The Earth Model Column Collaboratory (EMC) Ground-Based Lidar and Radar Instrument Simulator and Subcolumn Generator for Large-Scale Models

Climate models are essential for our comprehensive understanding of Earth's atmosphere and can provide critical insights on future changes decades ahead. Because of these critical roles, today's climate models are continuously being developed and evaluated using constraining measurements. Instrument simulators can provide a bridge between the measured or retrieved quantities and their sampling in models and field observations while considering instrument sensitivity limitations. Here we present the Earth Model Column Collaboratory (EMC²; https://github.com/columncolab/EMC2), an open-source ground-based lidar and radar instrument simulator and subcolumn generator, specifically designed for large-scale models, in particular climate models, but also applicable to high-resolution model output. EMC² provides a flexible framework enabling direct comparison of model output with ground-based observations, including the generation of subcolumns that may statistically represent finer model spatial resolutions. In addition, EMC² emulates ground-based (and air- or space-borne) measurements while remaining faithful to large-scale models' physical assumptions implemented in their cloud or radiation schemes. To facilitate model evaluation, EMC² also includes three hydrometeor classification methods. The Python software is easy to use, and can be straightforwardly customized for different models, radars and lidars. To demonstrate the use of EMC² we present a case study of a highly supercooled mixed-phase cloud based on measurements from the U.S. DOE Atmospheric Radiation Measurement (ARM) West Antarctic Radiation Experiment (AWARE). We compare observations with the application of EMC² to outputs from four configurations of the NASA Goddard Institute for Space Studies climate model (ModelE3) in single-column model (SCM) mode and a large-eddy simulation (LES) model. We show that two of the four ModelE3 configurations can form and maintain a highly supercooled precipitating cloud for several hours, consistent with observations and LES. While our focus is on one of these ModelE3 configurations, which performed slightly better in this case study, both configurations and the LES results post-processed with EMC² generally provide reasonable agreement with observed lidar and radar variables.