The simulations also indicate that latent heat effects induced by aerosol–cloud–precipitation interactions may considerably affect the orographic flow dynamics and consequently feed back on the orographic precipitation development.
    Type of Medium: Online Resource
    ISSN: 1520-0469 , 0022-4928
    URL: Article
    DOI: 10.1175/2007JAS2492.1
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2008
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
    Location Call Number Limitation Availability
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