Intense Dust Event Research Articles

The diurnal variation of dust and water ice aerosol optical depth at Jezero crater observed by MEDA/TIRS over a full Martian year

The Thermal InfraRed Sensor (TIRS) on the Perseverance rover has provided nearly two full Mars years of systematic monitoring of the total aerosol optical depth above Jezero Crater. These observations span a wide range of timescales, capturing seasonal patterns, diurnal variations, and minute-to-minute fluctuations in aerosol loading. By combining TIRS retrievals with orbital observations, the relative contributions of dust and water ice aerosols can be estimated, revealing their different seasonal and diurnal behaviors. The TIRS record shows distinct periods of dust storm activity, including strong regional storms during the perihelion season as well as short-lived but intense dust events outside the typical dust storm season. Water ice clouds exhibit pronounced seasonal and diurnal variability, with peak activity occurring during the aphelion season but with a presence throughout the year. The diurnal variation of clouds differs significantly between the aphelion and perihelion seasons, with clouds persisting throughout the night during the aphelion season, while largely absent outside of specific periods after sunrise and sunset during the perihelion season. These results provide new insights into the complex behavior of aerosols at Jezero Crater and their connections to atmospheric dynamics and the Martian dust and water cycles.

Fractional solubility of iron in mineral dust aerosols over coastal Namibia: a link to marine biogenic emissions?

Abstract. This paper presents the first investigation of the solubility of iron in mineral dust aerosols collected at the Henties Bay Aerosol Observatory (HBAO), in Namibia, from April to December 2017. During the study period, 10 intense dust events occurred. Elemental iron reached peak concentrations as high as 1.5 µg m−3, significantly higher than background levels. These events are attributed to wind erosion of natural soils from the surrounding gravel plains of the Namib desert. The composition of the sampled dust is found to be overall similar to that of aerosols from northern Africa but is characterized by persistent and high concentrations of fluorine which are attributed to local fugitive dust. The fractional solubility of Fe (%SFe) for both the identified dust episodes and background conditions ranged between 1.3 % and 20 % and averaged at 7.9 % (±4.1 %) and 6.8 (±3.3 %), respectively. Even under background conditions, the %SFe was correlated with that of Al and Si. The solubility was lower between June and August and increased from September onwards during the austral spring. The relation to measured concentrations of particulate MSA (methane sulfonic acid), solar irradiance, and wind speed suggests a possible two-way interaction whereby marine biogenic emissions from the coastal Benguela upwelling to the atmosphere would increase the solubility of iron-bearing dust according to the photo-reduction processes. This first investigation points to the western coast of southern Africa as a complex environment with multiple processes and active exchanges between the atmosphere and the Atlantic Ocean, requiring further research.

A Study of a Severe Spring Dust Event in 2021 over East Asia with WRF-Chem and Multiple Platforms of Observations

In this study, we investigate the most severe East Asian dust storm in the past decade that occurred on 14–16 March 2021 based on the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) and a variety of site measurements and satellite retrievals. The dust emissions from the Gobi Desert, especially over Mongolia on March 14, are the dominant sources of this intense dust event. The maximal hourly accumulated dust emissions over Mongolian and Chinese areas reached 1490.18 kt at 07:00 UTC on 14 March and 821.70 kt at 2:00 UTC on 15 March, respectively. During this dust event, the accumulated dust emissions in coarse modes (i.e., bin 4 and bin 5) account for 64.1% of the total dust emission mass, and the accumulated dust emissions in fine modes (i.e., bin 1) are the least, accounting for 7.6% of the total dust emission mass. Because the coarse mode bins of dust dominate the emissions, the downwind transported coarse mode particles can affect the North China Plain, while the fine particles can only affect the desert source and its surrounding regions such as the Gansu and Ningxia provinces. Due to the dust emissions and the dust transport path, the high AOD areas are located in the Gobi Desert and Northwest China and the vertical spatial distributions of aerosol extinction coefficients have the same characteristics. We also found the model drawback of overestimating simulated wind speeds, which leads to the overestimations of dust emissions and concentrations, indicating the urgency of improving the simulated wind field.

Effect of aerosol types from various sources at an urban location on spectral curvature of scattering and absorption coefficients

This study analyzes the spectral characteristics of in situ measured aerosol properties, namely scattering, absorption and single scattering albedo (SSA), explicitly examining the curvature characteristics of their wavelength dependence. Measurements were performed at an urban background site in Athens, Greece, during December 2017 and March 2018 characterized by contrasting aerosol sources and types, i.e. residential wood burning (RWB) and desert dust, respectively, which modulate the urban conditions, that are typically dominated by fossil-fuel combustion. Aerosol types were classified via the Scattering Ångström Exponent (SAE) vs. Absorption Ångström Exponent (AAE) matrix, with the black carbon (BC)-dominated type displaying the highest fraction (~40%) in both periods. The spectral optical properties were examined for each aerosol type and month, revealing notable differences, which are closely linked to the contrasting emission sources, atmospheric dynamics and mixing processes. BC from fossil-fuel emissions and regional background aerosols mostly presented similar characteristics in both months. Emphasis was given on the spectral curvature effect, since the different aerosol types display notable changes in the spectral dependence of scattering and absorption in logarithmic coordinates. The enhanced presence of brown carbon resulted in negative curvature for scattering (concave curves) and highly positive for absorption (convex curves), while the presence of BC was mostly translated in a better fit of the Ångström formula and small curvature effects. Intense dust events resulted in positive curvature for absorption and mostly negative for scattering. A scatterplot between the wavelength dependence of SSA and the scattering curvature may further differentiate key aerosol types i.e. BC, brown carbon and dust. This study highlights the curvature effects of the scattering, absorption and SSA, which have not been adequately addressed yet. The approach provides new insights in the differentiation of source-related aerosol types, although more analysis is needed to examine if findings are reproduced in other environments.

Seasonal Variations and Long-term Trend of Mineral Dust Aerosols over the Taiwan Region

Atmospheric dust aerosols are known to affect the air quality and public health as well as climate and weather systems. An increasing number of modeling studies have related ice nucleation with the number concentrations of dust particles with a diameter larger than 500 nm (ND,d>500nm). In this paper, the seasonal variation, vertical properties, and long-term trend of ND,d>500nm over the Taiwan region are analyzed, using simulations from a global chemical transport model with size-resolved particle microphysics. Over Taiwan, ND,d>500nm shows a bimodal seasonal variation distribution with two peaks in spring (March–May) and fall-early winter (October–December). In the different seasons, ND,d>500nm varies by about one order of magnitude from summer to spring (0.06–1.23 cm–3 in the boundary layer, 0.03–0.55 cm–3 in the middle and lower troposphere, and 0.006–0.03 cm–3 in the upper level). Vertically, ND,d>500nm profiles show the unimodal distribution, with the highest ND,d>500nm appears at ~1 km and decreasing with altitude. From surface to high levels, the frequencies of intense dust events decrease in fall (September–November) and increase in summer months (June–August). The long-term model results suggest a decreasing trend of the strong dust event frequencies and annual mean ND,d>500nm over Taiwan in the last two decades. From 1999 to 2018, the number of strong dust event days and ND,d>500nm decreased by 40–43% and 37–54%, respectively, under 4 km, and the decline is weaker at higher altitudes. The analysis suggests that these decrease trends are caused by the declining Asian dust emissions.

Tropospheric Dust and Associated Atmospheric Circulations over the Mediterranean Region with Focus on Romania’s Territory

The aim of this study is to assess the distribution of dust over the Mediterranean region, with a special focus on the territory of Romania. Two parameters are analyzed—Dust Load (DL) and Aerosol Optical Depth (AOD), the data is obtained from the dust forecast model BSC-DREAM8b v2.0, for the period between December 2015 and February 2019. The main geographical features of dust occurrence in the Mediterranean region are presented at the monthly and annual scale. The results show that, for Romania, the dust load is high from February to June, when it reaches its annual maximum. The atmospheric circulation inducing intense dust events over Romania have also been assessed using an objective classification method. A key element for the dust transport from the Sahara toward South-Eastern Europe is represented by the development of a deep cyclone South of Italy, following thereafter a North-East path towards the Balkan peninsula. The results at the regional scale are analyzed in connection with the aerosol optical properties at the local scale (e.g., aerosol optical depth at 440 nm, Absorption Ångström Exponent and Scattering Ångström Exponent at 440 nm and 675 nm, respectively) retrieved from the Aerosol Robotic Network (AERONET-NASA) for Romania, using data from ACTRIS-RO monitoring sites from Iași, Cluj–Napoca, and Bucharest. The differences between the forecast model and the observational data are also explored. Our results also show that the contribution of the natural mineral dust to air pollution in Romania is small, representing not more than 10% of all kinds of aerosols detected over the observation points from the ACTRIS-RO network.

Impact of Saharan dust episodes on preterm births in Guadeloupe (French West Indies)

ObjectivesLarge amounts of mineral dust are transported from their African sources in the Saharan-Sahel region to the Caribbean Sea, generating peak exposures to particulate matter ≤10 µm (PM10). This study...

Aerosol vertical distribution, optical properties and dust transport in the Western Mediterranean basin (case study: Summer, 2012)

In this paper, we have analyzed an intense dust event at the end of June 2012 crossing the western Mediterranean basin and reaching southern Europe. The geographical distribution of the dust event, its origins, microphysical and optical properties as well as its vertical distribution have been investigated using satellite data, AERONET sun photometer retrievals and lidar soundings. On average for the summer 2012, all satellite AOD derived from MODIS, MISR, SEVIRI and OMI are consistent, while OMI tends to overestimate the AOD. During late June and early July 2012, a major dust outbreak occurred over the North Atlantic and has moved toward East to cross the Mediterranean up to Northern Italy. Satellite and Sun photometer AOD time series have captured this event. Dust event is clearly identified in the AERONET observations using a classification of the coarse mode AOD and the total AOD. The size distributions of this event observed at the different AERONET stations from Northern Africa to Europe don't show a significant change due to sedimentation and the optical properties correspond to an aged dust event, as confirmed by the backtrajectories. The vertical distribution of the aerosol extinction coefficient reveals a complex structure with a large dust layer between 1.8 and 4.8 km AMSL having a rather constant extinction coefficient between 0.12 and 0.15 km−1.

Aerosol and Meteorological Parameters Associated with the Intense Dust Event of 15 April 2015 over Beijing, China

The northeastern parts of China, including Beijing city, the capital of China, were hit by an intense dust storm on 15 April 2015. The present paper discusses aerosol and meteorological parameters associated with this dust storm event. The back trajectory clearly shows that the dust originated from Inner Mongolia, the border of China, and Mongolia regions. Pronounced changes in aerosol and meteorological parameters along the dust track were observed. High aerosol optical depth (AOD) with low Ångström exponent (AE) are characteristics of coarse-mode dominated dust particles in the wavelength range 440–870 nm during the dusty day. During dust storm, dominance of coarse aerosol concentrations is observed in the aerosol size distribution (ASD). The single scattering albedo (SSA) retrieved from AERONET station shows increase with higher wavelength on the dusty day, and is found to be higher compared to the days prior to and after the dust event, supported with high values of the real part and decrease in the imaginary part of the refractive index (RI). With regard to meteorological parameters, during the dusty day, CO volume mixing ratio (COVMR) is observed to decrease, from the surface up to mid-altitude, compared with the non-dusty days due to strong winds. O3 volume mixing ratio (O3VMR) enhances at the increasing altitudes (at the low-pressure levels), and decreases near the surface at the pressure levels 500–925 hPa during the dust event, compared with the non-dusty periods. An increase in the H2O mass mixing ratio (H2OMMR) is observed during dusty periods at the higher altitudes equivalent to the pressure levels 500 and 700 hPa. The mid-altitude relative humidity (RH) is observed to decrease at the pressure levels 700 and 925 hPa during sand storm days. With the onset of the dust storm event, the RH reduces at the surface level.

Multi-Satellite Observation of an Intense Dust Event over Southwestern China

This study presents the results of a large-scale examination into a dust event that took place over southwestern China, an area that has received relatively little attention in the literature. The sources, transport path, and vertical distribution, as well as formation process of an intense dust storm event that took place over the Sichuan Basin from March 9 to March 14, 2013, were investigated using combined multiple satellite observations and meteorological data. Widespread dust plumes appeared over the Taklimakan Desert, Gobi Desert, and Loess Plateau on March 9. Different from the usual dust storms, the dust plumes did not move downstream directly but settled over the Loess Plateau and Sichuan Basin for several days. Persistent southwestern winds prevailed over eastern China during this period, and could prevent the dust storms from moving directly downstream. Our results suggest that the dust plumes over southwestern China mainly originated from the Gobi Desert. Despite extensive dust plumes over all the Sichuan Basin, PM10 increased sharply to more than 1200 μg/m^3 in the western part of the basin, with only a slight increase in the eastern part. When there was a sharp increase in coarse particles in Chengdu on March 11 and 14, northeasterly winds appeared over northern China. The elevated dust can be blown to the eastern slope of the Tibetan Plateau and deposited in the western Sichuan Basin. However, such intense dust events are not common in southwestern China. In addition, floating dust may not be observed near the surface, but can have an important impact on regional aerosol loading and properties.

Analysis of Impact Factors on the Variation of PM10 Concentration in Seoul, Korea

To identify the primary factor affected the decreased PM 10 concentration in Seoul which is the capital city of Korea, wind speed and emissions in 2003 and 2004 were analyzed. The level of air pollution is intense in Seoul and continually increased since the late 1990s. However the concentration of PM 10 has been greatly declined recently. In particular, the concentration of PM 10 decreased 14% in 2003 and 2004 excluding the Asian dust periods. It is suggested that the major factors for the decrease are differences in wind speed between the two years and the period of constant breeze. In 2003, intense Asian dust events happened frequently and it increased the concentration of total PM 10 . The intense dust events were influence by the speed and duration of the wind. It is considered that the meteorological condition was the primary drive for the change of the concentration of PM 10 . The decreased emissions seem to be the additional factor for the change in the concentration of PM 10 .

Study on an intense dust storm over Greece

Springtime constitutes the most favorable period for Sahara dust outbreaks and transport over Eastern Mediterranean. This study investigates the aerosol properties during April 2005 using remote-sensing and ground-based measurements. Three dust events with high aerosol optical depth (AOD) values have been observed during the measuring period, with duration of two days, i.e. 11–12, 16–17 and 25–26 April 2005. In this paper we mainly focus on the intense dust event of 16–17 April 2005, when a thick dust layer transported from Libya affected the whole Greek territory. Very high AOD values obtained from Aqua-MODIS sensor were observed over Greece (mean 2.42 ± 1.25) on 17 April, while the respective mean April value was 0.31 ± 0.09. The AOD at 550 nm (AOD 550) values over Crete were even larger, reaching ∼4.0. As a consequence, the PM 10 concentrations over Athens dramatically increased reaching up to 200 μg m −3. On the other hand, the fine-mode fraction values obtained from Terra-MODIS showed a substantial decrease in the whole Greek area on 17 April with values below 0.2 in the Southern regions. The intense dust layer showed a complex behavior concerning its spatial and temporal evolution and allowed us to study the changes in the optical properties of the desert dust particles along their transport routes due to the mixing processes with other aerosol types. The results from different measurements (ground-based and remote-sensing) did not contradict each other and, therefore, are adequate for monitoring of dust load over the Eastern Mediterranean.

Influence of Long-Range Transport Dust Particles on Local Air Quality: A Case Study on Asian Dust Episodes in Taipei during the Spring of 2002

In the spring of 2002, an intensive field measurement campaign was conducted to investigate the impact of Asian dust transport on local air quality in Taipei, Taiwan. The mass concentration, size distribution and chemical composition of the atmospheric aerosols were measured. Air quality data collected by the Taiwan EPA during this period were also analyzed. It was found that the content of crustal elements in aerosols could drastically increase on the arrival of air masses transported from the desert areas in Northwestern China and Mongolia. Time series analysis of aerosol measurements, air quality data, and meteorological conditions identified six Asian dust transport episodes occurring in the spring of 2002. In order to apportion the ambient aerosol burden between local and long-range sources, nitrogen oxides (NO(subscript x)) was chosen as a local pollution tracer and a simplified algorithm based on the NO(subscript x) and PM10 correlation was proposed. It was estimated that long-range transported aerosols contributed as much as 87% to the PM10 in Taipei on Feb. 11, the most intense dust event in 2002. A weak event that occurred on Mar. 23 contributed 35% to the PM10. Our results indicate that the air quality impact due to Asian transport dust is still important even during weak dust events.

Chemical and optical characterization of aerosols measured in spring 2002 at the ACE‐Asia supersite, Zhenbeitai, China

In April 2002, aerosol characteristics have been recorded at Zhenbeitai (ZBT) near the city of Yulin (38°17′N, 109°43′E, Shaanxi province, China). One year earlier, ZBT had been one of the continental supersites of the ACE‐Asia international experiment. In spring, this site, located on the southwestern fringe of the Mu Us desert, is at the crossing of the pathways followed by dust originating from the main Chinese dust sources. During the experiment a customized aerosol sampler has been used. It had been specially designed to ensure the best possible sampling isokineticity for all instruments and to minimize coarse particle losses. Its cutoff size (D50) has been computed to be 9 μm. For particles smaller than this size (PM9), mass concentrations, number concentrations, size distributions, elemental composition, and scattering properties were measured at ground level. Vertically integrated characteristics such as aerosol optical thickness (AOT), or single scattering albedo (ϖ0), were also determined by the means of a Sun‐tracking photometer. During the measurement period, several dust events, one of them a major dust storm when PM9 mass concentrations became as high as 4650 μg/m3, were observed. At this time the aerosol scattering coefficient reached 2800 Mm−1. These dust events were separated by periods when optical properties were altered, or even dominated, by anthropogenic aerosol of local origin. For these periods, PM9 was significantly less (always below 100 μg/m3) than during dust events, mass concentration in black carbon (BC) was between 0.9 and 6.7 μg/m3, and the aerosol scattering coefficient between 7 and 800 Mm−1. No difference in elemental composition could be detected between the various dust episodes. Measured Fe/Al (0.63 ± 0.04) and Mg/Al (0.32 ± 0.03) ratios are consistent with an aerosol source located in the “northwestern high desert sources.” This result is also supported by the air mass back‐trajectories coming from a west or northwest direction and by the fact that dust layers had generally already acquired a significant vertical extension (∼1500 m) when reaching the measurement site. This transported dust had already incorporated an anthropogenic carbonaceous component upon reaching the measurement site. The size distribution of this transported mixture is relatively constant and is characterized by the presence of a particle population with a number mean diameter between 1 and 2 μm. The mass scattering efficiency of this aerosol is 1.05 ± 0.13 m2/g, relative to PM9, and its Angström exponent is close to 0.19. The single scattering albedo determined by data inversion of Sun photometer measurements is found to increase from 0.89 at 441 nm to 0.95 at 873 nm. These relatively large ϖ0 values indicate that, though mixing of mineral dust and anthropogenic aerosols is the rule rather than the exception at ZBT, the aerosol is still not very absorbent during intense dust events. In consequence, the dust optical characteristics measured at ZBT during dust storms are probably representative of the ones of pure dust emitted from the “northwestern high desert” sources.

Chemical composition of mineral dust aerosol during the Saharan Dust Experiment (SHADE) airborne campaign in the Cape Verde region, September 2000

During the Saharan Dust Experiment (SHADE) in September 2000, we collected filter samples on board the Met Office C‐130 aircraft. The main study area was over the Atlantic Ocean between Sal Island and Senegal. Dust was encountered in the altitude range from 0.5–1 to 4–4.5 km. Sublayers with different particle size distributions and different source areas can be distinguished within the main dust plume. Diminution of O3 in anticorrelation with the dust layer suggests removal of O3 by dust particles. Dust loadings containing up to 54 μg m−3 Al (submicron plus supermicron fraction) were measured during particularly intense dust events. Mixing of dust with anthropogenic aerosols, mainly NH4HSO4, was observed in the fine fraction. It was associated with air masses that had originated over Europe and then traveled over North Africa. The ratio of nitrate to non‐sea‐salt sulfate was around 0.3. This argues against any significant influence of biomass burning emissions, which have much higher nitrate. However, we also encountered aged fossil fuel pollution plumes, likely from North America. The geochemical signature of mineral dust was consistent with previous results in the area. Si, Fe, and Ti were not enriched with respect to the soil composition, while other elements, such as Ca and S, were. Ca is prevalently present as calcite in African soils, but it is also found as calcium sulfate in the atmosphere.

Two‐year simulations of seasonal and interannual changes of the Saharan dust emissions

Using a soil‐derived dust emission scheme, the annual and monthly dust emissions in the western “dry” Sahara have been estimated for 1991 and 1992, respectively to 665 Mt and 586 Mt. Based on these simulations, an investigation of the seasonal and annual changes in dust emissions has been performed. The monthly dust emissions vary from 163 Mt in March 1991 to 8 Mt in December 1992. These seasonal variations are related to changes in the location and area of the source‐regions and in the frequency of dust events. On the opposite, the interannual variations of the dust emissions are due to changes in the occurrence of the most intense dust events.