Investigating the Interactions of the Atmosphere, the Broader Earth System and Human Society

Developing a fuller understanding of the complex interactions among the Earth’s atmosphere, oceans, land masses, ice masses, and biosphere; the interconnection of human activities with the Earth’s physical, chemical, and biological processes is a major focus of our national center.  EOL is tasked mainly with the mission to develop innovative instrumentation and data acquisition technology and lead scientific campaigns that make such understanding possible.  Even so, EOL scientists often find themselves in the thick of data analysis that contribute directly to the goal of improving our understanding of the atmosphere and earth system, specifically by investigating the interactions of the atmosphere and the broader earth system. In FY 2006, EOL staff participated in studies of formaldehyde and its role in ozone formation, the carbon cycle (in support of NCAR’s Biogeochemistry Initiative) the NCAR Water Cycle Initiative, and thunderstorm formation studies in support of the US Weather Research Program.

• Formaldehyde in Ozone Formation [Highlight]
• Biogeochemistry Initiative
• Water Cycle Initiative
• US Weather Research Program
• RICO Analysis

Formaldehyde in Ozone Formation [Highlight]

	Schematic of DFG absorption spectrometer mounted to multipass Herriott cell that was deployed dring INTEX-B, and MIRAGE and TexAQS and gave fast and accurate measurements of formaldehyde in the atmosphere. The system could revolutionize trace gas measurements: It is lighter in weight, smaller and does not require liquid nitrogen.

Understanding formaldehyde is critical to understanding the formation of ozone, which has a variety of impacts on human health. For example, at ground level, ozone is a pollutant with harmful effects to the human respiratory system as well as injurious to various plants, yet in the upper atmosphere it is critical in blocking damaging ultraviolet light reaching the surface.  In support of NCAR's priority to investigate interactions of the atmosphere and the earth system, EOL has participated in a variety of activities in FY 2006 to enhance our scientific understanding of such atmospheric chemical transport and transformations as well as improve our knowledge of emission inventories.

EOL scientists successfully employed advanced optical instruments, including the DFG Absorption Spectrometer, to acquire fast and accurate measurements of formaldehyde during three separate campaigns: the NASA-sponsored Intercontinental Chemical Transport Experiment-Phase B (INTEX-B) on the NASA DC-8 airplane; the Megacity Impacts on Regional and Global Environments-Mexico City case study (MIRAGE-MEX) on the NCAR C-130 airplane; and the 2006 Texas Air Quality Study (TexAQS) on the NOAA WP-3 airplane. In addition, these personnel were involved in the data analysis and interpretation from the 2004 INTEX-A study.

Data processing, quality control, archival, and interpretation and analysis will continue to be carried out on the data sets acquired during the three airborne campaigns this past year. In this process, the high quality measurements of formaldehyde on these campaigns will be finalized with uncertainties and this will be followed by the data integration into larger merged databases. These deliverables will be accomplished in the middle of FY 2007. Once accomplished, the data will be interpreted, and employed in measurement-model comparisons to improve our atmospheric simulations, knowledge of oxidation processes, and understanding of the Earth system.

These efforts will be carried out throughout FY 2007 and into FY 2008, and the findings will ultimately be released to the broader scientific community through refereed publications and various talks at international meetings and workshops. The analysis of the INTEX-A campaign will be completed in FY 2007, and like the analysis of the newly acquired data sets in 2006 will be published in a refereed journal.

Biogeochemistry Initiative

Carbon Dioxide (CO2) plays an important role in supporting life on Earth, and understanding the carbon cycle is critical to our ability to predict and prepare for climate change. EOL continues to make significant contributions towards advancing our understanding of global biogeochemical cycling and supporting the biogeosciences research community through collaborations with NCAR's Earth System Science Laboratory's (ESSL's) TIIMES (The Institute for Integrative and Multidisciplinary Earth Studies). 

In FY06, EOL retained a strong focus on carbon exchange in western United States forests through the Carbon in the Mountains Experiment. Efforts to process and analyze data from intensive airborne (ACME ‘04) and ground-based campaigns have revealed insights into the critical roles spring-time interactions with the water cycle play in the annual carbon balance of these ecosystems.  Work in the past year has also included planning for a second intensive campaign in FY07 and an expansion of the in situ CO2 observing network as a key contribution to the multi-agency North American Carbon Program (NACP). EOL scientists have completed an analysis of light-aircraft vertical CO2 profiles measured at 12 global sites by 6 international laboratories.  The results revealed systematic biases in atmospheric models that predict large northern terrestrial CO2 uptake and large tropical CO2 releases, suggesting a significant revision to the consensus view of the global carbon cycle.

EOL will collaborate in FY07 with investigators at CU, CSU, and Harvard to plan and conduct the ACME ’07 campaign on the University of Wyoming King Air.  This campaign will be the second Airborne Carbon in the Mountains Campaign, focusing on Colorado and Wyoming, and will include flights from early spring through fall.  The payload will include the RAF community oxygen instrument to be completed this fall.

Water Cycle Initiative

Adequate supplies of water are critical to human survival, yet many aspects of the Earth's water cycle are not well understood. Although there is observational evidence that the water cycle is changing, numerical models of weather and climate, and both long-and short-term projections of precipitation are notably weak. EOL continues to support NCAR's response to national and international needs for better information regarding changes in the water cycle by gleaning global, 2-hourly data sets from GPS measurements and by researching the diurnal cycle of precipitation over continents.

A Global, 2-Hourly Atmospheric Precipitable Water Dataset from GPS Measurements

Water vapor plays a central role in atmospheric radiation, the hydrological cycle and in understanding and predicting global climate change. It is therefore critical to advance the understanding of water vapor variability and change, but such advancement is hampered by inadequate observations. Several studies and reports have called for creating global water vapor datasets with sufficient accuracy and temporal resolution, and more importantly long-term stability. None of existing radiosonde, satellite or blended datasets can meet the requirements for the new water vapor datasets. But since global GPS measurements of atmospheric precipitable water (PW) can meet all of these requirements with great accuracy, it can be considered as a calibration standard to validate other measurements. EOL's efforts have been to take advantage of the growing network of global GPS stations to create a global GPS-derived PW dataset, something that has not yet been done.

EOL has contributed to NCAR's efforts to advance our understanding of this aspect of atmospheric interactions by producing a global, 10-year (1997-2006), 2-hourly data set of atmospheric precipitable water (PW) from ground-based Global Positioning System (GPS) measurements of zenith tropospheric delay (ZTD). An analysis technique was developed to convert ZTD to PW and was validated by comparing radiosonde and microwave radiometer data around the globe. The PW data are available every two hours at about 350 International GPS Service (IGS) ground stations from 1997 to 2006. The PW dataset is validated by comparing with radiosonde, microwave radiometer, and satellite data, and comparisons show no systematic bias in the GPS dataset.

The analysis technique, dataset and validations will be published in the Journal of Geophysical Research in 2007. The dataset will be continually to be updated as ZTD data become available. EOL scientists are searching for GPS ZTD products from non-IGS regional networks, such U.S.A., Japan, and Korea, and process and add the data to our global PW dataset to increase the spatial coverage.

Monitoring the quality of global radiosonde humidity record using ground-based GPS measurements

Global radiosonde data represent an increasingly valuable resource for studies of climate change. Unfortunately, the usefulness of radiosonde data for long-term climate monitoring is limited by errors and biases associated with instrument and data processing procedures and by radiosonde changes among stations and with time. EOL scientists analyzed these biases in an effort to improve the long-term radiosonde climate records.  They were are able to take advantage of the increasing volume and maturity of GPS data as well as  its long-term stability to monitor the quality of global radiosonde.

They began by searching for locations where radiosonde and GPS stations were within 50 km in distance and within 100 m in elevation. When they compared the 102 such stations they found all over the globe, they discovered systematic and significant biases in three widely-used radiosonde types, dry biases in Vaisala sondes (both RS80 and RS90) and wet biases in MRZ and IM-MK3 radiosondes.  In FY 2007, they will prepare a journal article to summarize their comparisons of these measurements to clarify the usefulness of ground-based GPS PW data on monitoring the quality of global radiosonde humidity data.

US Weather Research Program

Data taken during IHOP_2002 on 12 June 2002 shows severe thunderstorms form near an intersection between a dryline and warm front. Internal gravity waves, horizontal convective rolls and a mesolow were also affecting the pre-convective region. Observational analyses suggest that the mesolow, dryline and warm front created a large area of enhanced convergence while the horizontal convective rolls provided the necessary trigger for thunderstorm development.

During FY2006, EOL scientists worked towards the US Weather Research Program’s (USWRP) objectives of improving short-term weather forecasts by analyzing a convection initiation case study of 12 June 2002 from the International H2O Project (IHOP_2002). This is a collaboration with UCLA, CNRS (France) and NWS, Indianapolis, and a manuscript for Monthly Weather Review will be published in FY 2007. 

Also under the USWRP program, EOL scientists are analyzing early morning data from IHOP to better understand the moisture evolution and distribution during the development of the daytime convective boundary layer. This is a collaboration with U. Leeds (UK), CNRS (France), DLR (Germany), U. Wyoming and Penn State and was presented as a conference preprint at the European Radar Conference in Barcelona in September, 2006. In March 2007 we will submit one or two manuscripts to the Monthly Weather Review special issue on Boundary Layer Processes.

Radar data assimilation has been shown to be effective for improving numerical forecasts of convective precipitation. In support of the USWPR in 2007 EOL plans to make EOL radar data easier for the data assimilation community to use by creating a quality-controlled dataset. We will automate a procedure to remove radar artifacts (e.g., velocity aliasing, ground clutter and second-trip echoes) and will thus provide a dataset that may be more readily ingested into data assimilation schemes. This work will be conducted in collaboration with the Short-Term Explicit Prediction (STEP) program with the goal of helping to improve short-term forecasts of convection initiation and evolution.

RICO Analysis

EOL scientists are participating in the analysis of RICO (Rain in Cumulus Over the Ocean) data.  RICO was an intensive study of rain formation process in trade wind cumulus, using S-POL, the C130 and several other observing platforms. The initial results from the analyses were presented at the recent AMS Conference on Cloud Physics.  These results include studies of the affects of giant nuclei on rain formation, studies of the nature of the updrafts in RICO clouds and their relationship to the cloud microphysics, studies of the characteristics of the RICO aerosol, and studies of the uses of trace gases and thermodynamic variables to understand mixing and entrainment processes. In FY07, EOL scientists will develop and submit peer-reviewed papers on the results of these analyses.