Clear‐column closure studies of aerosols and water vapor aboard the NCAR C‐130 during ACE‐Asia, 2001

Redemann, Jens; Masonis, Sarah J.; Schmid, Beat; Anderson, Theodore L.; Russell, P. B.; Livingston, J. M.; Dubovik, Оleg; Clarke, A. D.

doi:10.1029/2003jd003442

Cited by 61 publications

(109 citation statements)

References 38 publications

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“…The study by Schmid et al (2000) suggests that this agreement occurs at the common measurement wavelength of around 550 nm; however, the comparison may not be as well constrained at other wavelengths. Aerosol closure studies show the best agreement when limited to submicrometer sizes and spherical particles that pose the smallest challenges to inlets, measurement techniques, and calculation of aerosol properties (Magi et al, 2003;Redemann et al, 2003).…”

Section: Summary From Closure Studiesmentioning

confidence: 99%

Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oceans: estimates based on in-situ chemical and optical measurements and chemical transport modeling

et al. 2006

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Abstract. The largest uncertainty in the radiative forcing of climate change over the industrial era is that due to aerosols, a substantial fraction of which is the uncertainty associated with scattering and absorption of shortwave (solar) radiation by anthropogenic aerosols in cloud-free conditions (IPCC, 2001). Quantifying and reducing the uncertainty in aerosol influences on climate is critical to understanding climate change over the industrial period and to improving predictions of future climate change for assumed emission scenarios. Measurements of aerosol properties during major field campaigns in several regions of the globe during the past decade are contributing to an enhanced understanding of atmospheric aerosols and their effects on light scattering and climate. The present study, which focuses on three regionsCorrespondence to: T. S. Bates (tim.bates@noaa.gov) downwind of major urban/population centers (North Indian Ocean (NIO) during INDOEX, the Northwest Pacific Ocean (NWP) during ACE-Asia, and the Northwest Atlantic Ocean (NWA) during ICARTT), incorporates understanding gained from field observations of aerosol distributions and properties into calculations of perturbations in radiative fluxes due to these aerosols. This study evaluates the current state of observations and of two chemical transport models (STEM and MOZART). Measurements of burdens, extinction optical depth (AOD), and direct radiative effect of aerosols (DRE -change in radiative flux due to total aerosols) are used as measurement-model check points to assess uncertainties. In-situ measured and remotely sensed aerosol properties for each region (mixing state, mass scattering efficiency, single scattering albedo, and angular scattering properties and their dependences on relative humidity) are used as input parameters to two radiative transfer models (GFDL and UniversityPublished by Copernicus GmbH on behalf of the European Geosciences Union. T. S. Bates et al.:Constraining aerosol climate models with observations of Michigan) to constrain estimates of aerosol radiative effects, with uncertainties in each step propagated through the analysis. Constraining the radiative transfer calculations by observational inputs increases the clear-sky, 24-h averaged AOD (34±8%), top of atmosphere (TOA) DRE (32±12%), and TOA direct climate forcing of aerosols (DCF -change in radiative flux due to anthropogenic aerosols) (37±7%) relative to values obtained with "a priori" parameterizations of aerosol loadings and properties (GFDL RTM). The resulting constrained clear-sky TOA DCF is −3.3±0.47, −14±2.6, −6.4±2.1 Wm −2 for the NIO, NWP, and NWA, respectively. With the use of constrained quantities (extensive and intensive parameters) the calculated uncertainty in DCF was 25% less than the "structural uncertainties" used in the IPCC-2001 global estimates of direct aerosol climate forcing. Such comparisons with observations and resultant reductions in uncertainties are essential for improving and developing confidence in climate model calculations in...

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Section: Summary From Closure Studiesmentioning

confidence: 99%

Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oceans: estimates based on in-situ chemical and optical measurements and chemical transport modeling

et al. 2006

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“…The error bars on the AATS extinction values for a particular profile were derived by combining, in an rms sense, the standard deviation of the set of retrieval results with an estimate of the uncertainty (Eq. 5 in Redemann et al, 2003) due to spatial and/or temporal inhomogeneity of the aerosol field during the vertical profile. These uncertainties were used to weight the bilinear regression, which yielded a similar slope (1.05±0.04) and intercept (−0.001±0.001) as the unweighted regression.…”

Section: Aats-14mentioning

confidence: 99%

NASA LaRC airborne high spectral resolution lidar aerosol measurements during MILAGRO: observations and validation

et al. 2009

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Abstract. The NASA Langley Research Center (LaRC) airborne High Spectral Resolution Lidar (HSRL) measures vertical profiles of aerosol extinction, backscatter, and depolarization at both 532 nm and 1064 nm. In March of 2006 the HSRL participated in the Megacity Initiative: Local and Global Research Observations (MILAGRO) campaign along with several other suites of instruments deployed on both aircraft and ground based platforms. This paper presents high spatial and vertical resolution HSRL measurements of aerosol extinction and optical depth from MILAGRO and comparisons of those measurements with similar measurements from other sensors and model predictions. HSRL measurements coincident with airborne in situ aerosol scattering and absorption measurements from two different instrument suites on the C-130 and G-1 aircraft, airborne aerosol optical depth (AOD) and extinction measurements from an airborne tracking sunphotometer on the J-31 aircraft, and AOD from a network of ground based Aerosol Robotic Network (AERONET) sun photometers are presented as a validation of the HSRL aerosol extinction and optical depth products. Regarding the extinction validation, we find bias differences between HSRL and these instruments to be less than 3% (0.01 km −1 ) at 532 nm, the wavelength at which the HSRL technique is employed. The rms differences at 532 nm were less than 50% (0.015 km −1 ). To our knowledge this is the Correspondence to: R. R. Rogers (raymond.r.rogers@nasa.gov) most comprehensive validation of the HSRL measurement of aerosol extinction and optical depth to date. The observed bias differences in ambient aerosol extinction between HSRL and other measurements is within 15-20% at visible wavelengths, found by previous studies to be the differences observed with current state-of-the-art instrumentation .

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“…there has been a comparison between an ambient extinction reference and extinction measured behind an LTI on the C-130. Redemann et al (2003) report on ACE-Asia measurements with their AATS-6 tracking sun photometer, which they compare to simultaneous TSI nephelometer and PSAP measurements of in situ extinction. For 943 fine-mode-dominated samples (for which the inlets are unlikely to modify the distribution by much) the in situ versus AATS-6 slope was 1.007 and the r 2 was 0.81.…”

Section: What Is the Impact Of Inlet-derived Changes On Studies Of Aementioning

confidence: 99%

PELTI: Measuring the Passing Efficiency of an Airborne Low Turbulence Aerosol Inlet

Huebert

Howell

Covert

et al. 2004

Aerosol Science and Technology

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In an effort to improve the accuracy of airborne aerosol studies, we compared a new porous-diffuser low-turbulence inlet (LTI) with three other inlets on the NSF/NCAR C-130, using both dust and sea salt as test aerosols. Analysis of bulk filters behind the LTI and an external reference total aerosol sampler (TAS) found no significant differences, while both the NASA shrouded solid diffuser inlet (SD) and NCAR community aerosol inlet (CAl) passed smaller amounts. However, scanning electron microscopic analyses of particles behind the LTI and TAS confirmed the model prediction that the LTI porous diffuser (PD) enhanced 7 J.Lm particle concentrations by about 60%. Aerodynamic particle size distributions behind the other inlets began to diverge from enhancement-corrected LTI values above 2 J.Lm, with mass concentrations of larger particles lower by as much as a factor of ten behind the CAl and a factor of 2 behind the SD. We conclude that the corrected LTI distributions were closer to ambient values than those from either the CAl or the SD. Since tubing losses contributed the most uncertainty when deducing ambient supermicron size distributions from LTI data, minimizing them should be a high priority for future experiments. Measured transfer tubing losses were larger than model estimates, in part because of some complex pieces for which no suitable model exists. The LTI represents a significant advance in our ability to It is always a pleasure to work with the staff of NCAR's RAF, who provided us with support well above and beyond the call of duty. Krista Laursen and Alan Schanot were instrumental in getting the equipment installed and the experiment into the field successfully. Darrel Baumgardner worked with the FSSPs and their data. We are particularly grateful to the National Science Foundation for a series of grants that made the LTI and PELTI a reality, including ATM-9813515 and ATM-0002698 to UH. This is SOEST contribution No. 6206.

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Clear‐column closure studies of aerosols and water vapor aboard the NCAR C‐130 during ACE‐Asia, 2001

Cited by 61 publications

References 38 publications

Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oceans: estimates based on in-situ chemical and optical measurements and chemical transport modeling

Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oceans: estimates based on in-situ chemical and optical measurements and chemical transport modeling

NASA LaRC airborne high spectral resolution lidar aerosol measurements during MILAGRO: observations and validation

PELTI: Measuring the Passing Efficiency of an Airborne Low Turbulence Aerosol Inlet

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