Meridional Heat Transport During Atmospheric Rivers in High‐Resolution CESM Climate Projections
Meridional sensible and latent heat transport is quantified and evaluated for regions with landfalling atmospheric rivers using both MERRA-2 reanalysis and fully coupled CESM1.3 high-resolution climate projections. Uncertainty in these calculations due to AR identification is assessed by applying available Tier 1 AR-catalogues from Atmospheric Tracking Method Intercomparison Project (ARTMIP) to the MERRA-2 reanalysis. CESM1.3 climate projections suggest that under global warming, latent heat transport increases across all regions in the mid-latitudes where sensible heat decreases (increases) for Western North America (Europe). Generally, changes to the meridional heat transport are forced by the upper-level meridional wind component
Much of the atmospheric river (AR) research to date has focused on water, not energy, transport. In this study, sensible and latent heat transport is uniquely and explicitly computed for landfalling ARs impacting western North America, the UK, and the Iberian Peninsula. Mechanistic differences between regional ARs in the context of heat transport are evident, in particular for latent heat, and illustrate the importance of evaluating ARs from a regional perspective where the climate change response depends on the flavor of AR.
We show that there is general agreement in both transport quantities and latitudinal distribution across ARTMIP members for the MERRA-2 data. Under global warming using CESM1.3 data and the Shields/Kiehl detection algorithm, latent heat transport increases across all regions in the mid-latitudes although there is a different latitudinal signature for transport by ARs compared to the climatology across the full record. For sensible heat transport, western North America (Europe) is projected to experience less (more) heat transport by ARs. The mechanism driving the changes in meridional heat transport by ARs can be primarily tied to upper-level meridional winds.