scholarly journals Light propagation, coefficient attenuation, and the depth of one optical depth in different water types

2021 ◽  
Vol 944 (1) ◽  
pp. 012047
Author(s):  
B Nababan ◽  
D Ulfah ◽  
J P Panjaitan
Keyword(s):  
Optical Depth ◽  
Light Propagation ◽  
Ocean Color ◽  
Intermediate Water ◽  
Water Types ◽  
In Situ Data ◽  
Propagation Pattern ◽  
Marine Environmental ◽  
Downwelling Irradiance

Abstract The ocean color satellite can only sense a water column up to one optical depth. However, literatur regarding the depth of one optical depth is very limited to none. This study aimed to determine light propagation, attenuation coefficient (Kd), and the depth of one optical depth in different water types. We used in situ data of downwelling irradiance (Ed) with depths taken using the instrument of submersible marine environmental radiometer (MER) in the northeastern gulf of mexico (NEGOM) in April 2000. We also used SeaWiFS data such as water leaving radience (Lw ), remote sensing refectance (Rrs), and chlorophyll-a concentration (Chla). The results showed that the light propagation pattern generally decreased with increasing depth. The reduction in light intensity with depth was very strong in the red wavelengths, lower in the green wavelengths, and the lowest in the blue wavelengths. In contrast, Kd values were generally found the lowest at the blue wavelengths, slightly increase at the purple and green wavelengths, and the highest at the red wavelengths. The depth of one optical depth in the case-1 waters was found as deep as 39.79 m (λ=475 nm), followed by intermediate water of 31.79 m (λ=475 nm), and in the case-2 waters of 16.08 m (λ=490 nm). Both Kd (490) in situ and modelled results showed a good correlation (r=0.83-0.84) and R2 values of 0.68-0.71.

scholarly journals System vicarious calibration for ocean color climate change applications: Requirements for in situ data

2015 ◽  
Vol 159 ◽  
pp. 361-369 ◽  
Author(s):  
Giuseppe Zibordi ◽  
Frédéric Mélin ◽  
Kenneth J. Voss ◽  
B. Carol Johnson ◽  
Bryan A. Franz ◽  
...  
Keyword(s):  
Climate Change ◽  
Ocean Color ◽  
Vicarious Calibration ◽  
In Situ Data

Retrieval of Aerosol Scattering and Absorption Properties from Photopolarimetric Observations over the Ocean during the CLAMS Experiment

2005 ◽  
Vol 62 (4) ◽  
pp. 1093-1117 ◽  
Author(s):  
Jacek Chowdhary ◽  
Brian Cairns ◽  
Michael I. Mishchenko ◽  
Peter V. Hobbs ◽  
Glenn F. Cota ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Optical Depth ◽  
Ocean Color ◽  
Single Scattering ◽  
Effective Radius ◽  
In Situ Measurements ◽  
Single Scattering Albedo ◽  
Spectral Variation ◽  
Sky Radiance

Abstract The extensive set of measurements performed during the Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) experiment provides a unique opportunity to evaluate aerosol retrievals over the ocean from multiangle, multispectral photometric, and polarimetric remote sensing observations by the airborne Research Scanning Polarimeter (RSP) instrument. Previous studies have shown the feasibility of retrieving particle size distributions and real refractive indices from such observations for visible wavelengths without prior knowledge of the ocean color. This work evaluates the fidelity of the aerosol retrievals using RSP measurements during the CLAMS experiment against aerosol properties derived from in situ measurements, sky radiance observations, and sun-photometer measurements, and further extends the scope of the RSP retrievals by using a priori information about the ocean color to constrain the aerosol absorption and vertical distribution. It is shown that the fine component of the aerosol observed on 17 July 2001 consisted predominantly of dirty sulfatelike particles with an extinction optical thickness of several tenths in the visible, an effective radius of 0.15 ± 0.025 μm and a single scattering albedo of 0.91 ± 0.03 at 550 nm. Analyses of the ocean color and sky radiance observations favor the lower boundary of aerosol single scattering albedo, while in situ measurements favor its upper boundary. Both analyses support the polarimetric retrievals of fine-aerosol effective radius and the consequent spectral variation in extinction optical depth. The estimated vertical distribution of this aerosol component depends on assumptions regarding the water-leaving radiances and is consistent with the top of the aerosol layer being close to the aircraft height (3500 m), with the bottom of the layer being between 2.7 km and the surface. The aerosol observed on 17 July 2001 also contained coarse-mode particles. Comparison of RSP data with sky radiance and in situ measurements suggests that this component consists of nonspherical particles with an effective radius in excess of 1 μm, and with the extinction optical depth being much less than one-tenth at 550 nm.

scholarly journals PENGUKURAN KOEFISIEN DIFFUSE ATENUASI (Kd) DI PERAIRAN DANGKAL SEKITAR KARANG LEBAR, KEPULAUAN SERIBU, DKI JAKARTA

2018 ◽  
Vol 8 (2) ◽  
pp. 127-138
Author(s):  
Budhi Agung Prasetyo ◽  
Vincentius Paulus Siregar ◽  
Syamsul Bahri Agus ◽  
Wikanti Asriningrum
Keyword(s):  
Ocean Color ◽  
Downwelling Irradiance

Nilai koefisien diffuse atenuasi Kd(λ) yang berasal dari pengukuran downwelling irradiance Ed(λ) merupakan salah satu parameter penting dalam oceanografi yang memberikan informasi mengenai ketersediaan cahaya dan tingkat penetrasi cahaya di dalam kolom air yang memberikan gambaran mengenai tingkat kecerahan, fotosintesis dan proses biologi lainnya. Informasi mengenai koefisien diffuse atenuasi memegang peranan penting dalam pengembangan algoritma Bio-Optik pada data satelit Ocean Color. Tujuan dari penelitian ini adalah untuk menjelaskan variabilitas dari koefisien diffuse atenuasi di perairan dangkal Karang Lebar, pulau Air dan Panggang dengan menggunakan sensor irradiace hyperspectral radiometer TriOS-RAMSES dengan cakupan rentang panjang gelombang 320 hingga 950 nm dengan resolusi spektral 3.3 nm. Pengukuran in situ dilakukan dengan menurunkan sensor irradiance di setiap kedalaman secara vertikal pada kolom air. Secara keseluruhan hasil pengukuran menunjukkan bahwa nilai Kd(λ) memiliki pola dimana pada region panjang gelombang 380-480 nm akan menurun dan akan meningkat kembali hingga pada region panjang gelombang merah 560-760 nm. Nilai Kd(λ) di bagian dalam gobah ditemukan lebih tinggi dibandingkan di bagian luar gobah dengan perbedaan yang signifikan terjadi di region panjang gelombang merah, perbedaan signifikan nilai Kd(λ) juga terjadi di ketiga wilayah (F = 5.581 > F critical = 5.554) dimana masing-masing area memiliki karakteristik yang berbeda-beda. Secara dominan, nilai Kd(λ) dipengaruhi oleh serapan klorofil-a dengan R2 = 0.808 dibandingkan dengan hamburan dari muatan padatan terlarut dibuktikan dengan R2 = 0.043. Nilai Kd(λ) pada rentang panjang gelombang sinar tampak (400-700 nm) dapat memberikan gambaran mengenai jangkauan penetrasi cahaya sinar tampak yang bisa dideteksi oleh satelit dengan satuan satu kedalaman optik. Hubungan nilai Kd(λ) dengan satu kedalaman optik dijelaskan secara eksponensial dengan persamaan Kd(400-700nm) = 0.375*exp(-0.095*1ζ) dengan koefisien determinasi R2 = 0.97.

scholarly journals In situ autonomous optical radiometry measurements for satellite ocean color validation in the Western Black Sea

2014 ◽  
Vol 11 (6) ◽  
pp. 3003-3034 ◽  
Author(s):  
G. Zibordi ◽  
F. Mélin ◽  
J.-F. Berthon ◽  
M. Talone
Keyword(s):  
Black Sea ◽  
Ocean Color ◽  
Northern Adriatic Sea ◽  
Northern Adriatic ◽  
In Situ Data ◽  
Infrared Imager ◽  
Color Data ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Satellite Ocean Color

Abstract. The accuracy of primary satellite ocean color data products from the Moderate Resolution Imaging Spectroradiometer on-board Aqua (MODIS-A) and the Visible/Infrared Imager/Radiometer Suite (VIIRS), is investigated in the Western Black Sea using in situ measurements from the Gloria site included in the Ocean Color component of the Aerosol Robotic Network (AERONET-OC). The analysis is also extended to an additional well-established AERONET-OC site in the northern Adriatic Sea characterized by optically complex coastal waters exhibiting similarities with those observed at the Gloria site. Results from the comparison of normalized-water leaving radiance LWN indicate biases of a few percent between satellite derived and in situ data at the center-wavelengths relevant for the determination of chlorophyll a concentration (443–547 nm, or equivalent). Remarkable is the consistency among the annual cycle determined with time series of satellite-derived and in situ LWN ratios at these center-wavelengths. Contrarily, the differences between in situ and satellite-derived LWN are pronounced at the blue (i.e., 412 nm) and red (i.e., 667 nm, or equivalent) center-wavelengths, suggesting difficulties in confidently applying satellite-derived radiometric data from these spectral regions for quantitative analysis in optically complex waters.

scholarly journals Validation and Comparison of Water Quality Products in Baltic Lakes Using Sentinel-2 MSI and Sentinel-3 OLCI Data

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 742 ◽  
Author(s):  
Tuuli Soomets ◽  
Kristi Uudeberg ◽  
Dainis Jakovels ◽  
Agris Brauns ◽  
Matiss Zagars ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Water Quality ◽  
Inland Waters ◽  
Water Type ◽  
Water Types ◽  
In Situ Data ◽  
Spatial Coverage ◽  
Level 2 ◽  
Sentinel 2

Inland waters, including lakes, are one of the key points of the carbon cycle. Using remote sensing data in lake monitoring has advantages in both temporal and spatial coverage over traditional in-situ methods that are time consuming and expensive. In this study, we compared two sensors on different Copernicus satellites: Multispectral Instrument (MSI) on Sentinel-2 and Ocean and Land Color Instrument (OLCI) on Sentinel-3 to validate several processors and methods to derive water quality products with best performing atmospheric correction processor applied. For validation we used in-situ data from 49 sampling points across four different lakes, collected during 2018. Level-2 optical water quality products, such as chlorophyll-a and the total suspended matter concentrations, water transparency, and the absorption coefficient of the colored dissolved organic matter were compared against in-situ data. Along with the water quality products, the optical water types were obtained, because in lakes one-method-to-all approach is not working well due to the optical complexity of the inland waters. The dynamics of the optical water types of the two sensors were generally in agreement. In most cases, the band ratio algorithms for both sensors with optical water type guidance gave the best results. The best algorithms to obtain the Level-2 water quality products were different for MSI and OLCI. MSI always outperformed OLCI, with R2 0.84–0.97 for different water quality products. Deriving the water quality parameters with optical water type classification should be the first step in estimating the ecological status of the lakes with remote sensing.

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