Dust Accumulation Biases in PIRATA Shortwave Radiation Records*

2013 ◽  
Vol 30 (7) ◽  
pp. 1414-1432 ◽  
Author(s):  
Gregory R. Foltz ◽  
Amato T. Evan ◽  
H. Paul Freitag ◽  
Sonya Brown ◽  
Michael J. McPhaden
Keyword(s):  
North Atlantic ◽  
Numerical Models ◽  
Dust Concentration ◽  
Shortwave Radiation ◽  
Dust Deposition ◽  
Atmospheric Dust ◽  
The North ◽  
Direct Measurements ◽  
High Dust ◽  
Dust Accumulation

Abstract Long-term and direct measurements of surface shortwave radiation (SWR) have been recorded by the Prediction and Research Moored Array in the Tropical Atlantic (PIRATA) since 1997. Previous studies have shown that African dust, transported westward from the Sahara and Sahel regions, can accumulate on mooring SWR sensors in the high-dust region of the North Atlantic (8°–25°N, 20°–50°W), potentially leading to significant negative SWR biases. Here dust-accumulation biases are quantified for each PIRATA mooring using direct measurements from the moorings, combined with satellite and reanalysis datasets and statistical models. The SWR records from five locations in the high-dust region (8°, 12°, and 15°N along 38°W; 12° and 21°N along 23°W) are found to contain monthly-mean accumulation biases as large as −200 W m−2 and record-length mean biases on the order of −10 W m−2. The other 12 moorings, located mainly between 10°S and 4°N, are in regions of lower atmospheric dust concentration and do not show statistically significant biases. Seasonal-to-interannual variability of the accumulation bias is found at all locations in the high-dust region. The moorings along 38°W also show decreasing trends in the bias magnitude since 1998 that are possibly related to a corresponding negative trend in atmospheric dust concentration. The dust-accumulation biases described here will be useful for interpreting SWR data from PIRATA moorings in the high-dust region. The biases are also potentially useful for quantifying dust deposition rates in the tropical North Atlantic, which at present are poorly constrained by satellite data and numerical models.

scholarly journals The link between marine sediment records and changes in Holocene Saharan landscape: simulating the dust cycle

2016 ◽  
Vol 12 (4) ◽  
pp. 1009-1027 ◽  
Author(s):  
Sabine Egerer ◽  
Martin Claussen ◽  
Christian Reick ◽  
Tanja Stanelle
Keyword(s):  
North Atlantic ◽  
Marine Sediment ◽  
Land Surface ◽  
Surface Characteristics ◽  
Dust Deposition ◽  
Surface Cover ◽  
The North ◽  
Sediment Records ◽  
The North Atlantic ◽  
Dust Accumulation

Abstract. Marine sediment records reveal an abrupt and strong increase in dust deposition in the North Atlantic at the end of the African Humid Period about 4.9 to 5.5 ka ago. The change in dust flux has been attributed to varying Saharan land surface cover. Alternatively, the enhanced dust accumulation is linked to enhanced surface winds and a consequent intensification of coastal upwelling. Here we demonstrate for the first time the direct link between dust accumulation in marine cores and changes in Saharan land surface. We simulate the mid-Holocene (6 ka BP) and pre-industrial (1850 AD) dust cycle as a function of Saharan land surface cover and atmosphere-ocean conditions using the coupled atmosphere–aerosol model ECHAM6.1-HAM2.1. Mid-Holocene surface characteristics, including vegetation cover and lake surface area, are derived from proxy data and simulations. In agreement with data from marine sediment cores, our simulations show that mid-Holocene dust deposition fluxes in the North Atlantic were two to three times lower compared with pre-industrial fluxes. We identify Saharan land surface characteristics to be the main control on dust transport from North Africa to the North Atlantic. We conclude that the increase in dust accumulation in marine cores is directly linked to a transition of the Saharan landscape during the Holocene and not due to changes in atmospheric or ocean conditions alone.

Recent dust variability over South Asia controlled by North Atlantic SST anomalies

2021 ◽  
Author(s):  
Priyanka Banerjee ◽  
Sreedharan Krishnakumari Satheesh ◽  
Krishnaswamy Krishna Moorthy
Keyword(s):  
South Asia ◽  
South Asian ◽  
North Atlantic ◽  
Asian Monsoon ◽  
Positive Phase ◽  
South Asian Monsoon ◽  
The North ◽  
Sst Anomaly ◽  
The North Atlantic ◽  
High Dust

<p>Several studies have associated high dust years over South Asia to warming of the central or eastern equatorial Pacific Ocean (El Nino conditions) and the resulting weakening of the summer monsoon. Using satellite aerosol data for 2001-2018, we show that there has been a departure from this relation since the second decade of the 21st century with the North Atlantic Ocean emerging as a major driver of interannual variability of dust over South Asia. This change in relation coincides with the end of the global warming hiatus and a shift towards persistent positive phase of the winter North Atlantic Oscillation (NAO). Positive phase of the NAO induces cold phase of the spring/summer North Atlantic sea surface temperature (SST) tripole pattern. We show here that high dust activity during 2011-2018 is associated with positive SST anomaly over the mid-latitude North Atlantic and negative SST anomaly over the sub-tropical North Atlantic: the two southern arms of the SST tripole pattern. Interestingly, the relation between NAO and these two southern arms of the SST tripole has undergone changes in recent years, which has impacted the South Asian monsoon. The result is general drying over South Asia and an increase in the strength of the dust-carrying northwesterlies. Simulations with the Community Earth System Model (CESM) shows that SST tripole-like anomalies recorded during 2011-2018 over the North Atlantic can generate mid-latitude wave train that weakens the South Asian monsoon circulation, leads to surface high pressure anomalies and increase in dust emission and transport over northwest India and Pakistan. Most of the increase in the dust load can be attributed to enhanced transport at 800 hPa pressure level during May-June, which can lead to ~40-50% increase in dust concentrations at this level.</p>

scholarly journals The North Atlantic Marine Boundary Layer Experiment(NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002

2006 ◽  
Vol 6 (8) ◽  
pp. 2241-2272 ◽  
Author(s):  
D. E. Heard ◽  
K. A. Read ◽  
J. Methven ◽  
S. Al-Haider ◽  
W. J. Bloss ◽  
...  
Keyword(s):  
Boundary Layer ◽  
North Atlantic ◽  
Marine Boundary Layer ◽  
Numerical Models ◽  
Measurement Data ◽  
Air Mass ◽  
The North ◽  
Trace Species ◽  
Wide Range ◽  
The North Atlantic

Abstract. The North Atlantic Marine Boundary Layer Experiment (NAMBLEX), involving over 50 scientists from 12 institutions, took place at Mace Head, Ireland (53.32° N, 9.90° W), between 23 July and 4 September 2002. A wide range of state-of-the-art instrumentation enabled detailed measurements of the boundary layer structure and atmospheric composition in the gas and aerosol phase to be made, providing one of the most comprehensive in situ studies of the marine boundary layer to date. This overview paper describes the aims of the NAMBLEX project in the context of previous field campaigns in the Marine Boundary Layer (MBL), the overall layout of the site, a summary of the instrumentation deployed, the temporal coverage of the measurement data, and the numerical models used to interpret the field data. Measurements of some trace species were made for the first time during the campaign, which was characterised by predominantly clean air of marine origin, but more polluted air with higher levels of NOx originating from continental regions was also experienced. This paper provides a summary of the meteorological measurements and Planetary Boundary Layer (PBL) structure measurements, presents time series of some of the longer-lived trace species (O3, CO, H2, DMS, CH4, NMHC, NOx, NOy, PAN) and summarises measurements of other species that are described in more detail in other papers within this special issue, namely oxygenated VOCs, HCHO, peroxides, organo-halogenated species, a range of shorter lived halogen species (I2, OIO, IO, BrO), NO3 radicals, photolysis frequencies, the free radicals OH, HO2 and (HO2+Σ RO2), as well as a summary of the aerosol measurements. NAMBLEX was supported by measurements made in the vicinity of Mace Head using the NERC Dornier-228 aircraft. Using ECMWF wind-fields, calculations were made of the air-mass trajectories arriving at Mace Head during NAMBLEX, and were analysed together with both meteorological and trace-gas measurements. In this paper a chemical climatology for the duration of the campaign is presented to interpret the distribution of air-mass origins and emission sources, and to provide a convenient framework of air-mass classification that is used by other papers in this issue for the interpretation of observed variability in levels of trace gases and aerosols.

The Intra-Americas Springtime Sea Surface Temperature Anomaly Dipole as Fingerprint of Remote Influences

2010 ◽  
Vol 23 (1) ◽  
pp. 43-56 ◽  
Author(s):  
Ernesto Muñoz ◽  
Chunzai Wang ◽  
David Enfield
Keyword(s):  
Gulf Of Mexico ◽  
North Atlantic ◽  
Caribbean Sea ◽  
Enso Event ◽  
Shortwave Radiation ◽  
Teleconnection Patterns ◽  
The North ◽  
The Pacific ◽  
Sst Anomaly ◽  
The Caribbean

Abstract The influence of teleconnections on the Intra-Americas Sea (IAS; Gulf of Mexico and Caribbean Sea) has been mostly analyzed from the perspective of El Niño–Southern Oscillation (ENSO) on the Caribbean Sea (the latter being an extension of the tropical North Atlantic). This emphasis has overlooked both 1) the influence of other teleconnections on the IAS and 2) which teleconnections affect the Gulf of Mexico climate variability. In this study the different fingerprints that major teleconnection patterns have on the IAS during boreal spring are analyzed. Indices of teleconnection patterns are regressed and correlated to observations of oceanic temperature and atmospheric data from reanalyses and observational datasets. It is found that the Pacific teleconnection patterns that influence the IAS SSTs do so by affecting the Gulf of Mexico in an opposite manner to the Caribbean Sea. These analyzed Pacific climate patterns are the Pacific–North American (PNA) teleconnection, the Pacific decadal oscillation (PDO), and ENSO. The North Atlantic Oscillation (NAO) is related to a lesser degree with the north–south SST anomaly dipole than are Pacific teleconnection patterns. It is also found that the IAS influence from the midlatitude Pacific mostly affects the Gulf of Mexico, whereas the influence from the tropical Pacific mostly affects the Caribbean Sea. Therefore, the combination of a warm ENSO event and a positive PNA event induces a strong IAS SST anomaly dipole between the Gulf of Mexico and the Caribbean Sea during spring. By calculating an index that represents the IAS SST anomaly dipole, it is found that the dipole forms mostly in response to changes in the air–sea heat fluxes. In the Gulf of Mexico the dominant mechanisms are the air–sea differences in humidity and temperature. The changes in shortwave radiation also contribute to the dipole of net air–sea heat flux. The changes in shortwave radiation arise, in part, by the cloudiness triggered by the air–sea differences in humidity, and also by the changes in the convection cell that connects the Amazon basin to the IAS. Weaker Amazon convection (e.g., in the event of a warm ENSO event) reduces the subsidence over the IAS, and henceforth the IAS cloudiness increases (and the shortwave radiation decreases). This study contributes to a greater understanding of how the IAS is influenced by different Pacific and Atlantic teleconnections.

scholarly journals Twelve thousand years of dust: the Holocene global dust cycle constrained by natural archives

2014 ◽  
Vol 10 (6) ◽  
pp. 4277-4363 ◽  
Author(s):  
S. Albani ◽  
N. M. Mahowald ◽  
G. Winckler ◽  
R. F. Anderson ◽  
L. I. Bradtmiller ◽  
...  
Keyword(s):  
North Atlantic ◽  
Accumulation Rates ◽  
Dust Deposition ◽  
The Holocene ◽  
The North ◽  
Dust Mass ◽  
The North Atlantic ◽  
Mass Accumulation Rates ◽  
Mass Accumulation ◽  
Natural Archives

Abstract. Mineral dust plays an important role in the climate system by interacting with radiation, clouds, and biogeochemical cycles. In addition, natural archives show that the dust cycle experienced variability in the past in response to global and local climate change. The compilation of the DIRTMAP paleodust datasets in the last two decades provided a target for paleoclimate models that include the dust cycle, following a time slice approach. We propose an innovative framework to organize a paleodust dataset that moves on from the positive experience of DIRTMAP and takes into account new scientific challenges, by providing a concise and accessible dataset of temporally resolved records of dust mass accumulation rates and particle grain-size distributions. We consider data from ice cores, marine sediments, loess/paleosol sequences, lake sediments, and peat bogs for this compilation, with a temporal focus on the Holocene period. This global compilation allows investigation of the potential, uncertainties and confidence level of dust mass accumulation rates reconstructions, and highlights the importance of dust particle size information for accurate and quantitative reconstructions of the dust cycle. After applying criteria that help to establish that the data considered represent changes in dust deposition, 43 paleodust records have been identified, with the highest density of dust deposition data occurring in the North Atlantic region. Although the temporal evolution of dust in the North Atlantic appears consistent across several cores and suggest that minimum dust fluxes are likely observed during the Early to mid-Holocene period (6000–8000 years ago), the magnitude of dust fluxes in these observations is not fully consistent, suggesting that more work needs to be done to synthesize datasets for the Holocene. Based on the data compilation, we used the Community Earth System Model to estimate the mass balance and variability of the global dust cycle during the Holocene, with dust load ranging from 17.1 to 20.5 Tg between 2000 and 10 000 years ago, and a minimum in the Early to Mid-Holocene (6000–8000 years ago).

scholarly journals An experimental study of the Atlantic variability on interdecadal timescales

2012 ◽  
Vol 19 (3) ◽  
pp. 335-343 ◽  
Author(s):  
M. Vincze ◽  
I. M. Jánosi ◽  
E. Barsy ◽  
T. Tél ◽  
A. Várai
Keyword(s):  
North Atlantic ◽  
Laboratory Experiments ◽  
Thermal Noise ◽  
Numerical Models ◽  
Low Frequency ◽  
Atlantic Multidecadal Variability ◽  
Multidecadal Variability ◽  
Sector Model ◽  
The North ◽  
Low Frequency Variability

Abstract. A series of laboratory experiments has been carried out to model the basic dynamics of the multidecadal variability observed in North Atlantic sea surface temperature (SST) records. According to the minimal numerical sector model introduced by te Raa and Dijkstra (2002), the three key components to excite such a low-frequency variability are rotation, meridional temperature gradient and additive thermal noise in the surface heat forcing. If these components are present, periodic perturbations of the overturning background flow are excited, leading to thermal Rossby mode like propagation of anomalous patches in the SST field. Our tabletop scale setup was built to capture this phenomenon, and to test whether the aforementioned three components are indeed sufficient to generate a low-frequency variability in the system. The results are compared to those of the numerical models, as well as to oceanic SST reanalysis records. To the best of our knowledge, the experiment described here is the very first to investigate the dynamics of the North Atlantic multidecadal variability in a laboratory-scale setup.

scholarly journals The Record-Breaking High Temperature over Europe in June of 2019

Atmosphere ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 524 ◽  
Author(s):  
Wei Zhao ◽  
Ningfang Zhou ◽  
Shangfeng Chen
Keyword(s):  
High Temperature ◽  
North Atlantic ◽  
Wave Train ◽  
Surface Air Temperature ◽  
Shortwave Radiation ◽  
The North ◽  
Atmospheric Wave ◽  
Local Soil ◽  
Anomalous Anticyclone ◽  
The North Atlantic

Observational and reanalysis data show that the surface air temperature (SAT) over most parts of Europe in June of 2019 broke the highest temperature on record. In this study, we investigate the factors for the formation of this record-breaking high temperature over Europe, focusing on the role of atmospheric circulation anomalies. A strong anomalous anticyclone appeared over Europe, with a quasi-barotropic vertical structure. On one hand, the downward motion anomalies associated with this anomalous anticyclone led to less cloud cover and an increase in downward shortwave radiation, which contributed to the SAT warming over Europe. On the other hand, southerly wind anomalies to the west side of the anomalous anticyclone also resulted in SAT warming via carrying warmer and wetter air northward from lower latitudes. The formation of the anticyclonic anomaly over Europe in June of 2019 was closely related to an atmospheric wave train propagating eastward from the mid-high latitudes of the North Atlantic to Eurasia. The atmospheric wave train over the North Atlantic–Eurasia region is suggested to be mainly related to the Atlantic–Eurasia teleconnection pattern. Further analysis indicates that a decrease in the local soil moisture over Europe may also have escalated the surface temperature warming through a positive land–atmosphere feedback.

scholarly journals Holocene atmospheric dust deposition in NW Spain

The Holocene ◽  
2019 ◽  
Vol 30 (4) ◽  
pp. 507-518 ◽  
Author(s):  
Antonio Martínez Cortizas ◽  
Olalla López-Costas ◽  
Lisa Orme ◽  
Tim Mighall ◽  
Malin E Kylander ◽  
...  
Keyword(s):  
North Atlantic ◽  
Arid Regions ◽  
Dust Deposition ◽  
Atmospheric Dust ◽  
Raised Bog ◽  
Complex Interactions ◽  
Dust Events ◽  
Forest Stability ◽  
Atmospheric Dust Deposition ◽  
Complex Geology

Atmospheric dust plays an important role in terrestrial and marine ecosystems, particularly those that are nutrient limited. Despite that most dust originates from arid and semi-arid regions, recent research has shown that past dust events may have been involved in boosting productivity in nutrient-poor peatlands. We investigated dust deposition in a mid-latitude, raised bog, which is surrounded by a complex geology (paragneiss/schist, granite, quartzite and granodiorite). As proxies for dust fluxes, we used accumulation rates of trace (Ti, Zr, Rb, Sr and Y) as well as major (K and Ca) lithogenic elements. The oldest, largest dust deposition event occurred between ~8.6 and ~7.4 ka BP, peaking at ~8.1 ka BP (most probably the 8.2 ka BP event). The event had a large impact on the evolution of the mire, which subsequently transitioned from a fen into a raised bog in ~1500 years. From ~6.7 to ~4.0 ka BP, fluxes were very low, coeval with mid-Holocene forest stability and maximum extent. In the late Holocene, after ~4.0 ka BP, dust events became more prevalent with relatively major deposition at ~3.2–2.5, ~1.4 ka BP and ~0.35–0.05 ka BP, and minor peaks at ~4.0–3.7, ~1.7, ~1.10–0.95 ka BP and ~0.74–0.58 ka BP. Strontium fluxes display a similar pattern between ~11 and ~6.7 ka BP but then became decoupled from the other elements from the mid Holocene onwards. This seems to be a specific signal of the granodiorite batholith, which has an Sr anomaly. The reconstructed variations in dust fluxes bear a strong climatic imprint, probably related to storminess controlled by North Atlantic Oscillation conditions. Complex interactions also arise because of increased pressure from human activities.

scholarly journals Marine sediment records as indicator for the changes in Holocene Saharan landscape: simulating the dust cycle

2015 ◽  
Vol 11 (6) ◽  
pp. 5269-5306 ◽  
Author(s):  
S. Egerer ◽  
M. Claussen ◽  
C. Reick ◽  
T. Stanelle
Keyword(s):  
North Atlantic ◽  
Marine Sediment ◽  
Land Surface ◽  
Surface Characteristics ◽  
Dust Deposition ◽  
Surface Cover ◽  
The North ◽  
Sediment Records ◽  
The North Atlantic ◽  
Ocean Conditions

Abstract. Marine sediment records reveal an abrupt and strong increase in dust deposition in the North Atlantic at the end of the African Humid Period about 5500 years ago. The change in dust flux has been attributed to varying Saharan land surface cover. Alternatively, variability in climate and ocean conditions, for example changes in sea surface temperature, have been proposed to explain the enhanced dust deposition. Here we demonstrate for the first time the direct link between dust accumulation in marine cores and Saharan land surface. We simulate the mid-Holocene (6 ka BP) and pre-industrial (1850 AD) dust cycle as a function of Saharan land surface cover and atmosphere–ocean conditions using the coupled atmosphere-aerosol model ECHAM6-HAM2.1. Mid-Holocene surface characteristics, including vegetation cover and lake surface area, are derived from proxy data and simulations. In agreement with data from marine sediment cores, our simulations show that mid-Holocene dust deposition fluxes in the North Atlantic were two to three times lower compared with pre-industrial fluxes. We identify Saharan land surface characteristics to be the main control on dust transport from North Africa to the North Atlantic. We conclude that the variation in dust accumulation in marine cores is likely related to a transition of the Saharan landscape during the Holocene and not due to changes in atmospheric or ocean conditions.

scholarly journals The North Atlantic Marine Boundary Layer Experiment (NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002

2005 ◽  
Vol 5 (6) ◽  
pp. 12177-12254 ◽  
Author(s):  
D. E. Heard ◽  
K. A. Read ◽  
J. Methven ◽  
S. Al-Haider ◽  
W. J. Bloss ◽  
...  
Keyword(s):  
Boundary Layer ◽  
North Atlantic ◽  
Marine Boundary Layer ◽  
Numerical Models ◽  
Measurement Data ◽  
Air Mass ◽  
The North ◽  
Trace Species ◽  
Wide Range ◽  
The North Atlantic

Abstract. The North Atlantic Marine Boundary Layer Experiment (NAMBLEX), involving over 50 scientists from 12 institutions, took place at Mace Head, Ireland (53.32° N, 9.90° W), between 23 July and 4 September 2002. A wide range of state-of-the-art instrumentation enabled detailed measurements of the boundary layer structure and atmospheric composition in the gas and aerosol phase to be made, providing one of the most comprehensive in situ studies of the marine boundary layer to date. This overview paper describes the aims of the NAMBLEX project in the context of previous field campaigns in the Marine Boundary Layer (MBL), the overall layout of the site, a summary of the instrumentation deployed, the temporal coverage of the measurement data, and the numerical models used to interpret the field data. Measurements of some trace species were made for the first time during the campaign, which was characterised by predominantly clean air of marine origin, but more polluted air with higher levels of NOx originating from continental regions was also experienced. This paper provides a summary of the meteorological measurements and Planetary Boundary Layer (PBL) structure measurements, presents time series of some of the longer-lived trace species (O3, CO, H2, DMS, CH4, NMHC, NOx, NOy, PAN) and summarises measurements of other species that are described in more detail in other papers within this special issue, namely oxygenated VOCs, HCHO, peroxides, organo-halogenated species, a range of shorter lived halogen species (I2, OIO, IO, BrO), NO3 radicals, photolysis frequencies, the free radicals OH, HO2 and (HO2+ΣRO2), as well as a summary of the aerosol measurements. NAMBLEX was supported by measurements made in the vicinity of Mace Head using the NERC Dornier-228 aircraft. Using ECMWF wind-fields, calculations were made of the air-mass trajectories arriving at Mace Head during NAMBLEX, and were analysed together with both meteorological and trace-gas measurements. In this paper a chemical climatology is presented to interpret the distribution of air-mass origins and emission sources, and to provide a convenient framework of air-mass classification that is used by other papers in this issue for the interpretation of observed variability in levels of trace gases and aerosols.

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