Past Seminars at COLA

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2010 Seminars at COLA
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Title: NOAA CTB - Towards a Global Drought Monitoring and Forecasting Capability
Speaker: Prof. Eric F. Wood
Affiliation: Dept. of Civil and Environmental Engineering, Princeton University
Date: Wednesday, January 13, 2010 at 2:00 p.m.
Title: Observed 20th Century Climate Variability
Speaker: Prof. Mike Wallace
Affiliation: University of Washington
Date: Thursday January 14, 2010 at 11:00 a.m.
Title: Climate Variability and Climate Change Over South America
Speaker: Paula Gonzalez
Affiliation: Research Center of the Sea and Atmosphere (CIMA)
Date: Friday, February 5, 2010 at 11:00 a.m.
Abstract: Different aspects of climate variability and climate change over South America will be discussed, with a special emphasis on the La Plata Basin region for its social and economic relevance. An assessment of the ability of state-of-the-art coupled general circulation models from the WCRP/CMIP3 project in reproducing particular features of intraseasonal to interannual variability over the region will be presented. The uncertainties of climate change projections for the region will be discussed, along with some simple examples of interdisciplinary impact studies.
Title: CTB Seminar Series: NASA Multi-Scale Modeling System with United Physics
Speaker: Wei-Kuo Tao
Affiliation: Laboratory for Atmospheres, NASA, GSFC
Date: Tuesday, February 9, 2010 at 2:00 p.m.
Title: The Brazilian Effort Toward an Earth System Model
Speaker: Paulo Nobre
Affiliation: Center for Weather Forecast and Climate Studies - CPTEC / National Space Research Institute - INPE
Date: Wednesday, March 10, 2010 at 3:00 p.m.
Abstract: This talk describes the efforts underway in Brazil toward the construction of a fully coupled earth system model. The development is orchestrated by INPE/CCST and is based on INPE coupled ocean-atmosphere general circulation model (CGCM), whose atmospheric component is CPTEC AGCM (which itself is an improved, F90, MPI, version of the 1994's COLA AGCM) and the ocean component is GFDL's MOM4. Improved land surface model (NCAR's IBIS) and atmospheric chemistry, as well as ocean ice and biogeochemistry (from MOM4) are standard features being included in the ESM. All model components are coupled trough GFDL's Flexible Modular System - FMS coupler.
Title: Why Does a GCM with an Embedded Cloud Resolving Model have an Improved Diurnal Cycle of Rainfall?
Speaker: Mike Pritchard
Affiliation: University of California, Scripps Institution of Oceanography
Date: Friday, March 19, 2010 at 11:00 a.m.
Abstract: Getting the diurnal rainfall cycle right in global climate models (GCMs) remains a stumbling block for the earth system modeling community. A new climate simulation technology may offer a way forward - the "multi-scale modeling framework" (MMF) approach, i.e. replacing the cumulus parameterization in a GCM with thousands of tiny, interactive, idealized embedded cloud resolving models (CRMs). The statistical character of simulated global composite diurnal rainfall in an MMF is remarkably realistic, and new modes of regional diurnal convective variability are seen to emerge that are not simulated by GCMs, including long-lived propagating warm season nocturnal convection in the lee of the Rockies. In trying to understand how/why these diurnal rainfall improvements occur, we present an updated conceptual model of how the scale interface in an MMF works. New clues are drawn about the physical processes that enable its improved diurnal cycle by comparing budget diagnostics of tropical and central US diurnal phenomena in a GCM both with and without an embedded cloud resolving.
Title: CTB Seminar Series: The Impact of Coupled Versus Observed SST on Summer Season Predictions over America with the NCEP CFS Using Different Land Surface Models and Different Initial Conditions
Speaker: Rongqian Yang
Affiliation: Environmental Modeling Center
Date: Wednesday, March 24, 2010 at 2:00 p.m.
Title: Remote Sensing of Cloud Feedback: Comparison with Model Simulations
Speaker: Suki Manabe
Affiliation: Princeton University
Date: Thursday, May 27, 2010 at 3:30 p.m.
Abstract: Large uncertainty still remains about the sensitivity of climate. The uncertainty is attributable in no small part to our inability to reliably determine the influence of cloud upon the strength of radiative feedback that controls the sensitivity of climate. Here we describe our recent attempt to study this problem through remote sensing from satellites.
Title: Comparison of two NOAA/GFDL coupled climate models (CM2G and CM2M) over North Pacific
Speaker: Young-Gyu Park
Affiliation: Princeton University Home Institute, Principal Research Scientist, Korea Ocean Research and Development Institute, Ansan, Korea - Current position, Visiting Research Scholar, GFDL
Date: Tuesday, July 20, 2010 at 11:00 a.m.
Title: Tropical Pacific Ocean in a warming climate
Speaker: Dr, David wang
Affiliation: Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory, Columbia University
Date: Wednesday, July 21, 2010 at 11:00 a.m.
Abstract: The tropical Pacific region is an essential part of global climate system. Recent studies suggest a number of robust global warming signatures in the tropical Pacific region, particularly the weakening of the Walker circulation. The present study further investigates the response of the tropical Pacific Ocean to future greenhouse warming in three aspects: the shallow meridional overturning circulation or subtropical cell (STC), the ventilation of the equatorial thermocline and undercurrent (EUC), and the regional sea level, in the framework of CMIP3 multi-model climate projection. First, it is found there is a contrasting tendency for the STC to be weakening (strengthening) in the northern (southern) hemisphere in the 21st century, consistent with large-scale surface wind change under global warming. The pycnocline transport convergence, as the equatorward branch of the STC, exhibits a robust weakening of about 3 Sv. The weakening mainly takes place in the ocean interior, consistent with the zonal slackening of the tropical pycnocline, whereas the change of the pycnocline transport along the western boundary is relatively small, affected by the shoaling of the pycnocline base. In addition, the Indonesian throughflow transport above the pycnocline base shows a robust weakening of about 1.5 Sv. Second, the source regions and transit time distributions of the EUC water are investigated using a simulated adjoint passive tracer for both the present-day climate and a warmer climate. Several major source regions are identified and associated with different transit times. In a warmer climate, the distribution of source waters are largely unchanged and the transit time becomes slightly younger. The warming of the EUC water can be traced back to the extra-tropical surface warming. Finally, it is found that the projected sea level change in the tropical Pacific region can be well reproduced by a linear, wind-driven model that embodies only baroclinic wave dynamics, especially when both the surface wind change and ocean stratification change are taken into account.
Title: Two types of El Nino and Their Climate Impacts
Speaker: Jong-Seong Kug
Affiliation: Korea Ocean Research and Development Institute
Date: Thursday, August 5, 2010 at 11:00 a.m.
Abstract: In this study, two types of El Nino events are classified based on spatial patterns of sea-surface temperature (SST) anomaly. One is cold tongue (CT) El Nino, which can be regarded as the conventional El Nino, and the other is Warm Pool (WP) El Nino. The CT El Nino is characterized by relatively large SST anomalies in the NINO3 region, while the WP El Nino is associated with SST anomalies mostly confined to the NINO4 region. In addition, spatial patterns of many atmospheric and oceanic variables are also distinctively different for the two types of El Nino events. Furthermore, difference in the transition mechanism between two types of El Nino is clearly identified. That is, the discharge process of the equatorial heat content associated with the WP El Nino is not efficient due to the spatial structure of SST anomaly; as a result, it cannot trigger a cold event. It is also demonstrated that the zonal advective feedback (i.e., zonal advection of mean SST by anomalous zonal current) plays a crucial role in the development of a decaying SST anomaly associated with the WP El Nino, while the thermocline feedback is a key process during the CT El Nino. In addition we show changes in the ratio of WP El Nino to CT El Nino under projected global warming scenarios from the Coupled Model Intercomparison Project phase 3 multi-model data set. Using calculations based on historical El Nino indices, we find that projections of anthropogenic climate change are associated with an increased frequency of the WP El Nino compared to the CT El Nino. When restricted to the six climate models with the best representation of the twentieth-century ratio of WP El Nino to CT El Nino, the occurrence ratio is projected to increase as much as five times under global warming.
Title: The Eastern Mediterranean teleconnection Pattern: structure, dynamic mechanisms of formation and impact on present and future regional climate
Speaker: Dr. Maria Hatzaki
Affiliation: Institute of Environmental Research and Sustainable Development, National Observatory of Athens
Date: Thursday, August 12, 2010 at 11:00 a.m.
Abstract: Teleconnection patterns appear as preferred modes of natural variability of low frequency atmospheric circulation, with fixed centers of action. Their examination is of great interest in the field of atmospheric dynamics and climate variability, as they influence the regional climate and the occurrence of extreme weather events. The existence of teleconnection patterns centered in Eastern Mediterranean, a region with intense topographic features and limited climatological research, was examined through the climatological data analysis of the Northern Hemisphere geopotential heights, for the period 1958-2003. This analysis leaded to the identification of a teleconnection pattern, in the winter fields of 300 and 500 hPa geopotential heights, with its poles located over Eastern Mediterranean and Northeastern Atlantic, respectively, and it will be referred to as Eastern Mediterranean teleconnection Pattern (EMP). An index, the EMP Index, was defined in order to discriminate the two phases of the pattern, the positive and the negative and that could be applied in the dynamical study of EMP and its impact on regional climate. During positive (negative) phase of EMP, strong anomalous anticyclonic (cyclonic) circulation prevails over northeastern Atlantic, while a weaker anomalous cyclonic (anticyclonic) exists over Eastern Atlantic, leading to an increased meridional (zonal) circulation over Europe and Mediterranean. The frequency analysis revealed that the prevailing frequencies of EMP classify the pattern in the intermediate scale of variability (10-30 days). The instant frequencies analysis of the Hilbert-Huang transformation was applied, in order to find the temproral period of each winter, during which the EMP signal is maximized. The theoretically proposed processes and mechanisms that lead to the formation of teleconnection patterns were examined: a) in planetary scale, the Rossby wave propagation from orographic or thermal forcing, b) in synoptic scale, the influence of transients (eddies defined as departures from time mean zonal circulation) and c) interaction between stratosphere and troposphere.
Studying the aforementioned processes, it was found that the positive phase of EMP forms when a forcing of tropical heating appears in tropical Pacific, along with an anomalous southern flow over the region of north Pacific. As a consequence, a Rossby wave-train propagates initially to the northeast and then it obtains a zonal structure over Atlantic and Europe, forming a ridge over Atlantic and a trough over eastern Mediterranean. The polar frontal jet shifts northward, having an anticyclonic circulation that creates a blocking system and so the storm track moves to the north. As the jet moves across Scandinavia, the transient eddies activity becomes enhanced taking energy from the mean flow, while in the mid-latitude Atlantic the existence of low-frequency eddies decelerates the mean flow, enhancing the blocking system. During the negative phase, the existence of a tropical heating does not seem to force a wave-train propagation to the mid-latitudes. The Rossby wave-train has a zonal structure, while the Rossby waves are not clearly formed on the westerly flow. This fact is confirmed by the polar jet, which has zonal structure and comes charging into Europe. The northern pole of the pattern forms at the poleward side of the jet, while the southern pole forms at the equatorward side of the jet, due to the anticyclonic shear at this side of the jet and the topography of this region. The role of transient eddies in this case is to enhance the westerly flow.
The study of the interaction between stratosphere and troposphere, through tropopause dynamics, showed that the Atlantic storm track follows a different life cycle during each phase of the pattern. In the positive phase, the wave is dominated by a NE-SW shear then the trough becomes thinner, producing finally a cut-off cyclone. In the negative phase, there is less equatorward movement of the trough and the wave has a broader zonal structure. The impact of each phase of EMP on mean regime of temperature and precipitation along with their extreme events was examined applying the Regularized Canonical Correlation Analysis (RCCA) and the analysis of the composite anomalies on the respective parameters. It was found that EMP indeed affects the mean winter patterns of temperature, precipitation and their extreme events inversely between the two phases. In particular, the positive (negative) phase of EMP is related to a decrease (increase) of temperatures and an increase (decrease) of precipitation. The extreme events of precipitation increase (decrease), the dry spells decrease (increase) and the extreme cold (warm) events intensify, during positive (negative) phase. Moreover, an attempt was made to estimate the impact of the EMP on the temperature and precipitation regimes of north-western Europe and the British Isles. It was found that the EMP affects the regional climate with inverse impact between the two phases. Finally, a possible change in the position and strength of EMP in the future and its resulting impact on regional climate of Eastern Mediterranean were investigated. The knowledge of the behavior of teleconnection patterns in the future could lead to an improvement of climate models simulations. Future climate data were used (2070-2100) based on two IPCC emission scenarios for the evolvement of the future atmospheric concentrations of greenhouse gases, and their respective control run, as derived from the general circulation model HadAM3P and the respective regional model HadRM3P. Even serious uncertainties and limitations related to the future climatic scenarios have been stressed by the international bibliography and the results of this study for the future impact of EMP should be considered with caution, it was found that EMP still exists in the future for both scenarios and affects the future regional climate in similar ways.
Title: The Future of Climate Science
Speaker: Bob Bishop
Affiliation: ICES Foundation
Date: Friday, September 17, 2010 at 11:00 a.m.
Abstract: High Performance Computing is currently deployed in several centers for climate research, but not at the levels needed to achieve substantial success on a global basis, given the complexity of the problem. A quantum leap in capabilities will be necessary to handle next-generation climate models that integrate newly emerging sciences, high-resolution grids, and voluminous observational data from satellites and sophisticated ground devices. Dr. Bishop will discuss efforts to build an International Centre for Earth Simulation (ICES) based in Switzerland that takes an holistic systems approach, and that has the competence and resources to achieve new insights in this new decade, and is capable to globally influence public policy with respect to weather, climate, environment, disaster risk reduction and socio-economic development.

On this progressively crowded and fragile planet, such a capability will be invaluable, Bishop believes, if not imperative, for our long-term survival. ICES could serve as a test-bed for large scale public and private development planning. Decision makers could ask ‘what if’ questions for major construction projects (such as China’s Three Gorges Dam), and then interactively evaluate alternative scenarios. Likewise, ICES could help uncover the possible unintended consequences of climate remediation and adaptation strategies, geo-engineering ideas, CO2 sequestration, deep sea drilling, etc. ICES would be a resource for building more resilient societies in an era of rapid climate change and frequent natural disasters (such as flooding, extreme weather events and volcanic ash clouds), and therefore of great consequence to our future well-being. It would ultimately play a major role in the education and training of policy-makers, the public, and future Earth Scientists - in conjunction with the current national and regional centers

Title: A Hybrid Lagrangian/Eulerian View of the Atmospheric Mass Circulation: Preliminary Results
Speaker: Professor Ming Cai
Affiliation: Department of Earth, Ocean, and Atmospheric Science, Florida State University
Date: Tuesday, November 2, 2010 at 11:00 a.m.

n this talk, I will present some preliminary results of an on-going diagnostics study of the seasonal cycle, intra-seasonal, and inter-annual variability of global mass circulation, and its relation with the climate variability in various fields, such as temperature, geopotential height, surface pressure, static stability, wind, potential vorticity and E-P
flux using daily NCEP-NCAR reanalysis (1979-present). The primary objectives of our diagnostics analysis are (i) to delineate the simultaneous couplings among diabatic heating, meridional mass transport, meridional angular momentum transport, and form drag associated with baroclinically amplifying waves, (ii) to link the extratropical
stratosphere-troposphere coupling to the tropical-extratropical coupling, and (iii) to understand climate variability/changes from global atmospheric mass circulation perspective.

The global mass circulation links the tropics to the extratropics and the stratosphere to the troposphere. Such a global mass circulation consists of a (meridionally) broad Hadley cell in the tropics and a succession of wave-driven cells in the extratropics. Collectively, these circulation systems move warm air poleward aloft and cold air equatorward near the surface. The meridional divergence of warm air mass aloft and convergence of cold air below correspond to adiabatic rising motions whereas the convergence of warm air aloft and divergence of cold air below correspond to adiabatic descending motions. The adiabatically rising air mass is diabatically heated in the tropics and flows poleward where it sinks and loses its heat diabatically. The cold air mass comes back to tropics through the equatorward mass transport and diabatic heating. In the extratropics, the mass circulation is carried out mainly by baroclinically amplifying (or westward tilting) Rossby waves. The westward tilting waves are responsible for a net poleward mass transport aloft and equatorward mass transport below. Accompanied with the wavedriven
mass circulation are the accumulation of westerly angular momentum aloft and easterly angular momentum below, giving rise to a poleward shifting or intensification of westerly jet aloft. The westward tilting waves also act to transfer westerly angular momentum downward via form drag. The downward transfer of westerly angular momentum weakens the jet aloft and neutralizes the accumulation of easterly angular momentum below, paving the way for the further poleward advancement of warm air mass and equatorward advancement of cold air mass. The downward transfer of westerly momentum is responsible for prevailing surface westerly flow at the extratropics where the westerly angular momentum is removed by topographic form drag and surface friction.

The temporal and spatial variation of the warm air branch is synchronized with the cold air branch in the troposphere below. Because the pole is the destination point of the warm air branch and the beginning point of the cold air branch, the synchronized poleward warm air advancement and equatorward cold air movement would lead to a
strong stratosphere-troposphere coupling over the polar region.

Title: Coupled Model Data Assimilation for Climate Estimation and Prediction
Speaker: Dr. Shaoqing Zhang
Affiliation: GFDL
Date: Thursday, November 4, 2010 at 2:00 p.m.

A coupled climate model simulates reasonably the interactions of major components of the climate system, such as the atmosphere, ocean, land and sea-ice. However, due to insufficient observations and incomplete understanding of the physical processes involved, model simulations show biases in the mean and variability of the climate. For climate estimation and forecast/prediction initialization, coupled data assimilation uses coupled model dynamics to extract observational information and reconstructs the historical and present states of climate. Here we show how a fully-coupled data assimilation system is able to integrate the earth system observations and applied to detecting climate predictability and initializion of seasonal-interannual to decadal predictions.

Title: Poleward propagation of boreal summer intraseasonal oscillations in a coupled model: Role of internal processes
Speaker: Dr. Ajayamohan
Affiliation: CCCMA, University of Victoria
Date: Wednesday, November 10, 2010 at 11:00 a.m.

This study compares the simulated poleward migration characteristics of boreal summer intraseasonal oscillations (BSISO) in a suite of coupled ocean–atmospheric model sensitivity integrations. The sensitivity experiments are designed in such a manner to allow full coupling in specific ocean basins but forced by temporally varying monthly
climatological sea surface temperature adopted from the fully coupled model control runs. The hypothesis that internal process, namely, the interaction between moist physics and equatorial waves, plays an important role on the poleward propagation of BSISO over south Asia is tested. Specifically, the relative role of local air-sea interaction versus internal processes in moistening the boundary layer ahead of convection is examined.