Analysis of summertime atmospheric transport of fine particulate matter in Northeast Asia

In Northeast Asia, the effect of long-range transport of air pollutants is generally pronounced in spring and winter, but can be important even in summer. This study analyzed summer-time atmospheric transport of elemental carbon (EC) and sulfate (SO₄ ^2?) with the Community Multiscale Air Quality (CMAQ) model driven by the Weather Research and Forecasting (WRF) model. The WRF/CMAQ modeling system was applied to regions ranging from Northeast Asia to the Greater Tokyo Area in Japan in summer 2007. In terms of EC, while the model simulated well the effect of long-range transport, the simulation results indicated that domestic emissions in Japan dominantly contributed (85%) to EC concentrations in the Greater Tokyo. In terms of SO₄ ^2?, the simulation results indicated that both domestic emissions (62%) and long-range transport from the other countries (38%) substantially contributed to SO₄ ^2? concentrations in the Greater Tokyo. Distinctive transport processes of SO₄ ^2? were associated with typical summer-time meteorological conditions in the study region. When a Pacific high-pressure system covered the main island of Japan, domestic emissions, including volcanic emission, dominantly contributed to SO₄ ^2? concentrations in the Greater Tokyo. When a high-pressure system prevailed over the East China Sea and low-pressure systems passed north of Japan, synoptic westerly winds associated with this pressure pattern transported a large amount of SO₄ ^2? from the continent to Japan. In addition, although heavy precipitation and strong wind decreased SO₄ ^2? concentrations near the center of a typhoon, peripheral typhoon winds occasionally played an important role in long-range transport of SO₄ ^2?.     

Active fault traces along Bhuj Fault and Katrol Hill Fault, and trenching survey at Wandhay, Kachchh, Gujarat, India

Several new active fault traces were identified along Katrol Hill Fault (KHF). A new fault (named as Bhuj Fault, BF) that extends into the Bhuj Plain was also identified. These fault traces were identified based on satellite photo interpretation and field survey. Trenches were excavated to identify the paleoseismic events, pattern of faulting and the nature of deformation. New active fault traces were recognized about 1km north of the topographic boundary between the Katrol Hill and the plain area. The fault exposure along the left bank of Khari River with 10m wide shear zone in the Mesozoic rocks and showing displacement of the overlying Quaternary deposits is indicative of continued tectonic activity along the ancient fault. The E-W trending active fault traces along the KHF in the western part changes to NE-SW or ENE-WSW near Wandhay village. Trenching survey across a low scarp near Wandhay village reveals three major fault strands F1, F2, and F3. These fault strands displaced the older terrace deposits comprising Sand, Silt and Gravel units along with overlying younger deposits from units 1 to 5 made of gravel, sand and silt. Stratigraphic relationship indicates at least three large magnitude earthquakes along KHF during Late Holocene or recent historic past.     

Debris-flow release processes investigated through the analysis of multi-temporal LiDAR datasets in north-western Iceland

Debris flows are fast-moving gravity flows of poorly sorted rock and soil, mixed and saturated with water. Debris-flow initiation has been studied using empirical and experimental modelling, but the geomorphic changes, indicative of different triggering processes, are difficult to constrain with field observations only. We identify signatures to distinguish two different debris-flow release styles by integrating high-resolution multi-temporal remote sensing datasets and morphometric analysis. We analyse debris flows sourced above the town of Ísafjörður (Iceland). Two debris-flow triggering processes were previously hypothesised for this site: (i) slope failure, characterised by landslides evolving into debris flows; and (ii) the fire-hose effect, in which debris accumulated in pre-existing, steep-sided bedrock passages is transported by a surge of water. It is unknown which process dominates and determines the local risk. To investigate this question, we compare airborne LiDAR elevation models and aerial photographs collected in 2007 with similar data from 2013. We find that two new debris-flow tracks were created by slope failures. These are characterised by steep sliding surfaces and lateral leveed channels. Slope failure also occurred in two large, recently active tracks, creating the preparatory conditions for the fire-hose effect to mobilise existing debris. These tracks show alternating zones of fill and scour along their length, and debris stored below the source-area at rest angles >35°. Our approach allows us to identify and quantify the morphological changes produced by slope failure release process, which generated the preparatory conditions for the fire-hose effect. As debris flows are rarely observed in action and morphological changes induced by them are difficult to detect and monitor, the same approach could be applied to other landscapes to understand debris-flow initiation in the absence of other monitoring information, and can improve the identification of zones at risk in inhabited areas near hillslopes with potential for debris flows. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

Ejby—A new H5/6 ordinary chondrite fall in Copenhagen,Denmark

On February 6, 2016 at 21:07:19 UT, a very bright fireball was seen over the eastern part of Denmark. The weather was cloudy over eastern Denmark, but many people saw the sky light up—even in the heavily illuminated Copenhagen. Two hundred and thirty three reports of the associated sound and light phenomena were received by the Danish fireball network. We have formed a consortium to describe the meteorite and the circumstances of the fall and the results are presented in this paper. The first fragment of the meteorite was found the day after the fall, and in the following weeks, a total of 11 fragments with a total weight of 8982 g were found. The meteorite is an unbrecciated, weakly shocked (S2), ordinary H chondrite of petrologic type 5/6 (Bouvier et al. 2017). The concentration of the cosmogenic radionuclides suggests that the preatmospheric radius was rather small ~20 cm. The cosmic ray exposure age of Ejby (83 ± 11 Ma) is the highest of an H chondrite and the second highest age for an ordinary chondrite. Using the preatmospheric orbit of the Ejby meteoroid (Spurny et al. 2017) locations of the recovered fragments, and wind data from the date of the fall, we have modeled the dark flight (below 18 km) of the fragments. The recovery location of the largest fragment can only be explained if aerodynamic effects during the dark flight phase are included. The recovery location of all other fragments are consistent with the dark flight modeling.