ESSL LAR 2008: Strategic Goal #1, Priority #4
Earth and Sun Systems Laboratory endeavors are central to NCAR's Strategic Goal #1, Improve understanding of the atmosphere, the Earth system, and the Sun. This Strategic Goal encompasses four Strategic Priorities, each of which is dependent on the efforts and accomplishments of ESSL staff.
ESSL developed an action plan with seven priority themes which involve direct partnerships with the university community and contribute directly to the ESSL Strategic Vision and to several priority items of the NCAR Strategic Plan.
ESSL's seven priority themes:
- Climate projection, with emphasis on short-term prediction.
- Biosphere-Atmosphere-Hydrosphere interactions and specifically development of BEACHON Project (Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, Hydrology, Organics and Nitrogen).
- Water system research, specifically the development of the Society, Water, Atmosphere and Natural Systems Project (SWANS).
- An advanced Weather Research and Forecasting system, specifically the development of the Hurricane Intensity and Forecasts (HiFi) Project.
- Space Weather, specifically the development of the Coronal Solar Magnetism Observatory Project (COSMO).
- Chemical Weather, including interpretation of observed data gathered during the Megacity Impact on Regional and Global Environments (MIRAGE) campaign, and the development of a capability for chemical data monitoring and prediction.
- Prediction across scales, specifically the development of an advanced next-generation, climate-weather modeling system and an integrated Earth system model of intermediate complexity.
Goal #1, Priority #4: Developing Community Models, is described in the NCAR Strategic Plan as follows: "Developing numerical models and making them available to the scientific community is at the heart of NCAR's research and service to the community. Key activities in this priority are creating and adding to community models, research models, as well as progressing toward creation of an Earth system model."
This NCAR priority, driven by ESSL's themes 1, 4, 5, 6 & 7, is critical to achieving NCAR's first strategic goal.
The section below describes specific research conducted by ESSL staff under projects relevant to Priority 4. The major ESSL activities in this area are ongoing improvement and development efforts focused on the following numerical models: the Community Climate Systems Model (CCSM), the Weather Research and Forecasting model (WRF), Space Weather prediction models, the Nested Regional Climate Model (NRCM), and the Whole Atmosphere Community Climate Model (WACCM). Additional models included in these efforts are the Model for Ozone and Related chemical Tracers (MOZART), the Community Atmosphere Model with chemistry (CAM-Chem), upper atmosphere models, and carbon/nitrogen cycle models.
- Community Climate Systems Model: Development of Scientific Capabilities - CGD
- Space weather: Model development and data analysis - HAO
- Nested regional climate modeling - CGD
- WRF - MMM
- WACCM - ACD
- WACCM development and extension - HAO
- MOZART - ACD
- Community Atmosphere Model combined with the MOZART chemical Mechanism (CAM CHEM) - ACD
- Upper atmosphere community models - HAO
- Carbon/Nitrogen cycle modeling - CGD
- Comparative solar system studies - HAO
- Analysis, Integration and Modeling of the Earth System (AIMES) - CGD
- Master mechanism - ACD
- Tropospheric Ultraviolet and Visible (TUV) - Radiation Model - ACD
The development and continuous improvement of a comprehensive climate modeling system that is at the forefront of international efforts to understand and predict the behavior of the Earth's climate is a high priority of NCAR research. This includes the Community Climate System Model (CCSM) as well as its component models. The CCSM, run on some of the world's most powerful supercomputers, simulates the many interconnected events that drive Earth's climate. These include changes in the atmosphere and oceans, the ebb and flow of sea ice, and the subtle impacts of forests and rivers.
CCSM is unique among the most comprehensive of global climate models. Primarily supported by the National Science Foundation (NSF) and the Department of Energy (DOE), with additional support from the National Aeronautics and Space Administration (NASA) and the National Oceanic and Atmospheric Administration (NOAA), it belongs to the entire community of climate scientists, rather than to a single institution. Hundreds of specialists from across the United States and overseas collaborate on improvements to CCSM. The model's underlying computer code is freely available on the Web. As a result, scientists throughout the world can use CCSM for their climate experiments.
The CCSM project was started in 1994, although climate modeling at NCAR has a much longer history, stretching back to about 1980. The first version of CCSM was unveiled in 1998, and the most recent version, CCSM-3, was released in 2004. CCSM-3 represents a major advance over earlier versions of the model because it contains far more information about Earth's physical processes. For example, it tracks the flow of major rivers that empty into the oceans and it now resolves five different thickness categories of sea ice within each grid cell, such as the thickness and the melt rate. Moreover, the finer scale and lower viscosity of its ocean allows scientists to capture significantly greater detail about ocean currents and the mixing of salt and fresh water.
CCSM is constantly being updated and improved; CCSM4 is most likely to be released in 2009. In preparation, an interim version, CCSM3.5, was assembled in mid-2007, and is being evaluated from a number of perspectives, with carbon system spin-up a particular focus. In addition to remaining at the forefront of international modeling efforts, the scientific goals of the CCSM project are as follows:
- to use the modeling system to investigate and understand the mechanisms that lead to interdecadal, interannual, and seasonal variability in Earth's climate;
- to explore the history of Earth's climate through the application of versions of the CCSM suitable for paleoclimate simulations; and
- to apply this modeling system to estimate the likely future of Earth's environment in order to provide information required by governments in support of local, state, national, and international policy determination.
ESSL/CGD (in collaboration with scientific and software engineering partners from Universities, DOE, NASA) has been busy in developing component models, integrating those components as candidates considered for the next generation of the CCSM, and exploring these in a variety of ways for understanding the Earth System and climate change. One of the topics identified in last yearís report as a "Plan for 2008" was "a concerted effort to address systematic model biases in the tropics on seasonal and longer timescales." We describe one contribution to that effort here.
A significant reformulation of the parameterization of convection within Community Atmosphere Model (CAM) took place in 2007. The parameterized convection was made much more sensitive to the dilution of air as it ascends in the atmosphere. The convecting parcels were also made sensitive to the change in phase of condensate between liquid and ice, and momentum transports were included in the formulation. The result was a substantial improvement in many aspects of the atmospheric simulation when driven with observed sea surface temperatures, and in the coupled system. The changes were included in the CCSM 3.5, an interim version, which was finalized in October 2007. This uses the new finite volume dynamical core in the atmosphere component, the updated POP 2 code for the ocean component, the latest CICE 4 version for the sea ice component, and a much updated version of the land component compared to the CCSM 3. There have also been significant parameterization improvements in all the components. CLM 3.5 has a very much improved hydrology cycle compared to CLM 3, and the global partitioning of evapotranspiration is greatly improved using the CLM 3.5.
The most significant aspect of CCSM 3.5 is in its simulation of the El Nino - Southern Oscillation (ENSO) in the tropical Pacific Ocean. All previous versions of the CCSM, and most other climate models, had a peak in the ENSO frequency near two years, which is much shorter than in reality. This problem has now been corrected in CCSM 3.5, which shows a frequency peak between 3-6 years. In addition, the correlation between the Nino 3 SST timeseries and SST anomalies across the globe has also been substantially improved. Figure 1 shows this correlation from the HadiSST observational data set, the previous CCSM 3 control, and the new model version with the CAM 3.5. The improvement is quite remarkable, with the new model showing a correlation pattern that is very like the pattern from observations. The correlation is much broader in the eastern tropical Pacific, and the correlation patterns in the Pacific and other oceans are also much improved. We believe this is primarily due to the two modifications of the deep convection parameterization in the atmosphere, which include convective momentum transport and a dilute approximation to calculate CAPE.
Another accomplishment during FY 08 has been to run the first proof of concept short-term projection from 1980 to 2030. This run uses much finer horizontal resolution of 0.5 degree in the atmosphere and land components. The initial conditions for these components were interpolated from the January 1st 1980 fields from a 20th century run using 2 degree resolution in the atmosphere and land components. The two runs were integrated from 1980 to 2030 using observed carbon dioxide levels to 2000, and then the A1B future scenario. The largest improvement was in the sea surface temperature fields in the three major upwelling regions. The SST errors compared to observations in the two runs are shown in Figure 2. The SST errors are reduced by well over 50% off the west coasts of the USA and Peru, and by a smaller percentage off Namibia. This is a significant improvement, but the 0.5 degree run takes about 20 times more computational resource than the 2 degree run. The 0.5 degree version of the new CCSM 4 will be used to make the short-term climate projections for the next IPCC assessment.
During FY 2008, the major CSEG accomplishment has been to finalize and test the sequential, single-executable CCSM. The goal was to create a sequential system that contains backwards compatibility with the current concurrent system, provides "plug and play" capability of data and active components and produces the same climate as the current concurrent system. In addition, the CSEG has ported and tested the results from the CCSM 3.5 running on several new computer platforms across the USA.
2009 and Beyond
2009 will be a very busy year for the CCSM project. The deadline for delivery of individual components of the next version, CCSM 4, is September 30, 2008. CCSM 4 then needs to be finalized, which requires acceptable 1870 Control and 20th century runs to have been made and positively analyzed. This usually takes several months to achieve, and will first be done using a resolution of 2 degrees in the atmosphere and land, and 1 degree in the ocean and sea ice. Then, an acceptable 0.5 degree version of the atmosphere and land components needs to be assembled to be used in the short-term simulations. Finally, a low resolution version of the CCSM 4 needs to be assembled for use in Paleoclimate studies.
Space weather research seeks to understand and work towards predictions of the physical conditions in the geospace environment, particularly when disturbed by energetic events occurring on the Sun. This is a multidisciplinary field of research which requires understanding of solar, solar wind, magnetospheric, and ionospheric physics. It covers a broad range of time scales, including solar cycle variations (years), recurrent solar wind streams (months), coronal mass ejection (CME) propagation and geomagnetic storms (days), flares and energetic particles (minutes). Understanding these phenomena is important for human spaceflight, satellite design, communication and navigation systems used by our increasingly technologically dependent society.
HAO scientists continue to make substantial progress in modeling the many aspects of Space Weather. Coronal mass ejections are a main driver of significant space weather events. Using 3D MHD simulations Yuhong Fan and Sarah Gibson have been able to determine that both the precursor magnetic field configuration in the corona and the initiation mechanism play and an important role in determining the geoeffectiveness of a CME. In particular, they found that eruptions triggered by the torus instability or the kink instability can result in magnetic clouds which differ in their geoeffectiveness due to the different amount of rotation of the escaping flux rope that ultimately affects the orientation of the magnetic field impacting the Earth's magnetosphere. Mark Miesch and colleagues have completed initial development of a heliospheric model using the FLASH code produced by the University of Chicago. This model is currently capable of modeling the configuration of the plasma and magnetic fields into which a CME must propagate before reaching the Earth. AIM scientists led by Wenbin Wang used the CMIT 2.0 Model developed in collaboration with the Center for Integrated Space Weather Modeling (CISM) to study vertical drifts in the F region of the ionosphere. They found that the model does a good job of capturing the temporal variations of these drifts. Furthermore, they conclude that these variations were primarily driven by changes in the solar wind conditions. In collaboration with colleagues at Dartmouth College, AIM scientist Michael Wiltberger began the process of adding mass outflow from the ionosphere into magnetosphere in the Coupled Magnetosphere Ionosphere Thermosphere (CMIT) model. Initial results from these studies have shown that this outflow can have a significant impact on the evolution of the magnetosphere. In particular, simulations with large outflows have shown a multiple substorm sequence for steady IMF conditions which is not seen in simulations for similar conditions which do not include the outflow. Another major achievement of the AIM group, directed by Stan Solomon, in support of Space Weather modeling has been the release of the TIE-GCM, an essential component of CMIT, directly to the community under an open source licensing agreement. In addition, we are working closely with NASA's Community Coordinated Modeling Center (CCMC) to provide the space weather community with the ability to conduct runs on request of CMIT.
Over the course of the next year simulations of CMEs will be conducted using vector magnetic field observations from the recently launched Hinode satellite as basis for determining the shearing and twisting motions driving specific events. These event studies will allow for a direct quantitative comparison of the simulation results with multi-wavelength coronal observations. The heliosphere model will be used to model the solar wind conditions observed during the Whole Heliosphere Interval. Work on this model will also include coupling it with CME eruption modeling to study the evolution of the magnetic field structure within and around the CME as it propagates to the Earth. Now that initial work on including mass outflow into CMIT has been completed we will focus on the extension of this work to incorporate the factors regulating the magnitude and location of the outflow into the model. Development of CMIT will also include efforts to improve the representation of the magnetic field in the inner magnetosphere by coupling it to a ring current model.
Mesoscale processes can have a major impact on large-scale circulations. Yet climate models do not adequately represent this upscale influence of mesoscale processes. NCAR is addressing this challenge by developing a multi-scale modeling system to aid our understanding of climate processes, particularly at the regional scales important to society, and projecting how these may change in the future. A multi-scale modeling system is necessary not only to reduce these climate biases but also to:
(a) downscale climate variability and climate change to the regional scale
for applications such as water resource management over, say, the Western
US, and to determine the climatology of extreme events such as tropical cyclones.
(b) capture the upscale impacts of regional phenomena such as eastern boundary upwelling regimes or mesoscale convection.
The Advanced Research WRF (ARW) and Community Climate System Model (CCSM) have been specifically proposed as candidates from which to develop a two-way coupled multi-scale modeling system. As a first step in this direction, a consortium of University, DOE and NCAR/MMM and CGD scientists engaged in developing the Nested Regional Climate Model (NRCM) from the ARW model. The NRCM has been configured to a tropical channel domain, driven by NCEP-NCAR reanalysis conditions at the north and south boundaries, to enable investigations of the simulation of tropical modes and their interaction with moist convection and to provide high-resolution winds for a study of eastern oceanic boundary issues. Figure 1 shows a snapshot of precipitable water over the tropical channel domain showing tropical cyclones over the North Atlantic. This work included a range of 1-way and 2-way nesting configurations aimed at gaining experience with such configurations and at enabling leading-edge research on the output. The experience with this phase of the program has been an excellent learning activity as well as providing improved understanding of the interactions between mesoscale processes, specifically moist convection, monsoons, and climate. The NRCM has also been instructive in providing a means of distinguishing processes that are, or may be adequately parameterized, from those that cannot and must be resolved in climate simulations.
Our main research goal in FY2008 was to perform a more detailed and extensive analysis of the tropical channel simulations to advance our understanding of tropical wave modes, and evaluate the model's skill in simulating various tropical phenomena using different levels of nesting. Building on strong collaborations between MMM and CGD, and between NCAR and a host of external investigators, significant progress has been made in several areas, with a few key examples highlighted below:
1) Analysis of tropical wave modes
A preliminary space-time spectral analysis of the outgoing long-wave radiation
in FY2006 indicated that the tropical channel model is able to capture important
wave-like modes corresponding to Kelvin waves and Madden-Julian Oscillation
(MJO). In FY2007, a more detailed analysis of the Kelvin waves showed that
their horizontal propagation speeds and vertical dynamical signals are reasonably
well simulated, although the climatological variance of these waves is significantly
under-predicted in the deep tropics (between 5S-5N). A similar under-prediction
problem was found for the MJO, which also appears less well organized than
the observed MJO.
To investigate the causes of this poor MJO representation, an additional analysis was performed of two simulations of an MJO event that occurred during May - June of 1997. Careful processing of the continuous run initialized on January 1, 1996, shows that no MJO events occurred during the May - June period. However, in a simulation initialized on May 1, 1997, the MJO event was successfully reproduced. These findings suggest that model biases built up in the continuous run have a significant negative impact on the simulation of MJO. Additional analyses are being performed to understand the separate influences of initial conditions, lateral boundary conditions, and model physics on the ability of the model to capture various tropical modes.
In FY08, space-time spectral filtering of the simulated OLR was used to isolate easterly waves and tropical-depression type disturbances, extending the Kelvin wave analysis of FY07. Results showed reasonable climatological variance of easterly waves in the Pacific basin, but a significant under-prediction of wave activity in the Atlantic. Presumably this bias stems from biases in the mean state, such as anomalously heavy rainfall over the Pacific and drier conditions over Africa. Given that a large fraction of tropical cyclones in the model are found to develop from easterly waves (as demonstrated through composite analyses), it would seem that the paucity of tropical cyclogenesis cases over the tropical Atlantic can be traced to deficiencies in the mean state.
2) Analysis of the East Asian monsoon
Comparison of the observed and simulated East Asian summer monsoon circulation and precipitation revealed a major weakness in the NRCM simulation. This problem was particularly significant during 1997 when the West Pacific Subtropical High in the simulation was displaced much further east and a low pressure center was generated near the South China Sea that created a northeasterly flow into central and southern China, as opposed to the southwesterly monsoonal flow that brings abundant moisture and precipitation. On the other hand, the simulation compared well with observations during the 1998 summer.
To investigate the reasons for the large difference in model skill from year to year, we performed several sensitivity experiments to isolate the impacts of model initialization, sea surface temperature (SST), lateral boundary conditions, and physics parameterizations. These experiments suggest that SST plays a dominant role in explaining the large difference between the simulations in 1997 and 1998, possibly due to the strong dynamical feedbacks between SST forced convective heating in the western Pacific and the large scale circulation. However, the erroneous circulation in 1997 was insensitive to the convective parameterizations used. In FY08, we conducted a series of 4-month sensitivity experiments for the 1997 East Asian monsoon. We found that the error in the simulation of East Asian monsoon was largely due to the lack of atmosphere-ocean interaction in the current NCRM simulation. Deep convection may be triggered too easily in the model because of the lack of air-sea coupling that should provide a negative feedback to modulate deep convection in areas with warm SST. The excessive convection also accounts for the significant over prediction in the number of tropical cyclones over the western Pacific Ocean. When daily SST together with a simplified diurnal SST model was implemented, the error in precipitation forecast was substantially reduced. This highlights the need to develop a full-coupled atmosphere-ocean regional climate model that is also fully coupled with the global climate model.
3) Analysis of tropical cyclones
NRCM simulations have been explored using a tropical cyclone detection algorithm. The model captured the general global and seasonal distributions of tropical cyclones but consistently overproduced the number of tropical cyclones. Two-way nesting down from 36km to 12km over the Atlantic region for the 2005 season improved both the number and spatial distribution. This dataset has also been used to show the importance of the background flow in modulating easterly waves thereby creating favorable conditions for tropical cyclogenesis, and higher resolution simulations of genesis has shown vortices merging during the period of genesis.
Plans for FY09 include a climate change experiment using NRCM over the North America region, which is currently underway, and represents the second stage of research and model development towards a multi-scale modeling system based on ARW and CCSM. Research is primarily aimed at water resource variations in the intermountain western region and tropical cyclone variations over the North Atlantic region. The period of particular interest is the next 50 years or so, when society will largely have to adapt to those climate changes that are inevitable. The large-scale forcing data is provided from CCSM3 T85 climate change integrations and a series of “time-slice” ensemble experiments are currently being generated for three ten-year periods: 1995-2005, 2020-2030, and 2045-2055. Figure 2 shows a snapshot of outgoing long-wave radiation from July 2055 showing a tropical cyclone off the east coast of the US and a disturbance off the west coast of Africa. This experiment provides a genuine test of the requirements for future supercomputing systems to enable decadal predictions of the regional detail required for planning and adaptation strategies.
Trends in hurricane activity in the North Atlantic, Caribbean and Gulf of Mexico regions will be examined. This ambitious project is providing for the first time, decadal climate simulations of hurricanes at a resolution sufficient to identify key intensity and structural details. Another key focus area will be trends in water resources over the Western U.S.
The NRCM effort represents a step towards a new global weather climate model,
referred to here as the Earth System Model (ESM), at ‘convection permitting’
resolution. A new model is necessary to perform well on future computing platforms.
The ESM is currently in its inception phase and it is anticipated a robust
model is ten years away. Lessons learned from NRCM are directly relevant to
the ESM effort and will steer its development.
NCAR plans that the NRCM will eventually be provided and maintained as a community resource for use by all the academic, government, and private sector communities. The NRCM project has strong community support and is funded largely by the offshore oil industry, the reinsurance industry and NSF, supported by the MMM and CGD divisions.
During the past year, NCAR continued to develop new capabilities for the Advanced Research WRF (ARW) and support it to the community. Over 2000 new users registered to download the code, bringing the total number of registered users to over 7,600. Over half of this total is non-US users, and 113 countries are represented. Figure 1 shows the numbers of registered WRF users and a breakdown by group.
In June 2008 MMM organized and conducted the 9th Annual WRF Users’ Workshop, with over 225 participants attending from many different countries. MMM personnel also conducted three user tutorials on the ARW and WRF-VAR. The two ARW tutorials were held in Boulder with approximately 60 participants attending the first and 71 the second. The WRF-VAR tutorial, also in Boulder, attracted 52 participants. In addition, MMM division staff put on the 2nd East Asia Weather Research and Forecasting (WRF) Model Workshop and Tutorial at Seoul National University in Korea in April 2008. The workshop focused on recent WRF developments in data assimilation, global modeling, and regional climate modeling, applications to high-impact weather and climate, and real-time operations. The workshop and tutorial were conducted as part of the Korea Foundation for International Cooperation of Science and Technology (KICOS) Global Partnership Program, under the Korea Ministry of Science and Technology.
The Whole-Atmosphere Community Climate Model (WACCM) is a comprehensive numerical model, spanning the range of altitude from the Earth's surface to the lower thermosphere. WACCM is built upon the numerical framework of NCAR's Community Climate System Model (CCSM), and is envisaged as a flexible modeling environment, whose domain and component modules can be configured according to the specific problem under study. WACCM incorporates physical and chemical processes required to investigate the coupling among atmospheric regions from the surface to ~140 km. The current version of WACCM (WACCM3) has fully interactive chemistry and dynamics, and can also be coupled to the ocean component of CCSM. Addition of upper thermospheric physics and chemistry is currently underway, and will allow the model to extend upward to about 500 km.
WACCM has contributed to the Chemistry-Climate Model evaluation (CCMval) effort, an international activity under the auspices of the Stratospheric Processes And their Role in Climate (SPARC), and to the most recent Ozone Assessment (2006) of the World Meteorological Organization. In addition, the following topics are currently under investigation using WACCM:
- the effects of solar variability in the middle atmosphere using time-slice simulations during solar minimum and maximum conditions with and without the quasibiennial oscillation in the Tropics;
- the role of parameterized gravity waves and their tropospheric sources in simulations of the whole atmosphere;
- the dynamical variability in the middle atmosphere, in collaboration with University colleagues and other modeling groups;
- the response of the Brewer-Dobson circulation to climate change;
- the validation of chemistry and the dynamics of WACCM against observations (satellite and ground-based);
- testing and application of a new version of the model that can be driven by assimilated meteorological data to study the exchange of mass and constituents in the upper troposphere/ lower stratosphere;
- atmospheric predictability in the whole atmosphere context;
- the application of a version of the model coupled to the CCSM ocean component to understand climate change, including dynamics, temperature and chemical composition, in the 20th century and predict changes in the 21st century.
Recently published papers on these and other subjects may be found in the WACCM website . During 2008-2009, major emphases of the WACCM project will include: the study of the effect of the middle atmosphere on tropospheric climate; extension of WACCM to 500 km with the addition of an electrodynamics model component; improvements to the parameterization of mesoscale gravity waves; elucidation of the factors that accelerate the Brewer-Dobson circulation in the context of global-warming; and comparison of WACCM tides and other fast wave motions with global satellite observations.
The goal of the Whole Atmosphere Community Climate Model (WACCM) is to develop a model that extends from the Earth surface to the upper thermosphere, and self-consistently resolve the dynamical, chemical, radiative, and electrodynamical processes and the coupling between atmospheric regions. The current standard WACCM version (WACCM3) has an upper boundary in the lower thermosphere (~140 km).
In the previous year (FY07), we developed a WACCM extended (WACCM-X) to the upper thermosphere at pressure 3.4x10-7 Pa (~500 km),
and implemented thermospheric physics modules, including major species
diffusion, the constituent-dependent specific heats, gas constant, and mean molecular weight, and revised the treatment of the vertical diffusion equations for minor species and heat conduction equation. In FY08, we have built on the WACCM-X and further tested and validated the model. Major achievments include:
- Full model-year runs of WACCM-X under solar maximum, medium, and minimum conditions. Monthly mean climatology of winds and temperature structures in the upper atmosphere show general agreement with empirical models (MSIS-00 and HWM) and the TIME-GCM.
- The semi-annual variation of the O/N2 ratio in the upper thermosphere is reproduced by the model, including the magnitude of the variation and its dependence on the solar flux.
- Tides from the model were compared with TIMED/SABER and TIDI obserbations. The seasonal variability of the migrating diurnal tide, with maximum at March equinox and secondary maximum at September equinox, are in good agreement with observations, though the tidal amplitude from the model is weaker. We also demonstrated that the model amplitude is in much better agreement with observations when the vertical resolution of the model is doubled.
- The nonmigrating eastward wavenumber 3 component from the model, which is the second strongest diurnal tide in the lower thermosphere, shows excellent agreement with that derived from SABER and TIDI in both its amplitude and seasonal variability.
- The thermospheric tides show strong short-term variability, which is likely due to penetration of the lower atmospheric perturbations and their interaction with tides.
We are currently merging WACCM-X with WACCM 3.5. A significant improvement in the new version is the gravity wave source specification based on actual sources of convection and frontogenesis. We will examine its impact on the thermosphere. We are currently working on the electrodynamics of the model ionosphere by implementing ambipolar diffusion and ExB drift in the WACCM.
The Model for Ozone and Related chemical Tracers (MOZART) is a global offline chemical transport model. Version 2 (MOZART-2) is available to the public through the NCAR Community Data Portal and has been downloaded by 110 users.
Two new versions, MOZART-3 and MOZART-4 have been recently completed and are actively used by ACD scientists. MOZART-3 is an extension of MOZART-2 into the stratosphere, with the addition of halogen chemistry and heterogeneous processes on polar stratospheric clouds (Kinnison et al., JGR, 2007). MOZART-4 has been updated over MOZART-2 to improve tropospheric chemistry simulations, with more detailed representation of hydrocarbons and tropospheric aerosols. Examples of some of the studies using MOZART-4 are shown under Strategic Priority 1 in Section 6 and Section 7.
The chemical schemes of MOZART-3 and MOZART-4 have been incorporated in the coupled chemistry-climate models WACCM and CAM-Chem.
MOZART-3 and MOZART-4 (source code and documentation) will be made available to the public on the NCAR CDP by the end of 2008.
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). The continued incorporation of interactive chemistry capability in the Community Atmosphere Model (CAM) has reached a fairly stable state and now encompasses a variety of options to accommodate the needs of the coupled climate model, including a full interaction with the cloud microphysics (to represent the indirect effect, through collaboration with CGD and MMM scientist); in particular, using the implemented MOZART framework, CAM-chem can now be configured to combine prognostic and diagnostic variables. As a result. aerosols can either be prescribed, simulated using simple input oxidant fields, or simulated using the full MOZART-4 aerosol parameterization, or a combination of both; this flexibility is important to understand the specific role (radiatively and through cloud-aerosol interaction). In addition, the flexibility enabled the quick implementation of the modal (3 and 7 modes) aerosol scheme developed by S. Ghan (PNNL).
In addition, a version of CAM-chem with a representation of stratospheric chemistry was developed as a tool to represent ozone changes in the lower stratosphere; simulations over 1970-2005 indicate a very good comparison of ozone trends with respect to observations. This version will be used in 2009 for chemistry simulations in support of IPCC AR5.
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. In collaboration with scientists from Lawrence Livermore National Laboratory and University of California, Irvine, we have extensively tested 3 chemical mechanisms for tropospheric chemistry with increasing complexity of non-methane hydrocarbon (NMHC) representation; the overall goal is an understanding of how much chemistry is needed for specific applications (regional pollution chemistry or climate). In particular, comparison with the Mexico City (MIRAGE) campaign indicates (Figure 1) that an intermediate representation of NMHC is sufficient to represent ozone at the surface.
CAM-chem is now being merged with WACCM to allow for more flexibility in the model configuration and added ease of maintenance; indeed, this approach has eliminated code redundancy as much as possible. This merged code will now be the only version of CAM-chem or WACCM to be developed; this will allow for improvement from one science community to directly benefit the other one.
FY2009 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.
The computation of the radiative effects of the atmospheric composition is central to efforts to understand climate. A new radiative transfer model (RRTMG), developed by AER, Inc., has been incorporated into CAM/CCSM. The interface between the atmospheric specifications in CAM and the radiative solver has significantly improved user flexibility in testing new optics and testing radiative forcing due to changes in atmospheric composition as well the extensibility for new species. Microphysical specifications in CAM have been made consistent with optical parameterizations. Collaborators from LBL, UC Berkeley, PNNL, DRI, and AER have contributed optics, solvers, and validated the new package. This work is funded by DOE/SCIDAC.
FY2009 plans include efforts to study the new radiation budget of the climate system.
Microphysics parameterization for CAM
ACD and CGD scientists have been leading a collaborative development effort for a new microphysics parameterization for CAM. The goal of this effort is to develop an advanced microphysics package which can represent the size of cloud drops, and simulate how cloud drops are influenced by the distribution of aerosols. The ultimate goal is to quantify aerosol indirect effects in CAM and CCSM. This work dovetails with other studies in ACD, MMM and CGD of cloud microphysics, both in observations and in models. An important component of the broader activity is the development of better satellite data sets of cloud microphysical properties for comparing the CAM and WACCM simulations to observations. This work has recently been extended to treat the effects of ice clouds and ice cloud aerosol interactions.
HAO scientists have developed a suite of upper-atmospheric models, in collaboration with scientific visitors and scientists at universities, government labs, and other organizations. These models are made available for use by the community, typically through collaborations between HAO scientists and scientists in the community. A central model is the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) and simplified variants of it. The TIME-GCM simulates the three-dimensional, time-dependent global dynamics, chemistry, energetics, and electrodynamics of the mesosphere, thermosphere, and ionosphere, for given inputs representing solar, magnetospheric, and lower-atmospheric effects. Other HAO models with extensive use by the community are the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure for synthesizing high-latitude observations of ionospheric electric fields and currents, the Global-Scale Wave Model (GSWM) for calculating atmospheric tides and planetary waves from the ground through the thermosphere, and the GLOW model for calculating the effects of solar ultraviolet and X-rays as well as energetic particles. These models are used to understand the processes affecting the dynamical, electrodynamical, thermodynamical, and chemical conditions in the Earth's upper atmosphere, its response to the Sun's variable radiative, particulate and magnetic emissions, and its coupling to the lower atmosphere and the magnetosphere.
The models have been upgraded through improvements to atmospheric tidal forcing, auroral precipitation, and coupling with magnetospheric electrodynamics. In collaboration with the University of Colorado, the Global Ionosphere Plasmasphere (GIP) model has been coupled with the TIE-GCM, to allow replacement of the TIE-GCM imposed upper boundary conditions on the ionosphere with a physical model. Model results have been provided to collaborators in the community. A documented version of the TIE-GCM, version 1.9, has been made public at http://www.hao.ucar.edu/modeling/tgcm/ . This work has been sponsored by NSF base support to NCAR, NSF Space Weather special funds, and NSF CEDAR special funds. It has also been supported by NASA and DOD programs.
Highlight: Modelling the effects of changes in the Earthís magnetic field from 1957 to 1997 on the ionospheric hmF2 and foF2 parameters
Long-term trends in ionospheric electron density and peak height
have been used to study global-change effects in the upper atmosphere.
However, the ionosphere responds not only to increased atmospheric
carbon dioxide, but also to slow variations of the Earth's magnetic
field and to trends in geomagnetic activity. In order to quantify the
importance of changes in the Earth's magnetic field, the NCAR TIE-GCM
was used to model the ionosphere for the magnetic field as it existed
in 1957 and 1997, taking into account self-consistently the changes in
thermospheric winds due to changes in ionospheric drag. Substantial
changes in the peak height, hmF2, (up to ±20 km) and critical
frequency for radio-wave reflection, foF2, (up to ±0.5 MHz) are
predicted over the Atlantic Ocean and South America. This would make up
a significant contribution to observed long-term trends in these areas
and therefore must be taken into account in their interpretation.
Modeled trends of hmF2 and foF2 exhibit a strong seasonal and diurnal
variation, highlighting the importance of separating data with respect
to season and local time. Most of the modeled changes in hmF2 and foF2
can be related to changes in plasma transport up or down magnetic
field lines driven by neutral winds, changes which are mostly caused by
changes in the inclination of the field, though changes in declination
and neutral wind also play a role. Changes in the vertical component of
the electrodynamic drift velocity have relatively little effect (Figure 1).
This work was supported in part by NSF base funding. Graduate student visitor Ingrid Cnossen was supported by a Marie Curie fellowship of the European Union.
Reference: Cnossen, I., and A.D. Richmond (2008), Modelling the effects of changes in the Earth's magnetic field from 1957 to 1997 on the ionospheric hmF2 and foF2 parameters, J. Atmos. Solar-Terr. Phys., 1512-1524.
For FY09, we plan to continue model upgrades, testing, and scientific analysis in collaboration with the community. Model developments will continue to be documented, and upgraded versions of the TIE-GCM source code will be made available at the www.hao.ucar.edu/modeling/tgcm web site. Results of scientific studies will be published. Particular foci will be testing and implementing the full electrodynamic coupling of the GIP plasmasphere model with the TIE-GCM, continuing to transfer and document process modules from the TIME-GCM to WACCM, and continuing to test and implement modules coupling the magnetosphere with the ionosphere and thermosphere.
ESSL scientists have recently completed a model development project to bring together parallel efforts in the climate modeling and ecological modeling communities, integrating a detailed treatment of the terrestrial carbon cycle with a state-of-the-art land surface model (the Community Land Model - CLM). The resulting model has now been tested and its performance documented in offline configurations. A critical application of the model has been to study the influence of carbon-nitrogen cycle coupling on present-day and potential future climate-carbon cycle feedbacks. Inclusion of the nitrogen cycle has the net effect of limiting atmospheric carbon dioxide uptake, with more carbon dioxide remaining in the atmosphere to play a role in climate forcing. Development and evaluation of the simulated terrestrial carbon cycle and climate-carbon cycle feedbacks continues.
ESSL scientists participated in a project known as C-LAMP (Carbon LAnd Model intercomparison Project) to evaluate two different implementations of the terrestrial carbon cycle in the CLM. One model, CLM-CN, includes carbon-nitrogen interactions. A second model, CLM-CASA', simulates only the carbon cycle. The first paper describing the evaluation of the land model predictions against a broad database of observations (remotely sensed and in situ) of many different ecosystem states and fluxes has been submitted. Both models replicate key features of the terrestrial carbon cycle, but also have key deficiencies and model development continues.
Development of a fire module, coupling to the dynamic global vegetation model, implementation of land cover change, and a model of soil NO, N2O and N2 emissions adds to the functionality of the CLM.
2009 and Beyond
The work in FY 2009 continues to focus on the development and evaluation of the terrestrial carbon model in preparation for the release of CCSM 4.0. The primary scientific focus beyond the CCSM 4.0 release is to examine human and natural feedbacks and forcings in the earth system operating through the biogeochemical cycles.
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). The AIMES project endeavors to extend Earth System modeling approaches to include dynamics of human activities alongside biogeochemical and biophysical processes of the coupled climate system. Modeling activities in AIMES include improving biophysical and biogeochemical components of global models and testing the sensitivity of tradeoffs in vulnerability and resilience in terms of economic and ecosystem consequences.
AIMES and the WCRP Working Group on Coupled Modeling (WGCM) have collaborated to develop a strategy for next generation climate simulations for the upcoming Fifth Assessment.
Report of the IPCC (AR5). Climate modeling experiments for AR5 will include both long term (e.g., 2100 and beyond) and decadal prediction (Hibbard and Meehl 2007). In addition, AIMES also collaborates with the Integrated Assessment Modeling Consortium (IAMC) on the generation of scenarios for AR5. This collaboration has led to close collaboration and improved understanding of the provenance of the radiative forcings provided by the integrated assessment community and the strengths and limitations of climate modeling between the two modeling communities. This collaboration has resulted in a proposed parallel process (Figure 1) where the climate, integrated assessment and impacts, adaptation and vulnerability communities work much more closely towards the development of new scenarios for possible assessment activities beyond AR5. To initialize the AR5 process, AIMES worked with the IAMC and WGCM on the development and harmonization of land use, land cover and emissions between the climate and integrated assessment models for the representive concentration pathways that will define the scenarios for AR5.
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 investigates 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 is to collaborate with the IPCC Working Groups to develop climate change stabilization experiments with coupled atmosphere/ocean general circulation models, Earth System and Integrated Assessment models. AIMES, on behalf of the IGBP is leading an applied Earth System Science initiative to foster collaboration and exchange of information between the scientific community and resource managers, policy and and assessment communities and development agencies. 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) with topics including integrating indirect human activities (e.g., land use) with the Community Climate System Model (CCSM), Urbanization, biogeochemistry and the climate system, and land-use decision making for Earth system models. In 2008, NCAR hosted a YSN on Cultural Use and Impacts of Fire: Past, Present and Future.
The Integrated History of People and Earth (IHOPE) activity started in 2005 with a Dahlem conference on Collapse or Sustainability: an Integrated History and Future of People on Earth (Costanza et al., 2007, 2008). 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. AIMES is communicating with the Stockholm Resilience Centre (SRC) in Sweden to organize IHOPE-related activities targeting issues on historical, even decadal, timescales on the various ways of understanding the growth of environmental prediction and modeling, largely a 20th c. phenomenon (and, an understanding of IHOPE itself as a feature of modern "historiography"). AIMES and the SRC are discussing a series of meetings in 2009-2010, encompassing both the global south and the global north.
Sponsoring entities for workshops, symposia and colloquia include: NSF, NASA, EC-ACCENT (EU EC_FP6), IGBP, MPI (Germany), QUEST (UK), Arizona State University, University of Vermont, IHDP, the IAMC and WCRP.
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 Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A), producing the only fully explicit mechanism for the gas-phase atmospheric oxidation of hydrocarbons. In collaboration with Bernard Aumont and Marie Camredon (U. Paris), ACD scientists have removed the 8-carbon limitation on hydrocarbon chain length, by assuming complete condensation to the aerosol phase for species with vapor pressures lower than 10-13. For conditions relevant to Mexico City and chain lengths up to 10 carbons (the largest hydrocarbons for which observations are available), the gas phase mechanism consists of ca. 1.2x106 reactions among ca. 2x105 different chemical species. By allowing for gas-particle partitioning of these condensible compounds, they simulated the formation of secondary organic aerosols (SOA) in Mexico City for the conditions of the MIRAGE campaign. Results show significant SOA production for several days, although at rates slower than observed.
ACD scientists, together with researchers from Pacific Northwest National Labs and the U. of Washington used smog chamber measurements to show that hydrophobic aerosols play no role in SOA formation, contrary to previous theories. ACD scientists are also collaborating with PNNL researchers to provide input to a comprehensive, generalized inorganic-organic aerosol model.
FY 2009 work will continue development and evaluation of the GECKO-A mechanism generator, and perform further box model simulations for Mexico City to interpret results from the MIRAGE campaign.
This work is funded by NSF/NCAR and the DOE.
The Tropospheric Ultraviolet-Visible (TUV) radiation model calculates spectral irradiances and actinic fluxes, biologically active UV radiation at the surface, and photolysis coefficients (J values) for atmospheric chemistry use. TUV version 4.5 is available to the community through the NCAR/SCD Community Data Portal. ACD scientists have also made available global UV climatologies using TOMS v.8 ozone, specifically, maps of UV-A, UV-B, and several biologically weighted exposures (erythema, non-methane skin cancer, and vitamin D production). [Lee-Taylor, J. and S. Madronich, Climatology of UV-A, UV-B, and Erythemal Radiation at the Earth's Surface, 1979-2000, NCAR Technical Note TN-474-STR, August 2007.] An analytic formula for the UV Index in terms of the ozone column and sun angle allows efficient parameterization of UV effects of ozone changes.
ACD scientists collaborated with university colleagues to apply the TUV model and UV climatologies to diverse problems including skin cancer incidence and plant-based methanogenesis. ACD scientists and university colleagues are also examining the UV radiation field during the MIRAGE-Mex field campaign. Mexico City's pollutants (ozone, sulfur dioxide, nitrogen dioxide, and aerosols) reduce the UV radiation field in the boundary layer by 10-20% and at the surface by 20-40%. Preliminary analyses suggest that aerosols are more absorbing at UV wavelengths than at visible wavelengths. The UV reductions slow photochemistry significantly, allowing for greater export of yet-unreacted pollutants.
This work is funded by NSF/NCAR.