Past Seminars at COLA

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2008 Seminars at COLA
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Title: The origins of ITCZs, monsoons, and monsoon onset
Speaker: Winston Chao
Affiliation: NASA Goddard Space Flight Center
Date: January 14, 2008 at 2:00 p.m.
Abstract: Intertropical convergence zones (ITCZs), monsoons and monsoon onset are among the most prominent of atmospheric phenomena. Understanding their origins is fundamental to a full understanding of the atmospheric general circulation and has challenged meteorologists for a very long time. There has been important progress in understanding these phenomena in recent years, and in this seminar, recent developments (mostly by the speaker) are reviewed. First, contrary to conventional belief, land-sea thermal contrast is not necessary for monsoons to form. Second, monsoon onset occurs when there is a sudden poleward jump of an ITCZ during its annual cycle of latitudinal movement. A monsoon, then, is an ITCZ after its poleward jump. Third, the SST latitudinal maximum is not the most significant, or even a necessary, factor in the formation of an ITCZ; there are other important, if not more important, factors. These factors are the interaction between convection and surface fluxes, the interaction between convection and radiation, and the earth's rotation. Finally, the recent understanding of how ITCZs form has led to a conceptual explanation for the origin of the double ITCZ bias in GCM simulations.
Title: CFS real-time forecast during 2005-2007
Speaker: Wanqiu Wang
Affiliation: Climate Prediction Center, NCEP/NOAA
Date: January 16, 2008 at 2:00 p.m.
Abstract: The NCEP Climate Forecast System (CFS) was implemented in Aug 2004 and is currently used as one of the forecast tools in the consolidation of the CPC/NCEP seasonal climate forecast.     In this study, we review CFS forecasts produced in real time for 2005-2007.   In particular, we will evaluate the CFS performance in reproducing the observed interannual variability.   We address the following questions: (1) to what extent does the CFS capture the observed surface air temperature and precipitation anomalies over North America; (2) how well does the CFS reproduce observed interannual sea surface temperature (SST) variations in the tropics and how do the real-time forecasts compare with the hindcasts; and (3) how do forecast errors in SSTs relate to errors in initial oceanic conditions, subseasonal high-frequency variability, and air-sea coupling?
Title: Decadal prediction: Closing the gap between climate projections and seasonal forecasts
Speaker: Noel Keenlyside
Affiliation: Keibniz Institute of Marine Sciences (IFM-GEOMAR)
Date: January 28, 2008 at 3:30 p.m.

Seasonal prediction is essentially an initial value problem, where as the climate projections of the IPCC are primarily a boundary value problem. Decadal prediction is both. As such, closing the current gap between seasonal prediction and climate change projections is important not only because of the clear socio-economic benefit, but also through contributing to reducing uncertainties in climate change projections.Presented here are seasonal-to-decadal hindcasts performed with the IPCC version of the MPI-OM/ECHAM5 climate model, and covering the period 1960-2005. Initial conditions for all hindcasts are obtained from coupled simulations in which model SST are relaxed towards observations. Radiative forcing is as observed or following the IPCC A1B scenario. Tropical Pacific and Indian Ocean SST variations are well predicted out to 6

Title: Climate variability and change in South America from WCRP/CMIP3 Models
Speaker: Carolina Vera
Affiliation: CIMA, University of Buenos Aires-CONICET, Buenos Aires, Argentina
Date: February 20 , 2008 at 2:00 p.m.

An assessment of the ability of 20th-century simulations from the WCRP/CMIP3 models in reproducing the seasonal, intraseasonal and year-to-year climate variations in South America will be presented. In addition, climate change projections over South America and the associated uncertainty issues will be also discussed. Models are able to reproduce in some extent the basic features of the precipitation seasonal cycle over South America; although the precipitation amounts in the SACZ, monsoon core, and La Plata Basin regions are not well represented. The spatial patterns of precipitation variability on interannual and intraseasonal time scales are somewhat represented by some of the models, although they lack in describing correctly the remote influence of forcing like ENSO, AAO. There is a generalized consensus among models that seasonal precipitation changes projected for the second half of 21C are mainly an increase of precipitation over southeastern subtropical South America and reduction along the southern Andes. However, current climate model projections over South America still exhibit a considerably large range of uncertainties that need to be reduced. Moreover, the physical explanation of those climate changes is not clear yet. Changes in the storm tracks as well as in the mean conditions of the tropical regions might have a role in explaining them.

Title: NCEP’s GODAS and Global Oceanic Monitoring Products
Speaker: Yan Xue
Affiliation: Climate Prediction Center, NCEP, NOAA
Date: February 27 , 2008 at 2:00 p.m.

An operational Global Ocean Data Assimilation System (GODAS) has been developed at the National Centers for Environmental Prediction (NCEP). A retrospective global ocean reanalysis for 1979- present is accessible at the GODAS web site (, which provides the public an easy access to the documentations, model data, model validation and oceanic monitoring products of GODAS. The operational GODAS assimilates temperature profiles from XBT, Argo profiling floats and TAO moorings and synthetic salinity that are constructed from temperature and a local T-S climatology. The operational GODAS was updated in April 2007 with inclusion of the Altimetry sea surface height, but not the Argo salinity. This is because assimilation of the Argo salinity had large impacts on the quality of the ocean analysis, which would likely influence CFS forecast, initialized with the operational GODAS. Detailed validation of the GODAS ocean analysis against independent observations and analysis of impacts of Argo salinity will be presented. To maximize the utility of the GODAS ocean analysis for real time global oceanic monitoring, climate attributions and climate nowcasting, NOAA’s Climate Prediction Center initiated “Monthly Ocean Briefing” in May 2007. The briefing aims to provide a monthly assessment of how the state of the global ocean evolved recently, what is the interaction with atmosphere, and how recent CFS model predictions verify. The briefing consists of a PPT presentation and conference call, and is becoming a valuable product for both research and operational communities. The first part of the briefing describes the recent evolutions and current conditions of the ocean in each basin. A SST heat budget analysis is used to explain the SST tendencies for the major air-sea coupled modes such as ENSO. The influences of MJO-related winds on oceanic Kevin waves and ENSO are discussed. The impacts of extra-tropical winds on the ocean and coastal upwelling along the western coast of North America are monitored. The second part of the briefing discusses the biases in GODAS and their potential impacts on the recent performance of the CFS ENSO forecast.

Title: Summer Season Forecast Experiments with the CFS using Different Land Models and Different Initial Land States
Speaker: Ken Mitchell
Affiliation: Climate Prediction Center, NCEP, NOAA
Date: March 26 , 2008 at 2:00 p.m.

In N.H. summer, the influence of ENSO SST on N.H. atmospheric circulation is significantly weaker than in the winter season. Hence seasonal predictions by coupled global climate models show notably lower skill over the N.H. in summer than in winter, especially over land. Research over the past decade or more has indicated that proper land surface physics, land characteristics and land-state initialization (soil moisture, snowpack) is important for improving N.H. summer seasonal predictions with coupled global models.

In this study, we investigate the impact of different land models and different sources of land initial conditions on summer season predictions of the NCEP global coupled Forecast System (CFS). Specifically, 20-25 years of ensemble CFS summer forecasts are executed from late April initial conditions for four configurations of the CFS with two land models and two sources of initial land states. We present the precipitation and temperature prediction skill of these CFS summer forecasts, with a focus on prediction skill over CONUS. Additionally, we present some assessments over the Asian monsoon region (provided by CPC collaborators). The two land models in the above experiments are 1) the older OSU LSM used in the presently operational CFS and 2) the newer Noah LSM used operationally in NCEP's medium-range Global Forecast System (GFS) since June 2005. The two sources of initial land states are 1) the NCEP/DOE Global Reanalysis 2 (GR2), which utilizes the OSU LSM and 2) the new NCEP Global Land Data Assimilation System (GLDAS), which utilizes the new Noah LSM. Results from our experiments show that merely upgrading the land component of a global climate model for seasonal forecasting without providing initial land states that are selfconsistent with the land model upgrade can actually degrade the performance of the global model.

Title: Temperature Sensitivity of Pacific Snowpak
Speaker: Mike Wallace
Affiliation: University of Washington
Date: March 28 , 2008 at 10:30 a.m.
Title: Influence of Indian Ocean Dipole on Poleward Propagation of Boreal Summer Intraseasonal Oscillations
Speaker: Ajaya Mohan
Affiliation: Canadian Centre for Climate Modelling and Analysis, University of Victoria
Date: April 18 , 2008 at 3:30 p.m.

The influence of Indian Ocean Dipole (IOD) on poleward propagation of boreal summer intraseasonal oscillations (BSISO) is examined using observed datasets and coupled model outputs. The study finds that coherent (incoherent) poleward propagation of precipitation anomalies from 5S to 25N are observed during negative (positive) IOD years. Disorganized poleward propagation of BSISO in the south equatorial Indian Ocean is observed during positive IOD years. The rationale behind such an anomaly in poleward propagation of BSISO in contrasting IOD years are identified based on the theory of northward propagating BSISO, which suggests the influential role of air-sea interaction on the genesis and propagation of BSISO. We find that the mean structure of moisture convergence and meridional specific humidity distribution undergoes radical changes in contrasting IOD years, which in turn influences the meridional propagation of BSISO. This study assumes significance, considering the critical role of BSISO in modulating the seasonal mean summer monsoon rainfall.

Title: Recent developments in long-range forecasting at ECMWF: Steps towards seamless predictions
Speaker: Franco Molteni
Affiliation: European Centre for Medium-Range Forecasts
Date: April 22, 2008 at 3:00 p.m.
Title: MJO Monotoring and Assessment at the Climate Prediction Center and Initial Impressions of the CFS as an MJO Forecast Tool
Speaker: Jon Gottschalck
Affiliation: CPC / NCEP / NOAA NWS
Date: April 23 , 2008 at 2:00 p.m.

The Madden-Julian Oscillation (MJO) is the leading mode of intraseasonal climate variability across the global tropics and results in substantial areas and periods of enhanced / suppressed tropical rainfall, modulates tropical cyclone activity and monsoon systems and often impacts the extratropical circulation including over the US. CPC is committed to comprehensively monitoring, assessing and predicting the MJO in realtime operations. CPC is particularly interested in and actively pursuing methods to better understand the MJO and include its potential predictability more effectively into CPC operations -- both to improve the current forecasting capability in the week 2-4 time frame but also in the tropics through weekly hazard assessments. A description of current CPC MJO monitoring and assessment activities is given as background and includes a description of the CPC global tropics benefits/hazards assessment. Later, the use of the current version of the Climate Forecast System (CFS) in both operational and research-related MJO activities at CPC is described. Examples shown include the development of experimental realtime MJO forecast tools and its inclusion as part of an MJO objective consolidation effort at CPC. Verification statistics from these tools are shown and preliminary results indicate useful skill out to approximately 10 days on average for calculation of an MJO index. Also, a brief review is given on how the MJO activity during the winter of 2007-2008 affected CFS prediction of the current La Nina event. Finally, a few key messages are given about how COLA-CPC CFS related MJO research may be focused and applied to best and most efficiently aid CPC forecast operations .


Climate change in Sahel: past, present, future

Speaker: Alessandra Giannini
Affiliation: IRI for Climate and Society, The Earth Institute at Columbia University
Date: May 12, 2008 at 11:00 a.m.

Drought in the Sahel has long been a fascinating topic in climate research. For decades, since inception of the drying trend in this region in the late 1960's, scientists have debated its nature. Some hypothesized a bio-geophysical feedback between the anthropogenic disturbance associated with overgrazing and the extension of agricultural activity into marginal lands, driven by population growth, and the regional circulation. Others held
that the monsoon was sensitive to the imprint of the oceans on the large-scale circulation. I will review the modeling research of the past 5 years that demonstrates the dominance of the latter view: drought in the Sahel
was caused by a warming of the oceans, most noticeable in the equatorial
Indian Ocean and in the southern compared to the northern Atlantic.


Analysis of intraseasonal and interannual variability of south Asian summer monsoon using Hidden Markov Model (HMM)

Speaker: Jin Ho Yoo
Affiliation: The Abdas Salam International Centre for Theoretical Physics (ICTP)
Date: May 14, 2008 at 11:00 a.m.

The Asian summer monsoon exhibits pronounced variability on various time scales. Among them, an irregular propagating intraseasonal oscillation (ISO) with a period of 30–60 days is now considered as one of the most important phenomena to be challenged. Also, the interannual variability of seasonal mean monsoon circulation and its relationship with ENSO has been well recognized and intensively studied. While the ISO and ENSO-monsoon relationships have conventionally been considered separately, several recent studies have pointed to parallels in spatial structure, suggesting that interannual monsoon variability may be a residue of alteration of ISO phases. The relationship between the ISO and interannual variability is one of the key outstanding issues in the Asian monsoon studies.

In the present study, intraseasonal and interannual variability of summer monsoon rainfall in the pentad precipitation data is examined in a simple but flexible probabilistic model. In contrast to most previous analyses, a probabilistic model that explicitly accounts for the stochastic aspect of atmospheric variability, and can be used to generate a large number of stochastic rainfall simulations for hypothesis testing. The modeling framework is provided by a Hidden Markov Model (HMM), in which a latent state variable (hidden state) is introduced to enable a simplified factorization of the probability distribution function (PDF) of pentad rainfall.

The HMM selected consecutive phases of ISO as distinctive states and the transition probabilities among the states clearly support a cyclic transition of ISO phase. The transition probability of hidden states also suggests that re-initiation of ISO is more variable than other phases. In the stochastic simulation, the canonical ISO propagation and the level of irregularity are reasonably simulated by HMM up to 20 days time lag. The interannual variation of ISO associated with ENSO is assessed by employing a nonhomogeneous HMM (NHMM). The NHMM results showed some noticeable aspects of interannual variability of ISO. The influence of ENSO onto the ISO is reflected as preferences of particular ISO phases depending on the ENSO condition. In the presence of seasonal mean interannual variability, El-Nino related seasonal mean state is able to be distinguished from the ISO states whereas La-Nina related state is not clearly identified or shares the spatial pattern with ISO states. Statistical post-processing of dynamical seasonal prediction is also attempted by using NHMM with GCM simulation as an input variable.

Title: Fresh Flux (FWF) - Induced Oceanic Feedback in a Hybrid Coupled Model of the Tropical Pacific
Speaker: Dr. Rong-Hua Zhang
Affiliation: Earth Systems Science Interdisciplinary Center
Date: May 20, 2008 at 11:00 a.m.

Recent studies indicate that freshwater flux (FWF) forcing and its directly related changes in salinity can play an active role in maintaining the Pacific climate and its low-frequency variability. However, most previous modeling studies have focused on the roles of forcing components of atmospheric winds and heat flux; the effect of   FWF forcing and induced feedback have been examined mostly in ocean-alone modeling studies.   The impacts of FWF forcing on interannual variability in the tropical Pacific climate system are investigated using a hybrid coupled model (HCM), constructed from an oceanic general circulation model (OGCM) and a simplified atmospheric model, whose forcing fields to the ocean consist of three components. Interannual anomalies of wind stress and precipitation minus evaporation, (P-E), are calculated respectively by their statistical feedback models that are constructed from a singular value decomposition (SVD) analysis of their historical data. Heat flux is calculated using an advective atmospheric mixed layer (AML) model. The constructed HCM can well reproduce interannual variability associated with El Niño-Southern Oscillation (ENSO) in the tropical Pacific.

HCM experiments are performed with varying strength of anomalous FWF forcing. It is demonstrated that FWF can have a significant modulating impact on interannual variability. The buoyancy flux (QB) field, an important parameter determining the mixing and entrainment in the equatorial Pacific, is analyzed to illustrate the compensating role played by its two contributing parts, one is related with heat flux (QT) and the other with freshwater flux (QS), respectively. A positive feedback is identified between FWF and sea surface temperature (SST) as follows. SST anomalies, generated by El Niño, induce large anomalous FWF variability over the western and central regions, which directly influences sea surface salinity (SSS) and QB, leading to changes in the mixed layer depth (MLD), the stratification stability, the mixing and the entrainment of subsurface waters. These oceanic processes act to enhance the SST anomalies, which in turn feedback to the atmosphere in a coupled ocean-atmosphere system. As a result, taking into account the anomalous FWF forcing in the HCM leads to an enhanced interannual variability and ENSO cycles. It is further shown that the FWF forcing is playing a different role from heat flux forcing, with the former acting to drive a change in SST, while the latter being representing a passive response to the SST change. This HCM based modeling study presents clear evidence for the role of FWF forcing in modulating interannual variability in the tropical Pacific. The significance and implications of these results are further discussed for physical understanding and   model improvements of interannual variability in the tropical Pacific ocean-atmosphere system.
Title: Dynamical Polar Warming Amp;ification and a New Climate Feedback Analysis Framework
Speaker: Prof. Ming Cai
Affiliation: Department of Meteorology, Florida State University
Date: June 2, 2008 at 11:00 a.m.

Historically, only the thermodynamic processes (e.g., water vapor, cloud, surface albedo, and atmospheric lapse rate) that directly influence the top of the atmosphere (TOA) radiative energy flux balance are considered in climate feedback analysis.   One of my recent research areas is to develop a new framework for climate feedback analysis that explicitly takes into consideration not only the thermodynamic processes that the directly influence the TOA radiative energy flux balance but also the local dynamical (e.g., evaporation, surface sensible heat flux, vertical convections etc) and non-local dynamical (large-scale horizontal energy transport) processes in aiming to explain the warming asymmetry between high and low latitudes, between ocean and land, and between the surface and atmosphere.   

In this talk, I will begin with a brief review on the partial radiative perturbation (PRP) method, the primary climate feedback analysis method used in the IPCC AR4 report.   To demonstrate the need for developing a new framework, I will present a theoretical evidence showing the change in the atmospheric poleward energy transport is one of the leading factors causing the polar warming amplification.   The theoretical proof resolves the seemingly paradox, namely, "how can the warming in high latitude be greater than the low latitude warming by the atmospheric poleward heat transport given the fact the atmospheric poleward heat transport itself is driven by the poleward decreasing temperature profile?"

Next, I will propose a coupled atmosphere-surface climate feedback-response analysis method (CFRAM) as a new framework for estimating climate feedback and sensitivity in coupled general circulation models with a full physical parameterization package. The formulation of the CFRAM is based on the energy balance in an atmosphere-surface column.   In the CFRAM, the isolation of partial temperature changes due to an external forcing alone or an individual feedback is achieved by solving the linearized infrared radiation transfer model subject to individual energy flux perturbations (external or due to feedbacks).   The partial temperature changes are addable and their sum is equal to the (total) temperature change (in the linear sense).   The decomposition of feedbacks is based on the thermodynamic and dynamical processes that directly affect individual energy flux terms.    Therefore, not only the feedbacks that directly affect the TOA radiative fluxes but also those that do not directly affect the TOA radiation are explicitly included in the CFRAM. The differences between the CFRAM and PRP will be illustrated using a radiative-convective climate model.

In the end, I will present some results obtained with an idealized GCM model that does not include the hydrological cycle (therefore, cloud and ice-albedo feedbacks are not included). The CFRAM is used to isolate the partial temperature changes due to the external forcing, due to water vapor feedback, local vertical convection and non-local dynamical feedbacks. The sum of these partial temperature changes is responsible for the (total) atmospheric and surface warming patterns derived from the GCM climate perturbation simulations.   The feedback analysis using the CFRAM shows that the stronger polar warming in this idealized GCM climate simulation is solely due to the non-local dynamical feedback, as in the theoretical model.


Initial Conditions vs. Internal Dynamics in the Tropical Pacific Predictability Problem

Speaker: Dr. Christiana Stan
Affiliation: Center for Ocean-Land-Atmosphere Studies
Date: June 3, 2008 at 11:00 a.m.

The influence of atmospheric stochastic forcing and uncertainty in initial conditions on the limit of predictability of the NCEP Climate Forecast System (CFS) is quantified based on comparisons of idealized identical twin prediction experiments using two different coupling strategies. In the first method, called the interactive ensemble, a single oceanic general circulation model (GCM, Modular Ocean Model version 3 of GFDL) is coupled to the ensemble average of multiple realizations (in this case six ensemble members) of an atmospheric GCM (NCEP Global Forecast System). In the second method the standard CFS is used. The interactive ensemble is specifically designed to reduce the internal atmospheric dynamic fluctuations that are unrelated to the sea surface temperature anomalies via ensemble averaging at the air-sea interface, whereas in the standard CFS, the atmospheric noise (i.e., stochastic forcing) plays an active role in the evolution of the coupled system.

In the identical twin experiments presented here, we take the perfect model approach, thereby explicitly excluding the impact of model error on the estimate of the limit of predictability. The experimental design and the analysis separately consider how uncertainty in the ocean initial conditions (i.e., initial condition noise) versus uncertainty as the forecast evolves (i.e., noise due to internal dynamics of the atmosphere) impact estimates of the limit of predictability. Estimates of the limit of predictability are based on both deterministic measures (ensemble spread and root mean square error) and probabilistic measures (relative operating characteristics). The analysis examines both oceanic and atmospheric variables in the tropical Pacific. The overarching result is that noise in the initial condition is the primary factor limiting predictability, whereas noise as the forecast evolves is of secondary importance.


Coupled Interactions of the Monsoons

Speaker: Dr. Vasu Misra
Affiliation: Center for Ocean-Land-Atmosphere Studies
Date: June 12, 2008 at 3:00 p.m.

The South American Monsoon (SAM) will be used as a kaleidoscope to understand the global monsoons. In this talk I will briefly introduce the observed South American Monsoon (SAM) climate and its variability. The talk will then dwell on the role of airsea interactions and land-atmosphere coupling on the variability of the SAM precipitation. But these interactions are indeed not unique to SAM. A panoramic view of such coupled interactions existing in other monsoon regions of the globe will also be presented.

After demonstrating that coupled interactions are an integral part of the monsoons, the challenging issue of seasonal coupled prediction will be discussed. This will be done in the context of the ENSO predictions. ENSO is regarded to be the largest known natural coupled ocean-atmosphere phenomenon. Since ENSO has a bearing on the interannual variations of the monsoons, it is important to realize the difficulties in predicting this phenomenon. The deleterious role of the “initialization shock” in coupled model predictions of ENSO will be demonstrated.

Title: On the Mechanisms for Decadal Changes in El Nino/Southern Oscillation (ENSO) Associated with the 1976-77 Climate Shift
Speaker: Dr. Rong-Hua Zhang
Affiliation: ESSIC,University of Maryland.
Date: April 24, 2007 at 11:00 a.m.

El Niño has been observed to exhibit decadal changes in its properties; the cause and implication of such changes are strongly debated. Various mechanisms proposed to be responsible for the decadal modulation of ENSO in the late 1970s are examined using coupled atmosphere-ocean models, with a focus on the roles of decadal changes in ocean thermal structure observed in the tropical Pacific. Two types of coupled models are used, one intermediate coupled model (ICM) and another hybrid coupled model (HCM), which consist of the same intermediate ocean model (IOM) with an empirical parameterization for the temperature of subsurface water entrained into the mixed layer (Te), which is constructed via a singular value decomposition (SVD) analysis of historical data. The differences in the ICM and HCM are in the atmospheric component: the former is a statistical one estimating wind stress (_) anomalies based on a SVD analysis, and the latter is an atmospheric general circulation model (AGCM; ECHAM4.5). Signal part of wind stress response to SST anomalies is constructed by a 24 member ensemble ECHAM4.5 simulations forced by observed SST; stochastic wind stress forcing is estimated from the AGCM ensemble and coupled simulations. The ICM and HCM simulations can very well reproduce interannual variability associated with El Niño in the tropical Pacific. Sensitivity model simulations are made using the coupled models with different realizations of stochastic forcing in the atmosphere, and observed changes in ocean thermal structure in the late 1970s which are introduced into the coupled systems through the Te parameterizations from two sub-periods before (1963-79) and after (1980-96) the climate shift (Te 63-79and Te 80-96), respectively. It is demonstrated that the properties of ENSO are modulated differently by the decadal Te changes in the ocean and stochastic forcing in the atmosphere. The former is responsible for changes in the phase propagation of ENSO, while the latter can contribute to the amplitude and period modulation.

Title: Drought Monitoring based on multi model ensemble NLDAS and the GFS forecasts
Speaker: Wanru Wu
Affiliation: Climate Prediction Center/NWS/NOAA
Date: April 27, 2007 at 2:00 p.m.
Title: Automation as an Assistant to Discovery
Speaker: David Lary
Affiliation: UMBC/GEST
Date: May 11,2007 at 11:00 a.m.

By definition, many scientific issues in Earth Science are global in nature. Therefore, when we study such issues with the aid of observations and models/data assimilation we need to deal with massive datasets. As a result, there is great utility in a high degree of automation at many levels in many areas. The high degree of
automation allows us to focus our attention on the scientific issues. We will show examples of automation in model creation, observation cross-validation and calibration, data analysis and web site creation. The concept is also being used in designing prototypes of the next generation of earth observing system with real time
autonomous observation direction.

Title: Modeling Surface-Atmosphere Interactions
Speaker: Andrea Molod
Affiliation: Department of Earth, Atmospheric & Planetary Sciences - MIT
Date: May 14, 2007 at 3:00 p.m.
Abstract: The complex positive and negative feedback processes which link precipitation, evaporation, water vapor, boundary layer turbulence and large scale atmospheric motions are an integral element of the climate system. General circulation models (GCMs) are the primary tools used to elucidate these surface-atmosphere feedback mechanisms, and the ability of GCMs to properly simulate the processes involved is important to the understanding of climate and climate change. Two new modeling approaches relevant to the simulation of near-surface processes will be presented. The first is designed to capture the influence of the subgrid scale heterogeneity of the land surface vegetation on the overlying boundary layer, called Extended Mosaic. The other is called GridAlt, and captures the effects of the increased vertical resolution necessary in the regime close to the surface where the turbulent length scale is smaller than typical GCM vertical grid spacing.

Results of GCM simulations will be presented which isolate the influence of the new techniques as implemented in the MITgcm. The direct result of using Extended Mosaic was an increase in the local turbulent kinetic energy. This resulted in a change in character of a reinforcing feedback which is manifest in either a drying or a wetting regime, depending on the local surface conditions. Extended Mosaic also resulted in a strengthened the land-atmosphere coupling in the regions where this change in the feedback was manifest. The results of a series of aquaplanet simulations using GridAlt show that it captures most of the effects of increased vertical resolution. Realistic simulations with GridAlt show an increased atmospheric response to the underlying surface temperature.

Title: Simulations and prediction of the Asian-Australian and Indo-Pacific climate by NCEP Climate Forecast System
Speaker: Dr. Song Yang
Affiliation: Climate Prediction Center/NOAA National Centers for Environmental Prediction
Date: May 17, 2007 at 3:30 p.m.
Abstract: The NCEP coupled climate forecast system (CFS) is becoming an important source of information for regional climate analysis and prediction in many countries. The speaker will present a comprehensive analysis of the Asian-Australian and Indo-Pacific monsoon climate in the hindcast of the NCEP’s current operational CFS and several free runs of the coupled model, focusing on the variability and prediction of the regional climate on seasonal-to-interannual time scales. He will discuss the variability and prediction of different monsoon components and the skill of ENSO in monsoon prediction. He will also discuss the relationships between the Indian Ocean and Pacific SSTs. Features between different horizontal resolutions of the model will be compared. The general strengths and weaknesses of the CFS in simulating and predicting monsoons will be discussed as well.
Title: Selected short subjects: (1) equatorial stationary waves; (2) modes of storm track variability; (3) blocking and the NAO
Speaker: Prof. Mike Wallace
Affiliation: University of Washington
Date: May 21, 2007 at 3:30 p.m.
Abstract: Professor Mike Wallace will present a potpourri of what his students are currently working on.
Title: ENSO Oscillation and the GLobal Warming
Speaker: Dr. Kikuro Miyakoda
Affiliation: AOS, Princeton University
Date: May 25, 2007 at 11:00 a.m.
Abstract: An analysis is performed on the structure of the ENSO oscillation, using observational data, the atmospheric re-analysis of ECMWF (Simmons and Gibson, 2000; Kallberg et al. 2005) for 44 years and other re-analysis (JMA and NCEP, NASA), together with the oceanic data assimilation for 42 years (Masina et al. 2004). The conclusions below are mostly based on the results of NDJ (November-December-January) of the La Niña and El Niño years. One of the main conclusions is that, agreeing with the finding of Hansen et al (1999), the SST over the ENSO region has a sudden change in 1976 from negative to positive anomalies. Some of the reasons will be discussed below. Associated with this change, the rate of the total latent heating has intensified considerably.     The condensational heat emitted during the ENSO period may have contributed not only to sustain but also to increase the atmospheric temperature. This heat is spread from the NINO3.4 region to the global atmosphere due to the ENSO circulation. In other words, the condensational heat during the El Niño and La Niña events could be the major sources of the global warming. In particular, this process may have generated the sudden transition of the world SST in 1976. This heat flux is centered at rain belts of the equatorial Pacific and the Indian Ocean, which are located at 9 0 -15 0 S and 80 0 E-180 0 -80 0 W. In other words, its center is around the Maritime Continents and the SPCZ (South Pacific Convergence Zone), the ITCZ, and the counter-part over the Indian Ocean. The original cause for the global warming could be the increase of the greenhouse gas, aerosols etc. However, the final stage of this scenario may end up with the release of the condensational heat in the equatorial region.
Title: Tropical Cyclones in a Warmer Climate
Speaker: Lennart Bengtsson

Max Planck Institute for Meteorology, Hamburg, ESSC, University of Reading, UK

Date: October 8, 2007 at 3:00 p.p.

Tropical Cyclones (TC) under different climate conditions in the Northern Hemisphere have been investigated with the Max Planck Institute (MPI) coupled   (ECHAM5/MPI-OM) and atmosphere (ECHAM5) climate models at different resolutions. The intensity and size of TC depends crucially on resolution with higher wind speed and smaller scales at higher resolution. The typical size of a TC is reduced by a factor of 2.3 from T63 to T319. The structure of the storms is increasingly realistic at higher resolution.

The model has been tested using observed initial data from ERA-40 and operational data from 2005 and 2006. There is a realistic response to ENSO with less Atlantic TC during El Nino.

Series of 30-year experiments have been undertaken using conditions from the end of the 19 th and 20 th century and IPCC SRES scenario A1B for the end of the 21st century.

There are no significant differences between the 19 th and 20 th century but a reduction of TC at the end of the 21 st century. Reduction in the number of storms occurs in all regions. The high-resolution experiments indicate intensification at the upper end of TC, but this is not noticeable at the low resolution (T63).

We identify two competing processes effecting TC in a warmer climate. First, the increase in the static stability and reduced vertical circulation is suggested to contribute to the reduction in the number of storms. Second, the increase in temperature and water vapor provide more energy for the storms so when favorable conditions occur, higher SST and higher specific humidity will contribute to more intense storms. However, this will require higher resolution to have its full effect.

Title: CPC's Evaluation of the Stratosphere in the Operational CFS and CFS-Next
Speaker: Craig Long
Affiliation: Climate Prediction Center
Date: October 17, 2007 at 2:00 PM

It is well understood that quality short and long range weather forecasts require a valid stratosphere.  The Climate Prediction Center (CPC) has a long history of providing guidance to NCEP's Environmental Modeling Center on the quality of the stratosphere in the Global Forecast System (GFS).  This includes the quality of ozone, temperature, height and wind analyses and forecasts.  It was a natural extension of our capabilities to perform the same type of stratospheric assessment of forecasts generated from the Climate Forecast System (CFS).  CPC has since evaluated the basic stratospheric state of the Operational (T62L64) CFS forecasts and a CFS version of the current GFS (GSI-Hybrid T382L64).  We will present temperature, height, and ozone comparisons of these two models with respect to the DOE NCEP Reanalysis 2 and CPC analyses.  We will also present comparisons of the poleward heat flux and how well the structure of the wind fields are maintained with forecast time.  This includes the maintenance of the QBO.   Future evaluation plans will be discussed.

Title: Numerical research of atmospheric circulation in the North Hemisphere - dynamic downscaling experiments, energy transport and cyclone tracks
Speaker: Yong-Jia Song
Affiliation: BJERKNES Center for Climate
Date: November 13, 2007 at 11:00 AM

The Arctic climate is complex due to numerous nonlinear interactions between and within the atmosphere, cryosphere, ocean, and land. A dynamic downscaling experiment for the atmosphere in Arctic using ARPEGE climate model has been done, the systematic errors in the model are discussed in the meanwhile.   Furthermore, the poleward energy transports based on NCEP Reanalysis data and ARPEGE climate model simulation results are calculated, a long term variability of energy transport in North hemisphere based on Ncep data is showed as well. Finally, Cyclone tracks that occurred in the Northern Hemisphere during 50 extended winters has been identified from NCEP reanalyses and model simulation results by means of an objective tracking method (Hodges 1995, 1996). The tracks have been divided into two classes, one with northward moving cyclones and a second with southward moving cyclones.

Title: Super-Parametrization - A Direct Use of a Cloud-Resolving Model in Climate Simulation
Speaker: Marat Khairoutdinov
Affiliation: Stony Brook University
Date: November 15, 2007 at 11:00 AM

Recent advances in computing technology have allowed a new kind of general circulation model (GCM) to emerge, a Multi-scale Modeling Framework (MMF). It is becoming an increasingly practical tool in the area of climate modeling. In MMF, most of conventional sub-GCM-grid-scale parameterizations in each grid-column are replaced with imbedded cloud-resolving model (CRM), which in this context is often called a super-parameterization. The MMF approach allows clouds, aerosols, turbulence, and radiation processes interact on the cloud-scale, as they do in nature. One particular strength of the MMF approach is that it provides a direct link among the GCM, CRM, and cloud microphysics communities. The results of a 19-year long AMIP-style climate simulation and simple climate sensitivity experiments will be discussed. The MMF does a good job of reproducing the interannual variability in terms of spatial structure and magnitude of major atmospheric anomalies associated with the ENSO. The subseasonal variability of tropical climate associated with the Maddan-Julian Oscillation (MJO) and equatorially trapped waves are particular strengths of the simulation. Strong sensitivity of equatorially trapped disturbances such as MJO and Kelvin waves to 2K SST perturbation will be demonstrated using a simplified aqua-planet setup. Simulated cloud regimes defined by the value of 500-mb pressure vertical velocity in Tropics will be compared to observations. Preliminary analysis of simulated cloud-scale vertical velocity statistics from the MMF don't seem to show any significant land/ocean contrast in convective intensity that would explain large contrast in lightning frequency

Title: A Regional Climate Modeling Study of the Northern Plains 1997 Snowmelt Flooding Event
Speaker: Dr. Ki-Hong Min
Affiliation: Valparaiso University
Date: November 19, 2007 at 11:00 AM

Presence of snow strongly affects the surface energy budget in mid-to-high latitudes during the transition period of winter to spring. In addition, synoptic waves propagating over the Northern Plains are a major source of snow storms and flash flooding during this period. The presence of snow and its melt from winter to spring affects the propagation of synoptic waves and the amount of precipitation over this region. Therefore, it is crucial to include the cold land physics in high- and temperate-latitudes for regional climate studies. Here we investigate the effect of snow cover, soil frost, and snowmelt on the atmosphere over cold land and implement a multi-layer Soil-Snow Model (SSM) coupled to an atmospheric model - Purdue Regional Climate Model (PRCM). We have applied a one-dimensional, multi-layer land surface model based on the conservation of heat and water substance inside the soil and snow for use with the regional climate model. Compared to the current land-surface scheme, the new SSM shows significant improvement in both moisture and temperature simulation for the months of March and April 1997, which affects the surface energy budget and the hydrological cycle. Overall, the regional climate simulation of March and April 1997 with the inclusion of detailed frozen soil and snow processes improves the synoptic and local circulations during the cold season. The partitioning of incoming radiative energy into sensible and latent heat fluxes is shown to be sensitive to snowmelt and soil freeze/thaw conditions during the early stages of the model simulations. Both spatial and temporal analyses of PRCM-SSM indicate that the coupling of these processes is important when simulating cold season regional climate with frozen soil and snow cover.

Title: CFS as a Prediction System and Research Tool
Speaker: Lindsey Long
Affiliation: NOAA/NWS/NCEP/CPC
Date: November 28, 2007 at 1:30 PM
Abstract: The North American Monsoon System (NAMS) has been a challenge for both global and
regional models. One reason for this difficultly is the complex terrain of mountains and ocean. In this
assessment, we look at the ability of NCEP’s operational Climate Forecast System (CFS) to predict the
NAMS using hindcast runs from 1981-2006 at T62. In addition, model runs were made using an
updated version of the CFS at horizontal resolutions of T62, T126, and T382. These are single runs
with a May 15th initial condition. The hope is that a more accurate account of the topography will
provide better forecasts for the region. This also serves as a comparison between the operational CFS
and the updated version of the CFS. Emphasis is on the prediction of precipitation at both the
interannual and seasonal timescale and the accompanying atmospheric circulation.
In addition, the North American Monsoon Model Assessment Project 2 (NAMAP2) will be
highlighted. In this project, the CFS and GFS are compared to other global and regional models during
the 2004 monsoon season. Precipitation is the main emphasis, looking at the monsoon onset, seasonal
cycle and diurnal cycle