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search.filters.applied.f.access: openAccess × Type: Text × Subject: advection × WGL Institute: PIK ×

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Now showing 1 - 3 of 3
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    A critical humidity threshold for monsoon transitions
    (München : European Geopyhsical Union, 2012) Schewe, J.; Levermann, A.; Cheng, H.
    Monsoon systems around the world are governed by the so-called moisture-advection feedback. Here we show that, in a minimal conceptual model, this feedback implies a critical threshold with respect to the atmospheric specific humidity qo over the ocean adjacent to the monsoon region. If qo falls short of this critical value qoc, monsoon rainfall over land cannot be sustained. Such a case could occur if evaporation from the ocean was reduced, e.g. due to low sea surface temperatures. Within the restrictions of the conceptual model, we estimate qoc from present-day reanalysis data for four major monsoon systems, and demonstrate how this concept can help understand abrupt variations in monsoon strength on orbital timescales as found in proxy records.
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    Correlation networks from flows. The case of forced and time-dependent advection-diffusion dynamics
    (San Francisco, CA : Public Library of Science (PLoS), 2016) Tupikina, L.; Molkenthin, N.; López, C.; Hernández-García, E.; Marwan, N.; Kurths, J.
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    On statistics of the free-troposphere synoptic component: An evaluation of skewnesses and mixed third-order moments contribution to the synoptic-scale dynamics and fluxes of heat and humidity
    (Abingdon : Taylor and Francis Ltd., 2008) Petoukhov, V.; Eliseev, A.V.; Klein, R.; Oesterle, H.
    Based on the ERA40 data for 1976-2002 we calculated skewnesses and mixed third-order statistical moments (TOMs) for the synoptic variations [with (2.5-6) d timescales]of horizontal winds, temperature, vertical velocity and the specific humidity in Eulerian coordinates. All these variables show skewnesses which markedly deviate from zero, basically at the entries and the outlets of the mid-latitude storm tracks. In these regions, high values of skewness for vertical velocity, temperature and the specific humidity are revealed throughout the entire free troposphere, while the marked skewnesses for horizontal winds are traced in the lower free troposphere. We found a notable deviation of the synoptic-component statistics from the Gaussian statistics. We also made an estimate of the contribution from TOMs to the prognostic equations for the synoptic-scale kinetic energy and the meridional fluxes of sensible and latent heat, which appeared to be non-negligible, mainly in the storm tracks in winter. Our analysis attests that the most pronounced contribution of TOMs to the aforementioned equations comes from the self-advection by the horizontal synoptic-scale motions, while the TOMs induced by the metric terms in the original equations, and specifically the TOMs associated with the vertical self-advection by the synoptic-scale motions, are much less important.