Modeling dust sources, transport, and radiative effects at different altitudes over the Tibetan Plateau

Abstract. Mineral dust plays an important role in the climate of the Tibetan Plateau (TP) by modifying the radiation budget, cloud macro- and microphysics, precipitation, and snow albedo. Meanwhile, the TP with the highest topography in the word can affect intercontinental transport of dust plumes and induce typical distribution characteristics of dust at different altitudes. In this study, we conduct a quasi-global simulation to investigate the characteristics of dust source contribution and transport over the TP at different altitude by using a fully coupled meteorology–chemistry model (WRF–Chem) with a tracer-tagging technique. Generally, the simulation reasonably captures the spatial distribution of satellite retrieved dust aerosol optical depth (AOD) at different altitudes. Model results show that dust particles are emitted into atmosphere through updrafts over major desert regions, and then transported to the TP. The East Asian dust is transported and lifted up to the TP, contributing a mass loading of 50 mg/m2 at 3 km height and 5 mg/m2 at 12 km height over the northern slop of the TP. Dust from North Africa and Middle East are concentrated over both northern and southern slopes below 6 km, where mass loadings range from 10 to 100 mg/m2 and 1 to 10 mg/m2 below 3 km and above 9 km, respectively. As the dust is transported to the north and over the TP, mass loadings are 5–10 mg/m2 above 6 km. The imported dust mass flux from East Asia to the TP is 7.9 Tg/year mostly occuring at the heights of 3–6 km. The North African and Middle East dust particles are transported eastward following the westerly jet, and then imported into the TP at West side with the dust mass flux of 7.8 and 26.6 Tg/year, respectively. The maximum mass flux of the North African dust mainly occurs in 0–3 km (3.9 Tg/year), while the Middle East within 6–9 km (12.3 Tg/year). The dust outflow occurs at East side (−17.89 Tg/year) and South side (−11.22 Tg/year) of the TP with a peak value (8.7 Tg/year) in 6–9 km. Moreover, the dust mass is within the size range of 1.25~5.0 μm and dust number is concentrated in the size range of 0.156~1.25 μm. Compared with other aerosols, the dust contributes more than 50 % to the total AOD over the TP. The direct radiative forcing induced by the dust is −1.28 W/m2 at the top of the atmosphere (cooling), 0.41 W/m2 in the atmosphere (warming) and −1.68 W/m2 at the surface (cooling). Our quantitative analyses of the dust contribution from different source regions and the associated radiative forcing can help better understand the role of dust on the climate over the TP and surrounding regions.

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Modeling dust sources, transport, and radiative effects at different altitudes over the Tibetan Plateau

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-1507-2020 ◽

2020 ◽

Vol 20 (3) ◽

pp. 1507-1529 ◽

Cited By ~ 5

Author(s):

Zhiyuan Hu ◽

Jianping Huang ◽

Chun Zhao ◽

Qinjian Jin ◽

Yuanyuan Ma ◽

...

Keyword(s):

Tibetan Plateau ◽

North Africa ◽

Mass Flux ◽

Radiative Forcing ◽

Size Range ◽

Dust Particles ◽

The Tibetan Plateau ◽

The North ◽

Dust Mass ◽

Different Altitudes

Abstract. Mineral dust plays an important role in the climate of the Tibetan Plateau (TP) by modifying the radiation budget, cloud macro- and microphysics, precipitation, and snow albedo. Meanwhile, the TP, with the highest topography in the world, can affect intercontinental transport of dust plumes and induce typical distribution characteristics of dust at different altitudes. In this study, we conduct a quasi-global simulation to investigate the characteristics of dust source contribution and transport over the TP at different altitudes by using a fully coupled meteorology–chemistry model, the Weather Research and Forecasting model with chemistry (WRF-Chem), with a tracer-tagging technique. Generally, the simulation reasonably captures the spatial distribution of satellite-retrieved dust aerosol optical depth (AOD) at different altitudes. Model results show that dust particles are emitted into atmosphere through updrafts over major desert regions and then transported to the TP. The East Asian dust (mainly from the Gobi and Taklamakan deserts) is transported southward and is lifted up to the TP, contributing a mass loading of 50 mg m−2 at a height of 3 km and 5 mg m−2 at a height of 12 km over the northern slope of the TP. Dust from North Africa and the Middle East are concentrated over both of the northern and southern slopes below 6 km, where mass loadings range from 10 to 100 and 1 to 10 mg m−2 below 3 km and above 9 km, respectively. As the dust is transported to the north and over the TP, mass loadings are 5–10 mg m−2 above a height of 6 km. The dust mass flux carried from East Asia to the TP is 7.9 Tg yr−1, mostly occurring at heights of 3–6 km. The dust particles from North Africa and the Middle East are transported eastward following the westerly jet and then are carried into the TP at the west side with dust mass fluxes of 7.8 and 26.6 Tg yr−1, respectively. The maximum mass flux of the North African dust mainly occurs at 0–3 km (3.9 Tg yr−1), while the Middle Eastern dust occurs at 6–9 km (12.3 Tg yr−1). The dust outflow occurs on the east side (−17.89 Tg yr−1) and south side (−11.22 Tg yr−1) of the TP, with a peak value (8.7 Tg yr−1) at 6–9 km. Moreover, the dust (by mass) is concentrated within the size range of 1.25–5.0 µm and the dust (by particle number) is concentrated in the size range of 0.156–1.25 µm. Compared with other aerosols, the dust contributes to more than 50 % of the total AOD over the TP. The direct radiative forcing induced by the dust is −1.28 W m−2 at the top of the atmosphere (cooling), 0.41 W m−2 in the atmosphere (warming), and −1.68 W m−2 at the surface (cooling). Our quantitative analyses of the dust contributions from different source regions and the associated radiative forcing can help us to better understand the role of dust on the climate over the TP and surrounding regions.

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Modeling dust sources, transport, and radiative effects at different altitudes over the Tibetan Plateau

10.5194/egusphere-egu2020-12123 ◽

2020 ◽

Author(s):

Zhiyuan Hu ◽

Jianping Huang ◽

Chun Zhao ◽

Qinjian Jin ◽

Yuanyuan Ma ◽

...

Keyword(s):

Middle East ◽

Tibetan Plateau ◽

Mass Flux ◽

Radiation Budget ◽

Dust Particles ◽

The Tibetan Plateau ◽

North African ◽

The North ◽

Dust Mass ◽

Different Altitudes

Mineral dust plays an important role in the climate of the Tibetan Plateau (TP) by modifying the radiation budget, cloud macro- and microphysics, precipitation, and snow albedo. Meanwhile, the TP with the highest topography in the word can affect intercontinental transport of dust plumes and induce typical distribution characteristics of dust at different altitudes. In this study, we conduct a quasi-global simulation to investigate the characteristics of dust source contribution and transport over the TP at different altitude by using a fully coupled meteorology-chemistry model (WRF-Chem) with a tracer-tagging technique. Generally, the simulation reasonably captures the spatial distribution of satellite retrieved dust aerosol optical depth (AOD) at different altitudes. Model results show that dust particles are emitted into atmosphere through updrafts over major desert regions, and then transported to the TP. The East Asian dust (mainly from Gobi and Taklamakan deserts) transports southward and is lifted up to the TP, contributing a mass loading of 50 mg/m2 at 3 km height and 5 mg/m2 at 12 km height over the northern slop of the TP. Dust from North Africa and Middle East are concentrated over both northern and southern slopes below 6 km, where mass loadings range from 10 to 100mg/m2 and 1 to 10 mg/m2 below 3 km and above 9 km, respectively. As the dust is transported to the north and over the TP, mass loadings are 5-10 mg/m2 above 6 km.The imported dust mass flux from East Asia to the TP is 7.9 Tg/year mostly occuring at the heights of 3&#8211;6 km. The North African and Middle East dust particles are transported eastward following the westerly jet, and then imported into the TP at West side with the dust mass flux of 7.8 and 26.6 Tg/year, respectively. The maximum mass flux of the North African dust mainly occurs in 0&#8211;3 km (3.9 Tg/year), while the Middle East within 6&#8211;9 km (12.3 Tg/year). The dust outflow occurs at East side (&#8211;17.89 Tg/year) and South side (&#8211;11.22 Tg/year) of the TP with a peak value (8.7 Tg/year) in 6&#8211;9 km . Moreover, the dust mass is within the size range of 1.25~5.0

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Spring Dust Mass Flux over the Tibetan Plateau during 2007–19 and Connections with North Atlantic SST Variability

Journal of Climate ◽

10.1175/jcli-d-19-0481.1 ◽

2020 ◽

Vol 33 (22) ◽

pp. 9691-9703

Author(s):

Chao Xu ◽

Yaoming Ma ◽

Jiehua Ma ◽

Chao You ◽

Huijun Wang

Keyword(s):

Tibetan Plateau ◽

North Atlantic ◽

Tarim Basin ◽

Mass Flux ◽

The Tibetan Plateau ◽

Indian Peninsula ◽

The North ◽

Dust Mass ◽

The North Atlantic ◽

Spring Dust

AbstractDust is the major aerosol type over the Tibetan Plateau (TP), and the TP plays an important role in forming the spring dust belt across the Northern Hemisphere in the upper troposphere. Estimated spring dust mass flux (DMF) showed a significant declining trend over the TP during 2007–19. The total spring DMF across the TP (TDMFTP) was mainly affected by DMFs over the Tarim Basin, while the spring DMF across the TP in the midtroposphere was also connected with DMFs over the northwest Indian Peninsula and central Asia. Interannual variability of spring TDMFTP was strongly correlated with the North Atlantic winter sea surface temperature (SST) tripole. A cold preceding winter induced by the North Atlantic winter SST tripole over midlatitude Eurasia promotes dust activities in the subsequent spring. The North Atlantic winter SST tripole anomalies persist into the subsequent spring and induce a corresponding atmosphere response. Enhanced atmospheric baroclinicity develops over northwest China and the northern Indian Peninsula during spring, which is attributed to surface thermal forcing induced by the positive winter SST tripole phase. A strong positive North Atlantic winter SST tripole anomaly strengthens the upper-level westerly jets, enhancing airflow toward the TP midtroposphere; together, these circulation patterns cause anomalous cyclonic conditions in the lower troposphere, especially over the Tarim Basin, via the eastward propagation of a Rossby wave train. These atmospheric circulation conditions are likely to increase the frequency of dust occurrence and promote the transport of dust onto the TP.

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Modulation of Saharan dust export by the North African dipole

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-26689-2014 ◽

2014 ◽

Vol 14 (19) ◽

pp. 26689-26719 ◽

Cited By ~ 3

Author(s):

S. Rodríguez ◽

E. Cuevas ◽

J. M. Prospero ◽

A. Alastuey ◽

X. Querol ◽

...

Keyword(s):

North Africa ◽

North Atlantic ◽

Radiative Forcing ◽

Saharan Dust ◽

Dust Particles ◽

North African ◽

Inter Tropical Convergence Zone ◽

The North ◽

The Tropics

Abstract. Desert dust aerosols influence air quality and climate on a global scale, including radiative forcing, cloud properties and carbon dioxide modulation through ocean fertilisation. North Africa is the largest and most active dust source worldwide; however, the mechanisms modulating year-to-year variability in Saharan dust export in summer remains unclear. In this season, enhanced dust mobilization in the hyper-arid Sahara results in maximum dust impacts throughout the North Atlantic. The objective of this study is to identify the relationship between the long term interannual variability in Saharan dust export in summer and large scale meteorology in western North Africa. We address this issue by analysing ~25 yr (1987–2012) dust concentrations at the high altitude Izaña observatory (2373 m a.s.l.) in Tenerife Island, satellite and meteorological reanalysis data. Because in summer Saharan dust export occurs at altitudes 1–5 km, we paid special attention to the summer meteorological scenario in the 700 hPa standard level, characterised by a high over the subtropical Sahara and lower geopotential heights over the tropics; we measured the intensity of this low-high dipole like pattern in terms of the North AFrican Dipole Index (NAFDI): the difference of the 700 hPa geopotential heights anomalies averaged over central Morocco (subtropic) and over Bamako region (tropic). The correlations we found between the 1987–2012 NAFDI with dust at Izaña, satellite dust observations and meteorological re-analysis data, indicates that increase in the NAFDI (i) results in higher wind speeds at the north of the Inter-Tropical Convergence Zone which enhances dust export over the subtropical North Atlantic, (ii) influences on the size distribution of exported dust particles, increasing the load of coarse dust and (iii) are associated with higher rainfall over tropical North Africa and the Sahel. Because of the North African dipole modulation, inter-annual variability in Saharan dust export is correlated with monsoon rainfall in the Sahel. High values of the NAFDI enhance dust export at subtropical latitudes. Our results suggest that long term variability in Saharan dust export may be influenced by global oscillations in the climate of the tropics and subtropics and that this may have influenced dust transport pathways in the last decades.

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The North African “Extremistan” of the Islamic State Caliphate

International conference KNOWLEDGE-BASED ORGANIZATION ◽

10.1515/kbo-2016-0002 ◽

2016 ◽

Vol 22 (1) ◽

pp. 10-13

Author(s):

Adrian Cosmin Basarabă ◽

Maria-Mihaela Nistor

Keyword(s):

Middle East ◽

Real Estate ◽

North Africa ◽

Islamic State ◽

North African ◽

Boko Haram ◽

Ongoing Process ◽

The North ◽

Terrorist Groups ◽

Cellular Matrices

Abstract This article aims at presenting ISIS expansion in North Africa in the first quarter of 2016, with its subsequent implication in the wider framework of Jihadist proliferation worldwide. It can be argued that, while losing real estate in the Middle East, ISIS has started a permanent search for extra-cellular matrices or an ongoing process of de- and reterritorialization. The allegiance and support pledged by other African-based terrorist groups or organizations such as Boko Haram, al-I’tisam of the Koran and Sunnah in Sudan, al-Huda Battalion in Maghreb of Islam, The Soldiers of the Caliphate, al-Ghurabaa, Djamaat Houmat ad-Da’wa as-Salafiya and al-Ansar Battalion in Algeria, Islamic Youth Shura Council, Islamic State Libya (Darnah), in Libya, Jamaat Ansar Bait al-Maqdis, Jund al-Khilafah and Mujahideen Shura Council in the Environs of Jerusalem in Egypt, Okba Ibn Nafaa Battalion, Mujahideen of Tunisia of Kairouan and Jund al-Khilafah in Tunisia and al-Shabaab Jubba Region Cell Bashir Abu Numan in Somalia is an alarming hypothesis of Jihadism reaching “the threshold of inevitability”- syntagm existent in the network theories of David Singh Grewal- turning a whole region, continent of even world into what Nassim Nicholas Taleb would call Extremistan.

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Impact of dust size parameterizations on aerosol burden and radiative forcing in RegCM4

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-769-2017 ◽

2017 ◽

Vol 17 (2) ◽

pp. 769-791 ◽

Cited By ~ 7

Author(s):

Athanasios Tsikerdekis ◽

Prodromos Zanis ◽

Allison L. Steiner ◽

Fabien Solmon ◽

Vassilis Amiridis ◽

...

Keyword(s):

Optical Depth ◽

Radiative Forcing ◽

Climate Model ◽

Size Range ◽

Regional Climate ◽

Deposition Velocity ◽

Research Unit ◽

Dust Particles ◽

Total Size ◽

The Mediterranean

Abstract. We investigate the sensitivity of aerosol representation in the regional climate model RegCM4 for two dust parameterizations for the period 2007–2014 over the Sahara and the Mediterranean. We apply two discretization methods of the dust size distribution keeping the total mass constant: (1) the default RegCM4 4-bin approach, where the size range of each bin is calculated using an equal, logarithmic separation of the total size range of dust, using the diameter of dust particles, and (2) a newly implemented 12-bin approach with each bin defined according to an isogradient method where the size ranges are dependent on the dry deposition velocity of dust particles. Increasing the number of transported dust size bins theoretically improves the representation of the physical properties of dust particles within the same size bin. Thus, more size bins improve the simulation of atmospheric processes. The radiative effects of dust over the area are discussed and evaluated with the CALIPSO dust optical depth (DOD). This study is among the first studies evaluating the vertical profile of simulated dust with a pure dust product. Reanalysis winds from ERA-Interim and the total precipitation flux from the Climate Research Unit (CRU) observational gridded database are used to evaluate and explain the discrepancies between model and observations. The new dust binning approach increases the dust column burden by 4 and 3 % for fine and coarse particles, respectively, which increases DOD by 10 % over the desert and the Mediterranean. Consequently, negative shortwave radiative forcing (RF) is enhanced by more than 10 % at the top of the atmosphere and by 1 to 5 % on the surface. Positive longwave RF locally increases by more than 0.1 W m−2 in a large portion of the Sahara, the northern part of the Arabian Peninsula and the Middle East. The four-bin isolog method is to some extent numerically efficient, nevertheless our work highlights that the simplified representation of the four-bin approach produces less dust optical depth and RF, a fact that should be taken into account by future studies of the same region.

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Why Is There an Early Spring Cooling Shift Downstream of the Tibetan Plateau?

Journal of Climate ◽

10.1175/jcli3568.1 ◽

2005 ◽

Vol 18 (22) ◽

pp. 4660-4668 ◽

Cited By ~ 80

Author(s):

Jian Li ◽

Rucong Yu ◽

Tianjun Zhou ◽

Bin Wang

Keyword(s):

Tibetan Plateau ◽

North Africa ◽

North Atlantic ◽

Radiative Forcing ◽

Temperature Shift ◽

Early Spring ◽

Climate Feedback ◽

The Tibetan Plateau ◽

The North ◽

The North Atlantic

Abstract The temperature shift over the eastern flank of the Tibetan Plateau is examined using the last 50 yr of Chinese surface station observations. It was found that a strong cooling shift occurs in early spring (March and April) and late summer (July, August, and September) in contrast to the warming shift in other seasons. The cause of the March–April (MA) cooling is investigated in this study. The MA cooling shift on the lee side of the Tibetan Plateau is found to be not a local phenomenon, but rather it is associated with an eastward extension of a cooling signal originating from North Africa that is related to the North Atlantic Oscillation (NAO) in the previous winter. The midtropospheric westerlies over the North Atlantic and North Africa tend to intensify during positive NAO phases. The enhanced westerlies, after passing over the Tibetan Plateau, result in strengthened ascending motion against the lee side of the plateau, which favors the formation of midlevel stratiform clouds. The increased amount of stratus clouds induces a negative net cloud–radiative forcing, which thereby cools the surface air and triggers a positive cloud–temperature feedback. In this way, the cooling signal from the upstream could “jump” over the Tibetan Plateau and leave a footprint on its lee side. The continental stratiform cloud–climate feedback plays a significant role in the amplification of the cooling shift downstream of the Tibetan Plateau.

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The Oxford Handbook of Contemporary Middle Eastern and North African History

10.1093/oxfordhb/9780199672530.001.0001 ◽

2015 ◽

Keyword(s):

Middle East ◽

World War I ◽

Middle Eastern ◽

World Politics ◽

African History ◽

North African ◽

The North ◽

East Region ◽

Historical Developments ◽

Middle East Region

It is in moments of great upheaval that societies may best be studied. Today, The North Africa and the Middle East region (MENA) finds itself in the most alarming state since World War I. The Oxford Handbook of Contemporary Middle East and North African History is a timely intervention to interrogate the region’s internal dynamics and take stock of its place in world politics. It illuminates afresh dominant historical currents as well as counter-currents that previous accounts have not given their due attention or have failed to notice. Broadly chronological, this volume combines thematic and country-based, multi-disciplinary analysis in order to reconsider half a century of scholarship and to critically examine the defining processes and structures of historical developments from Morocco to Iran and from Turkey to Yemen over the past two centuries.

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Apparent dust size discrepancy in aerosol reanalysis in north African dust after long-range transport

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-10047-2020 ◽

2020 ◽

Vol 20 (16) ◽

pp. 10047-10062 ◽

Cited By ~ 1

Author(s):

Samantha J. Kramer ◽

Claudia Alvarez ◽

Anne E. Barkley ◽

Peter R. Colarco ◽

Lillian Custals ◽

...

Keyword(s):

Aerosol Optical Depth ◽

Long Range ◽

Optical Depth ◽

Dust Particles ◽

Long Range Transport ◽

North African ◽

African Dust ◽

Range Transport ◽

Dust Mass ◽

Mass Concentrations

Abstract. North African dust reaches the southeastern United States every summer. Size-resolved dust mass measurements taken in Miami, Florida, indicate that more than one-half of the surface dust mass concentrations reside in particles with geometric diameters less than 2.1 µm, while vertical profiles of micropulse lidar depolarization ratios show dust reaching above 4 km during pronounced events. These observations are compared to the representation of dust in the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) aerosol reanalysis and closely related Goddard Earth Observing System model version 5 (GEOS-5) Forward Processing (FP) aerosol product, both of which assimilate satellite-derived aerosol optical depths using a similar protocol and inputs. These capture the day-to-day variability in aerosol optical depth well, in a comparison to an independent sun-photometer-derived aerosol optical depth dataset. Most of the modeled dust mass resides in diameters between 2 and 6 µm, in contrast to the measurements. Model-specified mass extinction efficiencies equate light extinction with approximately 3 times as much aerosol mass, in this size range, compared to the measured dust sizes. GEOS-5 FP surface-layer sea salt mass concentrations greatly exceed observed values, despite realistic winds and relative humidities. In combination, these observations help explain why, despite realistic total aerosol optical depths, (1) free-tropospheric model volume extinction coefficients are lower than those retrieved from the micro-pulse lidar, suggesting too-low model dust loadings in the free troposphere, and (2) model dust mass concentrations near the surface can be higher than those measured. The modeled vertical distribution of dust, when captured, is reasonable. Large, aspherical particles exceeding the modeled dust sizes are also occasionally present, but dust particles with diameters exceeding 10 µm contribute little to the measured total dust mass concentrations after such long-range transport. Remaining uncertainties warrant a further integrated assessment to confirm this study's interpretations.

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Dust-dominated coarse particles as a medium for rapid secondary organic and inorganic aerosol formation in highly polluted air

10.5194/egusphere-egu21-13816 ◽

2021 ◽

Author(s):

Ye Kuang ◽

Wanyun Xu ◽

Linlin Liang ◽

Yao He ◽

Hongbin Cheng ◽

...

Keyword(s):

Radiative Forcing ◽

North China Plain ◽

Physical Property ◽

Ice Nucleation ◽

Submicron Particles ◽

Dust Particles ◽

Aerosol Formation ◽

The North ◽

Inorganic Aerosol ◽

Haze Formation

Secondary aerosol (SA) frequently drives severe haze formation on the North China Plain. However, previous studies mostly focused on submicron SA formation, thus our understanding of SA formation on supermicron particles remains poor. In this study, PM2.5 chemical composition and PM10 number size distribution measurements revealed that the SA formation occurred in very distinct size ranges. In particular, SA formation on dust-dominated supermicron particles was surprisingly high and increased with relative humidity (RH). SA formed on supermicron aerosols reached comparable levels with that on submicron particles during evolutionary stages of haze episodes. These results suggested that dust particles served as a medium for rapid secondary organic and inorganic aerosol formation under favorable photochemical and RH conditions in a highly polluted environment. Further analysis indicated that SA formation pathways differed among distinct size ranges. Overall, our study highlights the importance of dust in SA formation during non-dust storm periods and the urgent need to perform size-resolved aerosol chemical and physical property measurements in future SA formation investigations that are extended to the coarse mode because the large amount of SA formed thereon might have significant impacts on ice nucleation, radiative forcing, and human health.

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