Alfred Wegener Institute’s (AWI) IceBird program is a series of airborne campaigns carried out in winter and summer using a fixed-wing Basler BT-67 research aircraft to measure Arctic sea ice and to monitor its change. In 2017, the primary scientific instrument configuration including an airborne laser scanner (ALS) for surface topography and freeboard measurements and a tethered electromagnetic induction sounding instrument (EM-Bird) for total (snow+ice) thickness measurements was complemented with an ultrawideband frequency-modulated continuous-wave microwave radar to measure snow thickness. With the unique instrumentation onboard the IceBird campaigns, we are able to observe the respective thicknesses of the snow and sea-ice layers in high resolution along survey tracks on regional scale. Here, we describe the IceBird program concept and focus on the winter campaigns that take advantage of the full instrument configuration. We present recent data of high-resolution, collocated, airborne sea-ice and snow thickness and freeboard measurements based on over 3000 km of profiles collected in the western Arctic Ocean in April 2017 and 2019. The individual parameters are important for describing and monitoring the state of the Arctic sea ice and validating retrievals from satellite data, but combined they offer further possibilities to characterize sea ice. By assuming isostatic equilibrium, we are able to derive up-to-date estimates for sea-ice bulk density for first-year and multi-year ice, including deformed ice. As an outlook, we derive a parametrization of sea-ice bulk density based on sea-ice freeboard for further applications, such as evaluating the freeboard-to-thickness conversion for satellite altimetry.

The slot region between the radiation belts in the magnetosphere is considered to be stable and safe for satellite missions, but strong disturbances during space weather events can cause an enhancement of the electron radiation environment in this area. This paper provides an analysis of the dynamics of electron flux in 1998-2007 with specific attention to slot filling events and preceded geomagnetic activity. Flux of energetic electrons, with energies E>0.63 MeV, E>1.5 MeV, and E>3 MeV, was obtained from detectors on board the HEO-3 satellite in highly elliptical orbit. To evaluate geomagnetic conditions, associated with enhancement of electron flux, all the ‘slot filling events’ were studied together with geomagnetic activity provided by Dst and Kp global indices as well as with thehourly range indices of geomagnetic variations at mid-latitude. These geomagnetic indices were used for assessment of a threshold and frequency of occurrence of slot filling events. Regression analysis has been used to find a relationship between the maximum filling of the slot region due to space weather event and preceding geomagnetic activity level. Influence of the cumulative time of periods of enhanced geomagnetic activity to the variation of the electron flux in the slot region has been analysed. Suitability of different indices of geomagnetic activity for estimation of rate of occurrence of slot filling events and for assessment of electron flux in the slot region is discussed.

A drought is a slowly developing natural phenomenon that can occur in all climatic zones and can be defined as a temporary but significant decrease in water availability. Over the past three decades, the cost of droughts in Europe has amounted to over 100 billion euros and it is expected to considerably increase as future droughts are projected to be more severe and long-lasting. Although drought monitoring and management are largely studied in the literature, they often fail at yielding precise information on critical events occurrence and associated impacts such as reduction of electricity production or crop failures. This is due to the difficulty of capturing the complexity of drought dynamics, which evolve over diverse temporal (and spatial) scales, including short-term meteorological droughts, medium-term agricultural droughts, and long-term hydrological droughts, as well as the non-physical aspects related to droughts (water management, irrigation, etc.). In this work, we contribute a Machine Learning based framework named FRIDA (FRamework for Index-based Drought Analysis) for the identification of impact-based, site-specific drought indexes. FRIDA is a fully automated data-driven approach that relies on advanced feature extraction algorithms to identify relevant drought drivers from a pool of candidate hydro-meteorological variables. Selected predictors are combined into an index representing a surrogate of the drought conditions in the considered area, including either observed or simulated water deficits or remotely sensed information about the state of the crops. FRIDA is portable across different contexts for supporting the formulation of basin-specific indexes to better inform drought management strategies. Several real-world examples will be used to provide a synthesis of recent applications of FRIDA in case studies featuring diverse hydroclimatic conditions and variable levels of data availability.

The 3D S-wave velocity of shallow structure, especially the Quaternary sediments at 0-1 km near the surface, is an important issue of concern in urban planning and construction for the requirements of seismic hazard assessment and disaster mitigation. Due to the facility and less dependence on the site environment, noise-based technique is an ideal way to acquire the fine structure of urban sedimentary basin. Based on the dense array composed of more than 900 stations deployed in Tongzhou at a local scale of 20 × 40 km2, we proved the lateral variation of the phase velocity of multi-mode surface waves can be estimated directly with adequate accuracy by beamforming seismic noise with moving subarray, without tomography. Rayleigh wave phase velocity maps, at frequencies between 0.3 and 2.5 Hz for the fundamental mode as well as 0.8 and 3.0 Hz for the first overtone, are obtained. The 3D S-wave velocity model at 0-1 km depth with lateral resolution of 1 km is then established by inverting phase velocity maps of two modes. The thickness of the sediments is delineated by the impedance interface given by microtremor H/V (horizontal-to-vertical) spectral ratio. The model is in good agreement with tectonic unit. The sedimentary thickness of Daxing high and two sags located around Gantang and Xiadian are respectively 100-400 m and 400-600 m, which correlates well with the isosurface of S-wave velocity at 1 km/s. The model also presents some evidence on the extension of Daxing fault along NE direction.

First-arrival traveltime tomography (FATT) has been one of the commanding tomographic approaches for long wavelength velocity model building. Nowadays, FATT models are often used as initial models for more resolving imaging methods such as full-waveform inversion (FWI). In this context, improving the accuracy of FATT model is crucial to mitigate the nonlinearity of FWI. In spite of the widespread use of FATT at all scales (from near surface to global scale), it suffers from ill-posedness in terms of non-uniqueness of the solution due to the deficient information carried out by the sole traveltime attribute. We promote the use of the traveltime perturbation with respect to the source/receiver positions (horizontal component of the slowness vector or slope) as a supplement to the first-arrival traveltime (Tavakoli et al., 2018). For multi-component controlled-source experiments, we can generally take advantage of the fine source sampling to measure slopes by tracking local coherency over few neighboring traces in addition to traveltimes in common-receiver gathers, while slopes at the receiver position may be estimated by polarization analysis. The information of differential nature carried out by slopes yields a higher order sensitivity with respect to the subsurface parameters. We implement our first-arrival slope+traveltime (FASTT) tomography with eikonal solver and the matrix-free adjoint-state method, as previously proposed by Taillandier et al.(2009) for FATT. We illustrate the resolution power of FASTT relatively to FATT for coarse ocean bottom seismometer (OBS) acquisitions using two benchmarks based upon the EAGE/SEG Overthrust model at the exploration scale and a synthetic model of the eastern-Nankai subduction zone at the deep crustal scale (Górszczyk et al., 2018), then assess the quality of the tomographic models as initial models for FWI. We finally present an application to real OBS data collected during the SFJ experiment in the eastern Nankai Trough (Tokai area).

To simulate the outgassing of CO2 and water from Martian mantle, I used a two-dimensional numerical model of magmatism in the convecting mantle. The mantle is internally heated by incompatible heat-producing elements (HPEs) that decay with time. Mantle convection is driven by thermal, compositional, and melt-buoyancy. Mantle convection causes magmatism, that is, a decompression melting of upwelling mantle materials and upward permeable flow of the generated basaltic magma through the convecting mantle. Water is incompatible and concentrates to magma in a partially molten region, while there is a saturation limit for CO2 in magma that depends on the oxygen fugacity. Water and CO2 in magma are transported upward to the surface by migrating magma and are outgassed to the atmosphere when they ascend to the top of the mantle. Both water and CO2 reduces the solidus temperature and the viscosity of solid mantle materials. The calculated mantle evolves in four stages: in Stage I, an extensive magmatism forms the crust and compositionally differentiates the mantle; in Stage II, the resulting compositional stratification of the mantle suppresses magmatism and mantle convection for tens to hundreds of millions of years to allow heat to build up in the deep mantle; in Stage III, magma is generated at depth, and the buoyancy of generated magma induces plumes that ascend through the stratified mantle to cause an episodic magmatism; in Stage IV, the magmatism subsides due to extraction of HPEs from the mantle by the magmatism itself. The episodic magmatism in Stage III outgasses water and CO2. The total amount of outgassed water is typically 100-200 m GEL (global equivalent layer), while that of outgassed CO2 is around 105 Pa s or less, when the oxygen fugacity of the mantle is in the range of Iron-Wustite (IW) buffer to one log-unit higher. This amount of CO2 is not large enough to account for the clement surface environment of early Mars by itself even when H2O enhances the greenhouse effect of CO2. Other greenhouse gasses or a remnant of the CO2 that was supplied at the time of planetary formation may have played an important role in realizing the surface environment of early Mars that was favorable to life.

Water is one of the most important substances for plants. Limited water supplies directly influence crop yield, which eventually leads to food scarcity to humans. In this present study, we quantify the dynamics of a fluttering leaf as a function of the days without water. The deformation and vibration of a plant leaf can be induced by dropping an object or tapping with a finger. Using multiple cameras, the 3D motion of a leaf can be measured. We found that the frequency of a leaf increases with water stress. In terms of natural frequency, it tends to increase when moisture stress is applied to leaves. These results suggest that the stiffness of leaves according to moisture stress is related, so it can be used as an indicator of the overall performance of plants. This would lead to a nondestructive way to measure water stress through leaf stiffness.

China is home to 12% of the world’s grasslands; second largest in the world. The productivity of Chinese grasslands rapidly declined from 10% degraded in 1970 to 90% degraded by the 2000s. Inner Mongolia, China, is composed of 67%, mainly temperate, grasslands. From 1947-2009 human and livestock populations in Inner Mongolia increased from 5.6-24.7 million and 8.4-96.0 million, respectively. These changes were not only due to rising population increasing food demand, but also policy and lifestyle changes. Though climate change and overgrazing are dominant drivers of degradation, research shows that policies increasing privatization of land rights have significant impacts, namely the Household Production Responsibility System (HPRS) of 1949. In China, grassland degradation is linked to environmental problems of sandstorms, losses of biodiversity and carbon sinks, and droughts. Grassland degradation led to widespread public health concerns including dust storms originating from the arid rangelands of Inner Mongolia that swept pollution across major population centers in China and other Asian countries. Inner Mongolia climate change is evident: from 1951-2009 mean temperature increased at 0.28°C per decade, doubling the global linear warming trend of 0.138°C. This temperature increase was accompanied by a 9.9 mm decrease in precipitation per decade, resulting in decreased gross primary productivity measured by Normalized Difference Vegetation Index (NDVI). This study aims to quantify the Balagaer River Watershed degradation in Inner Mongolia, China from 2000-2019 and explore correlations between climate change, NDVI values, and degradation status. Researchers used GIS analysis of MODIS NDVI data and regressions of NDVI on precipitation and potential evapotranspiration (PET). Differences in NDVI were calculated between years and classified degradation into three categories: slightly, moderately, and heavily degraded. These calculations quantified the percentage of the watershed occupied by each category. Correlations between NDVI and precipitation and NDVI and PET were conducted using Excel at three temporal scales: annual, pre-growing season (October to April), and growing season (May to September). It is expected that decreased precipitation contributed to decreased NDVI.

Clouds play a significant role in the Earth’s energy balance and hydrological cycle through their effects on radiation and precipitation, and therefore are crucial for life on Earth. Earth’s NexT‐generation ICE mission (ENTICE) is proposed to measure diurnally resolved global vertical profiles of cloud ice particle size, ice water content, and in-cloud humidity and temperature using multi-frequency sub-millimeter (sub-mm) microwave radiometers and a 94 GHz cloud radar from space. The scientific objective of ENTICE is to identify the important processes by which anvil clouds evolve and interact with ambient thermodynamic conditions to advance our fundamental understanding of clouds and reduce uncertainties in cloud climate feedback. Whether such an objective could be achieved depends on the orbital sampling characteristics of the mission. In this study, ENTICE sampling statistics are simulated using five different scanning methods in a 400 km altitude precession orbit with an inclination of 65°: nadir, forward pointing, side scanning, and conical scanning for the radiometers, and nadir pointing for the radar. Using the GEOS-5 Nature Run produced at 7-km and 30-min resolution, sampling statistics with respect to cloud types and local hours with enhancement from radar are calculated for ENTICE. The wide swath of ENTICE radiometers by conical and side scanning methods ensures ample high cloud samples gathered by ENTICE over its two-year mission for different types of clouds with sufficient sampling over the diurnal cycles. Sampling differences between radar and radiometers at nadir demonstrate that the combination of radar and radiometers will allow for measurements of cloud vertical profiles. Therefore, our results show that the designed orbit sampling of ENTICE is sufficient to fulfill the mission science goals.

Community science is a collaboration between scientists and communities including their citizens and their leaders. In this collaboration, the scientists and communities together determine the questions to be studied, the approaches to be taken, and the interpretation of the results. Such a collaboration requires a foundation of scientific literacy within the community to enable both individuals and the community as whole to access the needed scientific understanding and to participate in the scientific process. It also requires that scientists and educators learn about the knowledge, values, norms, and priorities of the communities in which they are working—a kind of scientific community literacy. The EarthConnections Alliance supports the engagement of educational institutions and programs in community science while building community science literacy and scientific community literacy. The EarthConnections Alliance is formed of regional groups that are invested in linking geoscience learning and community service across grade levels within their communities as well as program partners who have expertise needed to create these learning opportunities. All members share a vision of creating learning pathways with four critical elements: 1) they connect opportunities to learn geoscience with opportunities to use this knowledge in service to the local community; 2) they link geoscience learning opportunities and learners across grade levels; 3) they use signposting and mentoring to guide and support students; and 4) they lead to local employment opportunities and geoscience-related careers. Initial funding for EarthConnections explored the creation of regional pathways in diverse sites across the country, the development of strategies and tools for supporting pathway development, and mechanisms for sharing resources and expertise within the Alliance. Over 125 individuals and groups are now engaged in this effort. Further information is available on the EarthConnections website: serc.carleton.edu/EarthConnections.html.

Most studies of earthquake source parameters give detailed information about individual earthquakes. A complementary approach is examining large datasets to gain insight into general properties of many earthquakes, rather than specifics for individual earthquakes. In the traditional formulation for inverse problems, such studies gain high stability - general properties - at the cost of low resolution - specifics for individual earthquakes. In one study we compared moment tensors in the USGS and the Global CMT Project catalogs. The differences are typically an order of magnitude larger than the reported errors, suggesting that the errors substantially underestimate the uncertainty. GCMT generally reports larger scalar moments than the USGS, with the difference decreasing with magnitude. This difference is larger and of opposite sign from that expected due to the different definitions of the scalar moment. Instead, the differences are intrinsic to the tensors, presumably in part due to different phases used in the inversions. A second study examines non-double-couple (NDC) components of moment tensors, which may reflect complex source processes for earthquakes in specific tectonic environments, the combined effect of double couple sources with different geometries, or artifacts of the inversion. A large dataset of moment tensors for earthquakes from three global and four regional catalogs shows that NDC components are essentially independent of magnitude for earthquakes with 2.9 < Mw < 8.2, with a mean deviation from a double-couple source of ~20%. The consistency suggests that most NDC components do not reflect complex rupture processes, which should be a greater effect for larger earthquakes because a significant NDC component requires substantially different geometry between portions of the rupture. Furthermore, there is essentially no difference in NDC components between earthquakes with different fault mechanisms, in different tectonic environments, or in different types of lithosphere. This consistency indicates that most NDC components do not reflect actual source processes, which would likely cause variability. Hence although some earthquakes have real NDC components, it appears that for most earthquakes, especially smaller ones, NDC components are likely to be artifacts of the inversion.

Ertel’s potential vorticity theorem is essentially a clever combination of two conservation principles. The result is a conserved scalar q that accurately reflects vorticity values that fluid parcels can possess and acts as a tracer for fluid flow. While true at large horizontal scales in the ocean and atmosphere, at increasingly smaller scales and in sharply curved fronts, its accuracy breaks down. This is because Earth’s rotation imparts angular momentum to fluid parcels and the conservation of absolute angular momentum L restricts the range of centripetal accelerations possible in balanced flow; this correspondingly restricts vorticity. To address this discrepancy, we revisit Ertel’s derivation and obtain a new conserved scalar Lq that more properly reflects the vorticity of fluid parcels at these small horizontal scales. Although limited to flows on the f plane, this theorem nevertheless highlights a fundamental principle applicable to all geophysical fluids: at sufficiently small horizontal scales such that L can appropriately be conserved, centripetal accelerations-or curvature-can modify the vorticity of fluid parcels observed on the sphere.

In this study, we present zircon U-Pb ages, Hf-O isotopes, and whole-rock geochemical data for the newly identified Duobaoshan appinite-granite suite in the eastern Central Asian Orogenic Belt (CAOB). Field and petrographic investigations show that this suite of rocks is composed of hornblende gabbro, quartz monzonite, and granite porphyry. The appinites are abnormally hornblende-rich, and contain spectacular hornblende phenocrysts, pegmatitic textures, and miarolitic cavity structures that indicate an anomalous water-rich origin. The quartz monzonite and granite porphyry show intrusive contact relations with the appinites. Secondary ion mass spectrometry (SIMS) zircon dating reveals that the Duobaoshan appinite-granite suite was emplaced in a very short time interval of 224–223 Ma. These samples show typical subduction related arc magmatic geochemical characteristics that are enriched in large-ion lithophile elements (LILEs) and light rare earth elements (REEs), depleted in high field strength elements (HFSEs) and middle and heavy REEs. All samples exhibit comparative total REEs and no significant evolutionary relationships. The appinites show high Sr/Y ratios (reaching ~100) and positive or zero Eu anomalies, which reveal amphibole fractionation promotion and plagioclase fractionation suppression in a water-rich magma system. The quartz monzonite possesses high Sr/Y and La/Yb ratios that exhibit adakite-like properties and were derived from thickened lower continental crust. The granite porphyry is silica-rich and non-adakitic. All samples have juvenile whole-rock initial 87Sr/86Sr ratios (~0.7038) and ɛNd(t) values. Zircons have depleted mantle-like ɛHf (t) (to +12.0) and δ18O (~+5.65‰) values. Combining these geochemical features with observations of the regional geology and tectonic setting, we propose that the Duobaoshan appinite-granite suite was generated under a Triassic back-arc extensional setting related to the southward subduction of the Mongol-Okhotsk Ocean. The appinites were derived from an unusual water-rich mantle source, which was previously metasomatized by slab-derived fluids. The quartz monzonite and granite porphyry were generated from partial melting of the juvenile lower continental crust triggered by coeval appinitic magma underplating.

This paper presents new zircon U-Pb ages and whole-rock geochemical data for Triassic granitoids in the Duobaoshan ore field, in the eastern Central Asian Orogenic Belt (CAOB). Dating results reveal that the Triassic granitoids in the Duobaoshan area were emplaced ca. 244–223 Ma. These samples are typical subduction-related arc magmatic rocks that are enriched with large-ion lithophile elements (LILEs), depleted in high field strength elements (HFSEs), and have relatively high Sr (average 1,036 ppm) and low Y (average 10 ppm) and Yb (average 1 ppm) contents that exhibit adakite-like geochemical properties. The samples feature a juvenile whole rock average initial 87Sr/86Sr ratio of 0.70394 and an average ɛNd(t), zircon ɛHf(t), and two-stage Hf model age of 4.62, 10.29, and 766 Ma respectively. These geochemical features reveal a thickened lower crust source. Comprehensive analyses of the early Paleozoic, Triassic, and early Jurassic granitoids in the Duobaoshan area indicate that the magmatism of these three stages was related to the melting of the juvenile lower continental crust materials. The early Paleozoic was the primary period of vertical crust growth, during which time the juvenile lower continental crust was formed. The Triassic granitoids derived from magma were generated by partial melting of the thickened juvenile lower crust and the Jurassic granitoids derived from the partial melting of the delaminated juvenile lower crust. Geological observation and tectonic setting analyses reveal that the Paleo-Asian Ocean tectonic regime in the Duobaoshan area switched to the Mongol-Okhotsk Ocean in the Mesozoic after its closure. The early Paleozoic granitoids were formed in a subduction setting related to the northwestward subducted Paleo-Asian Oceanic slab underlying the Erguna-Xing’an composite block. The Triassic granitoids were formed under a supra-subduction extensional regime related to the southward subduction of the Mongol-Okhotsk Ocean, and the Jurassic granitoids were generated under a slab rollback setting related to the late stage subduction of the Mongol-Okhotsk Ocean.

Palaeogene Environmental evolution in East Asia remains ambiguous. Here we present integrative work including magnetostratigraphy, grain-size, geochemistry, and clay minerals from a 1609-m-thick fluviolacustrine sequence in eastern China. The results reveal two periods of tectonic control alternating with three periods of climatic control of the sedimentary evolution. Tectonic activity, as revealed by particle coarsening and reduced weathering, occurs during 65.6-59 Ma around the study area, and increases in Asia during 55-54 Ma in response to the India-Eurasia collision. Weathering enhances gradually in East Asia during 59-55 Ma, probably caused by global warming. Continuous global warming during 54-50.5 Ma is responsible for enhanced aridification in East Asia. From 50.5 to 37.6 Ma, global cooling weakens evapotranspiration and increases westerlies-derived moisture. Both aspects increase effective moisture and chemical weathering in East Asia. These results shed light on how alternating tectonism and climate change impact environmental evolution in Asia during the Palaeogene.

The Lithium Nevada Corp. Thacker Pass Project has a measured resource of 242M tonnes at 0.29% Li (~0.7M tonnes Li). The deposit is the southernmost of five known lenses hosted within intracaldera tuffaceous sediments along the west side of the McDermitt caldera, which formed by eruption of 16.4 Ma peralkaline-metaluminous tuff. Analyses of 9880 core samples (~1.5-m thick) give a mean of ~ 2500 ppm Li, with some >8800 ppm. Entire sedimentary sections in the southern and western parts of the caldera basin have high Li (1500+ ppm). Pre-caldera rocks, the McDermitt Tuff, late caldera volcanics, and unaltered tuffaceous sediments have relatively low Li (5 -140 ppm). Sediment deposition was mainly subaqueous in the closed caldera basin. Li-rich fill may have been deposited from airborne sources. Claystone comprises most of the Thacker Pass deposit and dominates Li-rich intervals. The rest is mostly feldspar-rich ash. X-ray diffraction (XRD) data from six core holes across the deposit show consistent lateral mineral zoning. A Li-rich zone (mean >4,000 ppm) mainly contains illitic clay and underlies a zone of lower Li with smectite + analcime. Based on XRD peak locations and chemistry, the closest analogs to the illitic clay are Li micas (e.g. tainiolite). Montmorillonitic clay and a basal silicified zone underlie the illitic zone. Some transitional rock of mixed-layer clay between the illite and smectite zones also has high Li. All clay has similar optical properties but SEM images show illite forms tiny hexagonal plates and smectite has no resolvable crystallinity. Calcite, albite, K-feldspar, and quartz occur in all zones, dolomite and fluorite near the top of the illite zone, and pyrite and bitumen in unoxidized rock. The Li-rich zone has relatively high K, Rb, Mo, As, and Sb. Secondary Kspar in the Li-rich zone gave an 40Ar/39Ar age of 14.87±0.05 Ma. No origin fully explains known characteristics. The presence of illite suggests a moderate temperature hydrothermal system. Release of Li from tuffaceous sediments and transport by alkaline groundwater are consistent with most mineralogy (characteristic of closed hydrologic system diagenesis) and with the Kspar date that long postdates caldera magmatism. Release of 10 ppm Li from the likely 50-200 km3 of intracaldera sediments would contribute ~1-4M tonnes Li.

Air composition of the Lewis-Clark Valley (LCV) was studied over a two-year period to investigate the effects of a local pulp paper mill on ambient air and to assess potential health risk to the community. Lewiston, Idaho and Clarkston, Washington are twin cities in the Snake River Valley bordering North-Central Idaho and Southeastern Washington, with a population of over 50,000 including the surrounding areas. The paper mill is located in North Lewiston and releases malodorous sulfur air pollutants in the LCV. The neighboring Nez Perce Tribe has conducted a couple of air studies, in 2006-2007 and the summer of 2016-17, but to date no longer term study has taken place. Our current study utilized active air sampling via sorbent tubes followed by thermal desorption gas chromatography-mass spectrometry (TD-GC-MS) analysis to measure over 50 volatile organic compounds, hazardous air pollutants, and sulfides in ambient air (adapted from EPA Method TO-17). Seasonal, diurnal, and spatial variations in air composition were explored. In addition, monthly averaged passive air samples were collected for comparison at nearby urban areas – Boise, ID, Coeur d’Alene, ID, and Spokane, WA in 2018. In the LCV, dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) were the primary sulfur compounds detected, with concentrations highest adjacent to the paper mill. However, concentrations varied considerably depending on time of day, season, location and meteorology. Seasonal observations include DMS, benzene and chloroform peaking in the summer months, while DMDS peaks in the winter. Diurnal trends show DMS and chloroform with higher values during the morning hours than later in the day. The long-term monthly samples show benzene decreasing from winter to spring, with LCV levels comparable to Coeur d’Alene and Spokane, and Boise slightly higher. In most cases, benzene levels exceed those recommended for ambient air in the state of Idaho. Sources and potential health implications will be discussed.

Immersion freezing is an important heterogeneous ice nucleation process in mixed-phase clouds. Many researches on immersion freezing focus on the parameterization using the classical nucleation theory. However, the ice nucleating abilities of the atmospheric aerosol particles are not well understood, and therefore cause difficulties of the parameterization of immersion freezing. In this study, we investigate the ice nucleating ability of Marigold pollen from the Beijing area by doing drop immersion freezing experiments in the laboratory. Marigold pollen are first mixed with pure water. A population of drops with a volume of 10 mL from the mixture are then put on a PE film in a chamber with a cooling rate of about 0.5 °C min-1. We find that the median freezing temperature of drops with pollen as ice nuclei is -17 °C. The contact angle parameterization of immersion freezing using the classical nucleation theory is also given in this study. We use the single-θ and the θ-pdf parameterization schemes to explain the data. The results show that the θ-pdf parameterization scheme is better for describing the ice nucleating behavior of the pollen in Beijing.