• Land–atmosphere feedbacks and dry extremes
    under changing climate

    November 20th–22nd 2019

    Ghent | Belgium

  • Context

     

    In the face of climate change, general dryness and wetness conditions are expected to be modified in many parts of the world, and with them, also the dry and wet extreme event occurrence. In particular, dry extremes, such as long-term droughts and shorter dry spells, have a great and immediate effect on humans and environment, causing significant life and economical losses on annual basis.

     

    Climate models and existing observational records have already reported an ongoing increase in duration and severity of dry events in some regions of the world, and largely agree on their further exacerbation in the future, albeit with large degree of uncertainty. More devastating impacts on population and environment are therefore expected.

     

    The existing uncertainties about the role of local land–atmosphere feedbacks in the dynamics and long-term variability of dry events hamper the accurate forecasting and projection of these meteorological extremes.

     

    This workshop aims at reconciling ongoing scientific efforts directed to enhance our understanding of land–atmosphere interactions and their effect on droughts, dry spells and drying trends. A coherent synthesis of existing knowledge from two virtually distinct communities is intended: experts working on land-atmosphere feedbacks and dry extremes at boundary layer scales, and climate modellers working on the effect of land surface on long-term climate projections.

  • Research Questions

    The workshop will bring together experts working on land-atmosphere feedbacks and dry extremes at boundary layer scales and climate model scales to gain more insight into the two following research questions:

     

    Q1What is the effect of local and remote land-atmosphere feedbacks on the onset, evolution and termination of droughts and dry spells?

     

    Q2 How does this contribution of land–atmosphere feedbacks vary as climate changes and to what degree it explains drying trends?

    Current understanding of the physical factors influencing development of abnormally dry conditions suggests the key role of large-scale circulation features. However, an increasing number of studies show that land surface state and its immediate interaction with the atmosphere can play an important and direct role in the evolution of dry events locally or even remotely. In the former case, as soil dries out, less evaporation enters the atmosphere accelerating drying process even more. One consequence of that is the amplification of dryness conditions. Another, is a change in the local and remote land surface feedbacks on the boundary layer and, hence a change of the probability to form convection and precipitation locally. Little evidence exists on the relevance of land–atmosphere feedbacks on precipitation changes during droughts and dry spells.

    The second main aspect that will be considered in the workshop is the role of the land–atmosphere feedbacks in the observed and modelled positive global dryness trends. The simulations of climate models almost unanimously suggest a key role of soil moisture reduction in the strengthening of the dryness conditions with time via land–atmosphere interactions. However, the exact mechanisms underlying this relationship remain unclear. The effect of modified precipitation triggering via change of the local land–atmosphere feedbacks on boundary layer is suggested as one of the potential reasons but it has yet to be explored. As part of this problem, the lack of a direct collaboration between climate modelling community and the research carried out at boundary layer and daily scales further complicates the solution of the above problem.

  • Discussion Topics

    1. – Boundary layer dynamics during dry extreme events, with special emphasis on soil moisture feedbacks

     

    2. – Methods for disentangling large-scale climate forcing from land–atmospheric feedbacks

     

    3. – Global climatological trends in soil and atmospheric dryness and their relation to land surface feedbacks

     

    4. – Observation, modelling and interpretation of temporal dynamics and trends in land–atmosphere coupling, including novel metrics

     

    5. – Dry extremes links to monsoonal circulation and atmospheric moisture sources

  • Contact

    Irina Petrova

    Diego Miralles