Optical constants for Asian dust in midinfrared region

Lee, Kwang‐Mog; Park, Joong−Hyun

doi:10.1002/2013jd020207

Cited by 8 publications

(9 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The spectral dependence of (a) the real and (b) the imaginary parts of the complex refractive index for different mineral compositions. Illite data are from Querry et al (1978), quartz from Peterson and Weinman (1969), kaolinite and montmorillonite from Glotch et al (2007), calcite from Querry et al (1978) and Long et al (1993), gypsum from Long et al (1993), hematite from Marra et al (2005), and feldspar (labradorite) from Lee and Park (2014). No data are available for the imaginary part of feldspar.…”

Section: The Dust Emission Modulementioning

confidence: 99%

The Dust Direct Radiative Impact and Its Sensitivity to the Land Surface State and Key Minerals in the WRF‐Chem‐DuMo Model: A Case Study of Dust Storms in Central Asia

Sokolik

2018

JGR Atmospheres

View full text Add to dashboard Cite

The instantaneous direct radiative forcing is a basis for estimating the aerosol's climate effect, which is still one of the most uncertain factors. In this study, we incorporate eight minerals into a dust emission model that is coupled with the regional model. The model is used to estimate the direct radiative impact at the top of the atmosphere and at the surface by mineral dust. In addition, multiple tests are performed to investigate the sensitivity of the forcing to some key parameters (such as the surface albedo and key minerals, e.g., hematite and calcite). Based on our simulations of a dust event in Central Asia, the net instantaneous direct forcing (solar + infrared), averaged over the Aral Sea basin on 7 May 2007, are approximately in a range of (−8.05, −0.47) W/m2 at the top of the atmosphere. In comparison to the forcing estimated based on the default complex index, incorporation of dust minerals introduced a less cooling effect at the top of the atmosphere. We found that for a given clay‐to‐silt ratio, the net instantaneous forcing and the forcing in the solar band are sensitive to the surface albedo and hematite variation in the silt fraction. The forcing in the infrared band, however, is insensitive to these parameters, but it is sensitive to calcite and quartz in the silt fraction. Our results highlight the importance of accurately predicting the size‐resolved content of hematite and the surface albedo change to quantify the radiative forcing of mineral dust.

show abstract

Section: The Dust Emission Modulementioning

confidence: 99%

The Dust Direct Radiative Impact and Its Sensitivity to the Land Surface State and Key Minerals in the WRF‐Chem‐DuMo Model: A Case Study of Dust Storms in Central Asia

Sokolik

2018

JGR Atmospheres

View full text Add to dashboard Cite

show abstract

“…An earlier study by Lee and Park () already reported the optical constants for AD in the midinfrared region. Thus, the present study provides extended spectral coverage of the optical constants for AD.…”

Section: Introductionmentioning

confidence: 94%

Refractive Index for Asian Dust in the Ultraviolet‐Visible Region Determined From Compositional Analysis and Validated With OMI Observations

2020

View full text Add to dashboard Cite

Asian dust aerosols consist of various minerals, such as quartz, clay minerals, feldspars, and calcite. Complex refractive index of Asian dust is determined for a spectral range from 0.2 to 1.0 μm, assuming that the particles are an internal mixture of the component minerals in dust samples reported in previous literature. The derived optical constants for Asian dust are quite different from the refractive indices for other desert dusts. The imaginary refractive index for Asian dust is much smaller than that of the “mineral” model in Optical Properties of Aerosols and Clouds (OPAC) across the whole range. At wavelengths shorter than 650 nm, the present imaginary index is smaller than the index for Saharan dust, determined from mineralogical compositions of dust samples at Tinfou, Morocco, during the Saharan Mineral Dust Experiment (SAMUM). The simulated spectrum for an Asian dust event on 15 March 2009 in north‐east China using the present optical constants agree well with the spectrum measured by the Ozone Monitoring Instrument (OMI) on board the Aura spacecraft.

show abstract

“…The Absorbing Ångström Exponent (AAE), which represents the wavelength dependence of particle absorption, differs significantly between dust and the other two types in the 440-675 nm wavelength range. At shorter wavelengths, spectral variations of the imaginary part of the refractive index for the HAF and dust types are assumed based on Kirchstetter et al [39] and Lee et al [40], respectively. Kirchstetter et al [39] showed that the imaginary index for brown carbon varies following a power law in the UV range.…”

Section: Aerosol Model Assumptionsmentioning

confidence: 99%

“…Lee et al [40] obtained the spectral variation from 0.2 to 1.0 µm by assuming transported Asian dust consists of internally mixed mineral components and showed that the imaginary index varies more slowly between 350 and 500 nm than indicated by the Optical Properties of Aerosols and Clouds (OPAC) 'mineral-transported' dataset [41]. Using the results of Lee et al [40], the ω for dust was obtained as 1.835. This ω value is generally lower than the values of the Saharan dust sample described by Wagner et al [42].…”

Section: Aerosol Model Assumptionsmentioning

confidence: 99%

“…A parameter which represents the slope of the AAOD-wavelength relationship in log space is commonly used to describe this spectral dependence [52] and is known as AAE. Numerous studies have investigated the AAE in the UV range for various aerosol types and the values 3.9 [39], 1.8 [40] and 0.0 [41] were adopted for HAF, dust and NA aerosols, respectively, in this study. The AAE affects simulations of the spectral variation of the backscattered radiance and the accuracy of the OE method by affecting a priori retrieval and spectral fitting.…”

Section: Estimation Of Model Parametersmentioning

confidence: 99%

See 1 more Smart Citation

Optimal Estimation-Based Algorithm to Retrieve Aerosol Optical Properties for GEMS Measurements over Asia

Kim

Torres

et al. 2018

Remote Sensing

View full text Add to dashboard Cite

Abstract:The Geostationary Environment Monitoring Spectrometer (GEMS) is scheduled to be in orbit in 2019 onboard the GEO-KOMPSAT 2B satellite and will continuously monitor air quality over Asia. The GEMS will make measurements in the UV spectrum (300-500 nm) with 0.6 nm resolution. In this study, an algorithm is developed to retrieve aerosol optical properties from UV-visible measurements for the future satellite instrument and is tested using 3 years of existing OMI L1B data. This algorithm provides aerosol optical depth (AOD), single scattering albedo (SSA) and aerosol layer height (ALH) using an optimized estimation method. The retrieved AOD shows good correlation with Aerosol Robotic Network (AERONET) AOD with correlation coefficients of 0.83, 0.73 and 0.80 for heavy-absorbing fine (HAF) particles, dust and non-absorbing (NA) particles, respectively. However, regression tests indicate underestimation and overestimation of HAF and NA AOD, respectively. In comparison with AOD from the OMI/Aura Near-UV Aerosol Optical Depth and Single Scattering Albedo 1-orbit L2 Swath 13 km × 24 km V003 (OMAERUV) algorithm, the retrieved AOD has a correlation coefficient of 0.86 and linear regression equation, AOD GEMS = 1.18AOD OMAERUV + 0.09. An uncertainty test based on a reference method, which estimates retrieval error by applying the algorithm to simulated radiance data, revealed that assumptions in the spectral dependency of aerosol absorptivity in the UV cause significant errors in aerosol property retrieval, particularly the SSA retrieval. Consequently, retrieved SSAs did not show good correlation with AERONET values. The ALH results were qualitatively compared with the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) products and were found to be well correlated for highly absorbing aerosols. The difference between the attenuated-backscatter-weighted height from CALIOP and retrieved ALH were mostly closed to zero when the retrieved AOD is higher than 0.8 and SSA is lower than 0.93. Although retrieval accuracy was not significantly improved, the simultaneous consistent retrieval of AOD, SSA and ALH alone demonstrates the value of this stand-alone algorithm, given their nature for error using other methods. The use of these properties as input parameters for the air mass factor calculation is expected to improve the retrieval of other trace gases over Asia.

show abstract

Optical constants for Asian dust in midinfrared region

Cited by 8 publications

References 57 publications

The Dust Direct Radiative Impact and Its Sensitivity to the Land Surface State and Key Minerals in the WRF‐Chem‐DuMo Model: A Case Study of Dust Storms in Central Asia

The Dust Direct Radiative Impact and Its Sensitivity to the Land Surface State and Key Minerals in the WRF‐Chem‐DuMo Model: A Case Study of Dust Storms in Central Asia

Refractive Index for Asian Dust in the Ultraviolet‐Visible Region Determined From Compositional Analysis and Validated With OMI Observations

Optimal Estimation-Based Algorithm to Retrieve Aerosol Optical Properties for GEMS Measurements over Asia

Contact Info

Product

Resources

About