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DOE OSTI2014

Accelerated evolution of the Lyα luminosity function at z ≳ 7 revealed by the Subaru ultra-deep survey for Lyα emitters at z = 7.3

We present the ultra-deep Subaru narrowband imaging survey for Lyα emitters (LAEs) at z = 7.3 in the Subaru/XMM-Newton Deep Survey (SXDS) and Cosmic Evolution Survey (COSMOS) fields (∼0.5 deg{sup 2}) with a total integration time of 106 hr. Exploiting our new sharp bandwidth filter, NB101, installed on the Suprime-Cam, we have reached L(Lyα) = 2.4 × 10{sup 42} erg s{sup –1} (5σ) for z = 7.3 LAEs, about four times deeper than previous Subaru z ≳ 7 studies, which allows us to reliably investigate the evolution of the Lyα luminosity function (LF) for the first time down to the luminosity limit same as those of Subaru z = 3.1-6.6 LAE samples. Surprisingly, we only find three and four LAEs in the SXDS and COSMOS fields, respectively, while one expects a total of ∼65 LAEs by our survey in the case of no Lyα LF evolution from z = 6.6 to 7.3. We identify a decrease of the Lyα LF from z = 6.6 to 7.3 at the >90% confidence level from our z = 7.3 Lyα LF with the best-fit Schechter parameters of L{sub Lyα}{sup ∗}=2.7{sub −1.2}{sup +8.0}×10{sup 42} erg s{sup −1} and ϕ{sup ∗}=3.7{sub −3.3}{sup +17.6}×10{sup −4} Mpc{sup −3} for a fixed α = –1.5. Moreover, the evolution of the Lyα LF is clearly accelerated at z > 6.6 beyond the measurement uncertainties including cosmic variance. Because no such accelerated evolution of the UV-continuum LF or the cosmic star formation rate (SFR) is found at z ∼ 7, but suggested only at z > 8, this accelerated Lyα LF evolution is explained by physical mechanisms different from a pure SFR decrease but related to the Lyα production and escape in the process of cosmic reionization. Because a simple accelerating increase of intergalactic medium neutral hydrogen absorbing Lyα cannot be reconciled with Thomson scattering of optical depth measurements from WMAP and Planck, our findings may support new physical pictures suggested by recent theoretical studies, such as the existence of HI clumpy clouds within cosmic ionized bubbles that are selectively absorbing Lyα and the large ionizing photon escape fraction of galaxies causing weak Lyα emission.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1984

Inhomogeneous models of Titan's aerosol distribution

A model of Titan's aerosol is presented which allows the particle size to vary with height. The model assumes a refractive index appropriate to an ethylene polymer and a mass flux independent of height equal to the value derived from laboratory measurements. The free parameters of the model are determined by fitting to the observed geometric albedo at 4000 and 6000 A. A methane spectrum is derived which is in excellent agreement with observations. An aerosol optical depth of about 5 is found in the visible, with the particle radius varying from 0.01 to 8 microns. The presence of an optically thick methane cloud at the temperature minimum is indicated.

Podolak, M.↗
NASA NTRS1991

Gas and dust in the Ophiuchus region

The interstellar gas and dust in the Ophiuchus molecular cloud region are studied through H I, CO, and IRAS observations. The generally good global correlation of H I with the infrared intensity and dust optical depth breaks down on the smaller scales that can be distinguished in this nearby region. The presence of an intense ultraviolet field and shocks caused by the early-type stars can account for this difference. Integrated emission from the CO molecule correlates with the dust optical depth. This correlation is used to derive the conversion factor between W(CO) and the atomic hydrogen column density. The region close to the early-type stars in Upper Scorpius shows a considerable amount of infrared emission, but negligible CO emission.

De Geus, E. J.↗
NASA NTRS1995

Direct Radiative Forcing by Anthropogenic Airborne Mineral Aerosols

Although airborne mineral aerosols are traditionally considered a natural component of the earth-atmosphere climate system, an examination of dust production mechanisms and dust source regions reveals that a significant fraction of the dust loading could be due to human activities. We find that the global mean direct solar radiative forcing by anthropogenically generated mineral aerosols may be comparable to the direct solar radiative forcing by other anthropogenic aerosols. The net regional forcing by mineral aerosols can greatly exceed the regional forcing by sulfate aerosol and can even be comparable to the net forcing by clouds. An improved understanding of the radiative forcing due to mineral aerosols requires better knowledge of the regional patterns of dust production rates and dust optical depths, more comprehensive measurements of dust microphysical and optical characteristics, as well as a comprehensive assessment of the role of dust aerosols on infrared radiative forcing.

Sokolik, Irina N.↗
DOE OSTI2018

New Self-lensing Models of the Small Magellanic Cloud: Can Gravitational Microlensing Detect Extragalactic Exoplanets?

We use three-dimensional distributions of classical Cepheids and RR Lyrae stars in the Small Magellanic Cloud (SMC) to model the stellar density distribution of a young and old stellar population in that galaxy. We use these models to estimate the microlensing self-lensing optical depth to the SMC, which is in excellent agreement with the observations. Our models are consistent with the total stellar mass of the SMC of about 1.0×10{sup 9} M{sub ⊙} under the assumption that all microlensing events toward this galaxy are caused by self-lensing. We also calculate the expected event rates and estimate that future large-scale surveys, like the Large Synoptic Survey Telescope (LSST), will be able to detect up to a few dozen microlensing events in the SMC annually. If the planet frequency in the SMC is similar to that in the Milky Way, a few extragalactic planets can be detected over the course of the LSST survey, provided significant changes in the SMC observing strategy are devised. A relatively small investment of LSST resources can give us a unique probe of the population of extragalactic exoplanets.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1992

Does UV instrumentation effectively measure ozone abundance?

Measurements of O3 on Mars provide significant information about the chemistry and composition of the atmosphere, including long-term changes. The most extensive and accurate data were inferred from the Mariner 9 UV spectrometer experiment. Mars O3 shows strong seasonal and latitudinal variation, with column abundances ranging from 0.2 microns at equatorial latitudes to 60 microns over the northern winter polar latitudes (1 micron-atm is a column abundance of 2.689 x 10(exp 15) molecules cm(exp-2)). The Mariner 9 UV spectrometer scanned from 2100 to 3500 Angstroms in one of its two spectral channels every 3 seconds with a spectral resolution of 15 Angstroms and an effective field-of-view of approximately 300 km(exp 2). Measurements were made for almost half a Martian year, with winter and spring in the Northern Hemisphere and summer and fall in the Southern Hemisphere. The detectability limit of the spectrometer was approximately 3 microns of ozone. The UV spectrometer on Mariner 9 was incapable of penetrating the dust during dust storms; the single-scattering albedo and phase function of airborne dust and cloud ice are not known to the degree required to extract the small UV signal reflected up from near the surface. The reflectance spectroscopy technique would also have difficulty detecting the total column abundance of O3 in cases where large dust abundances exist together with the polar hood, especially at high latitudes where large solar zenith angles magnify those optical depths; yet these cases would contain the maximum O3, based on theoretical results. It is quite possible that the maximum O3 column abundance observed by Mariner 9 of 60 microns is common. In fact, larger quantities may exist in some of the colder areas with optically thick clouds and dust. As the Viking period often had more atmospheric dust loading than did that of Mariner 9, the reflectance spectroscopy technique may even have been incapable of detecting the entire O3 column abundance during much of the Mars year that Viking observed, particularly at high latitudes.

Lindner, Bernhard Lee↗
NASA NTRS1978

The albedo of Titan

It is shown that a two-layer model of Titan's atmosphere is required in order to match laboratory data on methane absorption to ground-based IR observations of Titan. An excellent fit to the observations is obtained with a model where the dust in Titan's atmosphere is confined to a region containing 50 m-am of methane and located above an atmosphere with 1.95 km-am of methane, with the amount of dust being the value required for an extinction optical depth of 5 at 0.5 micron. The surface reflectivity required by this model is about 40% to 50%, which is typical for both dirty snow and clouds. The possibility is discussed of distinguishing between two scenarios for the observed surface of Titan (a true surface or just cloud tops) on the basis of limb-darkening curves obtained at many wavelengths with an orbiting telescope or a flyby mission.

Podolak, M.↗
NASA NTRS1983

SAM 2 measurements of the polar stratospheric aerosol. Volume 3: October 1979 to April 1980

The Stratospheric Aerosol Measurement (SAM) II sensor is aboard the Earth-orbiting Nimbus 7 spacecraft providing extinction measurements of the Antarctic and Arctic stratospheric aerosol with a vertical resolution of 1 km. Representative examples and weekly averages of aerosol data and corresponding temperature profiles for the time and place of each SAM II measurement (Oct. 1979 through Apr. 1980) are presented. Contours of aerosol extinction as a function of altitude and longitude or time are plotted and weekly aerosol optical depths are calculated. Seasonal variations and variations in space (altitude and longitude) for both polar regions are easily seen. Typical values of aerosol extinction at the SAM II wavelength of 1.0 microns for this time period are 2 to 4 times .0001/km in the main stratospheric aerosol layer. Optical depths for the stratosphere are about 0.002 to 0.003, up slightly over normal background levels (due to the eruption of Sierra Negra, Nov. 1979). Polar stratospheric clouds at altitudes of about 22 km were observed during the Arctic winter. A ready-to-use format containing a representative sample of the third 6 months of data to be used in atmospheric and climatic studies is presented.

Mccormick, M. P.↗
NASA NTRS1995

Thermal Balance in Dense Molecular Clouds: Radiative Cooling Rates and Emission-Line Luminosities

We consider the radiative cooling of fully shielded molecular astrophysical gas over a wide range of temperatures ( 10 K < T < 2500 K) and H2 densities ( 10(exp 3)/cc < n(H2) < 10(exp 10)/cc). Our model for the radiative cooling of molecular gas includes a detailed treatment of the interstellar chemistry that determines the abundances of important coolant molecules, and a detailed treatment of the excitation of the species H2, CO, H2O, HCl, O2, C, O, and their isotopic variants where important. We present results for the total radiative cooling rate and for the cooling rate due to individual coolant species, as a function of the gas temperature, density, and optical depth. We have also computed the individual millimeter, submillimeter, and far-infrared line strengths that contribute to the total radiative cooling rate, and we have obtained example spectra for the submillimeter emission expected from molecular cloud cores. Many of the important cooling lines will be detectable using the Infrared Space Observatory and the Submillimeter Wave Astronomy Satellite.

Neufeld, David A.↗
NASA NTRS2013

The Collection 6 'dark-target' MODIS Aerosol Products

Aerosol retrieval algorithms are applied to Moderate resolution Imaging Spectroradiometer (MODIS) sensors on both Terra and Aqua, creating two streams of decade-plus aerosol information. Products of aerosol optical depth (AOD) and aerosol size are used for many applications, but the primary concern is that these global products are comprehensive and consistent enough for use in climate studies. One of our major customers is the international modeling comparison study known as AEROCOM, which relies on the MODIS data as a benchmark. In order to keep up with the needs of AEROCOM and other MODIS data users, while utilizing new science and tools, we have improved the algorithms and products. The code, and the associated products, will be known as Collection 6 (C6). While not a major overhaul from the previous Collection 5 (C5) version, there are enough changes that there are significant impacts to the products and their interpretation. In its entirety, the C6 algorithm is comprised of three sub-algorithms for retrieving aerosol properties over different surfaces: These include the dark-target DT algorithms to retrieve over (1) ocean and (2) vegetated-dark-soiled land, plus the (3) Deep Blue (DB) algorithm, originally developed to retrieve over desert-arid land. Focusing on the two DT algorithms, we have updated assumptions for central wavelengths, Rayleigh optical depths and gas (H2O, O3, CO2, etc.) absorption corrections, while relaxing the solar zenith angle limit (up to 84) to increase pole-ward coverage. For DT-land, we have updated the cloud mask to allow heavy smoke retrievals, fine-tuned the assignments for aerosol type as function of season location, corrected bugs in the Quality Assurance (QA) logic, and added diagnostic parameters such as topographic altitude. For DT-ocean, improvements include a revised cloud mask for thin-cirrus detection, inclusion of wind speed dependence in the retrieval, updates to logic of QA Confidence flag (QAC) assignment, and additions of important diagnostic information. At the same time as we have introduced algorithm changes, we have also accounted for upstream changes including: new instrument calibration, revised land-sea masking, and changed cloud masking. Upstream changes also impact the coverage and global statistics of the retrieved AOD. Although our responsibility is to the DT code and products, we have also added a product that merges DT and DB product over semi-arid land surfaces to provide a more gap-free dataset, primarily for visualization purposes. Preliminary validation shows that compared to surface-based sunphotometer data, the C6, Level 2 (along swath) DT-products compare at least as well as those from C5. C6 will include new diagnostic information about clouds in the aerosol field, including an aerosol cloud mask at 500 m resolution, and calculations of the distance to the nearest cloud from clear pixels. Finally, we have revised the strategy for aggregating and averaging the Level 2 (swath) data to become Level 3 (gridded) data. All together, the changes to the DT algorithms will result in reduced global AOD (by 0.02) over ocean and increased AOD (by 0.02) over land, along with changes in spatial coverage. Changes in calibration will have more impact to Terras time series, especially over land. This will result in a significant reduction in artificial differences in the Terra and Aqua datasets, and will stabilize the MODIS data as a target for AEROCOM studie

Aerosol retrieval algorithms↗
NASA NTRS2015

MISR Calibration Issues in High-Contrast Scenes, and Empirical Corrections

We diagnose the potential causes for the Multi-angle Imaging SpectroRadiometer's (MISR) persistent high aerosol optical depth (AOD) bias at low AOD with the aid of coincident MODerate-resolution Imaging Spectroradiometer (MODIS) imagery from NASA's Terra satellite. Internal reflections within the MISR instrument are responsible for a large portion of the high AOD bias in high-contrast scenes, which are especially common as broken-cloud situations over ocean. Discrepancies between MODIS and MISR nadir-viewing near-infrared (NIR) images are used to optimize nine parameters, along with a background reflectance modulation term (that was modeled separately), to represent the observed features. Independent, surface-based AOD measurements from the AErosol RObotic NETwork (AERONET) and the Marine Aerosol Network (MAN) are compared with MISR Research Algorithm (RA) AOD retrievals for 1118 coincidences to validate the corrections when applied to the nadir and off-nadir cameras. Additionally, the calibration coefficients for the red and NIR channels used for MISR over-water aerosol retrievals were reassessed with the RA to be consistent on a camera-by-camera basis. With these corrections, plus the baseline RA corrections applied (except enhanced cloud screening), the median AOD bias in the mid-visible (green) band decreases from 0.010 to 0.002, the RMSE decreases by approx. 10%, and the slope and correlation of the MISR vs. sun photometer Ångström Exponent improves. For AOD558 nm < 0.10 and with additional cloud screening, the median bias for the RA-retrieved AOD in the green band decreases from 0.011 to 0.003, compared to ~ 0.023 for the Standard Algorithm (SA). RMSE decreases by ~ 20% compared to the baseline (uncorrected) RA and by 17-53% compared to the SA. After all corrections and cloud screening are implemented, for AOD558 nm < 0.10, which includes about half the validation data, 68% absolute AOD errors for the RA have dropped to < 0.02 (approx. 0.018).

MISR↗
NASA NTRS2020

The AERONET Version 3 Aerosol Retrieval Algorithm, Associated Uncertainties and Comparisons to Version 2

The Aerosol Robotic Network (AERONET) Version 3 (V3) aerosol retrieval algorithm is described, which is based on the Version 2 (V2) algorithm with numerous updates. Comparisons of V3 aerosol retrievals to those of V2 are presented, along with a new approach to estimate uncertainties in many of the retrieved aerosol parameters. Changes in the V3 aerosol retrieval algorithm include (1) a new polarized radiative transfer code (RTC), which replaced the scalar RTC of V2, (2) detailed characterization of gas absorption by adding NO2 and H2O to specify total gas absorption in the atmospheric column, specification of vertical profiles of all the atmospheric species, (3) new bidirectional reflectance distribution function (BRDF) parameters for land sites adopted from the MODIS BRDF/Albedo product, (4) a new version of the extraterrestrial solar flux spectrum, and (5) a new temperature correction procedure of both direct Sun and sky radiance measurements. The potential effect of each change in V3 on single scattering albedo (SSA) retrievals was analyzed. The operational almucantar retrievals of V2 versus V3 were compared for four AERONET sites: GSFC, Mezaira, Mongu, and Kanpur. Analysis showed very good agreement in retrieved parameters of the size distributions. Comparisons of SSA retrievals for dust aerosols (Mezaira) showed a good agreement in 440 nm SSA, while for longer wavelengths V3 SSAs are systematically higher than those of V2, with the largest mean difference at 675 nm due to cumulative effects of both extraterrestrial solar flux and BRDF changes. For non-dust aerosols, the largest SSA deviation is at 675 nm due to differences in extraterrestrial solar flux spectrums used in each version. Further, the SSA 675 nm mean differences are very different for weakly (GSFC) and strongly (Mongu) absorbing aerosols, which is explained by the lower sensitivity to a bias in aerosol scattering optical depth by less absorbing aerosols. A new hybrid (HYB) sky radiance measurement scan is introduced and discussed. The HYB combines features of scans in two different planes to maximize the range of scattering angles and achieve scan symmetry, thereby allowing for cloud screening and spatial averaging, which is an advantage over the principal plane scan that lacks robust symmetry. We show that due to an extended range of scattering angles, HYB SSA retrievals for dust aerosols exhibit smaller variability with solar zenith angles (SZAs) than those of almucantar (ALM), which allows extension of HYB SSA retrievals to SZAs less than 50∘ to as small as 25∘. The comparison of SSA retrievals from closely time-matched HYB and ALM scans in the 50 to 75∘ SZA range showed good agreement with the differences below ∼0.005. We also present an approach to estimate retrieval uncertainties which utilizes the variability in retrieved parameters generated by perturbing both measurements and auxiliary input parameters as a proxy for retrieval uncertainty. The perturbations in measurements and auxiliary inputs are assumed as estimated biases in aerosol optical depth (AOD), radiometric calibration of sky radiances combined with solar spectral irradiance, and surface reflectance. For each set of Level 2 Sun/sky radiometer observations, 27 inputs corresponding to 27 combinations of biases were produced and separately inverted to generate the following statistics of the inversion results: average, standard deviation, minimum and maximum values. From these statistics, standard deviation (labeled U27) is used as a proxy for estimated uncertainty, and a lookup table (LUT) approach was implemented to reduce the computational time. The U27 climatological LUT was generated from the entire AERONET almucantar (1993–2018) and hybrid (2014–2018) scan databases by binning U27s in AOD (440 nm), Angström exponent (AE, 440–870 nm), and SSA (440, 675, 870, 1020 nm). Using this LUT approach, the uncertainty estimates U27 for each individual V3 Level 2 retrieval can be obtained by interpolation using the corresponding measured and inverted combination of AOD, AE, and SSA.

Aliaksandr Siniuk↗
NASA NTRS1992

Interstellar dust from the Milky Way to the Magellanic Clouds

Interstellar dust in the Magellanic Clouds, with a weak or nearly absent 2175 A extinction feature, may be of interest in studies of galaxies in early stages of chemical evolution. To this inquiry, we extend the graphite-silicate grain model, introduced by Mathis, Rumpl, and Nordsieck and developed by Draine and Lee (1984) from the Milky Way to the Magellanic Clouds. We find that the empirical extinction curves in the Large and Small Magellanic Clouds can be reproduced by adjusting only the relative abundances of graphite and silicate grains, while leaving all other model properties fixed to those appropriate for the Galactic extinction curve. Using the graphite-silicate models, we calculate the absorption and scattering optical depths, the mass-density ratio of interstellar dust to neutral hydrogen, and the Kramers-Kronig relation for all three galaxies. We also present a fitting function for the three extinction curves, valid not only over the observed range of wavelengths but also over the full range as predicted by the models. All the quantities we derived here are independent of the dust-to-gas ratios in the Milky Way and the Magellanic Clouds, and can be applied to other galaxies if they contain Galactic or Magellanic-type dust.

Pei, Yichuan C.↗
NASA NTRS1989

Molecules in an infrared cirrus cloud

One of the clouds that form the Polar Loop was observed in the 1(sub 10)-1(sub 11) 4.8 GHz transition of formaldehyde and in J equal to 1-0 transitions of CO-12 and CO-13 at 115 and 110 GHz resp. The cloud consists of several filaments. From the correlation of IRAS 60 and 100 microns intensities a color temperature of the dust of 21 K and a maximum optical depth of 3 x 10(exp -4) were derived. At one local maximum of the 100 micron intensity, the hyperfine structure of formaldehyde could be resolved. Since the infrared optical depth is small, the 100 micron intensity can be used as a measure of dust column density.

Meyerdierks, Horst↗
NASA NTRS1992

High-phase-angle observations of Neptune at 2650 and 7500 A - Haze structure and particle properties

An analysis is conducted of spatially resolved Voyager 2 Photopolarimeter Subsystem (PPS) observations at 2650 and 7500 A. The continuum absorber that is tropospherically abundant, if confined to the region below the methane haze layer, indicates an optical depth for that layer no greater than 0.8; models in which this optical depth is as large as 3.0 yield too much limb darkening, in the case where the continuum absorber is mixed with both the methane haze and deeper clouds. Tropospheric aerosols are noted to have phase functions with shallow backward lobes.

Pryor, Wayne R.↗
NASA NTRS1999

Current Status of Aerosol Retrievals from TOMS

Properties of atmospheric aerosols over all land and water surfaces are retrieved from TOMS measurements of backscattered radiances. The TOMS technique, uses observations at two wavelengths. In the near ultraviolet (330-380 nm) range, where the effects of gaseous absorption are negligible. The retrieved properties are optical depth and a measure of aerosol absorptivity, generally expressed as single scattering albedo. The main sources of error of the TOMS aerosol products are sub-pixel cloud contamination and uncertainty on the height above the surface of UV-absorbing aerosol layers. The first error source is related to the large footprint (50 x 50 km at nadir) of the sensor, and the lack of detection capability of sub-pixel size clouds. The uncertainty associated with the height of the absorbing aerosol layers, on the other hand, is related to the pressure dependence of the molecular scattering process, which is the basis of the near-UV method of absorbing aerosol detection. The detection of non-absorbing aerosols is not sensitive to aerosol layer height. We will report on the ongoing work to overcome both of these difficulties. Coincident measurements of high spatial resolution thermal infrared radiances are used to address the cloud contamination issue. Mostly clear scenes for aerosol retrieval are selected by examining the spatial homogeneity of the IR radiance measurements within a TOMS pixel. The approach to reduce the uncertainty associated with the height of the aerosol layer by making use of a chemical transport model will also be discussed.

Torres, O.↗
NASA NTRS2003

Investigation of Overlap Correction Techniques for Application in the Micro-Pulse Lidar Network (MPLNET)

The Micro-Pulse Lidar NETwork (MPLNET) is comprised of micro-pulse lidars (MPL) stationed around the globe to provide measurements of aerosol and cloud vertical distribution on a continuous basis. MPLNET sites are co-located with sunphotometers in the AErosol Robotic NETwork (AERONET) to provide joint measurements of aerosol optical depth, size, and other inherent optical properties. The IPCC 2001 report discusses . the importance of obtaining routine measurements of aerosol vertical structure, especially for absorbing aerosols. MPLNET provides exactly this sort of measurement, including calculation of aerosol extinction profiles, in a near real-time basis for all sites in the network. In order to obtain aerosol profiles, near range signal returns (0-6 km) must be accurately measured by the MPL. This measurement is complicated by the instrument s overlap range: Le., the minimum distance at which returning signals are completely in the instrument s field-of-view (FOV). Typical MPL overlap distances are large, between 5 - 6 km, due to the narrow FOV of the MPL receiver. A function describing the MPL overlap must be determined and used to correct signals in this range. Currently, overlap functions for MPLNET are determined using horizontal MPL measurements along a path with 10-1 5 km clear line-of-sight and a homogenous atmosphere. These conditions limit the location and ease in which successful overlaps can be obtained. Furthermore, the current MPLNET process of correcting for overlap increases the uncertainty and bias error for the near range signals and the resulting aerosol extinction profiles. To address these issues, an alternative overlap correction method using a small-diameter, wide FOV receiver is being considered for potential use in MPLNET. The wide FOV receiver has a much shorter overlap distance and will be used to calculate the overlap function of the MPL receiver. This approach has a significant benefit in that overlap corrections could be obtained without the need for horizontal measurements. A review of both overlap methods is presented, including a discussion of the impact on reducing the uncertainty and bias error in MPLNET aerosol profiles.

Berkoff, Timothy A.↗
NASA NTRS2015

Retrieving the Height of Smoke and Dust Aerosols by Synergistic Use of VIIRS, OMPS, and CALIOP Observations

Aerosol Single scattering albedo and Height Estimation (ASHE) algorithm was first introduced in Jeong and Hsu (2008) to provide aerosol layer height as well as single scattering albedo (SSA) for biomass burning smoke aerosols. One of the advantages of this algorithm was that the aerosol layer height can be retrieved over broad areas, which had not been available from lidar observations only. The algorithm utilized aerosol properties from three different satellite sensors, i.e., aerosol optical depth (AOD) and Ångström exponent (AE) from Moderate Resolution Imaging Spectroradiometer (MODIS), UV aerosol index (UVAI) from Ozone Monitoring Instrument (OMI), and aerosol layer height from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Here, we extend the application of the algorithm to Visible Infrared Imaging Radiometer Suite (VIIRS) and Ozone Mapping and Profiler Suite (OMPS) data. We also now include dust layers as well as smoke. Other updates include improvements in retrieving the AOD of nonspherical dust from VIIRS, better determination of the aerosol layer height from CALIOP, and more realistic input aerosol profiles in the forward model for better accuracy.

aerosol↗