scholarly journals An algorithm for detecting <i>Trichodesmium</i> surface blooms in the South Western Tropical Pacific

2011 ◽  
Vol 8 (12) ◽  
pp. 3631-3647 ◽  
Author(s):  
C. Dupouy ◽  
D. Benielli-Gary ◽  
J. Neveux ◽  
Y. Dandonneau ◽  
T. K. Westberry
Keyword(s):  
Co2 Sequestration ◽  
New Caledonia ◽  
Tropical Pacific ◽  
The South ◽  
Western Tropical Pacific ◽  
Tropical Oceans ◽  
Fiji Islands ◽  
C And N ◽  
In Situ Observations

Abstract. Trichodesmium, a major colonial cyanobacterial nitrogen fixer, forms large blooms in NO3-depleted tropical oceans and enhances CO2 sequestration by the ocean due to its ability to fix dissolved dinitrogen. Thus, its importance in C and N cycles requires better estimates of its distribution at basin to global scales. However, existing algorithms to detect them from satellite have not yet been successful in the South Western Tropical Pacific (SP). Here, a novel algorithm (TRICHOdesmium SATellite) based on radiance anomaly spectra (RAS) observed in SeaWiFS imagery, is used to detect Trichodesmium during the austral summertime in the SP (5° S–25° S 160° E–170° W). Selected pixels are characterized by a restricted range of parameters quantifying RAS spectra (e.g. slope, intercept, curvature). The fraction of valid (non-cloudy) pixels identified as Trichodesmium surface blooms in the region is low (between 0.01 and 0.2 %), but is about 100 times higher than deduced from previous algorithms. At daily scales in the SP, this fraction represents a total ocean surface area varying from 16 to 48 km2 in Winter and from 200 to 1000 km2 in Summer (and at monthly scale, from 500 to 1000 km2 in Winter and from 3100 to 10 890 km2 in Summer with a maximum of 26 432 km2 in January 1999). The daily distribution of Trichodesmium surface accumulations in the SP detected by TRICHOSAT is presented for the period 1998–2010 which demonstrates that the number of selected pixels peaks in November–February each year, consistent with field observations. This approach was validated with in situ observations of Trichodesmium surface accumulations in the Melanesian archipelago around New Caledonia, Vanuatu and Fiji Islands for the same period.

scholarly journals An algorithm for detecting <i>Trichodesmium</i> surface blooms in the South Western Tropical Pacific

2011 ◽  
Vol 8 (3) ◽  
pp. 5653-5689 ◽  
Author(s):  
C. Dupouy ◽  
D. Benielli-Gary ◽  
J. Neveux ◽  
Y. Dandonneau ◽  
T. K. Westberry
Keyword(s):  
Total Surface Area ◽  
Tropical Pacific ◽  
The South ◽  
Western Tropical Pacific ◽  
Tropical Oceans ◽  
Novel Approach ◽  
Monthly Distribution ◽  
C And N ◽  
In Situ Observations

Abstract. Trichodesmium, a major colonial cyanobacterial nitrogen fixer, forms large blooms in NO3-depleted tropical oceans and enhances CO2 sequestration by the ocean due to its ability to fix dissolved dinitrogen. Thus, its importance in C and N cycles requires better estimates of its distribution at basin to global scales. However, existing algorithms to detect them from satellite have not yet been successful in the South Western Tropical Pacific (SWTP). Here, a novel approach based on radiance anomaly spectra (RAS) observed in SeaWiFS imagery is used to detect Trichodesmium during the austral summertime in the SWTP. Selected pixels are characterized by a restricted range of parameters quantifying RAS spectra quantitative parameters (e.g. slope, intercept, curvature). The fraction of valid pixels identified as Trichodesmium surface blooms in the region 5° S–25° S 160° E–190° E is low (between 0.01 and 0.2 %), but is about 100 times higher than suggested by previous algorithms. This represents a total surface area which varies from 1500 to 20 000 km2. A monthly distribution of Trichodesmium surface accumulations in the SWTP is presented which demonstrates that the number of selected pixels peaks in November–February each year, consistent with field observations. This approach was validated with in situ observations of Trichodesmium surface accumulations for the period 1998–2010.

scholarly journals Remote Sensing of <i>Trichodesmium</i> spp. mats in the Western Tropical South Pacific

2018 ◽  
Author(s):  
Guillaume Rousset ◽  
Florian De Boissieu ◽  
Christophe E. Menkes ◽  
Jérôme Lefèvre ◽  
Robert Frouin ◽  
...  
Keyword(s):  
Large Scale ◽  
New Caledonia ◽  
Regional Scale ◽  
Atmospheric Correction ◽  
South Pacific ◽  
The South ◽  
False Positive Detection ◽  
Modis Imagery ◽  
In Situ Observations

Abstract. Trichodesmium is the main nitrogen-fixing species in the South Pacific region, a hotspot for diazotrophy. Due to the paucity of in situ observations, methods for detecting Trichodesmium presence on a large scale have been investigated to assess the regional-to-global impact of these species on primary production and carbon cycling. A number of satellite-derived algorithms have been developed to identify Trichodesmium surface blooms, but determining with confidence their accuracy has been difficult, chiefly because of the scarcity of sea-truth information at time of satellite overpass. Here, we use a series of new cruises as well as airborne observational surveys in the South Pacific to quantify statistically the ability of these algorithms to discern correctly Trichodesmium surface blooms in the satellite imagery. The evaluation, performed on MODIS data at 250 m and 1 km resolution acquired over the South West Pacific, shows limitations due to spatial resolution, clouds, and atmospheric correction. A new satellite-based algorithm is designed to alleviate some of these limitations, by exploiting optimally spectral features in the atmospherically corrected reflectance at 531, 645, 678, 748, and 869 nm. This algorithm outperforms former ones near clouds, limiting false positive detection, and allowing regional scale automation. Compared with observations, 80 % of the detected mats are within a 2 km range, demonstrating the good statistical skill of the new algorithm. Application to MODIS imagery acquired during the February–March 2015 OUTPACE campaign reveals the presence of surface blooms Northwest and East of New Caledonia and near 20° S–172° W in qualitative agreement with measured nitrogen fixation rates. The new algorithm, however, fails to detect sub-surface booms evidenced in trichome counts. Improving Trichodesmium detection requires measuring ocean color at higher spectral and spatial (

scholarly journals Diazotrophic <i>Trichodesmium</i> influence on ocean color and pigment composition in the South West tropical Pacific

2018 ◽  
Author(s):  
Cécile Dupouy ◽  
Robert Frouin ◽  
Marc Tedetti ◽  
Morgane Maillard ◽  
Martine Rodier ◽  
...  
Keyword(s):  
High Performance ◽  
New Caledonia ◽  
Principal Component ◽  
Euphotic Zone ◽  
Tropical Pacific ◽  
The South ◽  
South West ◽  
Underwater Vision ◽  
Fiji Islands ◽  
High Fluorescence

Abstract. We assessed the influence of the marine diazotrophic cyanobacterium Trichodesmium on the bio-optical properties of South West tropical Pacific waters (18–22° S, 160° E–160° W) during the February–March 2015 OUTPACE cruise. We performed measurements of backscattering and absorption coefficients, irradiance, and radiance, in the euphotic zone, and took Underwater Vision Profiler 5 (UPV5) pictures for counting the largest Trichodesmium spp. colonies. Pigment concentrations were determined by fluorimetry and by high performance liquid chromatography and picoplankton abundance by flow cytometry. Trichome concentration was estimated from pigment algorithms and validated by surface visual counts. In result, the large colonies were well correlated to the trichome concentration estimates (though with a large factor of 600 to 900, due to aggregation processes). Large Trichodesmium abundance was always associated with particulate absorption at a peak of mycosporine-like amino acid absorption, and high particulate backscattering, but not with high fluorescence, high chlorophyll-a concentration, or blue particulate absorption in the water column. Along the West to East transect, Trichodesmium together with Prochlorococcus represented the major part of total chlorophyll and the other groups were negligible. Trichodesmium contribution to chlorophyll was the highest in the Melanesian Archipelago around New Caledonia and Vanuatu, progressively decreased to the vicinity of the Fiji Islands, and reached a minimum in the South Pacific gyre where the contribution of Prochlorococcus was maximum. At the frontal LDB, Trichodesmium and Prochlorococcus has almost same contributions. The relationship between normalized water-leaving radiance, in the ultraviolet and visible domains, nLw, and chlorophyll was generally similar to that found in the Eastern tropical at BIOSOPE. Principal component analysis (PCA) of OUTPACE data showed that nLw were strongly correlated to chlorophyll except in the green and yellow domains. These results, as well as differences in the PCA of BIOSOPE data, suggested that nLw variability in the green and yellow during OUTPACE was influenced by other variables, associated with Trichodesmium presence as the backscattering coefficient, phycoerythrin fluorescence, and/or zeaxanthin absorption. Trichodesmium detection should then involve examination of nLw at the green and yellow wavelengths.

scholarly journals The Energy Budget of the Polar Atmosphere in MERRA

2012 ◽  
Vol 25 (1) ◽  
pp. 5-24 ◽  
Author(s):  
Richard I. Cullather ◽  
Michael G. Bosilovich
Keyword(s):  
Energy Budget ◽  
The Arctic ◽  
Polar Regions ◽  
Polar Cap ◽  
The South ◽  
Atmospheric Energy ◽  
In Situ Observations ◽  
Energy Convergence ◽  
South Polar

Abstract Components of the atmospheric energy budget from the Modern-Era Retrospective Analysis for Research and Applications (MERRA) are evaluated in polar regions for the period 1979–2005 and compared with previous estimates, in situ observations, and contemporary reanalyses. Closure of the budget is reflected by the analysis increments term, which indicates an energy surplus of 11 W m−2 over the North Polar cap (70°–90°N) and 22 W m−2 over the South Polar cap (70°–90°S). Total atmospheric energy convergence from MERRA compares favorably with previous studies for northern high latitudes but exceeds the available previous estimate for the South Polar cap by 46%. Discrepancies with the Southern Hemisphere energy transport are largest in autumn and may be related to differences in topography with earlier reanalyses. For the Arctic, differences between MERRA and other sources in top of atmosphere (TOA) and surface radiative fluxes are largest in May. These differences are concurrent with the largest discrepancies between MERRA parameterized and observed surface albedo. For May, in situ observations of the upwelling shortwave flux in the Arctic are 80 W m−2 larger than MERRA, while the MERRA downwelling longwave flux is underestimated by 12 W m−2 throughout the year. Over grounded ice sheets, the annual mean net surface energy flux in MERRA is erroneously nonzero. Contemporary reanalyses from the Climate Forecast Center (CFSR) and the Interim Re-Analyses of the European Centre for Medium-Range Weather Forecasts (ERA-I) are found to have better surface parameterizations; however, these reanalyses also disagree with observed surface and TOA energy fluxes. Discrepancies among available reanalyses underscore the challenge of reproducing credible estimates of the atmospheric energy budget in polar regions.

The East Pacific/South Pacific Boundary: New taxa and occurrences from Rapa Nui (Easter Island), New Caledonia and adjacent regions

Zootaxa ◽  
2021 ◽  
Vol 4980 (3) ◽  
pp. 401-450
Author(s):  
CHRISTOPHER L. MAH
Keyword(s):  
New Species ◽  
New Genus ◽  
New Caledonia ◽  
Easter Island ◽  
Rapa Nui ◽  
East Pacific ◽  
In Situ Observations ◽  
Three New Species ◽  
New Occurrences

Recent expeditions to Rapa Nui (also known as Easter Island) and New Caledonia have revealed undescribed species from mesophotic and deeper depths. This includes three new species from Rapa Nui, Hacelia raaraa, Linckia profunda (Ophidiasteridae), Uokeaster ahi (Asterodiscididae) and two new species from New Caledonia, Astroglypha pyramidata n. gen. and Ophidiaster colossus (Ophidiasteridae). The new genus Astroglypha is described for A. pyramidata but the genus also includes the Atlantic Tamaria passiflora, which is reassigned herein. Pauliastra n. gen. is designated as a replacement for the homonym issue with Pauliella. New occurrences and synonymies are addressed for taxa related to New Caledonia, Rapa Nui and adjacent regions. A morphology based phylogenetic analysis agrees with prior work which placed Goniaster among the Asterodiscididae and posits biogeographic relationships among asterodiscidid genera. Implications for the Goniasteridae and placement of Goniaster among asterodiscidid genera are discussed. Biogeography and relationships among taxa from Rapa Nui and New Caledonia are reviewed. In situ observations from species observed from Rapa Nui are included. 

South Pacific Commission

1952 ◽  
Vol 6 (1) ◽  
pp. 152-153
Keyword(s):  
New Zealand ◽  
Pacific Islands ◽  
New Caledonia ◽  
South Pacific ◽  
Development Project ◽  
Training Institution ◽  
The South ◽  
Control Programs ◽  
Fiji Islands ◽  
Deputy Chairman

The eighth session of the South Pacific Commission, held at Nouméa, New Caledonia, from October 29 to November 9, 1951, was presided over by R. L. Lassalle-Séré (France). On November 7, 1951, the six participating countries (Australia, France, Netherlands, New Zealand, United Kingdom, and United States) signed an agreement extending the scope of the Commission to include Guam and the Trust Territory of the Pacific Islands. Other agenda items included consideration of the Commission's work program and budget for 1952. The program, consisting of 39 projects, included ten in the field of health. The Commission discussed the report of the conference of medical experts on filariasis and elephantiasis which was held in Tahiti from August 21 to September 1, 1951, to study current research and control programs for these diseases and to recommend measures for combatting them,2 and decided to appoint an expert to supervise the implementation of these recommendations. The Commission also reviewed the work done in the projects on tuberculosis, nutrition and leprosy. In the economic category, in which there were ten projects, the commission considered plans for a conference of fisheries experts in 1952 and grantsin-aid for the furtherance of work with economic plants. In the field of social development, where nineteen projects were considered, the Commission discussed the preparation of plans for a model vocational training institution; publication of a report on research in social anthropology and a report on a community development project being carried out in the Fiji Islands; continuation of a housing survey; and the work of the South Pacific Literature Bureau. It was decided to appoint E. M. Ojala (New Zealand) deputy chairman of the South Pacific Research Council.

On the role of tropical waves triggering extreme rainfall and flood in Sulawesi, Indonesia: a multi-scale interaction perspective

2020 ◽  
Author(s):  
Beata Latos ◽  
Thierry Lefort ◽  
Maria Flatau ◽  
Donaldi Permana ◽  
Piotr Flatau ◽  
...  
Keyword(s):  
Extreme Rainfall ◽  
Active Phase ◽  
Radar Data ◽  
Kelvin Wave ◽  
The South ◽  
Sea Surface Temperature Anomalies ◽  
Extreme Rain ◽  
In Situ Observations ◽  
Rain Events

&lt;p&gt;On January 22, 2019 extreme rainfall in the South-Western Sulawesi, Indonesia, triggered a massive, deadly flood, the most devastating one ever reported. This happened during an interaction of a robust Convectively Coupled Kelvin Wave (CCKW) and Equatorial Rossby Wave (ER). Potential causes of a flood include Madden Julian-Oscillation active phase, rainy season with monsoonal flow in the Karimata Strait, positive sea surface temperature anomalies supportive of convection, and synoptic-scale weather systems. All these factors can contribute to extreme rainfall and a flood development. Nonetheless, here we show that in this particular case enhancement of low-level westerlies led to convergence and forced ascend of moist air over orographic features of the south-western Sulawesi. This chain of processes was a result of a propagation of a CCKW, with contribution from an ER. Satellite and radar data analysis, as well as in-situ observations reveal that convergence and strong westerlies in the Java Sea, forced by the CCKW, resulted in the rain events in Jeneberang River Basin and the devastating flood in the city of Makassar.&lt;/p&gt;&lt;p&gt;Additional analysis of 20 years of the flood database together with in situ observations and satellite data support our hypothesis, based on this case study, of a significance of an enhanced westerlies as a precursor of extreme rain events and floods in Makassar, the capital and most populous city in Sulawesi.&lt;/p&gt;

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