4MESO Identifying Mesoscale Convective Systems and Extreme Precipitation Associated in Northeastern North America with the Canadian Regional Climate Model (CRCM6).

Extreme precipitation events are primarily associated with large-scale and mesoscale meteorological phenomena, including mesoscale convective storms (MCS). The introduction of convection-permitting models (CPMs), which operate at high spatial resolution and do not require parameterization schemes, has led to a more realistic representation of the atmospheric processes involved in mesoscale phenomena. This study provides a detailed climatological analysis of MCS and associated extreme precipitation events in the northeastern region of North America during the period 2015-2021. We employ a tracking algorithm to identify and characterize MCS using Canadian Regional Climate Model, version 6 (CRCM6) simulations at 12 km and 2.5 km grid spacing, along with ERA5 reanalysis data, IMERG and MERGIR satellite data, and Nexrad STAGE IV radar observations. The temporal distribution analysis shows a higher frequency of MCS events during the spring and summer months, typically starting in the early afternoon. Our results indicate that lower resolution products, including CRCM6-12km and ERA5, do not fully reproduce MCS or their multiannual distribution compared to satellite data and radar observations. In contrast, the high-resolution CRCM6-2.5km model tends to identify MCS with slightly smaller areas but higher total and maximum precipitation rates, longer lifetimes, and greater track distances. Despite differences in the number of MCS identified between the models, there is agreement in the representation of certain characteristics such as size and precipitation intensity. The diurnal cycle analysis shows that MCS sizes peak in the late afternoon and early morning, while maximum precipitation occurs about 17 hours, with the CRCM6-2.5km model showing a slight overestimation compared to radar observations. Notably, MCSs in the study region exhibit rapid intensification within the first few hours after initiation, particularly for events lasting less than 10 hours, which reach their peak intensity between the 3rd and 6th hours. The CRCM6-2.5km model has shown an improved ability to represent convection processes associated with MCS at finer scales compared to lower resolution models. This improved understanding and predictive capability is particularly important for regions with significant dam and hydroelectric infrastructure, such as eastern Canada.