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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.

June 19, 2019

calendar_today EDGI: Simple Machine Learning for Geoscience at the GFDL

person Lunchtime Seminar - Lunchtime Seminar Series - Chris Dupuis (GFDL)

access_time 12:00 pm - 1:00 pm

place Location: Smagorinsky Seminar Room

Machine learning is often mystified in science fields, even when the basic scientific needs are relatively straightforward. We present an aggressively simple prototype command-line tool developed at the GFDL that combines principal component analysis with single-node parallelism, automatic NetCDF I/O, and a variety of basic and specialized flavors. Standard PCA with real- and complex-valued data, PCA of real-valued circular data, PCA of analytic singals, and PCA with multiple variables will be demonstrated. Further, new developments in C++ permit automatic parallelization of array-based statistics, which will inform first full-fledged version of EDGI PCA and a planned ensemble consistency test for the GFDL model.

June 20, 2019

calendar_today Ocean modelling for seamless prediction: resolution and process representation

person Formal Seminar (approved) - Formal Seminar - Helen Hewitt (UK Met Office)

access_time 2:00 pm - 3:00 pm

place Location: Smagorinsky Seminar Room

Ocean model configurations developed by the Met Office (and partners) are utilised for applications from short-range ocean forecasting to climate projections ('seamless prediction'). The opportunities as well as the challenges and conflicting requirements of the seamless approach are described. The choice of ocean model resolution is discussed including the need to provide evidence to support the additional computational and storage costs of higher resolution. Alongside enhanced resolution, improved process representation in the model configurations is also a target and current efforts to improve overflows and convection are described.

June 26, 2019

calendar_today Tropical Cylones and Climate Change: An Assessment Report

person Lunchtime Seminar - Lunchtime Seminar Series -Tom Knutson

access_time 12:00 pm - 1:00 pm

place Location: Smagorinsky Seminar Room

An assessment was made of whether detectable changes in tropical cyclone (TC) activity are identifiable in observations and whether any changes can be attributed to anthropogenic climate change. Overall, historical data suggest detectable TC activity changes in some regions associated with TC track changes, while data quality and quantity issues create greater challenges for analyses based on TC intensity and frequency. A number of specific published conclusions (case studies) about possible detectable anthropogenic influence on TCs were assessed using the conventional approach of preferentially avoiding Type I errors (i.e., overstating anthropogenic influence or detection). We conclude there is at least low-to-medium confidence that the observed poleward migration of the latitude of maximum intensity in the western North Pacific is detectable, or highly unusual compared to expected natural variability. Opinion on the author team was divided on whether any observed TC changes demonstrate discernible anthropogenic influence, or whether any other observed changes represent detectable changes. We also assessed published detection and attribution findings from a Type II error avoidance perspective, and presented summaries of future TC projections for a 2 degree Celsius global warming.

July 8, 2019

calendar_today Interannual-decadal variability and predictability over the South Atlantic and southern Indian Oceans

person Informal Seminar - Informal Seminar - Yushi Morioka (JAMSTEC/VAiG/APL, Yokohama, Japan)

access_time 2:00 pm - 3:00 pm

place Location: Smagorinsky Seminar Room

Interannual-decadal sea-surface temperature (SST) variability in the South Atlantic and southern Indian Oceans has great influences on regional rainfall variability over the southern Africa through modulation of moisture transport. The Interannual SST variability, so called “Subtropical Dipole” which is characterized by a meridional dipole pattern of SST anomalies in each basin, is induced by ocean mixed-layer thickness variability associated with subtropical high variability. A series of climate model experiments reveals that besides remote forcing such El-Niño Southern Oscillation (ENSO) and the Southern Annular Mode (SAM), sea-ice extent variability over the Weddell Sea has a potential to influence the atmospheric variability over the South Atlantic. On a decadal timescale, the SST variability over the South Atlantic tends to propagate eastward as quasi-stationary oceanic Rossby waves under the influence of the Antarctic Circumpolar Current (ACC) and induce the decadal SST variability over the southern Indian Ocean. Decadal reforecast experiments with different ocean initial conditions show that the decadal SST variability over the South Atlantic (southern Indian Ocean) is predictable when the model's SST, subsurface ocean temperature and salinity are initialized (only the model's SST is initialized).

July 19, 2019

calendar_today A parameterization of local and remote tidal mixing

person Informal Seminar - Informal Seminar - Casimiar de Lavergne (CNRS, LOCEAN Laboratory, Sorbonne University, Paris)

access_time 10:30 am - 11:30 am

place Location: Smagorinsky Seminar Room

Internal tides power much of the observed small-scale turbulence in the ocean interior. To represent mixing induced by this turbulence in climate-scale ocean models, energy routes from the generation to the dissipation of internal tides must be understood and mapped. Here we present a mixing scheme which accounts for the local breaking of high-mode internal tides and the distant dissipation of low-mode internal tides. The scheme relies on four static 2D maps of internal tide dissipation, constructed using mode-by-mode Lagrangian tracking of energy beams from sources to sinks. Each map is associated with a distinct dissipative process and a corresponding vertical structure. Applied to an observational climatology of stratification, the scheme produces a global 3D map of dissipation and mixing which compares well with available microstructure observations and with upper-ocean fine-structure mixing estimates. Implemented in the NEMO global ocean model, the scheme improves the representation of deep water-mass transformation and obviates the need for a fixed background diffusivity.

July 24, 2019

calendar_today Tropical Atmospheric Madden-Julian Oscillation: Strongly-Nonlinear Free Solitary Rossby Wave?

person Lunchtime Seminar - Lunchtime Seminar Series - Jun-Ichi Yano (Meteo France, Toulouse)

access_time 12:00 pm - 1:00 pm

place Location: Smagorinsky Seminar Room

The Madden-Julian oscillation (MJO), a planetary-scale eastward propagating coherent structure with periods of 30-60 days, is a prominent manifestation of intraseasonal variability in the tropical atmosphere. It is widely presumed that small-scale moist cumulus convection is a critical part of its dynamics. However, the recent results from high-resolution modeling as well as data analysis suggest that the MJO may be understood by dry dynamics to a leading-order approximation. Simple, further theoretical considerations presented herein suggest that if it is to be understood by dry dynamics, the MJO is most likely a strongly nonlinear solitary Rossby wave. Under a global quasi--geostrophic equivalent-barotropic formulation, modon theory provides such analytic solutions. Stability and the longevity of the modon solutions are investigated with a global shallow water model. The preferred modon solutions with the greatest longevities compare overall well with the observed MJO in scale and phase velocity within the factors. Host: Leo Donner

August 5, 2019

calendar_today Xin Rong Chua-FPO

person Informal Seminar - Xin Rong Chua-FPO

access_time 10:00 am - 12:00 pm

place Location: Smagorinsky Seminar Room

Xin Rong Chua-FPO

August 9, 2019

calendar_today Justin Ng's FPO

person Informal Seminar - Justin Ng's FPO

access_time 10:00 am - 12:00 pm

place Location: Smagorinsky Seminar Room

Justin Ng's FPO POC: Anna Valerio

August 12, 2019

calendar_today Spencer Clark - FPO

person Informal Seminar - Spencer Clark - FPO

access_time 10:00 am - 12:00 pm

place Location: Smagorinsky Seminar Room

Spencer Clark - FPO

August 15, 2019

calendar_today Jenny Chang FPO

person Meeting - Jenny Chang FPO

access_time 10:00 am - 12:00 pm

place Location: Smagorinsky Seminar Room

Jenny Chang FPO POC: Anna Valerio (AOS)

December 5, 2019

calendar_today Eddy Saturation

person Informal Seminar - Navid Navid Constantinou (Australian National University)

access_time 10:30 am - 11:30 am

place Location: 317 Seminar Room

Eddy Saturation