Numerical simulation and synoptic analysis of dust emission and transport in East Asia

This study is concerned with the mechanisms of dust storm development in East Asia and the characteristics of the responsible synoptic systems. Two severe East Asian dust storms which occurred in spring 2002 are analyzed using synoptic and remote sensing data. The relationships between the formation and the movement of the dust storms and the evolution of the synoptic systems are examined. It is shown that a dust storm may develop when a synoptic system moves to the desert area of Northeast Asia with a surface wind speed exceeding 6 m s^− 1. Numerical simulations of the two dust storms are carried out using a dust storm forecasting model. The performance of the model is verified with observations. The dust sources are found to be consistent with the desert regions in Northeast Asia, but cover a somewhat larger area than the observations suggest. Finally, we present a conceptual model of dust storm generation and movement in East Asia on the basis of numerical modeling and synoptic analysis.     

Aeolian dust experiment on climate impact: An overview of Japan–China joint project ADEC

The Aeolian Dust Experiment on Climate Impact (ADEC) was initiated in April 2000 as a joint five-year Japan–China project. The goal was to understand the impact of aeolian dust on climate via radiative forcing (RF). Field experiments and numerical simulations were conducted from the source regions in northwestern China to the downwind region in Japan in order to understand wind erosion processes temporal and spatial distribution of dust during their long-range transportation chemical, physical, and optical properties of dust and the direct effect of radiative forcing due to dust. For this, three intensive observation periods (IOP) were conducted from April 2002 to April 2004.The in situ and network observation results are summarized as follows: (1) In situ observations of the wind erosion process revealed that the vertical profile of moving sand has a clear size dependency with height and saltation flux and that threshold wind velocity is dependent on soil moisture. Results also demonstrated that saltation flux is strongly dependent on the parent soil size distribution of the desert surface. (2) Both lidar observations and model simulations revealed a multiple dust layer in East Asia. A numerical simulation of a chemical transport model, CFORS, illustrated the elevated dust layer from the Taklimakan Desert and the lower dust layer from the Gobi Desert. The global-scale dust model, MASINGAR, also simulated the dust layer in the middle to upper free troposphere in East Asia, which originated from North Africa and the Middle East during a dust storm in March 2003. Raman lidar observations at Tsukuba, Japan, found the ice cloud associated with the dust layer at an altitude of 6 to 9 km. Analysis from lidar and the radio-sonde observation suggested that the Asian dust acted as ice nuclei at the ice-saturated region. These results suggest the importance of dust's climate impact via the indirect effect of radiative forcing due to the activation of dust into ice nuclei. (3) Studies on the aerosol concentration indicated that size distributions of aerosols in downwind regions have bimodal peaks. One peak was in the submicron range and the other in the supermicron range. The main soluble components of the supermicron peak were Na⁺, Ca²⁺, NO₃⁻, and Cl⁻. In the downwind region in Japan, the dust, sea salt, and a mixture of the two were found to be dominant in coarse particles in the mixed boundary layer. (4) Observation of the optical properties of dust by sky-radiometer, particle shoot absorption photometer (PSAP), and Nephelometer indicated that unpolluted dust at source region has a weaker absorption than originally believed.A sensitivity experiment of direct RF by dust indicated that single scattering albedo is the most important of the optical properties of dust and that the sensitivity of instantaneous RF in the shortwave region at the top of the atmosphere to the refractive index strongly depends on surface albedo. A global scale dust model, MASINGAR, was used for evaluation of direct RF due to dust. The results indicated the global mean RF at the top and the bottom of the atmosphere were − 0.46 and − 2.13 W m^− 2 with cloud and were almost half of the RF with cloud-free condition.     

Modeling mineral dust emissions from Chinese and Mongolian deserts

The present study investigates the frequency and intensity of mineral dust emissions over the deserts of eastern Asia from 1996 to 2001. Mineral dust emissions are simulated using a physical dust emission scheme over a region extending from 35.5°N to 47°N and from 73°E to 125°E. The input parameters required by the dust emission model are (1) surface features data including aerodynamic roughness length, soil dry size distribution and texture; and (2) meteorological surface data, mainly wind speed, soil moisture and snow cover. The way by which these surface features and meteorological data can be assessed is described and discussed. The influence of soil moisture and snow cover is taken into account and their effects on simulated dust emission are quantified.The simulations reproduce on a daily basis the location and intensity of the severe events of April 1998 and spring 2001 as recorded by the meteorological stations and/or described in various studies. Based on 6 yr of simulations, the main dust source regions are identified and their relative contributions to the total dust emissions are quantified.The seasonal cycle of the dust storms frequency is well reproduced with a maximum in spring. The simulations suggest that it is mainly controlled by the emissions occurring in the Taklimakan desert in latter spring and in summer, and by those occurring in the northern deserts of China in winter. The Taklimakan desert appears to be the most frequent and steady source of dust emissions during the studied period. On the other hand, in the Gobi desert, only a few dust emission events are simulated, but the dust amount emitted during each event is generally very large. In the northern deserts of China, dust emissions are frequent and their intensity is variable.These results show an important annual and inter-annual variability of the emitted dust (between 100 Mt yr^− 1 and 460 Mt yr^− 1), mainly controlled by the occurrence of severe events in the Gobi desert and in the northern deserts of China.     

A numerical study of the contributions of dust source regions to the global dust budget

Contributions of the nine potential dust source regions (North and South Africa, the Arabian Peninsula, Central Asia, eastern and western China, North and South America, and Australia) to the global dust budget are investigated with a global dust transport model. A six-year simulation (1990 to 1995) indicates that the greatest contributor to the global dust budget is found to be North Africa (the Sahara Desert), which accounts for 58% of the total global dust emission and 62% of the total global dust load in the atmosphere. Australian dust dominates the southern hemisphere. The dust emission and atmospheric dust load originating from East Asia (eastern and western China) are estimated to be 214 Tg yr^− 1 and 1.1 Tg, respectively, which are 11% and 6% of the total global dust emission and dust load. Dust from East Asia dominates the atmospheric load over China and Mongolia (about 70%), Korea (60%), Japan (50%), and the North Pacific Ocean (40%). The contribution of dust originating from regions other than East Asia to the dust load over these East Asian countries and the North Pacific Ocean cannot be ignored. The simulated total dust deposition flux on Greenland suggests a possible overestimation of the Saharan dust and an underestimation of the East Asian dust in the Arctic region, which may be a common problem with global dust transport models. Possible reasons for the underestimation of the East Asian dust are discussed.     

An integrated dust storm prediction system suitable for east Asia and its simulation results

An integrated dust storm modeling system is developed for the prediction of dust storms. The system couples a wind erosion scheme, a dust transportation model and the Penn State/UCAR modeling system (MM5) with a geographic information database. The system can be used for the prediction of dust emission rate and dust concentration associated with individual dust storm events. Two severe dust storm events occurred in spring 2002, one on the 19th–22nd of March and the other on the 6th–9th of April. The integrated modeling system is used to simulate the two events. The numerical results are compared with surface weather records and satellite images and good agreement is found between the model results and observation in dust concentration distribution and evolutions. The Gobi Desert in southern Mongolia and the Badain Jaran Desert, Tengger Desert and Hunshandake sandy land in Inner Mongolia (China) are identified to be the dust sources for the two events. The dominant modes of dust particles over western Inner Mongolia and Mongolia are from 2 to 11 μm in size, and 2 to 22 μm over Beijing and its surrounding area. The emission of particles in the 2–11 μm size range is found to be most important for Northeast Asian dust storms.     

An investigation of sand–dust storm events and land surface characteristics in China using NOAA NDVI data

Observations from 560 weather stations in China show that sand–dust storms occur most frequently in April in north China. The region consists of Sub-dry Mid Temperate, Dry Mid Temperate, Sub-dry South Temperate and Dry South Temperate Zones and much of the land surface is desert or semi-desert: it is relatively dry with minimal rainfall and a high annual mean temperature. In most regions of China, the annual mean frequency of sand–dust events decreased sharply between 1980 and 1997 and then increased from 1997 to 2000. Statistical analyses demonstrate that the frequency of sand–dust storms correlates highly with wind speed, which in turn is strongly related to land surface features; on the other hand, a significant correlation between storm events and other atmospheric quantities such as precipitation and temperature was not observed. Accordingly, land surface cover characteristics (vegetation, snowfall and soil texture) may play a significant role in determining the occurrence of sand–dust storms in China. Analysis of Normalized Difference Vegetation Index derived from National Oceanic and Atmospheric Administration and Empirical Orthogonal Function show that since 1995 surface vegetation cover in large areas of Northern China has significantly deteriorated. Moreover, a high correlation is shown to exist among the annual occurrence of sand–dust storms, surface vegetation cover and snowfall. This suggests that the deterioration of surface vegetation cover may strongly influence the occurrence of sand–dust storms in China. Soils with coarse and medium textures are found to be more associated with sand–dust storms than other soils.     

Decreased values of cosmic dust number density estimates in the Solar System

Experiments to investigate the effect of impacts on side-walls of dust detectors such as the present NASA/ESA Galileo/Ulysses instrument are reported. Side walls constitute 27% of the internal area of these instruments, and increase field of view from 140° to 180°. Impact of cosmic dust particles onto Galileo/Ulysses Al side walls was simulated by firing Fe particles, 0.5-5 μm diameter, 2-50 km s⁻¹, onto an Al plate, simulating the targets of Galileo and Ulysses dust instruments. Since side wall impacts affect the rise time of the target ionization signal, the degree to which particle fluxes are overestimated varies with velocity. Side-wall impacts at particle velocities of 2-20 km s⁻¹ yield rise times 10-30% longer than for direct impacts, so that derived impact velocity is reduced by a factor of ∼2. Impacts on side wall at 20-50 km s⁻¹ reduced rise times by a factor of ∼10 relative to direct impact data. This would result in serious overestimates of flux of particles intersecting the dust instrument at velocities of 20-50 km s⁻¹. Taking into account differences in laboratory calibration geometry we obtain the following percentages for previous overestimates of incident particle number density values from the Galileo instrument [Grün et al., 1992. The Galileo dust detector. Space Sci. Rev. 60, 317-340]: 55% for 2 km s⁻¹ impacts, 27% at 10 km s⁻¹ and 400% at 70 km s⁻¹. We predict that individual particle masses are overestimated by ∼10-90% when side-wall impacts occur at 2-20 km s⁻¹, and underestimated by ∼10-¹⁰² at 20-50 km s⁻¹. We predict that wall impacts at 20-50 km s⁻¹ can be identified in Galileo instrument data on account of their unusually short target rise times. The side-wall calibration is used to obtain new revised values [Krüger et al., 2000. A dust cloud of Ganymede maintained by hypervelocity impacts of interplanetary micrometeoroids. Planet. Space Sci. 48, 1457-1471; 2003. Impact-generated dust clouds surrounding the Galilean moons. Icarus 164, 170-187] of the Galilean satellite dust number densities of 9.4×¹⁰⁻⁵, 9.9×¹⁰⁻⁵, 4.1×¹⁰⁻⁵, and 6.8×¹⁰⁻⁵ m⁻³ at 1 satellite radius from Io, Europa, Ganymede, and Callisto, respectively. Additionally, interplanetary particle number densities detected by the Galileo mission are found to be 1.6×¹⁰⁻⁴, 7.9×¹⁰⁻⁴, 3.2×¹⁰⁻⁵, 3.2×¹⁰⁻⁵, and 7.9×¹⁰⁻⁴ m⁻³ at heliocentric distances of 0.7, 1, 2, 3, and 5 AU, respectively. Work by Burchell et al. [1999b. Acceleration of conducting polymer-coated latex particles as projectiles in hypervelocity impact experiments. J. Phys. D: Appl. Phys. 32, 1719-1728] suggests that low-density “fluffy” particles encountered by Ulysses will not significantly affect our results—further calibration would be useful to confirm this.     

Dust influx reconstruction during the last 26,000 years inferred from a sedimentary leaf wax record from the Japan Sea

We obtained the high-resolution record of terrestrial biomarkers (C₂₉ and C₃₁ n-alkanes) for the last 26,000 years from Oki Ridge in the south Japan Sea that enabled us to discuss millennial scale climate changes. Our sampling resolution for the biomarker during the major deglaciation period (10–19.5 cal ka BP) is 300 years and for the elemental analyses (total organic carbon and total nitrogen) is as good as ca 200 years. The estimated mass accumulation rate of these molecules during the last glacial period is substantially higher than during the Holocene. They also exhibited two distinct peaks at 17.6 cal ka BP and 11.4 cal ka BP, which are coincident with Heinrich Event 1 and the latest stage of the Younger Dryas, respectively. The unique oceanographic setting of the Japan Sea tends to preferentially preserve organic material of aeolian origin. The nature of our biomarker record in fact suggests a strong aeolian signal, and hence their flux to the Japan Sea potentially reflects the climate conditions of the dust source regions and transport intensity. Our results are consistent with previously reported monsoon variations based on other proxies that is indicative of a strong linkage between North Atlantic climate and Asian monsoon intensity.     

The climatic and physiographic controls of the eastern Mediterranean over the late Pleistocene climates in the southern Levant and its neighboring deserts

Modern-day synoptic-scale eastern Mediterranean climatology provides a useful context to synthesize the diverse late Pleistocene (60–12 ka) paleohydrologic and paleoenvironmental indicators of past climatic conditions in the Levant and the deserts to its south and east. We first critically evaluate, extract, and summarize paleoenvironmental and paleohydrologic records. Then, we propose a framework of eastern Mediterranean atmospheric circulation features interacting with the morphology and location of the southeast Mediterranean coast. Together they strongly control the spatial distribution of rainfall and wind pattern. This cyclone–physiography interaction enforces the observed rainfall patterns by hampering rainfall generation south and southeast of the latitude of the north Sinai coast, currently at 31°15′.The proposed framework explains the much-increased rains in Lebanon and northern Israel and Jordan as deduced from pollen, rise and maintenance of Lake Lisan, and speleothem formation in areas currently arid and semiarid. The proposed framework also accounts for the southward and eastward transition into semiarid, arid, and hyperarid deserts as expressed in thick loess accumulation at the deserts' margins, dune migration from west to east in the Sinai and the western Negev, and the formation of hyperarid (< 80 mm yr^− 1) gypsic–salic soils in the southern Negev and Sinai. Our climatic synthesis explains the hyperarid condition in the southern Negev, located only 200–250 km south of the much-increased rains in the north, probably reflecting a steeper rainfall gradient than the present-day gradient from the wetter Levant into its bordering southern and eastern deserts.At present, the rainiest winter seasons in Lebanon and northern and central Israel are associated with more frequent (+ 20%), deeper Cyprus Lows traversing the eastern Mediterranean at approximately the latitude of southern Turkey. Even these wettest years in northern Israel do not yield above average annual rainfall amounts in the hyperarid southern Negev. This region is mainly influenced by the Active Red Sea Troughs that produce only localized rains. The eastern Mediterranean Cyprus Lows also produce more dust storms and transport higher amounts of suspended dust to the loess area than any other atmospheric pattern. Concurrent rainfall and dust are essential to the late Pleistocene formation of the elongated thick loess zone along the desert northern margin. Even with existing dust storms, the lack of rain and very sparse vegetation account for the absence of late Pleistocene loess sequences from the southern Negev and the formation of hyperarid soils.When the north Sinai coast shifted 30–70 km northwest due to last glacial global sea level lowering, the newly exposed coastal areas supplied the sand and dust to these active eastern Mediterranean cyclones. This enforced the latitude of the northern boundary of the loess zone to be directly due east of the LGM shoreline. This shift of coast to the northwest inhibited rainfall in the southern Levant deserts and maintained their hyperaridity. Concurrently, frequent deep eastern Mediterranean Cyprus Lows were funneled along the northern Mediterranean increasing (probably doubling) the rains in central and northern Israel, Lebanon, southwestern Syria and northern Jordan. These storms and rains formed lakes, forests, and speleothems only a short distance north of the deserts in the southern Levant.     

MOC observations of the 2001 Mars planet-encircling dust storm

From 15 September 1997 through 21 January 2006, only a single planet-encircling martian dust storm was observed by MGS-MOC. The onset of the storm occurred on 26 June 2001 (Ls=184.7°), earliest recorded to date. It was initiated in the southern mid-to-low latitudes by a series of local dust storm pulses that developed along the seasonal cap edge in Malea and in Hellas basin (Ls=176.2°-184.4°). The initial expansion of the storm, though asymmetric, was very rapid in all directions (3-32 m s⁻¹). The main direction of propagation, however, was to the east, with the storm becoming planet encircling in the southern hemisphere on Ls=192.3°. Several distinct centers of active dust lifting were associated with the storm, with the longest persisting for 86 sols (Syria-Claritas). These regional storms helped generate and sustain a dust cloud (“haze”), which reached an altitude of about 60 km and a peak opacity of τdust∼5.0. By Ls=197.0°, the cloud had encircled the entire planet between 59.0° S and 60.0° N, obscuring all but the largest volcanoes. The decay phase began around Ls∼200.4° with atmospheric dust concentrations returning to nominal seasonal low-levels at Ls∼304.0°. Exponential decay time constants ranged from 30-117 sols. The storm caused substantial regional albedo changes (darkening and brightening) as a result of the redistribution (removal and deposition) of a thin veneer of surface dust at least 0.1-11.1 μm thick. It also caused changes in meteorological phenomena (i.e., dust storms, dust devils, clouds, recession of the polar caps, and possibly surface temperatures) that persisted for just a few weeks to more than a single Mars year. The redistribution of dust by large annual regional storms might help explain the long period (∼30 years) between the largest planet-encircling dust storms events.     

A review on East Asian dust storm climate, modelling and monitoring

In arid and semi-arid area of Asia, dust storms occur frequently. Asian dust storms have a major impact on the air quality of the densely populated areas of China, Korea and Japan, and are important to the global dust cycle. In extreme cases, they result in the loss of human lives and disruptions of social and economic activities. In recent years, systematic research on Asian dust storms has been carried out. Much progress has been made in the development of integrated dust storm monitoring and modeling systems by making use of advanced numerical models, satellite remote sensing and GIS data. In this paper, we summarize the recent achievements in Asian dust storm research with an emphasis on dust climatology, modeling and satellite monitoring. The concept of integrated dust storm monitoring and modeling system is described and a summary of the developments in key research areas is given, including new dust models and techniques in satellite remote sensing and system integration. We then discuss the current research frontiers and the challenges for future studies.     

An intercomparison of four wet deposition schemes used in dust transport modeling

The characteristics of four wet deposition schemes widely used in dust modeling studies are examined within the framework of a regional scale dust model. Since these schemes are based on different formulations, the scavenging coefficients of them deviate by a factor of 10³ depending on precipitation rate and particle size. The four schemes coupled with the dust model are applied to simulate a 2002 Asian dust event. The corresponding wet deposition patterns and scavenging efficiencies are compared. It is found that apart from the scheme derived from scavenging coefficient measurements, the other three schemes give similar wet deposition patterns although their scavenging efficiencies are different depending on the particle-size range. The results suggest that the performances of these schemes are affected by the particle size distribution of the dust emission, together with the model's performance of precipitation prediction.     

Magnetic field modulated dust streams from Jupiter in interplanetary space

High speed dust streams emanating from near Jupiter were first discovered by the Ulysses spacecraft in 1992. Since then the phenomenon has been re-observed by Galileo in 1995, Cassini in 2000, and Ulysses in 2004. The dust grains are expected to be charged to a potential of , which is sufficient to allow the planet's magnetic field to accelerate them away from the planet, where they are subsequently influenced by the interplanetary magnetic field (IMF). A similar phenomenon was observed near Saturn by Cassini. Here, we report and analyze simultaneous dust, IMF and solar wind data for all dust streams from the two Ulysses Jupiter flybys. We find that compression regions (CRs) in the IMF – regions of enhanced magnetic field – precede most dust streams. Furthermore, the duration of a dust stream is roughly comparable with that of the precedent CR, and the occurrence of a dust stream and the occurrence of the previous CR are separated by a time interval that depends on the distance to Jupiter. The intensity of the dust streams and their precedent CRs are also correlated, but this correlation is only evident at distances from the planet no greater than 2 AU. Combining these observations, we argue that CRs strongly affect dust streams, probably by deflecting dust grain trajectories, so that they can reach the spacecraft and be detected by its dust sensor.     

Climate changes and recent glacier behaviour in the Chilean Lake District

Atmospheric temperatures measured at the Chilean Lake District (38°–42°S) showed contrasting trends during the second half of the 20th century. The surface cooling detected at several meteorological stations ranged from − 0.014 to − 0.021 °C a^− 1, whilst upper troposphere (850–300 gpm) records at radiosonde of Puerto Montt (41°26′S/73°07′W) revealed warming between 0.019 and 0.031 °C a^− 1. Regional rainfall data collected from 1961 to 2000 showed the overall decrease with a maximum rate of − 15 mm a^− 2 at Valdivia st. (39°38′S/73°05′W). These ongoing climatic changes, especially the precipitation reduction, seem to be related to El Niño–Southern Oscillation (ENSO) phenomena which has been more frequent after 1976. Glaciers within the Chilean Lake District have significantly retreated during recent decades, in an apparent out-of-phase response to the regional surface cooling. Moreover, very little is known about upper troposphere changes and how they can enhance the glacier responses. In order to analyse their behaviour in the context of the observed climate changes, Casa Pangue glacier (41°08′S/71°52′W) has been selected and studied by comparing Digital Elevation Models (DEMs) computed at three different dates throughout the last four decades. This approach allowed the determination of ice elevation changes between 1961 and 1998, yielding a mean thinning rate of − 2.3 ± 0.6 m a^− 1. Strikingly, when ice thinning is computed for the period between 1981 and 1998, the resulting rate is 50% higher (− 3.6 ± 0.6 m a^− 1). This enhanced trend and the related area loss and frontal retreat suggests that Casa Pangue might currently be suffering negative mass balances in response to the upper troposphere warming and decreased precipitation of the last 25–30 yr, as well as debris cover would not prevent the glacier from a fast reaction to climate forcing. Most of recent glaciological studies regarding Andean glaciers have concentrated on low altitude changes, namely frontal variations, however, in order to better understand the regional glacier changes, new data are necessary, especially from the accumulation areas.     

Application of artificial neural networks to the prediction of dust storms in Northwest China

Artificial neural networks (ANN) are non-linear mapping structures analogous to the functioning of the human brain. In this study, we take the ANN approach to model and predict the occurrence of dust storms in Northwest China, by using a combination of daily mean meteorological measurements and dust storm occurrence. The performance of the ANN model in simulating dust storm occurrences is compared with a stepwise regression model. The correlation coefficients between the observed and the estimated dust storm occurrences obtained from the neural network procedure are found to be significantly higher than those obtained from the regression model with the same input data. The prediction tests show that the ANN models used in this study have the potential of forecasting dust storm occurrence in Northwest China by using conventional meteorological variables.     

Diagnosis and simulation of a rapidly developing cyclone related to a severe dust storm in East Asia

Mongolian cyclones are important to the outbreaks of severe dust storms in Northeast Asia. In this paper, we conduct a diagnostic study and a numerical simulation of a rapidly developing Mongolian cyclone that produced the April 5 to 7, 2000 severe dust storm in East Asia. The surface pressure of the cyclone decreased rapidly on April 5 to 6 causing strong surface winds. The diagnosis shows that the cyclone was a “dry cyclone”, as the convergence of moisture flux was weak and the baroclinic forcing was strong. The analysis of the Q vectors also reveals that ageostrophic wind was significant in the middle and upper part of the cyclone, resulting in strong vertical motion in the lower part. The three-dimensional structure of the cyclone is characterized by an ascending southern warm current and a descending northern cold current. This structure is favorable to the release of available potential energy and the intensification of the cyclone. In the second part of this study, we develop a coupled system of a dust emission scheme and a mesoscale numerical model (MM5V3) and applied the system to the simulation of the Mongolian cyclone. The main features of the cyclone identified from the diagnostic analysis are successfully reproduced. The predicted dust storm-affected area is found to be consistent with the meteorological observations and satellite remote sensing. It is shown that the coupled system is capable of predicting the spatial and temporal variations of the dust storm.     

Simulations of the impacts of dynamic vegetation on interannual and interdecadal variability of Asian summer monsoon with modern and mid-Holocene orbital forcings

The impacts of dynamic vegetation on interannual and interdecadal variability of Asian summer monsoon in modern (0 kyr) and mid-Holocene (6 kyr) climates are investigated by contrasting simulations with and without dynamic vegetation in a coupled ocean-atmosphere model.According to a dynamic index of South Asian summer monsoon, it has been found that the strengths of interannual and interdecadal westerly wind tend not to be affected by the dynamic vegetation over South Asia in the lower troposphere for 0 kyr and 6 kyr. However, based on a dynamic index of western North Pacific (WNP) monsoon, the strengths of tropical westerly wind and south–north cross-equatorial transport are weakened over the tropical western Pacific in the lower troposphere for 0 kyr and 6 kyr. It suggests the impact of dynamic vegetation is more obvious for the WNP monsoon than for the South Asian monsoon. Also, it implies the impact of dynamic vegetation on the interannual and interdecadal circulations is distinctly regional.Singular value decomposition (SVD) analysis shows that the impact of dynamic vegetation can remodel the leading correlation mode (SVD1) between precipitation and surface temperature. All of the interannual and interdecadal precipitation patterns with and without the impact of dynamic vegetation are associated with positive anomalies over India and southeastern China. However, the impact of dynamic vegetation tends to enhance (keep) the positive interannual temperature anomalies of SVD1 over the midlatitudinal Eurasia (WNP) for 0 kyr, but to reduce the anomalies over the midlatitudinal Eurasia and WNP for 6 kyr. Furthermore, the La Niña-like sea surface temperature (SST) anomalies always dominate the tropics for 0 kyr and 6 kyr. It suggests La Niña-like SST anomalies are the important mechanism to induce the above-mentioned precipitation pattern no matter whether for 0 kyr or for 6 kyr. For the interdecadal surface temperature pattern of SVD1, the impact of dynamic vegetation tends to enhance (reduce) positive anomalies over the midlatitudinal Eurasia (WNP) for 0 kyr, but to reduce (keep) positive anomalies over the midlatitudinal Eurasia (WNP) for 6 kyr. Also, all of the above implies the impact of dynamic vegetation is a mechanism to induce the long-term change of leading interannual and interdecadal surface temperature pattern over the midlatitudinal Eurasia and/or WNP.     

Characterization of Asian Dust during ACE-Asia

ACE-Asia was a multi-national collaboration organized to investigate and understand the chemistry, radiative properties, and climatic effects of mineral dust and other aerosol particles in the East Asia/Northwest Pacific region. Studies conducted at the Gosan and Zhenbeitai surface supersites show striking variations in aerosol concentrations and properties that were affected by the occurrence and origins of the Asian dust storms, air mass pathways, and mixing during the transport. Investigations conducted on the R/V Ronald H. Brown (RHB) showed that dust had a pervasive influence on the chemical composition, size distribution, and optical properties of the aerosol. Analyses using an aerosol time-of-flight mass spectrometer on the RHB showed that most of the coarse-particle nitrate and sulfate in post-frontal air was associated with dust, and more remarkably, that competitive or exclusionary processes evidently are involved in the uptake or production of these substances. Studies conducted onboard the NCAR C-130 aircraft showed that coarse-mode dust was less absorbing and less hygroscopic than pollution aerosol and that there was little correlation in light scattering and absorption by the sub- vs. super-micrometer aerosol. Below 2 km, dust was commonly mixed with pollutants, and this had a stronger influence on the optical properties of the submicrometer particles than the coarse-mode dust; at higher altitudes, the dust was less affected by pollution. Single particle analyses of C-130 samples showed that the mixing of black carbon (BC) with dust was common, but only certain types of BC particles were aggregated. Models were used in the planning, execution and interpretative phases of ACE-Asia; and summaries of modeling results are presented to illustrate the progress being made in identifying new dust sources; in depicting the time-varying, three-dimensional structure of dust plumes; and in quantifying the production, transport, and deposition of Asian dust.     

DuneXpress

The DuneXpress observatory will characterize interstellar and interplanetary dust in-situ, in order to provide crucial information not achievable with remote sensing astronomical methods. Galactic interstellar dust constitutes the solid phase of matter from which stars and planetary systems form. Interplanetary dust, from comets and asteroids, represents remnant material from bodies at different stages of early solar system evolution. Thus, studies of interstellar and interplanetary dust with DuneXpress in Earth orbit will provide a comparison between the composition of the interstellar medium and primitive planetary objects. Hence DuneXpress will provide insights into the physical conditions during planetary system formation. This comparison of interstellar and interplanetary dust addresses directly themes of highest priority in astrophysics and solar system science, which are described in ESA’s Cosmic Vision. The discoveries of interstellar dust in the outer and inner solar system during the last decade suggest an innovative approach to the characterization of cosmic dust. DuneXpress establishes the next logical step beyond NASA’s Stardust mission, with four major advancements in cosmic dust research: (1) analysis of the elemental and isotopic composition of individual interstellar grains passing through the solar system, (2) determination of the size distribution of interstellar dust at 1 AU from 10^− 14 to 10^− 9 g, (3) characterization of the interstellar dust flow through the planetary system, (4) establish the interrelation of interplanetary dust with comets and asteroids. Additionally, in supporting the dust science objectives, DuneXpress will characterize dust charging in the solar wind and in the Earth’s magnetotail. The science payload consists of two dust telescopes of a total of 0.1 m² sensitive area, three dust cameras totaling 0.4 m² sensitive area, and a nano-dust detector. The dust telescopes measure high-resolution mass spectra of both positive and negative ions released upon impact of dust particles. The dust cameras employ different detection methods and are optimized for (1) large area impact detection and trajectory analysis of submicron sized and larger dust grains, (2) the determination of physical properties, such as flux, mass, speed, and electrical charge. A nano-dust detector searches for nanometer-sized dust particles in interplanetary space. A plasma monitor supports the dust charge measurements, thereby, providing additional information on the dust particles. About 1,000 grains are expected to be recorded by this payload every year, with 20% of these grains providing elemental composition. During the mission submicron to micron-sized interstellar grains are expected to be recorded in statistically significant numbers. DuneXpress will open a new window to dusty universe that will provide unprecedented information on cosmic dust and on the objects from which it is derived.     

Recent organic matter accumulation in relation to some climatic factors in ombrotrophic peat bogs near heavy metal emission sources in Finland

Accumulation of organic matter (OM) was studied in four ombrotrophic peat bogs in Finland: Harjavalta (vicinity of a Cu–Ni smelter), Outokumpu (near a closed Cu–Ni mine), Alkkia (Ni-treated site) and Hietajärvi (a pristine site). At each sampling site, two peat cores (15 × 15 × 100 cm) were taken. Age-dating of peat was determined using ²¹⁰Pb method (CRS model). The local annual temperature sum and precipitation for the past 125 years were modeled. The objective was to compare recent net accumulation rates of heavy metal polluted ombrotrophic peat bogs with those of a pristine bog, and to study the relationship between weather and net accumulation rates. Based on ²¹⁰Pb age-dating, the upper 16-cm peat layer at Harjavalta, 35 cm at Outokumpu and 25 cm at Hietajärvi represents 125 years of peat formation, yielding the following average peat accumulation rates: Harjavalta 1.3 mm year^− 1, Outokumpu 2.8 mm year^− 1 and Hietajärvi 2.0 mm year^− 1. At the Alkkia site, the Ni treatment in 1962 had completely stopped the peat accumulation. Net accumulation rates were related to precipitation at Outokumpu, Harjavalta and Hietajärvi sites. In addition, emissions released from the nearby located Cu–Ni smelter could have affected negatively net OM accumulation rate at Harjavalta site.