  Large-eddy simulation (LES) is able to capture key boundary-layer (BL)
turbulence and cloud processes. Yet, large-scale forcing and surface turbulent
fluxes of sensible and latent heat are often poorly prescribed for LES
simulations. We derive these quantities from measurements and reanalysis
obtained for two cold air outbreak (CAO) events during Phase I of the Aerosol
Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE)
in February-March 2020. We study the two contrasting CAO cases by performing
LES and test the sensitivity of BL structure and clouds to large-scale forcings
and turbulent heat fluxes. Profiles of atmospheric state and large-scale
divergence and surface turbulent heat fluxes obtained from the reanalysis data
ERA5 agree reasonably well with those derived from ACTIVATE field measurements
for both cases at the sampling time and location. Therefore, we adopt the time
evolving heat fluxes, wind and advective tendencies profiles from ERA5
reanalysis data to drive the LES. We find that large-scale thermodynamic
advective tendencies and wind relaxations are important for the LES to capture
the evolving observed BL meteorological states characterized by the hourly ERA5
reanalysis data and validated by the observations. We show that the divergence
(or vertical velocity) is important in regulating the BL growth driven by
surface heat fluxes in LES simulations. The evolution of liquid water path is
largely affected by the evolution of surface heat fluxes. The liquid water path
simulated in LES agrees reasonably well with the ACTIVATE measurements.This
study paves the path to investigate aerosol-cloud-meteorology interactions
using LES informed and evaluated by ACTIVATE field measurements.
