Several new global climate change experiments have been conducted with
a coupled climate model that includes the effects of increasing
CO2 and the radiative cooling effects of sulfate aerosols.
The greenhouse gas increase causes general global warming, however,
the sulfate aerosols cause less warming and even regional cooling,
which yields climate change patterns closer to observed.
Several different climate change scenarios were
performed. Full details are on this page.
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Thomas Bettge, Bruce Briegleb, William Large, Warren Washington and John Weatherly have completed the development of the CSM sea ice model (CSIM). The model has been implemented in the fully coupled CSM integrations. The present model is based on the cavitating-fluid ice dynamics, and the 3-level ice and snow thermodynamics modified for interface to the Flux Coupler. In early CSM integrations, the ice dynamics allowed excessive build-up of thick ice in response to wind forcing. The excessive ice build-up has been corrected in the model, while an improved treatment of ice dynamics is under development.
The results of the coupled CSM integrations showed very little trend in the total ice extent in each hemisphere, a remarkable achievement for a non-flux-corrected atmosphere-ocean model. In particular, the Southern Hemisphere ice extent and mean ice thickness are very close to the present-day observations.
The sea ice model continues to be developed, through collaboration with Jinlun Zhang and Mike Steele of the University of Washington and Greg Flato of the Canadian Climate Center, to incorporate the viscous-plastic ice rheology of Hibler-Zhang. Sensitivities of the ice thermodynamics are being investigated by Weatherly and Jim Maslanik of University of Colorado/CIRES.
Gerald Meehl and Filippo Giorgi continue to serve as a lead authors of Chapter 6 of the 1995 IPCC Scientific Assessment that will summarize recent findings of transient climate change due to increased carbon dioxide (CO2) and trace gases. Meehl summarized the effects of possible changes in climate variability as a result of increased CO2. Our research at NCAR with a coupled model revealed patterns of climate change with increased CO2 and sulfate aerosols whose effects were consistent with other modeling centers involved in the 1995 IPCC. Giorgi analyzed the projections of regional climate change by coupled GCM transient runs as well as nested regional climate model experiments. He found that, because of the relatively large errors in the present-day runs and the wide range of simulated regional responses by GCMs, the confidence in the climate change scenarios produced by current coupled GCMs on the regional scale is still low. He also found that nested regional climate models can enhance the simulation of regional climate change detail as forced by complex topography and land cover. Linda Mearns was also a contributor to Chapter 6 and summarized analyses of changing climatic variability in climate models and the frequency of extreme events.
Bette Otto-Bliesner is a contributor to Chapter 5, Climate Models-Evaluation of the 1995 IPCC Scientific Assessment. Otto-Bliesner summarized the performance of models in simulating the Earth's climate for past geologic time periods.
Robert Chervin and Anthony Craig used the 512 PE Cray T3D at the Pittsburgh Supercomputing Center to investigate the issue of scalability of the Parallel Ocean Program (POP) with respect to both number of processors and model resolution. Several performance bottlenecks were identified and corrected, which allowed performing integrations with a 2/3 degree (on average), displaced pole, global version of POP instead of only the 4/3 degree (on average) version. The standard 2/3 degree grid (384x256x32) was modified (i.e., to 384x288x32) to include increased latitudinal resolution near the equator to resolve the strong tropical current systems. Also, because of the displaced pole, there is high horizontal resolution in the eastern North Pacific, in the Arctic Straits near northern Canada and Greenland, and the Gulf Stream area. This modified version allowed for a very realistic representation of the continents and bottom topography to obtain correct volume transport flow in many important regions of the global ocean. A highly scale selective biharmonic (i.e., del fourth) spatially varying horizontal viscosity and diffusivity was implemented as an alternative to the more traditional Laplacian (i.e., del squared) formulation which permitted a doubling of the time step. This version of POP has been integrated for approximately 25 years and the results are quite promising. Further experimentation with this 2/3 degree version of POP is ongoing with expectation of its eventual inclusion in a new CHAMMP-based coupled model. The uncoupled performance of this component model is being evaluated, improved and optimized.
Craig and Matthew Maltrud (LANL) have taken responsibility for collecting and organizing the various versions of POP that have evolved over the past several years. A consolidated version of the model, featuring all the latest and tested developments, should result from their efforts.
Chervin and Craig are also carefully evaluating the interpolation schemes being developed by Phillip Jones at LANL. These schemes are critical for communication of component model information through the flux coupler and also for the analysis of the performance of all versions of POP that feature generalized curvilinear coordinates and a displaced pole.
Chervin and Craig have become active participants in the distributed, multi-institutional CHAMMP coupled climate model activity, both technically and scientifically.
Benjamin Felzer, Jon Bergengren, David Pollard and Starley Thompson collaborated on GENESIS version 2.0 simulations of the climate of 6,000 and 10,000 years ago using a fully interactive version of the EVE predictive vegetation model running synchronously with the climate model. Some large-scale features of the predicted vegetation match vegetation changes estimated from paleo records, but some vegetation model shortcomings were also apparent.
A new dynamic vegetation model has been coupled into the GENESIS GCM, in collaboration with Jon Foley's group at the University of Wisconsin, Madison. Foley et al. have recently developed a new "IBIS" vegetation model using an integrated approach to photosynthesis, respiration, transpiration and NPP. The net carbon flux into or out of the plant determines the rate of growth of each plant type, which allows the dynamic evolution of geographic vegetation distributions to be predicted in response to climate change simulated by the GCM, while simultaneously the changing vegetation cover has significant effects on the large-scale climate. The model is described in a paper in press in Global Biogeochemical Cycles, along with preliminary dynamic-vegetation results using the land-surface part of GENESIS (LSX) driven by prescribed meteorology.
The regional climate model (RegCM) developed in CCR by Giorgi and collaborators was used for a number of applications.
Giorgi, Christine Shields and Mearns completed five-year long present day and 2xCO2 experiments over the Central Plains region with boundary conditions provided by the CSIRO GCM. The results are presently being analyzed, and show that the RegCM demonstrates good performance in reproducing spatial and temporal patterns of temperature and precipitation over the Central Plains. These runs will provide climate change scenarios for use in a variety of impact assessment studies. In collaboration with Maria Rosaria Marinucci, similar control and 2xCO2 runs are being conducted over the southwestern U.S. region, which will also be used in impact sensitivity studies.
Giorgi, Jim Hurrell and Marinucci completed a study of elevation dependency of the climate change signal and it's possible implications for climate change detection. A significant elevation dependency of the surface warming signal was found in regional climate model runs over the Alpine region, which was mostly attributed to a snow-albedo feedback. This study was based on five-year long present day and 2xCO2 experiments over the European region with boundary conditions provided by the Washington-Meehl version of the CCM. The results suggest that impacts of global warming on high elevation ecosystems and hydrology may be pronounced and that the elevation signal in surface climate change could be used as a useful detection tool.
In collaboration with Gary Bates, Mearns and Steven Hostetler (USGS), Giorgi completed five-year long present day and 2xCO2 experiments over the Great Lakes Basin with boundary conditions provided by the CSIRO GCM. For this experiment the model was interactively coupled with a lake model. Results are currently being analyzed, and the focus of the analysis is on the effects of lake-atmosphere interactions and feedbacks on the simulated regional climate change signal.
Other applications of the RegCM include: i) the study of the effects of variations in the size of the Aral Sea on the climate of the region (this work is in collaboration with Lisa Sloan and Eric Small of the University of California, Santa Cruz); and ii) the study of monsoon-vegetation interactions over East Asia (this work is in collaboration with Congbin Fu of the Chinese Academy of Sciences). Both these projects are at their beginning stages. Related to project ii) above, Giorgi is involved in the scientific committee of the START TEA (Temperature East Asia) region.
Giorgi, Shields and Keiichi Nishizawa (CRIEPI) are incorporating and testing new physics parameterizations from the CCM3 (radiative transfer, convection and land surface processes) within the RegCM. This work will improve the compatibility between the RegCM and the CCM3 (i.e. the atmospheric component of the CSM), and will constitute the basis for the development of the next version of the regional climate model. As part of a collaboration with William Chameides of the Georgia Institute of Technology, the RegCM is currently being coupled with an atmospheric chemistry/aerosol model to study the effects of sulphate emissions on the regional climate of East Asia. This work is in its beginning stages.
Giorgi also completed the development and testing of a parameterization of surface heterogeneity for inclusion in land surface process models. A stand-alone version of the scheme has been completed and extensively tested using observed climate forcing. The model reproduced the surface energy and water budgets at various locations. Giorgi analyzed the effect of heterogeneity in surface temperature and soil water content on the surface budgets. Temperature heterogeneity was found to be most important for the simulation of snowpack evolution and related surface-atmosphere fluxes, while soil water heterogeneity substantially affected the soil water cycle.
With Giorgi and Mearns, Bates continued work on the simulation of the regional climate of the Great Lakes and Mississippi basins, under the NOAA Climate and Global Change Program's GCIP project. Several simulations of the 1988 drought and 1993 floods over this region were conducted to study the effects of soil moisture and vegetation on regional hydrology. Among key results found were that changes in local land surface effects like soil moisture have only modest and fairly short-lived influences on precipitation in these regional climate simulations.
Bates, Hostetler and Melanie Wetzel (Desert Research Institute) continued the study of the regional climate model's simulation of surface hydrology over the western United States. Precipitation and snow water equivalents (SWE) were compared with observations at different spatial scales and geographic locations, and as a function of elevation. Precipitation and SWE were generally well simulated but were under-predicted at local topographic maxima. These results have implications in the use of sigma coordinate models to simulate surface hydrology in regions of highly variable topography.
Bates also continued collaboration with Sue Marshall (University of North Carolina - Charlotte) to implement her parameterization of snow albedo in the BATS surface physics package of RegCM2.
Thompson, Pollard and Shields continued regional climate
model simulations for the DOE Yucca Mountain Project. During 1996,
an analysis of potential climate change at the Yucca Mountain Site
for an assumed CO2 doubling climate scenario was performed. In
addition to being warmer, as expected, it was found that winter
rainfall increased substantially in the increased CO
In collaboration with Anji Seth, Giorgi is analyzing the effect of
initial conditions, lateral boundary conditions, resolution
and domain size on the simulation of regional climate using limited area
models. The summers of 1988 and 1993 are used
as test cases for this study. The study shows that the choice of domain size,
and resolution significantly affect the
simulation of precipitation for the selected cases, as well as it's sensitivity
to changes in surface forcings. This indicates that, for different regions,
care has to be taken in the selection of an appropriate
domain of simulation.
Linda Mearns, with Tim Hoar of CAS,
constructed a statistics
package that performs a suite of statistical tests on daily temperature
and precipitation time series, across a model or observational
spatial domain.
This work is partially supported by the Statistics and
Atmospheric Sciences Program at NCAR.
This past year the package has been applied to Regional Climate Modeling
runs of the U. S. Great Plains and Great Lakes regions.
Mearns with colleagues Cynthia Rosenzweig and Richard Goldberg at GISS
continued their studies to include
sensitivity of the crop
model to combinations of mean and variance changes of both
temperature and precipitation.
The work was further extended to forming scenarios of climate change
one with only mean changes, and another with mean and variability changes,
as predicted from runs of the regional climate model (RegCm) nested
in the GENESIS GCM over the conterminous U.S. These scenarios were then
applied to the CERES-wheat model for four locations in the U.S.
central Plains. Substantial differences in simulated yield resulted between
the mean and mean plus variability scenarios at three of the four locations.
As an extension of this work, a project studying impact of variability changes
on forest/ecosystems
in the Northwestern U.S. has begun, funded by NSF and in collaboration with
scientists at the University of Washington and Oregon State University.
The NIGEC project "Development of a Nested Regional Climate Change
Scenario with an Application to Crop Climate Models" completed
its third year and started its fourth.
The project involves regional modeling with RegCM2 by Giorgi, and Shields
and detailed model evaluation and application to crop models by
Mearns and Easterling at the University of Nebraska.
One goal of the project is to appropriately integrate climate modeling
work, model analysis, climate change scenario formation, and application to
impacts models.
The project is providing climate change scenarios for other
researchers funded by NIGEC.
On the impacts side, the sensitivity of the crop models to the
individual climate
variables is being determined by Mearns and colleagues.
In addition, a study of the spatial scaling characteristics of simulated
crop yields in the Great Plains has begun.
This past year the nesting GCM
was selected (the 9-level CSIRO climate model), and 5-year control and
doubled CO2 runs of the RegCM were completed.
Basic analysis of the runs has been completed, and the control
run is being used to exercise the crop models.
A comparison of the regional climate model results with a semi-empirical
statistical downscaling technique (developed by colleagues at
the University of Nebraska) for the Central Great Plains is nearing
completion. As part of this project an analysis of contrasting
climate conditions for 1988 and 1993 in the Great Plains was completed by
Giorgi, Mearns, Leslie Mayer, and Shields.
Several new integrating projects were developed and proposed
in the winter and spring,
and have been funded by EPA, NASA, and NOAA.
These are: (1) Two overlapping three-year projects on Climate Variability and
Agriculture in the Southeast U. S.;
(2) another three-year project funded by NASA
concerning the Yangzte River Delta
MegaloPlex, under the direction of Chameides at Georgia Institute of
Technology; and (3) a small project funded by
NOAA concerning the effects of climate
variability on forest dieback in the Northeast U. S. which
began this past summer.
Mearns is using the regional climate model runs of the Great Lakes
region completed last year to perform a regionally integrated impacts
assessment, which involves
American and Canadian foresters, agronomists and hydrologists.
Detailed validation of daily output has begun.
Meehl, Washington, Bettge, and Gary Strand
configured a global coupled ocean-atmosphere general circulation
model without flux correction and integrated it into a set of 75-year
sensitivity experiments where increasing CO2 concentrations and the
direct and indirect efforts of anthropogenic sulfate aerosols were
included. Sulfate aerosol forcing increases from zero to present-day
estimates in the first 30 years of the integrations, while equivalent
CO2 forcing increased by 1% per year relative to the control
experiment, similar to the rate of the increase of observed greenhouse
gas forcing over the period 1960-1990. Annual mean averages around
year 30, analogous to present-day conditions, indicate better
agreement with recent observed geographic and zonal mean temperature
anomaly patterns in the sulfate aerosol experiments and less warming
in northern summer than winter. Sulfate aerosols then are increased
following the IS92a scenario, while CO2 continues to increase at 1%
per year. Averages around year 70, analogous to conditions roughly 40
years in the future, indicate warming almost everywhere in the
troposphere over the globe as the CO2
forcing overwhelms the negative
radiative forcing from the sulfate aerosols. There is also a
weakening of the south Asian monsoon in the sulfate aerosol
experiments. With the help of Bruce Briegleb (CMS), there is
qualitative agreement in the patterns of the temperature changes, both
geographic and zonal, between the different sulfate aerosol
experiments, with the magnitude of the changes a function of the size
of the radiation forcing. The indirect experiments were conducted in
cooperation with David Erickson (ACD), and the statistical significance
of the coupled model change was done with the help of Peter Jaumann
(ASP). This work will be published in Geophysical Research
Letters and click here to see the figure (75k).
Thompson and Pollard completed work on GENESIS version 2.0 simulations
designed to examine how the mass balance of the Greenland and
Antarctic ice sheets could respond to global warming. 1x and 2x
equilibrium CO2 cases were run with the global climate model, taking
care to apply reasonable correction procedures that greatly improve
the model's surface mass balance in the control case. It was found
that increased ablation due to warming in the 2xCO2 case dominates in
Greenland, but increased accumulation dominates in Antarctica. The
implied net effect of the mass balance changes on the time rate of
change of sea level is relatively small. This work is in press in
the Journal of Climate.
Over this last year, Otto-Bliesner tested the CCM3 atmospheric
component of the NCAR CSM at T31 (approximately 3.75 latitude by
3.75 longitude) resolution. The T31 model is able to replicate the
basic surface features such as sea level pressure, surface stresses, and
precipitation comparable to the standard T42 simulation. Notable differences
include less ridging of the subtropical high in the North Atlantic
in January in the T31 model resulting in a southward shift of maximum
wind stresses and a 3 W/m2 radiative imbalance at the top of the
atmosphere. The latter will be eliminated with future adjustments.
The T31 version of CCM3 will be useful for paleoclimatic applications
because of its reduced computing requirements. A slab ocean
with diffusive heat transport is also being developed for similar
applications and has completed initial testing.
Otto-Bliesner continued collaboration with Garland Upchurch
(Southwest Texas State University) examining the role of high-latitude
forests in achieving warm, ice-free conditions year-round during a
"Greenhouse interval" of climate history (Cretaceous-Tertiary
boundary at approximately 66.4 million years ago). The effect is
equal to a doubling of carbon dioxide.
Otto-Bliesner and Brady used the ocean GCM developed by Brady
to investigate the Atlantic thermohaline circulation during the Last
Glacial Maximum (21 Kyr), a time when stable isotope measurements in
deep-sea cores have been interpreted to indicate shallow North
Atlantic Deep Water and greater penetration of Antarctic Bottom Water
into the North Atlantic. Driven by CLIMAP estimates of glacial
sea-surface temperatures, the model shows the best fit with the
data when sea-surface salinities are reduced by 1 part per thousand
in the North Atlantic poleward of 50 N.
A high-resolution dynamic ice-sheet model has been coupled to the
GENESIS Global Climate Model (GCM). The relatively coarse resolution
and distorted topography in GCMs poses significant problems in
predicting the mass balance on ice sheets, and during FY96
Pollard and Thompson have applied techniques to substantially
solve the downscaling problem. In addition, important
ice-sheet-specific physics such as the refreezing of meltwater that is
absent in the GCM snow and ice modules has been incorporated. With
these techniques, realistic mass balances on present-day Greenland and
Antarctica have been achieved. The coupling techniques are independent
of the GCM, and the dynamic ice-sheet model can be used with any
GCM. The ice-sheet model itself uses a standard vertically integrated
flow law to predict ice thickness versus longitude and latitude, with
the bedrock topography responding towards local isostatic equilibrium
under the ice weight with a time lag of 3000 years.
The coupled GCM-icesheet model system has been applied so far to two
geologic periods: the end of the last interglacial, and the last
glacial maximum. Just before the end of the last interglacial at about
120,000 yr BP, conditions resembled those of
today. In the next 10,000 years, geologic evidence shows that ice
sheets started growing rapidly in N.E. Canada and Eurasia, leading to
a sea-level drop of about 50 m during that time. The GENESIS GCM has
been run for several decades to simulate the climate of 116,000 yr BP
with no North American or Eurasian ice sheets, and then the dynamic
ice-sheet model has been driven by that climate for 10000 years. A
large ice sheet grows (unrealistically) in the western Rockies, but
only minor growth occurs in N.E. Canada. The cause of this discrepancy
is under investigation. A large ice sheet grows on Scandinavia, in
better correspondence with geologic data.
For the Last Glacial Maximum (LGM) at 21,000 BP, the GCM has been run
with prescribed "observed" N. American and Eurasian ice sheets, and
then the dynamic ice model has been run to equilibrium under that
climate. In the nominal experiment, the N. American ice sheet retreats
rapidly, whereas one would expect it to be close to equilibrium at
21,000 BP. However by imposing slight perturbations to the GCM
climate, the ice model reaches equilibrium albeit with a different
shape than the prescribed initial shape. These results suggest (i) the
simulated GCM climate is close to correct but is slightly too warm at
LGM, and (ii) the temporal dynamic evolution of the ice sheets from
about 25,000 yr BP onward needs to be considered to explain the
ice-sheet shape at LGM. These experiments are the subject of 3 papers
in press in glaciological journals.
During FY96, Robert DeConto, Pollard and Thompson completed a simulation of
the Campanian period (80 million years BP) with the GENESIS GCM using
a 50-m slab ocean model. Boundary conditions for this period have
been assembled by DeConto and Chris Wold at NCAR, with input
from William Hay at the University of Colorado.
New global maps of continents and
topography were assembled by this group for the simulation, who also
provided prescribed values for atmospheric composition, solar
constant, etc. The EVE vegetation model was used in fully interactive
mode, modified to account for the absence of grasses (which evolved
later in geologic time). To our knowledge this marks the first time
such a coupled system has been used for Mesozoic GCM simulations. The
simulated surface temperatures and predicted vegetation show very
encouraging agreement with proxy fossil evidence, including warm polar
climates and forests covering most of the south polar land-mass.
Esther Brady has taken the surface meteorology from this run, and
driven a Semtner-Chervin type ocean general circulation model at
2x2-degree resolution to quasi-equilibrium, using bathymetry estimated
for the Campanian by DeConto et al. The bottom water formation in
these experiments suggests a situation very different from today,
originating as fairly warm but saline water emerging from shallow seas
in the southern mid latitudes, and moving poleward before sinking to
form bottom water at a temperature of about 10 degrees C (compared to
today's ~3 degree C). These Campanian GCM results are novel and are the
subject of 2 papers to be submitted to Science and Nature.
These models make use of configurations from CHAMMP researchers
and use new massively parallel processor (MPP) computers. The
coupled climate model will conduct multi-century climate change
experiments.
Through collaboration from Los Alamos National Laboratory (LANL), the
Naval Postgraduate School (NPS), and NCAR, we have developed an ocean
component that uses the Parallel Ocean Program (POP) ocean model with
a displaced north pole. The grid has an average resolution of 2/3
degree latitude and longitude with increased latitudinal resolution
near the equator of approximately 1/2 degree. Because of the
displaced pole, there is relatively higher horizontal resolution in
the eastern North Pacific, in the Arctic Straits near northern Canada
and Greenland, and in the Gulf Stream area. Also, the
continents and bottom topography were carefully modified to obtain
realistic flow in many regions throughout the globe. This model is
being spun up with observed surface and subsurface forcing in
preparation for coupling. The model is presently running efficiently
on the CRAY T3D and is being run on the CRAY T3E. We also plan to add
more realistic upper ocean parameterizations to the model. The model
in its present form yields an extraordinary simulation of the Arctic
Ocean, tropical Pacific, and boundary currents, such as the Gulf
Stream, with eddies resolved in most basins.
The ice model has been implemented in an eddy-resolving model
by Yuxia Zhang of the Naval Postgraduate School
and optimized for MPP architecture by
Craig. It uses the Zhang and Hibler ice dynamics with line
relaxation for solving the viscous-plastic ice rheology. The
thermodynamics are from the Semtner and Parkinson-Washington models.
The grid is transformed such that the resolution is constant, thus
avoiding the problem of convergence near the pole as on a
latitude-longitude grid. This grid will require an additional
interpolation of atmosphere and ocean variables. The spatial
resolution of Zhang's model is about 18 km, which provides a realistic
Arctic simulation of eddy-resolving ocean and sea ice motion.
Recently, she has also applied this model in the Antarctic region,
again with realistic eddies simulated. For the coupled model, an ice
model grid with 27 km resolution has been implemented that includes all
of the present day ice-covered areas in both hemispheres,
minimizing the grid space required. John Weatherly and
Zhang are improving the thermodynamical aspects of the sea ice
model by adding more realistic treatment of snow and sea ice.
The new sea ice model of Elizabeth Hunke and John Dukowicz of LANL
could also be implemented in the coupled system in the future. It
is designed to be another efficient dynamical sea ice model and can be
run on the POP ocean grid with the displaced pole.
The atmospheric component is the massively parallel version of the
NCAR Community Climate Model version 3 (CCM3). This model includes the
latest versions of radiation, boundary physics, and precipitation
physics and is a state-of-the-art atmospheric component. This model
has been coded to run on the T3D and is being converted to the T3E.
The method of tying the components together and allowing the exchange
of fluxes and variables is the flux coupler. The flux coupler is
undergoing testing and implementation by Richard Loft, John Dennis,
and Steven Hammond (SCD). Since the grid components are different,
there is an interpolation scheme for passing information between the
atmospheric component grid and the ocean/sea ice grid that has been
developed by Philip Jones of LANL. It is undergoing testing and
refinement.
We have coupled the ocean and sea ice models, which have already run
on the Cray T3E, and spun up the ocean/ice system. Based on the
experience with the NCAR CSM, in order to minimize the initial drift
of the coupled system, the ocean/ice can be spun-up with forcing from
previous CCM3 runs with prescribed sea surface temperature. This has
also been useful in demonstrating and improving the kind of
adjustments that initially occur in the ocean and ice due to coupling
the CCM3, without having to run the more expensive coupled system.
This massively parallel coupled climate model takes advantage of the
latest high performance computer technology. This distributed
scientific effort requires many scientists and programmers
contributing to goals of a new generation DOE climate model. The model is
flexible enough to allow changes for new components. This effort will
be complementary to the NCAR Climate System Model (CSM) effort in that the
flux coupler concept will be used, the same spin-up technique will be
used, and the CCM3 will be used.
The following are the scientists/programmers involved in the coupled
climate model effort in alphabetical order: J. Arblaster (NCAR), T. Bettge
(NCAR), R. Chervin (NCAR), T. Craig (NCAR), J. Dennis (NCAR), J.
Dukowicz (LANL), J. Hack (NCAR), S. Hammond (NCAR), E. Hunke (LANL),
P. Jones (LANL), R. Loft (NCAR), R. Malone (LANL), M. Maltrud (LANL),
W. Maslowski (NPS), J. Meehl (NCAR), A. Semtner (NPS), R. Smith
(LANL), G. Strand (NCAR), W. Washington (NCAR), J. Weatherly (NCAR),
D. Williamson (NCAR), and Y. Zhang (NPS).
Updated information on the DOE/CHAMMP modeling effort can be found
here.
Climate Model Analysis and Impacts Assessment of Climate Variability
Arctic Sea Ice Modeling
A model of the Arctic ice-ocean system developed by Weatherly
has been used to simulate the Arctic response to the
greenhouse warming predicted in the Washington and Meehl coupled GCM.
The sea ice responds to the doubled-CO2 warming by becoming
significantly thinner, with a lesser change in ice extent. The results
illustrate the difficulty in detecting greenhouse-induced climatic
change from satellite observations of ice extent alone. The Arctic
ice-ocean model is also being used to investigate the extreme
minimum ice extents observed in 1990 and 1995.
Detection of Climate Change--Climate Sensitivity to Increased
Greenhouse Gases and Sulfate Albedo (Direct and Indirect Effects)
Paleoclimate Model Development and Applications
Coupled GCM and Dynamic Ice-Sheet Model
A/OGCM Simulations of the Campanian (80 Ma)
Participation in PALE and PMIP Projects
Felzer, Pollard, Thompson and Otto-Bliesner
have participated actively in the international PMIP
(Paleoclimate Modeling Intercomparison Project) and PALE
(Paleoclimates from Arctic Lakes and Estuaries) Projects. In
collaboration with John Kutzbach's group at the University of
Wisconsin, Madison, GENESIS GCM simulations have been performed at the
prescribed 6,000 BP and 21,000 BP periods and archived for PMIP, and
David Pollard is an organizer of the ice-sheet mass balance subgroup
for that project. Ben Felzer is serving as the main climate modeling
liaison for PALE, and has analyzed experiments using GENESIS for 6,000,
10,000 and 21000 BP, paying close attention to the vegetation
distributions predicted by the EVE vegetation model developed
by Jon Bergengren. In addition Felzer is performing a 6000 BP
simulation using the ARCSyM regional climate model over a domain
including Hudson Bay, Greenland, Iceland, part of the Canadian
Archipelago and the northwest Atlantic Ocean.
Two-meter temperature anomaly, 10-0 ka BP (June, July, August).
Increased summer insolation at
10 ka BP results in a warmer
northern hemisphere except for regions under the influence of
the ice sheets [GENESIS simulations].
Biomes at 0 and 10 ka BP simulated by GENESIS
coupled with EVE. The warmer temperatures across Asia at 10ka BP
produce grassland instead of forest in the modern simulation.
North Atlantic region simulated with the mesoscale
model,
ARCSyM. Simulations will
include forcings at the boundaries by modern observational,
modern GENESIS, and 6 ka BP GENESIS.
The model resolution is 70 km.
NCAR Contribution to New Generation DOE/CHAMMP Distributed Climate
Modeling
Ocean Model Component
Sea Ice Model Component
Atmospheric Model Component
Flux Coupler
Coupled Models
