Identifying sensitive ranges in global warming precipitation change dependence on convective parameters

Bernstein, D. N.; Neelin, J. David

doi:10.1002/2016gl069022

Cited by 21 publications

(29 citation statements)

References 68 publications

(89 reference statements)

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“…The convection experiment (CONV) perturbs four parameters in the modified Zhang-McFarlane deep convection scheme (Neale et al, 2008;Zhang & McFarlane, 1995). Each parameter in CONV is perturbed up to five times (see also Bernstein & Neelin, 2016;Langenbrunner & Neelin, 2017). The cloud physics experiment (CLOUD) perturbs ten macrophysical and microphysical parameters.…”

Section: Methodsmentioning

confidence: 99%

Relationships Between Tropical Ascent and High Cloud Fraction Changes With Warming Revealed by Perturbation Physics Experiments in CAM5

Schiro

Wang

et al. 2019

Geophysical Research Letters

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Tropical ascent area (Aa) and high cloud fraction (HCF) are projected to decrease with surface warming in most Coupled Model Intercomparison Project Phase 5 (CMIP5) models. Perturbing deep convective parameters in the Community Atmosphere Model (CAM5) results in a similar spread and correlation between HCF and Aa responses to interannual warming compared to the CMIP5 ensemble, with a narrower Aa corresponding to greater HCF reduction. Perturbing cloud physics parameters produces a comparatively smaller range of Aa responses to warming and a dissimilar HCF‐Aa relation to that in CMIP5; a narrower Aa corresponds to less HCF reduction, likely due to cloud radiative effects. A narrowing of Aa corresponds to a regime shift toward stronger precipitation in both experiments. We infer that model differences in deep convection parameterization likely play a greater role than differing cloud physics in determining the diverse responses of Aa and HCF to warming in CMIP5.

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Section: Methodsmentioning

confidence: 99%

Relationships Between Tropical Ascent and High Cloud Fraction Changes With Warming Revealed by Perturbation Physics Experiments in CAM5

Schiro

Wang

et al. 2019

Geophysical Research Letters

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“…The present paper focuses on the dominant direction of causality in the fast-time-scale precipitation-CWV relationship and addresses the impacts of entrainment on the two-way interaction between deep convection and environmental humidity. Our methodology is based on analysis of parameter sensitivity experiments (Bernstein and Neelin 2016) in the Community Earth System Model (CESM), which is able to simulate the sharp precipitation pickup with the default setting (Sahany et al 2012(Sahany et al , 2014. We show that the set of statistics associated with the transition to deep convection (or ''convective transition statistics'') in the CESM can be radically altered if different values of entrainment are prescribed in the deep convective scheme.…”

Section: Introductionmentioning

confidence: 99%

Tropical Convective Transition Statistics and Causality in the Water Vapor–Precipitation Relation

Kuo

Neelin

Mechoso

2017

Journal of the Atmospheric Sciences

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Previous work by various authors has pointed to the role of lower-free-tropospheric humidity in affecting the onset of deep convection in the tropics. Empirical relationships between column water vapor (CWV) and precipitation have been inferred to result from these effects. Evidence from previous work has included deep convective conditional instability calculations for entraining plumes, in which the lower-free-tropospheric environment affects the onset of deep convection due to the differential impact on buoyancy of turbulent entrainment of dry versus moist air. The relationship between deep convection and water vapor is, however, a two-way interaction because convection also moistens the free troposphere. The present study adds an additional line of evidence toward fully establishing the causality of the precipitation-water vapor relationship. Parameter perturbation experiments using the coupled Community Earth System Model (CESM) with hightime-resolution output are analyzed for a set of statistics for the transition to deep convection, coordinated with observational diagnostics for the Green Ocean Amazon (GOAmazon) campaign and tropical western Pacific Atmospheric Radiation Measurement (ARM) sites. For low values of entrainment in the deep convective scheme, these statistics are radically altered and the observed pickup of precipitation with CWV is no longer seen. In addition to helping cement the dominant direction of causality in the fast-time-scale precipitation-CWV relationship, the results point to impacts of entrainment on the climatology. Because at low entrainment convection can fire before tropospheric moistening, the climatological values of relative humidity are lower than observed. These findings can be consequential to biases in simulated climate and to projections of climate change.

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“…The first 10 years are discarded to allow for model equilibration, so climatologies represent a 1985–2005 average. Bernstein and Neelin [] show that the hydrological cycle tends to adjust quickly to parameter changes (on time scales less than 10 years). Small remaining imbalances in top‐of‐atmosphere (TOA) radiation associated with adjustment of the deep ocean could be relevant to some climate quantities but are not a strong effect for those examined here.…”

Section: Datamentioning

confidence: 99%

“…Figure shows model RMSE as a function of parameter value for precipitation, column water vapor, and skin temperature fields in the tropical Pacific domain. A notable theme here is that all parameters show some degree of nonlinearity as a function of parameter value for a given field—even when the parameter dependence appears fairly linear in others—and these results parallel those of Bernstein and Neelin []. For example, the parameter dependence across α appears linear for column water vapor but more notably nonlinear at low α values for both precipitation and skin temperature.…”

Section: Parameter Sensitivity Across Multiple Fieldsmentioning

confidence: 99%

See 1 more Smart Citation

Multiobjective constraints for climate model parameter choices: PragmaticPareto fronts in CESM1

Langenbrunner

Neelin

2017

J Adv Model Earth Syst

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Global climate models (GCMs) are examples of high‐dimensional input‐output systems, where model output is a function of many variables, and an update in model physics commonly improves performance in one objective function (i.e., measure of model performance) at the expense of degrading another. Here concepts from multiobjective optimization in the engineering literature are used to investigate parameter sensitivity and optimization in the face of such trade‐offs. A metamodeling technique called cut high‐dimensional model representation (cut‐HDMR) is leveraged in the context of multiobjective optimization to improve GCM simulation of the tropical Pacific climate, focusing on seasonal precipitation, column water vapor, and skin temperature. An evolutionary algorithm is used to solve for Pareto fronts, which are surfaces in objective function space along which trade‐offs in GCM performance occur. This approach allows the modeler to visualize trade‐offs quickly and identify the physics at play. In some cases, Pareto fronts are small, implying that trade‐offs are minimal, optimal parameter value choices are more straightforward, and the GCM is well‐functioning. In all cases considered here, the control run was found not to be Pareto‐optimal (i.e., not on the front), highlighting an opportunity for model improvement through objectively informed parameter selection. Taylor diagrams illustrate that these improvements occur primarily in field magnitude, not spatial correlation, and they show that specific parameter updates can improve fields fundamental to tropical moist processes—namely precipitation and skin temperature—without significantly impacting others. These results provide an example of how basic elements of multiobjective optimization can facilitate pragmatic GCM tuning processes.

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Identifying sensitive ranges in global warming precipitation change dependence on convective parameters

Cited by 21 publications

References 68 publications

Relationships Between Tropical Ascent and High Cloud Fraction Changes With Warming Revealed by Perturbation Physics Experiments in CAM5

Relationships Between Tropical Ascent and High Cloud Fraction Changes With Warming Revealed by Perturbation Physics Experiments in CAM5

Tropical Convective Transition Statistics and Causality in the Water Vapor–Precipitation Relation

Multiobjective constraints for climate model parameter choices: PragmaticPareto fronts in CESM1

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