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Multiscale Spatiotemporal Analysis of Extreme Events in the Gomati River Basin, India
Accelerating climate change is causing considerable changes in extreme events, leading to immense socioeconomic loss of life and property. In this study, we investigate the characteristics of extreme climate events at a regional scale to ‐understand these events’ propagation in the near fu-ture. We have considered sixteen extreme climate indices defined by the World Meteorological Or-ganization’s Expert Team on Climate Change Detection and Indices from a long‐term dataset (1951– 2018) of 53 locations in Gomati River Basin, North India. We computed the present and future spatial variation of theses indices using the Sen’s slope estimator and Hurst exponent analysis. The periodicities and non‐stationary features were estimated using the continuous wavelet transform. Bivariate copulas were fitted to estimate the joint probabilities and return periods for certain com-binations of indices. The study results show different variation in the patterns of the extreme climate indices: D95P, R95TOT, RX5D, and RX showed negative trends for all stations over the basin. The number of dry days (DD) showed positive trends over the basin at 36 stations out of those 17 stations are statistically significant. A sustainable decreasing trend is observed for D95P at all stations, indi-cating a reduction in precipitation in the future. DD exhibits a sustainable decreasing trend at almost all the stations over the basin barring a few exceptions highlight that the basin is turning drier. The wavelet power spectrum for D95P showed significant power distributed across the 2–16‐year bands, and the two‐year period was dominant in the global power spectrum around 1970–1990. One interest-ing finding is that a dominant two‐year period in D95P has changed to the four years after 1984 and remains in the past two decades. The joint return period’s resulting values are more significant than values resulting from univariate analysis (R95TOT with 44% and RTWD of 1450 mm). The difference in values highlights that ignoring the mutual dependence can lead to an underestimation of extremes. © 2021 by the author. Licensee MDPI, Basel, Switzerland.
Office Indoor PM and BC Level in Lithuania: The Role of a Long-Range Smoke Transport Event
While the impacts of climate change on wildfires and resulting air pollution levels have been observed, little is known about how indoor air filtering systems are performing under intensive smoke conditions. For this aim, particle number size distribution and concentration in a size range 0.5–18 μm and equivalent black carbon (eBC) mass concentration were measured in a modern office with a mechanical ventilation system. Measurements took place from 30 September to 6 October 2020 in the Center for Physical Sciences and Technology (FTMC) campus located in the urban background environment in Lithuania. During the measurement campaign, an intensive pollution episode, related to long-range transport wildfire smoke, was observed. The results indicated that the smoke event increased both indoor and outdoor eBC mass concentrations twice. Filters were non-selective for different eBC sources (biomass burning versus traffic) or chemical composition of carbonaceous aerosol particles (eBC versus brown carbon (BrC)). Air filtering efficiency was found to be highly dependent on particle size. During the smoke event the highest particle number concentration was observed at 2.1 μm and 1.0 μm size particles in outdoor and indoor air, respectively. Differences of indoor to outdoor ratio between event and non-event days were not significant. Because of lower removal rate for small particles, eBC had higher contribution to total PM2.5 mass concentration in indoor air than in outdoor air. The results gained are crucial for decision-making bodies in order to implement higher-quality air-filtering systems in office buildings and, as a result, minimize potential health impacts. © 2021 by the authors.
Climate Variability in Central Europe during the Last 2500 Years Reconstructed from Four High-Resolution Multi-Proxy Speleothem Records
The Late Holocene was characterized by several centennial-scale climate oscillations including the Roman Warm Period, the Dark Ages Cold Period, the Medieval Warm Period and the Little Ice Age. The detection and investigation of such climate anomalies requires paleoclimate archives with an accurate chronology as well as a high temporal resolution. Here, we present 230Th/U-dated high-resolution multi-proxy records (δ13C, δ18O and trace elements) for the last 2500 years of four speleothems from Bunker Cave and the Herbstlabyrinth cave system in Germany. The multi-proxy data of all four speleothems show evidence of two warm and two cold phases during the last 2500 years, which coincide with the Roman Warm Period and the Medieval Warm Period, as well as the Dark Ages Cold Period and the Little Ice Age, respectively. During these four cold and warm periods, the δ18O and δ13C records of all four speleothems and the Mg concentration of the speleothems Bu4 (Bunker Cave) and TV1 (Herbstlabyrinth cave system) show common features and are thus interpreted to be related to past climate variability. Comparison with other paleoclimate records suggests a strong influence of the North Atlantic Oscillation at the two caves sites, which is reflected by warm and humid conditions during the Roman Warm Period and the Medieval Warm Period, and cold and dry climate during the Dark Ages Cold period and the Little Ice Age. The Mg records of speleothems Bu1 (Bunker Cave) and NG01 (Herbstlabyrinth) as well as the inconsistent patterns of Sr, Ba and P suggests that the processes controlling the abundance of these trace elements are dominated by site-specific effects rather than being related to supra-regional climate variability.
Atmospheric Dynamics and Numerical Simulations of Six Frontal Dust Storms in the Middle East Region
This study analyzes six frontal dust storms in the Middle East during the cold period (October–March), aiming to examine the atmospheric circulation patterns and force dynamics that triggered the fronts and the associated (pre-or post-frontal) dust storms. Cold troughs mostly located over Turkey, Syria and north Iraq played a major role in the front propagation at the surface, while cyclonic conditions and strong winds facilitated the dust storms. The presence of an upper-atmosphere (300 hPa) sub-tropical jet stream traversing from Egypt to Iran constitutes also a dynamic force accompanying the frontal dust storms. Moderate-Resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) observations are used to monitor the spatial and vertical extent of the dust storms, while model (Weather Research and Forecasting model coupled with Chemistry (WRF-Chem), Copernicus Atmospheric Monitoring Service (CAMS), Regional Climate Model-4 (RegCM4)) simulations are also analyzed. The WRF-Chem outputs were in better agreement with the MODIS observations compared to those of CAMS and RegCM4. The fronts were identified by WRF-Chem simulations via gradients in the potential temperature and sudden changes of wind direction in vertical cross-sections. Overall, the uncertainties in the simulations and the remarkable differences between the model outputs indicate that modelling of dust storms in the Middle East is really challenging due to the complex terrain, incorrect representation of the dust sources and soil/surface characteristics, and uncertainties in simulating the wind speed/direction and meteorological dynamics. Given the potential threat by dust storms, more attention should be directed to the dust model development in this region. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Real World Vehicle Emission Factors for Black Carbon Derived from Longterm In-Situ Measurements and Inverse Modelling
Black carbon (BC) is one of the most harmful substances within traffic emissions, contributing considerably to urban pollution. Nevertheless, it is not explicitly regulated and the official laboratory derived emission factors are barely consistent with real world emissions. However, realistic emission factors (EFs) are crucial for emission, exposure, and climate modelling. A unique dataset of 10 years (2009–2018) of roadside and background measurements of equivalent black carbon (eBC) concentration made it possible to estimate real world traffic EFs and observe their change over time. The pollutant dispersion was modelled using the Operational Street Pollution Model (OSPM). The EFs for eBC are derived for this specific measurement site in a narrow but densely trafficked street canyon in Leipzig, Germany. The local conditions and fleet composition can be considered as typical for an inner-city traffic scenario in a Western European city. The fleet is composed of 22% diesel and 77% petrol cars in the passenger car segment, with an unknown proportion of direct injection engines. For the mixed fleet the eBC EF was found to be 48 mg km−1 in the long-term average. Accelerated by the introduction of a low emission zone, the EFs decreased over the available time period from around 70 mg km−1 to 30 – 40 mg km−1 . Segregation into light (<3.5 t) and heavy (>3.5 t) vehicles resulted in slightly lower estimates for the light vehicles than for the mixed fleet, and one order of magnitude higher values for the heavy vehicles. The found values are considerably higher than comparable emission standards for particulate matter and even the calculations of the Handbook Emission Factors for Road Transport (HBEFA), which is often used as emission model input. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
The Memory of a Fault Gouge: An Example from the Simplon Fault Zone (Central Alps)
Faut gouge forms at the core of the fault as the result of a slip in the upper brittle crust. Therefore, the deformation mechanisms and conditions under which the fault gouge was formed can document the stages of fault movement in the crust. We carried out a microstructural analysis on a fault gouge from a hanging-wall branch fault of the Simplon Fault Zone, a major low-angle normal fault in the European Alps. We use thin-section analysis, together with backscattered electron imaging and X-ray diffractometry (XRD), to show that a multistage history from ductile to brittle deformation within the fault gouge. We argue that this multistage deformation history is the result of continuous exhumation history from high to low temperature, along the Simplon Fault Zone. Because of the predominance of pressure solution and veining, we associated a large part of the deformation in the fault gouge with viscous-frictional behaviour that occurred at the brittle-ductile transition. Phyllosilicates and graphite likely caused fault lubrication that we suggested played a role in localizing slip along this major low-angle normal fault.
Can Green Plants Mitigate Ammonia Concentration in Piglet Barns?
For animal welfare and for farmers’ health, the concentration of ammonia (NH3 ) in animal houses should be as low as possible. Plants can remove various atmospheric contaminants through the leaf stomata. This study examined the effect of ornamental plants installed inside a piglet barn on the NH3 concentration in the air. Gas measurements of the air in the ‘greened’ compartment (P) and a control compartment (CTR) took place over two measuring periods (summer–autumn and winter). Differences between the NH3 emissions were calculated based on the ventilation rates according to the CO2 balance. Fairly low mean NH3 concentrations between 2 and 4 ppm were measured. The NH3 emissions were about 20% lower (p < 0.01) in P than in CTR, in summer–autumn and in winter period. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Observation of the Ionosphere in Middle Latitudes during 2009, 2018 and 2018/2019 Sudden Stratospheric Warming Events
The ionospheric weather is affected not only from above by the Sun but also from below by processes in the lower-lying atmospheric layers. One of the most pronounced atmospheric phenomena is the sudden stratospheric warming (SSW). Three major SSW events from the periods of very low solar activity during January 2009, February 2018, and December 2018/January 2019 were studied to evaluate this effect of the neutral atmosphere on the thermosphere and the ionosphere. The main question is to what extent the ionosphere responds to the SSW events with focus on middle latitudes over Europe. The source of the ionospheric data was ground-based measurements by Digisondes, and the total electron content (TEC). In all three events, the ionospheric response was demonstrated as an increase in electron density around the peak height of the F2 region, in TEC, and presence of wave activity. We presume that neutral atmosphere forcing and geomagnetic activity contributed differently in individual events. The ionospheric response during SSW 2009 was predominantly influenced by the neutral lower atmosphere. The ionospheric changes observed during 2018 and 2018/2019 SSWs are a combination of both geomagnetic and SSW forcing. The ionospheric response to geomagnetic forcing was noticeably lower during time intervals outside of SSWs. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.