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Research modelsDeveloping numerical models and making them available to the scientific community is at the heart of ESSL’s research and service to the community. Leading the way are the Community Climate System Model (CCSM) and the Weather Research and Forecasting Model (WRF). CCSM is a coupled model combining representations of the atmosphere, ocean, land, and sea ice. WRF is a next-generation mesoscale numerical weather prediction system designed to serve both operational forecasting and atmospheric research needs. There is strong community participation both in developing the models and in using them. Additionally, ESSL continues to develop and use together with the community to a lesser extent a variety of other models within ESSL. This combined model development will contribute to the creation of a comprehensive Earth System Model, a top priority for ESSL and a task that will likely be undertaken in collaboration with CISL. This system will be developed around the interactions of the Earth’s physical, chemical and biogeophysical systems with future inclusion of human and societal elements. Described below are ESSL’s accomplishments and projects related to community models, research models and the creation of an Earth system model, with NCAR highlights on CCSM and the NCAR participation to the IPCC campaign, and on the CGD-MMM collaboration on Nested Regional Climate modeling which, for relatively short timescales, will allow for a direct input to societal and economical matters. WACCM - ACD/CGD
WACCM
The Whole Atmosphere Community Climate Model (WACCM) is an inter-disciplinary project of ESSL that brings together three physical components or models: the physics and dynamics of the lower atmosphere (CAM from CGD); the chemistry of the middle and upper atmosphere (MOZART from ACD); and the physical processes of the upper atmosphere (TIME/GCM from HAO). The WACCM project started with the goal of developing a fully interactive model from the ground to the lower thermosphere based on those physical components and relying on the software framework provided by the NCAR Community Climate System Model (CCSM). The scientific goal of developing WACCM is to study the couplings (chemical, dynamical, and radiative) between atmospheric layers. For example, these couplings are known to be exerted by the vertical propagation of waves that transport energy and momentum across several vertical scales, and the meridional transport of constituents by the mean circulation that communicates chemical changes globally. Those effects can be mediated by changes of the chemical composition resulting from either climate effects or solar variability. From the earlier versions of WACCM that did not include interactive chemistry (WACCM1b, circa 2002) to the fully interactive version (WACCM3, circa 2005), the project has grown from an in-house effort to a small community of users and developers both from inside NCAR and from University/Non-Profit groups. The project is also hosting a number of post-docs and students, both from the US and international affiliate Universities. Up-to-date information on the current activities are documented on the web. During 2006, WACCM has contributed significantly to the Chemistry-Climate Model evaluation (CCMval) effort, an international activity under the auspices of the Stratospheric Processes And their Role in Climate (SPARC) which operates under the World Climate Research Programme for the World Meteorological Organization. WACCM scientists are also co-authors or contributing authors in the upcoming Ozone Assessment, 2006. Under CCMval, historical simulations of the last 50 years were carried out, as well as projections of ozone recovery in the next 50 years. In addition to this, the following topics are under investigation using WACCM:
During 2007, a major emphasis is the study of the effect of the middle atmosphere on the tropospheric climate. ESSL scientists and collaborators will be looking at the potential impact that the middle atmosphere has on tropospheric climate sensitivity. This is done by comparing the climate sensitivity to a doubling of CO2 in CAM simulations with a slab ocean to WACCM simulations in identical configurations but using the fully interactive chemistry and physics. Other areas of interest that are going to extend beyond 2007 are: polar mesospheric clouds and their connection to climate change; extension of WACCM to 500 km; improvements to gravity waves parameterizations.
AIMES
ESSL is the home of the International Project Office (IPO) for the International Geosphere-Biosphere Programme’s (IGBP) Earth System modeling project, Analysis, Integration and Modeling of the Earth System (AIMES). AIMES succeeds the IGBP Global Analysis and Modelling (GAIM) Task Force that had a strong focus on independent sub-systems of the biogeochemical cycles and physical interactions between climate and ecosystems, particularly the carbon cycle. The AIMES project extends the Earth System modelling approaches in GAIM to include human processes. Modelling activities in AIMES test the sensitivity of tradeoffs in vulnerability and resilience in terms of economic and ecosystem consequences. Relevant activities in AIMES include the Coupled Carbon Cycle-Climate Model Intercomparison Project (C4MIP), where the magnitudes of terrestrial carbon uncertainties are still largely uncertain. C4MIP will investigate model benchmark and evaluation exercises to explore mechanisms that influence the response of the terrestrial carbon cycle: (1) soil moisture and net primary production, particularly in the tropics, (2) effects of CO2 fertilisation, and (3) disturbance and land cover. A joint strategy of AIMES and the WCRP Working Group on Coupled Modelling (WGCM) is to collaborate with the IPCC Working Groups to develop climate change stabilization experiments with coupled atmosphere/ocean general circulation models and Earth System models. An applied Earth System Science initiative, the International Nitrogen Initiative (INI), addresses end-to-end problem solving across scales (e.g., spatial, temporal, management) implementing process-based research through mitigation or management. In addition, AIMES sponsors the Global Emissions Inventory Activity (GEIA). AIMES is also working within the international community to develop an integrated synthesis of activities in the northern high latitudes to promote model development. To date, AIMES has initiated a Young Scientist’s Network (YSN) that met once at the Community Climate System Model (CCSM) workshop in Breckenridge, and more recently in Mexico City, alongside an Urban Regional Carbon Management Conference. Products to date include a report in EOS transactions and a paper in preparation for understanding urbanization interactions with biogeochemistry and climate for the cities of Shanghai, Phoenix, and Sao Paulo. The Integrated History of People and Earth (IHOPE) activity currently has a book from a Dahlem conference, held in 2005, in press to be released by MIT press in November, 2006 at the Earth System Science Partnership (ESSP) Open Science Conference in Beijing, China. An overall conclusion from the Dahlem-IHOPE conference is that societies respond in various manners to environmental (e.g., climate) stress. Extreme drought, for instance, has triggered both social collapse and ingenious management of water through irrigation. Sponsoring entities for workshops, symposia and colloquia include: NSF, NASA, EC-ACCENT (EU EC_FP6), IGBP, MPI (Germany), QUEST (UK).
MOZART
Using the recently finalized Version 4 of the Model for Ozone and Related chemical Tracers (MOZART-4), the impact of analyzed meteorological fields on global chemical simulations has been studied. Simulations with MOZART-4 driven with NCEP/NCAR Reanalysis and ERA-40 (ECMWF Reanalysis) meteorological fields show significant differences in the chemical budgets of a number of compounds. The diagnosis of clouds, and therefore convection and precipitation vary significantly in the 2 reanalyses, resulting in significant differences in OH concentrations and washout of aerosols and trace gases. Figure 1 compares the annual average of the aerosol optical depth from the 2 MOZART simulations compared to the observations from the MODIS instrument on the Terra satellite. The most significant differences are seen away from source regions, where the transport and washout of aerosols have a strong influence on the distributions. Constraining surface emissions of atmospheric species is crucial in constraining their budgets and is a critical first-step in understanding the impacts of emissions on global air-quality. One common methodology in constraining emissions is the use of “top-down" emission estimates from satellites. However, estimates of CO sources derived from inversions using satellite measurements still exhibit persistent discrepancies. ACD scientists carried out controlled inverse analyses to elucidate the influence of model transport on the robustness of regional estimates of CO sources. The study utilized 2 widely-used GTCMs (MOZART and GEOS-Chem) driven by 3 currently available meteorological datasets (NCEP, ECMWF and GMAO) to generate response functions for prescribed regional CO sources. Results showed that inter-model differences in CO due to differences in transport are within 10-30% of the inter-model mean CO concentration. However, these differences can translate to regionally significant spread in the source estimates. For example, while CO source estimates for East Asia and North Africa were reasonably robust, the results showed inconsistencies and inter-model spread of greater than 40% in source estimates for Indonesia, South America, Europe and Russia. This clearly indicates that the current estimation of top-down emission uncertainty fails to account for transport bias. FY2007 work will include continued evaluation of MOZART-4 through comparisons with satellite and in situ measurements as well as additional testing of the impact of analyzed meteorological fields on chemical simulations. This work is funded by NSF/NCAR, NSF/Biocomplexity, NSF/ITR, and NASA. CAM CHEM
The incorporation of interactive chemistry in the Community Atmosphere Model (CAM) has seen considerable progress during the last year. CAM is the latest in a series of global atmosphere models developed at NCAR for the weather and climate research communities. CAM also serves as the atmospheric component of the Community Climate System Model (CCSM). Many of the processes included in the chemistry-transport model MOZART have now been transferred to CAM. These include interactive photolysis rates, interactive dry deposition and interactive biogenic emissions. For extended chemistry-climate studies, a number of different options exist for simulating aerosols and chemistry to facilitate using the model in the optimal configuration. Aerosols can either be prescribed, simulated using simple input oxidant fields, or simulated using the full MOZART-4 aerosol parameterization. ACD scientists have developed a mechanism in which the number of hydrocarbons is quite reduced from the MOZART-4 mechanism, leading to a speed-up of a factor of 2. This reduction has been analyzed and evaluated against measurements and it reproduces many of the main features of atmospheric chemistry relevant for climate studies, e.g. the ozone distribution and the methane lifetime. The indirect effect has been incorporated through collaboration with CGD scientists. FY2007 plans include continued evaluation of the model performance under the different options described above. This work is funded by NSF/NCAR, NSF Biocomplexity, and DOE.
TUV
Tropospheric ultraviolet (UV) radiation is the driving force for all tropospheric photochemical processes. Photons in the UV wavelength have the potential to break usually fairly stable molecules into very reactive fragments (photolysis) and thus initiate reaction chains otherwise unlikely or even impossible. UV radiation is also harmful to living organisms and detrimental to human health. High doses of UV radiation are considered the major contributing factor for the development of skin cancer or cataracts. UV radiation can weaken the human immune system and can affect crop yields and phytoplankton activity (to only name a few effects). The TUV model calculates spectral irradiances and actinic fluxes, biologically active UV radiation at the surface, and photolysis coefficients (J values) for atmospheric chemistry use. The TUV model was made available to the community through the NCAR/SCD Community Data Portal. Although it may be premature to give robust statistics, TUV downloads from (non-NCAR) community users continue at a rate of about 2-4 per week. ACD scientists, in collaboration with U. of Cordoba (Argentina) researchers Rafael Fernández , Gerardo Palancar, and Beatriz Toselli, added to TUV a fully explicit line-by-line calculation of the O2 Schumann-Runge bands (SRB) transmission. This explicit calculation allows testing of parameterization methods currently used in models, and also allows more accurate calculation of scattered radiation in the stratosphere and mesosphere. ACD scientists, together with medical researchers J. Cannell (Atascadero State Hospital), R. Wieth (Mount Sinai Hospital, Toronto), J. Umhau (NIH), M Holick (Boston U.) W. Grant (SUNARC), C. Garland (U. California San Diego) and E. Giovannucci (Harvard U.), examined the causes for the seasonal dependence of influenza epidemics. Based on a critical review of the literature, they hypothesize that the low wintertime UV levels at temperate latitudes lead to common vitamin D deficiency, which in turn may be associated with higher risks of influenza epidemics. FY 2007 work will involve continued use of TUV and testing of parameterizations used in other models. This work is funded by NSF/NCAR. Master mechanism
The NCAR Master Mechanism is an explicit and detailed gas phase chemical mechanism combined with a box model solver. User inputs include species of interest, emissions, temperature, dilution, and boundary layer height. Any input parameter may be constrained with respect to time. Photolysis rates are calculated using the TUV model included in the code package. The model is written in a mixture of F77 and Fortran90, and is managed using C-shell scripts. ACD scientists continued the development of the Self-Generating Master
Mechanism, the only fully explicit mechanisms for the gas-phase atmospheric
oxidation of hydrocarbons. An important recent addition is a set
of subroutines to formulate the The model can be downloaded from the NCAR Community Data Portal. This work is funded by NSF/NCAR.
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