Climatology and associated precipitation of fronts co-occurring with ARs and MCSs

Abstract It is well-known that fronts, atmospheric rivers (ARs), and mesoscale convective systems (MCSs) are important weather phenomena linked to hydrological events. Less has been discussed on frontal precipitation when fronts co-occur with other two. This study uses objective algorithms applied to reanalysis and observational datasets to detect these three weather phenomena and categorizes midlatitude fronts based on whether they co-occur with ARs and MCSs. A large proportion of fronts co-occur with ARs. Fronts with ARs and MCSs are common within the storm tracks. Front number varies by type, category, and latitude, as do front intensity, size and related precipitation. Using satellite-derived precipitation estimates, we explore the frontal precipitation distribution and the relationship between precipitation area and intensity of front objects. Results show that fronts with ARs only are frequently associated with light precipitation and tend to have large precipitation areas, whereas fronts with MCSs only are frequently associated with moderate-to-intense precipitation. Fronts with both are more often associated with high rates and produce substantial precipitation amounts within large precipitation areas. Investigation of environmental factors, including frontogenesis, total column water vapor (TCWV), and convective available potential energy (CAPE), over the selected ocean regions suggests a general positive relationship with frontal precipitation, but varying by region. Fronts with ARs and with MCSs have different environmental features, the former of which frequently have high TCWV and the latter have strong CAPE. Peak frontal precipitation is more likely related to convective updrafts of MCSs, rather than frontogenetical forcing or ARs.