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Goal 1, Priority 2: Investigating the Interactions of the Atmosphere, the Broader Earth System and Human Society

In the past, meteorology and climatology were considered separate fields, largely because of disparate time and length scales. Today, the two fields are strongly coupled, not only because climate provides boundaries for investigating the weather, but also because localized events can influence larger climatological scales. The activities that NCAR scientists focused on this year ranged from collecting in situ data to better understand climate, weather and related phenomena, to developing and analyzing ways to better model natural processes and working with university partners to devise ways of tackling scientific questions.

FY2007 Accomplishments

Click to enlarge. The time series of September Arctic ice extent from CCSM-3 (black), the CCSM-3 5-year running mean (blue) and the satellite observations (red), with the identified abrupt event shown by the grey shading. The sea ice conditions for the (b) 1990-1999 average, the (c) 2010-2019 average and the (d) 2035-2044 average are also shown and indicate the realistic present day ice cover simulated by CCSM-3 and the rapid decline that occurs by mid-century. Most, if not all of the FY2007 research efforts under this priority rely on cross-community collaboration. Among the many examples of enhancing scientific and societal understanding of the effects of global climate change is the climate modeling being done around Arctic sea ice retreat. Considerable effort has occurred–and work continues–to examine observed and projected changes in the sea ice system, and the consequences of a seasonally ice-free Arctic ocean for the climate system. CCSM integrations exhibit abrupt reductions in the future summer sea ice cover, with the most extreme event going from 80% September ice coverage to 20% coverage in approximately 10 years.

The Earth’s oceans have a significant impact on the Earth’s system, making it important to understand ocean processes, and using this understanding to improve ocean models. CGD’s FY2007 efforts in this area include prediction of the Earth’s energy, water and biogeochemical cycles, and understanding natural and human influenced climate variability, including high impact variations such as sea level rise. In turn, the ESSL objective of understanding two-way scale interactions within the Earth system is central to improving our understanding of how ocean circulation features such as coastal upwelling zones, western boundary currents, and meso-scale eddies are affected by and affect the basin- to global-scale ocean circulation. In a complementary way, global atmospheric modeling efforts within CGD are examining the sensitivity of physical processes in the atmospheric component model to small errors in Sea Surface Temperature (SST). This work has illustrated large simulation sensitivity, particularly at low latitudes, pointing to the strong coupling existing between the ocean and atmosphere.


Click to enlarge. Ocean velocity vectors and temperature in the north-west Atlantic and Labrador Sea near 50 m depth, averaged over years 101 through 120 of CCSM coupled model integrations: a) with higher viscosity (CONT, top panel) and b) with lower viscosity (NOSMAG, bottom panel). In both cases, the white contours are the 5% (offshore) and 50% (onshore) average sea-ice concentrations. As expected, the currents in (a) are stronger than (b), and advect more warm water into the Labrador Sea, especially along the west coast of Greenland. This warm water tends to melt the sea ice and initiate the positive ice-albedo feedback, where the reduced ice lowers effective albedo, which allows more absorption of solar radiation, which warms the ocean and leads to more melting. As a result, the sea-ice distribution in (b) is much more like the observed.

In addition to our atmosphere and ocean modeling work, FY2007 saw the CCSM Biogeochemistry and Land Working Groups place a strong emphasis on development and testing of new CCSM component models that improve the representation of known interactions between ecosystems, biogeochemistry, and climate in our fully coupled model. Accomplishments over the past year include adoption of a new land model component (CLM-CN) for the interim model version CCSM 3.5. CLM-CN includes a fully prognostic treatment of both carbon and nitrogen cycles within terrestrial ecosystems, and retains all of the mechanistic detail from CLM related to physical and biophysical mechanisms of land surface-climate interaction.

In collaboration with a broad group of university investigators, ESSL scientists also recently completed a series of fully coupled simulations linking new land and ocean ecosystem components to the physical components of CCSM. This system has been used to investigate the influence of climate-biogeochemistry coupling on climate-carbon cycle feedback finding very significant impacts due to the new coupling. See the ESSL LAR for further details.

Mentioned under the previous priority, the MIRAGE initiative aims to understand the fate of urban emissions in the downwind atmosphere. Important new results include:

  • Air downwind from Mexico City continues to be chemically active, with production of ozone (O3) and organic particles continuing for several days.
  • Organic reactivity is dominated by hydrocarbons near the surface in Mexico City, but by oxygenated organics (particularly aldehydes) in the outflow.
  • Reactive nitrogen appears to be lost more rapidly than expected, and a significant fraction is unidentified.
  • For more MIRAGE results, see the ESSL LAR.

The collection and analysis of data on aerosols, clouds and storms have been important element of the rainfall enhancement programs RAL conducts throughout the world. Field programs in West Africa and in Saudi Arabia in 2007 have yielded important new insights into the effects of aerosols as agents of significant climatic perturbations, particularly with respect to cloud microphysical processes and precipitation. For more results, see the RAL Annual Report.

Scientists and support teams from EOL and other NCAR labs collaborated with university investigators to plan and conduct the second Airborne Carbon in the Mountains Experiment (ACME07) campaign using the University of Wyoming’s King Air aircraft. ACME endeavors to shed insight on carbon dynamics in mountain forest regions by developing new methods for estimating carbon exchange at local to regional scales. This second campaign began in early spring and ran through the fall, focusing on Colorado and Wyoming.

EOL also collaborated with investigators from Harvard, NOAA, and Scripps Institution of Oceanography, and ESSL’s The Institute for Integrative and Multidisciplinary Earth Studies (TIIMES), to begin planning the HIPPO (HIAPER Pole-to-Pole Observations) campaign, which will investigate the global carbon cycle. Data collection will be done on the NSF-NCAR Gulfstream V (GV)–formerly known as HIAPER (further project details are available in Goal 5, Priority 1). EOL and TIIMES staff also continued operating the Regional Atmospheric Continuous CO2 Network in the Rocky Mountains (Rocky RACCOON) network of CO2 analyzers, collaborating with University of Utah and University of Wisconsin to investigate regional carbon cycling in the Rocky Mountains, this work will continue in FY2008.

In April and May of 2007, EOL and ESSL/ACD scientists and support staff became involved in studying the role of aerosols in climate and weather. EOL deployed the GV in support of the PACific Dust EXperiment (PACDEX), which is designed to provide insights on the dynamics of the Eurasian-Pacific-North American dust plume. The dust plumes’ full effect has not been widely explored because there has not been, until recently, an airborne platform capable of sampling the plume throughout its evolution, in situ, as it moves across the Pacific Ocean. The GV solves this problem.

The Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, Water, Organics and Nitrogen (BEACHON) program is providing a detailed, quantitative characterization of biosphere-hydrosphere-atmosphere interactions. These quantitative characterizations are being used to improve regional and global models of the Earth system. Part of the BEACHON program, the Canopy Horizontal Array Turbulence Study (CHATS) is a prototype “super site.” Located in a relatively simple ecosystem–a walnut orchard–unmanned instrumentation was used to observe effects of everyday turbulent flow over the orchard. Microscale measurements of phenomena such as boundary layer depth and local mesoscale circulations, atmospheric CO2 and water vapor, among other characteristics, are being studied and will be put into context of the larger atmospheric environment.


Click to enlarge. Effects of the hybrid parameterization applied in MM5 at 60 km grid spacing illustrated by the diurnal variability of precipitation over the continental U.S. a) Betts-Miller convective parameterization. Precipitation is under-predicted and the organized system travels too slowly, about 10 m/s compared to the observed 17m/s. b) hybrid parameterization (i.e., Betts-Miller coupled to a representation of mesoscale stratiform heating and the mesoscale downdraft). c) As in b) except the explicit (‘grid-scale’) precipitation is added. The mesoscale components augment the precipitation and increase the propagation speed while it operates (curved line in top figure.) [From Moncrieff and Liu ( 2006)]. In the realm of hydrology studies, scientists contributing to TIIMES’ Water Cycle Program are striving to improve representation of the hydrologic cycle in climate models. In FY2007, program focus was on improving representation of convective precipitation downwind of major continental mountain ranges. Toward this end, Mitch Moncrieff and Changhai Liu developed a new parameterization of convection and looked at some of the key characteristics of these systems, for example, organized, mesoscale transport of heat and momentum to larger scales over the continental United States. Work done by Wojciech Grabowski on the super-parameterization concept, provides an alternative approach to the convection question. Grabowski uses a full 2D, high-resolution cloud model at each grid point to more accurately account for the shear impacts on clouds and momentum transport. His efforts focused on improving the model’s microphysical scheme, including the impact of aerosol particles. This approach to modeling precipitation will become more attractive to climate models as computer power increases.

During FY2007, RAL continued to provide hydrological modeling support for a World Bank-funded project for the country of Romania. Working in collaboration with scientists from Baron Advanced Meteorological Services we have completed a suite of enhancements to the Noah-distributed hydrological model and implemented and tested the new modeling system in several new river basins in both the United States and in Romania. All components of the Noah-distributed hydrological modeling system arebeing fully parallelized for use on NCAR supercomputers.

A new project aimed at improving predictions of short term (hours to one day) flash flooding events in the Colorado Front Range was initiated during FY2007. This project deploys, in an unprecedented manner, the newly developed Noah-distributed hydrological modeling system over a large region in north-central Colorado. During FY2007, the model domain was defined and attributed and case study simulations were executed that focused on simulating the 1997 Ft. Collins flash flood. Additionally, this model was coupled to the Advanced Weather Research and Forecasting model for fully-coupled simulations of high-impact hydrometeorological events. Results from an initial round of sensitivity studies have been completed and were presented at the annual WRF User’s workshop in late June.

RAL scientist, David Gochis, remained heavily involved in the NOAA-NSF-NASA sponsored North American Monsoon Experiment (NAME), co-operating a regional rain gauge network in western Mexico with collaborators at the University of Sonora. The network is now entering its seventh year of operation and continues to provide research quality data for warm season precipitation research in western Mexico and to evaluate satellite-based estimates of precipitation. Studies are now underway using parcel trajectory analysis tools to analyze the transport of moisture, which drives monsoon rainfall.

While precipitation is a key component of the water system, surface and ground water dynamics play similarly important roles. A TIIMES and University of Arizona-run hydrometeorology workshop in November 2006 explored various aspects of hydrology relevant to the proper simulation of the water cycle in climate models, including the education of students in this important area.

Click to enlarge. Divergence (left panel) and vorticity (right panel) for 7 DYCOMS-II cases. The thick vertical bar is one standard deviation of the estimated random error and the thin vertical bar is one standard deviation of the mean calculated from the measurements. During the past year, data from the NCAR C-130 aircraft from the Dynamics and Chemistry of Marine Stratocumulus (DYCOMS-II) Experiment were used to estimate the accuracy of divergence and vorticity measurements from the horizontal wind field in the atmospheric boundary layer and to refine techniques used to obtain these measurements. Results indicate that wind-field measurements with minimal systematic errors should provide estimates of mesoscale divergence and vorticity with much greater accuracy than is now possible with other existing methods.

Click to enlarge. Analysis of the vertical momentum flux in the marine surface layer for varying wave age with winds following and opposing surface water waves. The vertical axis compares the momentum flux generated by atmospheric turbulence and the surface wave field. As the winds decrease or the speed of the waves increase, the momentum transfer from the ocean to the atmosphere becomes larger. Observational results are indicated by red dots and by X. Results for flow over a stationary land surface (note wave age = 0) are indicated by an open green square with an error bar. LES results are indicated by blue dots. The vertical dotted line indicates the speed (or wave age) where the winds and waves are in equilibrium with each other. Other accomplishments in FY2007 focused on winds and waves in marine boundary layers, which are often in an unsettled state as fast-running swells generated by distant storms propagate into local regions and modify the overlying turbulent fields. A large-eddy simulation (LES) model with the capability to resolve a moving sinusoidal wave at its lower boundary was used to investigate this low-wind/fast-wave regime. An analysis of the momentum flux from recent field campaigns Coupled Boundary Layers Air-Sea Transfer (CBLAST) (see Figure 6 below) and the Ocean Horizontal Array Turbulence Study (OHATS) validate the LES predictions and illustrate that the wave field modifies the drag of the ocean in fundamentally different ways than a rough land surface. Read more about this work and MMM’s efforts to nest a finer-grid LES inside a coarser-grid LES, using the WRF modeling system’s dynamic core in the ESSL LAR.

SERE scientists also conduct research that seeks to provide better understanding of the interactions among long-term climate change, climate variability, and weather extremes, while reducing societal vulnerability to their impacts. Among SERE’s FY2007 efforts, planning for and conceptual development of the Society-Water and Natural Systems (SWANS) program began. The SWANS pilot project launched in FY2007, focusing on the Colorado River Basin and the effects of climate change on snow processes in Colorado's mountains, and the resulting implications for water management and policy. This project also involves RAL and ESSL scientists, and collaborators from the University of Colorado and NOAA.

SERE’s efforts to understand changes in society-relevant extremes include looking at how climate change can influence climate extremes–such as heat waves, heavy rainfall, drought, etc.–not only in quantity, but also in intensity and variability. During FY2007, researchers from SERE’s Institute for the Study of Society and Environment (ISSE) continued comparing model simulations of extremes to observed trends in order to validate climate model projections.

Click to enlarge. Comparison of observational data, NCEP reanalysis data, NCEP-driven WRF data, and NCEP-driven WRF data for long-term average winter (DJF) ISSE scientists also spearheaded the North American Climate Change Assessment Program (NARCCAP) at NCAR. This international program includes principal investigators from Canada and the UK and aims to produce multiple high-resolution climate change scenarios for most of North America. The initial program phase of the program, which entailed creating high-resolution, regional climate model simulations using National Centers for Environmental Prediction (NCEP) re-analyses boundary conditions from 1979 to 2004, was completed in FY2007.

FY2008 Plans for Strategic Priority 2

The role of natural versus external forcing in driving transitions and potential predictability of climate- and weather-related events will continue. Among NCAR’s plans to address these scientific questions in FY2008 are the following:

  • Analysis of sea ice projections from other (non-CCSM) models included in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4). CGD scientist are analyzing these models’ sea ice mass budget changes, the relationship to changing surface heat budgets, and the impact on the timing and transition to seasonally ice-free conditions. Implications for future polar bear habitat loss are also being assessed.
  • A high-latitude terrestrial climate change feedback project has been initiated to investigate how permafrost thaw will affect the Arctic’s carbon balance. This interdisciplinary project aims to improve our ability to simulate, understand, and predict high-latitude terrestrial climate feedbacks in CCSM, with a particular goal to develop a version of CCSM that can address the critical carbon issues in the Arctic tundra.
  • In FY2008, MMM and CGD will generate a large-domain (about 500 km x 500 km x 20 km), high-resolution (a grid mesh about 100 m x 100 m x 20 m) LES of a tropical deep convection system in which deep and shallow convection, as well as large turbulent eddies (inside the PBL and inside the convection) are all resolved. MMM scientists plan to use a new Vector Vorticity Model developed by CMMAP scientists to perform such a LES. This will be the first attempt to simulate tropical deep convection with its associated shallow convection and turbulence motions explicitly calculated as well.
  • Scientists in CGD’s Terrestrial Sciences Section have initiated a project to merge the carbon and nitrogen cycling capability of the CLM-CN model with a previously developed global dynamic vegetation model (CLM-DGVM). ESSL scientists will also be exploring the introduction of coupling between the carbon, nitrogen, and phosphorus cycles.
  • MIRAGE data analysis and interpretation is still in its earliest stages, and is expected to continue over the next several years. The FY2008 phase is expected to involve model simulation and evaluation (both process-level, and 3D chemistry-transport models).
  • For the first time in a rainfall enhancement experiment, dual-polarization, dual-wavelength and advanced weather radars will all be implemented in the field for a new RAL program in Queensland, Australia. In combination with airborne measurements, these radar systems will make it possible to trace the physical chain of events from the natural or seeded small particles to droplet and ice crystal growth, subsequent precipitation development in clouds, and ultimately rain on the ground in both natural and seeding clouds.
  • Analysis of PACDEX data will be a priority for EOL and ACD scientists in FY2008/2009.
  • In the upcoming year, ESSL/MMM scientists will continue analysis of the CBLAST and OHATS databases, and extend these analyses to the OBL. In the latter, focus will be on wave and current interactions under high winds.
  • In late September 2007, a team of staff from EOL completed the site survey for TiMREX, a joint U.S.-Taiwan multi-agency field program. The field program will be conducted from 15 May to 30 June 2008 in the northern South China Sea, western coastal plain and mountain slope regions of southern Taiwan.
  • BEACHON will continue developing its observational infrastructure. In FY2008, this work will include instrument acquisition and development of a BEACHON super-site, which will be placed in a water-limited region of Colorado. A BEACHON super-site workshop will be convened to refine these plans with university partners, as well as scientists from across NCAR.
  • During FY2008/2009, the Water Cycle Program will focus on evaluating the Moncrieff/Liu convective scheme, as well as other candidate schemes. Water Cycle Program researchers will also use diagnostic studies to better understand linkages between soil moisture and precipitation in climate models.
  • A new collaboration between RAL scientists and Dr. Enrique Vivoni of New Mexico Tech will focus on observing and modeling hydrometeorological processes in the North American monsoon regions of northwest Mexico.
  • With baseline development and implementation of the Noah-distributed hydrological model for the Colorado Front Range nearing completion, several additional efforts are being initiated. RAL scientists will begin to develop new quantitative precipitation forecasts, using RAL’s nowcasting systems and the Advanced Weather Research and Forecasting (AWRF) model, for operational deployment during the spring and summer of 2008.
  • New hydrometeorological model development is planned within RAL. New forecast products along with the hydrological forecasts will be shared with the Denver/Boulder National Weather Service office through a new collaboration initiated in September 2007.
  • During FY2008, NCAR scientists will work toward establishing SWANS as a multi-institutional collaborative effort. Diagnostic studies will be used to explore implications for water management and policy, and compare findings to IPCC AR4 diagnoses, and other regional assessment models.
  • Currently, the NARCCAP team is analyzing output from the NCEP runs, and is archiving the data. In FY2008, SERE/ISSE will make these data available to the broader climate community.
  • FY2008 work related to changes in society-relevant extremes will include applying new methodology to extreme, high sea surface temperatures in the tropics to ascertain whether increasing trends are consistent with the thermostat hypothesis. This research will have important implications for assessing potential impacts of global warming on coral reefs.
  • In FY2008, SERE scientists will also initiate the RESUCCCITIES (Initiative to Attain Resilient and Sustainable

Relationships among Carbon, Climate, and Cities) program to address three major constraints affecting urban areas. These include:

  1. the imminent peak in fossil-fuel production, particularly petroleum;
  2. environmental injustice between developed and developing nations resulting from unequal access to energy resources, and from the negative effects of greenhouse gases–the preponderance of which developed nations generated–that developing nations are less able to deal with effectively; and
  3. climate forcing related to greenhouse gas emissions, which have increasingly negative, and unequal impacts on cities. Further RESUCCCITIES details are available in the SERE LAR.

Related Lab Annual Report Sections:
Goal 1, Priority 2