scholarly journals Inversion of Phytoplankton Pigment Vertical Profiles from Satellite Data Using Machine Learning

2021 ◽  
Vol 13 (8) ◽  
pp. 1445
Author(s):  
Agathe Puissant ◽  
Roy El Hourany ◽  
Anastase Alexandre Charantonis ◽  
Chris Bowler ◽  
Sylvie Thiria
Keyword(s):  
Machine Learning ◽  
Vertical Distribution ◽  
Missing Values ◽  
Satellite Observations ◽  
Global Ocean ◽  
Self Organizing Map ◽  
Vertical Profiles ◽  
Phytoplankton Pigments ◽  
The Vertical Distribution ◽  
Self Organizing

Observing the vertical dynamic of phytoplankton in the water column is essential to understand the evolution of the ocean primary productivity under climate change and the efficiency of the CO2 biological pump. This is usually made through in-situ measurements. In this paper, we propose a machine learning methodology to infer the vertical distribution of phytoplankton pigments from surface satellite observations, allowing their global estimation with a high spatial and temporal resolution. After imputing missing values through iterative completion Self-Organizing Maps, smoothing and reducing the vertical distributions through principal component analysis, we used a Self-Organizing Map to cluster the reduced profiles with satellite observations. These referent vector clusters were then used to invert the vertical profiles of phytoplankton pigments. The methodology was trained and validated on the MAREDAT dataset and tested on the Tara Oceans dataset. The different regression coefficients R2 between observed and estimated vertical profiles of pigment concentration are, on average, greater than 0.7. We could expect to monitor the vertical distribution of phytoplankton types in the global ocean.

scholarly journals ESTIMATION OF OCEANIC PARTICULATE ORGANIC CARBON WITH MACHINE LEARNING

2020 ◽  
Vol V-2-2020 ◽  
pp. 949-956
Author(s):  
R. Sauzède ◽  
J. E. Johnson ◽  
H. Claustre ◽  
G. Camps-Valls ◽  
A. B. Ruescas
Keyword(s):  
Machine Learning ◽  
Optical Properties ◽  
Organic Carbon ◽  
Vertical Distribution ◽  
Particulate Organic Carbon ◽  
Ocean Color ◽  
Global Scale ◽  
Vertical Profiles ◽  
The Vertical Distribution ◽  
Satellite Ocean Color

Abstract. Understanding and quantifying ocean carbon sinks of the planet is of paramount relevance in the current scenario of global change. Particulate organic carbon (POC) is a key biogeochemical parameter that helps us characterize export processes of the ocean. Ocean color observations enable the estimation of bio-optical proxies of POC (i.e. particulate backscattering coefficient, bbp) in the surface layer of the ocean quasi-synoptically. In parallel, the Argo program distributes vertical profiles of the physical properties with a global coverage and a high spatio-temporal resolution. Merging satellite ocean color and Argo data using a neural networkbased method has already shown strong potential to infer the vertical distribution of bio-optical properties at global scale with high space-time resolution. This method is trained and validated using a database of concurrent vertical profiles of temperature, salinity, and bio-optical properties, i.e. bbp, collected by Biogeochemical-Argo (BGC-Argo) floats, matched up with satellite ocean color products. The present study aims at improving this method by 1) using a larger dataset from BGC-Argo network since 2016 for training, 2) using additional inputs such as altimetry data, which provide significant information on mesoscale processes impacting the vertical distribution of bbp, 3) improving the vertical resolution of estimation, and 4) examining the potential of alternative machine learning-based techniques. As a first attempt with the new data, we used some feature-specific preprocessing routines followed by a Multi-Output Random Forest algorithm on two regions with different ocean dynamics: North Atlantic and Subtropical Gyres. The statistics and the bbp profiles obtained from the validation floats show promising results and suggest this direction is worth investigating even further at global scale.

scholarly journals Seasonal cycle of desert aerosols in western Africa: analysis of the coastal transition with passive and active sensors

2017 ◽  
Vol 17 (13) ◽  
pp. 8395-8410 ◽  
Author(s):  
Habib Senghor ◽  
Éric Machu ◽  
Frédéric Hourdin ◽  
Amadou Thierno Gaye
Keyword(s):  
Vertical Distribution ◽  
Satellite Observations ◽  
Boreal Summer ◽  
Wide Field ◽  
Aerosol Layer ◽  
Good Representation ◽  
Mineral Aerosols ◽  
Western Africa ◽  
The Impact ◽  
The Vertical Distribution

Abstract. The impact of desert aerosols on climate, atmospheric processes, and the environment is still debated in the scientific community. The extent of their influence remains to be determined and particularly requires a better understanding of the variability of their distribution. In this work, we studied the variability of these aerosols in western Africa using different types of satellite observations. SeaWiFS (Sea-Viewing Wide Field-of-View Sensor) and OMI (Ozone Monitoring Instrument) data have been used to characterize the spatial distribution of mineral aerosols from their optical and physical properties over the period 2005–2010. In particular, we focused on the variability of the transition between continental western African and the eastern Atlantic Ocean. Data provided by the lidar scrolling CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) onboard the satellite CALIPSO (Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations) for the period 2007–2013 were then used to assess the seasonal variability of the vertical distribution of desert aerosols. We first obtained a good representation of aerosol optical depth (AOD) and single-scattering albedo (SSA) from the satellites SeaWiFS and OMI, respectively, in comparison with AERONET estimates, both above the continent and the ocean. Dust occurrence frequency is higher in spring and boreal summer. In spring, the highest occurrences are located between the surface and 3 km above sea level, while in summer the highest occurrences are between 2 and 5 km altitude. The vertical distribution given by CALIOP also highlights an abrupt change at the coast from spring to fall with a layer of desert aerosols confined in an atmospheric layer uplifted from the surface of the ocean. This uplift of the aerosol layer above the ocean contrasts with the winter season during which mineral aerosols are confined in the atmospheric boundary layer. Radiosondes at Dakar Weather Station (17.5° W, 14.74° N) provide basic thermodynamic variables which partially give a causal relationship between the layering of the atmospheric circulation over western Africa and their aerosol contents throughout the year. A SSA increase is observed in winter and spring at the transition between the continent and the ocean. The analysis of mean NCEP (National Centers for Environmental Prediction) winds at 925 hPa between 2000 and 2012 suggest a significant contribution of coastal sand sources from Mauritania in winter which would increase SSA over the ocean.

scholarly journals Vertical distribution of sub-micron aerosol chemical composition from North-Western Europe and the North-East Atlantic

2009 ◽  
Vol 9 (2) ◽  
pp. 9117-9150
Author(s):  
W. T. Morgan ◽  
J. D. Allan ◽  
K. N. Bower ◽  
G. Capes ◽  
J. Crosier ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
Vertical Distribution ◽  
Western Europe ◽  
Vertical Profiles ◽  
East Atlantic ◽  
Air Masses ◽  
North East ◽  
The North ◽  
The Vertical Distribution

Abstract. A synthesis of UK based airborne in-situ measurements of aerosol properties representing air masses from North-West Europe and the North-East Atlantic is presented. The major focus of the study is the vertical distribution of sub-micron aerosol chemical composition. Vertical profiles are derived from a Quadrupole Aerosol Mass Spectrometer (Q-AMS). Background sub-micron aerosol vertical profiles are identified and are primarily composed of organic matter and sulphate aerosol. Such background conditions occurred predominantly during periods associated with long-range air mass transport across the Atlantic. These instances may serve as useful model input of aerosol to Western Europe. Increased mass concentration episodes are coincident with European outflow and periods of stagnant/recirculating air masses. Such periods are characterised by significantly enhanced concentrations of nitrate aerosol relative to those of organic matter and sulphate. Periods of enhanced ground level PM2.5 loadings are coincident with instances of high nitrate mass fractions measured on-board the aircraft, indicating that nitrate is a significant contributor to regional pollution episodes. The vertical structure of the sulphate and organic aerosol profiles were shown to be primarily driven by large-scale dynamical processes. The vertical distribution of nitrate is likely determined by both dynamic and thermodynamic processes, with chemical partitioning of gas phase precursors to the particle phase occurring at lower temperatures at the top of the boundary layer. Such effects have profound implications for the aerosol's lifetime and subsequent impacts, highlighting the requirement for accurate representation of the aerosol vertical distribution.

scholarly journals High-resolution vertical distribution and sources of HONO and NO<sub>2</sub> in the nocturnal boundary layer in urban Beijing, China

2020 ◽  
Vol 20 (8) ◽  
pp. 5071-5092 ◽  
Author(s):  
Fanhao Meng ◽  
Min Qin ◽  
Ke Tang ◽  
Jun Duan ◽  
Wu Fang ◽  
...  
Keyword(s):  
High Resolution ◽  
Vertical Distribution ◽  
Inversion Layer ◽  
Ground Surface ◽  
Residual Layer ◽  
Urban Atmosphere ◽  
Vertical Profiles ◽  
Haze Episode ◽  
Beijing China ◽  
The Vertical Distribution

Abstract. Nitrous acid (HONO), an important precursor of the hydroxyl radical (OH), plays a key role in atmospheric chemistry, but its sources are still debated. The production of HONO on aerosol surfaces or on ground surfaces in nocturnal atmospheres remains controversial. The vertical profile provides vertical information on HONO and NO2 to understand the nocturnal HONO production and loss. In this study, we report the first high-resolution (<2.5 m) nocturnal vertical profiles of HONO and NO2 measured from in situ instruments on a movable container that was lifted on the side wiring of a 325 m meteorological tower in Beijing, China. High-resolution vertical profiles revealed the negative gradients of HONO and NO2 in nocturnal boundary layers, and a shallow inversion layer affected the vertical distribution of HONO. The vertical distribution of HONO was consistent with stratification and layering in the nocturnal urban atmosphere below 250 m. The increase in the HONO ∕ NO2 ratio was observed throughout the column from the clean episode to the haze episode, and relatively constant HONO∕NO2 ratios in the residual layer were observed during the haze episode. Direct HONO emissions from traffic contributed 29.3 % ± 12.4 % to the ambient HONO concentrations at night. The ground surface dominates HONO production by heterogeneous uptake of NO2 during clean episodes. In contrast, the HONO production on aerosol surfaces (30–300 ppt) explained the observed HONO increases (15–368 ppt) in the residual layer, suggesting that the aerosol surface dominates HONO production aloft during haze episodes, while the surface production of HONO and direct emissions into the overlying air are minor contributors. Average dry deposition rates of 0.74±0.31 and 1.55±0.32 ppb h−1 were estimated during the clean and haze episodes, respectively, implying that significant quantities of HONO could be deposited to the ground surface at night. Our results highlight the ever-changing contributions of aerosol and ground surfaces in nocturnal HONO production at different pollution levels and encourage more vertical gradient observations to evaluate the contributions from varied HONO sources.

Particle-Size Distribution in Soils of the Khankaiskiy Nature Reserve (Primorye Territory)

2021 ◽  
pp. 99-105
Author(s):  
Olga M. Golodnaya ◽  
Elena A. Zharikova
Keyword(s):  
Particle Size ◽  
Vertical Distribution ◽  
Nature Reserve ◽  
Decisive Role ◽  
Middle Part ◽  
Vertical Profiles ◽  
Physical Clay ◽  
Parent Materials ◽  
The Vertical Distribution ◽  
Alluvial Meadow

Soil texture is determined and the features of particle-size vertical distribution in soils of different landscapes of the Khankaiskiy Nature Reserve are considered. Three variants of the distribution of clay (&lt;0.001 mm) and physical clay (&lt;0.01 mm) fractions along the vertical profiles soils are identified: accumulative, regressive, with a maximum in the middle-profile horizon and with their approximately equal contents in the upper and the lower horizons. A regressive variant is revealed in burozems gleyic, podzoliс-brownzems, dark-humus gley and alluvial meadow gley soils. These soils are characterized by a medium loamy sandy-coarse-dusty composition of the upper horizons and a light- or medium-loamy composition of the middle and lower parts of the profile. The distribution of fine fractions along the profile is observed with a gradual decrease in their content with depth in typical burozems and alluvial meadow gley-ic soils, while the texture of the layer changes from medium loamy to light loamy. The vertical distribution of fine fractions with a maximum in the middle part of the profile is revealed in mucky gley soils. The profile is formed under the influence of a combination of the floodplain process with the introduction and redeposition of suspended particles and gleying. The lithological specificity of the accumulation of the initial parent materials plays a decisive role in the differentiation of fine fractions in the soil profile.

A method for retrieving the spatial distribution of trace gases using measurements of three ground-based MAX-DOAS instruments

2020 ◽  
Author(s):  
Michael Revesz ◽  
Stefan F. Schreier ◽  
Philipp Weihs ◽  
Tim Bösch ◽  
Kezia Lange ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Vertical Distribution ◽  
Trace Gases ◽  
Trace Gas ◽  
Wind Condition ◽  
Vertical Profiles ◽  
Open Issue ◽  
Using Data ◽  
Set Up ◽  
The Vertical Distribution

&lt;p&gt;Within the project VINDOBONA (VIenna horizontal aNd vertical Distribution OBservations Of Nitrogen dioxide and Aerosols), a method was developed to retrieve the spatial distribution of trace gases using data from three ground based MAX-DOAS instruments and was applied on the example of NO&lt;sub&gt;2&lt;/sub&gt;. At three different locations in Vienna (Austria) MAX-DOAS instruments were installed performing measurements in the visible and UV spectral range. Currently, each instrument is set up to determine the column densities in different azimuthal directions and low elevation angles within approximately a horizontal plane. The different lines of sight of the three instruments intersect horizontally and can be used to estimate the horizontal spatial distribution of trace gases. With the knowledge of vertical profiles, even the vertical distribution can be estimated using this method.&amp;#160;&lt;/p&gt;&lt;p&gt;The intersections of the different lines of sight define segments along the slant columns for which the mass concentrations can be estimated. Knowledge about the vertical profiles for a chosen trace gas can be used to correct the retrieved trace gas concentration to specific altitudes above ground. Such corrections are also required since the three instruments were set up at different heights above ground, at different altitudes relative to sea level and with different elevation angles of the lowest viewing direction. One open issue for the retrieval process is the terrain in Vienna in combination with the prevailing wind condition that impacts the horizontal and vertical trace gas distribution and make the retrieval challenging.&amp;#160;&lt;/p&gt;

scholarly journals High-Resolution Monthly Rainfall Database for Ethiopia: Homogenization, Reconstruction, and Gridding

2012 ◽  
Vol 25 (24) ◽  
pp. 8422-8443 ◽  
Author(s):  
G. Mengistu Tsidu
Keyword(s):  
Harmonic Analysis ◽  
Missing Values ◽  
Rainfall Variability ◽  
Singular Spectrum Analysis ◽  
Monthly Rainfall ◽  
Climatic Research Unit ◽  
Southern Ethiopia ◽  
Self Organizing Map ◽  
Global Datasets ◽  
Self Organizing

Abstract Recent heightened concern regarding possible consequences of anthropogenically induced global warming has spurred analyses of data aimed at detection of climate change and more thorough characterization of the natural climate variability. However, there is greater concern regarding the extent and especially quality of the historical climate data. In this paper, rainfall records of 233 gauge stations over Ethiopia for the 1978–2007 period are employed in an analysis that involves homogenization, reconstruction, and gridding onto a regular 0.5° × 0.5° resolution grid. Inhomogeneity is detected and adjusted based on quantile matching. The regularized expectation-maximization and multichannel singular spectrum analysis algorithms are then utilized for imputation of missing values, and the latter has been determined to have a marginal advantage. Ordinary kriging is used to create a gridded monthly rainfall dataset. The spatial and temporal coherence of this dataset are assessed using harmonic analysis, self-organizing maps, and intercomparison with global datasets. The self-organizing map delineates Ethiopia into nine homogeneous rainfall regimes, which is consistent with seasonal and interannual rainfall variations. The harmonic analysis of the dataset reveals that the annual mode accounts for 55%–85% of the seasonal rainfall variability over western Ethiopia while the semiannual mode accounts for up to 40% over southern Ethiopia. The dataset is also intercompared with Global Precipitation Climatology Project (GPCP), Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP), Climatic Research Unit time series version 3 (CRUTS3.0), Tropical Rainfall Measuring Mission (TRMM), and interim ECMWF Re-Analysis (ERA-Interim) rainfall. The correlation of the dataset with global datasets ranges from 0.52 to 0.95 over sparse to dense rain gauge regions. The GPCP rainfall has a small bias and good correlation with the new dataset whereas TRMM and ERA-Interim have relatively large dry and wet biases, respectively.

Vertical profiles of Cs-137 in soil of the Matua Island ( the Central Kuril Islands, Russia) in 2017

2020 ◽  
Author(s):  
Borisov Alexander ◽  
Andrey Ivanov ◽  
Vitaly Linnik
Keyword(s):  
Vertical Distribution ◽  
Specific Activity ◽  
Global Fallout ◽  
Kuril Islands ◽  
Thin Layers ◽  
Maximum Height ◽  
Soil Core ◽  
Vertical Profiles ◽  
Matua Island ◽  
The Vertical Distribution

&lt;p&gt;The 2011 Fukushima-Daiichi nuclear power plant (FDNNP) accident resulted in the atmospheric releases of large quantities of man-made radionuclides. According to [1], Matua Island, located at a distance of more than 1000 km from FDNPP, was also subjected to minor radioactive contamination. Matua Island, 52.6 sq.km, a recent volcano with the highest point of 1446 m a.s.l. is located in the center of the Kuril Islands Arc. Volcanic soils are formed on stratified gravelly-stony tephra more than 60 cm thick, underlain by thin layers of volcanic slags. The latest catastrophic eruption which changed the landscape of the island occurred in 2009.&lt;/p&gt;&lt;p&gt;Studies of the vertical distribution of the Cs-137 in soils were carried out on four landscape catenas. The length of the catenas from the sea shore deep into the island ranged from 700 m (maximum height a.s.l. &amp;#160;70 m) to 3.3 km (height a.s.l. &amp;#160;450 m).&lt;/p&gt;&lt;p&gt;Soil core samples were taken in &amp;#160;summer 2017 at a depth of tephra, which was located at a depth of 10 to 25 cm. Soil was sliced into separate layers with a step of 2 to 5 cm.&lt;/p&gt;&lt;p&gt;The measurement activity concentrations of the Cs-137 in the soil samples were carried out on a low-background gamma spectrometer Canberra Industries. &amp;#160;The counting time&amp;#160; was fixed not less than 24 h to ensure that the statistical measurement error is small.&lt;/p&gt;&lt;p&gt;Cs-134, the &amp;#171;Fukushima&amp;#8221; fallout marker, due to the decay, was not detected. Therefore, it is difficult to accurately assess the Cs-137 contribution from the FDNNP accident from a global fallout.&lt;/p&gt;&lt;p&gt;The vertical distribution of Cs-137 is characterized by extreme heterogeneity, which reflects both the primary fallout conditions and the landscape conditions of the likely lateral redistribution. For &amp;#1089;atena 1 with a length of 1 km and an altitude&amp;#160; of 400 m, the number of pickets (P0, P1, etc. &amp;#8211; the numbering of pickets goes downhill), the specific activity of Cs-137 (Bq/kg) and the depth of the layer (cm) are given as follows: P0-27 Bq/kg (2-4 cm); P1 - 64 Bq/kg (6-8 cm); P2 &amp;#8211; 70 Bq/kg (8-10 cm); P3 - 53 Bq/kg (4-6 cm); P4 - 15 Bq/kg (0-5 cm).&amp;#160; Similar spatial&amp;#160; heterogeneity of the specific activity of Cs-137 and its depth penetration was also found for catena 3 with a length of 1250 m and a height of 75 m (the numbering of pickets goes up the slope): P1-137 Bq/kg (17-20 cm); P2-76 Bq/kg (0-5 cm); P3 - 35 Bq/kg (0-4 cm); P4 - 43 Bq/kg (3-6 cm); P6 &amp;#8211; 24 Bq/kg (5-10 cm).&lt;/p&gt;&lt;p&gt;The distribution of Cs-137 in individual soil layers was used to evaluate the empirically found shapes of the vertical profiles of radionuclide concentration. Cs-137 is believed here to be a&amp;#160; very valuable tracer&amp;#160; that&amp;#160; can be used to test&amp;#160; variability of vertical geochemical migration in Matua&amp;#160; landscapes.&lt;/p&gt;&lt;p&gt;[1]. Ramzaev V.P., Barkovsky A.N., Gromov A.V., Ivanov S.A., Kaduka M.V. Fukushima fallout in Sakhalin Region, Russia, part 1: &lt;sup&gt;137&lt;/sup&gt;Cs and &lt;sup&gt;134&lt;/sup&gt;Cs in grassland soils. Radiation Hygiene, 2018, Vol. 11, No. 1, pp. 25-42.&lt;/p&gt;

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