Columbia Water Center Scientists to Present New Findings at the AGU Fall Meeting

by |November 30, 2011

The American Geophysical Union’s fall conference is coming up! The meeting will be held in San Francisco from December 5th to the 9th — as usual, Columbia Water Center scientists and associates will be giving a number of presentations covering a dizzying array of topics.

Presentation themes this year include conflict and peace in trans-boundary river basins; central planning versus public-private partnerships for water resources; streamflow forecasting and reconstruction using tree rings; the climate connection to flooding in Brazil and the Midwestern United States; a new way to understand the timing of cloud cover and convection over land; the crisis of water resources in the developing world; extreme precipitation in Europe over the last century; the historical impact of climate extremes on global agricultural production and trade, and using “Local Lyapunov Exponents” to understand the decadal variability of El Nino.

Following is a list of presentations with abstracts to be presented by Columbia Water Center scientists.

December 5, 2011

Session: H11F. The Evolution of Water Management Paradigms (Posters)

8:00 am to 12:20 pm
Topic: Hydrology (H)
Location: Halls A-C (Moscone South)
Co-Sponsors: Public Affairs (PA) and Societal Impact and Policy Sciences (SI)

“Climatic Change, Conflict and Peace in Transboundary River Basins – A Theoretical Perspective”

Abstract ID: H11F-1111
Presenter: T. U. Siegfried
Authors: T. U. Siegfried; L. Beck; V.’Koubi; T. Bernauer


Recent research shows that one of the most significant risk for societal development pertains to water availability and that the greatest risks for unrest stemming from economic deprivation and the erosion of livelihoods is found in transboundary river basins in poor and politically unstable parts of the world. While until now, historic linkages between water scarcity and conflict were weak at best, there is growing fear that environmental change will increasingly lead to an entanglement of conflict and resources dynamics in the future. Where resources are not jointly managed in a cooperative way and resources sharing mechanisms not legislated by sound international institutions and were significant impacts from environmental change are expected, these developments give rise to concern. To study environmental change and conflict interlinkages, we develop a formal hydro-climatological model for transboundary freshwater resources and investigate theoretically how climate change translates into potential for conflict and peace, contingent on configurations of power between riparians. The model accounts for how upstream countries exercise power by using water whereas downstream countries use power to obtain water. We show that equilibrium water allocation outcomes are biased towards the more powerful riparian, and that absolute upstream or downstream river basin dominance are limiting cases of our general model. Our model suggests that the basin-wide conflict potential is always more sensitive to changes in relative power between riparian states than to impacts from climatic changes.

“What’s the P in PPP?”
Abstract ID: H11F-1114
Presenter: T. Heikkila
Abstract Authors: T. Heikkila; U. Lall


Public, Private, Partnership, Participatory, Polycentric, Poor, Perfect, Purveyor, Planner, Positive, Plural, Practical, Political, Process, Pervasive, Phase, Physical, Passive, Progressive, Paradigm? As the world stands at the crossroads of a water scarcity crisis, many wonder whether the “well developed” central planner paradigm of water resources planning, management, investment and regulation that emerged in the last century has served us well. The negative impacts of centralized projects and their management are routinely decried. Service metrics of publicly managed systems continue to deteriorate as the ability to recover operational and maintenance costs continue to be weak. The political processes that portend to protect the access of the disadvantaged are said to contribute to the poor performance of the systems, especially for the disadvantaged. The institutionalization of “well formed” policies that prove inflexible in an environment where supply, demand and societal goals change calls for adaptive management. Stakeholder driven participatory processes and public private partnerships are touted as potential paradigms for progressive solutions that span the political domain and could help achieve positive water balance recognizing the dimensions of supply and demand at local or regional scales. This talk presents a proposed framework that postulates the prospective roles that different actors could play to provide an effective and practical strategy for securing water resources while promoting active allocation strategies, improving access and reliability while promoting profitability for private operators, including progressive farmers who given their usage patterns can make the most prolific contribution to water security. We label this the many P Paradigm. To develop this framework, we draw initial insights from the literature on participatory and decentralized watershed governance. We then apply findings from field experiments on water management reforms in India and Brazil to extend this literature and demonstrate the benefits of the framework to scholars and practitioners alike.

“Incorporating Seasonal Forecast of Inflow into Existing Water Resource Management at Ubolratana Dam, Thailand”
Abstract ID: H11F-1121
Presenter: V. Chatikavanij
Authors: V. Chatikavanij; P. J. Block; U. Lall


Seasonal forecast of streamflow, coupled with dynamic reservoir operation policy, has been shown to improve water allocation and flood control. By considering current and expected future reservoir level, water managers can make more adaptive and informed judgments about reservoir operation and allocation policy. While seasonal forecast application has shown substantial positive results, its adoption is still lagging due to the difficulties in integrating forecast into the current reservoir management system. This project offers a simple framework for incorporating seasonal streamflow forecasts into existing operation to optimize reservoir management decisions at the Ubolratana Dam in the Northeastern region of Thailand. The framework allows for the retention of existing reservoir policy while altering the application of the upper rule curve based on forecast information. Our objective is to maximize water release for hydropower generation, minimize spill and shortages while meeting demands for irrigation and water quality control during the peak summer monsoon season. Climate variables, including sea-surface temperature and sea-level pressure in March-May, are used to develop streamflow forecast ensembles for September-November. We use a dynamically linked system of forecast and reservoir management models to specify operating rules for end of the month storage levels at the Ubolratana Reservoir. Benefits and reliability based on the forecast ensembles are compared with historical operations and a climatological-based approach. Forecast ensembles are also divided into terciles to evaluate performance during dry and wet years, of particular interest to water managers. Results demonstrate that the dynamic operations contingent on forecasts may increase water releases for hydropower, decrease spill and deficit, and improve reliability compared with the status quo.

Session: GC13A. Climate Change, Food, and Water: III (Posters)
1:40 to 6:00 p.m.
Topic: Global Environmental Change (GC)
Location: Room 3016 (Moscone West)
Co-Sponsor: Hydrology (H)

“Virtual Water Trade: Revisiting the Assessments to Incorporate Regional Water Stress”
Abstract ID: GC13A-0969
Presenter: S. Perveen
Authors: S. Perveen; M. J. Puma; T. J. Troy; M. Browne; M. Ghosh


Virtual water (VW) refers to the volume of freshwater embedded in the production and shipment of a commodity, which can include agricultural or industrial products, and the trade of commodities can then be viewed as the trade of one region’s water resources to another. The premise behind this trade is that countries with a comparative water advantage may choose to export crops, and countries with scarce water resources may focus economic activity on non-water intensive sectors. However, this assumption is not always true given food self-sufficiency policies; water scarce regions often choose to unsustainably mine aquifers for irrigation. Recent studies have shown no correlation between dependency on VW imports and water scarcity for nations, suggesting that politico-economic considerations rather than resource scarcity considerations may dominate the current VW dynamics. Existing VW computations do not take into account water-scarcity value or the full-cost pricing of commodities. This study aims to fill in this gap by focusing on three countries – the United States, India, and Japan – and their production, imports and exports of crop, livestock and industrial commodities. These countries offer three different perspectives on virtual water, with Japan as a net importer of agriculture virtual water and a major industrial nation. The United States, on the other hand, exports significant quantities of grain. India is a developing country with a strong focus on food self-sufficiency. We first quantify the amount of water used in the production of each commodity and then examine the virtual water trade balance for each country, examining the tradeoffs each country has made between agriculture and industrial water use; given that water resources are finite. To examine the interplay between virtual water trade and water scarcity, we focus on two sub-regions, the Ogallala Aquifer in the US and the Punjab region in India, both of which have significant agricultural economies and are knowingly depleting their groundwater resources. We estimate the direct and indirect cost of water in each region and evaluate the economic trade-offs these regions are making.

December 6, 2011

Session: H24C. Hydroclimatic Extremes: Monitoring, Diagnosis, and Prediction III (Oral Presentations)
4:00 pm to 6:00 pm
Topic: Hydrology (H)
Location: Room 3016 (Moscone West)
Co-Sponsor(s): Atmospheric Sciences (A)

“Spatio-Temporal Non-Stationary Flood Frequency Modeling: Seasonal Peak Floods in Southern Brazil Modeled Using Pre- and Concurrent Pacific and Atlantic Ocean Conditions”
Abstract ID: H24C-06
5:25 to 5:40 pm
Presenter: C. H. Lima*
Authors: C. H. Lima; U. Lall


Floods events are the major natural disaster in Brazil with significant resulting damages in the recent years. The understanding of the spatio-temporal patterns and the climate states associated with those events is key for flood risk management. In this work we analyze and model seasonal peak floods from 33 streamflow gauges across the Paraná Basin, which is the second largest basin in Brazil located in the South-Southeast region of the country. Significant monotonic trends are found for the January-April peak flow for some sites located in the southeast part of the Paraná basin. Peak over threshold (POT) data for the January-April season also reveal some monotonic temporal trends in the accumulated volume for some sites, while no significant evidence is found for monotonic trends in the frequency of occurrence of streamflow events above a specified threshold (e.g. 95% percentile). Composite analysis of pre- and concurrent season conditions in the sea surface temperature (SST) of the Tropical Pacific and South Atlantic oceans using NOAA and NCEP/NCAR reanalysis data reveal that warmer ENSO conditions in the previous season tend to be associated with a higher occurrence of extreme floods across the basin. This is also associated with a persistent colder SST in the subtropical Atlantic during the January-March season. A non-homogeneous Poisson-Generalized Pareto (Poisson-GP) distribution using Atlantic and Pacific SST derived climate indexes as covariates is proposed to model the occurrence of a high threshold and the peak flows over this threshold for the sites across the basin. A comparison with stationary, traditional POT models suggest that the proposed non-stationary model is more suitable for the floods conditions observed in the analyzed sites. Spatial patterns arising from the at-site parameter estimates point also to a better strategy of multivariate, non-stationary POT modeling in a Hierarchical Bayesian framework, which considers the spatial dependence across the sites in a less complex manner.

“Delaware River Streamflow Reconstruction using Tree Rings: Exploration of Hierarchical Bayesian Regression”
Abstract ID: H24C-07
5:40 to 5:55 pm
Presenter: N. Devineni*
Authors: N. Devineni; U. Lall; E. Cook; N. Pederson


We present the application of a linear model in a Hierarchical Bayesian Regression (HBR) framework for reconstructing the summer seasonal averaged streamflow at five stations in the Delaware River Basin using eight newly developed regional tree ring chronologies. This technique directly provides estimates of the posterior probability distribution of each reconstructed streamflow value, considering model parameter uncertainty. The methodology also allows us to shrink the model parameters towards a common mean to incorporate the predictive ability of each tree chronology on multiple stations. We present the results from HBR analysis along with the results from traditional Point by Point Regression (PPR) analysis to demonstrate the benefits of developing the reconstructions under a Bayesian modeling framework. Further, we also present the comparative results of the model validation using various performance evaluation metrics such as reduction in error (RE) and coefficient of efficiency (CE). The reconstructed streamflow at various stations can be utilized to examine the frequency and recurrence attributes of extreme droughts in the region and their potential connections to known low frequency climate modes.

December 7, 2011

Session: A31D. Atmospheric Feedbacks and Climate: Observations, Theory, and Modeling I (Posters)
8:00 pm to 12:20 pm
Topic: Atmospheric Sciences (A)
Location: Halls A-C (Moscone South)
Co-Sponsor(s): Global Environmental Change (GC)

“A probabilistic-bulk model of shallow convection over land”
Abstract ID: A31D-0111
Presenter: P. Gentine
Authors: P. Gentine; A. K. Betts; B. R. Lintner; K. L. Findell; F. D’Andrea


Obtaining the right diurnal cycle of both cloud cover and precipitation over land has been a longstanding issue in meteorology and climate. This has however fundamental repercussion for the study and prediction of land-atmosphere interactions. The difficulty of the representation of clouds over land compared to its oceanic counterpart is due to the large diurnal variability of the boundary layer induced by the diurnal solar heating of the surface. A better comprehension of shallow convection over land is a necessary step toward improved understanding and precipitation of cloud and precipitation processes over land. There have been recent important developments in our understanding of shallow convection over the ocean through large eddy simulation (Siebesma et al. 2003) and conceptual, toy model, studies (Bretherton and Park 2008). Over the land our understanding based on large eddy simulation studies (e.g. Brown et al. 2002) but there remains gaps in our conceptual understanding of the processes over land. We here present the first bulk model of shallow convection over land able to represent the transition between the different regimes observed over Summertime continents: dry boundary layer to forced cloud regime, forced cloud regime to (active) shallow convection and finally shallow convection to deep convection. For the first time a conceptual model is able to reproduce the timing of cloud cover and convection over land based on physical arguments. The idea behind the model is to introduce a probability density function at the land surface relating the variability of properties of the downdraft/updrafts (upward velocity, potential temperature and specific humidity) to the sensible and latent heat flux at the surface and to the mixed layer height. Those parcels are used to define the growth of the (dry) mixed layer and the cloud layer using a mass conservation argument as well as the buoyancy of the parcels, without the use of any entrainment velocity parameterizations. The bulk model is based on the conservation of potential temperature (reps. specific humidity) in the mixed layer and in the cloud layer. The enthalpy and moisture sources for the clouds are related to the parcels and their variability at the surface in a manner similar to Neggers et al. 2009. The forced cloud regime and the corresponding transition layer are demonstrated to be fundamental for the preconditioning of the environment to active convection. Without this preconditioning active convection cannot be triggered.

Session: H31C. Quantifying Pathways of Land-Atmosphere Coupling in Models and Observations II (Posters)
8:00 pm to 12:20 pm
Topic: Hydrology (H)
Location: Halls A-C (Moscone South)
Co-Sponsor(s): Atmospheric Sciences (A)

“Assessing the Evaporation-Precipitation Feedback over North America in GFDL’s AM2.1 Atmospheric Model.”
Abstract ID: H31C-1166
Presenter: A. M. Berg
Authors: A. M. Berg; K. L. Findell; P. Gentine; B. R. Lintner; C. Kerr


Land-atmosphere interactions are recognized as a major component of the physical climate system. One of the key features of those interactions is the feedback of soil moisture on precipitation, which reflects the coupling between soil moisture and evapotranspiration on the one hand, and between evapotranspiration and precipitation on the other hand. Observational constraints on this feedback – in particular its atmospheric branch – have so far been missing, mostly because of the lack of adequate large-scale observations of soil moisture and surface energy fluxes. Using the NARR reanalysis data (North American Regional Reanalysis, Mesinger et al. 2006), Findell et al. (2011) recently provided an assessment of the impacts of surface evaporative and sensible heat fluxes on the frequency and intensity of afternoon convective rainfall over North America. Here, we apply the same metrics to simulations from the GFDL’s atmospheric model, AM2.1. Using AMIP-like experiments, we show that the model tends to correctly reproduce the first order spatial pattern – as well as seasonality – of the sensitivity of afternoon rainfall frequency and intensity to the evaporative fraction over North America: an increase of rainfall probability with higher evapotranspiration in the Eastern US and in Mexico, albeit with no direct effect on rainfall amounts. Beyond this broad geographical agreement, the ability of the model to realistically represent the physical relationship between surface fluxes, boundary layer processes and precipitation is investigated. Particular attention is given to the dependency of model errors (in terms of feedback representation) on model climatic biases, e.g. here in rainfall (biased rain amounts, “drizzle” intraseasonal distribution), which propagate to the subsequent surface fluxes partitioning. References:- Mesinger, F. et al, 2006: North American regional reanalysis. Bull. Am. Meteorol. Soc. 87, 343§360. – Findell, K., P. Gentine, B. R. Lintner, and C. Kerr, 2011: Probability of afternoon precipitation in eastern United States and Mexico enhanced by high evaporation. Nature Geoscience, 4, 434-439.

Session: H32C. Hydrology and Earth Sciences in Developing World Communities I (Oral Presentations)
10:20 am to 12:20 pm
Topic: Hydrology (H)
Location: Room 3016 (Moscone West)
Co-Sponsor(s): Co-Sponsor(s): Education (ED) Global Environmental Change (GC) Public Affairs (PA)

“Developing Hydrology or Hydromorphology: A modern research agenda that can inform the trenches.”

Abstract ID: H32C-02
Presentation Time: 10:35 am to 10:50 am
Presenter: U. Lall
Authors: U. Lall


The pace of change in the developing world is dramatic. As the “developed” economies focus on environmental restoration, the developing countries are marked by a rapid transformation of the landscape accompanied by pressures of resource extraction and development. At one level, the considerations for large water projects are not fundamentally different than those that were faced when the United States or Australia underwent a rapid development cycle. On closer inspection, we note that in countries such as India and China the recent development pressures come at a time when the cumulative effects of past modification of the hydrologic system – water quantity, quality, ecosystem functioning – have already led to significant degradation of function. Even this situation is not dissimilar to what was experienced in parts of Europe at one time. However, the combination of population pressures, a segregated economy, and the local pressures induced by globalization and global environmental changes are unprecedented. The emergence of the movements towards “small is beautiful” and the push towards decentralized infrastructure in this setting are consequently not a surprise. However, the broad replication of such measures without significant planning, regulation or scientific information that connects local, watershed and river basin impacts could lead to a hydromorphic transformation that is unprecedented in the history of man. The interplay between water and humans has shaped watersheds and societies for millennia, and hydromorphology refers directly to the nascent science of how the spatio-temporal dynamics of such systems plays out given the geometric and geological constraints of a river basin, and the operational, ever changing climate. Theories of such evolution may be self-evident, but need to be formally developed. The developing world provides an amazing opportunity to both develop such a laboratory, and to also influence the course of its evolution for synergistic improvements in the long-term outcomes for humans and watershed systems. I discuss how an interdisciplinary, experimental and theoretical approach to hydromorphology could be fostered with a developing country focus, and could potentially inform environmental restoration goals in developed countries as an end point.

December 8, 2011

Session: H42D. Freshwater, Ecosystem, and Agriculture Sustainability Under Climate and Land Use Change I
10:20 am to 12:20 pm
Topic: Hydrology (H)
Location: Room 3010 (Moscone West)
Co-Sponsor(s): Global Environmental Change (GC)

“The water-energy-food-climate-economics nexus: solving hunger and resource scarcity (Invited)”

Abstract ID: H42D-01
Presentation Time: 10:20 am to 10:35 am
Presenter: U. Lall
Author: U. Lall


A nexus refers to the core or to interconnectivity across issues. Addressing the boundary interactions of traditional sectors in an interconnected world as human activities change the physical boundaries of land and climate is an emerging academic and governance discourse. Through contrasting examples from the US and India, I shed light on the descriptive aspects of these connections and feedbacks that define potential impacts or traps for societies, and ponder whether a massive conceptual or numerical Earth System Model can help inform outcomes, or whether there are dominant links at particular scales (physical, social, economic or biological) that characterize the emergent dynamics and define critical equilibrium or transient solutions in certain places. However, the real question is what next given the definition of the nexus? Here, I argue that given the current valuation and management structure of different resource sectors and the associated information flows and sensitivities, the interlinked energy-climate issues can emerge as useful drivers of improved productivity in water-food systems, thus promoting resource and environmental sustainability while promoting economic development. Thus, levers can be found that help steer the course of these complex interacting systems towards desirable sectoral outcomes.

Session: H43A. Advances in Hydrometeorological Predictions and Applications III Posters
1:40 pm to 6:00 pm
Topic: Hydrology (H)
Location: Halls A-C (Moscone South)
Co-Sponsor(s): Atmospheric Sciences (A)Natural Hazards (NH)

“Predictability and Diagnostics of Western Himalayan Hydro-climatology”
Abstract ID: H43A-1172
Presenter: I. Pal
Authors: I. Pal; U. Lall; A. W. Robertson; M. A. Cane


Snowmelt dominated streamflow of the Western Himalayan rivers is an important water resource during the dry pre-monsoon months to meet the irrigation and hydropower needs in northern India. On the other hand, winter precipitation as the form of snow over Himalayas helps in maintaining the glaciers, which serve as a storehouse of freshwater throughout the year. With the help of the hydro-climatological data provided by the Bhakra Beas Management Board in India, we present the outcome of our research on the prediction and diagnostics of Satluj river basin hydro-climatology at the Indian side up to the upstream of Bhakra dam, which is a major source of water for irrigation and electricity generation (1325MW) for north India. Spring seasonal inflow anomalies to Bhakra dam are strongly correlated with large-scale precipitation and temperature in the preceding winter over the Western Himalayas and adjoining north and central Indian plains, suggesting a potentially usable predictability for reservoir managers. Winter precipitation in the Western Himalayas is mainly brought about by the mid-latitude jet stream leading to the formation of low-pressure synoptic systems known as Western Disturbances (WD). WDs originate over the North Atlantic Ocean or Mediterranean Sea, with secondaries developing over the Persian Gulf and Caspian Sea either directly or as a result of the arrival of low-pressure systems from southwest Arabia, and travel eastward over Iran, Afghanistan, Pakistan, and northwest India. Winter WDs (and therefore the average volume of winter precipitation over Western Himalayas) are also modulated by the large-scale interaction between ocean and atmosphere led by the variation of the SSTs of the Indian Ocean and Pacific. As a result, average spring inflow volume, which is a function of the average volume of precipitation in winter, was also found to be positively correlated with the SSTs over the western and equatorial Indian Ocean, and with below-normal sea-level pressures centered over the Azores, both during the preceding winter. Teleconnections of winter precipitation and spring Bhakra inflow with the El-Nino indices in winter are also noted, which provide some promise for improving the long lead prediction capability for inflows into this important multi-purpose reservoir that is operated at seasonal time scales for irrigation, flood control and hydropower production. They also provide potential directions for the statistical downscaling of precipitation, temperature and/or streamflow directly from large-scale climate model simulations of ocean temperature and atmospheric pressure fields.

December 9, 2011

Session: GC51D. Climate Extremes V (Posters)
8:00 am to 12:20 pm
Topic: Global Environmental Change (GC)
Location: Halls A-C (Moscone South)
Co-Sponsor(s): Global Environmental Change (GC)

“Extreme precipitation in Europe over the last century: a climate perspective.”
Abstract ID: GC51D-1002
Presenter: F. Cioffi
Authors: F. Cioffi; C. Karamperidou; C. B. Krishnamurthy; U. Lall


We analyze over a century of continuous rainfall data available from the ECA&D archive for spatio-temporal trends in extreme precipitation. The data base includes 515 stations with records longer than 100 years. For each station, we identify daily rainfall events in the winter 6 months (Oct-Mar) that exceed the 99th percentile of daily rainfall. An annual time series of the frequency of such events is created, as well as an annual time series of the average daily rainfall in these events. Space and time analyses of the variation of the frequency and intensity time series are then pursued using multivariate time and frequency domain (multi-taper method) methods.The key trends and organized spectral modes identified are related to potential anthropogenic change and to well established climate indices (e.g., NAO, EAWR and SL). The simultaneous analysis of monotonic trends over the secular period and quasi-oscillatory phenomena is informative as to the attribution of changes in extreme precipitation over the region. The spatial patterns associated with each quasi-oscillatory mode and the “trend” signal are identified, and an envelope of the time reconstruction centered at the key frequency bands deemed significant is also identifies and related to potential teleconnections through correlation with key atmospheric circulation indices and SST fields. The potential implications for future risks are discussed in the context of a Global Flood project that aims to characterize the climate risk factors and develop instruments for prediction and mitigation of these risks.

“Low-frequency modulation of large-scale weather regimes and impacts on extreme flooding over the Midwest of the United States”

Abstract ID: GC51D-1018
Presenter: A. W. Robertson*
Authors: A. W. Robertson*; Y. Kushnir; U. Lall; J. Nakamura


The April 2011 flood event in Ohio River Basin and related lower Mississippi River floods was the latest of a set of major such flooding events recorded over the twentieth century (defined in terms of a 10-year return maximum in streamflow). Composite analysis of these events reveals an anomalous northward moisture transport in a moist conveyor belt from the Gulf of Mexico and the tropical Atlantic, focused by convergence associated with the “Bermuda High” and the synoptic events impinging on it. The questions of whether the recent 2011 event presages more frequent extreme floods in the future, and the degree of potential climate predictability of such events both require a better understanding of how the frequency and intensity of the synoptic events responsible for the floods vary on interannual to interdecadal timescales, and are thus potentially influenced by large-scale modes of low frequency climate variability. Here we present an analysis of daily weather regimes derived from NCEP-NCAR reanalysis wind data using a K-means analysis for the March–May season, 1961–2011, together with a complementary analysis of daily rainfall station data over the Ohio River Basin for the same period using a hidden Markov model (HMM). Flooding weather regimes will be identified and interpreted, both synoptically in terms of isentropic potential vorticity diagnostics, as well as in terms of low-frequency modulation over time associated with teleconnection patterns such as ENSO, PDO, and the NAO.”

GC51E. Climate Extremes VI (Posters)
8:00 am to 12:20 pm
Topic: Global Environmental Change (GC)
Location: Halls A-C (Moscone South)
Co-Sponsor(s): Co-Sponsor(s): Atmospheric Sciences (A)Global Environmental Change (GC)Hydrology (H)Nonlinear Geophysics (NG)Ocean Sciences (OS)

“The historical impact of climate extremes on global agricultural production and trade”
Abstract ID: GC51E-1031
Presenter: T. J. Troy*
Authors: T. J. Troy*; I. Pal; P. J. Block; U. Lall


How does climate variability at interannual time scales impact the volume and prices of key agricultural products on the global market? Do concurrent climate shocks in major breadbaskets of the world have serious impacts on global stocks and food prices? To what extent may irrigated agriculture or food storage buffer such impacts? Is there evidence of such impacts and/or buffering in the publicly available historical data? This talk explores these questions through empirical data analysis. During the past two years, we have seen drought in China, Europe, and Russia and floods in the United States and Australia. In this study, we examine the relationship between climate and crop yields, focusing on three main grain staples: wheat, rice, and maize. To do this, we use global production, trade, and stock data from the Food and Agricultural Organization and the United States Department of Agriculture for agriculture information and gridded observations of temperature and precipitation from 1960 through 2008. We focus on the impact of climate shocks (extreme temperatures, drought, and floods) on the agricultural production for the top exporting countries and quantify how these shocks propagate through the country’s exports, imports, and grain stocks in order to understand the effect climate variability and extremes have on global food security. The ability to forecast these climate shocks at seasonal to longer lead times would significantly improve our ability to cope with perturbations in the global food supply, and we evaluate the ability of current models to produce skillful seasonal forecasts over the major grain producing regions.

NG52A. Stochasticity, Multiplicity of Scales, Memory, and Thermodynamics in Geophysics II (Oral Presentations)
10:20 am to 12:20 pm
Topic: Nonlinear Geophysics (NG)
Location: Room 304 (Moscone South)
Co-Sponsor(s): Atmospheric Sciences (A)Earth and Planetary Surface Processes (EP)Global Environmental Change (GC)Hydrology (H)Ocean Sciences (OS)Seismology (S)Tectonophysics (T)

“Decadal ENSO variability as reflected by Local Lyapunov Exponents.”
Abstract ID: NG52A-03
Presentation Time: 10:50 am to 11:05 am
Presenter: C. Karamperidou
Authors: C. Karamperidou; M. A. Cane; A. T. Wittenberg; U. Lall; P. N. Di Nezio


Body: Decadal variability of ENSO is present in historical and paleo records, and has been simulated by a hierarchy of dynamical and statistical models. The ENSO variability in the IPCC AR4 Coupled GCMs ranges from constant periodicity or amplitude to significant inter-decadal variability in both period and amplitude. While long runs of intermediate dynamical models that exhibit inter-decadal and inter-centennial variability, such as the ZC model, have been a subject of numerous studies, only recently have long runs of coupled GCMs, such as the GFDL CM2.1 2000-yr control run, become available. The presence of such rich variability in the absence of external forcing that could induce persistent regimes, along with the length of the simulation, provides new ground for investigation of the causes of long-term modulation of ENSO behavior and the implications for predictability at multiple time-scales from the short-range to the decadal.In this work, we investigate ENSO predictability in long unforced runs of a fully coupled GCM (GFDL’s CM2.1) and the intermediate ZC model in a dynamical systems theory context. We compute the Local Lyapunov Exponents (LLEs) of the NINO3 time series, and use them as a means of classifying epochs of distinct ENSO behavior. The ‘loss’ or ‘gain’ of predictability across these epochs and their relation to the physical evolution of the ENSO events is examined. The correspondence of the LLE statistics with prediction error in ‘perfect-model’ reforecasts is also discussed.

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