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GFDL Events & Seminars

Visitors without GFDL affiliation attending seminars or other organized events must present government or university issued photo ID or two other forms of identification to gain access to the facility. If an acceptable ID cannot be provided, the Visitor will not be allowed access. If access is granted, the Visitor must sign in and be given a Visitor Badge. The Visitor Badge expires immediately after the seminar.

September 4, 2019

calendar_today Local Epistemologies, Model Purpose, and Pluralism of Methods in Climate Model Development

person Lunchtime Seminar - Lunchtime Seminar Series - Monica Morrison (Indiana University, Bloomington)

access_time 12:00 pm - 1:00 pm

place Location: Smagorinsky Seminar Room

Climate modeling, like many areas of scientific practice, is composed of local research communities with distinct histories, whose practices are governed by their own local epistemologies. The local epistemology of a research community is constituted by the scientific aims, goals, assumptions, values, methodologies, and standards that operate in the research community and determine the course of research. In climate modeling, these local research communities and their associated epistemologies influence the course of model development by way of decisions about scientific goals, model purpose, and cognitive values, which are reflected in the subsequent decisions about representational priorities, implementation protocols, models of analysis, investigative strategies, methodological rules, and metrics and standards for determining model skill. Different local communities will have variations in the types of scientific problems they investigate, and differences in their other epistemic commitments, which ultimately results in a distinct perspective being taken by each local community on the complex system. For models this means that each model, which is the product of a local community, will partition the causal space according to their specified interests and related representational priorities—each model will thus pick out slightly different features of the complex causal system and represent them in slightly different ways consistent with their epistemology. Given this picture of modeling practice there are many models that are perspectival in nature, but no model that is a complete representation of the complex system. The perspectival nature of models might seem problematic because only certain features of the causal space are being represented and surveyed in a given model. However, I demonstrate that in historical and contemporary modeling practices there exists a plurality of communities, epistemologies, and associated models that exhibit representational pluralism, thus providing a multitude of different representational perspectives on the complex system. To maximize knowledge and increase degrees of objectivity, a plurality of models is desirable, and this desirable pluralism is a historical and contemporary feature of modeling practice.

September 11, 2019

calendar_today Uncertainty Quantification in Climate Modeling

person Lunchtime Seminar - Lunchtime Seminar Series - Qian Yun (Pacific Northwest National Laboratory (PNNL))

access_time 12:00 pm - 1:00 pm

place Location: Smagorinsky Seminar Room

DOE - Energy Exascale Earth System Model (E3SM) is a new model and has included many new features in the physics parameterizations compared to its predecessors. Potential complex nonlinear interactions among the new features create a significant challenge for understanding the model behaviors and parameter tuning. Using the one-at-a-time method, the benefit of tuning one parameter may offset the benefit of tuning another parameter, or the improvement in one target variable may lead to degradation in another target variable. To better understand the model behaviors and physics, we conducted a large number of short simulations in which 18 parameters carefully selected from parameterizations of deep convection, shallow convection and cloud macrophysics and microphysics were perturbed simultaneously using the Latin Hypercube sampling method. From the Perturbed Parameters Ensemble (PPE) simulations and use of different skill score functions, we identified the most sensitive parameters and their global spatial distribution, quantified how the model responds to changes of the parameters, and estimated the maximum likelihood of model parameter space for a number of important fidelity metrics. Results from this analysis provide a more comprehensive picture of the E3SM model behavior at global scale as well as at process level in different cloud regimes. The difficulty in reducing biases in multiple variables simultaneously highlights the need of characterizing model structural uncertainty (embedded errors) to inform future development efforts. In this talk, besides presenting above parametric sensitivity results in E3SM atmosphere model, I will also highlight a few applications using Uncertainty Quantification technics in model calibration and optimization, wind energy and aerosol study conducted at PNNL. Finally, I will discuss a few challenges and paths forward in this area. POC: Sarah Kapnick, and Paul Ginoux.

September 18, 2019

calendar_today Reconciling Predictability and Uncertainties in Seasonal Predictions and Future Projections of Tropical Cyclone Activity

person Lunchtime Seminar - Lunchtime Seminar Series - Gan Zhang (AOS)

access_time 12:00 pm - 1:00 pm

place Location: Smagorinsky Seminar Room

To be provided at a later date.

September 25, 2019

calendar_today Evaluating Last Interglacial Constraints on Future Antarctic Ice-Sheet Mass Losses with a Supervised Machine Learning Technique

person Lunchtime Seminar - Lunchtime Seminar Series - Daniel Gilford (Rutgers University)

access_time 12:00 pm - 1:00 pm

place Location: Smagorinsky Seminar Room

Antarctic ice loss has accelerated in recent decades, and its contributions to global sea level rise could be as high as ~1 meter by the end of the century. But deep uncertainties in ice-sheet physics make it difficult to produce robust projections of sea level rise. The lack of agreement among experts and poor constraints on ice-sheet model parameters exemplify this ambiguity. Past warm periods provide useful analog climates where sea levels were much higher than present, but these paleoclimate estimates are themselves deeply uncertain. It is critical to assess the efficacy of paleoclimate estimates constraining future Antarctic ice-sheet mass losses to (1) improve future projections of sea level rise and (2) inform paleoclimate research and observational goals. Here we use Gaussian Process regression to develop a statistical “emulator” designed to mimic the behavior of an ice-sheet model. Gaussian process modeling is a non-parametric supervised machine learning technique which maps inputs (e.g. ice-sheet model parameters) to target outputs (e.g. sea-level contributions from Antarctica) with explicit quantification of model uncertainties. Emulation is applied over the last interglacial (LIG; a warm period ~125,000 years ago) and a future high greenhouse gas emissions scenario, and is trained on ice-sheet model ensembles constructed by varying the parameters of maximum rate of ice-cliff loss and the coefficient of ice-shelf hydrofracturing. Emulated projections are calibrated with various LIG constraints on Antarctic sea level contributions to find the likely configurations of model parameterizations. Using a Bayesian approach, we quantify uncertainties in future projections from the ice-sheet model if the LIG estimated contributions were well-known. Results also show how specific assumptions about the LIG period (such as those used in past studies) can influence future projections, and highlight the importance of continued observational efforts.

October 9, 2019

calendar_today Scorched Earth: Ecosystem-Atmosphere Interactions Exacerbate Climate Penalty on Air Pollution in Europe

person Lunchtime Seminar - Lunchtime Seminar Series - Meiyun Lin

access_time 12:00 pm - 1:00 pm

place Location: Smagorinsky Seminar Room


October 16, 2019

calendar_today Progress in quantifying the effective radiative forcing due to aerosol-cloud interactions

person Lunchtime Seminar - Lunchtime Seminar Series - Johannes Quaas

access_time 12:00 pm - 1:00 pm

place Location: Smagorinsky Seminar Room

The effective radiative forcing due to aerosol-cloud interaction, ERFaci, is composed of the radiative forcing due to aerosol-cloud interactions, RFaci (Twomey effect) that is the immediate response of cloud albedo to an increase in droplet number concentration, Nd. Previous satellite-based quantifications of this effect were hampered by deficiencies in the retrieval of aerosol and also Nd. The talk will firstly discuss progress in this regard, which leads to a stronger estimated RFaci than previous satellite-based approaches. The other component of ERFaci is in the cloud adjustments. These can be split into adjustments of cloud fraction, f, and liquid water path, L. In terms of the latter, statistical relationships between L and Nd show on average negative adjustments of L (a positive forcing component). In turn, the analysis of ship-, volcano- and industry tracks leads to an estimated small overall effect on L; these results are trustworthy since a cause-effect relation is assured. In terms of the f adjustment, the current results point to an increase in cloud fraction at larger Nd. It is unclear which processes lead to this result. The talk will also briefly discuss how cloud-resolving simulations may help to better understand the remaining uncertainties. In the last part, a brief discussion will be presented on initial steps towards an estimate of the response of cirrus to anthropogenic aerosols. POC: Leo Donner or Yi Ming

November 22, 2019

calendar_today Dr. Kikuro Miyakoda Symposium

person Special Event - Dr. Kikuro Miyakoda Symposium

access_time 12:00 pm - 5:00 pm

place Location: Smagorinsky Seminar Room

Dr. Kikuro Miyakoda Symposium will highlight Kikuro's life achievements in the world of Science. A memorial coordinated by his Daughter will be in the morning.

December 5, 2019

calendar_today Eddy Saturation

person Informal Seminar - Navid Constantinou (Australian National University)

access_time 10:30 am - 11:30 am

place Location: 317 Seminar Room

Eddy Saturation