Seminars at COLA

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Upcoming Seminars at COLA
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Title: The Science in Adaptation
Speaker: Ed Sarachik
Affiliation: University of Washington
Date: Monday, May 2, 2010 at 3:30 p.m.
Abstract: We introduce the concept of adaptation to the impacts of future climate conditions being careful to:
* Consider who does the adapting and therefore the spatial scales on which adaptation is possible
* Consider the time scales on which adaptation can be done with special emphasis on the annual time scale
* Relate near and long term adaptation
* Distinguish the roles of high and low frequency climate variations
* Indicate which aspects of climate are important
* Assess whether or not the climate enterprise as it is currently practiced provides enough information for successful adaptation
* Criticize the IPCC for its near total disregard of climate variability.
The takeaway message is: mitigation is about climate trends for which the IPCC is adequate. Adaptation is about climate variability which puts much more stringent conditions on our ability to deliver useful climate information.
Slides: TheScienceInAdaptation.pdf
Title: The Asian Monsoon in the Super-Parameterized CCSM and its Relationship to Tropical Wave Activity
Speaker: Charlotte DeMott
Affiliation: Colorado State University
Date: Monday, April 25, 2011 at 2:00 p.m.
Abstract: The Asian monsoon is evaluated in three general circulation models (GCMs): CCSM (coupled, conventional convection), SP-CAM (uncoupled, SP convection) and SP-CCSM (coupled, SP). Adding SP improves tropical variability, the simulation of easterly zonal shear over the Indian and western Pacific Oceans, and increases negative sea surface temperature (SST) biases in that region.
SP-CCSM is the only model to reasonably simulate the eastward-, westward-, and northward-propagating components of the Asian monsoon. SP-CCSM produces a variety of tropical waves with spectral characteristics similar to those in observations. Simulated equatorial Rossby (ER) and mixed Rossby-gravity (MRG) waves may lead to different simulations of the NPISO in each model. Each model exhibits some northward propagation for ER waves, but only SP-CCSM produces northward-propagating MRG waves, as in observations. The combination of ER and MRG waves over the Indian Ocean influences the spatio-temporal structure of the NPISO, and contributes to the differences seen in each model.
The role of ocean coupling must be considered in terms of the timescale of the SST response compared to the timescale of tropical variability. High-frequency disturbances experience coupling via its changes to the basic state, while lower-frequency disturbances may respond directly to SST fluctuations.
Title: ITCZ Shifts in Simulations of Global Warming
Speaker: Dargan Frierson
Affiliation: University of Washington, Department of Atmospheric Sciences
Date: Wednesday, April 13, 2011 at 11:00 a.m.
Abstract: We introduce a new theoretical framework to help interpret why comprehensive climate models differ in their projections of how much the ITCZ will shift with global warming. The framework is based on fundamental energetic constraints of the system: since both moisture transports and energy transports within the deep tropical atmosphere are governed by the Hadley circulation, a southward shift of the ITCZ is associated with a northward transport of moist static energy. This situation is typically associated with enhanced heating of the Southern Hemisphere, often due to hemispheric differences in aerosols, clouds, surface albedo changes. We show that the cross-equatorial energy flux is strongly anticorrelated with ITCZ shifts in several different warming scenarios, justifying the energetic framework. We then perform partitioning and attribution of the energy flux changes using the exact energy budget and an energy balance model. In many models extratropical forcing is the primary driver of ITCZ shifts, with clouds and surface albedo changes of key importance. In 20th century simulations, aerosol cooling of the Northern Hemisphere causes the ITCZ to shift southward in all models, of greatly varying degree.
Title: On the problem of hydrology and the human influence on climate
Speaker: Tom Chase
Affiliation: University of Colorado
Date: Friday, April 8, 2011 at 10:30 a.m.
Abstract: In current estimates, The H20 molecule completely dominates the effect of added CO2 in the atmosphere when considering human effects on climate and yet H2O is seldom identified in this way. H20 dynamics are also very poorly simulated in computer models, even at the controlled plot scale (spatial scale 1 m2), familiar to hydrologists. This raises questions on how global scale models with spatial scale four or more orders of magnitude higher handle this dominant influence when projecting climate change when relying on physical relations derived for the plot scale. I will give examples from research on Asian monsoons, southwestern US inversions and our look at the physical soundness of a well-known US national climate model.
Title: Climate variability and change in the land of the 6-inch monsoon
Speaker: Dave Gutzler
Affiliation: University of New Mexico
Date: Friday, March 18, 2011 at 11:00 a.m.
Abstract: The American Southwest features a seasonal cycle of precipitation that can be characterized as monsoonal, although absolute rainfall amounts are only a small fraction of seasonal monsoon rainfall across southern Asia. Nevertheless summer precipitation is integral to the health of ecosystems and millions of people in the semiarid southwestern states. Like the Indian or Southeast Asian monsoons, the North American monsoon provides a huge challenge for climate prediction efforts at time scales from seasonal variability out to century-scale change. Conceptual ideas for enhancement of seasonal and longer prediction skill, based on forcing from SST or land surface anomalies or widespread aerosol loading, can be applied to multiple monsoon systems. We will discuss efforts based on these concepts to diagnose and predict North American monsoon precipitation anomalies, and consider the rather dire longer-term climate change projections for this water-limited and population-stressed region.
Title: Test-Driven Development of Scientific Models
Speaker: Tom Clune
Affiliation: Software Integration and Visualization Office, NASA GSFC
Date: Wednesday, February 16, 2011 at 3:00 p.m.
Abstract: Test-Driven Development (TDD) is a software development process that promises many advantages for developer productivity and has become widely accepted among professional software engineers. As the name suggests, TDD practitioners alternate between writing short automated tests and producing code that passes those tests. Although this overly simplified description will undoubtedly sound prohibitively burdensome to many uninitiated developers, the advent of powerful unit-testing frameworks greatly reduces the effort required to produce and routinely execute suites of tests. By testimony, many developers find TDD to be addicting after only a few days of exposure, and find it unthinkable to return to previous practices. Of course, scientific/technical software differs from other software categories in a number of important respects, but I nonetheless believe that TDD is quite applicable to the development of such software and has the potential to significantly improve programmer productivity and code quality within the scientific community. After a detailed introduction to TDD, I will present the experience within the Software Integration and Visualization Office (SIVO) in applying the technique to various applications. This discussion will emphasize the various direct and indirect benefits as well as some of the difficulties and limitations of the methodology. I will conclude with a brief description of pFUnit, a unit testing framework I co-developed to support test-driven development of parallel Fortran applications.
Title: Prospects for Improving Subseasonal Predictions
Speaker: Kathy Pegion
Affiliation: CIRES/University of Colorado
Date: Monday, February 14, 2011 at 2:00 p.m.
Abstract: Extending atmospheric prediction skill beyond the predictability limit of about 10 days for daily weather rests on the hope that some time-averaged aspects of anomalous circulations remain predictable at longer forecast lead times, both due to the existence of natural low-frequency modes of atmospheric variability and coupling to a medium with larger thermal inertia, i.e. the ocean. In this project, the Week 2 and Week 3 forecast skill of two global coupled atmosphere-ocean models from NASA and NOAA are compared with that of much simpler Linear Inverse Models (LIMs) derived from observed time-lag correlations of atmospheric circulation anomalies in the northern hemisphere and outgoing longwave radiation (OLR) anomalies in the tropics. The coupled models are found to beat the LIMs only slightly, and only if an ensemble prediction methodology is employed. To assess the potential for further skill improvement, a predictability analysis based on the relative magnitudes of forecast signal and forecast noise in the LIM framework is conducted. Estimating potential skill by such a method is argued to be superior to using the ensemble-mean and ensemble-spread information in the coupled-model ensemble prediction system. The LIM-based predictability analysis yields relatively conservative estimates of the potential skill, and suggests that outside the tropics the average coupled-model skill may already be close to the potential skill, although there may still be room for improvement in the tropical forecast skill.
Past Seminars at COLA
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