| Abstrakt: |
Arctic clouds play a key role in Arctic climate variability and change; however, contemporary climate models struggle to simulate cloud properties accurately. Model‐simulated cloud properties are determined by the physical parameterizations and their interactions within the model configuration. Quantifying effects of individual parameterization changes on model‐simulated clouds informs efforts to improve models and provides insights on climate system behavior. This study quantities the influence of parameterization scheme changes on Arctic low cloud properties within the Hadley Center Global Environmental Model 3 atmospheric model using a suite of experiments where individual parameterization packages are changed between the two configurations. The results indicate, surprisingly, that single parameterization changes explain most of the cloud property changes, whereas multiple parameterizations, including non‐cloud schemes, contribute to cloud radiative effect differences. Non‐cloud parameterizations are those not used to compute time step cloud properties. We employ a three‐term decomposition to quantify contributions from (a) regime independent, (b) regime dependent, and (c) the regime frequency of occurrence changes. Decomposition results indicate that cloud property changes vary by meteorological regime, each term contributes differently to each cloud property change, and non‐cloud parameterization changes make substantial contributions to the LW and SW cloud radiative effects by affecting clear‐sky fluxes. The analysis provides insights on the role of non‐cloud parameterizations for setting cloud radiative effects, a pathway for cloud‐atmosphere circulation interactions, raises questions on the importance of infrequently occurring regimes to climate simulations, and on useful observational approaches for improving models. Plain Language Summary: Arctic clouds play a key role in Arctic climate variability and change; however, state‐of‐the‐art climate models struggle to accurately simulate clouds. Errors in model‐simulated clouds have known and unknown influences on the simulated climate and climate change projections. Model cloud properties are determined by the physical parameterizations and their interactions within the model. Thus, to improve model‐simulated clouds, we need to understand the effects of parameterization changes. We use a series of Hadley Center Global Environmental Model 3 atmospheric model simulations where individual parameterizations are changed one‐at‐a‐time. This approach allows us to isolate the influence of individual cloud parameterizations on model‐simulated cloud properties to inform model development and the observations needed to improve models. The results show that individual parameterizations are most important for specific cloud variables and that multiple parameterizations are important to determining the model‐simulated influence of clouds on the energy budget. We also find that changes in model‐simulated cloud properties respond differently under different weather conditions. The analysis provides insights on the role of non‐cloud parameterizations, defined as those that are not used to directly compute cloud properties, for setting cloud radiative effects, the ways that clouds and the atmosphere interact, raises questions on the importance of infrequently occurring weather conditions to climate simulations, and on useful observational approaches for improving models. Key Points: Individual parameterization changes explain cloud property changes while multiple parameterizations explain cloud radiative effect changesThe large‐scale cloud scheme accounts for most of the changes in Arctic meteorological regime frequencyNon‐cloud parameterizations must be considered to understand the full influence of parameterization changes on cloud radiative effects [ABSTRACT FROM AUTHOR] |
