Inferring Surface Flux Partitioning over LAND from an Evolving Boundary Layer

Changes in the atmospheric boundary layer (ABL) height are largely impacted by the partitioning of surface fluxes, and thus serve as a good proxy for land-atmosphere (L-A) coupling. Despite the ABL’s recognized influence on weather conditions and air quality, there has been a deficit in high-resolution observations of its evolution that could serve as a basis for estimating surface fluxes. Previous studies seeking to do so rely heavily on numerical model simulations and observations incapable of temporally resolving the ABL. This study seeks to assess the extent to which characteristics of an evolving boundary layer reflect the partitioning of surface fluxes over land, evaluated as the evaporative fraction (EF), from an observational dataset capable of capturing ABL growth. As a first step, this research employs the use of a parcel-theory based-diagnostic analysis tool that quantifies convective initiation to estimate EF. As the tool has not been used previously to infer L-A coupling from ABL-resolving observations, it is being calibrated against single column model (SCM) ensemble simulations over the Southern Great Plains (SGP) during boreal summer. This allows for any inaccuracies in estimates to be accounted for along with the quantification of any error that exists after the adjustments. Once calibrated, the tool will be applied to a decade long observational record of ABL profiles, also over the SGP, from the American Meteorological Data Reports (AMDAR) dataset to estimate flux partitioning. Using data over the same region as the SCM simulations allows further evaluation using observational data, which is prone to noise in measurements and missing segments. After this verification, energy deficit estimations output from the tool applied to the AMDAR data are used to characterize regime limits indicating the presence (or absence) of L-A coupling. These regimes are divided by both EFs and measurement lead times relative to estimated convective initiation. The classification scheme allows the tool with observations to function independently of the SCM that only serves as verification of the estimated EF. Ultimately, the tool and scheme can be applied to all AMDAR sites or other locations with ABL measurements with the intent to understand when and where L-A coupling is important.