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Nedoluha G.E.,U.S. Navy | Connor B.J.,BC Consulting | Barrett J.,State University of New York at Stony Brook | Mooney T.,State University of New York at Stony Brook | And 7 more authors.
Journal of Geophysical Research: Atmospheres

The ground-based measurements of upper stratospheric ClO, made with a ground-based millimeter wave instrument at Mauna Kea, Hawaii (19.8°N, 204.5°E) starting in 1992, are compared with UARS (Upper Atmosphere Research Satellite) MLS ClO measurements (1991-1998) and the Aura MLS ClO measurements (2004-2009). The ground-based measurements are made as part of the Network for the Detection of Atmospheric Composition Change (NDACC). Intercomparisons between the ground-based measurements and the Aura MLS measurements show that both instruments retrieve similar seasonal variations over Mauna Kea. The seasonal variation in ClO is also compared with measurements of variations in stratospheric CH4, which affects the partitioning of total inorganic chlorine. Using the ground-based instruments as a transfer standard, we find that the agreement between UARS and Aura MLS ClO measurements near the peak of the mixing ratio profile is within ∼1%. Combining the uncertainties in the biases calculated from the coincident ground-based and satellite measurements, we find that using the ground-based data as a transfer standard allows us to provide a 2σ limit to the bias between the UARS and Aura measurements of 3%-4% near the peak of the ClO profile. Given agreement between UARS and Aura MLS of ∼1% ± 4%, there is no reason to apply any bias correction in order to use the UARS and Aura MLS ClO measurements as a single data set. Copyright 2011 by the American Geophysical Union Copyright 2011 by the American Geophysical Union. Source

Keppel-Aleks G.,California Institute of Technology | Wennberg P.O.,California Institute of Technology | Washenfelder R.A.,National Oceanic and Atmospheric Administration | Wunch D.,California Institute of Technology | And 14 more authors.

New observations of the vertically integrated CO2 mixing ratio, (CO2), from ground-based remote sensing show that variations in CO2) are primarily determined by large-scale flux patterns. They therefore provide fundamentally different information than observations made within the boundary layer, which reflect the combined influence of large-scale and local fluxes. Observations of both (CO2) and CO2 concentrations in the free troposphere show that large-scale spatial gradients induce synoptic-scale temporal variations in (CO2) in the Northern Hemisphere midlatitudes through horizontal advection. Rather than obscure the signature of surface fluxes on atmospheric CO2, these synoptic-scale variations provide useful information that can be used to reveal the meridional flux distribution. We estimate the meridional gradient in (CO2) from covariations in (CO2) and potential temperature, θ, a dynamical tracer, on synoptic timescales to evaluate surface flux estimates commonly used in carbon cycle models. We find that simulations using Carnegie Ames Stanford Approach (CASA) biospheric fluxes underestimate both the (CO2) seasonal cycle amplitude throughout the Northern Hemisphere midlatitudes and the meridional gradient during the growing season. Simulations using CASA net ecosystem exchange (NEE) with increased and phase-shifted boreal fluxes better fit the observations. Our simulations suggest that climatological mean CASA fluxes underestimate boreal growing season NEE (between 45-65° N) by ∼40%. We describe the implications for this large seasonal exchange on inference of the net Northern Hemisphere terrestrial carbon sink. © 2012 Author(s). Source

Sagawa H.,Japan National Institute of Information and Communications Technology | Sato T.O.,Japan National Institute of Information and Communications Technology | Sato T.O.,Tokyo Institute of Technology | Baron P.,Japan National Institute of Information and Communications Technology | And 12 more authors.
Atmospheric Measurement Techniques

We evaluate the quality of ClO profiles derived from the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on the International Space Station (ISS). Version 2.1.5 of the level-2 product generated by the National Institute of Information and Communications Technology (NICT) is the subject of this study. Based on sensitivity studies, the systematic error was estimated as 5-10 pptv at the pressure range of 80-20 hPa, 35 pptv at the ClO peak altitude (∼ 4 hPa), and 5-10 pptv at pressures 0.5 hPa for daytime mid-latitude conditions. For nighttime measurements, a systematic error of 8 pptv was estimated for the ClO peak altitude (∼ 2 hPa). The SMILES NICT v2.1.5 ClO profiles agree with those derived from another level-2 processor developed by the Japan Aerospace Exploration Agency (JAXA) within the bias uncertainties, except for the nighttime measurements in the low and middle latitude regions where the SMILES NICT v2.1.5 profiles have a negative bias of ∼ 30 pptv in the lower stratosphere. This bias is considered to be due to the use of a limited spectral bandwidth in the retrieval process of SMILES NICT v2.1.5, which makes it difficult to distinguish between the weak ClO signal and wing contributions of spectral features outside the bandwidth. In the middle and upper stratosphere outside the polar regions, no significant systematic bias was found for the SMILES NICT ClO profile with respect to data sets from other instruments such as the Aura Microwave Limb Sounder (MLS), the Odin Sub-Millimetre Radiometer (SMR), the Envisat Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), and the ground-based radiometer at Mauna Kea, which demonstrates the scientific usability of the SMILES ClO data including the diurnal variations. Inside the chlorine-activated polar vortex, the SMILES NICT v2.1.5 ClO profiles show larger volume mixing ratios by 0.4 ppbv (30%) at 50 hPa compared to those of the JAXA processed profiles. This discrepancy is also considered to be an effect of the limited spectral bandwidth in the retrieval processing. We also compared the SMILES NICT ClO profiles of chlorine-activated polar vortex conditions with those measured by the balloon-borne instruments: Terahertz and submillimeter Limb Sounder (TELIS) and the MIPAS-balloon instrument (MIPAS-B). In conclusion, the SMILES NICT v2.1.5 ClO data can be used at pressures ∼30 hPa for scientific analysis. © 2013 Author(s).f 0. Source

Yoshida Y.,Japan National Institute of Environmental Studies | Kikuchi N.,Japan National Institute of Environmental Studies | Morino I.,Japan National Institute of Environmental Studies | Uchino O.,Japan National Institute of Environmental Studies | And 27 more authors.
Atmospheric Measurement Techniques

The column-averaged dry-air mole fractions of carbon dioxide and methane (XCO2 and XCH4) have been retrieved from Greenhouse gases Observing SATellite (GOSAT) Short-Wavelength InfraRed (SWIR) observations and released as a SWIR L2 product from the National Institute for Environmental Studies (NIES). XCO2 and XCH4 retrieved using the version 01.xx retrieval algorithm showed large negative biases and standard deviations (-8.85 and 4.75 ppm for XCO2 and -20.4 and 18.9 ppb for XCH 4, respectively) compared with data of the Total Carbon Column Observing Network (TCCON). Multiple reasons for these error characteristics (e.g., solar irradiance database, handling of aerosol scattering) are identified and corrected in a revised version of the retrieval algorithm (version 02.xx). The improved retrieval algorithm shows much smaller biases and standard deviations (-1.48 and 2.09 ppm for XCO2 and -5.9 and 12.6 ppb for XCH4, respectively) than the version 01.xx. Also, the number of post-screened measurements is increased, especially at northern mid- and high-latitudinal areas. © Author(s) 2013. Source

Deutscher N.M.,University of Wollongong | Deutscher N.M.,University of Bremen | Sherlock V.,NIWA - National Institute of Water and Atmospheric Research | Sherlock V.,CEA Saclay Nuclear Research Center | And 12 more authors.
Atmospheric Chemistry and Physics

We investigate factors that drive the variability in total column CO2at the Total Carbon Column Observing Network sites in the Southern Hemisphere using fluxes tagged by process and by source region from the CarbonTracker analysed product as well as the Simple Biosphere model. We show that the terrestrial biosphere is the largest driver of variability in the Southern Hemisphere column CO2. However, it does not dominate in the same fashion as in the Northern Hemisphere. Local-and hemispheric-scale biomass burning can also play an important role, particularly at the tropical site, Darwin. The magnitude of seasonal variability in the column-average dry-air mole fraction of CO2, XCO2, is also much smaller in the Southern Hemisphere and comparable in magnitude to the annual increase. Comparison of measurements to the model simulations highlights that there is some discrepancy between the two time series, especially in the early part of the Darwin data record. We show that this mismatch is most likely due to erroneously estimated local fluxes in the Australian tropical region, which are associated with enhanced photosynthesis caused by early rainfall during the tropical monsoon season. Source

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