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2007 Seminars at COLA
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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