Increased Variability of Biomass Burning Emissions in CMIP6 Amplifies
Hydrologic Cycle in the CESM2 Large Ensemble
Abstract
Historical simulations performed for the Coupled Model Intercomparison
Project Phase 6 (CMIP6) used biomass burning emissions between
1997–2014 containing higher spatial and temporal variability compared
to emission inventories specified for earlier years, and compared to
emissions used in previous (e.g., CMIP5) simulation intercomparisons.
Using the Community Earth System Model version 2 (CESM2) Large Ensemble,
we show this increased biomass burning emissions variability leads to
amplification of the hydrologic cycle poleward of 40°N. Notably, the
high variability of biomass burning emissions leads to increased latent
heat fluxes, column-integrated precipitable water, and precipitation.
Lower relative humidity, greater static stability, greater ocean heat
uptake, and weaker meridional energy transport from the tropics act to
moderate this hydrologic cycle amplification. Our results suggest it is
not only the secular changes (on multidecadal timescales) in biomass
burning emissions that impact the hydrologic cycle, but also the shorter
timescale variability of their emissions.