scholarly journals Assumptions on mixing heights influence the quantification of emission sources: A case study for Cyprus

2016 ◽  
Author(s):  
Imke Hüser ◽  
Hartwig Harder ◽  
Angelika Heil ◽  
Johannes W. Kaiser
Keyword(s):  
Forest Fires ◽  
Mixing Layer ◽  
Particle Dispersion ◽  
Emission Sources ◽  
Source Contributions ◽  
Mixing Layer Height ◽  
Spatio Temporal ◽  
The Impact ◽  
Flexpart Model

Abstract. Lagrangian particle dispersion models (LPDMs) in backward mode are widely-used to quantify the impact of transboundary pollution on downwind sites. Most LPDM applications assume mixing of surface emissions in a boundary layer that is constant in height. The height of this mixing layer (ML), however, is subject to strong spatio-temporal variability. Neglecting this variability may introduce substantial errors in the quantification of source contributions. Here, we perform backward trajectory simulations with the FLEXPART model starting at Cyprus to quantify these errors. The simulations calculate the sensitivity to emissions of upwind pollution sources within the ML height. The emission sensitivity is used to quantify source contributions at the receptor and support the interpretation of ground measurements carried out during the CYPHEX campaign in July 2014. It is determined by two interacting factors: the dilution of pollutants within the ML and the number of trajectories impacted by the emissions. In this study, we calculate the emission sensitivity for a constant ML height of 300 m and a dynamical ML height to compare the resulting differences. The results show that the impact of emission sources is predominantly overestimated by the neglected dilution in expanded daytime ML heights. There is, however, substantial variability in the simulated differences. For shallow marine or nocturnal ML heights, for example, a ML assumed to high may lead to an underestimation of the intensive concentrations. This variability is predominantly caused by the spatio-temporal changes in ML heights and the meteorological conditions that drive the dispersion of the trajectories. In an application example, the impact of CO emissions from hypothetical forest fires is simulated and source contributions are compared for different ML heights. The resulting difference shows that the 300 m overestimates the total CO contributions from upwind sources by 16 %. Thus, it is recommended to generally implement a dynamic mixing layer height parametrization in LPDMs to prevent these errors.

scholarly journals Assumptions about footprint layer heights influence the quantification of emission sources: a case study for Cyprus

2017 ◽  
Vol 17 (18) ◽  
pp. 10955-10967 ◽  
Author(s):  
Imke Hüser ◽  
Hartwig Harder ◽  
Angelika Heil ◽  
Johannes W. Kaiser
Keyword(s):  
Mixing Layer ◽  
Particle Dispersion ◽  
Reasonable Assumption ◽  
Night Time ◽  
Meteorological Model ◽  
Source Contributions ◽  
Time Sensitivity ◽  
Tracer Particles ◽  
Constant Height ◽  
The Impact

Abstract. Lagrangian particle dispersion models (LPDMs) in backward mode are widely used to quantify the impact of transboundary pollution on downwind sites. Most LPDM applications count particles with a technique that introduces a so-called footprint layer (FL) with constant height, in which passing air tracer particles are assumed to be affected by surface emissions. The mixing layer dynamics are represented by the underlying meteorological model. This particle counting technique implicitly assumes that the atmosphere is well mixed in the FL. We have performed backward trajectory simulations with the FLEXPART model starting at Cyprus to calculate the sensitivity to emissions of upwind pollution sources. The emission sensitivity is used to quantify source contributions at the receptor and support the interpretation of ground measurements carried out during the CYPHEX campaign in July 2014. Here we analyse the effects of different constant and dynamic FL height assumptions. The results show that calculations with FL heights of 100 and 300 m yield similar but still discernible results. Comparison of calculations with FL heights constant at 300 m and dynamically following the planetary boundary layer (PBL) height exhibits systematic differences, with daytime and night-time sensitivity differences compensating for each other. The differences at daytime when a well-mixed PBL can be assumed indicate that residual inaccuracies in the representation of the mixing layer dynamics in the trajectories may introduce errors in the impact assessment on downwind sites. Emissions from vegetation fires are mixed up by pyrogenic convection which is not represented in FLEXPART. Neglecting this convection may lead to severe over- or underestimations of the downwind smoke concentrations. Introducing an extreme fire source from a different year in our study period and using fire-observation-based plume heights as reference, we find an overestimation of more than 60  % by the constant FL height assumptions used for surface emissions. Assuming a FL that follows the PBL may reproduce the peak of the smoke plume passing through but erroneously elevates the background for shallow stable PBL heights. It might thus be a reasonable assumption for open biomass burning emissions wherever observation-based injection heights are not available.

scholarly journals Vertically-resolved Characteristics of Air Pollution during Two Severe Winter Haze Episodes in Urban Beijing, China

2017 ◽  
Author(s):  
Qingqing Wang ◽  
Yele Sun ◽  
Weiqi Xu ◽  
Wei Du ◽  
Libo Zhou ◽  
...  
Keyword(s):  
Mixing Layer ◽  
Urban Site ◽  
Formation Mechanisms ◽  
Vertical Profiles ◽  
Severe Winter ◽  
Aerosol Composition ◽  
Layer Height ◽  
Mixing Layer Height ◽  
The Impact ◽  
Beijing China

Abstract. We conducted the first real-time continuous vertical measurements of particle extinction (bext), gaseous NO2, and black carbon (BC) from ground level to 260 m during two severe winter haze episodes at an urban site in Beijing, China. Our results illustrated four distinct types of vertical profiles: 1) uniform vertical distributions (37 % of the time) with vertical differences less than 5 %; 2) higher values at lower altitudes (29 %); 3) higher values at higher altitudes (16 %), and 4) significant decreases at the heights of ~ 100–150 m (14 %). Further analysis demonstrated that vertical convection as indicated by mixing layer height, temperature inversion, and local emissions are three major factors affecting the changes in vertical profiles. Particularly, the formation of Type 4 was strongly associated with the stratified layer that was formed due to the interactions of different air masses and temperature inversions. Aerosol composition was substantially different below and above the transition heights with ~ 20–30 % higher contributions of local sources (e.g., biomass burning and cooking) at lower altitudes. A more detailed evolution of vertical profiles and their relationship with the changes in source emissions, mixing layer height, and aerosol chemistry was illustrated by a case study. BC showed overall similar vertical profiles as those of bext (R2 = 0.92 and 0.69 in November and January, respectively). While NO2 was correlated with bext for most of the time, the vertical profiles of bext/NO2 varied differently for different profiles, indicating the impact of chemical transformation on vertical profiles. Our results also showed that more comprehensive vertical measurements (e.g., more aerosol and gaseous species) at higher altitudes in the megacities are needed for a better understanding of the formation mechanisms and evolution of severe haze episodes in China.

Computation of Temporal Decline to a Vanished Island A Case Study Zalzal Koh

2019 ◽  
Author(s):  
Ali Asghar ◽  
Muhammad Ayaz Ahmad ◽  
Memona Zafar ◽  
Shazma Saman ◽  
Muhammad Awais Arshad ◽  
...  
Keyword(s):  
Water Waves ◽  
Dead Sea ◽  
Strike Slip ◽  
Landsat 8 ◽  
Reduced Pressure ◽  
Richter Scale ◽  
Pressure Water ◽  
Spatio Temporal ◽  
The Impact

A massive tremor stuck Baluchistan Pakistan on September 24, 2013 with a magnitude of 7.7 recorded on Richter scale. The epicenter was Awaran Baluchistan which directly affected about 300,000 people leaving about 386 causalities. The impact of this earthquake was so much large that it created a new landmass which was named as Zalzala Koh later. It was the result of strike slip faulting at a depth of 15km. The new born island was full of rich minerals, gases and dead sea animals. This island was 60 feet high, 100 feet wide and 250 feet long. The classification results of Landsat 8 show that the island completely disappeared in 2019 after 6 six years of its birth. First the volume of this island decreases due to reduced pressure of internal gases and secondly, the high-pressure water waves vanished it completely. Satellite imagery proved efficient for spatio-temporal monitoring of various landuse classes.

scholarly journals Mixing-layer height retrieval with ceilometer and Doppler lidar: from case studies to long-term assessment

2014 ◽  
Vol 7 (11) ◽  
pp. 3685-3704 ◽  
Author(s):  
J. H. Schween ◽  
A. Hirsikko ◽  
U. Löhnert ◽  
S. Crewell
Keyword(s):  
Mixing Layer ◽  
Weather Conditions ◽  
Cloud Base ◽  
Layer Height ◽  
Essential Variable ◽  
Mixing Layer Height ◽  
Wind Lidar ◽  
One Year ◽  
Transition Times

Abstract. Aerosol signatures observed by ceilometers are frequently used to derive mixing-layer height (MLH) which is an essential variable for air quality modelling. However, Doppler wind lidar measurements of vertical velocity can provide a more direct estimation of MLH via simple thresholding. A case study reveals difficulties in the aerosol-based MLH retrieval during transition times when the mixing layer builds up in the morning and when turbulence decays in the afternoon. The difficulties can be explained by the fact that the aerosol distribution is related to the history of the mixing process and aerosol characteristics are modified by humidification. The results of the case study are generalized by evaluating one year of joint measurements by a Vaisala CT25K and a HALO Photonics Streamline wind lidar. On average the aerosol-based retrieval gives higher MLH than the wind lidar with an overestimation of MLH by about 300 m (600 m) in the morning (late afternoon). Also, the daily aerosol-based maximum MLH is larger and occurs later during the day and the average morning growth rates are smaller than those derived from the vertical wind. In fair weather conditions classified by less than 4 octa cloud cover the mean diurnal cycle of cloud base height corresponds well to the mixing-layer height showing potential for a simplified MLH estimation.

Comparison of mixing layer height inversion algorithms using lidar and a pollution case study in Baoding, China

2019 ◽  
Vol 79 ◽  
pp. 81-90 ◽  
Author(s):  
Xiangguang Ji ◽  
Cheng Liu ◽  
Zhouqing Xie ◽  
Qihou Hu ◽  
Yunsheng Dong ◽  
...  
Keyword(s):  
Mixing Layer ◽  
Layer Height ◽  
Mixing Layer Height

scholarly journals Impact of spaceborne carbon monoxide observations from the S-5P platform on tropospheric composition analyses and forecasts

2017 ◽  
Vol 17 (2) ◽  
pp. 1081-1103 ◽  
Author(s):  
Rachid Abida ◽  
Jean-Luc Attié ◽  
Laaziz El Amraoui ◽  
Philippe Ricaud ◽  
William Lahoz ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Forest Fires ◽  
Weather Conditions ◽  
Emission Sources ◽  
Simulation Experiments ◽  
Northern Summer ◽  
Free Model ◽  
Comparison Of The Results ◽  
The Impact ◽  
Total Column

Abstract. We use the technique of Observing System Simulation Experiments (OSSEs) to quantify the impact of spaceborne carbon monoxide (CO) total column observations from the Sentinel-5 Precursor (S-5P) platform on tropospheric analyses and forecasts. We focus on Europe for the period of northern summer 2003, when there was a severe heat wave episode associated with extremely hot and dry weather conditions. We describe different elements of the OSSE: (i) the nature run (NR), i.e., the truth; (ii) the CO synthetic observations; (iii) the assimilation run (AR), where we assimilate the observations of interest; (iv) the control run (CR), in this study a free model run without assimilation; and (v) efforts to establish the fidelity of the OSSE results. Comparison of the results from AR and the CR, against the NR, shows that CO total column observations from S-5P provide a significant benefit (at the 99 % confidence level) at the surface, with the largest benefit occurring over land in regions far away from emission sources. Furthermore, the S-5P CO total column observations are able to capture phenomena such as the forest fires that occurred in Portugal during northern summer 2003. These results provide evidence of the benefit of S-5P observations for monitoring processes contributing to atmospheric pollution.

scholarly journals Spatio-Temporal Visualisation of Reflections from Building Integrated Photovoltaics

2018 ◽  
Author(s):  
Roland Schregle ◽  
Christian Renken ◽  
Stephen Wittkopf
Keyword(s):  
Reference Material ◽  
Distribution Functions ◽  
High Temporal Resolution ◽  
Complex Data ◽  
3 Dimensional ◽  
Building Integrated Photovoltaics ◽  
Computational Workflow ◽  
Spatio Temporal ◽  
The Impact

With the increasing adoption of building integrated photovoltaics (BIPV), concerns arise about potential glare. While recommended criteria to assess glare exist, it is challenging to apply these in the spatial and temporal domains and communicate the complex data to planning authorities and clients. In this paper we present a new computational workflow using annual daylight simulation, material modelling using bi-directional scattering distribution functions (BSDFs) and image-based postprocessing to obtain 3-dimensional renderings of cumulative annual irradiance and glare duration on the built environment. The annual daylight simulation considers relevant sun positions in high temporal resolution (15-minute timesteps) and measured BSDFs to model different PV materials. The postprocessing includes a relative irradiance visualisation comparing the impact of a proposed PV proportional to a reference material. It also includes a new spatio-temporal workflow to assess the glare duration based on recommended thresholds. We demonstrate this workflow with a case study of a proposed PV roof for a church, assessing the glare potential of two different PV materials. Our visualisations indicate glare durations well below the thresholds with satinated PVs, and in noncritical zones outside observer positions with standard PVs. Thus the proposed PV roof does not cause any disturbing glare.

scholarly journals Spatio-Temporal Visualisation of Reflections from Building Integrated Photovoltaics

2018 ◽  
Author(s):  
Roland Schregle ◽  
Christian Renken ◽  
Stephen Wittkopf
Keyword(s):  
Reference Material ◽  
Distribution Functions ◽  
High Temporal Resolution ◽  
Complex Data ◽  
3 Dimensional ◽  
Building Integrated Photovoltaics ◽  
Computational Workflow ◽  
Spatio Temporal ◽  
The Impact

With the increasing adoption of building integrated photovoltaics (BIPV), concerns arise about potential glare. While recommended criteria to assess glare exist, it is challenging to apply these in the spatial and temporal domains and communicate the complex data to planning authorities and clients. This paper presents a new computational workflow using annual daylight simulation, material modelling using bi-directional scattering distribution functions (BSDFs) and image-based postprocessing to obtain 3-dimensional renderings of cumulative annual irradiance and glare duration on the built environment. The annual daylight simulation considers relevant sun positions in high temporal resolution (15-minute timesteps) and measured BSDFs to model different PV materials. The postprocessing includes a relative irradiance visualisation comparing the impact of a proposed PV proportional to a reference material. It also includes a new spatio-temporal workflow to assess the glare duration based on recommended thresholds. This workflow is demonstrated with a case study of a proposed PV roof for a church, assessing the glare potential of two different PV materials. The visualisations indicate glare durations well below the thresholds with satinated PVs, and in noncritical zones outside observer positions with standard PVs. Thus the proposed PV roof does not cause any disturbing glare.

scholarly journals Parasite invasion following host reintroduction: a case study of Yellowstone's wolves

2012 ◽  
Vol 367 (1604) ◽  
pp. 2840-2851 ◽  
Author(s):  
Emily S. Almberg ◽  
Paul C. Cross ◽  
Andrew P. Dobson ◽  
Douglas W. Smith ◽  
Peter J. Hudson
Keyword(s):  
Good Health ◽  
Sarcoptes Scabiei ◽  
High Morbidity ◽  
Resource Quality ◽  
Parasite Invasion ◽  
Spatio Temporal ◽  
Canid Species ◽  
The Impact ◽  
Better Than

Wildlife reintroductions select or treat individuals for good health with the expectation that these individuals will fare better than infected animals. However, these individuals, new to their environment, may also be particularly susceptible to circulating infections and this may result in high morbidity and mortality, potentially jeopardizing the goals of recovery. Here, using the reintroduction of the grey wolf ( Canis lupus ) into Yellowstone National Park as a case study, we address the question of how parasites invade a reintroduced population and consider the impact of these invasions on population performance. We find that several viral parasites rapidly invaded the population inside the park, likely via spillover from resident canid species, and we contrast these with the slower invasion of sarcoptic mange, caused by the mite Sarcoptes scabiei . The spatio-temporal patterns of mange invasion were largely consistent with patterns of host connectivity and density, and we demonstrate that the area of highest resource quality, supporting the greatest density of wolves, is also the region that appears most susceptible to repeated disease invasion and parasite-induced declines. The success of wolf reintroduction appears not to have been jeopardized by infectious disease, but now shows signs of regulation or limitation modulated by parasites.

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