Dust Storm Conditions Research Articles

5G-28 GHz Signal Transmission Over Hybrid All-Optical FSO/RF Link in Dusty Weather Conditions

5G wireless networks promise to provide massive bandwidth for various types of connections. In such networks, the backhaul/fronthaul sections should be easy to deploy and support the required high bandwidth. To improve the free space optic (FSO) link bandwidth so that it can replace fiber cables and support 5G networks, all-optical FSO systems were proposed which exploit advanced modulation formats in the transmitter side and coherent detection in the receiver side. However, such links will suffer much under harsh outdoor environment, especially under fog and dust conditions than traditional FSO links that have limited bandwidth. Effect of fog on such links has been investigated in the literature. However, the dust effect is not covered. In this paper, we first experimentally analyzed the effects of dust storms on the performance of an all-optical FSO link carrying a 1-Gbaud/16-quadrature amplitude modulation 5G signal. The results demonstrate that the all-optical FSO link is significantly affected by low visibility range, with severe bit-error-rate (BER), and error vector magnitude (EVM) limits appearing at a 50-m visibility range for a 2.7-m channel length. For a visibility range greater than 200-m, the BER and EVM were improved to 10−9 and 5.5% of the root mean square, respectively. Furthermore, the analysis showed that the dust storm condition introduces flat fading over the frequency range under study, i.e., 21–29 GHz. Second, a comparison between FSO and radio frequency (RF) channels under the same dusty conditions were performed. The results showed that the effects of the dust storm are negligible for the RF link which makes it suitable as a backup for FSO link under severe dust conditions. Finally, a hybrid cascaded FSO/RF link was installed and analyzed in terms of visibility range, BER, and EVM.

Effects of airborne particulate matter (PM10) from dust storm and thermal inversion on global DNA methylation in human peripheral blood mononuclear cells (PBMCs) in vitro

Scientists have considered epigenetic modifications as a possible mechanism to deal with adverse effects of air pollution. This study aimed to compare the effect of PM10 (PM with aerodynamic diameter ≤ 10 μm) from dust storm and inversion conditions on in vitro global methylation in human peripheral blood mononuclear cells (PBMCs). PM10 was sampled in Tehran, Iran, at a point impacted with dust storm and inversion. PM toxicity was determined using the MTT assay. PBMCs were extracted from whole blood of healthy males and treated separately with a mixture of pooled PM10 from inversion and dusty conditions at concentrations of 50–300 μg/mL for 4 h. Untreated cells were used as the negative control. Moreover, 5-methylsytosine (%5-mC) and 5-hydroxymethylcytosine (%5-hmC) were measured by the enzyme-linked immunosorbent assay (ELISA) method. Daily average PM10 concentrations in dusty and inversion days were 348.40 and 220.54 μg/m3, respectively. The mean of %5-mC (2.04 ± 1.49%) was estimated 12 times more than that of %5-hmC (0.17 ± 0.11%). PM10 resulting from the both sources caused DNA hypomethylation; however, this effect from inversion (median = 3%, IQR = 2.4%) was found to be significantly more than that from dust storm (median = 1.1%, IQR = 1.38%). Moreover, particles increased %5-hmC caused by PM10, which was significantly greater when resulting from inversion (0.23 ± 0.1%) than from dust storm (0.12 ± 0.09%). Furthermore, %5-mC and %5-hmC were significantly different at different PM10 concentrations (50–300 μg/mL) so that a significant difference was observed between %5-mC and %5-hmC at extreme concentrations. Results showed that PM10 from inversion caused a significantly more global methylation than that from dust storm. It can be concluded that measurement of 5-mC and 5-hmC as epigenetic modifications in environmental studies of DNA methylation can be a good procedure to determine health effects related to PM10 exposure.

Morphology, Mineralogy and Mixing of Individual Atmospheric Particles Over Kanpur (IGP): Relevance of Homogeneous Equivalent Sphere Approximation in Radiative Models

Estimation of the direct radiative forcing (DRF) by atmospheric particles is uncertain to a large extent owing to uncertainties in their morphology (shape and size), mixing states, and chemical composition. A region-specific database of the aforementioned physico-chemical properties (at individual particle level) is necessary to improve numerically-estimated optical and radiative properties. Till date, there is no detailed observation of the above mentioned properties over Kanpur in the Indo-Gangetic Plain (IGP). To fill this gap, an experiment was carried out at Kanpur (IITK; 26.52°N, 80.23°E, 142 m msl), India from April to July, 2011. Particle types broadly classified as (a) Cu-rich particles mixed with carbon and sulphur (b) dust and clays mixed with carbonaceous species (c) Fe-rich particles mixed with carbon and sulfur and (d) calcite (CaCO3) particles aged with nitrate, were observed. The frequency distributions of aspect ratio (AR; indicator of extent of particle non-sphericity) of total 708 particles from April to June reveal that particles with aspect ratio range >1.2 to ≤1.4 were abundant throughout the experiment except during June when it was found to shift to high AR range, >1.4 to ≤1.6 (followed with another peak of AR i.e. >2 to ≤2.4) due to dust storm conditions enhancing the occurrence of more non-spherical particles over the sampling site. The spherical particles (and close to spherical shape; AR range, 1.0 to ≤1.2) were found to be <20% throughout the experiment with a minimum (11.5%) during June. Consideration of Homogeneous Equivalent Sphere Approximation (HESA) in the optical/radiative model over the study region is found to be irrelevant during the campaign.

Community analysis of Persian oak fungal microbiome under dust storm conditions

Abstract Dust storms have major effects on terrestrial ecosystems through the long-distance transport and deposition of particulate matter. It is unclear how dust deposition affects plant-associated microbiomes in downwind ecosystems. Here we show that dust deposition may negatively influence the isolation, richness, and diversity of endophytic fungal communities of Persian oak. We used culture-based methods paired with Sanger sequencing to examine these effects on fungal assemblages isolated from leaf, branch and deposited dust. Increased amounts of dust deposition led to decreased endophytic fungal diversity in plant tissues but increased fungal diversity in deposited dust layers on leaves. Dust deposition decreased the abundance of a dominant endophyte in branches with promising biocontrol properties. Endophytic fungal communities found in leaves were more similar to fungal assemblages of deposited dust in comparison to branch endophytes. Our results suggest that dust storms may have ecosystem-wide effects by altering the fungal microbiomes of forest-forming trees.

Dust Particle Size Distributions during Spring in Yinchuan, China

Dust particle size distributions in Yinchuan, China, were measured during March and April 2014, using APS-3321 sampler. The distributions were measured under different dust conditions (background, floating dust, blowing dust, and dust storm) and statistical analyses were performed. The results showed that, under different dust conditions, the instantaneous number concentrations of dust particles differed widely. For example, during blowing sand and dust storm conditions, instantaneous dust particles concentrations varied substantially, while, under floating dust conditions, concentration differences were relatively small. The average dust particles size distributions were unimodal under all dust conditions, but the average surface area and mass size distributions were all bimodal. These distributions had peaks in different locations under different dust conditions. Under different dust conditions, wind speed and humidity were very important factors for particles size distributions. With increasing wind speed and decreasing humidity, fine particles were dominant in the atmosphere and the number and mass distributions of the coarse particles were indicative of long-range transport from surrounding deserts. Different dust conditions had different influences on PM1, PM2.5, and PM10concentrations.

Influence of dust accumulation on building roof thermal performance and radiant heat gain in hot-dry climates

This paper presents an effort to estimate the impact of dust accumulation on exterior building roof absorptivity and total radiative heat gain. A new model is introduced to calculate a building solar absorptivity as a function of dust accumulation rate. Hourly dust deposition is modeled using the Non-hydrostatic Multi-scale Model (NMMB) to predict monthly averaged dust accumulation over time. The correlation sensitivities to its input parameters and the impact of dust accumulation on building annual loads are also studied. Results show that dust accumulation increases the roof solar absorptivity from its initial value up to dust absorptivity based on the site climatic condition and roof characteristics. The predicted monthly averaged accumulated dust for all studied sites varies between 1.3 and 73.8g/m2/month. The new model has resulted in an annual cooling space increase of 44.7–181.1kWh/m2/year, for the selected hot-dry sites with moderate to extreme dust storm conditions. Heating reductions were found to be 0.5–13.1kWh/m2/year which are not significant in comparison to the increase in annual cooling load. The results of this work were attempted to improve the predictive capability of current building simulation models.

Modeling the microphysics of CO2 ice clouds within wave-induced cold pockets in the martian mesosphere

Mesospheric CO2 ice clouds on Mars are simulated with a 1D microphysical model, which includes a crystal growth rate adapted to high supersaturations encountered in the martian mesosphere. Observational constraints (crystal radius and opacity) exist for these clouds observed during the day around the equator at ∼60–80km altitude. Nighttime mesospheric clouds interpreted as CO2 ice clouds have also been characterized at low southern latitudes, at ∼90–100km altitude. From modeling and observational evidence, it is believed that mesospheric clouds are formed within temperature minima created by thermal tides, where gravity wave propagation allows for the creation of supersaturated layers (cold pockets). Thus, temperature profiles perturbed by gravity waves are used in the model to initiate nucleation and maintain growth of CO2 ice crystals. We show that it is possible to reproduce the observed effective radii for daytime and nighttime clouds. Crystal sizes are mainly governed by the altitude where the cloud forms, and by the amplitude of supersaturation. The temporal and spatial behavior of the cloud is controlled by the extent and lifetime of the cold pocket. The cloud evaporates fast after the cold pocket has vanished, implying a strong correlation between gravity wave activity and CO2 cloud formation. Simulated opacities remain far below the observed ones as long as typical dust conditions are used. In the case of the lower daytime clouds, the enhanced mesospheric dust loading typically reached during dust storm conditions, allows for greater cloud opacities, close to observed values, by supplying the atmosphere with condensation nuclei. However, CO2 ice clouds are not detected during the dust storm season, and, because of fast sedimentation of dust particles, an exogenous supply (meteoritic flux) appears necessary to explain opacities of both daytime and nighttime mesospheric CO2 ice clouds along their whole period of observation.

Background-like nitrate in desert air

The atmospheric nitrogen cycle is a key process driving the earth's environmental evolution. Current model studies require knowledge of NOx soil emissions from various land types, but desert emissions remain unquantified or are not addressed with high confidence. Our measurements at two observatories in Taklimakan desert during a dust episode showed an approximately stable and dust-independent nitrate in the air. Its concentration estimated from PM2.5, PM10 and TSP samples under non-dust, floating dust and dust storm conditions was 3.81 ± 1.24 μg m−3, 2.95 ± 0.69 μg m−3, 4.99 ± 1.71 μg m−3, respectively, despite the more-than-one-order difference of dust loading. This concentration was much larger than that in remote marine and tropical forest air. Comprehensive investigation revealed a similar presence of nitrate in other desert air. The nitrate was hypothesized to be the consequence of the conversion of NOx released from desert soils. These results indicate a background-like nitrate and active reactions of nitrogen compounds in desert air.

Chemical characteristics of atmospheric fallout in the south of Xi'an during the dust episodes of 2001–2012 (NW China)

Atmospheric fallouts (AFs) were collected in the south of Xi'an, NW China, during the dust episodes of 2001–2012. The chemical characteristics of total 68 AF samples including their chemical compositions, size distribution and magnetic susceptibility were studied. The contamination degree and the source of heavy metals in AF were also explored with enrichment factor method and multivariate statistical analysis. The results showed that the particle mass size distribution of AFs dominated by coarse particles (PM10–50) in dust days. The concentrations of 26 elements associated with AFs determined by wavelength dispersive X-ray fluorescence spectrometry (WDXRF) in studied sites varied from 92.90 to 188.10 mg kg−1 for Cr, 31.40 and 63.00 mg kg−1 for Cu, 16.60 to 167.30 for Pb and 106.60 to 196.80 for Zn. Their average concentrations found in this study were 139.22 ± 29.41 mg kg−1, 46.93 ± 10.56 mg kg−1, 78.42 ± 46.52 mg kg−1 and 150.61 ± 32.84 mg kg−1, respectively, which exceeded their corresponding recommended background values more than two times. While, other elements, such as Br varied from 1.10 to 5.90 with 3.34 ± 1.60 mg kg−1 mean, Cs from 2.90 to 10.90 with mean of 7.23 ± 2.47 mg kg−1, Ga between 6.90 and 20.80 with 15.23 ± 3.59 mg kg−1, Rb in the range of 62.10–124.20 with the average of 80.69 ± 16.89 mg kg−1, Y from 9.90 to 35.00 with 20.43 ± 6.27 mg kg−1 average, La from 29.60 to 54.20 with mean of 37.28 ± 8.28 mg kg−1 and V with average of 81.97 ± 8.93 mg kg−1 in the 57.7–92.10 mg kg−1. Multivariate statistical analysis (principal component analysis and clustering analysis) was suggested that the principal element elements, Al, Fe, Si, K, Ca, Na, Mg, coupled with the trace elements Co, V, Ce, Mn, Ni, Ga, Y, Rb, La, Br, Cs were predominated by crustal material sources, whereas, Cr, Cu, Ba, Sr, As, Pb and Zn were highly influenced by anthropogenic activities. Simultaneously, the water-soluble ions (WS-ions) of NH4+, SO42−, SO32−, NO3−, SiO44−, HSO4− contained in APs identified by FT-IR spectroscopy were possible originated from coal combustion. The results were also confirmed and consistent with the observations of magnetic susceptibility (MS), enrichment factor (EFs) and contamination evaluation analysis. With such rates of atmospheric fallouts that contain elevated levels of toxic elements during the dust storm condition, actions should be taken to continually examine and understand of the potential impacts of AFs on surface ecosystem, water resource, and human health in the dust storm condition.

The semidiurnal tide in the middle atmosphere of Mars

AbstractAtmospheric thermal tides are global oscillations in atmospheric fields that are subharmonics of a solar day. While atmospheric tides on Earth are mainly relevant in the upper atmosphere, on Mars, they dominate temperature variations and winds throughout the atmosphere. Observations and model simulations to date have suggested that the migrating diurnal tide is the predominant mode in the Martian atmosphere, and that the semidiurnal tide is only relevant in the tropical middle atmosphere during conditions of high dust loading. New comprehensive observations by the Mars Climate Sounder in a geometry that allows coverage of multiple local times show that the semidiurnal tide is a dominant response of the Martian atmosphere throughout the Martian year. The maximum semidiurnal amplitude of ~ 16 K is found at southern winter high latitudes, which makes it the largest tidal amplitude observed in the Martian middle atmosphere outside of dust storm conditions. The semidiurnal tide can be successfully modeled due to recent advances of Mars General Circulation Models (MGCMs) that include the radiatively active treatment of water ice clouds. Tidal forcing occurs through absorption of radiation by aerosols and points to the vertical structure of dust and clouds and their radiative effects as being essential for our understanding of the thermal structure and the general circulation of the Martian atmosphere. As with terrestrial GCMs trying to quantify mechanisms affecting climate, future Mars modeling efforts will require microphysical schemes to control aerosol distributions, and vertically and temporally resolved measurements of temperature and aerosols will be essential for their validation.

Aerosol optical absorption by dust and black carbon in Taklimakan Desert, during no-dust and dust-storm conditions

Aerosol absorption coefficient σap involves the additive contribution of both black carbon aerosol (BC) and dust aerosol. The linear statistical regression analysis approach introduced by Fialho et al. (2005) is used to estimate the absorption exponents of BC and dust aerosol absorption coefficients, and further to separate the contributions of these two types of aerosols from the total light absorption coefficient measured in the hinterland of Taklimakan Desert in the spring of 2006. Absorption coefficients are measured by means of a 7-wavelength Aethalometer from 1 March to 31 May and from 1 November to 28 December, 2006. The absorption exponent of BC absorption coefficient α is estimated as (−0.95±0.002) under background weather (supposing the observed absorption coefficient is due only to BC); the estimated absorption exponent of dust aerosol absorption coefficient β during the 6 dust storm periods (strong dust storm) is (−2.55±0.009). Decoupling analysis of the measured light absorption coefficients demonstrates that, on average, the light absorptions caused by dust aerosol and BC make up about 50.5% and 49.5% respectively of the total light absorption at 520nm; during dust weather process periods (dust storm, floating dust, blowing dust), the contribution of dust aerosol to absorption extinction is 60.6% on average; in the hinterland of desert in spring, dust aerosol is also the major contributor to the total aerosol light absorption, more than that of black carbon aerosol.

Aeolian processes and dune morphology in Gale Crater

Datasets at resolutions many times greater than previously available were used to study aeolian features within Gale Crater. High resolution thermal inertia data allowed for detailed particle size estimation, with the data sufficient to resolve dunefields. A wide range of grain sizes have now been identified in the Gale Crater dunefields, ranging from medium to very coarse sand. High Resolution Imaging Science Experiment (HiRISE) and THEMIS VIS data allowed for detailed analysis of the dune morphology and slip-faces, which shows that the dunes have responded to topographic influences on prevailing wind directions under a present day wind regime. This result was corroborated by a regional mesoscale model for the crater under dust storm conditions. The central mound and smaller scale crater floor topography has altered the prevailing wind regime and dune patterns. Aeolian activity has thus played, and continues to play, an important role in shaping many of the present surface features of Gale Crater. The arrival of a future lander mission such as the Mars Science Laboratory would be able to sample these surface features directly and add a wealth of data to the understanding of Gale Crater.

Impact of Dust Transported from China on Air Quality in Korea -Characteristics of PM2.5Concentrations and Metallic Elements in Asan and Seoul, Korea

[ <TEX>$PM_{2.5}$</TEX> ], particulate matter less than 2.5 um in a diameter, can penetrate deeply into the lungs. Exposure to <TEX>$PM_{2.5}$</TEX> has been associated with increased hospital visits for respiratory aliments as well as increase mortality. <TEX>$PM_{2.5}$</TEX> is a byproduct of combustion processes and as such has a complex composition including a variety of metallic elements, inorganic and organic compounds as well as biogenic materials (microorganisms, proteins, etc). In this study, the average concentrations of fine particulates <TEX>$PM_{2.5}$</TEX> have been measured simultaneously in Asan and Seoul, Korea, by using particulate matter portable sampler from September 2001 to August 2002. Sample collection filters were analyzed by ICP-OES to determine the concentrations of metallic elements (As, Ni, Fe, Cr, Cd, Cu, Pb, Zn, Si). Annual mean <TEX>$PM_{2.5}$</TEX> concentrations in Asan and Seoul were 37.70 and <TEX>$45.83\;{\mu}g/m^3$</TEX>, respectively. The highest concentrations of <TEX>$PM_{2.5}$</TEX> were found in spring season in both cities and the concentrations of measured metallic elements except As in Asan were higher than those in Seoul, suggesting that yellow dust in spring could affect <TEX>$PM_{2.5}$</TEX> concentrations in Asan rather than Seoul. The correlation coefficients of Pb and Zn were 0.343 for Asan and 0.813 for Seoul during non-yellow dust condition, suggesting that Pb and Zn were influenced with the same sources. The correlation coefficients between Si and Fe in the fine particulate mode were 0.999 (Asan) and 0.998 (Seoul) during yellow dust condition. It was suggested that these two elements were impacted by soil-related transport from China during the yellow dust storm condition.

Albedo models for the residual south polar cap on Mars: Implications for the stability of the cap under near-perihelion global dust storm conditions

It is uncertain whether the residual (perennial) south polar cap on Mars is a transitory or a permanent feature in the current Martian climate. While there is no firm evidence for complete disappearance of the cap in the past, clearly observable changes have been documented. Observations suggest that the perennial cap lost more CO 2 material in the spring/summer season prior to the Mariner 9 mission than in those same seasons monitored by Viking and Mars Global Surveyor. In this paper we examine one process that may contribute to these changes—the radiative effects of a planet encircling dust storm that starts during late Martian southern spring on the stability of the perennial south polar cap. To approach this, we model the radiative transfer through a dusty planetary atmosphere bounded by a sublimating CO 2 surface. A critical parameter for this modeling is the surface albedo spectrum from the near-UV to the thermal-IR, which was determined from both space-craft and Earth-based observations covering multiple wavelength regimes. Such a multi-wavelength approach is highly desirable since one spectral band by itself cannot tightly constrain the three-parameter space for polar surface albedo models, namely photon “scattering length” in the CO 2 ice and the amounts of intermixed water and dust. Our results suggest that a planet-encircling dust storm with onset near solstice can affect the perennial cap's stability, leading to advanced sublimation in a “dusty” year. Since the total amount of solid CO 2 removed by a single storm may be less than the total CO 2 thickness, a series of dust storms would be required to remove the entire residual CO 2 ice layer from the south perennial cap.

Impacts of wind velocity on sand and dust deposition during dust storm as inferred from a series of observations in the northeastern Qinghai–Tibetan Plateau, China

The monthly sand and dust deposition flux and modern dust storms were monitored in the northern Qaidam Basin of the Qinghai–Tibetan Plateau. The monthly sand and dust flux varied between 0.57 and 18.12 mg cm − 2 month − 1 from June 2003 to April 2005, and was well correlated with the monthly extreme wind velocity ( V extr) ( r 2 = 0.60, n = 23). Sand and dust was mainly deposited in spring and early summer in the study area. The weight of settled sand and dust collected during dust storms exhibited a positive correlation with the mean 10-min wind velocity ( r 2 = 0.60, n = 16) during the dust storms. For the typical dust storms, the weight and flux of settled sand and dust will linearly increase with the increasing wind strength and fluctuation amplitude of wind velocities. The coarse fraction (> 63 μm) also increases with them, in contrast, the fine-grained fraction (< 63 μm) decreases. It is plausible to assume that most of the fine-grained dust particles are lifted and transported far from the region under dust storm conditions, especially under the stronger and more variable wind conditions. The results demonstrate that the wind regime (strength and variability) is a key control on the sand and dust deposition during dust storm; dust can be emitted from the Qaidam Basin as one of dust source areas in China.

Aeolian process and pedogenesis under the influence of the East Asian monsoon: A statistical approach to particle-size distribution variability

The grain size of Chinese loess has been widely regarded as a sensitive proxy for the intensity of the wind strength associated with the winter component of the East Asian monsoon. The majority of papers concerned with loess particle size examine variations in moments of the particle size distribution. However, in coastal geomorphological research parametric models have been used and the samples represented by resulting parameter estimates. Here we investigate the use of log-hyperbolic and log-skew-laplace models to distinguish between loess, loess subgroups and palaeosols in a particularly high accumulation rate profile from the NW Chinese loess plateau area. The aim is to define narrow units of ‘pristine’ loess that may indicate brief returns to dust storm conditions. With this approach, units within the loess, previously ascribed to Heinrich events, can be seen to have a particular particle size distribution signature, thus allowing them to be stratigraphically and environmentally constrained. Parametric models applied to grain-size distribution data in Chinese loess make a useful addition to previously used particle size techniques that have demonstrated cyclicity on a scale similar to that of Dansgaard–Oeschger events in ice cores and those designed to determine the degree of loess pedogenesis such as micromorphology and magnetic enhancement. The aim of our work is to make full use of particle size distribution data in the wider context of palaeoenvironmental reconstruction.

Simulation of a Solar Stirling Engine Operating Under Various Weather Conditions on Mars

A solar stirling engine based on a horizontal selective flat-plate converter is analyzed in this work. A detailed model for the heat losses towards the atmosphere is presented. The engine’s output power is maximised numerically. The analysis is based on meteorological data measured at Viking Landers sites during clear sky and dust storm conditions. All the computations were performed for a solar collection area similar in size with that of Mars Pathfinder’s Sojourner. The efficiency of converting solar energy into mechanical work at noon is as high as 18%. The power provided by the engine is as high as 16 W during autumn and winter. These results suggest that under the Martian environment the performance of properly designed solar Stirling engines is comparable with that of PV cell power systems.

Equatorial jets in the dusty Martian atmosphere

We investigate the production of equatorial jets which demonstrate strong local superrotation in an atmospheric general circulation model of Mars. These westerly jets are driven by diurnal thermal tides, and their strength is shown to be closely related to the amount of dust in the atmosphere. The superrotating jets are strongest near to equinox and under conditions of high atmospheric dust loading. If there is sufficient dust, in amounts corresponding to dust storm conditions, the westerly equatorial jets can occur at any time of year and reach speeds of over 40 m/s, peaking between 10 and 20 km altitude. For more moderate dust amounts, typical of background levels on Mars, the jets are still strong when the subsolar point is close to the equator and latitudinally symmetric tidal modes are forced. Strong easterly retrograde winds are also found high above the equator, and it is shown that the thermal tides play a major role in their formation. This process is especially relevant close to equinox when the cross‐equatorial meridional circulation is weak.

A general circulation model simulation of the Martian polar warming

This paper reports on a successful general circulation model simulation of a rapid warming phenomenon observed in the Martian winter polar atmosphere during global dust storm conditions. The model includes a self‐consistent simulation of the dust distribution which is forced with a prescribed surface source. The warming is shown to be largely a response to the development of a pole‐to‐pole solstitial Hadley circulation resulting from the greatly increased dust loading. A crucial aspect of the simulation is a sufficiently deep computational domain that allows for the full development of this circulation. These simulations indicate that the thermal tides play a contributing role by providing zonal momentum flux divergence at the winter pole and by the advection of aerosol.

On the impact of thermal stability on some rough flow effects over mobile surfaces

Calculations are made of the effects of thermal stability under a range of conditions, over the sea and land, on the physical factors (including the critical wind speed) affecting dust-storm generation, snow drift, and rough sea conditions. The computational procedure involves the surface friction velocity, u*, and its relation with the aerodynamic roughness over aerodynamically rough, mobile surfaces. The results indicated that even at relatively high wind speeds, thermal effects under extreme advection situations may be significant, particularly for those properties of the agitated surface dependent on u*3 and u*4.