Flexible Permafrost Model: a new process-based permafrost model for cross-scale studies

Understanding the dynamics and influences of permafrost under a warming climate heavily relies on numerical simulations. However, this task presents significant challenges as the state-of-the-art land surface models are found weak ability in representing permafrost processes. Here, we introduce the Flexible Permafrost Model (FPM), a land surface scheme designed model especially for permafrost applications. This model serves as a flexible platform to explore novel structures and parameterizations for a variety of permafrost processes. The FPM accounts for both vertical and lateral heat flow at and below the soil surface, while also describing the energy exchange with the atmosphere by considering radiative and turbulent fluxes. To demonstrate the utility of FPM for supporting permafrost studies, we apply the model to the simulations of global-scale permafrost extent and fine-scale permafrost island dynamics. Our simulation results are found reasonable against published permafrost extent and in situ observations, indicating FPM can serve as a stand-alone simulation tool for permafrost studies.