Benefits of Deterministic and Stochastic Tendency Adjustments in a Climate Model ...

• Main Authors: Chapman, William E., Berner, Judith
• Format: Report
• Language: unknown
• Published: arXiv 2023
• Subjects: Atmospheric and Oceanic Physics physics.ao-ph; FOS Physical sciences; North Atlantic; North Atlantic oscillation
• Online Access: https://dx.doi.org/10.48550/arxiv.2308.15295; https://arxiv.org/abs/2308.15295

We develop and compare model-error representation schemes derived from data assimilation increments and nudging tendencies in multi-decadal simulations of the community atmosphere model, version 6. Each scheme applies a bias correction during simulation run-time to the zonal and meridional winds. We quantify to which extent such online adjustment schemes improve the model climatology and variability on daily to seasonal timescales. Generally, we observe a ca. 30% improvement to annual upper-level zonal winds, with largest improvements in boreal spring (ca. 35%) and winter (ca. 47%). Despite only adjusting the wind fields, we additionally observe a ca. 20% improvement to annual precipitation over land, with the largest improvements in boreal fall (ca. 36%) and winter (ca. 25%), and a ca. 50% improvement to annual sea level pressure, globally. With mean state adjustments alone, the dominant pattern of boreal low-frequency variability over the Atlantic (the North Atlantic Oscillation) is significantly improved. ...