Skip to content

GFDL Past Events & Seminars - 2012

Click a row to display that event's description/abstract.

Date Speaker Affiliation Title of Presentation
Jan. 5Steve SherwoodUniversity of New South WalesA connection between tropical lapse rates, severe hurricanes, and peak heat stress
A connection between tropical lapse rates, severe hurricanes, and peak heat stress
Jan. 11Marcelo Barreiro Universidad de la Republica, Uruguay, Visiting Scholar at AOSExplorations of tropical oceans response to external forcing
Explorations of tropical oceans response to external forcing
Jan. 12Pat GlibertUMCESEcological stoichiometry, biogeochemical cycling and aquatic food webs: The view beyond carbon
Nutrient ratios have long been thought to infer system regulation only when nutrient concentrations are at levels limiting to the phytoplankton assemblage. A prevailing view has considered nutrient ratios to be ecologically irrelevant unless concentrations are in these limiting ranges. This talk addresses the theme that nutrient ratios do play important roles in shaping aquatic food webs whether nutrients are limiting are not. Three aspects will be emphasized. First, nutrient ratios are changing globally due to anthropogenic activities. Second, physiological regulation by nutrients continues by cells even in the "super-saturation"range of the kinetic curve. This has importance consequences for biomass composition, i.e. food quality. Third, the relative availability of different nutrients also exerts considerable influence on higher trophic levels via changes in food quality and via altered biogeochemical cycling. From both an ecological as well as a modeling perspective, strengthened insights about food web dynamics can be gained by the use of "currencies"beyond C. While productivity is a function of C, community composition at all levels of the food web is more strongly linked to N and P availability and their dynamics.
Jan. 18Jan-Huey ChenAOS Post DocSeasonal Prediction of Tropical Cyclones Using GFDL's C360-HiRAM
Seasonal Prediction of Tropical Cyclones Using GFDL's C360-HiRAM
Jan. 19Benjamin CookColumbia - LDEOIntensification of North American megadroughts through surface and dust aerosol forcing.
During the Medieval Climate Anomaly (MCA), North America experienced recurrent periods of drought spanning decades or longer. These `megadroughts' had exceptional persistence compared to more recent events, and many climate models have difficulty reproducing droughts of similar duration. We conducted a suite of general circulation model experiments to test the impact of sea surface temperature (SST), land surface, and other (solar, volcanic, etc) forcings during the megadroughts. The land surface forcing is represented as a set of dune mobilization boundary conditions, derived from available geomorphological evidence and modeled as increased bare soil area and a dust aerosol source over the Central Plains (105W-95W, 32N-44N). Cold tropical Pacific SST forcing and other MCA forcings stimulate warming and drying over the Central Plains, but can not reproduce the persistence of the megadroughts. In our simulation with additional forcing from dust aerosols, the dust increases the shortwave planetary albedo, reducing energy inputs to the surface and the planetary boundary layer. This energy deficit increases atmospheric stability, inhibiting vertical movement and convection and reducing cloud cover and precipitation over the Central Plains. Droughts simulated in our scenario with dust aerosols have significantly longer persistence than our other model experiments, matching the autocorrelation structure of tree ring reconstructed drought variability. Results from this study provide the first model based evidence that dust aerosol forcing and land surface changes can explain the persistence of the MCA megadroughts, although uncertainties remain in the formulation of the boundary conditions and the future importance of these feedbacks as western North America moves into an anthropogenically warmer and drier world.
Jan. 25Ning LinMITHurricane Surge and Global Warming: Physically-based Risk Assessment
Hurricanes present major hazards for the United States and many other areas. Due to rising sea level and possibly increasing storm intensity, hurricane impact is likely to be more severe in the future, affecting a significant percentage of the world population in rapidly developing coastal regions. We develop physically-based risk assessment methods to study hurricane weather extremes, how they change with climate, and how to minimize their impact. This talk focuses on hurricane storm surge. We introduce a surge risk assessment method, which couples a General Circulation Model (GCM)-driven statistical/deterministic hurricane model with hydrodynamic models to simulate large numbers of synthetic surge events and predict surge risk under different climates. It considers the effects of the astronomical tide, wave setup, and sea-level rise (SLR). The method is applied, as an example, to New York City (NYC). Struck by many intense hurricanes in recorded history and prehistory, NYC is highly vulnerable to storm surge. We show that the surge level for NYC will likely increase due to the change of storm climatology, with a magnitude comparable to the projected SLR. The combined effects of storm climatology change and SLR may greatly shorten the surge flooding return periods in the future.
Jan. 26Scott DoneyWHOICarbon Cycle Dynamics in the Community Earth System Model (CESM-1)
Carbon Cycle Dynamics in the Community Earth System Model (CESM-1)
Feb. 2Trude StorelvmoYaleAerosol Effects on Cloud Thermodynamic Phase
Aerosol Effects on Cloud Thermodynamic Phase
Feb. 8Graham HughesAustralia National UniversityStratified mixing processes and the energetics of the global ocean circulation
Stratified mixing processes and the energetics of the global ocean circulation
Feb. 9Jeroen TrompPrinceton UniversitySeismic imaging based on spectral-element and adjoint methods
By taking advantage of modern numerical methods and harnessing large parallel computers, the simulation of seismic wave propagation in realistic 3D Earth models has become feasible. Such "forward" simulations require hundreds of processors and many CPU hours. The challenge lies in harnessing these new-found forward modeling capabilities to enhance the quality of images of Earth's interior, i.e., to address the "inverse" problem. By drawing connections between seismic tomography, adjoint methods popular in climate and ocean dynamics, and time-reversal imaging used in the petroleum industry, one iteration in tomographic inversions may be performed based on just two numerical simulations for each earthquake: one calculation for the current model and a second adjoint calculation that uses time-reversed signals at the receivers as simultaneous, fictitious sources. This has finally opened the door to solving the 3-D inverse problem. Our current application involves "adjoint tomography" of the European crust and upper mantle.
Feb. 15Syukuro ManabePrincetonRelationship among Sea Surface Temperature, Rainfall and Cyclones in the Tropics
Looking back the modeling studies of tropical circulation that we conducted at GFDL during the 1960's and early 1970's, I would like to explore the dynamical relationship among sea surface temperature, tropical cyclones, and rainfall. The studies use an atmospheric GCM, which incorporates a very simple parameterization of deep moist convection called saturated convective adjustment. It was very encouraging, however, that the model yielded realistic distribution of rainfall and that of tropical cyclones in the tropics. Finally, I discuss the influence of global warming upon tropical circulation (e.g., Walker Circulation, ENSO and tropical cyclone), based upon the several modeling studies that were conducted in 1990's using a coupled ocean-atmosphere GCM.
Feb. 16Ken CaldeiraStanfordGeoengineering Earth's climate
Greenhouse gases from human activities continue to accumulate in the atmosphere causing the Earth to get hotter and hotter. Independent of what we might desire, there is little strong evidence that these trends will change substantially any time soon. Volcanic eruptions have shown us that small particles in the stratosphere can cool the Earth rapidly. Engineering analyses suggest that the direct cost of emplacing such particles in the stratosphere would be approximately one ten-thousandth of global GDP -- essentially in the noise of the global economy. Climate models suggest that such emplacement would eliminate most climate change for most people most of the time. Results of such climate model simulations will be presented. Discussion of this topic is often polarizing, with the mainstream generally considering these ideas crazy and unwise. The desire to consider these options seems strongest at the two ends of the spectrum, with some environmentalists feeling that protection of Arctic and other ecosystems depends on this kind of drastic action in addition to redoubling efforts to reduce greenhouse gas emissions, and with some more business-minded folks thinking that these strategies should be developed as emergency back-up measures in lieu of serious efforts to reduce greenhouse gas emissions. This talk will discuss what is understood scientifically about some geoengineering proposals to counteract some of the effects of high concentrations of greenhouse gases in the atmosphere, and place this scientific knowledge in a broader political and environmental context.
Feb. 22Rym MsadekGFDL/UCARTBA
TBA
Feb. 23Minghua ZhangStony Brook University/SUNYThe CGILS Project to Understand the Physical Mechanism of Climate Feedbacks from Low Clouds
The CGILS Project to Understand the Physical Mechanism of Climate Feedbacks from Low Clouds
Feb. 29Martin SchmidtBaltic Sea Research Institute, GermanyOxygen minimum zones in the eastern boundary currents of the Southern Atlantic - a model view
Oxygen minimum zones in the eastern boundary currents of the Southern Atlantic - a model view
Mar. 1David RompsUniversity of Claifornia, BerkeleyMaking sense of clouds with the Trasilient Matrix
Making sense of clouds with the Trasilient Matrix
Mar. 7Yi MingGFDLThe seasonality of Arctic air pollution: A "dynamicist"'s view
The seasonality of Arctic air pollution: A "dynamicist"'s view
Mar. 8Zhiming KuangHarvardTropical convection, waves, and climate
Tropical convection, waves, and climate
Mar. 14Zack SubinU of C, BerkeleyInteractions of Water and Energy Mediate Permafrost Climate Feedbacks
Interactions of Water and Energy Mediate Permafrost Climate Feedbacks
Mar. 15Elizabeth HunkeLos Alamos National LabSea ice in global climate models
Sea ice in global climate models
Mar. 21Stefan TulichCIRES Dependence of convectively coupled tropical waves on
Dependence of convectively coupled tropical waves on the basic state
Mar. 22Doug MacAyealU of ChicagoIce-Shelf Disintegration: Break-Up Processes and Climate Drivers
Ice-Shelf Disintegration: Break-Up Processes and Climate Drivers
Mar. 28Jingqiu MaoAOS/GFDLRadical loss in the atmosphere by Cu-Fe redox coupling in aerosols
Radical loss in the atmosphere by Cu-Fe redox coupling in aerosols
Mar. 29Lai-Yung (Ruby) LeungPacific Northwest National LaboratoryDevelopment of Framworks for Robust Regional Climate Modeling
Development of Framworks for Robust Regional Climate Modeling
Apr. 4Gabriel VecchiGFDLTropical Changes in the 21st Century Projections from CMIP5: Roles of Greenhouse and Non-greenhouse forcing
Tropical Changes in the 21st Century Projections from CMIP5: Roles of Greenhouse and Non-greenhouse forcing
Apr. 5Kristie BoeringUC - BerkeleyTop-down and Bottom-Up: The isotopic composition of atmospheric nitrous oxide since 1940
Top-down and Bottom-Up: The isotopic composition of atmospheric nitrous oxide since 1940
Apr. 11Michael WintonGFDLChanging currents and changing climate
Changing currents and changing climate
Apr. 12Phil RaschPNNLExploration of aerosol, cloud and dynamical feedbacks in the climate-cryosphere system
I will describe some of our recent studies on factors influencing arctic climate. This will include a discussion of some some biases in aerosol simulations seen in our model (and and many other climate models). I will discuss the role of these biases in influencing Arctic clouds, and climate, and our successful attempt to reduce the biases by changing aerosol aging and cloud processing of the aerosol. Reducing the bias has a measurable impact on aerosols, and cloud distributions, and on aerosol deposition on snow and ice, primarily in the Arctic and mid- and upper-troposphere. These improvement have possible consequences for the aerosol indirect effect, and climate sensitivity. I will briefly outline some of our other studies on the role of the Arctic Oscillation in the transport of black carbon to high latitudes, and attempts to tease out the role of various forcing mechanisms (local radiative forcing, atmospheric and oceanic heat transports) in changing Arctic Ice extent
Apr. 25Tony Rosati & X. YangGFDLDecadal Climate Prediction at GFDL
Decadal Climate Prediction at GFDL
Apr. 26Steve FrolkingU of New HampshirePeatlands in the 21st century climate system - state of knowledge and a modelling perspective
Peatlands occupy 3% of the Earth's land area, but they are a globally important carbon store because of their high carbon density. Undisturbed peatlands are currently a weak CO2 sink (~0.1 Pg C y-1), a moderate source of CH4 (~0.03 Pg CH4 y-1), and a very weak source of N2O (~0.00002 Pg N2O-N y-1). Anthropogenic disturbance, primarily agriculture and forestry drainage of 10%-20% of global peatlands, likely changes the global peatland greenhouse gas balance to a CO2 source (~0.1 Pg C y-1), and a larger (but still small) N2O source (~0.0004 Pg N2O-N y-1). There is no strong evidence that peatlands significantly contributed to 20th century changes in the atmospheric burden of CO2, CH4, or N2O; will this picture change in the 21st century? The main global change impacts on peatlands that may have significant climate impacts are (1) intentional drainage, especially in the tropics; (2) widespread permafrost thaw; and (3) increased fire intensity and frequency as a result of drier climatic conditions and/or drainage. Quantitative estimates are limited by sparse field data (particularly in the tropics), the large variability present in existing data, uncertainties in the future trajectory of peatland use, interactive effects of individual impacts, and the unprecedented rates of climate change expected in the 21st century.
May. 10Louis St. LaurentWHOITurbulence and Mixing in the Drake Passage
Turbulence and Mixing in the Drake Passage
May. 16Larry HorowitzGFDLHistorical and future climate change simulated by GFDL's CM3 coupled model
Historical and future climate change simulated by GFDL's CM3 coupled model
May. 23Dr. Andreas Schiller The Bluelink Ocean Forecasting System CSIRO Marine and Atmospheric Research Hobart, AUSAn overview of the Bluelink ocean forecasting system
An overview of the Bluelink ocean forecasting system
May. 23Xujing Jia DavisWHOILocal Oceanic Response to Atmospheric Forcing in the Gulf Stream Region
Local Oceanic Response to Atmospheric Forcing in the Gulf Stream Region
May. 30Hiram LevyGFDLAir Pollution (primarily aerosols) and Climate Change: From CM2.1 to CM3
Air Pollution (primarily aerosols) and Climate Change: From CM2.1 to CM3
May. 31Ann FridlindGISSStudies of low-lying Arctic clouds: Learning fundamentals of mixed-phase cloud physics from a persistent element of polar climate
Studies of low-lying Arctic clouds: Learning fundamentals of mixed-phase cloud physics from a persistent element of polar climate
Jun. 6Dr. Kushnir and SeagerLDEOTopics in LDEO decadal climate research: Impacts of ozone depletion on the hydrological cycle; Centennial tropical Pacific variability in coupled GCMs (including GFDL CM2.1); The recent multi-decadal drying of the Mediterranean region.
Topics in LDEO decadal climate research: Impacts of ozone depletion on the hydrological cycle; Centennial tropical Pacific variability in coupled GCMs (including GFDL CM2.1); The recent multi-decadal drying of the Mediterranean region
Jun. 7Claudia CenedeseWHOIDownwelling in Basins Subject to Buoyancy Loss
Recent observational, theoretical, and modeling studies all suggest that the upper part of the downwelling limb of the thermohaline circulation is concentrated in strong currents subject to buoyancy loss near lateral boundaries. This is fundamentally different from the traditional view that downwelling takes place in regions of deep convection. Even when resolving the buoyant boundary currents, coarse resolution global circulation and climate models rely on parameterizations of poorly known turbulent mixing processes. In this study, the first direct measurements of downwelling occurring within a basin subject to buoyancy loss are obtained. Downwelling is observed near the basin's vertical wall within the buoyant boundary current flowing cyclonically around the basin. Although the entire basin is cooled, large-scale mean downwelling is absent in the basin interior. Laboratory rotating experiments are conducted to explicitly resolve the turbulent mixing due to convective plumes, the baroclinic eddies generated by the boundary current, and identify where downwelling takes place. Small vertical velocities can be measured more reliably in the laboratory than in many numerical calculations, while the measurement of these small vertical velocities is still a challenge for field experiments. Downwelling is observed near the vertical wall within a boundary layer with a thickness that scales with the baroclinic Rossby radius of deformation, consistent with the dynamical balance proposed by a previous numerical study. Hence, downwelling in the Labrador Sea and Lofoten Basin cyclonic boundary currents may be concentrated in a baroclinic Rossby radius of deformation thick boundary layer in regions with large eddy generation.
Jun. 13Steve BrownESRLNighttime oxidation of biogenic hydrocarbons
Nighttime oxidation of biogenic hydrocarbons
Jun. 14Ben SanterLLNLIdentifying Human Influences on Atmospheric Temperature: Are Results Robust to Current Uncertainties?
We perform a multi-model detection and attribution ("D&A") study with changes in atmospheric temperature. The observations are satellite estimates of tropospheric and stratospheric temperature change. Climate model estimates of atmospheric temperature change were obtained from phase 5 of the Coupled Model Intercomparison Project (CMIP-5). The CMIP-5 geographical patterns of externally-forced changes in atmospheric temperature ("fingerprints") are identifiable with high statistical confidence in all currently-available observed data sets. For stratospheric temperature changes over 1979 to 2011, the similarity between the searched-for fingerprint and observations increases over time, and signal-to-noise (S/N) ratios invariably exceed 15. In the troposphere, the fingerprint strength in observations is lower, but S/N ratios are still highly significant (>3), even in a satellite data set which until recently showed relatively muted tropospheric warming. This fingerprint match between models and observations occurs because of common hemispheric-scale asymmetry in the patterns of atmospheric temperature change. Our results provide clear scientific evidence for a discernible human influence on global climate, and are robust to current uncertainties in the searched-for fingerprint, model estimates of climate noise, the observations, and choices made in the application of the D&A method.
Jun. 20Kathie KellyUniversity of Washington, Applied Physics LaboratoryThe Coherence and Impact of Meridional Heat Transport Anomalies in the Atlantic Ocean Inferred from Observations
Observations of thermosteric sea level (TSL) from hydrographic data, equivalent water thickness (EWT) from satellite gravity data, as well as altimetric sea surface height (SSH) anomalies, are used to construct budgets of heat and mass for the Atlantic Ocean from 31S to 64N and to infer changes in the meridional heat transport (MHT). The time-varying budgets are forced by surface heat and freshwater flux anomalies; discrepancies between the modeled response to surface fluxes and observed mass and heat content are used to infer lateral heat and mass convergences. The "unknown control" version of a Kalman filter is employed to extract smoothed budget terms and a smooth residual in each of several regions, given reasonable estimates of model and data errors. Regional convergences are then summed to estimate meridional heat transports for 1993-2010. The analysis reveals that MHT is coherent between 31S and the separated Gulf Stream and that positive anomalies in MHT correspond to increased heat loss in the subtropical gyre. The inferred MHT reproduces a recent drop and subsequent reversal seen in the RAPID/MOCHA observations at 26.5N and shows previous large anomalies. An intensification of MHT anomalies in the South Atlantic and a correlation of MHT with the Antarctic Oscillation suggests a southern source for MHT anomalies.
Jun. 21Joel NorrisUCSDRecent Progress in Understanding Clouds and Climate Change
Recent Progress in Understanding Clouds and Climate Change
Jun. 27Bill SternImpact of Resolution, Parameterization and Coupling on the representation of Tropical ISOs in GCMs at GFDL / Plus: A Weather Balloon Adventure
Impact of resolution, parameterization and coupling on the representation of tropical intraseasonal activity in GCMs at GFDL
Jul. 12Pu LinU of WashingtonUnderstanding the stratospheric circulation changes in the Southern Hemisphere
Understanding the stratospheric circulation changes in the Southern Hemisphere
Jul. 23V. RamanathanScripps Institution of OceanographyShort Lived Climate Pollutants: A Second Front in Climate Change Mitigation
Short Lived Climate Pollutants: A Second Front in Climate Change Mitigation
Jul. 23V. RamanathanScripps Insitute of OceanographyRoundtable
Discussion
Jul. 25Dr. Paula GonzalezColumbia-International Research InstituteImpact of the 20th Century ozone depletion on increasing precipitation in South Eastern South America
It has been shown that ozone depletion and the subsequent generation of the Antarctic ozone hole have been significant drivers of the observed climate change in the Southern Hemisphere (i.e., Polvani et al., 2011). In particular, these processes have contributed to a wetting of the subtropics of the SH in the later part of the 20th Century (i.e., Kang et al., 2011). This talk concentrates on finding evidences of the impact of ozone depletion on the increasing precipitation in South Eastern South America (SESA), which is a region that has exhibited one of the largest wetting trends during the 20th Century. A hierarchy of 6 different numerical experiments has been used to explore such impacts and has consistently revealed that ozone depletion has significantly contributed to the wetting of SESA in the period 1960-1999. In addition, the results indicate that such contribution is of the same relevance or even more important than that related to changes in GHGs.
Jul. 25Lisa GoddardColumbia-International Research InstituteMulti-scale Climate Information for Agricultural Planning in Southeastern South America for Coming Decades
Agricultural expansion in the Southern Cone of South America has increased drastically since 1990 due in part to increased annual precipitation over regions traditionally considered semiarid. Agricultural decision makers in this region desire reliable decadal-scale outlooks for planning and management, but none exist currently. The sectoral and regional context serves as a test bed for the development of decadal climate information. This talk will describe the research by which we plan to build up climate information across timescales. These include (1) Investigation of climate changes in the recent past, including attribution of the causes of that change, and probabilistic estimates of how climate may change in future decades due to natural variability and radiatively-forced change. (2) Design of prototype climate information appropriate to agriculture on the 10-20 year time horizon. (3) Assessment of agricultural vulnerabilities to climate variability and change and development of adaptive management strategies to increase resiliency. This climate information across timescales is being investigated and developed using state-of-the-art tools, including dynamical model climate change projections, initialized decadal predictions, idealized atmospheric model experiments, and high resolution regional downscaling to resolve dynamical processes and the changing characteristics of weather transients. Historical climate observations are incorporated in the diagnostic analyses of the past and will inform statistical techniques applied to predictions of the future. The observed, simulated, and predicted/projected climate information will be applied to a crop model to assess the vulnerability of agricultural lands to predicted climate changes, and to test possible strategies for mitigating the vulnerability.
Jul. 26Carlos GaitanU of British ColumbiaComparison of statistical downscaling methods for future weather and climate
Statistical downscaling (SD) of global climate model output assumes that the SD skill in present climate is retained in future climate. To check this assumption, we used regional climate model output as pseudo-observations to verify the SD model's performance in terms of both weather and climate of extremes for historical (1968-2000) and future (2038-2070) periods. Nonlinear Bayesian neural network and multiple linear regression models were used to downscale the Canadian Global Climate Model 3.1 output using the Canadian Regional Climate Model 4.2 (daily maximum and minimum temperature) output as pseudo-observations in southern Ontario and Quebec, Canada. The results indicate that choosing the best model based on performance in the historical period could result in having one of the worst models for the future period. Using SD models with greater ability to model complicated relations, by having either nonlinear capability or additional non-temperature predictors, seemed to alleviate the drop in performance found in future climate conditions.
Jul. 27Chun-Chieh WuNational Taiwan UniversityA New Paradigm for Secondary Eyewall Formation in Tropical Cyclones
A New Paradigm for Secondary Eyewall Formation in Tropical Cyclones
Jul. 27GFDLEAGFDLDiscussion
Discussion
Aug. 1Chris GolazGFDLTBA
TBA
Aug. 2Frank LiJPLCharacterizing and Understanding Cloud Water and Radiation Budget Biases in CMIP3/CMIP5 GCMs, Contemporary GCMs and Reanalyses
shortwave (RSUT) and outgoing longwave (RLUT) fluxes at the top of the atmosphere (TOA) that are directly influenced by cloud/convection from the 20th century Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations and compare these results to the same analysis on CMIP3 (CMIP Phase 3) as well as from the NASA GMAO GEOS5 atmospheric global climate model (GCM). A number of contemporary satellite measurements and derived products are used for the TOA fluxes (CERES-EBAF and CloudSat) and observationally constrained model calculations for the surface flux (e.g. EBAF-Surface product, ISCCP and CloudSat product), with quantified uncertainties, for comparison to the GCMs. The results show that a majority of the GCMs considered in this study have significant local biases in the annual mean of the radiative fluxes considered (i.e. RSDS, RLUT, and RSUT) with the bias values ranging from -30 to 30 Wm-2. The ensemble behavior of CMIP5 has improved considerably relative to CMIP3 in terms of bias, but neither the CMIP5 ensemble mean nor any individual model performances indicate progress in terms of root-mean square error (RMSE) evaluations. There are still a number of models as well as multi-model mean that exhibit very large regional biases despite the efforts of model progress and availability of relevant radiation and cloud observations in the past few years since CMIP3. In general, the CMIP5 ensemble of models displays no differences in cloud field simulation variability from the CMIP3 ensemble when considering the Taylor Plot framework. Persistent and systematic biases across most of the models and the model ensemble means are underestimated RSUT, overestimated RSDS and RLUT which are consistent to the underestimated cloud ice and liquid water contents in the extra-tropics and storm tracks and significantly underestimated cloud water contents in tropical convective active regions over ITCZ/SPCZ, Warm Pool, Indian Monsoon as well as South America, Central Africa. The systematic biases of the RSDS, RLUT and RSUT are in phase with the maximum precipitation regions in the tropics, suggesting that at least a part of this persistent bias stems from GCMs ignoring the effects of precipitating and/or convective core ice and liquid in their radiation calculations. The systematic biases in RLUT, RSDS and RSUT also exist in GFDL CM3 but the model largely outperforms the other GCMs. This might be due to the abilities of the GFDL model to represent and output both cloudy, precipitating ice and convective profiles and to perform a more realistic radiation simulation, combined with the observational capabilities to roughly distinguish these types of ice mass, provide an additional means for constraints on the model physics. As a better approach, rather than revising the current cloud parameterizations of the conventional GCMs, we suggest in a GCM that the model explicitly treats at least four hydrometeor species (cloud water, cloud ice, rain and snow) and their interactions with radiation as well as includes convective cloud mass with realistic microphysical and detrainment properties, to improve the mid- and low-level cloud fraction over the convectively active regions such as ITCZ/SPCZ and subtropical oceans which would help to rectify the positive RSDS and RLUT biases and the negative RSUT bias evident in the CMIP3/CMIP5 models analyzed here.
Aug. 21Laura JacksonHadley Centre - Met Office, U. K.The Atlantic Meridional Overturning Circulation in HadCM3 and a multithousand member perturbed physics ensemble - projections and stability
The Atlantic Meridional Overturning Circulation in HadCM3 and a multithousand member perturbed physics ensemble - projections and stability
Aug. 22John KrastingGFDLENSO-driven Interannual Carbon Flux Variability in GFDL's Earth System Models
ENSO-driven Interannual Carbon Flux Variability in GFDL's Earth System Models
Sep. 12Shang-Ping XieU. Hawaii/IPRCRegional patterns of climate change in global warming
Regional patterns of climate change in global warming
Sep. 13RamachandranPRL, India, currently on sabbatical at NASA-AmesSeasonal variations, Mixing and Radiative Forcing of Black Carbon
Seasonal variations, Mixing and Radiative Forcing of Black Carbon
Sep. 19Tom DelworthGFDLA review of mechanisms for decadal to centennial variability of the Atlantic Meridional Overturning Circulation as seen in climate models
A review of mechanisms for decadal to centennial variability of the Atlantic Meridional Overturning Circulation as seen in climate models
Sep. 25V. Balaji and Tom DelworthGFDLA special briefing seminar
The National Research Council has recently released a report "A National Strategy for Advancing Climate Modeling". This report carries a lot of significance and context for the climate modeling work that we do at GFDL. Two of the members of the Panel that prepared the report were V. Balaji and Tom Delworth. They have kindly agreed to give us all a briefing on the principal contents of the report. A special briefing seminar by Balaji and Delworth will take place on September 25 (Tuesday) starting at Noon in the Smagorinsky Seminar Room.
Sep. 26Jorge SarmientoP. U.Overview presentation on Southern Ocean Biogeochemical observations and modeling program
Overview presentation on Southern Ocean Biogeochemical observations and modeling program
Sep. 27Jennifer MacKinnonScripps Insitute of OceanographyDiapycnal mixing in the ocean: patterns, processes, and peculiarities
Diapycnal mixing in the ocean: patterns, processes, and peculiarities
Oct. 3Michael GhilEcole Normale Supérieure, Paris, and University of California, Los AngelesToward an NAO Theory: Observations, Theories and Simulations
Toward an NAO Theory: Observations, Theories and Simulations
Oct. 4Heidi CullenClimate CentralSeeing Climate, Seeing Change: The role of social and decision sciences in communicating uncertain environmental risks
Seeing Climate, Seeing Change: The role of social and decision sciences in communicating uncertain environmental risks
Oct. 10Shaoqing ZhangGFDLParameter Estimation in Coupled Models: Opportunities and Challenges
Parameter Estimation in Coupled Models: Opportunities and Challenges
Oct. 11Robert KoppRutgersInterpreting the noisy geological record of ancient sea level changes
Interpreting the noisy geological record of ancient sea level changes
Oct. 17Jacob SchewePotsdam Institute for Climate Impact Research, GermanyMore frequent future monsoon failure due to inherent instability
Indian monsoon rainfall is vital for a large share of the world's population. Both reliably projecting India's future precipitation and unraveling abrupt cessations of monsoon rainfall found in paleorecords require improved understanding of its stability properties. We show that in a comprehensive climate model, monsoon failure is possible but very rare under pre-industrial conditions, while under future warming it becomes much more frequent. We identify the fundamental intraseasonal feedbacks that are responsible for monsoon failure in the climate model, relate these to observational data, and build a statistically predictive model for such failure. Thereby we provide a simple dynamical explanation for future changes in the frequency distribution of seasonal mean all-Indian rainfall. Forced only by global mean temperature and the strength of the Pacific Walker circulation in spring, the simple model reproduces the future trend as well as the multi-decadal variability in seasonal monsoon rainfall, as found in the climate model. The approach offers a novel perspective on large-scale monsoon variability as the result of internal instabilities modulated by pre-seasonal ambient climate conditions.
Oct. 18Jonathan Jiang and Hui SuJet Propulsion Lab, Pasadena, CAEvaluation and Regime-dependent Error Diagnosis of Cloud and Water Vapor Simulations in Climate Models Using NASA A-Train Satellite Observations
Using NASA "A-Train" satellite observations, we evaluate the accuracy of cloud water content (CWC) and water vapor mixing ratio (H2O) outputs from ~20 climate models submitted to the CMIP5, and assess improvements relative to their counterparts for the earlier CMIP3. We find more than half of the models show improvements from CMIP3 to CMIP5 in simulating column-integrated cloud amount, while changes in water vapor simulation are insignificant. For the CMIP5 models, the model spreads and their differences from the observations are much larger in the upper troposphere than in the lower or middle troposphere. Numerical scores are used to compare model performances in regards of to spatial mean, variance and distribution of CWC and H2O over the tropical oceans. Model performances at each pressure level are ranked according to the average of all the relevant scores for that level. We further developed a diagnostic framework to decompose the cloud simulation errors into the large-scale errors, cloud parameterization errors and co-variation errors. We find that the cloud parameterization errors contribute predominantly to the total errors for all models.
Oct. 22CEREES Science Team MeetingGFDLCEREES Science Team Meeting
CEREES Science Team Meeting
Oct. 23CEREES Science Team MeetingGFDLCEREES Science Team Meeting
CEREES Science Team Meeting
Oct. 24CEREES Science Team MeetingGFDLCEREES Science Team Meeting
CEREES Science Team Meeting
Oct. 25CEREES Science Team MeetingGFDLCEREES Science Team Meeting
CEREES Science Team Meeting
Nov. 1Vernon Morris Howard UniversityA Summary of Research Findings from the Saharan dust AERosols and Ocean Science (AEROSE) Campaigns (2004-2011)
Howard University has lead a series of maritime field experiments supporting research and observations of the microphysical characteristics (optical properties, surface characteristics, chemical composition, deposition rates, and size- & mass distributions) of mineral dust aerosols and their impact on the marine troposphere annually since 2004. These are known as the AERosols and Ocean Science Expeditions or AEROSE. The AEROSE project is a comprehensive interdisciplinary mission that returned multiple, high quality, and unique data sets. The majority of the missions (seven of the past eight) and the upcoming 2013 cruise) are conducted aboard the NOAA Ship Ronald H. Brown. These activities involve comprehensive trace gas and aerosol monitoring and aerosol collection including observations of mineral dust microphysics, optical properties, and chemical impacts on the regional and global atmosphere. Howard University teams also participate in continuous monitoring stations (El Paso, Texas and Isla Magueyes, Puerto Rico), at-sea investigations of short and long duration and execute field intensives in collaboration with NOAA and other partners. These field programs are excellent student training opportunities and generate data sets that can be utilized for improvement of model parameterizations in weather, climate, & air quality forecast models, for satellite validation, and for the improvement of retrieval algorithms (Morris et al 2006, Nalli et al 2011). A survey of the results and analysis from the AEROSE campaign will be presented. In particular,insights pertaining to the mass distribution dynamics and surface composition will be highlighted.
Nov. 7Fabien Roquet Stockholm University, SwedenToward a new approach to Ocean Energetics: introducing the concept of Dynamical Potential Energy
The concept of Available Potential Energy is supposed to indicate which part of the Potential Energy is available to transform into Kinetic Energy. Yet it is impossible to obtain a unique definition of Available Potential Energy for the real ocean due to nonlinearities of the equation of state, rendering its usefulness largely hypothetical. In this presentation, we will see how the energy conservation for a stably stratified ocean can be reformulated in terms of horizontal anomalies of density and pressure. The concept of Dynamical Potential Energy will be introduced, defined as the horizontal anomaly of Potential Energy. Modified conservation equations will be presented that make it much simpler to identify oceanic power input by buoyancy and mechanical forces. Finally, closed budgets of energy will be presented for idealized circulations obtained with a general circulation model, comparing spatial patterns of power inputs generated by wind and thermal forcings.
Nov. 8Randal KosterNASAIdentifying and Evaluating the Relationships that Control a Land Surface Model's Hydrological Behavior
The inherent soil moisture-evaporation relationships used in today's large-scale land surface models (LSMs) arguably reflect substantial guesswork given the unavailability of contemporaneous evaporation and soil moisture observations at the spatial scales represented by regional and global models. The inherent soil moisture-runoff relationships used in the LSMs are also of uncertain accuracy. Evaluating these relationships is difficult but crucial given that they have a major impact on how the land component contributes to hydrological and meteorological variability within a simulated climate system. The relationships, it turns out, can be examined efficiently and effectively with a simple water balance model framework. The simple water balance model, driven with multi-decadal observations covering the conterminous United States, shows how different prescribed relationships lead to different manifestations of hydrological variability, some of which can be compared directly to observations. Through the testing of a wide suite of relationships, the simple model provides estimates for the underlying relationships that operate in nature and that should be operating in LSMs. We examine the relationships currently used in a number of different LSMs in the context of the simple water balance model results and make recommendations for potential first-order improvements to these LSMs.
Nov. 14Charles StockGFDLGlobal-scale carbon and energy flows through the planktonic food web: an analysis with a coupled physical biological model
Global-scale carbon and energy flows through the planktonic food web: an analysis with a coupled physical biological model
Nov. 15Oliver BuhlerNYURandom and deterministic ocean mean flows created by internal waves
Random and deterministic ocean mean flows created by internal waves
Nov. 28Rachel LickerWoodrow Wilson School at PrincetonAssessing Global and Regional Crop Yield Patterns: An Integration of Biophysical and Social Drivers
Assessing Global and Regional Crop Yield Patterns: An Integration of Biophysical and Social Drivers
Nov. 28Yuxing YunUniversity of Michigan"Global modeling study of aerosol indirect effects in mixed-phase clouds"
"Global modeling study of aerosol indirect effects in mixed-phase clouds"
Nov. 29Drew T. ShindellNASA-GISSInsights into the relationship between regional radiative forcing and climate response
While forcings such as those due to increasing greenhouse gases or changing solar irradiance are relatively uniform geographically, forcing by aerosols, ozone and land-use are highly inhomogeneous. This talk will explore some recent analysis attempting to better understand how this uneven distribution of forcing affects climate response. I will discuss results from simulations with the GISS GCM driven by localized regional forcings that help indicate how temperature and precipitation response is affected by both the type and location of forcing. Using GISS CMIP5 simulations driven by single forcing agents, I will then examine how the various agents affect the response of particular regional climate features including the location of the ITCZ and the rate of Southern Ocean overturning. Finally, results from a larger set of the new generation of CMIP5/ACCMIP composition-climate models will be examined to see how the response to highly inhomogeneous forcing compares with the response to greenhouse gas forcing and to evaluate the robustness of the regional forcing/response relationships across the models.
Dec. 13Ilya V. BuynevichTemple UniversityWritten in Sand: Geological Archives of Extreme Coastal Events
Written in Sand: Geological Archives of Extreme Coastal Events