GFDL - Geophysical Fluid Dynamics Laboratory

GFDL Events & Seminars

Upcoming GFDL events & seminars

Events and seminars

  • October 16, 2017: Interhemispheric Asymmetry in Global Warming
    Suki Manabe (AOS Program at Princeton University)
    As the concentration of greenhouse gas increases in the atmosphere, temperature increases at the earth surface. In the Northern Hemisphere, the magnitude of the warming increases with increasing latitude and is at a maximum over the Arctic Ocean and its immediate vicinity. In the Southern Hemisphere, on the other hand, the polar amplification of the global warming is absent in the Antarctic Ocean. This is what happened in the numerical experiment conducted at GFDL almost 30 years ago. The geographical pattern of global warming described above appears to be broadly consistent with the pattern of surface temperature change that have been observed during the last several decades, when the rate of increase of greenhouse gas is pronounced. In this talk, I would like to discuss the role of ocean in delaying global warming particularly in the circumpolar ocean of the Southern Hemisphere.
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • October 17, 2017: Indian Monsoon Depressions: New insights from GFDL's AGCM and Linear Theory
    Angel Adames (GFDL)
    The mechanisms that lead to the propagation of moisture and moist static energy in monsoon low and high-pressure systems collectively referred to as synoptic-scale monsoonal disturbances (SMDs), are investigated using daily output fields from GFDL's Atmospheric Model 4 (AM4). Propagation of the moisture anomalies is dominated by vertical moisture advection while the MSE anomalies propagate due to horizontal advection of low-frequency dry static energy by the SMD winds. By combining the budgets, we interpret the propagation of the precipitation anomalies in terms of lifting that is forced by horizontal dry static energy advection. This process moistens the lower free troposphere, producing an environment that is conducive for deep convection. The precipitation anomalies are, in turn, largely maintained by longwave radiative heating. Based on these results, we propose a linear framework where the evolution of moisture plays a central role in SMDs. In this framework, warm air advection by the anomalous northerly winds induces vertical moisture advection, which moistens and destabilizes the column. The moistened lowered troposphere enhances convection which, in turn, causes the low pressure system to intensify through vortex stretching. This instability only occurs if the vorticity tendency from dry processes (such as horizontal vorticity advection) and moist processes (vortex stretching from convection) are of the same polarity.
    Time: 10:30 am - 11:30 am
    Location: Smagorinsky Seminar Room
  • October 18, 2017: The impact of nitrogen chemistry in snow on atmospheric oxidising capacity in the polar boundary layer
    Veronica Chan (British Antarctic Survey)
    Snow surfaces do not only influence the albedo feedback on Earth but also have a significant impact on the chemistry of the overlying air. Light-induced chemical reactions take place in the snow leading to emissions of reactive chemical species such as nitrogen oxides, an ozone precursor, which can alter ozone concentration in the lower atmosphere. Tropospheric ozone is a pollutant and a greenhouse gas that can influence the regional energy balance and climate. This project aims at developing a model to quantify the emissions of nitrogen species from snow for the following reasons: 1) In the Arctic, there is strong interest in near-term mitigation of the current warming by controlling tropospheric ozone precursors as the level of nitrogen oxide has doubled since the mid-twentieth century due to fossil fuel burning from the shipping industries. To provide an accurate assessment of how effective the adopted mitigation measures are it is necessary to understand the natural background air chemistry and take into account the chemical snow source. 2) Climate models predict the largest temperature rise in the polar regions which would certainly change the chemical snow source. The consequences of the changing climate on nitrogen emission from snow and the feedback via tropospheric ozone level will be constrained. 3) Ice cores are powerful archives of past climate and environmental conditions, from seasonal to multi-millennial timescales. However, photoreactions and physical processes within the snowpack do influence nitrate concentrations and currently prevent a quantitative interpretation of the polar ice core record of nitrate.
    Time: 12:00 pm - 1:00 pm
    Location: Smagorinsky Seminar Room
  • October 19, 2017: The Role of Aerosol and Greenhouse Gas Forcing in CMIP5 Models: Impacts on Atlantic Hurricane Intensity and Asian Monsoon
    Formal Seminar - Mingfang Ting (Columbia University)
    In this talk, I will discuss our recent work on the regional climate changes in the historical period due to both the aerosol and greenhouse gas forcing, in particular how these anthropogenic forcing may have impacted the Asian monsoon and the Atlantic hurricane intensity. While aerosols and greenhouse gases tend to produce opposite sign changes in terms of surface temperature and precipitation as previously discussed, the mechanisms by which these changes occur are not entirely symmetric between the two forcing cases. For example, aerosols tend to produce largely dynamical responses in Asian monsoon circulation changes, while greenhouse gas forcing tends to be dominated by the thermodynamic impact through changes in atmospheric moisture content. For their impact on the Atlantic hurricane intensity, aerosols are more effective in causing changes in hurricane intensity than greenhouse gases, due to differences in surface energy balances. Future changes in Asian monsoon and hurricane intensity as simulated by the CMIP5 models will also be discussed as a comparison to that during the historical period.
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • October 25, 2017: Understanding How Tropical Cyclone Intensification Rates Could Increase with Climate Change
    Kieran Bhatia (GFDL)
    Recent studies have showed that tropical cyclone (TC) intensification rates control forecast performance, the magnitude of financial losses, as well as the lifetime maximum intensity of a storm. As one of the first global coupled climate models to simulate and predict category 4 and 5 (Saffir–Simpson scale) TCs and their interannual variations, the High-Resolution Forecast-Oriented Low Ocean Resolution (HiFLOR) model at the Geophysical Fluid Dynamics Laboratory (GFDL) is uniquely able to provide insight on how the entire TC intensification distribution could be transformed due to climate change. In this study, three 70-year HiFLOR experiments are performed to identify the effects of radiative forcing on TC intensity change. For each of the experiments, sea surface temperature (SST) and atmospheric radiative forcing are nudged to different targets, allowing us to explore the sensitivity of TCs to these conditions. First, a control experiment, which uses prescribed ocean and atmospheric forcing observed during the years 1986-2005, is compared to two observational records and evaluated for its ability to capture the mean TC intensity behavior during these years. The simulated intensification distribution as well as the percentage of TCs that become major hurricanes agrees well with observations. The control experiment is then compared to two climate change experiments, which use the same climatological SSTs from the control experiment plus mean SST anomalies and atmospheric radiative forcing from either 2016-2035 or 2081-2100. The frequency, intensity, and intensification distribution of TCs all shift to higher values as the 21st century progresses. Several synoptic variables are investigated as possible pathways for a warming climate to affect TC intensification.
    Time: 12:00 pm - 1:00 pm
    Location: Smagorinsky Seminar Room
  • October 26, 2017: How much has human-caused climate change influenced wildfire extent across western US forests?
    Formal Seminar - John Abatzoglou (University of Idaho)
    Wildfire activity across western US forests has seen substantial variability over the past century with changes in human settlement, fire management policies, and climate variability. Since the mid 1980s, the amount of fire across western US forests has increased 8-fold leading to a cascade of impacts including widespread forest mortality, carbon emissions, periods of degraded air quality, and substantial fire suppression expenditures. Although numerous factors aided the recent rise in fire activity, observed warming and drying have significantly increased fire-season fuel aridity, fostering a more favorable fire environment across forested systems. Human-caused climate change was responsible for half of the documented increases in fuel aridity since the 1970s and contributed to a substantial increase in forest fire extent over the past three decades.
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • October 31, 2017: Wave breaking in ocean-atmosphere interactions
    Luc Deike (Princeton University)
    Breaking waves at the water surface is a striking example of turbulent mixing across a fluid interface. The impact of the jet generates turbulence, entrains air into the water and ejects droplets into the air. A fundamental understanding of the general multi-scale properties of the resulting multiphase turbulent flow is necessary to develop more accurate gas transfer or spray generation parameterizations. In this talk, I will discuss a general framework to account for the effect of breaking waves on ocean-atmosphere interaction, such as dissipation, momentum flux, air entrainment or Lagrangian drift. I will start by a model for air entrainment by breaking waves in the ocean, based on laboratory experiments and direct numerical simulations at the wave and bubble scale. This model is then up-scaled to the ocean using measurements of the wave and wave breaking statistics. This leads to semi-empirical formulas relating wind and wave variable, such as wind speed and significant wave height, to air entrainment by breaking. I will discuss how this approach can be used to compute other key exchanged variables, such as energy dissipation, Lagrangian drift or sea spray. Point of Contact: Dr. Stephen Griffies, 609-452-6672.
    Time: 10:30 am - 11:30 am
    Location: Smagorinsky Seminar Room
  • November 1, 2017: Convection, climate, and their sensitivities in cloud-resolving FV3
    Nadir Jeevanjee (GFDL)
    We present cloud-resolving FV3 simulations and explore their sensitivity to resolution, the hydrostatic approximation, and numerical damping parameters. We find that O(100 m) resolutions are required for convective vertical velocities to converge, and that the hydrostatic solver overestimates these by a factor of 2 - 3 in this regime. We develop analytic theory to explain these results. We also find a striking sensitivity of the mean climate to `divergence damping', a commonly used form of explicit diffusion on the wind fields. This sensitivity appears to be tied to the width of convective updrafts, which increases with increased damping and acts as kind of convective organization, dramatically drying out the troposphere, reducing cloudiness, and increasing the OLR by up to 35 W/m^2.
    Time: 12:00 pm - 1:00 pm
    Location: Smagorinsky Seminar Room
  • November 8, 2017: TBD
    Pu Lin (GFDL)
    TBD
    Time: 12:00 pm - 1:00 pm
    Location: Smagorinsky Seminar Room
  • November 9, 2017: TBD
    Formal Seminar
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • November 15, 2017: TBD
    Laure Zanna (GFDL )
    TBD
    Time: 12:00 pm - 1:00 pm
    Location: Smagorinsky Seminar Room
  • November 16, 2017: TBD
    Formal Seminar
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • November 22, 2017: TBA
    Hailey Shin
    TBD
    Time: 12:00 pm - 1:00 pm
    Location: Smagorinsky Seminar Room
  • November 29, 2017: Chairman of the Board
    David Goodrich (Chesapeake Climate Action Network)
    A Hole in the Wind: A Bicycle Journey Across the US, Looking at Climate” After retiring from NOAA in 2011, the speaker rode 4200 miles from Delaware to Oregon, looking at the effects of climate change up close and talking with people along the way. He came across fragmented barrier islands on the coast, drought and expanding wind farms in Kansas, beetle-killed forest in Colorado and fire in Idaho. Along the way, he encountered a toddler's beauty pageant in Maryland, the landscape of fracking in Pennsylvania, a tornado party in Missouri, and a ghost town in Wyoming. His book, A Hole in the Wind, was released by Pegasus Books this summer.
    Time: 12:00 pm - 1:00 pm
    Location: Smagorinsky Seminar Room
  • November 30, 2017: TBD
    Formal Seminar
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • December 6, 2017: Why has the tropical lower stratosphere stopped cooling for the last 20 years?
    Lorenzo Polvani (Columbia University)
    TBD
    Time: 12:00 pm - 1:00 pm
    Location: Smagorinsky Seminar Room
  • December 7, 2017: TBD
    Formal Seminar
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • December 20, 2017: Diabatic Influence of Recurving Tropical Cyclones on the Midlatitude Atmospheric Circulation
    Heather Archambault (GFDL Associate Director)
    To be provided
    Time: 12:00 pm - 1:00 pm
    Location: Smagorinsky Seminar Room
  • December 21, 2017: TBD
    Formal Seminar
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • December 28, 2017: TBD
    Formal Seminar
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • January 4, 2018: TBD
    Formal Seminar
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • January 11, 2018: TBD
    Formal Seminar
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • January 18, 2018: TBD
    Formal Seminar
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • January 25, 2018: TBD
    Formal Seminar
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • February 1, 2018: TBD
    Formal Seminar - Tapio Schneider (California Technical Institute)
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • February 8, 2018: TBD
    Formal Seminar
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • February 22, 2018: TBD
    Formal Seminar - Lori Bruhwiler (ESRL/GMD)
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • March 1, 2018: TBD
    Formal Seminar
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • March 8, 2018: TBD
    Formal Seminar
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • March 15, 2018: TBD
    Formal Seminar - Cecilia Bitz (University of Washington)
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • March 22, 2018: TBD
    Formal Seminar
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • March 29, 2018: TBD
    Formal Seminar - Norman G. Loeb (NASA)
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • April 5, 2018: TBD
    Formal Seminar - Linus Magnusson (ECMWF)
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room
  • April 12, 2018: TBD
    Formal Seminar
    TBD
    Time: 2:00 pm - 3:00 pm
    Location: Smagorinsky Seminar Room

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