Editing IPCC:AR6/WGI/Chapter-11 (section)

==== 11.7.3.3 Model Evaluation ====

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The explicit representation of severe convective storms requires non-hydrostatic models with horizontal grid spacings finer than 4 km, denoted as convection-permitting models or storm-resolving models ( [[IPCC:Wg1:Chapter:Chapter-10#10.3.1|Section 10.3.1]] ). Convection-permitting models are becoming available to run over a wide domain, such as a continental scale or even over the global area, and show realistic climatological characteristics of MCSs ( [[#Prein--2015|Prein et al., 2015]] ; [[#Guichard--2017|Guichard and Couvreux, 2017]] ; [[#Satoh--2019|Satoh et al., 2019]] ). Such high-resolution simulations are computationally too expensive to perform at the larger domain and for long periods, and alternative methods by using an RCM with dynamical downscaling are generally used ( [[IPCC:Wg1:Chapter:Chapter-10#10.3.1|Section 10.3.1]] ). Convection-permitting models are used as the flagship project of CORDEX to particularly study projections of thunderstorms ( [[IPCC:Wg1:Chapter:Chapter-10#10.3.3|Section 10.3.3]] ). Simulations of North American MCSs by a convection-permitting model conducted by [[#Prein--2020|Prein et al. (2020)]] were able to capture the main characteristics of the observed MCSs, such as their size, precipitation rate, propagation speed, and lifetime. Cloud-permitting model simulations in Europe also showed sub-daily precipitation realistically ( [[#Ban--2014|Ban et al., 2014]] ; [[#Kendon--2014|Kendon et al., 2014]] ). Evaluation of precipitation conducted using convection-permitting simulations around Japan showed that finer resolution improves intense precipitation ( [[#Murata--2017|Murata et al., 2017]] ). MCSs over Africa simulated using convection-permitting models showed better extreme rainfall ( [[#Kendon--2019|Kendon et al., 2019]] ) and diurnal cycles and convective rainfall over land than the coarser-resolution RCMs or GCMs ( [[#Stratton--2018|Stratton et al., 2018]] ; [[#Crook--2019|Crook et al., 2019]] ).

The other modelling approach is the analysis of the environmental conditions that control characteristics of severe convective storms using the typical climate model results in CMIP5/6 ( [[#Allen--2018|Allen, 2018]] ). Severe convective storms are generally formed in environments with large CAPE and tornadic storms are, in particular, formed with a combination of large CAPE and strong vertical wind shear. As the processes associated with severe convective storms occur over a wide range of spatial and temporal scales, some of which are poorly understood and are inadequately sampled by observational networks, the model calibration approaches are generally difficult and insufficiently validated. Therefore, model simulations and their interpretations should be done with much caution.

In summary, there are typically two kinds of modelling approaches for studying changes in severe convective storms. One is to use convection-permitting models in wider regions or the global domain in time-sliced downscaling methods to directly simulate severe convective storms. The other is the analysis of the environmental conditions that control characteristics of severe convective storms by using coarse-resolution GCMs. Even in finer-resolution convection-permitting models, it is difficult to directly simulate tornadoes, hail storms, and lightning, so modelling studies of these changes are limited.

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