Meridional Heat Transport During Atmospheric Rivers in High‐Resolution CESM Climate Projections

• Published in: Geophysical research letters 2019-12, Vol.46 (24), p.14702-14712
• Main Authors: Shields, Christine A., Rosenbloom, Nan, Bates, Susan, Hannay, Cecile, Hu, Aixue, Payne, Ashley E., Rutz, Jonathan J., Truesdale, John
• Format: Article
• Language: English
• Subjects: ARTMIP; Atmosphere; atmospheric rivers; CESM high‐resolution model; Climate; Climate change; Climatic analysis; Drought; Earth; Energy transport; Enthalpy; ENVIRONMENTAL SCIENCES; Global warming; Heat; Heat transport; Hydrologic cycle; Hydrological cycle; Hydrology; Intercomparison; Latent heat; Meridional heat transport; Meridional wind; Phase changes; Regions; Resolution; Sensible and latent heat; Sensible heat; Storms; Transport; Water transport; Wind components
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2019GL085565

Meridional sensible and latent heat transport is evaluated for regions with landfalling atmospheric rivers using both MERRA‐2 reanalysis and fully coupled CESM1.3 high‐resolution climate projections. Western North America, the United Kingdom, and the Iberian Peninsula are chosen to represent the regions significantly impacted by atmospheric rivers (ARs). CESM1.3 historical simulations can accurately represent both sensible and latent regional meridional heat transports compared to MERRA‐2 both for the total period analyzed (1980–2016) and for days with atmospheric rivers only. Uncertainty in these calculations due to AR identification is assessed by applying available Tier 1 AR‐catalogs from Atmospheric Tracking Method Intercomparison Project (ARTMIP) to the MERRA‐2 analysis. 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. Plain Language Summary Atmospheric rivers (ARs) are long, filamentary structures in the atmosphere that transport significant amounts of water and energy from lower latitudes to higher latitudes. They can be considered a subset of an extratropical storm and are commonly found in the mid‐latitudes. To date, the majority of research has focused on water transport simply because ARs are an important part of Earth's hydrological cycle and can act as either drought‐busters or mechanisms for catastrophic floods, particularly in regions such as western North America and western Europe. Here, rather than focusing on water transport, we analyze two key contributors to total energy transport in the atmosphere: (1) heat produced by the phase changes of water (latent heat) and (2) heat produced by a change in temperature (sensible heat). With global warming, for days with landfalling atmospheric rivers, we find that sensible heat transport decreases for western North America but increases for western Europe. Latent heat transport, however, increases across all regions. Key Points Heat transport during landfalling atmospheric rivers is explicitly computed for western North America and Europe Under global warming, latent heat transport increases across all regions in the mid‐latitudes where sensible heat decreases (increases) for western North America (Europe) Upper‐level meridional