Reconciling Ground-Based and Space-Based Estimates of the Frequency of Occurrence and Radiative Effect of Clouds around Darwin, Australia

AbstractThe objective of this paper is to investigate whether estimates of the cloud frequency of occurrence and associated cloud radiative forcing as derived from ground-based and satellite active remote sensing and radiative transfer calculations can be reconciled over a well-instrumented active remote sensing site located in Darwin, Australia, despite the very different viewing geometry and instrument characteristics. It is found that the ground-based radar–lidar combination at Darwin does not detect most of the cirrus clouds above 10 km (because of limited lidar detection capability and signal obscuration by low-level clouds) and that the CloudSat radar–Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) combination underreports the hydrometeor frequency of occurrence below 2-km height because of instrument limitations at these heights. The radiative impact associated with these differences in cloud frequency of occurrence is large on the surface downwelling shortwave fluxes (ground and satellite) and the top-of-atmosphere upwelling shortwave and longwave fluxes (ground). Good agreement is found for other radiative fluxes. Large differences in radiative heating rate as derived from ground and satellite radar–lidar instruments and radiative transfer calculations are also found above 10 km (up to 0.35 K day−1 for the shortwave and 0.8 K day−1 for the longwave). Given that the ground-based and satellite estimates of cloud frequency of occurrence and radiative impact cannot be fully reconciled over Darwin, caution should be exercised when evaluating the representation of clouds and cloud–radiation interactions in large-scale models, and limitations of each set of instrumentation should be considered when interpreting model–observation differences.

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A novel methodology using MODIS and CERES for assessing the daily radiative forcing of smoke aerosols in large scale over the Amazonia

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-31515-2014 ◽

2014 ◽

Vol 14 (22) ◽

pp. 31515-31550

Author(s):

E. T. Sena ◽

P. Artaxo

Keyword(s):

Remote Sensing ◽

Spatial Distribution ◽

Radiative Transfer ◽

Biomass Burning ◽

Satellite Remote Sensing ◽

Radiative Forcing ◽

Large Scale ◽

High Temporal Resolution ◽

Modis Aod ◽

The Impact

Abstract. A new methodology was developed for obtaining daily retrievals of the direct radiative forcing of aerosols (24h-DARF) at the top of the atmosphere (TOA) using satellite remote sensing. For that, simultaneous CERES (Clouds and Earth's Radiant Energy System) shortwave flux at the top of the atmosphere (TOA) and MODIS (Moderate Resolution Spectroradiometer) aerosol optical depth (AOD) retrievals were used. This methodology is applied over a large region of Brazilian Amazonia. We focused our studies on the peak of the biomass burning season (August to September) from 2000 to 2009 to analyse the impact of forest smoke on the radiation balance. To assess the spatial distribution of the DARF, background scenes without biomass burning impacts, were defined as scenes with MODIS AOD < 0.1. The fluxes at the TOA retrieved by CERES for those clean conditions (Fcl) were estimated as a function of the illumination geometry (θ0) for each 0.5° × 0.5° grid cell. The instantaneous DARF was obtained as the difference between clean Fcl (θ0) and the polluted mean flux at the TOA measured by CERES in each cell (Fpol (θ0)). The radiative transfer code SBDART (Santa Barbara DISORT Radiative Transfer model) was used to expand instantaneous DARFs to 24 h averages. With this methodology it is possible to assess the DARF both at large scale and at high temporal resolution. This new methodology also showed to be more robust, because it considerably reduces statistical sources of uncertainties in the estimates of the DARF, when compared to previous assessments of the DARF using satellite remote sensing. The spatial distribution of the 24h-DARF shows that, for some cases, the mean 24h-DARF presents local values as high as −30 W m−2. The temporal variability of the 24h-DARF along the biomass burning season was also studied and showed large intraseasonal and interannual variability. In an attempt to validate the radiative forcing obtained in this work using CERES and MODIS, those results were compared to coincident AERONET ground based estimates of the DARF. This analysis showed that CERES-MODIS and AERONET 24h-DARF are related as DARFCERES-MODIS24 h = (1.07 ± 0.04)DARFAERONET24 h −(0.0 ± 0.6). This is a significant result, considering that the 24h-DARF retrievals were obtained by applying completely different methodologies, and using different instruments. The instantaneous CERES-MODIS DARF was also compared with radiative transfer evaluations of the forcing. To validate the aerosol and surface models used in the simulations, downward shortwave fluxes at the surface evaluated using SBDART and measured by pyranometers were compared. The simulated and measured downward fluxes are related through FBOAPYRANOMETER = (1.00 ± 0.04)FBOASBDART −(20 ± 27), indicating that the models and parameters used in the simulations were consistent. The relationship between CERES-MODIS instantaneous DARF and calculated SBDART forcing was satisfactory, with DARFCERES-MODIS = (0.86 ± 0.06)DARFSBDART −(6 ± 2). Those analysis showed a good agreement between satellite remote sensing, ground-based and radiative transfer evaluated DARF, demonstrating the robustness of the new proposed methodology for calculated radiative forcing for biomass burning aerosols. To our knowledge, this was the first time satellite remote sensing assessments of the DARF were compared with ground based DARF estimates.

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Aerosol influences on radiative heating rates in the Asian tropopause aerosol layer

10.5194/egusphere-egu21-5145 ◽

2021 ◽

Author(s):

Jie Gao ◽

Jonathon Wright

Keyword(s):

Radiative Transfer ◽

Radiative Forcing ◽

Asian Monsoon ◽

Volcanic Eruptions ◽

Radiative Heating ◽

Spatiotemporal Variability ◽

Radiation Budget ◽

Aerosol Layer ◽

Heating Rates ◽

Aerosol Analysis

The Asian Tropopause Aerosol Layer (ATAL) has emerged over recent decades to play an increasingly prominent role in the upper troposphere and lower stratosphere above the Asian monsoon region. Although the effects of the ATAL on the surface and top-of-atmosphere radiation budget have been examined by several studies, the processes and effects by which the ATAL alters radiative transfer within the tropopause layer have been much less discussed. We have used a conditional composite approach to investigate aerosol mixing ratios and their impacts on radiative heating rates in the Asian monsoon tropopause layer in MERRA-2. We have then subsampled in time based on known volcanic eruptions and the evolution of emission and data assimilation inputs to the MERRA-2 aerosol analysis to isolate the ATAL contribution and compare it to radiative heating signatures in the monsoon anticyclone region after volcanic eruptions. The results indicate that the ATAL impact on radiative heating rates in this region is on the order of 0.1 K/day, similar to that associated with ozone variability in MERRA-2 but weaker than cloud radiative effects at these altitudes. We have validated these results and tested their sensitivity to variations in the vertical structure and composition of ATAL aerosols using offline radiative transfer simulations. The idealized simulations produce similar but slightly stronger responses of radiative heating rates to the ATAL and are in good agreement with previous estimates of the top-of-atmosphere radiative forcing. Although the ATAL perturbations inferred from MERRA-2 are only about 10% of mean heating rates at these levels, their spatial distribution suggests potential implications for both isentropic and diabatic transport within the monsoon anticyclone, which should be examined in future work. Our results are limited by uncertainties in the composition and spatiotemporal variability of the ATAL, and reflect only the conditions in this layer as represented by MERRA-2. Targeted observations and model simulations are needed to adequately constrain the uncertainties, particularly with respect to the relative proportions and contributions of nitrate aerosols, which are not included in the MERRA-2 aerosol analysis.

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LESS: Large-scale remote sensing data and image simulation framework over Vegetated Areas

10.5194/egusphere-egu2020-21412 ◽

2020 ◽

Author(s):

Jianbo Qi ◽

Donghui Xie

Keyword(s):

Remote Sensing ◽

Radiative Transfer ◽

Large Scale ◽

Computational Cost ◽

Field Measurements ◽

Airborne Lidar ◽

Graphic User Interface ◽

Inversion Algorithm ◽

Modeling Framework ◽

Tracing Method

Three-dimensional (3D) radiative transfer (RT) modeling and simulation of the transport of radiation through earth surfaces is a challenging and difficult task. The difficulties lie in the complexity of the landscapes and also the intensive computational cost of 3D RT simulations. Current models usually work with abstract landscape elements to reduce complexity or only consider relatively small realistic scenes. In this study, a new 3D RT modeling framework (called LESS) is proposed. It employs a forward photon tracing method to simulate bidirectional reflectance factor (BRF) or flux-related data (e.g., downwelling radiation) and a backward path tracing method to generate sensor images (e.g., fisheye images) or large-scale (e.g. 1 km2) spectral images from visible to thermal infrared band. In this framework, a graphic user interface (GUI) and a set of tools are also provided to help to construct the landscape and set parameters, e.g., extracting tree crowns from airborne LiDAR data, which makes it more accessible to common users. The accuracy of LESS is evaluated with other models and field measurements in terms of directional BRF and pixel-wise comparisons. It shows that the accuracy of LESS is consistent with the reference models from RAMI model inter-comparison website (http://rami-benchmark.jrc.ec.europa.eu/HTML/Home.php) as well as field measurements. LESS has also been extended to simulate atmosphere, LiDAR and in-situ sensors. It provides as a useful tool for studying the radiative transfer process over complex forest canopies from leaf to canopy scales. The simulated datasets can be used as benchmarks for validating other physical remote sensing inversion algorithm and developing parameterized models for retrieving bio-geophysical variables of canopy. LESS can be accessed from http://lessrt.org.

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The libRadtran software package for radiative transfer calculations (Version 2.0)

Geoscientific Model Development Discussions ◽

10.5194/gmdd-8-10237-2015 ◽

2015 ◽

Vol 8 (12) ◽

pp. 10237-10303 ◽

Cited By ~ 15

Author(s):

C. Emde ◽

R. Buras-Schnell ◽

A. Kylling ◽

B. Mayer ◽

J. Gasteiger ◽

...

Keyword(s):

Remote Sensing ◽

Radiative Transfer ◽

Software Package ◽

Radiative Forcing ◽

Gas Absorption ◽

Molecular Gas ◽

Photolysis Frequencies ◽

Aerosol Scattering ◽

Version 2.0 ◽

Climate Studies

Abstract. libRadtran is a widely used software package for radiative transfer calculations. It allows to compute (polarized) radiances, irradiances, and actinic fluxes in the solar and thermal spectral regions. libRadtran has been used for various applications, including remote sensing of clouds, aerosols and trace gases in the Earth's atmosphere, climate studies, e.g., for the calculation of radiative forcing due to different atmospheric components, for UV-forcasting, the calculation of photolysis frequencies, and for remote sensing of other planets in our solar system. The package has been described in Mayer and Kylling (2005).. Since then several new features have been included, for example polarization, Raman scattering, a new molecular gas absorption parameterization, and several new cloud and aerosol scattering parameterizations. Furthermore a graphical user interface is now available which greatly simplifies the usage of the model, especially for new users. This paper gives an overview of libRadtran version 2.0 with focus on new features. A complete description of libRadtran and all its input options is given in the user manual included in the libRadtran software package, which is freely available at http://www.libradtran.org.

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A novel methodology for large-scale daily assessment of the direct radiative forcing of smoke aerosols

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-5471-2015 ◽

2015 ◽

Vol 15 (10) ◽

pp. 5471-5483 ◽

Cited By ~ 7

Author(s):

E. T. Sena ◽

P. Artaxo

Keyword(s):

Remote Sensing ◽

Spatial Distribution ◽

Radiative Transfer ◽

Biomass Burning ◽

Satellite Remote Sensing ◽

Radiative Forcing ◽

High Temporal Resolution ◽

Radiation Balance ◽

Direct Radiative Forcing ◽

The Impact

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Seasonal Variation of Cloud Systems over ARM SGP

Journal of the Atmospheric Sciences ◽

10.1175/2007jas2394.1 ◽

2008 ◽

Vol 65 (7) ◽

pp. 2107-2129 ◽

Cited By ~ 10

Author(s):

Xiaoqing Wu ◽

Sunwook Park ◽

Qilong Min

Keyword(s):

Liquid Water ◽

Radiative Forcing ◽

General Circulation ◽

Large Scale ◽

General Circulation Models ◽

Heat Fluxes ◽

Radiative Heating ◽

Dominant Factor ◽

Cloud Systems ◽

Second Peak

Abstract Increased observational analyses provide a unique opportunity to perform years-long cloud-resolving model (CRM) simulations and generate long-term cloud properties that are very much in demand for improving the representation of clouds in general circulation models (GCMs). A year 2000 CRM simulation is presented here using the variationally constrained mesoscale analysis and surface measurements. The year-long (3 January–31 December 2000) CRM surface precipitation is highly correlated with the Atmospheric Radiation Measurement (ARM) observations with a correlation coefficient of 0.97. The large-scale forcing is the dominant factor responsible for producing the precipitation in summer, spring, and fall, but the surface heat fluxes play a more important role during winter when the forcing is weak. The CRM-simulated year-long cloud liquid water path and cloud (liquid and ice) optical depth are also in good agreement (correlation coefficients of 0.73 and 0.64, respectively) with the ARM retrievals over the Southern Great Plains (SGP). The simulated cloud systems have 50% more ice water than liquid water in the annual mean. The vertical distributions of ice and liquid water have a single peak during spring (March–May) and summer (June–August), but a second peak occurs near the surface during winter (December–February) and fall (September–November). The impacts of seasonally varied cloud water are very much reflected in the cloud radiative forcing at the top-of-atmosphere (TOA) and the surface, as well as in the vertical profiles of radiative heating rates. The cloudy-sky total (shortwave and longwave) radiative heating profile shows a dipole pattern (cooling above and warming below) during spring and summer, while a second peak of cloud radiative cooling appears near the surface during winter and fall.

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Sensitivity of surface temperature to radiative forcing by contrail cirrus in a radiative-mixing model

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-13833-2017 ◽

2017 ◽

Vol 17 (22) ◽

pp. 13833-13848 ◽

Cited By ~ 7

Author(s):

Ulrich Schumann ◽

Bernhard Mayer

Keyword(s):

Surface Temperature ◽

Temperature Sensitivity ◽

Radiative Forcing ◽

Large Scale ◽

Energy Transport ◽

Vertical Component ◽

Circulation Model ◽

Surface Energy Budget ◽

Radiative Heating ◽

Surface Warming

Abstract. Earth's surface temperature sensitivity to radiative forcing (RF) by contrail cirrus and the related RF efficacy relative to CO2 are investigated in a one-dimensional idealized model of the atmosphere. The model includes energy transport by shortwave (SW) and longwave (LW) radiation and by mixing in an otherwise fixed reference atmosphere (no other feedbacks). Mixing includes convective adjustment and turbulent diffusion, where the latter is related to the vertical component of mixing by large-scale eddies. The conceptual study shows that the surface temperature sensitivity to given contrail RF depends strongly on the timescales of energy transport by mixing and radiation. The timescales are derived for steady layered heating (ghost forcing) and for a transient contrail cirrus case. The radiative timescales are shortest at the surface and shorter in the troposphere than in the mid-stratosphere. Without mixing, a large part of the energy induced into the upper troposphere by radiation due to contrails or similar disturbances gets lost to space before it can contribute to surface warming. Because of the different radiative forcing at the surface and at top of atmosphere (TOA) and different radiative heating rate profiles in the troposphere, the local surface temperature sensitivity to stratosphere-adjusted RF is larger for SW than for LW contrail forcing. Without mixing, the surface energy budget is more important for surface warming than the TOA budget. Hence, surface warming by contrails is smaller than suggested by the net RF at TOA. For zero mixing, cooling by contrails cannot be excluded. This may in part explain low efficacy values for contrails found in previous global circulation model studies. Possible implications of this study are discussed. Since the results of this study are model dependent, they should be tested with a comprehensive climate model in the future.

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A Multisensor Perspective on the Radiative Impacts of Clouds and Aerosols

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-12-025.1 ◽

2013 ◽

Vol 52 (4) ◽

pp. 853-871 ◽

Cited By ~ 112

Author(s):

David S. Henderson ◽

Tristan L’Ecuyer ◽

Graeme Stephens ◽

Phil Partain ◽

Miho Sekiguchi

Keyword(s):

Radiant Energy ◽

Close Correlation ◽

Energy System ◽

Liquid Water Content ◽

Radiative Heating ◽

Orthogonal Polarization ◽

Radiative Effect ◽

Heating Rates ◽

Radiative Fluxes ◽

Aerosol Forcing

AbstractThe launch of CloudSat and Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) in 2006 provided the first opportunity to incorporate information about the vertical distribution of cloud and aerosols directly into global estimates of atmospheric radiative heating. Vertical profiles of radar and lidar backscatter from CloudSat’s Cloud Profiling Radar (CPR) and the Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard CALIPSO naturally complement Moderate Resolution Imaging Spectroradiometer (MODIS) radiance measurements, providing a nearly complete depiction of the cloud and aerosol properties that are essential for deriving high-vertical-resolution profiles of longwave (LW) and shortwave (SW) radiative fluxes and heating rates throughout the atmosphere. This study describes a new approach for combining vertical cloud and aerosol information from CloudSat and CALIPSO with MODIS data to assess impacts of clouds and aerosols on top-of-atmosphere (TOA) and surface radiative fluxes. The resulting multisensor cloud–aerosol product is used to document seasonal and annual mean distributions of cloud and aerosol forcing globally from June 2006 through April 2011. Direct comparisons with Clouds and the Earth’s Radiant Energy System (CERES) TOA fluxes exhibit a close correlation, with improved errors relative to CloudSat-only products. Sensitivity studies suggest that remaining uncertainties in SW fluxes are dominated by uncertainties in CloudSat liquid water content estimates and that the largest sources of LW flux uncertainty are prescribed surface temperature and lower-tropospheric humidity. Globally and annually averaged net TOA cloud radiative effect is found to be −18.1 W m−2. The global, annual mean aerosol direct radiative effect is found to be −1.6 ± 0.5 W m−2 (−2.5 ± 0.8 W m−2 if only clear skies over the ocean are considered), which, surprisingly, is more consistent with past modeling studies than with observational estimates that were based on passive sensors.

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Impact of the Ambae, Raikoke and Ulawun eruptions in 2018-2019 on the global stratospheric aerosol layer and climate

10.5194/egusphere-egu2020-2406 ◽

2020 ◽

Author(s):

Corinna Kloss ◽

Pasquale Sellitto ◽

Bernard Legras ◽

Jean-Paul Vernier ◽

Fabrice Jégou ◽

...

Keyword(s):

Radiative Transfer ◽

Radiative Forcing ◽

Volcanic Eruptions ◽

Stratospheric Aerosol ◽

Orthogonal Polarization ◽

Transfer Model ◽

Aerosol Layer ◽

The Impact ◽

Aerosol Plume

Using a combination of satellite, ground-based and in-situ observations, and radiative transfer modelling, we quantify the impact of the most recent moderate volcanic eruptions (Ambae, Vanuatu in July 2018; Raikoke, Russia and Ulawun, New Guinea in June 2019) on the global stratospheric aerosol layer and climate.For the Ambae volcano (15&#176;S and 167&#176;E), we use the Stratospheric Aerosol and Gas Experiment III (SAGE III), the Ozone Mapping Profiler Suite (OMPS), the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Himawari geostationary satellite observations of the aerosol plume evolution following the Ambae eruption of July 2018. It is shown that the aerosol plume of the main eruption at Ambae in July 2018 was distributed throughout the global stratosphere within the global large-scale circulation (Brewer-Dobson circulation, BDC), to both hemispheres. Ground-based LiDAR observations in Gadanki, India, as well as in-situ Printed Optical Particle Spectrometer (POPS) measurements acquired during the BATAL campaign confirm a widespread perturbation of the stratospheric aerosol layer due to this eruption. Using the UVSPEC radiative transfer model, we also estimate the radiative forcing of this global stratospheric aerosol perturbation. The climate impact is shown to be comparable to that of the well-known and studied recent moderate stratospheric eruptions from Kasatochi (USA, 2008), Sarychev (Russia, 2009) and Nabro (Eritrea, 2011). Top of the atmosphere radiative forcing values between -0.45 and -0.60 W/m2, for the Ambae eruption of July 2018, are found.In a similar manner the dispersion of the aerosol plume of the Raikoke (48&#176;N and 153&#176;E) and Ulawun (5&#176;S and 151&#176;E) eruptions of June 2019 is analyzed. As both of those eruptions had a stratospheric impact and happened almost simultaneously, it is challenging to completely distinguish both events. Even though the eruptions occurred very recently, first results show that the aerosol plume of the Raikoke eruption resulted in an increase in aerosol extinction values, double as high as compared to that of the Ambae eruption. However, as the eruption occurred on higher latitudes, the main bulk of Raikoke aerosols was transported towards the northern higher latitude&#8217;s in the stratosphere within the BDC, as revealed by OMPS, SAGE III and a new detection algorithm for SO2 and sulfate aerosol using IASI (Infrared Atmospheric Sounder Interferometer). Even though the Raikoke eruption had a larger impact on the stratospheric aerosol layer, both events (the eruptions at Raikoke and Ambae) have to be considered in stratospheric aerosol budget and climate studies.

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Satellite-based radiative forcing by light-absorbing particles in snow across the Northern Hemisphere

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-269-2021 ◽

2021 ◽

Vol 21 (1) ◽

pp. 269-288

Author(s):

Jiecan Cui ◽

Tenglong Shi ◽

Yue Zhou ◽

Dongyou Wu ◽

Xin Wang ◽

...

Keyword(s):

Remote Sensing ◽

Radiative Transfer ◽

Northern Hemisphere ◽

Radiative Forcing ◽

Remote Sensing Data ◽

The Arctic ◽

Snow Albedo ◽

Moderate Resolution ◽

Moderate Resolution Imaging Spectroradiometer ◽

Earth’S Climate

Abstract. Snow is the most reflective natural surface on Earth and consequently plays an important role in Earth's climate. Light-absorbing particles (LAPs) deposited on the snow surface can effectively decrease snow albedo, resulting in positive radiative forcing. In this study, we used remote-sensing data from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) and the Snow, Ice, and Aerosol Radiative (SNICAR) model to quantify the reduction in snow albedo due to LAPs before validating and correcting the data against in situ observations. We then incorporated these corrected albedo-reduction data in the Santa Barbara DISORT (Discrete Ordinate Radiative Transfer) Atmospheric Radiative Transfer (SBDART) model to estimate Northern Hemisphere radiative forcing except for midlatitude mountains in December–May for the period 2003–2018. Our analysis reveals an average corrected reduction in snow albedo (ΔαMODIS,correctedLAPs) of ∼ 0.021 under all-sky conditions, with daily radiative forcing (RFMODIS,dailyLAPs) values of ∼ 2.9 W m−2, over land areas with complete or near-complete snow cover and with little or no vegetation above the snow in the Northern Hemisphere. We also observed significant spatial variations in ΔαMODIS,correctedLAPs and RFMODIS,dailyLAPs, with the lowest respective values (∼ 0.016 and ∼ 2.6 W m−2) occurring in the Arctic and the highest (∼ 0.11 and ∼ 12 W m−2) in northeastern China. From MODIS retrievals, we determined that the LAP content of snow accounts for 84 % and 70 % of the spatial variability in albedo reduction and radiative forcing, respectively. We also compared retrieved radiative forcing values with those of earlier studies, including local-scale observations, remote-sensing retrievals, and model-based estimates. Ultimately, estimates of radiative forcing based on satellite-retrieved data are shown to represent true conditions on both regional and global scales.

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