Atmospheres 2004 Technical Highlights: Section 5 Highlights of Laboratory for Atmosph
This section highlights the Laboratory’s accomplishments for 2004 with summaries written by the Heads, which give examples of the research carried out by scientists and engineers. Highlights are supplemented by NASA press releases in Appendix A1, by abstracts of highlighted journal articles in Appendix A2, and by a complete listing of refereed papers that appeared in print in 2004, in Appendix A3. For more details on science activities, the Web sites can be accessed from the Atmospheres home page at http://atmospheres.gsfc.nasa.gov/.
The Mesoscale Atmospheric Processes seeks to understand the contributions of mesoscale atmospheric processes to the global climate system. Research is conducted on the physical and dynamical properties, structure and evolution of meteorological phenomena ranging from synoptic scale down to microscales, with a strong focus on the initiation, development, and effects of cloud systems. A major emphasis is placed on understanding energy exchange and conversion mechanisms; especially cloud microphysical development and latent heat release associated with atmospheric motions. The research is inherently focused on defining the atmospheric component of the global hydrologic cycle, especially precipitation, and its interaction with other components of the Earth system. Members participate in satellite missions and develop advanced remote sensing technology with strengths in the active remote sensing of aerosols, water vapor, winds, and convective and cirrus clouds. There are also strong research activities in cloud system modeling, and in the analysis, application, and visualization of a great variety of data.
Scientists develop retrieval techniques to estimate precipitation using satellite observations from TRMM and other satellites such as GOES and the AMSR-E sensor on EOS Aqua. There were many notable accomplishments in 2004: provision of 3-hourly near-global rainfall fields in near-real time, studies of African easterly waves, publication of an effective El Niño predictor, and application of TRMM data to study the urban heat island effect, and effects of Amazon deforestation. The TRMM Ground Validation team processes and applies data from rain gauge networks, and ground-based radars. TRMM and other precipitation data are used for a wide spectrum of studies on precipitating cloud systems and the global water cycle. Increasingly, these activities integrate global or regional data sets with modeling. Research is conducted on the assimilation of TRMM observations into models to explore the potential benefits to weather forecasting, such as for hurricanes, and to improve understanding of precipitating cloud systems. Scientists are also an integral part of the developing Global Precipitation Measurement (GPM) mission, presently in the formulation phase. GPM seeks to establish an international calibrated satellite network for high-resolution (space and time) global precipitation measurements.
Development of lidar technology and application of lidar data for atmospheric measurements are also key areas of research. Systems have been developed to characterize the vertical profile structure of cloud systems (CPL), atmospheric aerosols (MPL), water vapor (SRL), and winds (GLOW) at fine temporal and/or spatial resolution from ground-based or airborne platforms. In addition, the Cloud Radar System (CRS), a millimeter-wavelength radar for profiling cloud systems has been developed and integrated on NASA’s high altitude ER-2 research aircraft for use in sensing the microphysical properties of cirrus and other cloud types, and complements the existing ER-2 Doppler (EDOP) radar that has been extensively used to study precipitating cloud systems.
Of particular note in 2004, was the publication of new techniques to derive atmospheric temperature profiles, aerosol size distributions, and cirrus ice water content all from Raman lidar observations. In addition, analysis of Raman lidar observations provided useful guidance for key assumptions made in deriving cirrus optical properties using more conventional elastic cloud lidar measurements, such as used in retrievals from MPL, CPL, GLAS, and CALIPSO observations. Results from a first CloudSat-CALIPSO-Aqua/MODIS (A-Train simulator) analysis based on data obtained during the 2002 CRYSTAL-Florida Area Cirrus Experiment (CPL, CRS, and MAS on NASA ER-2) provided unique insights into the data that will be obtained once CloudSat and CALIPSO are launched in 2005. Studies using MPL measurements of aerosol (pollution) and transport (ACE-Asia and Canadian forest fires) were also published and illustrate the significant intercontinental connections that exist on this planet. Major efforts are underway to expand MPLNET from its present 5 sites to 15 sites around the globe in the next two years. An MPL was deployed to the United Arab Emirates for an aerosol experiment; and CPL, newly integrated on NASA’s high-altitude WB-57F aircraft, was flown in the first Aura Validation Experiment over the Gulf of Mexico. Work continues to complete development of compact lightweight CPL and CRS instruments for use in future missions using high-altitude unmanned aerial vehicles (UAVs).
Scientists developed atmosphere-sensing capabilities of the Geoscience Laser Altimeter System (GLAS) that was launched on ICESat early in 2003. GLAS is used to profile the vertical distributions of cloud and aerosol layers. Analysis of the data from this exciting new mission is ongoing and many conference presentations of early results were given in 2004. Scientists serve as Project Scientists for the CALIPSO (lidar), and CloudSat (millimeter-radar) missions, which are planned for launch in 2005. The staff also organized and hosted the First International Raman Lidar Techniques Workshop, which attracted more than 90 registrants from 21 countries. This workshop sought to enhance the exchange of ideas, knowledge, and practices within the worldwide Raman lidar science community.
Cloud-resolving (Goddard Cumulus Ensemble, GCE) and mesoscale (MM5 and WRF) models are used in investigations of the dynamic and thermodynamic processes associated with tropical and extratropical cyclones and rainbands, and tropical and midlatitude deep convective systems. The models are also used to research cloud–chemistry interactions, stratospheric–tropospheric interactions, aerosol effects on clouds and precipitation, and the effects of the ocean surface (sea surface temperature) and land surface (vegetation and soil moisture) on atmospheric convection and weather systems. Other important applications include assessment of the potential benefits of assimilating satellite-derived water vapor and precipitation fields on simulations and forecasting of tropical and extra-tropical regional-scale weather systems (i.e., hurricanes and cyclones). Long-term integrations of the models are used to investigate climate feedback mechanisms, such as cloud–radiation interactions. The simulations provide a basis for integrated system-wide assessment of important factors, such as surface energy and radiative exchange processes, and diabatic heating and water budgets associated with tropical and midlatitude weather systems. The models are also used to develop retrieval algorithms. For example, the GCE model provides TRMM investigators with four-dimensional data sets for developing and improving TRMM rainfall and latent heating retrieval algorithms.
A highlight for 2004 was the publication of a unified analysis of GCE simulations of well-observed deep convective cloud systems from various field experiments. The analyses quantify and compare the atmospheric energy budget and precipitation efficiency of these systems. Significant improvements were made to GCE including implementation of message passing interface (MPI) to enable application on massively parallel state-of-the-art large-scale computers with excellent performance. A land surface model and a land information system were also implemented in the 3-D and MPI version of the GCE model; GCE has now been coupled to the Goddard finite volume global circulation model (fvGCM) as a super-parameterization within a Multi-scale Modeling Framework. A land surface model was also configured to represent urban processes and to use, for the first time, a unique tiling capability to properly characterize the heterogeneity of land surfaces when coupled with the most recent MM5 model. This framework provides a mechanism for investigating the impact of land use and land cover change (e.g., deforestation and urbanization) on mesoscale water cycle processes.
Scientists actively participated in international model comparison and evaluation activities of the GEWEX Cloud System Study for the purpose of increasing confidence in the cloud-resolving models and facilitating research on the development and testing of cloud parameterizations used in large-scale climate and forecast models (GCMs).
The staff has developed a world-class visualization lab that is used in high profile settings to reach out to scientists and, very importantly, to citizens and government organizations to stimulate understanding and support of NASA’s Earth Science Enterprise and its missions. The TRMM Outreach Office, the EOS Project Science Office, Earth Sciences Directorate, and the NASA Earth Science Enterprise (HQ) heavily utilize these capabilities in bringing the value of NASA missions and science accomplishments to the forefront of U.S. Global Change Research.
One of the most pressing issues we face, is to understand the Earth’s climate system and how it is affected by human activities now and in the future. This has been the driving force behind many of the activities in the Climate and Radiation. We have made major scientific contributions in five key areas: hydrologic processes and climate, aerosol–climate interaction, clouds and radiation, model physics improvement, and technology development. Examples of these contributions may be found in the workshops, seminars, and the list of refereed papers in Appendix 3.
Besides scientific achievements, we have made great strides in many areas of science leadership, as well as science enabling, education, and outreach. Thanks to the organizational efforts of Yoram Kaufman and Lorraine Remer, the AeroCenter seminar series continues to remain focused on challenging unresolved issues affecting climate-aerosol interactions and is very well attended. The biweekly seminars overflow the meeting room and attract aerosol researchers from NOAA and the University of Maryland on a regular basis.
Collaborative papers between AeroCenter members from different disciplines are now commonplace. Previous AeroCenter visitors submitted papers based on the work done during their visits to Goddard. MODIS data have been used for quantitative assessment of the emission, transport, and fate of dust from Africa. The MODIS data shows, in agreement with chemical transport models, that 120 Tg of dust are deposited annually into the oceans. It also resolves an old paradox about the need of Saharan dust as the main fertilizer of the Amazon basin and the amount of dust that was calculated to arrive in the Amazon region. Evidence was found that heavy smoke in the Amazon significantly reduces formation of boundary layer cumulus clouds and can change the smoke forcing from net cooling to net warming for which a paper was published in Science.
A strong collaboration has been established with the Environmental Protection Agency (EPA) and with NASA/Langley Research Center for the purpose of air quality monitoring and forecasting. As part of NASA’s Applications effort the potential of using the MODIS aerosol products as a Decision Support Tool within the EPA’s Air Quality Decision Support System has been demonstrated. The availability of MODIS cloud and aerosol products has opened many new pathways of research in climate modeling and data assimilation in the Laboratory. In recognition of his leadership in aerosol research in 2004, Yoram Kaufman was elected a Fellow of the American Meteorological Society (AMS).
We continue to serve in key leadership positions on international programs, panels, and committees. Si-Chee Tsay leads a group of scientists from NASA and universities in initiating a new project—Biomass-burning Aerosols in SouthEast-Asia: Smoke Impact Assessment (BASE-ASIA), to study the effects of smoke aerosol on tropospheric chemistry, water, and carbon cycles, and their interactions in the Southeast Asia monsoon region, using multiplatform observations from satellites, aircraft, networks of ground-based instruments and dedicated field experiments.
Robert Cahalan serves as project scientist of SOlar Radiation and Climate Experiment (SORCE), launched in January 2003, which is measuring both Total Solar Irradiance (TSI, formerly “solar constant”) and Spectral Solar Irradiance (SSI) with unprecedented accuracy and spectral coverage (1–2000 nm for SSI, 1–100,000 nm for TSI) during a 5-year nominal mission lifetime. Cahalan is chairing the Observations Working Group of the Climate Change Science Program Office, tasked to evaluate and coordinate multiagency contributions to the U.S. Government climate observing system. He also chairs the 3-Dimensional Radiative Transfer Working Group of the International Radiation Commission and directs the International Intercomparison of 3-Dimensional Radiation Codes, as described in a paper accepted by the Bull. Amer. Meteor. Soc. In recognition of his long-standing leadership in radiative transfer during 2004, Warren J. Wiscombe of the Climate and Radiation was elected President of the Atmospheric Sciences Section of the American Geophysical Union (AGU).
The Climate and Radiation Web site (http://climate.gsfc.nasa.gov/) has a front page that changes almost daily. It provides the latest news in climate research and automatically updates the calendars of users who subscribe. Its “Image of the Week” highlights research by members, and a search page provides easy access to archived news, images, publications, and other climate information and data. The web site also has an extensive glossary of Earth science acronyms, and a list of links to related sites. The Earth Observatory Web site (http://earthobservatory.nasa.gov/) also continues to provide the science community with direct communication gateways to the latest breaking news on NASA Earth Sciences. It provides the new media and other communications outlets with a “one-stop shopping” resource for publication quality images and data visualizations from NASA Earth Science satellite missions such as Terra, Aqua, and many others. The Earth Observatory Web site now boasts over 27,000 subscribers, with roughly 1 million page views per month worldwide. The contents of the Web site are increasingly syndicated by NASA Headquarters and other public sites.
Alexander Marshak is an editor (together with A. Davis from Los Alamos) of the “Three-Dimensional Radiative Transfer for Cloudy Atmospheres” monograph being published by Springer-Verlag. He also has authored and coauthored three chapters in the book; two additional chapters were authored by R. Cahalan and W. Wiscombe.
A new method to measure aerosol absorption from space has been developed. The method measures aerosol attenuation of sun glint over the ocean to derive aerosol absorption. The method will be best applied to future satellites that can measure the same spot over the ocean at an angle at glint and at an angle off glint.
A method to simultaneously analyze measurements from a two-wavelength lidar and a passive spectroradiometer, such as MODIS, has been introduced. The MODIS data are used to constrain the lidar inversion, thus decreasing the weight of assumptions in retrieving the aerosol profiles. The method was applied to Saharan dust and smoke from Africa in two field experiments.
There has been substantial progress in the area of land model development and its evaluation for more realistic representation of land–atmosphere interactions in general circulation models. Four land models that have been variously used at the Laboratory were put into the Land Information System (LIS) framework for interoperability, testing, evaluation, and intercomparisons using standard model-driving data. Two yearlong integrations with Global Soil Wetness Project (GSWP) forcing data (from analysis of observations from 1987 and 1988), have revealed several salient characteristics of different land models that will have an impact on the climate change studies. We are well on our way to use the outcome for a better land model that draws algorithms from the most realistic features of all the models. This activity is led by Yogesh Sud in collaboration with Randall Koster and his team in the GMAO, and Paul Houser and Christa Peters of Hydrological Sciences. In addition, our land model provided simulations for the study of the influence of soil moisture on seasonal precipitation published in Science. We also constructed and used a robust methodology for objective evaluation of the benefits of including a new physics package in a GCM—a daunting task with changes giving mixed plus–minus signals. The method helped to show that our cloud scheme named “McRAS” indeed outperforms the cloud scheme of the finite volume GCM, which uses NCAR cloud physics.
The second key area of climate model development is in cloud-physics. Almost all state-of-the-art models develop large simulation biases, which are often larger than the outstanding climate change issues that need to be assessed by these models. This is primarily due to the biased heating and moistening fields simulated by the model’s cloud physics. Efforts to curb such model biases continue. Yogesh Sud and Gregory Walker have determined that temperature biases near the surface of land, a feature common to most models evaluated with ARM-CART SCM data sets, are caused, in part, by patchiness of land that leads to non-uniform heating and moistening with deeper mixing of surface fluxes than those provided by uniform small-scale land conditions. Such corrections can mitigate this kind of model bias. Among other innovative modifications, are radiative and cloud-modulation effects of aerosol on cloud condensation nuclei and number of cloud drops. This work involves collaboration with Mian Chin. In addition, the work also involves parameterization of convection associated with different cloud types, and research on moist processes involving convective triggers and inhibitors, and treatment of smaller than the grid scale cloud processes with horizontal transports. We are also participating in cloud model intercomparison and improvements for the next generation of GMAO and NCAR models. This work is in collaboration with Arthur Hou of the GMAO, and Leo Donner of GFDL. William Lau of the Laboratory is strongly encouraging research on aerosol-cloud-radiation interaction. He is active in assessing the role of aerosol in providing the radiative and cloud and precipitation scale modulations using both model and satellite data. He recently led two studies on the radiative influence of aerosol on tropical circulation; of these, one will be an article in Nature.
We are evaluating coupled cloud-radiation and prognostic cloud-water schemes with in situ observations available from satellite retrievals, the ARM Cloud and Radiation Test Bed (ARM CART), and TOGA COARE IOPs. Future ARM data will provide badly needed forcing data on aerosol as well. All these data will contribute to cloud model improvements. Together, model evaluations with these testbeds have been found to better represent the hydrologic cycle in climate simulation studies. For more information, contact Yogesh Sud (Yogesh.C.Sud@nasa.gov).
5.3 Atmospheric Experiment
Atmospheric Experiment conducts experimental studies to increase our understanding of the chemical environment in our solar system during its formation and to study the physical processes that have continued to shape solar system bodies through time. To achieve this goal, the staff has a comprehensive program of experimental research, developing instruments to make detailed measurements of the chemical composition of solar system bodies such as comets, planets, and planetary satellites that can be reached by space probes or satellites.
1) Continued providing postlaunch support for the following key planetary missions:
- A Gas Chromatograph Mass Spectrometer on the Cassini/Huygens Probe mission to explore the atmosphere of the Saturn moon, Titan.
Extensive preparations have been made for the upcoming Saturn–Titan encounter. The Saturn orbit insertion occurred in July 2004. The Probe release to Titan occurred on December 25, 2004, and Probe entry into the atmosphere of Titan occurred on January 14, 2005. Existing instrument calibration facilities were prepared for pre- and post-flight calibration of the Flight Spare instrument, which is available in the Laboratory to simulate flight environments and to assist in the interpretation of the flight data. The effort is substantial because of the high complexity of the instrument and the difficulties involved in conducting in situ measurements from a fast-descending probe into an essentially unknown atmosphere.
- An Ion and Neutral Mass Spectrometer on the Cassini Orbiter to explore the upper atmosphere of Titan and the tenuous atmospheres of Saturn’s icy satellites, rings and magnetosphere.
The Ion and Neutral Mass Spectrometer (INMS) was designed, built, and calibrated for the Cassini Mission and is currently operated as a facility team instrument. Personnel participated as team members in the INMS science and operations planning in 2004. The INMS cover was jettisoned shortly after Saturn orbit insertion on July 1, 2004 and immediately began making measurements. Molecular and atomic oxygen ions, and protons were detected in the vicinity of Saturn’s A-ring. A likely explanation for these ions is solar ultraviolet photo ionization of neutral O2 molecules associated with a tenuous ring atmosphere whose lifetime is longer than that of water products, which are lost because of sticking on the ring particle surfaces.
The first high altitude passes through the atmosphere of Titan occurred on October 26 at 1174 km above the surface and on December 15 at 1198 km. The densities of molecular nitrogen and methane, the main constituents of the atmosphere, were determined and are comparable with earlier Voyager-derived values, which have also been used for lower altitude engineering studies. The homopause altitude, where the eddy diffusion coefficient because of mixing, is equal to the molecular diffusion coefficient, is high, in the 1150–1250 km region, while the exobase, where the mean free path is equal to the scale height, is low, about 1420 km. The exospheric temperature is estimated to be around 149 K, lower than Voyager-derived values.
Wave structures have been observed in the INMS molecular nitrogen data, which may help explain the high altitude extent (1200 km) of the well-mixed atmosphere of Titan. Detection of trace amounts of more complex (C2, C3, and C4) hydrocarbons and nitriles at the spacecraft altitudes support the concept of a high altitude well-mixed atmosphere. Isotopic ratio measurements of carbon and nitrogen suggest a very dense early atmosphere dominated by nitrogen derived from photo dissociation of ammonia, most of which escaped into space, leaving the substantial remnant observed today. In contrast, the methane in today’s atmosphere must be continually replaced by degassing, from an unknown source. Photochemistry of these two species produces nitriles and hydrocarbons that contribute to the formation of the aerosol layer which completely hides the surface in visible light. Measurements in this lower altitude region were made by the Cassini/Huygens Probe Gas Chromatograph Mass Spectrometer, which entered Titan’s atmosphere on January 14, 2005. The INMS will continue to make in situ measurements through the next four years as the Cassini spacecraft tours the Saturn system.
The engineering team is also participating in the flight instrument health assessment and in preparations for pre- and post-encounter laboratory calibration of an identical spare instrument. Considerable effort went into the design and construction of the molecular beam calibration system with which the environmental conditions of a Titan flyby of the Cassini Orbiter can be simulated.
2) Goddard Space Flight Center was selected to lead an international team to develop an instrument suite for the Mars Science Laboratory that will land on Mars in 2010 and operate on the surface for an entire Mars year (about two Earth years). The objective of the Mars Science Laboratory is to explore and quantitatively assess a potential habitat on Mars. The Sample Analysis at Mars (SAM) suite investigation will contribute to an assessment of the biological potential of the target environment by determining the extent and nature of organic carbon compounds and by taking an inventory of the other chemical building blocks of life such as H, N, O, P, and S. A range of isotope measurements is designed to contribute to the understanding of the long term atmosphere evolution processes that may have substantially transformed this planet over time. SAM will be able to measure the abundance and isotopic composition of the Martian atmospheric methane that has recently been discovered by remote sensing.
The SAM suite instruments selected by NASA for the Mars Science Laboratory are a mass spectrometer provided by Goddard Space Flight Center, a gas chromatograph provided by the University of Paris, and a tunable laser spectrometer provided by the Jet Propulsion Laboratory. These instruments work in concert to carry out a range of composition and isotopic analysis of gases with a special focus on a comprehensive analysis of carbon containing compounds. The instruments are supported by a chemical separation and processing laboratory developed at Goddard that releases gas from solid material and also provides gas enrichment and separation capability. Our industrial collaborator, Honeybee Robotics, provides the SAM sample manipulation system that moves small samples of Mars surface materials into their thermal processing stations. All these elements are designed to realize the goal of the SAM suite investigation to explore the potential for life on Mars.
3) Members continued to advance development in, and participated in the preparation of, NASA proposals for measurements on future planetary missions. These include (a) a probe of the deep atmosphere of Venus to carry out precision measurements of isotopes designed to resolve questions of the origin and processing of this atmosphere; (b) a detailed in situ rendezvous mission with the nucleus of a comet to better understand the complexity of organic molecules that might have been delivered to Earth over the course of its history; (c) a comet fly-by mission; and (d) a lander experiment on Mars to sample isotopes and molecules from its atmosphere and below its surface, which can address studies of past climate and the possibility of past life on this planet. A program of analysis of organics in Mars analog materials was initiated to test and validate the analytical approach.
4) The staff leads one of four themes of the recently selected Goddard node of the NASA Astrobiology Institute. As part of this activity, members participate in a collaborative astrobiology investigation with the Johns Hopkins University Applied Physics Laboratory (JHU/APL) to develop analytical protocols for in situ instruments that will aid in the evaluation of prebiotic chemistry on primitive solar system bodies, which might have contributed directly or indirectly to the emergence of life on early Earth. The approach includes analysis with a miniaturized time-of-flight mass spectrometer combined with a gas chromatograph, which will allow both simple and complex organic molecules to be resolved. Direct ionization of solid samples using laser ablation or energetic ions combined with electron ionization of gases thermally released from the same samples will allow a wide range of highly volatile-to-highly refractory components to be analyzed. This powerful technique will also enable in situ characterization of organics contained in solid phase material from the Jovian moons, or Mars.
5) Members continued the collaborative effort with the GSFC Engineering Directorate in a program to achieve a significant reduction in the size and weight of present-day mass spectrometer systems. This includes reduction of the electronics system by using Application Specific Integrated Circuits (ASICS) and other advanced packaging techniques, as well as reductions to the mass spectrometer itself by using Micro-Electrical Mechanical Systems (MEMS) techniques.
Atmospheric Chemistry and Dynamics develops computer models and remote sensing instruments and techniques, as aids in studies of aerosol, ozone, and other trace gases that affect chemistry, climate, and air quality on Earth. This is a world-class center of research in stratospheric chemistry. Using satellite, aircraft, balloon, and ground-based measurements coupled with data analysis and modeling, scientists have played a key role in improving our understanding of how human-made chemicals affect the stratospheric ozone layer.
Scientists have been active participants in satellite research projects. In the late 1960s, our scientists pioneered development of the backscattered ultraviolet (BUV) satellite remote sensing technique. Applying this technique to data taken from NASA and NOAA satellites, scientists have produced a unique long-term record of the Earth’s ozone shield. The data record now spans more than three decades, and provides to scientists worldwide, valuable information about the complex influences of Sun, climate, and weather on ozone and ultraviolet radiation reaching the ground. Scientists expect to maintain this venerable record using data from a series of BUV instruments that are planned for use on U.S. and international satellites in the next two decades. Scientists were also instrumental in developing the Upper Atmosphere Research Satellite (UARS) project, which generated data used by researchers to produce a highly detailed view of the chemistry and dynamics of the stratosphere. Currently, scientists are providing scientific leadership for the EOS Aura satellite, which was launched on July 15, 2004. Aura contains four advanced instruments to study the stratospheric ozone layer, chemistry and climate interactions, and global air quality. Scientists are also involved in the design of instruments to measure tropospheric air quality and chemical species from spacecraft located at high vantage points (at distances ranging from 20,000–1,500,000 km from Earth), which may be launched in support of NASA’s new Exploration Initiative. In addition, they operate a suite of advanced lidar instruments to study the stratosphere from ground and aircraft.
The measurement activities are highly coupled with modeling and data analysis activities. The staff maintains state-of-the-art 2-D and 3-D chemistry models that use meteorological data, produced by the GMAO, to interpret global satellite and aircraft measurements of trace gases. Results of these studies are used to produce congressionally-mandated periodic international assessments of the state of the ozone layer, as well as to provide a strategic plan for guidance in developing the next generation of satellite and aircraft missions. A major new thrust is to apply the unique synergy between modeling and measurement groups, which proved very successful for the study of stratospheric chemistry, to study chemically and radiatively active tropospheric species—including aerosol, CO2, O3, CO, NOx, and SO2—which affect climate, air quality, and human health.
The following provides more detailed descriptions of some of the current activities:
1) 3-D Stratospheric Chemistry Model Studies
Several scientists are analyzing a recently completed 50-year chemical transport model simulation of stratospheric ozone chemistry. They are focusing on its comparison to long-term data records from satellites and ground-based instruments. The goal is to use the model results, combined with data, to draw inferences about long-term ozone trends and about the expectation of a decrease in stratospheric chlorine accompanied by a recovery of ozone while the Montreal Protocol is being implemented. The team has further initiated collaborative work with the GMAO to examine the sensitivity of the finite volume general circulation model dynamics to changes of the ozone climatology in the radiation code of the GCM. This work is being combined with the effort to put the full-chemistry transport model online in the GCM. This is the first step in coupling the chemistry to the dynamics for chemistry–climate studies.
GMI is a project designed to reduce uncertainty in assessment modeling by developing and maintaining state-of-the-art chemistry and transport models that are appropriate for both stratospheric and tropospheric applications. The CTM is modular so that the sensitivity of results to various CTM components can be quantified. A science team with members from government labs, universities, and the private sector contributes to the project. Scientists contribute at all levels to this project, including scientific management, experiment design, and evaluation of the GMI simulations. Susan Strahan and Anne Douglass use physically based diagnostics to evaluate the realism of the GMI stratospheric simulations. These simulations are identical except that one uses meteorological fields from the GMAO data assimilation system and the other uses meteorological fields from the general circulation model (GCM) that is used in that assimilation system. The transport produced by the GCM is more realistic, except in the upper stratosphere where horizontal transport is weak leading to lower-than-observed mixing ratios for CH4. Anne Douglass compared the same simulations with observations of radical and reservoir species with the goal of understanding the differences in simulations for 1995–2030. The ClO in the upper stratosphere is higher than observed in the simulation using GCM winds because the low CH4 noted above shifts partitioning towards ClO and away from HCl.
3) Tropospheric O3 Studies
In 2004, members developed a long record (1979–present) of tropospheric and stratospheric ozone from TOMS satellite measurements extending from the tropics to the high latitudes in both hemispheres. In a recently submitted paper to the Journal of Geophysical Research (JGR), this data set was used to determine long-term changes in ozone in both the troposphere and stratosphere. This paper discusses the important issues of stratospheric ozone recovery and the long-term increase in tropospheric ozone related to increased industrial pollution. This study indicated that ozone values over surface emission-free regions of the Atlantic and Pacific Oceans are relatively high (50–60 DU) and are comparable to industrial regions of North America, Europe, and Asia.
4) Global Transport of Aerosol
Aerosol radiative forcing is one of the largest uncertainties in assessing global climate change. To understand the various processes that control the aerosol properties and to understand the role of aerosol in atmospheric chemistry and climate, the scientists have developed the Global Ozone Chemistry Aerosols Radiation and Transport (GOCART) model. In the past few years, the GOCART model has been used to study tropospheric aerosol and its effect on air quality and climate forcing. Major types of aerosol particles are simulated, including sulfate, dust, black carbon, organic carbon, and sea salt. Among these, sulfate, and black- and organic carbon mainly originate from human activities, such as fossil fuel combustion and biomass burning. Dust and sea salt are mainly generated by natural processes such as the uplift of dust from deserts by strong winds.
The modeling activities have been strongly connected to the satellite and aircraft observations. Our recent research involves studies of intercontinental transport of dust and pollutants using a combination of models and data. The data is from satellite observations (MODIS and TOMS), ground-based network (AERONET), and in situ measurements (ACE-Asia). The aerosol absorption in the atmosphere is based on the GOCART model and AERONET data, and the aerosol radiative forcing is based on assimilated products of the model and MODIS data. In addition, the model results are used by many groups worldwide for studies of air pollution, radiation budget, tropospheric chemistry, hydrological cycles, and climate change.
Analysis of the TOMS long-term record on aerosol optical depth has detected the existence of statistically significant trends in the atmospheric aerosol load over regions of the world that have experienced substantial economic growth over the last 30 years. The TOMS aerosol record indicates that an increasing trend of 17% per decade in the winter aerosol load has taken place in the China coastal plain, while a 7% per decade trend in aerosol concentration has been observed over India. These trends in aerosol optical depth are consistent with observed increases of SO2 emissions associated with anthropogenic activities in these regions.
5) Aerosols and Their Impact on UV Radiation
Aerosol UV absorption measurements are necessary to quantify the causes of the observed discrepancy between modeled and measured UV irradiances and photolysis rates. Since 2002, scientists, the AERONET program, and the USDA UV Monitoring and Research Program (UVMRP) have shared equipment, personnel, and analysis tools to quantify aerosol absorption using ground-based radiation measurements in Greenbelt, Maryland. In 2004, a 17-month monitoring experiment was completed, where the aerosol UV absorption was inferred from the measurements of direct and diffuse atmospheric transmittances by a UV-Multifilter Rotating Shadowband radiometer (UV-MFRSR) combined with ancillary measurements of aerosol particle size distribution and refractive index in the visible wavelengths (by CIMEL sun–sky radiometers), column ozone, surface pressure, and surface albedo. Combining these measurements with a Radiative Transfer model, the seasonal dependence of the aerosol absorption optical thickness, tabs, was derived for the first time in the UV wavelengths. The tabs had a pronounced seasonal dependence with maximum values of ~0.1 occurring in summer hazy conditions and <0.02 in the boreal winter–fall seasons, when aerosol loadings are small. The measured tabs was sufficient to explain both the magnitude and seasonal dependence of the bias in satellite estimates of surface UV irradiance previously seen with ground-based UV measurements.
6) Measurement and Modeling of Atmospheric Carbon Dioxide
Recent Laboratory progress in carbon cycle science has come in the areas of atmospheric transport modeling and instrument construction and testing. The atmospheric chemistry and transport model, used for calculating global CO2 transport, is incorporating a land biosphere model, high temporal resolution fossil fuel emissions, and satellite data-constrained biomass burning emissions to produce CO2 fields, which are closely tied to actual meteorology and emission events. These distributions will be compared with real-time CO2 observations to improve our knowledge of the coupling between carbon cycle processes and climate change.
A Fabry–Perot Interferometer, to measure column CO2, has been assembled and flight tested in California on the NASA DC-8 aircraft. Results indicate that the instrument has sufficient sensitivity to measure CO2 at high precision. In addition, integrated horizontal path measurements (400 m) of CO2 have been made with a lidar at 1.57 µ and tracked the diurnal changes observed by a collocated in situ instrument (Licor) over 24 h. A high-speed photon counting system suitable for making range-resolved measurements of CO2 within the planetary boundary layer (PBL) has been assembled and tested. An EDFA fiber amplifier with 2% duty cycle, 100-ns pulses and 300 mW average power has been fully characterized and is being integrated with the counting system for preliminary testing. Initial efforts are being directed towards integrated CO2 column measurements using cloud bases for the signal source and nighttime CO2 profiling within the PBL at very high resolution using boundary layer aerosols. The instrument’s range resolution will vary from 15–150 m and the initial measurement precision will be several parts per million by volume (ppmv).
7) Sun–Earth Connection Studies
Members were involved in several investigations into the influence of the Sun on the Earth’s atmosphere. One current study involves the effect of the very large solar storms in October–November 2003 on the middle atmosphere. These solar storms resulted in solar proton events at the Earth that created HOx (H, OH, HO2) and NOx (N, NO, NO2), which depleted ozone. The solar proton event of October 28–31, 2003 was the fourth largest of the past 40 years and caused huge NOx enhancements measured by the HALOE instrument and significant ozone depletions measured by the SBUV/2 instrument in the middle atmosphere.
It has been previously suggested, based on empirical correlations, that solar cycle affects the waves that drive the Quasi-biennial Oscillation (QBO) at low latitudes. The scientists had partially modeled this effect using a 2-D model. Recent results using 3-D models show the solar cycle caused large variations in the QBO of the lower stratosphere in low latitudes, as well as variations in tropospheric temperatures in high latitudes. Further work is necessary to establish the mechanism and robustness of these results.
8) New Instrument Development
Two new instruments are being developed under the Instrument Incubator Program (IIP), the Solar Viewing Interferometer Prototype (SVIP) and the GeoSpec (Geostationary Spectrograph). The SVIP is a 1–2 µ prototype of an instrument that will make measurements at 1–2 µ to determine the amounts of CO2, H2O, O3, N2O, and CH4 in the Earth’s atmosphere from a position at L2. The SVIP is designed for testing in the laboratory, outside at Goddard, and on a mountaintop. The GeoSpec is a dual spectrograph operating in the UV/VIS and VIS/NIR wavelength regions to measure trace gas concentrations of O3, NO2, and SO2, coastal and ocean pollution events, tidal effects, and aerosol plumes. GeoSpec is intended to support future missions in the combined fields of atmospheres, oceans, and land. GeoSpec is a collaboration of our Laboratory, Pennsylvania State University, Washington State University, and Research Support Instruments. GeoSpec activities during the current year included final optical prescription and mechanical design, detector procurement, and breadboard assembly plans. Initial testing of the prototype instrument is planned for spring 2005 with validation deployment during the summer at Washington State University.
5.5 Science Highlight Articles
This section presents short science highlights representing a snapshot of the Laboratory’s activities.
GLAS Sheds New Light on Global Clouds and Aerosol (by James Spinhirne of the Atmospherics Lidar Group)
The Geoscience Laser Altimeter System (GLAS) developed by GSFC was launched in 2003. In 2004, the first data results were presented and made available to the outside science community. GLAS gives the first global profiling from an active laser remote sensing instrument in space, providing fundamentally new measurements for atmospheric research. The GLAS atmospheric group completed and delivered the operational algorithms for data products for the mission. The results show that a very accurate, new measurement of the coverage and height distribution of global cloud cover is being made. GLAS has found that the actual coverage of the globe by clouds is 70%, of which 45% are single layered within the limits of optical attenuation, and a very surprising 76% of clouds are sufficient to block the optical surface return. The results have also shown significant limitations in the passive satellite data on polar cloudiness. Another important new result is the first global measurements and maps of boundary layer aerosol optical depth and the height of the PBL. The PBL measurements are part of the broader frame of the first global measurements of the true height distribution of global aerosol layers. From these and other applications, the GLAS measurements represent an important new tool for Earth science and global change research.
Totally unique in the GLAS data is the accuracy of the height measurement and the ability to clearly distinguish cloud, aerosol and surface-scattering signals. The GLAS measurements provide the capability to resolve atmosphere-scattering layers from resolutions below 100 m to globally girded data results. Examples of these unique and new measurements are shown in Figures 5-2 and 5-3. The GLAS measurements give atmospheric scientists a new view on the world.
Center for Aerosol Research at the NASA Goddard Space Flight Center (by Lorraine Remer of the AeroCenter)
AeroCenter is one of the five crosscutting themes of the Earth Science Directorate and an interdisciplinary union of GSFC researchers who are interested in many facets of atmospheric aerosols. Yoram Kaufman heads AeroCenter with the current steering committee composed of Mian Chin, Oleg Dubovik, Charles Ichoku, Judd Welton, and Lorraine Remer. Interests include observations of aerosols from space, aircraft and the ground, aerosol effects on clouds, precipitation, rainfall, climate and the biosphere, aerosols and radiative transfer, the aerosol role in air quality and human health, and the atmospheric correction of aerosol blurring of satellite imagery of the ground.
AeroCenter recognizes that GSFC has a unique role in worldwide aerosol research in terms of the depth and breadth of the work undertaken. Established aerosol research at Goddard includes the AERONET group, the lidar group, the MODIS aerosol group, the TOMS aerosol group, SeaWiFS atmospheric correction, MODIS atmospheric correction , Landsat atmospheric correction, the SMART observation system, Air Quality applications, GMAO aerosol assimilation, chemical transport modeling, cloud-aerosol interaction modeling, and climate modeling. In addition, the Goddard DAAC is responsible for the dissemination of a great quantity of EOS data including MODIS aerosol products. This wealth of resources is spread out over many divergent disciplines and organizations. Before AeroCenter, Goddard aerosol researchers were more likely to meet and talk at a conference in another city than in the hallways of their own building. One of the underlying reasons for AeroCenter’s genesis was to provide a fast track for newcomers so that they could become aware of the aerosol work happening beyond the walls of their own little cubicle.
The history of AeroCenter began with the EOS era and the launch of the Terra satellite. The new satellite products, soon to become available, would bring unprecedented aerosol information to the world. However, these new products would also swamp the average researcher with information. We searched for a way to make the data more accessible, involve more people in using the products, and increase our overall understanding of the science that involves aerosols. We started with support from NASA Headquarters and some seed money for a three-prong strategy: (a) develop Web tools to make the data more accessible; (b) create a visitors program to bring both senior scientists and student researchers to GSFC for training and collaboration; and (c) enhance collaborative efforts of the research currently in progress at GSFC.
a) The MOVAS Web site (http://lake.nascom.nasa.gov/movas/) developed by the Goddard DAAC in conjunction with AeroCenter allows easy access of a limited set of MODIS aerosol and cloud products using interactive maps and graphics. Researchers can access products, produce regional or temporal subsets, Hovmoller diagrams or time series plots, and download ASCII files. Recent additions to the site in 2004 include parameter comparison capabilities. Soon, global data sets from models will be available on this site as well.
b) The visitor program brought researchers from all over the world to Goddard for a few weeks to several months. Unfortunately, NASA Headquarters has discontinued funding for this program, and thus, we suspended the AeroCenter visiting scientist program in 2004.
c) The most visible success of AeroCenter is the increased collaboration within Goddard’s own aerosol community. The biweekly seminar series that continues with enthusiastic response both from speakers who wish to give a seminar and an eager audience that actively engages in discussion. The annual winter poster session is a highlight of the AeroCenter year, as is the annual aerosol update that is organized to keep the Directorate informed on the progress of Goddard’s aerosol research. The AeroCenter seminars and annual updates are widely attended, not just by GSFC researchers, but also by local colleagues from the University of Maryland and NOAA. Since AeroCenter began, the number of collaborative papers and proposals written and submitted that involve authors across organizational codes within GSFC, agencies, and universities has increased dramatically. The AeroCenter Web site (http://aerocenter.gsfc.nasa.gov) will soon be updated to become a source of internal information and enhance the feeling of community that AeroCenter members enjoy.
AeroCenter recognizes that GSFC is a Center of Excellence in aerosol research. The combination of expertise in observations, modeling and applications available within AeroCenter, and the type of collaboration that AeroCenter fosters will be necessary to firmly define the role of aerosols in climate change, weather modification, air quality and other applications.
For further information on the AeroCenter, contact Lorraine Remer (Lorraine.A.Remer@nasa.gov).
High Resolution finite volume General Circulation Model (fvGCM) (by Robert Atlas and Oreste Reale)
The finite-volume General Circulation Model (fvGCM), resulting from a development effort of more than ten years, has been brought to the resolution of a quarter of a degree as a part of the ALTIX computing project. The model is based on a finite-volume dynamical core with terrain-following Lagrangian control-volume discretization. The capability of running in real time at such high resolution, which is double the resolution currently adopted by most global models in operational weather centers, has been made possible thanks to a crucial aspect of the fvGCM development: its high computational efficiency, resulting from a careful design aimed to optimize performance on a variety of computational platforms including distributed memory, shared memory and hybrid architectures. Such high global resolution has brought NASA closer to overcoming a fundamental barrier in global atmospheric modeling for both weather and climate, because convection and tropical cyclones can be more realistically represented.
During the 2004 hurricane season, the model was run daily in real-time, and also simulations of the past hurricane seasons 2002 and 2003 have been made. Selected simulations of several Atlantic tropical cyclones, chosen because of varied difficulties presented to numerical weather forecasting, have been analyzed. The fvGCM has produced very good forecasts and simulations of several of these tropical systems, adequately resolving problems like erratic track, abrupt recurvature, intense extra-tropical transition, multiple landfall and reintensification, and interaction among vortices. The most important achievement of the high-resolution fvGCM, however, is probably the increase in intensity and the realism of hurricanes’ vertical structure. Figure 5-4 shows the sea level pressure for Hurricane Isidore (2002) from a 60-h fvGCM forecast relative to the National Center for Environmental Prediction (NCEP) analysis for this time. The coarser resolution analysis is not able to represent Isidore’s intensity but provides an indication of Isidore’s position. In spite of a less-than-satisfactory initialization (due to much lower resolution of the initial conditions), the dynamical core of the fvGCM can produce a minimum of approximately 960 hPa in the 60-h forecast for 1200 UTC 22 September. The observed minimum center pressure is 934 hPa at this time. The observed and simulated change in intensity between 0000 UTC 20 September and 1200 UTC 22 September are both of the order of 40 hPa. Therefore, it can be anticipated that with improved initial conditions the fvGCM could produce an even deeper vortex. In the lower panels of the accompanying figure, the zonal and meridional vertical cross-sections of wind speed, relative vorticity and temperature, are shown, for the 60-h fvGVM forecast for the same time (1200 UTC 22 September). All the prominent features of observed hurricanes can be seen: a vertical column of low speed, a prominent warm-core, an intense gradient of cyclonic vorticity away from the eye, wind and cyclonic vorticity maxima in the lower levels, and a hint of anticyclonic vorticity in the higher levels. Lower resolution GCMs may produce some of these features, but the radius of maximum wind is of the order of 2–300 km (whereas in our runs, it is of less than 100 km) and the vorticity maxima tend to be weaker and located at excessive altitude.
Aura Highlights (by Anne Douglass and Richard Stewart)
The Aura satellite was launched from Vandenberg Air Force Base on July 15, 2004. Aura is designed to study the Earth’s ozone, air quality, and climate and carries a suite of four instruments to accomplish this task. The instruments are the High Resolution Dynamics Limb Sounder (HIRDLS), Microwave Limb Sounder (MLS), Ozone Monitoring Instrument (OMI), and Tropospheric Emission Spectrometer (TES).
Initial results from Aura show that it is fulfilling its promise to provide comprehensive information about the troposphere and lower stratosphere. The following short paragraphs highlight some of the preliminary results from the three working instruments.
Microwave Limb Sounder
The suite of constituents observed by MLS will improve our understanding of the chemistry of the lower stratosphere and upper troposphere. MLS has already provided a comprehensive set of measurements of species related to Arctic ozone loss. The measurements in Figure 5-5 include nitric acid and water, both important for formation of polar stratospheric clouds (PSCs), as well as maps of hydrochloric acid, a reservoir for reactive chlorine, and the radical chlorine monoxide, which is released from the reservoir through reactions involving PSCs. These observations and those made in the Arctic will be used to evaluate the potential for severe loss of Arctic ozone during the next few decades when the abundance of stratospheric chlorine will still be high, and even slight cooling of the stratosphere could exacerbate ozone loss because of chlorine chemistry.
Ozone Monitoring Instrument
The OMI instrument will continue the Earth Probe Total Ozone Mapping Spectrometer (EP-TOMS) record for total ozone in addition to measuring other atmospheric parameters related to ozone chemistry and climate. OMI has excellent horizontal resolution and gathered four times more data about the 2004 ozone hole (Figure 5-6) than its TOMS predecessor.
Tropospheric Emission Spectrometer
TES employs both the natural thermal emission of the surface and atmosphere and reflected sunlight, thereby providing day-night coverage anywhere on the globe. Observations from TES will further understanding of long-term variations in the quantity, distribution, and mixing of minor gases in the troposphere, including sources, sinks, troposphere-stratosphere exchange, and the resulting effects on climate and the biosphere.
The TES instrument is providing the first direct measurements of ozone in the troposphere (Figure 5-7). Maps of upper and lower tropospheric ozone shown in the following figure will be used with simulations to evaluate the effects of biomass burning and other continental sources of pollution on our atmosphere and climate. The initial maps already show that ozone pollution spreads beyond continental boundaries and is a global problem.