scholarly journals Critical surface albedo and its implications to aerosol remote sensing

2011 ◽  
Vol 4 (6) ◽  
pp. 7725-7750 ◽  
Author(s):  
F. C. Seidel ◽  
C. Popp
Keyword(s):  
Remote Sensing ◽  
Surface Albedo ◽  
Atmospheric Correction ◽  
Single Scattering ◽  
Critical Surface ◽  
Aerosol Absorption ◽  
Sensing Applications ◽  
Aerosol Remote Sensing ◽  
Absorbing Aerosols ◽  
Observation Geometry

Abstract. We analyse the critical surface albedo (CSA) and its implications to aerosol remote sensing. CSA is defined as the surface albedo, where the reflectance at top-of-atmosphere (TOA) does not depend on aerosol optical depth (AOD). AOD retrievals are therefore inaccurate at the CSA. The CSA is obtained by derivatives of the TOA reflectance with respect to AOD using a radiative transfer code. We present the CSA and the effect of surface albedo uncertainties on AOD retrieval and atmospheric correction as a function of aerosol single-scattering albedo, illumination and observation geometry, wavelength and AOD. In general, increasing aerosol absorption and increasing scattering angles lead to lower CSA. We show that the CSA also depends on AOD, which was often neglected in previous studies. The following implications to aerosol remote sensing applications were found: (i) surface albedo uncertainties result in large AOD retrieval errors, particularly close to the CSA; (ii) AOD retrievals of non-absorbing aerosols require dark surfaces, while strong absorbing aerosols can be retrieved more accurately over bright surfaces; (iii) the CSA may help to estimate aerosol absorption; and (iv) the presented sensitivity of the reflectance at TOA to AOD provides error estimations to optimise AOD retrieval algorithms.

scholarly journals Critical surface albedo and its implications to aerosol remote sensing

2012 ◽  
Vol 5 (7) ◽  
pp. 1653-1665 ◽  
Author(s):  
F. C. Seidel ◽  
C. Popp
Keyword(s):  
Remote Sensing ◽  
Surface Albedo ◽  
Atmospheric Correction ◽  
Single Scattering ◽  
Small Range ◽  
Critical Surface ◽  
Aerosol Absorption ◽  
Sensing Applications ◽  
Aerosol Remote Sensing ◽  
Absorbing Aerosols

Abstract. We analyse the critical surface albedo (CSA) and its implications to aerosol remote sensing. CSA is defined as the surface albedo where the reflectance at top-of-atmosphere (TOA) does not depend on aerosol optical depth (AOD). AOD retrievals are therefore inaccurate at the CSA. The CSA is obtained by derivatives of the TOA reflectance with respect to AOD using a radiative transfer code. We present the CSA and the effect of surface albedo uncertainties on AOD retrieval and atmospheric correction as a function of aerosol single-scattering albedo, illumination and observation geometry, wavelength and AOD. In general, increasing aerosol absorption and increasing scattering angles lead to lower CSA. In contrast to the strict definition of the CSA, we show that the CSA can also slightly depend on AOD and therefore rather represent a small range of surface albedo values. This was often neglected in previous studies. The following implications to aerosol remote sensing applications were found: (i) surface albedo uncertainties result in large AOD retrieval errors, particularly close to the CSA; (ii) AOD retrievals of weakly or non-absorbing aerosols require dark surfaces, while strongly absorbing aerosols can be retrieved more accurately over bright surfaces; (iii) the CSA may help to estimate aerosol absorption; and (iv) the presented sensitivity of the reflectance at TOA to AOD provides error estimations to optimise AOD retrieval algorithms.

scholarly journals Assessing the Potential of Geostationary Satellites for Aerosol Remote Sensing Based on Critical Surface Albedo

2019 ◽  
Vol 11 (24) ◽  
pp. 2958 ◽  
Author(s):  
Xavier Ceamanos ◽  
Suman Moparthy ◽  
Dominique Carrer ◽  
Felix C. Seidel
Keyword(s):  
Remote Sensing ◽  
Atmospheric Aerosols ◽  
Surface Albedo ◽  
Satellite Measurement ◽  
Critical Surface ◽  
Geostationary Satellites ◽  
Detection And Tracking ◽  
Aerosol Remote Sensing ◽  
The Difference ◽  
One Year

Geostationary satellites are increasingly used for the detection and tracking of atmospheric aerosols and, in particular, of the aerosol optical depth (AOD). The main advantage of these spaceborne platforms in comparison with polar orbiting satellites is their capability to observe the same region of the Earth several times per day with varying geometry. This provides a wealth of information that makes aerosol remote sensing possible when combined with the multi-spectral capabilities of the on-board imagers. Nonetheless, the suitability of geostationary observations for AOD retrieval may vary significantly depending on their spatial, spectral, and temporal characteristics. In this work, the potential of geostationary satellites was assessed based on the concept of critical surface albedo (CSA). CSA is linked to the sensitivity of each spaceborne observation to the aerosol signal, as it is defined as the value of surface albedo for which a varying AOD does not alter the satellite measurement. In this study, the sensitivity to aerosols was determined by estimating the difference between the surface albedo of the observed surface and the corresponding CSA (referred to as dCSA). The values of dCSA were calculated for one year of observations from the Meteosat Second Generation (MSG) spacecraft, based on radiative transfer simulations and information on the satellite acquisition geometry and the properties of the observed surface and aerosols. Different spectral channels from MSG and the future Meteosat Third Generation-Imager were used to study their distinct capabilities for aerosol remote sensing. Results highlight the significant but varying potential of geostationary observations across the observed Earth disk and for different time scales (i.e., diurnal, seasonal, and yearly). For example, the capability of sensing multiples times during the day is revealed to be a notable strength. Indeed, the value of dCSA often fluctuates significantly for a given day, which makes some instants of time more suitable for aerosol retrieval than others. This study determines these instants of time as well as the seasons and the sensing wavelengths that increase the chances for aerosol remote sensing thanks to the variations of dCSA. The outcomes of this work can be used for the development and refinement of AOD retrieval algorithms through the use of the concept of CSA. Furthermore, results can be extrapolated to other present-day geostationary satellites such as Himawari-8/9 and GOES-16/17.

scholarly journals Quantifying the impact of aerosol scattering on the retrieval of methane from airborne remote sensing measurements

2020 ◽  
Vol 13 (12) ◽  
pp. 6755-6769
Author(s):  
Yunxia Huang ◽  
Vijay Natraj ◽  
Zhao-Cheng Zeng ◽  
Pushkar Kopparla ◽  
Yuk L. Yung
Keyword(s):  
Remote Sensing ◽  
Surface Albedo ◽  
Single Scattering ◽  
Water Soluble ◽  
Transfer Model ◽  
Background Values ◽  
Ch4 Emissions ◽  
Aerosol Scattering ◽  
The Impact ◽  
Retrieval Bias

Abstract. As a greenhouse gas with strong global warming potential, atmospheric methane (CH4) emissions have attracted a great deal of attention. Although remote sensing measurements can provide information about CH4 sources and emissions, accurate retrieval is challenging due to the influence of atmospheric aerosol scattering. In this study, imaging spectroscopic measurements from the Airborne Visible/Infrared Imaging Spectrometer – Next Generation (AVIRIS-NG) in the shortwave infrared are used to compare two retrieval techniques – the traditional matched filter (MF) method and the optimal estimation (OE) method, which is a popular approach for trace gas retrievals. Using a numerically efficient radiative transfer model with an exact single-scattering component and a two-stream multiple-scattering component, we also simulate AVIRIS-NG measurements for different scenarios and quantify the impact of aerosol scattering in the two retrieval schemes by including aerosols in the simulations but not in the retrievals. The presence of aerosols causes an underestimation of CH4 in both the MF and OE retrievals; the biases increase with increasing surface albedo and aerosol optical depth (AOD). Aerosol types with high single-scattering albedo and low asymmetry parameter (such as water-soluble aerosols) induce large biases in the retrieval. When scattering effects are neglected, the MF method exhibits lower fractional retrieval bias compared to the OE method at high CH4 concentrations (2–5 times typical background values) and is suitable for detecting strong CH4 emissions. For an AOD value of 0.3, the fractional biases of the MF retrievals are between 1.3 % and 4.5 %, while the corresponding values for OE retrievals are in the 2.8 %–5.6 % range. On the other hand, the OE method is an optimal technique for diffuse sources (<1.5 times typical background values), showing up to 5 times smaller fractional retrieval bias (8.6 %) than the MF method (42.6 %) for the same AOD scenario. However, when aerosol scattering is significant, the OE method is superior since it provides a means to reduce biases by simultaneously retrieving AOD, surface albedo, and CH4. The results indicate that, while the MF method is good for plume detection, the OE method should be employed to quantify CH4 concentrations, especially in the presence of aerosol scattering.

scholarly journals Deriving Aerosol Absorption Properties from Solar Ultraviolet Radiation Spectral Measurements at Thessaloniki, Greece

2019 ◽  
Vol 11 (18) ◽  
pp. 2179 ◽  
Author(s):  
Ilias Fountoulakis ◽  
Athanasios Natsis ◽  
Nikolaos Siomos ◽  
Theano Drosoglou ◽  
Alkiviadis F. Bais
Keyword(s):  
Solar Spectrum ◽  
Single Scattering ◽  
Spectral Measurements ◽  
City Center ◽  
Solar Ultraviolet Radiation ◽  
Aerosol Absorption ◽  
Absorbing Aerosols ◽  
The City ◽  
Double Monochromator ◽  
Construction Works

The gap in knowledge regarding the radiative effects of aerosols in the UV region of the solar spectrum is large, mainly due to the lack of systematic measurements of the aerosol single scattering albedo (SSA) and absorption optical depth (AAOD). In the present study, spectral UV measurements performed in Thessaloniki, Greece by a double monochromator Brewer spectrophotometer in the period 1998–2017 are used for the calculation of the aforementioned optical properties. The main uncertainty factors have been described and there is an effort to quantify the overall uncertainties in SSA and AAOD. Analysis of the results suggests that the absorption by aerosols is much stronger in the UV relative to the visible. SSA follows a clear annual pattern ranging from ~0.7 in winter to ~0.85 in summer at wavelengths 320–360 nm, while AAOD peaks in summer and winter. The average AAOD for 2009–2011 is ~50% above the 2003–2006 average, possibly due to increased emissions of absorbing aerosols related to the economic crisis and the metro-railway construction works in the city center.

scholarly journals Deriving Aerosol Absorption Properties from Solar Ultraviolet Radiation Spectral Measurements at Thessaloniki, Greece

2019 ◽  
Author(s):  
Ilias Fountoulakis ◽  
Athanasios Natsis ◽  
Nikolaos Siomos ◽  
Theano Drosoglou ◽  
Alkiviadis F. Bais
Keyword(s):  
Solar Spectrum ◽  
Single Scattering ◽  
Spectral Measurements ◽  
City Center ◽  
Solar Ultraviolet Radiation ◽  
Aerosol Absorption ◽  
Brewer Spectrophotometer ◽  
Absorbing Aerosols ◽  
The City ◽  
Double Monochromator

The gap in knowledge regarding the radiative effects of aerosols in the UV region of the solar spectrum is large, mainly due to the lack of systematic measurements of the aerosol single scattering albedo (SSA) and absorption optical depth (AAOD). In the present study, spectral UV measurements performed in Thessaloniki, Greece by a double monochromator Brewer spectrophotometer in the period 1998 - 2017 are used for the calculation of the aforementioned optical properties. The main uncertainty factors have been described and there is an effort to quantify the overall uncertainties in SSA and AAOD. Analysis of the results suggests that the absorption by aerosols is much stronger in the UV relative to the visible. SSA follows a clear annual pattern ranging from ~0.7 in winter to ~0.85 in summer at wavelengths 320 &ndash; 360 nm, while AAOD peaks in summer and winter. The average AAOD for 2009 &ndash; 2011 is ~50% above the 2003 &ndash; 2006 average, possibly due to increased emissions of absorbing aerosols related to the economical crisis and the metro-railway construction works in the city center. A detailed analysis of the uncertainties in the retrieval of the SSA and the AAOD from the Brewer spectrophotometer has been also performed.

scholarly journals Multi-Satellite Retrieval of SSA using OMI-MODIS algorithm

2018 ◽  
Author(s):  
Kruthika Eswaran ◽  
Sreedharan Krishnakumari Satheesh ◽  
Jayaraman Srinivasan
Keyword(s):  
Radiative Forcing ◽  
Single Scattering ◽  
Retrieval Algorithm ◽  
Ozone Monitoring Instrument ◽  
Aerosol Composition ◽  
Aerosol Radiative Forcing ◽  
Aerosol Absorption ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Absorbing Aerosols ◽  
Aerosol Type

Abstract. Single scattering albedo (SSA) represents a unique identification of aerosol type and aerosol radiative forcing. However, SSA retrievals are highly uncertain due cloud contamination and aerosol composition. Recent improvement in the SSA retrieval algorithm has combined the superior cloud masking technique of Moderate Resolution Imaging Spectroradiometer (MODIS) and the better sensitivity of Ozone Monitoring Instrument (OMI) to aerosol absorption. The combined OMI-MODIS algorithm has been validated over a small spatial and temporal scale only. The present study validates the algorithm over global oceans for the period 2008–2012. The geographical heterogeneity in the aerosol type and concentration over the Atlantic Ocean, the Arabian Sea and the Bay of Bengal was useful to delineate the effect of aerosol type on the retrieval algorithm. We also noted that OMI overestimates SSA when absorbing aerosols were present closer to the surface. We attribute this overestimation to data discontinuity in the aerosol height climatology derived from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite. OMI uses pre-defined aerosol heights over regions where CALIPSO climatology is not present leading to overestimation of SSA. The importance of aerosol height was also studied using the Santa Barbara DISORT radiative transfer (SBDART) model. The results from the joint retrieval were validated with ground-based measurements and it was seen that OMI-MODIS SSA retrievals were better constrained than OMI only retrieval.

Detection of absorbing aerosols from ground based observations of scattered sun light

2021 ◽  
Author(s):  
Thomas Wagner ◽  
Steffen Dörner ◽  
Sebastian Donner ◽  
Steffen Beirle ◽  
Janis Puķīte ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Atmospheric Aerosols ◽  
Single Scattering ◽  
Sensor Data ◽  
Special Importance ◽  
Aerosol Composition ◽  
Early Results ◽  
Absorption Potential ◽  
Absorbing Aerosols ◽  
Sun Light

&lt;p&gt;Absorption of solar radiation by atmospheric aerosols is an important heat source in the atmosphere. The absorption potential by aerosols (usually quantified by the co single scattering albedo) can vary strongly, depending on the aerosol composition. The absorption potential can be captured by in-situ sample analyses or retrieved by remote sensing techniques (e.g. by sun/sky photometry). For a global view, advanced satellite sensors with polarization and especially multi-viewing would be required (e.g. 3MI). However, sensor data at different UV wavelengths (e.g. TOMS) already inform qualitatively on the presence of (elevated) absorbing aerosol (i.e. from mineral dust, wildfires) via the so-called UV absorbing aerosol index (UVAI).&lt;/p&gt;&lt;p&gt;In this study, we propose an UVAI similar approach for ground-based observations of scattered sun light. We first performed radiative transfer simulations. Based on these simulations we found that absorbing aerosols can indeed be identified from ground-based measurements. We could in particular show that the detection of absorbing aerosols is possible in the presence of clouds (except optical very thick clouds), which will be of special importance, because existing remote sensing measurements of the aerosol absorption are only possible for clear sky conditions.&lt;/p&gt;&lt;p&gt;We also derived the UVAI from ground based measurements during a ship cruise in April and May 2019 over the tropical Atlantic. Clearly enhanced values of the UVAI could be detected when the ship crossed air masses which were contaminated by desert dust aerosols from the Sahara.&lt;/p&gt;&lt;p&gt;We present these early results and discuss possible future improvements.&lt;/p&gt;

scholarly journals Atmospheric correction algorithm for short-wave channels of the MSU-MR device of the Meteor-M no. 2 satellite

2019 ◽  
pp. 3-12
Author(s):  
M. O. Kuchma ◽  
V. D. Bloshchinskiy
Keyword(s):  
Reference Values ◽  
Surface Albedo ◽  
Atmospheric Correction ◽  
Short Wave ◽  
Atmospheric Conditions ◽  
Correction Algorithm ◽  
Low Resolution ◽  
Scanning Device ◽  
Observation Geometry ◽  
Present Algorithm

The problem of atmospheric correction for short-wave channels of a multispectral low-resolution scanning device installed on the Meteor-M No. 2 satellite is considered. To solve the problem the existing atmospheric correction algorithms are investigated. The developed atmospheric correction algorithm is based on the use of special Look-up Tables generated by the authors. Look-up Tables contain information about reflectance of the satellite device channels for various atmospheric conditions and observation geometry. The results of atmospheric correction for the first channel of the device were verified. Verification showed a high correlation with the reference reflectance, which is the data from the EUMETSAT portal Surface Albedo Validation Sites. An additional, verification of the present algorithm was also performed with the first channel data of the AVHRR device MetOp-A satellite. The correlation of the reference values and the results of atmospheric correction of both satellite devices are comparable.

Application of Sentinel-2A/B satellites to retrieve turbidity in the Guadalquivir estuary (Southern Spain)

2021 ◽  
Author(s):  
Masuma Chowdhury ◽  
César Vilas ◽  
Stef VanBergeijk ◽  
Gabriel Navarro ◽  
Irene Laiz ◽  
...  
Keyword(s):  
Climate Change ◽  
Remote Sensing ◽  
Water Quality ◽  
Coastal Waters ◽  
Atmospheric Correction ◽  
Southern Spain ◽  
Guadalquivir Estuary ◽  
Sensing Applications ◽  
Sentinel 2A ◽  
Sentinel 2

&lt;p&gt;Application of Sentinel-2A/B satellites to retrieve turbidity in the Guadalquivir estuary (Southern Spain)&lt;/p&gt;&lt;p&gt;Due to climate change, contamination, and diverse anthropogenic effects, water quality monitoring is intensifying its importance nowadays. Remote sensing techniques are becoming an important tool, in parallel with fieldwork, for supporting the cost-effective accomplishment of water quality mapping and management. In the recent years, Sentinel-2A/B twin satellites of the European Commission Earth Observation Copernicus programme emerged as a promising way to monitor complex coastal waters with higher spatial, spectral and temporal resolution. However, atmospheric and sunglint correction for the Sentinel-2 data over the coastal and inland waters is one of the major challenges in terms of accurate water quality retrieval. This study aimed at evaluating the ACOLITE atmospheric correction processor in order to develop a regional turbidity model for the Guadalquivir estuary (southern Spain) and its adjacent coastal region using Sentinel-2 imagery at a 10 m spatial resolution. Two settings for the atmospheric correction algorithm within the ACOLITE software were applied: the standard dark spectrum fitting (DSF) and the DSF with an additional option for sunglint correction. Turbidity field data were collected for calibration/validation purposes from the monthly Guadalquivir Estuary-LTER programme by Andalusian Institute of Agricultural and Fisheries Research and Training (IFAPA) using a YSI-EXO2 multiparametric sonde for the period 2017-2020 at 2 fixed stations (Bonanza and Tarfia) sampling 4 different water masses along the estuary salinity gradient. Several regional models were evaluated using the red band (665 nm) and the red-edge bands (i.e. 704, 740, 783 nm) of the Sentinel-2 satellites. The results revealed that DSF with glint correction performs better than without glint correction, especially for this region where sunglint is a major concern during summer, affecting most of the satellite scenes. This study demonstrates the invaluable potential of the Sentinel-2A/B mission to monitor complex coastal waters even though they were not designed for aquatic remote sensing applications. This improved knowledge will be a helpful guideline and tool for the coastal managers, policy-makers, stakeholders and the scientific community for ensuring sustainable ecosystem-based coastal resource management under a global climate change scenario.&lt;/p&gt;

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