Toward merging MOPEX and CAMELS hydrometeorological datasets: compatibility and statistical comparison

Abstract. This study compares two large hydrometeorological datasets, the Model Parameter Estimation Experiment (MOPEX), and the Catchment Attributes and Meteorology for Large-sample Studies (CAMELS), focusing on 47 shared watersheds within the continental United States. The evaluation spans daily, monthly, seasonal, and annual scales for the overlapping water years of 1981 to 2000. Spatial aggregations are conducted based on Köppen-Geiger climate regions along with annual Budyko evaporative and aridity indices. Results indicate significant differences between the datasets at daily timesteps, highlighting the challenge of high temporal resolution data reconciliation; however, compatibility markedly improves with temporal aggregation at monthly, seasonal, and annual scales. While MOPEX shows a warm bias for temperature and CAMELS shows a wet bias for precipitation, statistical analyses demonstrate that both datasets are representative of climatic conditions and extreme events. Our findings validate the results of previous research employing either dataset. Furthermore, this study serves as a foundation for the merging and extension of MOPEX and CAMELS datasets.