Relation between land-climate interactions and extremes

In this post, I would like to highlight some of the recent land-climate interaction related work that was done within the CNRCWP. Through carefully designed experiments with the fifth generation Canadian Regional Climate Model (CRCM5), we identified regions with strong land-atmosphere coupling over North America for current climate. The model was able to capture these regions with strong coupling, which, as shown in previous studies (Koster et al., 2004), are located over regions where evaporation is soil moisture limited and also exhibits large variability, such as the Great Plains of the U.S. One of the interesting findings is that soil moisture can impact extreme temperature/precipitation events even over climatologically dry regions during extreme wet years and over climatologically wet regions during extreme hot years. Figure 1, for instance, clearly demonstrates that the duration of extreme precipitation events are impacted by soil moisture, over climatologically arid and semi-arid regions of North America during selected years, i.e. during wet years, when the positive precipitation anomalies are caused by large scale atmospheric features such as ENSO, leading to increased land-atmosphere coupling in these dry regions. A similar impact of soil moisture on hot-spell events is also noted over climatologically wet regions of southeast U.S. during extreme hot years. You can consult (http://onlinelibrary.wiley.com/doi/10.1002/2014JD021677/full) for more details.

Figure 1: Composites (for extreme wet years) of maximum wet-spell duration (MxDWS) from observations (left), and from CRCM5 simulations with (middle) and without (right) soil moisture – atmosphere interactions.

I will be back with another blog to share with you how soil moisture-atmosphere coupling will change in future climate and how hot-spell characteristics will be impacted by these changes.

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