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We report on 10 yr of airborne measurements of atmospheric CO2 mole fraction from continuous and flask systems, collected between 2002 and 2012 over the Atmospheric Radiation Measurement Program Climate Research Facility in the US Southern Great Plains (SGP). These observations were designed to quantify trends and variability in atmospheric mole fraction of CO2 and other greenhouse gases with the precision and accuracy needed to evaluate ground-based and satellite-based column CO2 estimates, test forward and inverse models, and help with the interpretation of ground-based CO2 mole-fraction measurements. During flights, we measured CO2 and meteorological data continuously and collected flasks for a rich suite of additional gases: CO2, CO, CH4, N2O, 13CO2, carbonyl sulfide (COS), and trace hydrocarbon species. These measurements were collected approximately twice per week by small aircraft (Cessna 172 initially, then Cessna 206) on a series of horizontal legs ranging in altitude from 460m to 5500ma.m.s.l. Since the beginning of the program, more than 400 continuous CO2 vertical profiles have been collected (2007-2012), along with about 330 profiles from NOAA/ESRL 12-flask (2006-2012) and 284 from NOAA/ESRL 2-flask (2002- 2006) packages for carbon cycle gases and isotopes. Averaged over the entire record, there were no systematic differences between the continuous and flask CO2 observations when they were sampling the same air, i.e., over the oneminute flask-sampling time. Using multiple technologies (a flask sampler and two continuous analyzers), we documented a mean difference of <0.2 ppm between instruments. However, flask data were not equivalent in all regards; horizontal variability in CO2 mole fraction within the 5-10 min legs sometimes resulted in significant differences between flask and continuous measurement values for those legs, and the information contained in fine-scale variability about atmospheric transport was not captured by flask-based observations. The CO2 mole fraction trend at 3000ma.m.s.l. was 1.91 ppm yr-1 between 2008 and 2010, very close to the concurrent trend at Mauna Loa of 1.95 ppm yr-1. The seasonal amplitude of CO2 mole fraction in the free troposphere (FT) was half that in the planetary boundary layer (PBL) (∼15 ppm vs. ∼30 ppm) and twice that at Mauna Loa (approximately 8 ppm). The CO2 horizontal variability was up to 10 ppm in the PBL and less than 1 ppm at the top of the vertical profiles in the FT. [ABSTRACT FROM AUTHOR]

The article presents a study on a 10-year airborne measurements of atmospheric carbon dioxide (CO2) concentrations from continuous and flask systems collected between 2002 and 2012 over the Atmospheric Radiation Measurement Program Climate Research Facility in the U.S. Southern Great Plains (SGP). The study uses estimation theory and inverse models. Results show there were no systematic differences between the continuous and flask observations during air sampling.

An increase in photosynthetic activity of the northern hemisphere terrestrial vegetation, as derived from satellite observations, has been reported in previous studies. The amplitude of the seasonal cycle of the annually detrended atmospheric CO2 in the northern hemisphere (an indicator of biospheric activity) also increased during that period. We found, by analyzing the annually detrended CO2 record by season, that early summer (June) CO2 concentrations indeed decreased from 1985 to 1991, and they have continued to decrease from 1994 up to 2002. This decrease indicates accelerating springtime net CO2 uptake. However, the CO2 minimum concentration in late summer (an indicator of net growing-season uptake) showed no positive trend since 1994, indicating that lower net CO2 uptake during summer cancelled out the enhanced uptake during spring. Using a recent satellite normalized difference vegetation index data set and climate data, we show that this lower summer uptake is probably the result of hotter and drier summers in both mid and high latitudes, demonstrating that a warming climate does not necessarily lead to higher CO2 growing-season uptake, even in high-latitude ecosystems that are considered to be temperature limited. [ABSTRACT FROM AUTHOR]

The interaction of land with the atmosphere is sensitive to soil moisture ( W). Evapotranspiration (ET) reacts to soil moisture in a nonlinear way, f( W), as soils dry from saturation to wilt point. This nonlinear behavior and the fact that soil moisture varies on scales as small as 1-10 m in nature, while numerical general circulation models (GCMs) have grid cell sizes on the order of 1 to 100s of kilometers, makes the calculation of grid cell-average ET problematic. It is impractical to simulate the land in GCMs on the small scales seen in nature, so techniques have been developed to represent subgrid scale heterogeneity, including: (1) statistical-dynamical representations of grid subelements of varying wetness, (2) relaxation of f( W), (3) moderating f( W) with approximations of catchment hydrology, (4) 'tiling ' the landscape into vegetation types, and (5) hyperresolution. Here we present an alternative method for representing subgrid variability in W, one proven in a conceptual framework where landscape-scale W is represented as a series of 'Bins ' of increasing wetness from dry to saturated. The grid cell-level f( W) is defined by the integral of the fractional area of the wetness bins and the value of f( W) associated with each. This approach accounts for the spatiotemporal dynamics of W. We implemented this approach in the SiB3 land surface parameterization and then evaluated its performance against a control, which assumes a horizontally uniform field of W. We demonstrate that the Bins method, with a physical basis, attenuates unrealistic jumps in model state and ET seen in the control runs. [ABSTRACT FROM AUTHOR]

The Department of Energy Atmospheric Radiation Measurement (ARM) program is a climate research user facility operating stationary ground sites that provide long-term measurements of climate-relevant properties, mobile ground- and ship-based facilities to conduct shorter field campaigns (6-12 months), and the ARM Aerial Facility (AAF). The airborne observations acquired by the AAF enhance the surface-based ARM measurements by providing high-resolution in situ measurements for process understanding, retrieval-algorithm development, and model evaluation that are not possible using surface-or satellite-based techniques. Several ARM aerial efforts were consolidated to form AAF in 2006. With the exception of a small aircraft used for routine measurements of aerosols and carbon cycle gases, AAF at the time had no dedicated aircraft and only a small number of instruments at its disposal. AAF successfully carried out several missions contracting with organizations and investigators who provided their research aircraft and instrumentation. In 2009, AAF started managing operations of the Battelle-owned Gulfstream I (G-1) large twin-turboprop research aircraft. Furthermore, the American Recovery and Reinvestment Act of 2009 provided funding for the procurement of over twenty new instruments to be used aboard the G-1 and AAF contracted aircraft. Depending on the requested scope, AAF now executes campaigns using the G-1 or contracted aircraft, producing freely available datasets for studying gas, aerosol, cloud, and radiative processes and their interactions in the atmosphere. AAF is also engaged in the maturation and testing of newly developed airborne sensors to help foster the next generation of airborne instruments. [ABSTRACT FROM AUTHOR]

Monitoring the global distribution and long-term variations of CO2 sources and sinks is required for characterizing the global carbon budget. Total column measurements are useful for estimating regional-scale fluxes; however, model transport remains a significant error source, particularly for quantifying local sources and sinks. To improve the capability of estimating regional fluxes, we estimate lower tropospheric CO2 concentrations from groundbased near-infrared (NIR) measurements with space-based thermal infrared (TIR) measurements. The NIR measurements are obtained from the Total Carbon Column Observing Network (TCCON) of solar measurements, which provide an estimate of the total CO2 column amount. Estimates of tropospheric CO2 that are co-located with TCCON are obtained by assimilating Tropospheric Emission Spectrometer (TES) free tropospheric CO2 estimates into the GEOS-Chem model.We find that quantifying lower tropospheric CO2 by subtracting free tropospheric CO2 estimates from total column estimates is a linear problem, because the calculated random uncertainties in total column and lower tropospheric estimates are consistent with actual uncertainties as compared to aircraft data. For the total column estimates, the random uncertainty is about 0.55 ppm with a bias of -5.66 ppm, consistent with previously published results. After accounting for the total column bias, the bias in the lower tropospheric CO2 estimates is 0.26 ppm with a precision (one standard deviation) of 1.02 ppm. This precision is sufficient for capturing the winter to summer variability of approximately 12 ppm in the lower troposphere; double the variability of the total column. This work shows that a combination of NIR and TIR measurements can profile CO2 with the precision and accuracy needed to quantify lower tropospheric CO2 variability. [ABSTRACT FROM AUTHOR]

The article discusses a study on the use of Aura TES and TCCON instruments for profiling tropospheric carbon dioxide. The study aims to improve the capability of estimating regional fluxes and estimates near-surface carbon dioxide values from ground-based near infrared (NIR) measurements with space-based thermal infrared (TIR) measurements. It reveals the consistency of calculated random uncertainties in total column and boundary layer with actual uncertainties as compared to aircraft data.

The article discusses the calibration of the Total Carbon Column Observing Network (TCCON) with World Meteorological Organization (WMO)-scale aircraft profile data. It notes that the TCCON develops accurate measurements of the column average dry-air mole fractions of chemical elements and gases in different sites worldwide. It mentions the consistency of the calibration curves shown between the different TCCON sites which can be described by a single calibration factor for each molecule.

The article discusses the mixing ratios of carbon monoxide (CO) retrieved from an atmospheric emitted radiance interferometer (AERI) spectra in Oklahoma between 2002 and 2009. It presents CO mixing ratios for the atmospheric layer recovered from infrared (IR) radiance spectra by a celestial point AERI deployed at an observatory in Oklahoma. It offers a comparison of CO values measured by AERI between 2002-2009 with those measured from the Atmospheric IR Sounder (AIRS) over North America.

The article presents a study which evaluates the importance of Total Carbon Column Observing Network (TCCON) which was calibrated by World Meteorological Organization (WMO) in situ trace gas measurement scales. It states that the network is designed for aircraft campaigns for Stratosphere-Troposphere Analyses of Regional Transport 2008 (START-08) included a profile over the Lamont and Lauder sites. The global calibration factor of gas captures the TCCON data is also evaluated.

Presents information on a study which measured the lower troposphere over a southern taiga forest area in Fyodorovskoye, western Russia. Site description; Methodology; Results and discussion; Conclusions.

A 5-yr record of continuous high-frequency carbon dioxide CO2 observations over the 1995–1999 period for the Mace Head Atmospheric Research Station has been examined to reveal a complex interplay between local- and regional-scale sources and sinks. During the winter months, an additional CO2 source, over and above fossil fuel combustion, is required to support the observed concentrations of CO2 in European regionally polluted air masses. During the summer months, an additional CO2 sink is required. Over the entire study period, the additional net European ecosystem exchange source–sink required is –0.36±0.4 Gtonne C yr−1. [Copyright &y& Elsevier]