scholarly journals Monitoring of snow surface near-infrared bidirectional reflectance factors with added light-absorbing particles

2019 ◽  
Vol 13 (6) ◽  
pp. 1753-1766 ◽  
Author(s):  
Adam Schneider ◽  
Mark Flanner ◽  
Roger De Roo ◽  
Alden Adolph
Keyword(s):  
Near Infrared ◽  
Bidirectional Reflectance ◽  
Nondestructive Technique ◽  
Snow Albedo ◽  
Considerable Uncertainty ◽  
Clear Sky ◽  
Surface Areas ◽  
Microphysical Properties ◽  
Sky Conditions

Abstract. Broadband snow albedo can range from 0.3 to 0.9 depending on microphysical properties and light-absorbing particle (LAP) concentrations. Beyond the widely observed direct and visibly apparent effect of darkening snow, it is still unclear how LAPs influence snow albedo feedbacks. To investigate LAPs' indirect effect on snow albedo feedbacks, we developed and calibrated the Near-Infrared Emitting and Reflectance-Monitoring Dome (NERD) and monitored bidirectional reflectance factors (BRFs) hourly after depositing dust and black carbon (BC) particles onto experimental snow surfaces. After comparing snow infrared BRFs to snow specific surface areas (SSAs), we found that both measured and modeled snow infrared BRFs are correlated with snow SSA. These results, however, demonstrate a considerable uncertainty of ±10 m2 kg−1 in the determination of snow SSA from our BRF measurements. The nondestructive technique for snow SSA retrieval that we present here can be further developed for science applications that require rapid in situ snow SSA measurements. After adding large amounts of dust and BC to snow, we found more rapid decreasing of snow BRFs and SSAs in snow with added LAPs compared to natural (clean) snow but only during clear-sky conditions. These results suggest that deposition of LAPs onto snow can accelerate snow metamorphism via a net positive snow grain-size feedback.

scholarly journals Multispectral information from TANSO-FTS instrument – Part 2: Application to aerosol effect on greenhouse gas retrievals

2013 ◽  
Vol 6 (11) ◽  
pp. 3313-3323 ◽  
Author(s):  
H. Herbin ◽  
L. C. Labonnote ◽  
P. Dubuisson
Keyword(s):  
Greenhouse Gas ◽  
Near Infrared ◽  
Computation Time ◽  
Channel Selection ◽  
Atmospheric Parameter ◽  
Aerosol Layer ◽  
Clear Sky ◽  
Aerosol Parameters ◽  
Similar Accuracy ◽  
Sky Conditions

Abstract. This article is the second in a series of studies investigating the benefits of multispectral measurements to improve the atmospheric parameter retrievals. In the first paper, we presented an information content (IC) analysis from the thermal infrared (TIR) and shortwave infrared (SWIR) bands of Thermal And Near infrared Sensor for carbon Observations–Fourier Transform Spectrometer (TANSO-FTS) instrument dedicated to greenhouse gas retrieval in clear sky conditions. This second paper presents the potential of the spectral synergy from TIR to visible for aerosol characterization, and their impact on the retrieved CO2 and CH4 column concentrations. The IC is then used to determine the most informative spectral channels for the simultaneous retrieval of greenhouse gas total columns and aerosol parameters. The results show that a channel selection spanning the four bands can improve the computation time and retrieval accuracy. Therefore, the spectral synergy allows obtaining up to almost seven different aerosol parameters, which is comparable to the most informative dedicated instruments. Moreover, a channel selection from the TIR to visible bands allows retrieving CO2 and CH4 total columns simultaneously in the presence of one aerosol layer with a similar accuracy to using all channels together to retrieve each gas separately in clear sky conditions.

scholarly journals Assessment of Sun photometer Langley calibration at the high-elevation sites Mauna Loa and Izaña

2018 ◽  
Vol 18 (19) ◽  
pp. 14555-14567 ◽  
Author(s):  
Carlos Toledano ◽  
Ramiro González ◽  
David Fuertes ◽  
Emilio Cuevas ◽  
Thomas F. Eck ◽  
...  
Keyword(s):  
Near Infrared ◽  
Quality Criteria ◽  
High Elevation ◽  
High Mountain ◽  
Atmospheric Variability ◽  
Mauna Loa ◽  
Clear Sky ◽  
Calibration Uncertainty ◽  
Infrared Wavelengths

Abstract. The aim of this paper is to analyze the suitability of the high-mountain stations Mauna Loa and Izaña for Langley plot calibration of Sun photometers. Thus the aerosol optical depth (AOD) characteristics and seasonality, as well as the cloudiness, have been investigated in order to provide a robust estimation of the calibration uncertainty as well as the number of days that are suitable for Langley calibrations. The data used for the investigations belong to the AERONET and GAW-PFR networks, which maintain reference Sun photometers at these stations with long measurement records: 22 years at Mauna Loa and 15 years at Izaña. In terms of clear-sky and stable aerosol conditions, Mauna Loa (3397 m a.s.l.) exhibits on average 377 Langley plots (243 morning and 134 afternoon) per year suitable for Langley plot calibration, whereas Izaña (2373 m a.s.l.) shows 343 Langley plots (187 morning and 155 afternoon) per year. The background AOD (500 nm) values, on days that are favorable for Langley calibrations, are in the range 0.01–0.02 throughout the year, with well-defined seasonality that exhibits a spring maximum at both stations plus a slight summer increase at Izaña. The statistical analysis of the long-term determination of extraterrestrial signals yields to a calibration uncertainty of ∼ 0.25–0.5 %, this uncertainty being smaller in the visible and near-infrared wavelengths and larger in the ultraviolet wavelengths. This is due to atmospheric variability produced by changes in several factors, mainly the AOD. The uncertainty cannot be reduced based only on quality criteria of individual Langley plots and averaging over several days is shown to reduce the uncertainty to the needed levels for reference Sun photometers.

scholarly journals Assessment of Sun photometer Langley calibration at the high-elevation sites Mauna Loa and Izaña

2018 ◽  
Author(s):  
Carlos Toledano ◽  
Ramiro González ◽  
David Fuertes ◽  
Emilio Cuevas ◽  
Thomas F. Eck ◽  
...  
Keyword(s):  
Near Infrared ◽  
Quality Criteria ◽  
High Elevation ◽  
High Mountain ◽  
Atmospheric Variability ◽  
Mauna Loa ◽  
Clear Sky ◽  
Calibration Uncertainty

Abstract. The aim of this paper is to analyze the suitability of the high-mountain stations Mauna Loa and Izaña for Langley plot calibration of Sun photometers. Thus the aerosol optical depth (AOD) characteristics and seasonality, as well as the cloudiness, have been investigated in order to provide a robust estimation of the calibration accuracy, as well as the number of days that are suitable for Langley calibrations. The data used for the investigations belong to AERONET and GAW-PFR networks, which maintain reference Sun photometers at these stations with long measurement records: 22 years at Mauna Loa and 15 years at Izaña. In terms of clear sky and stable aerosol conditions, Mauna Loa (3397 m a.s.l.) exhibits on average of 377 Langleys (243 morning and 134 afternoon) per year suitable for Langley plot calibration, whereas Izaña (2373 m a.s.l.) shows 343 Langleys (187 morning and 155 afternoon) per year. The background AOD (500 nm wavelength) values, on days that are favorable for Langley calibrations, are in the range 0.01–0.02 throughout the year, with well-defined seasonality that exhibits a spring maximum at both stations plus a slight summer increase at Izaña. The statistical analysis of the long-term determination of extraterrestrial signals yields to a calibration uncertainty of ~ 0.2–0.5 %, being this uncertainty smaller in the near infrared and larger in the ultraviolet wavelengths. This is due to atmospheric variability that cannot be reduced based only on quality criteria of individual Langely plots.

scholarly journals Model-aided radiometric determination of photolysis frequencies in a sunlit atmosphere simulation chamber

2005 ◽  
Vol 5 (1) ◽  
pp. 191-206 ◽  
Author(s):  
B. Bohn ◽  
H. Zilken
Keyword(s):  
Time Dependent ◽  
Clear Sky ◽  
Photolysis Frequencies ◽  
Model Predictions ◽  
Complex Construction ◽  
Sky Conditions ◽  
Atmosphere Simulation Chamber ◽  
Radiometric Determination ◽  
Simulation Chamber

Abstract. In this work diurnal and seasonal variations of mean photolysis frequencies for the atmosphere simulation chamber SAPHIR at Forschungszentrum Jülich are calculated. SAPHIR has a complex construction with UV permeable teflon walls allowing natural sunlight to enter the reactor volume. The calculations are based on external measurements of solar spectral actinic flux and a model considering the time-dependent impact of shadows from construction elements as well as the influence of the teflon walls. Overcast and clear-sky conditions are treated in a consistent way and different assumptions concerning diffuse sky radiance distributions are tested. Radiometric measurements inside the chamber are used for an inspection of model predictions. Under overcast conditions we obtain fractions of 0.74 and 0.67 of external values for photolysis frequencies j(NO2) (NO2+hν→NO+O(3P)) and j(O1D) (O3+hν→O2+O(1D)), respectively. On a clear sky summer day these values are time-dependent within ranges 0.65-0.86 and 0.60-0.73, for j(NO2) and j(O1D), respectively. A succeeding paper (Bohn et al., 2004) is dealing with an on-road test of the model approach by comparison with photolysis frequencies from chemical actinometry experiments within SAPHIR.

scholarly journals Capability of multi-viewing-angle photo-polarimetric measurements for the simultaneous retrieval of aerosol and cloud properties

2010 ◽  
Vol 3 (4) ◽  
pp. 839-851 ◽  
Author(s):  
O. P. Hasekamp
Keyword(s):  
Satellite Remote Sensing ◽  
Essential Role ◽  
High Accuracy ◽  
Aerosol Layer ◽  
Viewing Angle ◽  
Clear Sky ◽  
Microphysical Properties ◽  
Cloud Properties ◽  
Land Surfaces ◽  
Sky Conditions

Abstract. An important new challenge in the field of multi-angle photo-polarimetric satellite remote sensing is the retrieval of aerosol properties under cloudy conditions. In this paper the possibility has been explored to perform a simultaneous retrieval of aerosol and cloud properties for partly cloudy scenes and for fully cloudy scenes where the aerosol layer is located above the cloud, using multi-angle photo-polarimetric measurements. Also, for clear sky conditions a review is given of the capabilities of multi-angle photo-polarimetric measurements in comparison with other measurement types. It is shown that already for clear sky conditions polarization measurements are highly important for the retrieval of aerosol optical and microphysical properties over land surfaces with unknown reflection properties. Furthermore, it is shown that multi-angle photo-polarimetric measurements have the capability to distinguish between aerosols and clouds, and thus facilitate a simultaneous retrieval of aerosol and cloud properties. High accuracy (0.002–0.004) of the polarimetric measurements plays an essential role here.

scholarly journals Capability of multi-viewing-angle photo-polarimetric measurements for the simultaneous retrieval of aerosol and cloud properties

2010 ◽  
Vol 3 (2) ◽  
pp. 1229-1262 ◽  
Author(s):  
O. P. Hasekamp
Keyword(s):  
Satellite Remote Sensing ◽  
Essential Role ◽  
High Accuracy ◽  
Aerosol Layer ◽  
Viewing Angle ◽  
Clear Sky ◽  
Microphysical Properties ◽  
Cloud Properties ◽  
Land Surfaces ◽  
Sky Conditions

Abstract. An important new challenge in the field of multi-angle photopolarimetric satellite remote sensing is the retrieval of aerosol properties under cloudy conditions. In this paper the possibility has been explored to perform a simultaneous retrieval of aerosol and cloud properties for partly cloudy scenes and for fully cloudy scenes where the aerosol layer is located above the cloud, using multi-angle photo-polarimetric measurements. Also, for clear sky conditions a review is given of the capabilities of multi-angle photo-polarimetric measurements in comparison with other measurement types. It is shown that already for clear sky conditions polarization measurements are highly important for the retrieval of aerosol optical and microphysical properties over land surfaces with unknown reflection properties. Furthermore, it is shown that multi-angle photo-polarimetric measurements have the capability to distinguish between aerosols and clouds, and thus facilitate a simultaneous retrieval of aerosol and cloud properties. High accuracy (0.002–0.004) of the polarimetric measurements plays an essential role here.

NIRS determination of carbohydrates from hydrothermal-treated rice straw

TAPPI Journal ◽  
2012 ◽  
Vol 11 (4) ◽  
pp. 27-32 ◽  
Author(s):  
ANA MORAL ◽  
MARIA DOLORES HERNÁNDEZ ◽  
ANTONIO TIJERO ◽  
ZOILO GONZÁLEZ ◽  
JUAN GARCÍA ◽  
...  
Keyword(s):  
Rice Straw ◽  
High Performance ◽  
Near Infrared ◽  
Hydrothermal Process ◽  
Prediction Method ◽  
Raw Material ◽  
Nondestructive Technique ◽  
Paper Mills ◽  
Additional Advantage

Increasingly stringent environmental standards and the need for sustainable development are forcing pulp and paper mills to study methods to maximize the use of process wastes. Several studies have shown that “hydrothermal process” wastes might serve as raw material to obtain monosaccharides and oligosaccharides. High-performance liquid chromatography (HPLC) traditionally has been used to study these carbohydrates. However, HPLC has a series of disadvantages that could be avoided by use of other methods. This study evaluated the potential use of near infrared spectroscopy (NIRS) as a substitute analysis method for HPLC, using rice straw as raw material. The results showed that NIRS analysis can be used as a prediction method for monosaccharides and oligosaccharides. This method has the additional advantage of being a fast, nondestructive technique that does not require pretreatment of samples, and therefore, decreases the costs and the environmental impact of the analyses process.

Evaluation of the Snow Albedo Retrieved from the Snow Kernel Improved the Ross-Roujean BRDF Model

2019 ◽  
Vol 11 (13) ◽  
pp. 1611 ◽  
Author(s):  
Ding ◽  
Jiao ◽  
Dong ◽  
Zhang ◽  
Peltoniemi ◽  
...  
Keyword(s):  
Near Infrared ◽  
Forward Direction ◽  
Surface Scattering ◽  
Bidirectional Reflectance Distribution Function ◽  
Model Framework ◽  
Bidirectional Reflectance ◽  
Snow Albedo ◽  
Simulation Results ◽  
Improved Model ◽  
Bidirectional Reflectance Distribution

The original kernel-driven bidirectional reflectance distribution function (BRDF) models were developed based on soil-vegetation systems. To further improve the ability of the models to characterize the snow surface scattering properties, a snow kernel was derived from the asymptotic radiative transfer (ART) model and used in the kernel-driven BRDF model framework. However, there is a need to further evaluate the influence of using this snow kernel to improve the original kernel-driven models in snow albedo retrieval applications. The aim of this study is to perform such an evaluation using a variety of snow BRDF data. The RossThick-Roujean (RTR) model is used as a framework for taking in the new snow kernel (hereafter named the RTS model) since the Roujean geometric-optical (GO) kernel captures a neglectable hotspot effect and represents a more prominent dome-shaped BRDF, especially at a small solar zenith angle (SZA). We obtained the following results: (1) The RTR model has difficulties in reconstructing the snow BRDF shape, especially at large SZAs, which tends to underestimate the reflectance in the forward direction and overestimate reflectance in the backward direction for various data sources. In comparison, the RTS model performs very well in fitting snow BRDF data and shows high accuracy for all data. (2) The RTR model retrieved snow albedos at SZAs = 30°–70° are underestimated by 0.71% and 0.69% in the red and near-infrared (NIR) bands, respectively, compared with the simulation results of the bicontinuous photon tracking (bic-PT) model, which serve as “real” values. However, the albedo retrieved by the RTS model is significantly improved and generally agrees well with the simulation results of the bic-PT model, although the improved model still somewhat underestimates the albedo by 0.01% in the red band and overestimates the albedo by 0.05% in the NIR band, respectively, at SZAs = 30°–70°, which may be negligible. (3) The albedo derived by these two models shows a high correlation (R2 > 0.9) between the field-measured and Polarization and Directionality of the Earth's Reflectances (POLDER) data, especially for the black-sky albedo. However, the albedo derived using the RTR model is significantly underestimated compared with the RTS model. The RTR model underestimates the black-sky albedo (white-sky albedo) retrievals by 0.62% (1.51%) and 0.93% (2.08%) in the red and NIR bands, respectively, for the field-measured data. The shortwave black-sky and white-sky albedos derived using the RTR model for the POLDER data are underestimated by 1.43% and 1.54%, respectively, compared with the RTS model. These results indicate that the snow kernel in the kernel-driven BRDF model frame is more accurate in snow albedo retrievals and has the potential for application in the field of the regional and global energy budget.

scholarly journals Measuring Landscape Albedo Using Unmanned Aerial Vehicles

2018 ◽  
Vol 10 (11) ◽  
pp. 1812 ◽  
Author(s):  
Chang Cao ◽  
Xuhui Lee ◽  
Joseph Muhlhausen ◽  
Laurent Bonneau ◽  
Jiaping Xu
Keyword(s):  
Unmanned Aerial Vehicles ◽  
Surface Albedo ◽  
Near Infrared ◽  
Surface Energy Balance ◽  
Landsat Image ◽  
Local Climate ◽  
Clear Sky ◽  
Aerial Vehicles ◽  
Albedo Change ◽  
Sky Conditions

Surface albedo is a critical parameter in surface energy balance, and albedo change is an important driver of changes in local climate. In this study, we developed a workflow for landscape albedo estimation using images acquired with a consumer-grade camera on board unmanned aerial vehicles (UAVs). Flight experiments were conducted at two sites in Connecticut, USA and the UAV-derived albedo was compared with the albedo obtained from a Landsat image acquired at about the same time as the UAV experiments. We find that the UAV estimate of the visibleband albedo of an urban playground (0.037 ± 0.063, mean ± standard deviation of pixel values) under clear sky conditions agrees reasonably well with the estimates based on the Landsat image (0.047 ± 0.012). However, because the cameras could only measure reflectance in three visible bands (blue, green, and red), the agreement is poor for shortwave albedo. We suggest that the deployment of a camera that is capable of detecting reflectance at a near-infrared waveband should improve the accuracy of the shortwave albedo estimation.

scholarly journals Measurement of all-wave and spectral albedos of snow-covered summer sea ice in the Ross Sea, Antarctica

2001 ◽  
Vol 33 ◽  
pp. 267-274 ◽  
Author(s):  
Xiaobing Zhou ◽  
Shusun Li ◽  
Kim Morris
Keyword(s):  
Grain Size ◽  
Near Infrared ◽  
Ross Sea ◽  
Snow Layer ◽  
Clear Sky ◽  
Pack Ice ◽  
Infrared Spectral ◽  
Size And Morphology ◽  
Ice Floes ◽  
Sky Conditions

AbstractAll-wave albedo and spectral albedo data were collected over snow-covered pack-ice floes during summer 1999 (January and February) in the Ross Sea, Antarctica. Temporal variation of the all-wave albedo and spectral albedo was measured from the northern edge to the southern edge of the pack ice along three lines of longitude: 165° W, 150° Wand 135° W. Snow depth, snow-cover stratification, snow-temperature profiles, and grain-size and morphology were also documented. It was observed that daily-averaged albedos were 0.70−0.86 for cloudy conditions over the pack ice. Only two sets of daily-averaged albedo were collected for clear-sky conditions (0.788 and 0:825). Albedo was lower at the marginal edges of the pack ice than in the central pack ice. Albedo was higher over the southern part of the central pack ice than over the northern part. Clear- and cloudy-sky albedos measured on the same site indicate that the average increase in albedo due to clouds is 1.4% (maximum 4.0%). Spectral albedos of the pack-ice floes were similar under clear-sky and cloudy conditions. Both are mainly controlled by the snow grain-size, especially in the top snow layer. All-wave albedos derived from measured visible and near-infrared spectral albedos, with extrapolation to ultraviolet and shortwave infrared regions for both clear- and cloudy-sky conditions, agreed well with all-wave albedos from direct measurements.

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