A seamless weather–climate multi‐model intercomparison on the representation of a high impact weather event in the western Mediterranean: HyMeX IOP12

Abstract

High Impact Weather (HIW), particularly Heavy Precipitation Events (HPE), are common phenomena affecting the western Mediterranean (WMED) especially in the autumn period. Understanding and evaluating the capability to adequately represent such events in model simulations is one of the main goals of the Hydrological cycle in the Mediterranean Experiment (HyMeX) and the main motivation of this investigation. In order to gain a better knowledge of the model representation of HPE and related processes we perform a seamless multi‐model intercomparison at the event scale. Limited‐area model runs (grid spacing from 2 to 20 km) at weather and climate time‐scales are considered, four with parametrized and five with explicit convection. The performance of the nine models is compared by analysing precipitation, as well as convection‐relevant parameters. An Intensive Observation Period (IOP12) from the HyMeX‐SOP1 (Special Observation Period) is used to illustrate the results. During IOP12, HPE affected the northwestern Mediterranean region, from Spain to Italy, as a consequence of Mesoscale Convective Systems (MCSs) which initiated and intensified in the area of investigation. Results show that: (i) the timing of the maximum precipitation seems to be linked to the representation of large‐scale conditions rather than differences among models; (ii) Convection Permitting Models (CPMs) exhibit differences among each other, but better represent the short‐intense convective events. All four convection‐parametrized models produce a large number of weak and long‐lasting events. Regional Climate Models (RCMs) capture the occurrence of the event but produce notably lower precipitation amounts and hourly intensities than CPMs and Numerical Weather Prediction (NWP) models with parametrized convection; (iii) these differences do not seem to come from mean moisture or Convective Available Potential Energy (CAPE) which are in the same range for all models, but rather from differences in the variability and vertical distribution of moisture and the triggering of deep convection.

Scaling of precipitation extremes with temperature in the French Mediterranean region: What explains the hook shape?

“…The consequence of spatial averaging effect is consistent with Chen and Knutson [] and Khodayar et al [] and is illustrated in Figures a and d which displays the curve drawn from the in situ measurements corrected using the ensemble mean ratio of spatially averaged to local precipitation extremes of Figure . The magenta and green curves mimic the expected SAFRAN and WRF scaling, respectively.…”

Extreme rainfall in Mediterranean France during the fall: added value of the CNRM-AROME Convection-Permitting Regional Climate Model

“…Concerning the role of model resolution in regards to the representation of hpes, studies by Déqué and Somot (2008), Torma et al (2015), Fantini et al (2018), Ruti et al (2016) and Prein et al (2016) proved the added value of a horizontal resolution of 12.5 km rcms (Regional Climate Model) with respect to a horizontal resolution of 50 km rcms. In Richard et al (2007) and Khodayar et al (2016), the authors showed that by using a set of explicit convection models at a horizontal resolution of 2 km, the simulated extreme precipitation for some hpe cases was closer to the observations than were the hydrostatic models with a coarser resolution. Berthou et al (2018) showed that when it came to daily precipitation, at a resolution of 12.5 km, two rcms behaved differently concerning the representation of high precipitation events in the Gard in September 2002 whereas their Convective Permitting Regional Climate Model (cprcms) counterpart converged for a better representation.…”

Multi‐scale observations of atmospheric moisture variability in relation to heavy precipitating systems in the northwestern Mediterranean during HyMeX IOP12

“…Although the relevance of the vertical distribution of moisture and related changes for the occurrence of HPSs was already pointed out in the region in Khodayar et al . (), the relationship with the severity of the event and the build‐up time has not been previously discussed. Therefore, further analysis regarding these characteristics will be necessary to assess the generality of our results.…”

“…This study focuses on a complex single IOP; therefore, it would be of interest to extend the investigation to a large number of events, including other types of convective situations. Although the relevance of the vertical distribution of moisture and related changes for the occurrence of HPSs was already pointed out in the region in Khodayar et al (2016a), the relationship with the severity of the event and the build-up time has not been previously discussed. Therefore, further analysis regarding these characteristics will be necessary to assess the generality of our results.…”