Observation and Reanalysis Derived Relationships Between Cloud and Land Surface Fluxes Across Cumulus and Stratiform Coupling Over the Southern Great Plains

Understanding interactions between low clouds and land surface fluxes is critical to comprehending Earth's energy balance, yet their relationships remain elusive, with discrepancies between observations and modeling. Leveraging long-term field observations over the Southern Great Plains, this investigation revealed that cloud-land interactions are closely connected to cloud-land coupling regimes. Observational evidence supports a dual-mode interaction: coupled stratiform clouds predominate in low sensible heat scenarios, while coupled cumulus clouds dominate in high sensible heat scenarios. Reanalysis data sets, MERRA-2 and ERA-5, obscure this dichotomy owing to a shortfall in representing boundary layer clouds, especially in capturing the initiation of coupled cumulus in high sensible heat scenarios. ERA-5 demonstrates a relatively closer alignment with observational data, particularly in capturing relationships between cloud frequency and latent heat, markedly outperforming MERRA-2. Our study underscores the necessity of distinguishing different cloud coupling regimes, essential to the understanding of their interactions for advancing land-atmosphere interactions. Low cloud interactions with the Earth's surface in the Southern Great Plains are examined to understand the coupling between low clouds and the land surface. Clouds play a major role in Earth's radiation energy balance and therefore the climate system, yet the cloud-land interaction relationship is complicated and not well-understood. Based on analyses of long-term field observations, we find that cloud-land interactions in this region are closely related to cloud-land coupling regimes. Observational evidence supports a dual-mode interaction: coupled stratiform clouds that dominate in low sensible heat states and coupled cumulus that dominate in high sensible heat states. The reanalysis data sets exhibit a common shortcoming of a deficit in boundary layer cloud parameterization, with a poorer representation of the initiation of coupled cumulus especially. This study highlights the importance of understanding the different cloud coupling regimes that interact with the land, which is essential for advancing weather and climate models. This study develops a diagnostic approach for untangling cloud-land relationships across distinct cloud coupling regimes Field observations are utilized to assess performances of reanalysis data in representing cloud-land interaction across different regimes Findings emphasize the importance of differentiating cloud coupling regimes in observational and modeling studies of boundary layer clouds