scholarly journals Interannual variability of isotopic composition in water vapor over western Africa and its relationship to ENSO

2015 ◽  
Vol 15 (6) ◽  
pp. 3193-3204 ◽  
Author(s):  
A. Okazaki ◽  
Y. Satoh ◽  
G. Tremoy ◽  
F. Vimeux ◽  
R. Scheepmaker ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Southern Oscillation ◽  
Monsoon Season ◽  
Precipitation Amount ◽  
Isotopic Signature ◽  
Atmospheric Environment ◽  
Global Spectral Model ◽  
Near Surface ◽  
Western Africa ◽  
The Relationship

Abstract. This study was performed to examine the relationship between isotopic composition in near-surface vapor (δ18Ov) over western Africa during the monsoon season and El Niño–Southern Oscillation (ENSO) activity using the Isotope-incorporated Global Spectral Model. The model was evaluated using a satellite and in situ observations at daily to interannual timescales. The model provided an accurate simulation of the spatial pattern and seasonal and interannual variations of isotopic composition in column and surface vapor and precipitation over western Africa. Encouraged by this result, we conducted a simulation stretching 34 years (1979–2012) to investigate the relationship between atmospheric environment and isotopic signature on an interannual timescale. The simulation indicated that the depletion in the monsoon season does not appear every year at Niamey. The major difference between the composite fields with and without depletion was in the amount of precipitation in the upstream area of Niamey. As the interannual variation of the precipitation amount is influenced by the ENSO, we regressed the monsoon season averaged δ18Ov from the model and annually averaged NINO3 index and found a statistically significant correlation (R = 0.56, P < 0.01) at Niamey. This relationship suggests that there is a possibility of reconstructing past western African monsoon activity and ENSO using climate proxies.

scholarly journals Interannual variability of isotopic composition in water vapor over West Africa and its relation to ENSO

2014 ◽  
Vol 14 (17) ◽  
pp. 24441-24474
Author(s):  
A. Okazaki ◽  
Y. Satoh ◽  
G. Tremoy ◽  
F. Vimeux ◽  
R. Scheepmaker ◽  
...  
Keyword(s):  
West Africa ◽  
Isotopic Composition ◽  
Southern Oscillation ◽  
Monsoon Season ◽  
Precipitation Amount ◽  
West African Monsoon ◽  
Isotopic Signature ◽  
Atmospheric Environment ◽  
Global Spectral Model ◽  
Near Surface

Abstract. This study was performed to examine the relationship between isotopic composition in near-surface vapor (δ18Ov) over West Africa during the monsoon season and El Niño–Southern Oscillation (ENSO) activity using the Isotope-incorporated Global Spectral Model. The model was evaluated using a satellite and in situ observations at intraseasonal to interannual timescales. The model provided an accurate simulation of the spatial pattern and seasonal and interannual variations of isotopic composition in column and surface vapor and precipitation over West Africa. Encouraged by this result, a simulation stretching 34 years (1979–2012) was conducted to investigate the relation between atmospheric environment and isotopic signature at the interannual time scale. The simulation indicated that the depletion in the monsoon season does not appear every year at Niamey. The major difference between the composite fields with and without depletion was in the amount of precipitation in the upstream area of Niamey. As the interannual variation of the precipitation amount is influenced by the ENSO, we regressed the monsoon season averaged δ18Ov from the model and annually averaged NINO3 index, and found a statistically significant correlation (R = 0.56, P < 0.01) at Niamey. This relation suggests that there is a possibility of reconstructing past West African monsoon activity and ENSO using climate proxies.

scholarly journals Strong evidence for the continued contribution of lead deposited during the 20th century to the atmospheric environment in London of today

2021 ◽  
Vol 118 (26) ◽  
pp. e2102791118
Author(s):  
Eléonore Resongles ◽  
Volker Dietze ◽  
David C. Green ◽  
Roy M. Harrison ◽  
Raquel Ochoa-Gonzalez ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Lead Isotopes ◽  
Strong Support ◽  
Road Dust ◽  
Isotopic Signature ◽  
Airborne Particles ◽  
Atmospheric Environment ◽  
Anthropogenic Sources ◽  
Leaded Gasoline ◽  
Lead Isotopic Composition

Although leaded gasoline was banned at the end of the last century, lead (Pb) remains significantly enriched in airborne particles in large cities. The remobilization of historical Pb deposited in soils from atmospheric removal has been suggested as an important source providing evidence for the hypothetical long-term persistency of lead, and possibly other pollutants, in the urban environment. Here, we present data on Pb isotopic composition in airborne particles collected in London (2014 to 2018), which provide strong support that lead deposited via gasoline combustion still contributes significantly to the lead burden in present-day London. Lead concentration and isotopic signature of airborne particles collected at a heavily trafficked site did not vary significantly over the last decade, suggesting that sources remained unchanged. Lead isotopic composition of airborne particles matches that of road dust and topsoils and can only be explained with a significant contribution (estimate of 32 ± 10 to 43 ± 9% based on a binary mixing model) of Pb from leaded gasoline. The lead isotopes furthermore suggest significant contributions from nonexhaust traffic emissions, even though isotopic signatures of anthropogenic sources are increasingly overlapping. Lead isotopic composition of airborne particles collected at building height shows a similar signature to that collected at street level, suggesting effective mixing of lead within the urban street canyon. Our results have important implications on the persistence of Pb in urban environments and suggest that atmospheric Pb reached a baseline in London that is difficult to decrease further with present policy measures.

scholarly journals A Continuum Approach to Understanding Changes in the ENSO-Indian Monsoon Relationship

2020 ◽  
pp. 1-49
Author(s):  
Justin Schulte ◽  
Fredrick Policielli ◽  
Benjamin Zaitchik
Keyword(s):  
Southern Oscillation ◽  
Monsoon Season ◽  
Rainfall Variability ◽  
Strongly Correlated ◽  
Sea Surface Temperature Anomalies ◽  
Indian Rainfall ◽  
The 1960S ◽  
June July ◽  
Work Supports ◽  
The Relationship

AbstractIt is well-documented that the relationship between the El Niño/Southern Oscillation (ENSO) and the Indian summer monsoon changes on interdecadal timescales, yet an explanation for the variations is still a subject of debate. Here, using a continuum framework based on one-point partial correlation maps, we show that the ENSO-Indian rainfall relationship is influenced by the gradient of sea surface temperature anomalies (SSTA) across the Niño 3 region. Based on this identified SSTA pattern, a simple trans Niño 3 (TN3) index is created that explains up to 50% of All-India rainfall variability during the mid to late monsoon season after the 1960s. It is also shown that the influence of the TN3 pattern on the relationship between common ENSO metrics and All-India rainfall is strongest during the August-September (AS) monsoon sub-season and weakest during the June-July sub-season. The TN3 pattern accounts for up to 80% of the change and sign reversal in the AS Niño 1+2-All-India rainfall relationship in recent decades. The 1940s coincides with the intensification of the TN3 pattern and its influence. As the TN3 index is nearly orthogonal to the Niño 3 index, and both are strongly correlated with All-India rainfall, the strengthening TN3 influence must be systematically associated with the weakening Niño 3-All-India relationship in recent decades. This work supports arguments that recent changes in the ENSO-Indian rainfall relationship are not solely related to noise.

scholarly journals Natural isotopic composition of nitrogen in suspended particulate matter in the Bay of Bengal

2004 ◽  
Vol 1 (1) ◽  
pp. 63-70 ◽  
Author(s):  
S. Kumar ◽  
R. Ramesh ◽  
N. B. Bhosle ◽  
S. Sardesai ◽  
M. S. Sheshshayee
Keyword(s):  
Particulate Matter ◽  
Isotopic Composition ◽  
Suspended Particulate Matter ◽  
Bay Of Bengal ◽  
Monsoon Season ◽  
Mineral Matter ◽  
Surface Salinity ◽  
Suspended Particulate ◽  
The Relationship

Abstract. We present the first measurement of nitrogen isotopic composition (δ15N) in suspended particulate matter (SPM) of the surface Bay of Bengal (BOB) at 24 different locations during pre- (April–May 2003) and post- (September–October 2002) monsoon seasons. The δ15N of particulate organic nitrogen (PON) in surface suspended matter of coastal as well as northern open BOB shows signatures of a two end-member mixing between continental inputs and marine sources. Dilution by the organic and detrital continental material brought in by rivers leads to consistently lower δ15N, evident from the relationship between surface salinity and δ15N. δ15N of surface PON of open ocean locations during both seasons, and also at coastal locations during pre-monsoon suggest the nitrate from deeper waters as a predominant source of nutrient for planktons. The depth profiles of δ15N of SPM during pre-monsoon season at nine different locations are also presented. These indicate an increase in δ15N by a maximum of 2.8‰ between euphotic depth and 300 m, which is lower than that observed in the eastern Indian Ocean, indicating the role of higher sinking rates of particles ballasted by aggregates of organic and mineral matter in BOB.

scholarly journals 2016 Monsoon Convection and its place in the Large-Scale Circulation using Doppler Radars

2021 ◽  
Author(s):  
Alex Doyle ◽  
Andrew Turner ◽  
Thorwald Stein
Keyword(s):  
Diurnal Cycle ◽  
Large Scale ◽  
Indian Monsoon ◽  
Monsoon Season ◽  
Model Development ◽  
India Meteorological Department ◽  
Convective Cloud ◽  
Atmospheric Environment ◽  
Annual Rainfall ◽  
Near Surface

&lt;p&gt;Convective cloud development during the Indian monsoon helps moisten the atmospheric environment and drive the monsoon trough northwards each year, bringing a large amount of India&amp;#8217;s annual rainfall. Therefore, an increased understanding of how monsoon convection develops in observations will help inform model development. In this study, 139 days of India Meteorological Department Doppler weather radar data is analysed for 7 sites across India during the 2016 monsoon season. Convective cell-top heights (CTH) are objectively identified through the season, and compared with near-surface (at 2 km height) reflectivity. These variables are analysed over three time scales of variability during the monsoon: monsoon progression, active-break periods and the diurnal cycle. We find a modal maximum in CTH around 6&amp;#8211;8 km for all sites. Reflectivity increases with CTH, at first sharply, then less sharply above the freezing level. Bhopal and Mumbai exhibit lower CTH for monsoon break periods compared to active periods. A clear diurnal cycle in CTH is seen at all sites except Mumbai. The phase of the diurnal cycle depends on the surface type being land or ocean for south-eastern India, with the frequency of oceanic cells typically exhibiting an early morning peak compared to those over land, consistent with the observed diurnal cycle of precipitation. The cell characteristics discovered are discussed in light of the differences in large-scale synoptic and mesoscale mechanisms responsible for different cell regimes. Our findings confirm that Indian monsoon convective regimes are partly regulated by the large-scale synoptic environment within which they are embedded.&lt;/p&gt;

scholarly journals Multiannual observations and modelling of seasonal thermal profiles through supraglacial debris in the Central Himalaya

2017 ◽  
Author(s):  
Ann V. Rowan ◽  
Lindsey Nicholson ◽  
Emily Collier ◽  
Duncan J. Quincey ◽  
Morgan J. Gibson ◽  
...  
Keyword(s):  
Mass Loss ◽  
Summer Monsoon ◽  
Monsoon Season ◽  
Mass Change ◽  
Temperature Profiles ◽  
Central Himalaya ◽  
Summer Monsoon Season ◽  
Near Surface ◽  
The Relationship ◽  
Rapid Mass

Abstract. Many glaciers in the Central Himalaya are covered with rock debris that modifies the transfer of heat from the atmosphere to the underlying ice. These debris-covered glaciers are experiencing rapid mass loss at rates that have accelerated during the last two decades. Quantifying recent and future glacier mass change requires understanding the relationship between debris thickness and ablation particularly through the summer monsoon season. We present air, near-surface and debris temperatures measured during three monsoon seasons at five sites on Khumbu Glacier in Nepal, and compare these results to similar measurements from two other debris-covered glaciers in this region. Seasonal debris temperature profiles are approximately linear and consistent between sites for thick (> 0.5 m) and thin (

scholarly journals A re-examination of ENSO/ anti-ENSO events and simultaneous performance of the Indian summer monsoon

MAUSAM ◽  
2021 ◽  
Vol 47 (1) ◽  
pp. 59-66
Author(s):  
J. CHATTOPADHYAY ◽  
R. BHATLA
Keyword(s):  
Monsoon Rainfall ◽  
Southern Oscillation ◽  
Monsoon Season ◽  
Strong Association ◽  
Enso Events ◽  
The Pacific ◽  
Degree Of Confidence ◽  
High Degree ◽  
The Relationship ◽  
Very High

The relationship between ENSO/anti-ENSO events in the Pacific basin and simultaneous all India monsoon has been re-examined for the period 1901-1990 using Southern Oscillation Index (SOI). The result shows that there is fairly strong association between ENSO events and dry monsoon years. There exists a weak teleconnection between anti-ENSO events and wet monsoon indicating that anti-ENSO events have only a moderate impact on the Indian monsoon rainfall. Developing ENSO (anti-ENSO) episodes during the monsoon season indicates non-occurrence of simultaneous floods (droughts) with a very high degree of confidence 70 (50) percent of the droughts (floods) during the above period have occurred during ENSO (anti-ENSO) events indicating that extreme monsoon activities in the form of droughts (floods) might be important factors for the occurrence of simultaneous ENSO/anti-ENSO events.

scholarly journals Natural isotopic composition of nitrogen in suspended particulate matter in the Bay of Bengal

2004 ◽  
Vol 1 (1) ◽  
pp. 87-105 ◽  
Author(s):  
S. Kumar ◽  
R. Ramesh ◽  
N. B. Bhosle ◽  
S. Sardesai ◽  
M. S. Sheshshayee
Keyword(s):  
Particulate Matter ◽  
Isotopic Composition ◽  
Suspended Particulate Matter ◽  
Bay Of Bengal ◽  
Monsoon Season ◽  
Mineral Matter ◽  
Surface Salinity ◽  
Suspended Particulate ◽  
The Relationship

Abstract. We present the first measurement of nitrogen isotopic composition (δ15N) in suspended particulate matter (SPM) of the surface Bay of Bengal (BOB) at 24 different locations during pre- (April–May 2003) and post- (September–October 2002) monsoon seasons. The δ15N of particulate organic nitrogen (PON) in surface suspended matter of coastal as well as northern open BOB shows signatures of a two end-member mixing between continental inputs and marine sources. Dilution by the organic and detrital continental material brought in by rivers leads to consistently lower δ15N, evident from the relationship between surface salinity and δ15N. δ15N of surface PON of open ocean locations during both seasons, and also at coastal locations during pre-monsoon suggest the nitrate from deeper waters as a predominant source of nutrient for planktons. The depth profiles of δ15N of SPM during pre-monsoon season at nine different locations are also presented. These indicate an increase in δ15N by a maximum of 2.8‰ between euphotic depth and 300 m, which is lower than that observed in the eastern Indian Ocean, indicating the role of higher sinking rates of particles ballasted by aggregates of organic and mineral matter in BOB.

Rendimento de grãos de soja e de milho, no Rio Grande do Sul, não difere entre eventos El Niño Oscilação Sul

Agrometeoros ◽  
2018 ◽  
Vol 26 (1) ◽  
Author(s):  
Ronaldo Matzenauer ◽  
Bernadete Radin ◽  
Alberto Cargnelutti Filho
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Rio Grande ◽  
La Niña ◽  
Rio Grande Do Sul ◽  
La Nina ◽  
Significant Difference ◽  
Income Data ◽  
The Relationship

O objetivo deste trabalho foi avaliar a relação entre o fenômeno El Niño Oscilação Sul - ENOS e o rendimento de grãos de soja e de milho no Rio Grande do Sul e verificar a hipótese de que os eventos El Niño são favoráveis e os eventos La Niña são prejudiciais ao rendimento de grãos das culturas. Foram utilizados dados de rendimento de grãos dos anos agrícolas de 1974/75 a 2016/17, e relacionados com as ocorrências de eventos ENOS. Foram analisados os dados de rendimento observados na colheita e os dados estimados com a remoção da tendência tecnológica. Os resultados mostraram que não houve diferença significativa do rendimento médio de grãos de soja e de milho na comparação entre os eventos ENOS. Palavras-chave: El Niño, La Niña, safras agrícolas. Abstract – The objective of this work was to evaluate the relationship between the El Niño Southern Oscillation (ENSO) phenomenon with the grain yield of soybean and maize in Rio Grande do Sul state, Brazil and to verify the hypothesis that the El Niño events are favorable and the La Niña events are harmful to the culture’s grain yields. Were used data from the agricultural years of 1974/75 to 2016/17, and related to the occurrence of ENOS events. We analyzed income data observed at harvest and estimated data with technological tendency was removed. The results showed that there was no significant difference in the average yield of soybeans and corn in the comparison between events.

scholarly journals The evolving response of mesopelagic fishes to declining midwater oxygen concentrations in the southern and central California Current

2018 ◽  
Vol 76 (3) ◽  
pp. 626-638 ◽  
Author(s):  
J Anthony Koslow ◽  
Pete Davison ◽  
Erica Ferrer ◽  
S Patricia A Jiménez Rosenberg ◽  
Gerardo Aceves-Medina ◽  
...  
Keyword(s):  
Baja California ◽  
Southern Oscillation ◽  
Global Climate ◽  
California Current ◽  
Deep Ocean ◽  
Near Surface ◽  
Oxygen Minimum Zones ◽  
The North ◽  
The Pacific ◽  
Oxygen Concentrations

Abstract Declining oxygen concentrations in the deep ocean, particularly in areas with pronounced oxygen minimum zones (OMZs), are a growing global concern related to global climate change. Its potential impacts on marine life remain poorly understood. A previous study suggested that the abundance of a diverse suite of mesopelagic fishes off southern California was closely linked to trends in midwater oxygen concentration. This study expands the spatial and temporal scale of that analysis to examine how mesopelagic fishes are responding to declining oxygen levels in the California Current (CC) off central, southern, and Baja California. Several warm-water mesopelagic species, apparently adapted to the shallower, more intense OMZ off Baja California, are shown to be increasing despite declining midwater oxygen concentrations and becoming increasingly dominant, initially off Baja California and subsequently in the CC region to the north. Their increased abundance is associated with warming near-surface ocean temperature, the warm phase of the Pacific Decadal oscillation and Multivariate El Niño-Southern Oscillation Index, and the increased flux of Pacific Equatorial Water into the southern CC.

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