3,392 research outputs found
Potential of observations from the Tropospheric Emission Spectrometer to constrain continental sources of carbon monoxide
No full textWe have conducted an observing system simulation experiment for the Tropospheric Emission Spectrometer (TES) satellite instrument to determine the potential of nadir retrievals of carbon monoxide (CO) from this instrument to constrain estimates of continental sources of CO. We use the GEOS-CHEM global chemical transport model to produce a pseudoatmosphere in which the relationship between sources and concentrations of CO is known. Linear profile retrievals of CO are calculated by sampling this pseudoatmosphere along the orbit of TES. These retrievals are used as pseudo-observations with a maximum a posteriori inverse algorithm to estimate the CO sources from the different continents. This algorithm accounts for the finite vertical resolution of the retrieval, instrument errors, and representation and transport errors in the GEOS-CHEM simulation of CO. The structure of the transport error is estimated using the statistics of the difference between paired GEOS-CHEM forecasts of CO, and this structure is then scaled to match the model error in the GEOS-CHEM simulation of aircraft observations of Asian outflow over the NW Pacific. We show that with proper characterization of observation errors just 2 weeks of observations from TES have the potential to constrain estimates of continental sources of CO to within 10%
Estimating the summertime tropospheric ozone distribution over North America through assimilation of observations from the Tropospheric Emission Spectrometer
No full textWe assimilate ozone and CO retrievals from the Tropospheric Emission Spectrometer (TES) for July and August 2006 into the GEOS-Chem and AM2-Chem models. We show that the spatiotemporal sampling of the TES measurements is sufficient to constrain the tropospheric ozone distribution in the models despite their different chemical and transport mechanisms. Assimilation of TES data reduces the mean differences in ozone between the models from almost 8 ppbv to 1.5 ppbv. Differences between the mean model profiles and ozonesonde data over North America are reduced from almost 30% to within 5% for GEOS-Chem, and from 40% to within 10% for AM2-Chem, below 200 hPa. The absolute biases are larger in the upper troposphere and lower stratosphere (UT/LS), increasing to 10% and 30% in GEOS-Chem and AM2-Chem, respectively, at 200 hPa. The larger bias in the UT/LS reflects the influence of the spatial sampling of TES, the vertical smoothing of the TES retrievals, and the coarse vertical resolution of the models. The largest discrepancy in ozone between the models is associated with the ozone maximum over the southeastern USA. The assimilation reduces the mean bias between the models from 26 to 16 ppbv in this region. In GEOS-Chem, there is an increase of about 11 ppbv in the upper troposphere, consistent with the increase in ozone obtained by a previous study using GEOS-Chem with an improved estimate of lightning NOx emissions over the USA. Our results show that assimilation of TES observations into models of tropospheric chemistry and transport provides an improved description of free tropospheric ozone.</p
Integration of InSAR time series analysis and water vapour correction for mapping postseismic deformation after the 2003 Bam (Iran) Earthquake
No full textAtmospheric water-vapor effects represent a major limitation of interferometric synthetic aperture radar (InSAR) techniques, including InSAR time-series (TS) approaches (e.g., persistent or permanent scatterers and small-baseline subset). For the first time, this paper demonstrates the use of InSAR TS with precipitable water-vapor (InSAR TS + PWV) correction model for deformation mapping. We use MEdium Resolution Imaging Spectrometer (MERIS) near-infrafred (NIR) water-vapor data for InSAR atmospheric correction when they are available. For the dates when the NIR data are blocked by clouds, an atmospheric phase screen (APS) model has been developed to estimate atmospheric effects using partially water-vapor-corrected interferograms. Cross validation reveals that the estimated APS agreed with MERIS-derived line-of-sight path delays with a small standard deviation (0.3–0.5 cm) and a high correlation coefficient (0.84–0.98). This paper shows that a better TS of postseismic motion after the 2003 Bam (Iran) earthquake is achievable after reduction of water-vapor effects using the InSAR TS + PWV technique with coincident MERIS NIR water-vapor data
Potential of observations from the Tropospheric Emission
No full textnt sources and sinks; 0365 Atmospheric Composition and Structure: Troposphere---composition and chemistry; 0368 Atmospheric Composition and Structure: Troposphere---constituent transport and chemistry; KEYWORDS: TES, carbon monoxide, inverse methods Citation: Jones, D. B. A., K. W. Bowman, P. I. Palmer, J. R. Worden, D. J. Jacob, R. N. Hoffman, I. Bey, and R. M. Yantosca, Potential of observations from the Tropospheric Emission Spectrometer to constrain continental sources of carbon monoxide, J. Geophys. Res., 108(D24), 4789, doi:10.1029/2003JD003702, 2003. 1. Introduction [2] Accurate estimates of the sources of atmospheric carbon monoxide (CO) are essential to understand the impact of human activity on the composition of the atmosphere. Atmospheric CO is a product of incomplete combustion and a by-product of the oxidation of atmospheric hydrocarbons. It plays a critical role in determining the oxidative capacity of the atmosphere because it is the primary sink of OH, the mai
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Potential of observations from the Tropospheric Emission Spectrometer to constrain continental sources of carbon monoxide
No full textWe have conducted an observing system simulation experiment for the Tropospheric Emission Spectrometer (TES) satellite instrument to determine the potential of nadir retrievals of carbon monoxide (CO) from this instrument to constrain estimates of continental sources of CO. We use the GEOS-CHEM global chemical transport model to produce a pseudoatmosphere in which the relationship between sources and concentrations of CO is known. Linear profile retrievals of CO are calculated by sampling this pseudoatmosphere along the orbit of TES. These retrievals are used as pseudo-observations with a maximum a posteriori inverse algorithm to estimate the CO sources from the different continents. This algorithm accounts for the finite vertical resolution of the retrieval, instrument errors, and representation and transport errors in the GEOS-CHEM simulation of CO. The structure of the transport error is estimated using the statistics of the difference between paired GEOS-CHEM forecasts of CO, and this structure is then scaled to match the model error in the GEOS-CHEM simulation of aircraft observations of Asian outflow over the NW Pacific. We show that with proper characterization of observation errors just 2 weeks of observations from TES have the potential to constrain estimates of continental sources of CO to within 10%.Engineering and Applied SciencesVersion of Recor
Vertical transport of surface fire emissions observed from space
No full textWe use optimal estimation to infer the vertical distribution of surface emissions lofted from boreal and tropical biomass burning during June-October (JJASO) 2006. We use satellite observations of CO, a tracer of incomplete combustion, at thermal infrared and microwave wavelengths from Aura Tropospheric Emission Spectrometer (TES) and Microwave Limb Sounder (MLS), respectively. TES and MLS together typically provide two to three pieces of information. We use a maximum a posteriori (MAP) methodology to estimate emitted CO mass in five vertical regions spanning the troposphere and lower stratosphere, equivalent to estimating surface emissions. Correlations between neighboring vertical regions, due to vigorous mixing induced by surface heating, reduce the inversion to the information content provided by the data. We use a total of 1785 TES profile measurements, of which 672 are colocated with MLS. We define an injection height based on MAP statistics. We find that 10%-20% of boreal and tropical fire emissions, depending on the region, reach the free and upper troposphere during JJASO 2006. Our injection height estimates during two key pyroconvective events, Siberia (July) and Indonesia (October), qualitatively agree with measurements of aerosol index and attenuated backscatter from Aura Ozone Monitoring Instrument (OMI) and CALIPSO, respectively. Surface emissions inferred from our mass estimates agree with the Global Fire Emission Database biomass burning emission inventory to within +/-10%. The small percentage of emissions injected above the boundary layer result in disproportionate changes in CO concentrations of more than 2-25 ppb and 15-160 ppb over boreal and tropical regions, respectively.</p
The vertical distribution of ozone instantaneous radiative forcing from satellite and chemistry climate models
No full textWe evaluate the instantaneous radiative forcing (IRF) of tropospheric ozone predicted by four state-of-the-art global chemistry climate models (AM2-Chem, CAM-Chem, ECHAM5-MOZ, and GISS-PUCCINI) against ozone distribution observed from the NASA Tropospheric Emission Spectrometer (TES) during August 2006. The IRF is computed through the application of an observationally constrained instantaneous radiative forcing kernels (IRFK) to the difference between TES and model-predicted ozone. The IRFK represent the sensitivity of outgoing longwave radiation to the vertical and spatial distribution of ozone under all-sky condition. Through this technique, we find total tropospheric IRF biases from -0.4 to + 0.7 W/m(2) over large regions within the tropics and midlatitudes, due to ozone differences over the region in the lower and middle troposphere, enhanced by persistent bias in the upper troposphere-lower stratospheric region. The zonal mean biases also range from -30 to + 50 mW/m(2) for the models. However, the ensemble mean total tropospheric IRF bias is less than 0.2 W/m(2) within the entire troposphere.</p
Can paleoceanographic tracers constrain meridional circulation rates?
No full textAuthor Posting. © American Meteorological Society, 2007. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 37 (2007): 394-407, doi:10.1175/jpo3018.1.The ability of paleoceanographic tracers to constrain rates of transport is examined using an inverse method to combine idealized observations with a geostrophic model. Considered are the spatial distribution, accuracy, and types of tracers required to constrain changes in meridional transport within an idealized single-hemisphere basin. Measurements of density and radioactive tracers each act to constrain rates of transport. Conservative tracers, while not of themselves able to inform regarding rates of transport, improve constraints when coupled with density or radioactive observations. It is found that the tracer data would require an accuracy one order of magnitude better than is presently available for paleo-observations to conclusively rule out factor-of-2 changes in meridional transport, even when assumed available over the entire model domain. When data are available only at the margins and bottom of the model, radiocarbon is unable to constrain transport while density remains effective only when a reference velocity level is assumed. The difficulty in constraining the circulation in this idealized model indicates that placing firm bounds on past meridional transport rates will prove challenging.The first author is supported by the NOAA Postdoctoral
Program in Climate and Global Change and GG
by the National Ocean Partnership Program (ECCO).
Author OM acknowledges support from the National
Science Foundation
Observing short timescale cloud development to constrain aerosol-cloud interactions
No full textThe aerosol impact on liquid water path (LWP) is a key uncertainty in the overall climate impact of aerosol. However, despite a significant effort in this area, the size of the effect remains poorly constrained, and even the sign is unclear. Recent studies have shown that the relationship between droplet number concentration (Nd ) and LWP is an unreliable measure of the
impact of Nd variations on LWP due to the difficulty in establishing causality. In this work, we use satellite observations of the short-term development of clouds to examine the role of Nd perturbations in LWP variations.
Similar to previous studies, an increase followed by a general decrease in LWP with increasing Nd is observed, suggesting an overall negative LWP response to Nd and a warming LWP adjustment to aerosol. However, the Nd also responds to the local environment, with aerosol production, entrainment from the free troposphere and wet scavenging all acting to modify the Nd . Many of these effects act to further steepen the Nd -LWP relationship and obscure the causal Nd impact on LWP.
Using the temporal development of clouds to account for these feedbacks in the Nd -LWP system, a weaker negative Nd -LWP relationship is observed over most of the globe. This relationship is highly sensitive to the initial cloud state, illuminating the roles of different processes in shaping the Nd -LWP relationship. The nature of the current observing system limits this work to
a single time period for observations, highlighting the need for more frequent observations of key cloud properties to constrain cloud behaviour at process timescales
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