Journal of Advances in Modeling Earth Systems

Journal: Journal of Advances in Modeling Earth Systems

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Wiley

ISSN

1942-2466

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Publications1 - 10 of 26

Arctic sea‐ice evolution as modeled by Max Planck Institute for Meteorology's Earth system model
Notz, Dirk; Haumann, Alexander; Haak, Helmuth; et al. (2013)
Journal of Advances in Modeling Earth Systems
New turbulent resistance parameterization for soil evaporation based on a pore‐scale model: Impact on surface fluxes in CABLE
Decker, Mark; Or, Dani; Pitman, Andy; et al. (2017)
Journal of Advances in Modeling Earth Systems
The Community Atmosphere Biosphere Land Exchange (CABLE) land surface model overestimates evapotranspiration (E) at numerous flux tower sites during boreal spring. The overestimation of E is not eliminated when the nonlinear dependence of soil evaporation on soil moisture or a simple litter layer is introduced into the model. New resistance terms, previously developed from a pore‐scale model of soil evaporation, are incorporated into the treatment of under canopy water vapor transfer in CABLE. The new resistance terms reduce the large positive bias in spring time E at multiple flux tower sites and also improve the simulation of daily sensible heat flux. The reduction in the spring E bias allows the soil to retain water into the summer, improving the seasonality of E. The simulation of daily E is largely insensitive to the details of the implementation of the pore model resistance scheme. The more physically based treatment of soil evaporation presented here eliminates the need for empirical functions that reduce evaporation as a function of soil moisture that are included in many land surface models.
Atmospheric component of the MPI‐M Earth System Model: ECHAM6
Stevens, Bjorn; Giorgetta, Marco; Esch, Monika; et al. (2013)
Journal of Advances in Modeling Earth Systems
ECHAM6, the sixth generation of the atmospheric general circulation model ECHAM, is described. Major changes with respect to its predecessor affect the representation of shortwave radiative transfer, the height of the model top. Minor changes have been made to model tuning and convective triggering. Several model configurations, differing in horizontal and vertical resolution, are compared. As horizontal resolution is increased beyond T63, the simulated climate improves but changes are incremental; major biases appear to be limited by the parameterization of small‐scale physical processes, such as clouds and convection. Higher vertical resolution in the middle atmosphere leads to a systematic reduction in temperature biases in the upper troposphere, and a better representation of the middle atmosphere and its modes of variability. ECHAM6 represents the present climate as well as, or better than, its predecessor. The most marked improvements are evident in the circulation of the extratropics. ECHAM6 continues to have a good representation of tropical variability. A number of biases, however, remain. These include a poor representation of low‐level clouds, systematic shifts in major precipitation features, biases in the partitioning of precipitation between land and sea (particularly in the tropics), and midlatitude jets that appear to be insufficiently poleward. The response of ECHAM6 to increasing concentrations of greenhouse gases is similar to that of ECHAM5. The equilibrium climate sensitivity of the mixed‐resolution (T63L95) configuration is between 2.9 and 3.4 K and is somewhat larger for the 47 level model. Cloud feedbacks and adjustments contribute positively to warming from increasing greenhouse gases.
Chasing Ice Crystals: Interlinking Cloud Microphysics and Dynamics in Cloud Seeding Plumes With Lagrangian Trajectories
Omanovic, Nadja; Ferrachat, Sylvaine; Fuchs, Christopher; et al. (2025)
Journal of Advances in Modeling Earth Systems
The ice phase is a major contributor to precipitation formation over continents due to its efficiency in growing hydrometeors to large enough sizes for sedimentation. One prominent growth mechanism is the vapor deposition onto ice crystals. However, its actual growth rates remain ambiguous. In the CLOUDLAB project, we conducted field experiments in supercooled clouds with the goal to infer ice crystal growth rates through local perturbations from cloud seeding. In this study, we combine a high-resolution model setup of 65 m with Lagrangian trajectories to achieve a more straightforward comparison to the observations. We first show that the chosen field experiments can be reproduced in the model in terms of ice crystal number concentration. Second, we perform a series of sensitivity studies by perturbing two parameters in the vapor depositional growth equation. The goal is to understand what change is needed to achieve an agreement between simulated and observed ice crystal growth rates since the default model configuration fails to do so. Increasing the vapor deposition efficiency by a factor of up to three yields comparable growth rates to the observations. Last, we try to quantify the different contributions to the vertical motions within the seeding plume, such as the large-scale forcing, the underlying topography, and latent heat release upon ice nucleation and growth. We show the different factors are superposed with the large-scale forcing being a dominant factor. The Lagrangian trajectories proved to be crucial to bridge dynamics and cloud microphysical processes.
Revisiting Machine Learning Approaches for Short‐ and Longwave Radiation Inference in Weather and Climate Models
Bertoli, Guillaume; Mohebi Ganjabadi, Salman; Ozdemir, Firat; et al. (2025)
Journal of Advances in Modeling Earth Systems
This paper explores Machine Learning (ML) parameterizations for radiative transfer in the ICOsahedral Nonhydrostatic weather and climate model (ICON) and investigates the achieved ML model speed‐up with ICON running on graphics processing units (GPUs). Five ML models, with varying complexity and size, are coupled to ICON; more specifically, a multilayer perceptron (MLP), a Unet model, a bidirectional recurrent neural network with long short‐term memory (BiLSTM), a vision transformer (ViT), and a random forest (RF) as a baseline. The ML parameterizations are coupled to the ICON code that includes OpenACC compiler directives to enable GPU support. The coupling is done with the PyTorch‐Fortran coupler developed at NVIDIA. The most accurate model is the BiLSTM with a physics‐informed normalization strategy, a penalty for the heating rates during training, a Gaussian smoothing as postprocessing and a simplified computation of the fluxes at the upper levels to ensure stability of the ICON model top. The presented setup enables stable aquaplanet simulations with ICON for several weeks at a resolution of about 80 km and compares well with the physics‐based default radiative transfer parameterization, ecRad. Our results indicate that the compute requirements of the ML models that can ensure the stability of ICON are comparable to GPU optimized classical physics parameterizations in terms of memory consumption and computational speed.
Global Photosynthesis Acclimates to Rising Temperatures Through Predictable Changes in Photosynthetic Capacities, Enzyme Kinetics, and Stomatal Sensitivity
Schneider, Pascal Daniel; Gessler, Arthur; Stocker, Benjamin (2025)
Journal of Advances in Modeling Earth Systems
Thermal acclimation of photosynthesis, the physiological adjustment to temperature over weeks, may help plants mitigate adverse impacts of global warming, but is often under-represented in Earth System Models (ESMs). We evaluated a plant functional type (PFT)-agnostic, optimality-based model of C$_3$ photosynthesis with a global data set of leaf gas exchange measurements. We investigated how three key photosynthesis traits vary along a gradient of growing-season temperatures (T$_{growth}$): optimal photosynthesis temperature (T$_{opt}$), net photosynthesis rate at T$_{opt}$ (A$_{opt}$), and the width of the temperature response curve (T$_{span}$). We analyzed how each trait is influenced by three acclimation processes: acclimation of photosynthetic capacities (carboxylation, electron transport, and respiration), their enzymatic responses, and stomatal sensitivity to vapor pressure deficit. The inclusion of all three acclimation processes was essential for reproducing observed patterns: a linear increase in T$_{opt}$ with T$_{growth}$, and no correlations of A$_{opt}$ and T$_{span}$ with T$_{growth}$. Acclimation of enzymatic responses and stomatal sensitivity was crucial for accurately predicting T$_{opt}$ and T$_{span}$. Acclimation of the photosynthetic capacities was necessary to avoid a bias in A$_{opt}$ that can arise when relying on static, PFT-specific parameters. Comparing a model with all and a model without any acclimation processes showed that thermal acclimation buffers the response of photosynthesis to warming substantially, leading to smaller increases in photosynthesis in cold climates (+2% instead of +18%) and smaller declines in warm climates (−4% instead of −22%). Our observations-constrained photosynthesis predictions suggest an important role of thermal acclimation in ESM, partly mitigating adverse effects of a warming climate.
Evaluation of boundary layer cloud parameterizations in the ECHAM5 general circulation model using CALIPSO and CloudSat satellite data
Nam, Christine C.W.; Quaas, Johannes; Neggers, Roel; et al. (2014)
Journal of Advances in Modeling Earth Systems
Three different boundary layer cloud models are incorporated into the ECHAM5 general circulation model (GCM) and compared to CloudSat and CALIPSO satellite observations. The first boundary layer model builds upon the standard Tiedtke (1989) parameterization for shallow convection with an adapted convective trigger; the second is a bulk parameterization of the effects of transient shallow cumulus clouds; and lastly the Dual Mass Flux (DMF) scheme adjusted to better represent shallow convection. The three schemes improved (Sub)Tropical oceanic low‐level cloud cover, however, the fraction of low‐level cloud cover remains underestimated compared to CALIPSO observations. The representation of precipitation was improved by all schemes as they reduced the frequency of light intensity events <0.01 mm d−1, which were found to dominate the radar reflectivity histograms as well as be the greatest source of differences between ECHAM5 and CloudSat radar reflectivity histograms. For both lidar and radar diagnostics, the differences amongst the schemes are smaller than the differences compared to observations. While the DMF approach remains experimental, as its top‐of‐atmosphere radiative balance has not been retuned, it shows the most promise in producing nonprecipitating boundary layer clouds. With its internally consistent boundary layer scheme that uses the same bimodal joint distribution with a diffusive and an updraft component for clouds and turbulent transport, the ECHAM5_DMF produces the most realistic boundary layer depth as indicated by the cloud field. In addition, it reduced the frequency of large‐scale precipitation intensities of <0.01 mm d−1 the greatest.
Global contrail coverage simulated by CAM5 with the inventory of 2006 global aircraft emissions
Chen, Chih-Chieh; Gettelman, Andrew; Craig, Cheryl; et al. (2012)
Journal of Advances in Modeling Earth Systems
The Influence of Convective Momentum Transport and Vertical Wind Shear on the Evolution of a Cold Air Outbreak
Saggiorato, Beatrice; Nuijens, Louise; Siebesma, A. Pier; et al. (2020)
Journal of Advances in Modeling Earth Systems
To study the influence of convective momentum transport (CMT) on wind, boundary layer and cloud evolution in a marine cold air outbreak (CAO) we use large‐eddy simulations subject to different baroclinicity (wind shear) but similar surface forcing. The simulated domain is large enough, urn:x-wiley:jame:media:jame21100:jame21100-math-0001 km2), to develop typical mesoscale cellular convective structures. We find that a maximum friction induced by momentum transport (MT) locates in the cloud layer for an increase of geostrophic wind with height (forward shear, FW) and near the surface for a decrease of wind with height (backward shear, BW). Although the total MT always acts as a friction, the interaction of friction‐induced cross‐isobaric flow with the Coriolis force can develop supergeostrophic winds near the surface (FW) or in the cloud layer (BW). The contribution of convection to MT is evaluated by decomposing the momentum flux by column water vapor and eddy size, revealing that CMT acts to accelerate subcloud layer winds under FW shear and that mesoscale circulations contribute significantly to MT for this horizontal resolution (250 m), even if small‐scale eddies are nonnegligible and likely more important as resolution increases. Under FW shear, a deeper boundary layer and faster cloud transition are simulated, because MT acts to increase surface fluxes and wind shear enhances turbulent mixing across cloud tops. Our results show that the coupling between winds and convection is crucial for a range of problems, from CAO lifetime and cloud transitions to ocean heat loss and near‐surface wind variability.
Complex functionality with minimal computation: Promise and pitfalls of reduced‐tracer ocean biogeochemistry models
Galbraith, Eric D.; Dunne, John P.; Gnanadesikan, Anand; et al. (2015)
Journal of Advances in Modeling Earth Systems
Earth System Models increasingly include ocean biogeochemistry models in order to predict changes in ocean carbon storage, hypoxia, and biological productivity under climate change. However, state‐of‐the‐art ocean biogeochemical models include many advected tracers, that significantly increase the computational resources required, forcing a trade‐off with spatial resolution. Here, we compare a state‐of‐the art model with 30 prognostic tracers (TOPAZ) with two reduced‐tracer models, one with 6 tracers (BLING), and the other with 3 tracers (miniBLING). The reduced‐tracer models employ parameterized, implicit biological functions, which nonetheless capture many of the most important processes resolved by TOPAZ. All three are embedded in the same coupled climate model. Despite the large difference in tracer number, the absence of tracers for living organic matter is shown to have a minimal impact on the transport of nutrient elements, and the three models produce similar mean annual preindustrial distributions of macronutrients, oxygen, and carbon. Significant differences do exist among the models, in particular the seasonal cycle of biomass and export production, but it does not appear that these are necessary consequences of the reduced tracer number. With increasing CO2, changes in dissolved oxygen and anthropogenic carbon uptake are very similar across the different models. Thus, while the reduced‐tracer models do not explicitly resolve the diversity and internal dynamics of marine ecosystems, we demonstrate that such models are applicable to a broad suite of major biogeochemical concerns, including anthropogenic change. These results are very promising for the further development and application of reduced‐tracer biogeochemical models that incorporate “sub‐ecosystem‐scale” parameterizations.

Publications1 - 10 of 26

Journal: Journal of Advances in Modeling Earth Systems

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