AOES Seminars AY 2017 – 2018
Climate Dynamics Summer 2018
12 Jul, Dissertation Defense: Zaiyu Wang
Understanding the Role of Coupling in Climate Simulations
Thu, 10:30am, Research Hall 121 (Climate Lab)
Advisor: Dr. Edwin K. Schneider
A simple ocean model (slab ocean model) is coupled to a full atmosphere model to study the role of air-sea coupling. The slab ocean model (SOM) is a 0-dimension model that predicts local temperature of ocean mixed layer solely based on heat flux budget between ocean and the atmosphere. The SOM assumes no interaction between adjacent ocean locations except through heat transport by the atmosphere.
The role of oceanic heat transport is represented by a prescribed heat flux correction called the Q-flux. A method is developed to calculate the Q-flux, so that the SOM sea surface temperature (SST) climatology is as close as possible to a target observed SST climate. The Q-flux is then used to determine remote SST bias effect, where the SST bias is induced by modifying the Q-flux in the tropical eastern Pacific or Atlantic. Strong remote impacts are found in SST and precipitation climatology for the tropical eastern Pacific SST bias.
The role of ocean mixed layer depth (MLD) is investigated by carrying out a globally shallower MLD experiment, using the SOM with a constant Q-flux. Theoretically, the SOM predicts no connection between the MLD and SST climate. However, model results with shallower MLD show strong cooling in the tropics and warming in the mid-high latitudes. Further analysis shows that it is the atmospheric non-linear response to SST annual cycle, caused by MLD changes, that leads to mean SST changes.
The study estimates remote impacts of tropical SST bias in the current coupled models. MLD sensitivity experiment results also suggest simulated mixed layer depth bias can contribute to SST climatology bias in the coupled model.
Tues 26 Jun: Special Seminar
Ajit Seth (Former Cabinet Secretary of India)
The Challenge of Climate Change – and India’s response
10:30 (tea: 10:00) Research Hall 163
[NOTE PREVIOUSLY TIME WAS INCORRECT]
Climate Change is reshaping the way we think about our planet and our future. Scientists, policy makers and industrialists are exploring innovative ways to combat the adverse effects of climate change, in an attempt to minimize global temperature increases resulting from the unabated exploitation of fossil fuels and the emission of green house gases.
The lecture will briefly review how climate change is adversely affecting our atmosphere and ocean, leading to increased frequency of extreme weather events, as well as deleterious impact on human, animal and plant life of the Earth. The lecture will present an overview of global negotiations on efforts to combat climate change, and how the challenges posed by climate change unite as well as divide us.
The lecture will describe India’s concerns and developmental prerogatives, the action that India is taking to adapt to climate change as well as to mitigate the country’s carbon footprint, and to the implementation challenges which India and other developing countries are facing.
Climate Dynamics Spring 2018
All seminars at 1:30pm on Wednesday unless otherwise noted.
Check back for updates – titles and more speakers to be posted.
18 Jan: Stefano Materia (CMCC)
The CMCC Seasonal Prediction System: general evaluation and possible contribution of land surface perturbation
Exploratory Hall 3301 11am-noon
CMCC-SPSv3, the seasonal prediction system developed at Centro Euro-Mediterraneo sui Cambiamenti Climatici (CMCC), will be part of the Copernicus Climate Change Service (C3S) multi-system, which will provide operational forecasts starting in April 2018. CMCC-SPSv3 is based on the general circulation model CMCC-CM, and has changed completely from the older version in terms of dynamical core and initialization data and strategy. The model consists of several independent components that simulate the Earth’s atmosphere (CAM5), ocean (NEMO3.4), land (CLM4.5/RTM) and sea-ice (CICE), together with a central coupler/driver component controlling data synchronization and exchange. This work aims at presenting a first evaluation of the CMCC-SPSv3. Results show valuable quality of seasonal forecasts in terms of skill, accuracy and discrimination.
24 Jan: Current Climate Conversation
Research Hall 121
31 Jan: Adam Sobel (Columbia University)
Understanding deep convection by parameterizing large-scale dynamics
Research Hall 163
This is partly a review of old work on the weak temperature gradient method (which we’ve used to address a variety of problems in tropical dynamics), but also much newer work on coupling the quasi-geostrophic omega equation to a cloud-resolving model (CRM) to parse how deep convection and synoptic-scale dynamics interact in precipitation extremes.
8 Feb: Double Seminar (two speakers in one hour)
Thu, 11-12, Exploratory Hall 3301
Mengmeng Lu (Sun Yat-sen University)
Possible Effect of the Tibetan Plateau on the “upstream” climate over West Asia, North Africa, South Europe and the North Atlantic
Through a set of sensitivity experiments using the CESM1.2.2, this study investigates the role of diabatic heating over the Tibetan Plateau (TP) in the variations of the global climate. It is found that the change in the surface thermal condition of the TP significantly influences the patterns of the atmospheric circulation in its “upstream” regions over central-western Asia, Africa, southern Europe, and the North Atlantic. The atmospheric response to the TP heating is characterized by a vertical circulation, with a strong rising branch over the TP and broad subsidence further to the west. This analysis indicates a climate link between Asia and Africa and the important role played by the TP in this link. The relative contribution of the TP to the heat sources over the entire Asian Continent in influencing the African-European-Atlantic climate is also discussed.
Hanjie Fan (Sun Yat-sen University)
The episode of 2014 Pacific SST warming: the unpredicted easterly anomalies during summer.
At the beginning of 2014, many climate models predicted a major El Nino later that year. The sea surface temperature anomalies (SSTAs) in the central and eastern Pacific were expected to exceed 2 Degrees Celsius in the coming winter. However, the development of the warm SSTAs was stalled in the summer by unpredicted easterly wind anomalies (EWAs) in the equatorial central and eastern Pacific. Observationally, the EWAs prevented the eastward advection of warm water immediately. Meanwhile, they triggered cold Kelvin wave fronts, which propagated to the eastern Pacific to suppress the warm SSTA. In light of the observational evidence, we have conducted a series of sensitivity experiments using the fully coupled CESM with prescribed EWAs to provide model proof of the EWA impact in hindering potential warm events.
14 Feb: Current Climate Conversation
Research Hall 121 [note corrected date]
20 Feb: Xiuhua Zhu (University of Hamburg)
Exploring GCM climate: Internal climate variability (ICV) and its implication
Tuesday, 1:30, Exploratory Hall 3301
Climate change is assessed against a reference climate – 30-year Climate Normals. In practice, this reference climate is updated every 10 years, implying that internal climate variability (ICV) is active on a much longer time scale. Statistic moments of GCM surface temperature show: i) Statistic moments display linear correlation in an unforced control climate; ii) Analyses of CMIP5 simulations suggest that whether or not and how this linear correlation is captured is subject to model resolution, forcing, and the choice of GCM. The results above cast a shadow over statistics derived usually on a window of 10-30 years, which is shorter than GCM-revealed ICV time scale; the possible impact on statistics of climate extremes is discussed. Interesting results from two tentative attempts are presented: i) The relation between statistic moments in the Lorenz Model; ii) An alternative approach to better describe the ICV domain, which provides a new perspective on detection of climate change.
28 Feb: Eric Maloney (CSU)
Modulation of Northern Hemisphere weather by the Madden-Julian oscillation
Exploratory Hall 3301
The Madden-Julian oscillation (MJO) significantly modulates northern Hemisphere midlatitude geopotential height anomalies, blocking, and atmospheric rivers (ARs). However, these connections are only robust during certain MJO phases, and it not clear whether such teleconnections will remain robust in a future warmer climate. First, reanalysis fields and a linear baroclinic model will be used to determine why teleconnections to higher latitudes are more robust during certain MJO phases. The implications of this robustness for numerical weather prediction will also be explored using a leading numerical weather prediction model. Next, the general issue of why these teleconnections are poorly simulated in many weather and climate models will be addressed by linking poor teleconnection performance to biases in the spatial extent of the North Pacific jet that affect the pathway of Rossby wave propagation into high latitudes. How the state of the quasi-biennial oscillation (QBO) affects the MJO teleconnections discussed above and associated prediction skill will then be addressed using numerical and statistical models. Finally, recent modeling results will be presented suggesting that the MJO teleconnection to higher latitudes may weaken in a warmer climate, which may make it more difficult to predict high latitude extreme events such as ARs.
7 Mar: Martha Buckley (GMU)
Can variations in mixed layer depth explain variations in SST predictability timescales in the North Atlantic?
Exploratory Hall 3301
The North Atlantic is a region of enhanced predictability of sea surface temperatures and upper ocean heat content (UOHC). I will estimate predictability timescales for SST and UOHC in the North Atlantic based solely on gridded observational products, using two novel diagnostics: wintertime SST and heat content based on mixed layer. In regions with very deep mixed layers, such as the Labrador Sea, predictability is much larger for UOHC than for SST. Between sixty and eighty percent of the regional variance of predictability timescales for UOHC in the North Atlantic can be explained simply by variations in wintertime mixed layer depths. These results suggest that predictability timescales are primarily determined by the thermal memory of the ocean. Finally, I will compare predictability in CMIP5 to observations.
19 Mar: Current Climate Conversation
Monday, 12:30, Research Hall 121 [note new time]
28 Mar: Liang Chen (GMU)
Simulated and observed impacts of land use and land management on temperature extremes
Exploratory Hall 3301
We compare land-use forcing with other forcing agents in explaining the simulated historical temperature extreme changes in the CESM-Last Millennium Ensemble (LME) project. The spatial pattern of changes in hot extremes in CESM-LME can be largely explained by the land-use forcing, which partially agree with the CMIP5 experiments. However, CESM-LME may fail to represent the observed warming effect of deforestation on hot extremes. Compared with measurements from paired (open versus forest) flux tower sites, we found that land surface models fail to capture the land-use induced changes in energy partitioning between latent and sensible heat flux. Furthermore, we investigated the impacts of land management (irrigation) on surface temperature using both CESM and satellite observations. Strong evaporative cooling of irrigation on daytime surface temperature is found over arid and semi-arid regions. Our results underline the overall importance of land use and land management in temperature extreme changes, implying land use forcing should be highlighted in future climate projections.
2 Apr: H. Annamalai (U Hawaii)
Grand Challenges in Monsoon Modeling: Representation of Processes and Source of Model Errors
Mon, 11am, Exploratory Hall 3301
Sustained research has shown how monsoons arise due to complex interactions among ocean, atmosphere, and land components. At the same time, however, simulating the monsoon precipitation climatology remains a grand challenge. For example, models produce positive rainfall errors (~34 mm/day) over a large area of the western tropical Indian Ocean (TIO) and a dry bias elsewhere. Error sources include fast atmospheric processes (particularly convection), orography interactions and coupled near-equatorial processes. Over the climatologically dry region of the western TIO, why do the models, irrespective of resolutions and varied physical parameterizations, simulate a wet bias? Our working hypothesis is that persistent errors arise due to multiple processes. We will review the recent literature on this topic, and discuss results from process-based sensitivity experiments that identify the importance of realistic boundary layer static stability in reducing the wet bias over the western TIO.
4 Apr: Nadya Vinogradova (NASA)
Ocean Water Cycle: Recent Amplification Observed by NASA
Exploratory Hall 3301
Predicting the future of the Earth’s hydrological cycle requires understanding of the changes in its largest component — the flux of freshwater one the oceans. Evidence from NASA data and models suggest that in response to the warming climate, surface freshwater fluxes over the oceans have developed a distinctive pattern of change, where dry areas are becoming drier and wet areas becoming wetter. This intensification of the hydrological cycle is often linked to corresponding changes in surface salinity, which acts as an ocean indicator of climate change. In this talk, I discuss recent changes in the ocean water cycle that were happening during the last two decades, as well the ocean’s response to such changes using NASA’s self-consistent observing and modeling capabilities.
5 Apr: Warwick Norton (Cumulus hedge fund)
How weather is used by an energy trading company in decision making
Thu, 11am, Exploratory Hall 3301
The talk will give a brief background to energy trading and give some recent examples to show the diversity of decisions made on the outcome of the weather. The importance of basic scientific understand and research to our company will be emphasised. Results from a research project will be presented which demonstrates the importance of the tropics for subseasonal range predictions. There are large interannual variations in forecast skill at this range and winters including 2016/17 can be very challenging to forecast even with the ECMWF model.
9 Apr: Gina Henderson (U.S. Naval Academy)
Contributions of tropical intraseasonal variability to high latitude climate.
Mon 11am Hub 3 & 4 (NOTE NEW DATE, due to weather)
Intraseasonal tropical climate variability has important implications on mid- and highlatitude climate, and in recent studies has been shown to modulate a number of weather processes in the Northern Hemisphere. In such studies, the leading mode of tropical intraseasonal variability, the Madden-Julian Oscillation (MJO), has tended to lag tropical convection by approximately 7 days. However, no such consensus exists when considering the relationship and lag between the MJO and the Antarctic atmosphere. This talk will give an overview of recent tropical-to-high latitude connection work undertaken by our research group in the Oceanography Department at the U.S. Naval Academy. The discussion will include statistical analysis of the MJO’s role in modulating Arctic sea ice and snow cover, in addition to recently published examples of the time-lagged response of Southern Hemisphere tropospheric circulation to tropical MJO forcing.
10 Apr: Dissertation Defense: Priyanka Yadav (GMU Climate Dynamics PhD)
The character of mid-latitude response to the cycles of the Madden-Julian Oscillation heating.
Tue, 11am, Research Hall 162
11 Apr: Thomas Haine (JHU)
Status, Mechanisms, and Impacts of Arctic Freshwater Export
Exploratory Hall 3301 1:30-2:30 PM
Large freshwater anomalies clearly exist in the Arctic Ocean. The sources of freshwater to the Arctic from precipitation and runoff have increased in the last few decades while the freshwater fluxes draining the Arctic are unchanged. Thus, the balance of sources and sinks of freshwater to the Arctic shifted to freshening during the 2000s. The observed accumulation of freshwater is consistent with this increased supply and the loss of freshwater from sea ice. Discharge of this freshwater may impact the Atlantic Meridional Overturning Circulation, and hence Atlantic sector climate.
13 Apr: Dissertation Defense: Sara Amini (GMU Climate Dynamics PhD)
The impact of large-scale circulation regimes on extreme weather over Pacific and North America
Fri, 10am, Exploratory Hall 3301
Dissertation Director: David Straus
18 Apr: Erdal Yigit (GMU)
Whole Atmosphere General Circulation Modeling of Wave-Induced Atmospheric Vertical Coupling
Exploratory Hall 3301 1:30-2:30 PM
Earth’s lower atmosphere is a source of waves that can transport energy and momentum upward and produce substantial dynamical and thermal effects in the middle and upper atmosphere. Observations often provide only limited vertical coverage, but atmospheric general circulation models (GCMs) can capture propagation all the way to the thermosphere in a self-consistent manner. Here, I apply GCMs to atmospheric vertical coupling induced by small-scale gravity waves (GWs). GWs from the lower atmosphere produce marked heating/cooling and dynamical effects in the thermosphere. This is a spectacular manifestation of previously-ignored weather impacts on the geospace environment. I will discuss transient events, such as stratospheric sudden warnings, and the applicability of the general circulation modeling framework to other planets, such as Venus and Mars.
23 Apr: Current Climate Conversation
Mon, Research Hall 121
24 Apr: Dissertation Defense: Guangyang Fang (GMU Climate Dynamics PhD)
Seasonal Predictability of Tropical Atlantic Variability
Tue, 10:30, Exploratory Hall 3301
25 Apr: Teresa Cicerone (GMU)
The link between the Seychelles-Chagos Thermocline Ridge (SCTR) and the Madden-Julian Oscillation
Exploratory Hall 3301
The initiation of the Madden-Julian Oscillation (MJO) remains one of the least understood phenomena. One proposed explanation involves the Seychelles-Chagos Thermocline Ridge (SCTR), a thermocline dome in the southern Indian Ocean associated with wind-driven upwelling. Usually, upwelling regions have cold sea surface temperature (SST), but the SCTR has warm SSTs, because the upwelling does not reach the surface. With a warm surface, a shallow thermocline, and a shallow mixed layer, the SCTR is a hot spot for air-sea interactions on MJO time scales. An analysis of the Community Earth System Model (CESM) reveals that the model mixed layer over the SCTR is cooler and deeper than observed. Small changes in these oceanic components can lead to large changes in convection, and therefore the MJO. These results pave the way for a future sensitivity experiment regarding the MJO response to a shoaled MLD within CESM.
15 May: John Marshall (MIT) POSTPONED
[Dr. Marshall will not be able to make it this week but hopes to reschedule for Fall 2018]
Damping of ITCZ shifts and Monsoons through Coupling of Trade Winds with Ocean Circulation
Tue, 11am, Research Hall 163
Coupling of the trade winds with the ocean’s subtropical cells result in strong damping of ITCZ migrations. We discuss the underlying reasons for this equatorial ‘stickiness’ of the ITCZ and argue that it is a robust feature of the coupled climate. We go on to explore how this coupling manifests itself in the Indian Ocean and likely damps the amplitude of the Monsoon. The ideas are illustrated with reference to the observed modern climate, highlighting regional atmosphere and ocean circulations. We discuss the implications for paleo reconstructions of the ITCZ in past (and future) climates.
2 May: Kristi Arsenault (SAIC/NASA)
Seasonal scale drought forecasting for Africa
Exploratory Hall 3301
Drought and water scarcity are among the most important issues facing Africa and the Middle East. To help address these issues, a seasonal scale drought forecasting system is being developed with the use of sophisticated land model system software tools, satellite-based observations, and dynamical seasonal climate forecasts. In this presentation, an overview of seasonal scale drought forecasting for these regions will be provided along with some validation and skill assessment of the drought and water balance forecasts.
Wed 23 May: Special Off-Campus Seminar
India’s Transition to a Low-Carbon Economy
10am-11am, at the World Resources Institute
James A. Harmon Conference Center, 10 G St NE # 800, Washington DC
Thu 24 May: Special Seminar
Isher Judge Ahluwalia (Indian Council for Res. on Internat’l Economic Relations [ICRIER])
Dimensions of Urban Sustainability: Examples from Indian Cities
11:00 (tea: 10:30) Research Hall 163
India’s rapid economic growth over the past decade and a half has been associated with haphazard urbanisation, leading to deterioration in public service delivery and adverse impact on the environment. This lecture will focus on two key dimensions of urban sustainability, i.e., water and waste management. It will present the state of over-exploitation of ground water as well as pollution of surface water, on the one hand, and poor management of the distribution network which makes it financially unsustainable. It will also discuss the state of solid waste management, the lack of segregation of wet (biodegradable) waste from dry waste and limited processing for resource recovery with its implications for environmental degradation.
Spring 2018 Geology Seminar Series
Seminars 4:30-5:30 pm, Exploratory Hall 1309; refreshments at 4:15.
Feb. 1 – Tolulope M. Olugboji, University of Maryland (seismology lithos-asthenos boundary)
Feb. 8 – Paul Nadeau, University of Stavanger, Norway (US shale gas revolution)
Feb. 15 – Pillar de Oliveira Carvalho Rodrigues, National Observatory (Banded iron formations)
Mar 1 – Helen Janiszewski, Carnegie (Seismology of subduction zones)
Mar 22 – Navit Sagoo, Yale University (Pliocene climate change)
Apr 5 –Wei Liu, China University of Geosciences (Songliao Basin paleoclimate)
Apr 19 – Maya Gomes, Johns Hopkins University (geobiology and sulfur isotopes)
May 3 – TBA (reserved for students and visitors)
Climate Dynamics Fall 2017
All seminars at 1:30pm on Wednesday unless otherwise noted.
11 Sep: Current Climate Conversation
Mon, 1:30pm, Research Hall 121
13 Sep: Jagadish Shukla (George Mason University)
Dynamical Seasonal Prediction: The Tale of Two ENSO-Monsoons and rainfall over India
Research Hall 163
After 50 years of climate modeling, and nearly 30 years after it was suggested that there is a scientific basis for dynamical seasonal prediction, the fidelity of climate models improved so that the models could produce a skillful prediction of Indian summer monsoon rainfall. The first part of this seminar will give a historical overview of monsoon forecasting, and a personal retrospective of the evolution of the science of dynamical seasonal prediction. The second part of the seminar will present the results of reforecasting summer monsoon rainfall in the past 57 years (1958-2014) using the NCEP Climate Forecast Systems. It will be shown that if the modern day coupled climate models were available during the 1970’s, even with the limited ocean observations at that time, it should have been possible to predict the 1972-73 ENSO event and the associated severe monsoon drought. This seminar will also present a comparison of the two strongest events – 1972-73 and 1997-98, for both of which ENSO was predicted quite accurately but the prediction of monsoon rainfall over India for 1997-98 was quite inaccurate.
20 Sep: Vikram Mehta (Center for Research on the Changing Earth System;CRCES)
Societal Impacts of Natural Decadal Climate Variability – Pacemakers of Civilizations
Exploratory Hall 3301
A substantial body of research has focused on understanding causes, mechanisms, and impacts of natural decadal climate variability (DCV) such as Pacific Decadal Oscillation (PDO), tropical Atlantic sea-surface temperature gradient variability (TAG), and decadal variability of El Niño-La Niña events. Tree-ring data going back more than 700 years show decadal hydrologic cycles (DHCs) associated with the rise and fall of civilizations, large-scale famines, and socio-political revolutions. Instrument-measured data confirm presence of DHCs. This talk, drawn from my recently-published book (Mehta, V.M., 2017: Natural Decadal Climate Variability: Societal Impacts), will give an overview of worldwide impacts of DCV phenomena, with specific examples of socio-economic-political impacts. The talk will end with an outline of actions needed to adapt to these impacts.
27 Sep: Kingtse Mo (Climate Prediction Center NOAA)
Drought Variability over the United States
Exploratory Hall 3301
We examined historic drought variability over the conterminous U.S. (CONUS) using observed precipitation (P) and reconstructed total moisture percentiles (TMP) and runoff from four land surface models over the period 1916-2013. We identified 16 drought events that covered more than 50% of the CONUS, most located at least partially over the Central U.S., which plays a critical role in U.S. (and global) food production. Most of these large droughts occurred when sea surface temperatures were cold in the tropical Pacific and warm in the North Atlantic. Droughts occurred less often and events were less severe as time progressed. In addition to long term trends, we found strong decadal variations in drought occurrence. Our analysis shows that U.S. droughts have preferred times of year for onset and demise. They are most likely to start in autumn (at the end of the rainy season) and end at the beginning of the spring rainy season.
4 Oct: Suki Manabe (Princeton U)
Interhemispheric Asymmetry in Global Warming
Research Hall 163
As the concentration of greenhouse gas increase 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.
11 Oct: Current Climate Conversation
Research Hall 121
25 Oct: Bohar Singh (George Mason University)
Seasonality of the Tropical Intraseasonal Oscillations: Sensitivity to Mean Background State
Thesis Defense
10am, Research Hall 163
Tropical intraseasonal oscillations (TISO) are identified with anomalies of atmospheric convection with 20-100 day periods and large spatial scale. We find that TISO events propagate eastward from November to April and northward from May to October. A composite analysis of the mean background reveals that the co-occurrence of warm climatological SST and mean westerly wind plays an important role in setting the location and propagation direction of TISO. Sensitivity experiments indicate that the regionality and seasonality of TISO are closely coupled to the SST and the low-level circulation. The SST in the tropics must reach a required threshold for convection to occur, while the low-level circulation controls the direction of propagation by controlling the location of moisture convergence.
25 Oct: Paul Dirmeyer (George Mason University)
Land-Atmosphere Interactions in Nature and Models
Exploratory Hall 3301
Feedbacks in the water and energy cycles from the land surface to the atmosphere can provide a means to improve the prediction of weather and climate, as persistent anomalies in land surface states such as soil moisture can provide memory and signal beyond what the atmosphere alone can maintain. In this talk, I will present a brief history of notions of land-atmosphere feedbacks, culminating with the “breakthrough” finding of regional hot-spots (analogous to El Niño) of land-atmosphere interactions around the world. A description will be given of the evolution of the theory of land-atmosphere coupling, and how we are applying that theory along with newly-available observational data sets to validate our weather and climate models in new ways. I will conclude by showing evidence of predictability and enhanced prediction skill attributable to knowledge of land surface states.
18 Oct: Charles Ichoku (NASA Goddard Space Flight Center)
Understanding the Drivers of Water-Cycle Dynamics in Tropical sub-Saharan Africa
Exploratory Hall 3301
Parts of tropical sub-Saharan Africa north of the Equator have experienced multiple episodes of devastating droughts, but occasionally also intense flooding. Some of the phenomena to which this situation has been attributed include: large-scale natural variability such as the El-Nino southern oscillation (ENSO), remote industrial sulfur emissions, and regional grazing and biomass-burning activities. In this talk, we will examine how large scale natural phenomena such as ENSO and the Atlantic Multidecadal Oscillation (AMO) may have contributed to severe droughts during the 1970s and 1980s, as symbolized by the dramatic drying of Lake Chad. Secondly, we will examine changes in regional hydrological indicators, which are associated with satellite-observed land-use activities which utilize wildland fires and other types of biomass burning. Thirdly, we will examine the intrinsic precipitation patterns observed from satellite and ground-based measurements. Finally, we will provide some perspectives on future research that can help unravel some of the ambiguities related to the highly variable water-cycle dynamics in tropical sub-Saharan Africa.
1 Nov: John Cook (George Mason University)
Responding to alternative facts in a post-truth world
Research Hall 163
In recent times, we have seen an increased prevalence of fake news with the public seeming to rely less on scientific evidence. How should scientists respond to these concerning trends? Several decades of research into climate science denial offers insights into the post-truth phenomenon – which displays the same kind of motivated reasoning as those who reject the scientific consensus on climate change. This talk will examine the psychological research into science denial – why and how do some people reject science and how might we respond?
8 Nov: Current Climate Conversation
Research Hall 121 (returned to original date after recent change)
13 Nov: Elizabeth Barnes (Colorado State University)
Causal Links Between the Arctic and the Midlatitude Jet-streams
Mon, 1:30pm, Research Hall 163
The Arctic has been warming rapidly over the past few decades, raising the question of how polar warming may impact the weather in lower latitudes. Here, we apply causal discovery techniques (e.g. Granger causality) to quantify the sensitivity of the jet-streams to variations in Arctic temperatures on subseasonal timescales using 4800 years of CMIP5 model simulations. These causal discovery techniques allow us to quantify the jet-stream sensitivity in the presence of feedbacks, as well as assess seasonal and regional sensitivities. A further benefit of this approach is that we can make direct comparisons of the sensitivities between observations and models, as well as across many models, and here we demonstrate that model differences in the mean-state circulation can lead to differences in the jet-stream response to Arctic temperature variability. While this talk is focused on the causal links between Arctic warming and the midlatitude atmospheric circulation, we hope it also highlights the relevance and utility of causal discovery techniques for atmospheric dynamics research.
15 Nov: Joe Fiore (NWS)
NWS GOES-16 Operational Test and Evaluation (OT&E) Process & Overview
Wed, 11:00-12:00, Exploratory Hall 3301 [note corrected date]
An introduction to where our branch fits in the NWS, what our general OT&E (and life cycle model testing) process involves, then specifics about the GOES-16 OT&E .
15 Nov: Dwi Susanto (U Maryland College Park)
Overview of Indonesian Throughflow and its Role on Global Ocean Circulation and Climate
Exploratory Hall 3301
Indonesian Throughflow (ITF) is the leakage of western tropical Pacific water into the southeastern Indian Ocean through the narrow passages of Indonesian Seas. ITF is an important pathway for the transfer of climate signals around the world’s oceans. An overview of the ITF in the Makassar Strait will be presented with results and detailed transport estimates. The ITF branch through the South China Sea-Karimata Strait has received little observational attention until the SITE (South China Sea-Indonesian Transport/Exchange) field measurement program. Preliminary results from SITE will be described. The current logistical and financial challenges facing current field measurements are not sustainable in the long run and therefore other approaches such as numerical model, remotely sensed and paleoclimate data will be discussed.
27 Nov: Laure Zanna (Oxford)
Ocean Heat Uptake and Dynamical Sea Level Rise: Past and Future Uncertainty
Monday 2:15-3:15 (note new date & time) Research Hall 163
The ocean absorbs a large portion of the anthropogenic heat released in the climate system, leading to an increase in global mean sea level rise. The magnitude, pattern and rate of ocean heat uptake are governed by several processes such as deep water formation, Southern Ocean Ekman pumping, and air-sea interaction. The spatial patterns of heat uptake and storage are further impacted by heat redistribution via changes in the ocean circulation, induced by natural variability and anthropogenic forcing.
We use observations, theory and a hierarchy of models to estimate the heat storage and thermosteric sea level rise in the Atlantic due to changes in circulation during the observational period and in future projections. We will show that about 2/3 of the thermosteric sea level rise at the latitude of NYC in the past 50 years is attributed to ocean circulation changes and traced back to surface forcing. We will further explore the link between air-sea forcing, ocean circulation and heat and carbon uptake in future projections. Our findings highlight high-latitude forcing as the cause for the large uncertainty in regional sea level projections, and provide a way forward to constrain regional projections of ocean heat uptake and sea level rise, including the use of anthropogenic carbon to infer circulation changes.
29 Nov: Brian Gross (NOAA-EMC)
Research Hall 163
6 Dec: George Philander (Princeton U.)
Research Hall 163
The Hedgehog and The Fox1
A Nelson Mandela Perspective on Global Warming
Global warming, a Tragedy of the Commons2 that requires “a fundamental extension in morality,” is polarizing because it poses both scientific and ethical challenges. How do we find a balance between our responsibilities to those living in abject poverty today, and our obligations to future generations? Science has no answer. To paraphrase Galileo: “science tells us how the heavens go, but not how to go to heaven”. The challenge is to bridge the cold, calculating, uncompromising world of science, and the profoundly different world of human affairs where compromise is a requisite, compassion a virtue. For guidance on how to proceed we can turn to Nelson Mandela, an authority on coping with polarized situations. The Clint Eastwood movie INVICTUS (about a rugby tournament in Johannesburg in 1995) provides part of his answer. The Kenny Rogers song “The Gambler” provides another. The solution is to know when to be a fox, when to be a hedgehog1. The seasonal cycle, the huge, annual global climate change that everyone experiences, is an excellent vehicle for exploring solutions to this dilemma.
1. Archilochus (7th-century b.c.e.): The fox knows many things, but the hedgehog knows one big thing.
2. Hardin G. Tragedy of the Commons Science vol 162, pp 1243-1248, 1968.
18 Dec: Current Climate Conversation
Mon 2:00 Research Hall 121 (note new date and time)
Fall 2017 Geology Seminar Series
Thursdays, 4:00-5:30, Exploratory Hall 1309
Sep 7 – Ron Martin, University of Delaware (history of biodiversity)
Sep 21 – Jesse Reimink, Carnegie Institution (earliest Earth terranes)
Special Public Lecture
Oct 5 – Howard Spero (U California – Davis)
Geosciences Frontier – Pursuing Novel Questions with 21st Century Tools
9:00-10:00am, Exploratory Hall 3301
About the Speaker: Prof. Spero is an AGU Emiliani Lecturer, and is a Fellow of AGU, AAAS, the Geological Society of America, and the California Academy of Sciences. His research focuses on the biological and environmental parameters that affect the stable isotope and trace metal geochemistry of the shells of recent and fossil organisms; paleoclimatology, marine micropaleontology, and paleoceanography.
Oct 5 – Daniel Viete, Johns Hopkins University (metamorphic petrology)
Oct 12 – Alan Pitts, University of Camerino (GMU’s new field camp)
Oct 19 – Ross Mitchell, Curtin University (supercontinent cycles)
Nov 2 – Marco Franceschi, Fulbright, Padua (ancient marine margin carbon sequestration)
Nov 16 – Rocio Caballero-Gill, USGS (Pliocene oceanography)
Nov 30 Note: seminar cancelled.
[Damien Pas, AOES-GMU (Devonian paleoclimates)]
7 Dec: ESS Master’s and AOES Scholars presentations
