scholarly journals An Improved Adaptive Subsurface Phytoplankton Layer Detection Method for Ocean Lidar Data

2021 ◽  
Vol 13 (19) ◽  
pp. 3875
Author(s):  
Chunyi Zhong ◽  
Peng Chen ◽  
Delu Pan
Keyword(s):  
Remote Sensing ◽  
Detection Method ◽  
Estimation Method ◽  
Absolute Difference ◽  
Lidar Data ◽  
Improved Method ◽  
Passive Remote Sensing ◽  
Layer Extraction ◽  
The Vertical Distribution

Phytoplankton, as the foundation of primary production, is of great significant for the marine ecosystem. The vertical distribution of phytoplankton contains key information about marine ecology and the optical properties of water bodies related to remote sensing.The common methods to detect subsurface phytoplankton biomass are often in situ measurements and passive remote sensing; however, the bio-argo measurement is discrete and costly, and the passive remote sensing measurement is limited to obtain the vertical information. As a component of active remote sensing, lidar technology has been proved as an effective method for mapping the vertical distribution of phytoplankton. In the past years, there have been few studies on the phytoplankton layer extraction method for lidar data. The existing subsurface layer extraction algorithms are often non-automatic, which need manual intervention or empirical parameters to set the layer extraction threshold. Hence, an improved adaptive subsurface phytoplankton layer detection method was proposed, which incorporates a curve fitting method and a robust estimation method to determine the depth and thickness of subsurface phytoplankton scattering layer. The combination of robust estimation method can realize automatic calculation of layer detection threshold according to the characteristic of each lidar signal, instead of an empirical fixed value used in previous works. In addition, the noise jamming signal can also be effectively detected and removed. Lidar data and in situ spatio-temporal matching Chlorophyll-a profile data obtained in Sanya Bay in 2018 was used for algorithm verification. The example result of step-by-step process illustrates that the improved method is available for adaptive threshold determination for layer detection and redundant noise signals elimination. Correlation analysis and statistical hypothesis testing shows the retrieved subsurface phytoplankton maximum depth by the improved method and in situ measurement is highly relevant. The absolute difference of layer maximum depth between lidar data and in situ data for all stations is less than 0.75 m, and mean absolute difference of layer thickness difference is about 1.74 m. At last, the improved method was also applied to the lidar data obtained near Wuzhizhou Island seawater, which proves that the method is feasiable and robust for various sea areas.

scholarly journals Aerosol optical and microphysical retrievals from a hybrid multiwavelength lidar data set – DISCOVER-AQ 2011

2014 ◽  
Vol 7 (9) ◽  
pp. 3095-3112 ◽  
Author(s):  
P. Sawamura ◽  
D. Müller ◽  
R. M. Hoff ◽  
C. A. Hostetler ◽  
R. A. Ferrare ◽  
...  
Keyword(s):  
Remote Sensing ◽  
In Situ Measurements ◽  
Index Of Refraction ◽  
High Spectral Resolution ◽  
Lidar Data ◽  
Data Set ◽  
Microphysical Properties ◽  
Lidar Measurements ◽  
Multiwavelength Lidar

Abstract. Retrievals of aerosol microphysical properties (effective radius, volume and surface-area concentrations) and aerosol optical properties (complex index of refraction and single-scattering albedo) were obtained from a hybrid multiwavelength lidar data set for the first time. In July 2011, in the Baltimore–Washington DC region, synergistic profiling of optical and microphysical properties of aerosols with both airborne (in situ and remote sensing) and ground-based remote sensing systems was performed during the first deployment of DISCOVER-AQ. The hybrid multiwavelength lidar data set combines ground-based elastic backscatter lidar measurements at 355 nm with airborne High-Spectral-Resolution Lidar (HSRL) measurements at 532 nm and elastic backscatter lidar measurements at 1064 nm that were obtained less than 5 km apart from each other. This was the first study in which optical and microphysical retrievals from lidar were obtained during the day and directly compared to AERONET and in situ measurements for 11 cases. Good agreement was observed between lidar and AERONET retrievals. Larger discrepancies were observed between lidar retrievals and in situ measurements obtained by the aircraft and aerosol hygroscopic effects are believed to be the main factor in such discrepancies.

scholarly journals Measurements of Aerosols and Trace Gases in Southern Romania

2017 ◽  
Vol 68 (4) ◽  
pp. 873-878
Author(s):  
Alexandru Dandocsi ◽  
Anca Nemuc ◽  
Cristina Marin ◽  
Simona Andrei
Keyword(s):  
Remote Sensing ◽  
Vertical Profiles ◽  
Aerosol Mass Spectrometer ◽  
Boundary Layer Height ◽  
Passive Remote Sensing ◽  
Aerosol Mass ◽  
Scanning Lidar ◽  
532 Nm

An intensive measurement campaign was performed during September 2014 in southern Romania in two different locations: Magurele, Ilfov County and Turceni, Gorj County. This paper presents one case study with analysis of the aerosol properties from in-situ, passive remote sensing and active remote sensing measurements. A Multiwavelength Raman Lidar (RALI) provided one hour averaged vertical profiles of extinction and backscatter from the 532 nm and 1064 nm channels in Magurele. The UV scanning Lidar (MILI) provided one hour averaged backscattered and extinction vertical profiles for Turceni. Planetary Boundary Layer Height (PBLH) was calculated using the altitude of the maximum negative gradient of the range corrected signal. Mass concentrations for different aerosol species (organics, nitrate, sulphate, ammonium and chloride) were obtained from in-situ measurements using Aerosol Mass Spectrometer located in M�gurele and Aerosol Chemical Speciation Monitor (ACSM) located in Turceni.

scholarly journals Exploring Atmospheric Aerosols by Twilight Photometry

2008 ◽  
Vol 25 (9) ◽  
pp. 1600-1607 ◽  
Author(s):  
B. Padma Kumari ◽  
S. H. Kulkarni ◽  
D. B. Jadhav ◽  
A. L. Londhe ◽  
H. K. Trimbake
Keyword(s):  
Remote Sensing ◽  
Atmospheric Aerosols ◽  
Integrated Circuit ◽  
Tropical Meteorology ◽  
Indian Institute ◽  
Experimental Setup ◽  
Vertical Profiles ◽  
Remote Sensing Technique ◽  
Passive Remote Sensing ◽  
The Vertical Distribution

Abstract The instrument twilight photometer was designed, developed, and installed at the Indian Institute of Tropical Meteorology (IITM), Pune, India (18°43′N, 73°51′E), to monitor the vertical distribution of atmospheric aerosols. The instrument, based on passive remote sensing technique, is simple and inexpensive. It is operated only during twilights, and the method of retrieval of aerosol profile is based on a simple twilight technique. It functions at a single wavelength (660 nm), and a photomultiplier tube is used as a detector. The amplifier, an important component of the system, was designed and developed by connecting 10 single integrated-circuit (IC) amplifiers in parallel so that the noise at the output is drastically reduced and the sensitivity of the system has been increased. As a result, the vertical profiles are retrieved to a maximum of 120 km. A brief description of the basic principle of twilight technique, the experimental setup, and the method of retrieval of aerosol profiles using the above photometer are detailed in this paper.

scholarly journals Remote Sensing

2017 ◽  
Vol 58 ◽  
pp. 10.1-10.21 ◽  
Author(s):  
J. Bühl ◽  
S. Alexander ◽  
S. Crewell ◽  
A. Heymsfield ◽  
H. Kalesse ◽  
...  
Keyword(s):  
Remote Sensing ◽  
In Situ Measurements ◽  
Ice Formation ◽  
Literature Study ◽  
Passive Remote Sensing ◽  
Level Information ◽  
Formation And Evolution ◽  
Remote Sensing Techniques ◽  
Remote Sensing Methods

Abstract State-of-the-art remote sensing techniques applicable to the investigation of ice formation and evolution are described. Ground-based and spaceborne measurements with lidar, radar, and radiometric techniques are discussed together with a global view on past and ongoing remote sensing measurement campaigns concerned with the study of ice formation and evolution. This chapter has the intention of a literature study and should illustrate the major efforts that are currently taken in the field of remote sensing of atmospheric ice. Since other chapters of this monograph mainly focus on aircraft in situ measurements, special emphasis is put on active remote sensing instruments and synergies between aircraft in situ measurements and passive remote sensing methods. The chapter concentrates on homogeneous and heterogeneous ice formation in the troposphere because this is a major topic of this monograph. Furthermore, methods that deliver direct, process-level information about ice formation are elaborated with a special emphasis on active remote sensing methods. Passive remote sensing methods are also dealt with but only in the context of synergy with aircraft in situ measurements.

scholarly journals Global carbon monoxide vertical distributions from spaceborne high-resolution FTIR nadir measurements

2005 ◽  
Vol 5 (11) ◽  
pp. 2901-2914 ◽  
Author(s):  
B. Barret ◽  
S. Turquety ◽  
D. Hurtmans ◽  
C. Clerbaux ◽  
J. Hadji-Lazaro ◽  
...  
Keyword(s):  
High Resolution ◽  
Estimation Method ◽  
Lower Troposphere ◽  
Optimal Estimation ◽  
Vertical Distributions ◽  
Surface Measurements ◽  
The Vertical Distribution ◽  
Global Carbon ◽  
Good Agreement

Abstract. This paper presents the first global distributions of CO vertical profiles retrieved from a thermal infrared FTS working in the nadir geometry. It is based on the exploitation of the high resolution and high quality spectra measured by the Interferometric Monitor of Greenhouse gases (IMG) which flew onboard the Japanese ADEOS platform in 1996-1997. The retrievals are performed with an algorithm based on the Optimal Estimation Method (OEM) and are characterized in terms of vertical sensitivity and error budget. It is found that most of the IMG measurements contain between 1.5 and 2.2 independent pieces of information about the vertical distribution of CO from the lower troposphere to the upper troposphere-lower stratosphere (UTLS). The retrievals are validated against coincident NOAA/CMDL in situ surface measurements and NDSC/FTIR total columns measurements. The retrieved global distributions of CO are also found to be in good agreement with the distributions modeled by the GEOS-CHEM 3D CTM, highlighting the ability of IMG to capture the horizontal as well as the vertical structure of the CO distributions.

scholarly journals Remote sensing of sea ice: advances during the DAMOCLES project

2012 ◽  
Vol 6 (6) ◽  
pp. 1411-1434 ◽  
Author(s):  
G. Heygster ◽  
V. Alexandrov ◽  
G. Dybkjær ◽  
W. von Hoyningen-Huene ◽  
F. Girard-Ardhuin ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Sea Ice ◽  
Estimation Method ◽  
Satellite Observations ◽  
Microwave Emission ◽  
The Arctic ◽  
Ice Thickness ◽  
In Situ Observation ◽  
Microwave Emissivity

Abstract. In the Arctic, global warming is particularly pronounced so that we need to monitor its development continuously. On the other hand, the vast and hostile conditions make in situ observation difficult, so that available satellite observations should be exploited in the best possible way to extract geophysical information. Here, we give a résumé of the sea ice remote sensing efforts of the European Union's (EU) project DAMOCLES (Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies). In order to better understand the seasonal variation of the microwave emission of sea ice observed from space, the monthly variations of the microwave emissivity of first-year and multi-year sea ice have been derived for the frequencies of the microwave imagers like AMSR-E (Advanced Microwave Scanning Radiometer on EOS) and sounding frequencies of AMSU (Advanced Microwave Sounding Unit), and have been used to develop an optimal estimation method to retrieve sea ice and atmospheric parameters simultaneously. In addition, a sea ice microwave emissivity model has been used together with a thermodynamic model to establish relations between the emissivities from 6 GHz to 50 GHz. At the latter frequency, the emissivity is needed for assimilation into atmospheric circulation models, but is more difficult to observe directly. The size of the snow grains on top of the sea ice influences both its albedo and the microwave emission. A method to determine the effective size of the snow grains from observations in the visible range (MODIS) is developed and demonstrated in an application on the Ross ice shelf. The bidirectional reflectivity distribution function (BRDF) of snow, which is an essential input parameter to the retrieval, has been measured in situ on Svalbard during the DAMOCLES campaign, and a BRDF model assuming aspherical particles is developed. Sea ice drift and deformation is derived from satellite observations with the scatterometer ASCAT (62.5 km grid spacing), with visible AVHRR observations (20 km), with the synthetic aperture radar sensor ASAR (10 km), and a multi-sensor product (62.5 km) with improved angular resolution (Continuous Maximum Cross Correlation, CMCC method) is presented. CMCC is also used to derive the sea ice deformation, important for formation of sea ice leads (diverging deformation) and pressure ridges (converging). The indirect determination of sea ice thickness from altimeter freeboard data requires knowledge of the ice density and snow load on sea ice. The relation between freeboard and ice thickness is investigated based on the airborne Sever expeditions conducted between 1928 and 1993.

Research on the SVM Classification of Active and Passive Remote Sensing Data Based on the Feature Per-Parcel

2013 ◽  
Vol 405-408 ◽  
pp. 3001-3006 ◽  
Author(s):  
Shuang Ting Wang ◽  
Chun Lai Wang ◽  
Wei Bing Du ◽  
Le Le Tong ◽  
Fei Wang
Keyword(s):  
Remote Sensing ◽  
Texture Feature ◽  
Remote Sensing Data ◽  
Remote Sensing Image ◽  
Lidar Data ◽  
Pixel Classification ◽  
Classification Result ◽  
Passive Remote Sensing ◽  
High Resolution Image

Pepper and Salt" phenomenon and misclassification phenomenon are serious and the accuracy is low based on pixel classification, when only use a single remote sensing image. In this article, joint LiDAR data and high resolution image together based on feature per-parcel classification,and in the image segmentation stage, texture feature is introduced, these can full use of spectral informationtexture feature and elevation information in classification, to solve same object with different spectra and same spectrum with different objects. Compared with the classification based on pixel, only use a single remote sensing image, the method based on feature per-parcel with spectrumtexture and elevation information achieved a high accuracy,96.94%, improved the classification result.

scholarly journals STRAT: An Automated Algorithm to Retrieve the Vertical Structure of the Atmosphere from Single-Channel Lidar Data

2007 ◽  
Vol 24 (5) ◽  
pp. 761-775 ◽  
Author(s):  
Y. Morille ◽  
M. Haeffelin ◽  
P. Drobinski ◽  
J. Pelon
Keyword(s):  
Vertical Structure ◽  
Detection Method ◽  
Single Channel ◽  
Temporal Variations ◽  
Large Datasets ◽  
Lidar Data ◽  
Lidar Signal ◽  
Automated Algorithm ◽  
The World ◽  
The Vertical Distribution

Abstract Today several lidar networks around the world provide large datasets that are extremely valuable for aerosol and cloud research. Retrieval of atmospheric constituent properties from lidar profiles requires detailed analysis of spatial and temporal variations of the signal. This paper presents an algorithm called Structure of the Atmosphere (STRAT), which is designed to retrieve the vertical distribution of cloud and aerosol layers in the boundary layer and through the free troposphere and to identify near-particle-free regions of the vertical profile and the range at which the lidar signal becomes too attenuated for exploitation, from a single lidar channel. The paper describes each detection method used in the STRAT algorithm and its application to a tropospheric backscatter lidar operated at the SIRTA observatory, in Palaiseau, 20 km south of Paris, France. STRAT retrievals are compared to other means of layer detection and classification; retrieval performances and uncertainties are discussed.

scholarly journals Study of aerosol microphysical properties profiles retrieved from ground-based remote sensing and aircraft in-situ measurements during a Saharan dust event

2015 ◽  
Vol 8 (9) ◽  
pp. 9289-9338 ◽  
Author(s):  
M. J. Granados-Muñoz ◽  
J. A. Bravo-Aranda ◽  
D. Baumgardner ◽  
J. L. Guerrero-Rascado ◽  
D. Pérez-Ramírez ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Volume Concentration ◽  
Mineral Dust ◽  
In Situ Measurements ◽  
Saharan Dust ◽  
Night Time ◽  
Passive Remote Sensing ◽  
Microphysical Properties ◽  
Multi Wavelength

Abstract. In this work we present an analysis of mineral dust optical and microphysical properties obtained from different retrieval techniques applied to active and passive remote sensing measurements, including a comparison with simultaneous in-situ aircraft measurements. Data were collected in a field campaign performed during a mineral dust outbreak a Granada, Spain, experimental site (37.16° N, 3.61° W, 680 m a.s.l.) on the 27 June 2011. Column-integrated properties are provided by sun- and star-photometry which allows a continuous evaluation of the mineral dust optical properties during both day and night-time. Both the Linear Estimation and AERONET (Aerosol Robotic Network) inversion algorithms are applied for the retrieval of the column-integrated microphysical particle properties. In addition, vertically-resolved microphysical properties are obtained from a multi-wavelength Raman lidar system included in EARLINET (European Aerosol Research Lidar Network), by using both LIRIC (Lidar Radiometer Inversion Code) algorithm during daytime and an algorithm applied to the Raman measurements based on the regularization technique during night-time. LIRIC retrievals reveal several dust layers between 3 and 5 km a.s.l. with volume concentrations of the coarse spheroid mode up to 60 μm3 cm−3. The combined use of the regularization and LIRIC methods reveals the night-to-day evolution of the vertical structure of the mineral dust microphysical properties and offers complementary information to that from column-integrated variables retrieved from passive remote sensing. Additionally, lidar depolarization profiles and LIRIC retrieved volume concentration are compared with aircraft in-situ measurements. This study presents for the first time a comparison of both volume concentration and dust particle polarization ratios measured with in-situ and remote sensing techniques. Results for the depolarization measurements in the dust layer indicate reasonable agreement within the estimated uncertainties. The differences in the volume concentration profiles, although somewhat larger, are still within the expected uncertainties.

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