scholarly journals Ultra-Violet Mie Lidar Observations of Particulates Vertical Profiles in Macao during a Record High Pollution Episode

2021 ◽  
Vol 14 (1) ◽  
pp. 118
Author(s):  
Qiaojun Liu ◽  
Andrew Yuksun Cheng ◽  
Jianhua Zhu ◽  
Sauwa Chang ◽  
Kinseng Tam
Keyword(s):  
Ultra Violet ◽  
Northern China ◽  
High Energy ◽  
Mie Scattering ◽  
Back Trajectory ◽  
Vertical Profiles ◽  
Atmospheric Conditions ◽  
Pearl River Delta Region ◽  
Dust Event ◽  
Back Trajectory Analysis

Vertical profiles of particulates were measured in Macao by using a 355 nm Mie scattering lidar during a dust event. A high energy pulse laser was employed as the light source to detect the extinction coefficient in the atmosphere. The extinction profiles showed layers of high aerosol concentrations in good agreement with both back trajectory analysis and ground-based pollution measurements in Macao, which indicate that this lidar is very useful for monitoring extinction profiles during extreme high aerosol loading and low visibility atmospheric conditions when most low energy lidar system is inefficient. The results evidenced that correlations between PM2.5 and TSP varied with the intensity of dust storm and the PM2.5/PM10 ratio was small during dust episode, which indicated that aerosols were dominated by large particles. Furthermore, results of the dust event showed high aerosol concentrations at altitudes where the wind carried the dusty aerosols from northern China, covering Shanghai and the Taiwan Channel, to the Pearl River Delta Region. This research improved the understanding of the dust properties in Macao.

Aeolus Rayleigh-channel winds in cloudy conditions

2021 ◽  
Author(s):  
Gert-Jan Marseille
Keyword(s):  
Rayleigh Scattering ◽  
Scattered Light ◽  
Weather Prediction ◽  
Ultra Violet ◽  
Mie Scattering ◽  
Atmospheric Conditions ◽  
Atmospheric Flow ◽  
Rayleigh Channel ◽  
Wind Profiles ◽  
Height Assignment

<p>Aeolus was launched in August 2018 and is expected to be operational until 2022. Aeolus is the first Doppler wind lidar in space to measure wind profiles through Rayleigh scattering of an ultra-violet laser beam and the determination of the Doppler shift of the scattered light by molecules along the Line-Of-Sight (LOS). In addition, Mie scattering provides winds on aerosol and cloud particles. The atmosphere return signal is a small bandwidth peak (from Mie scattering) on top of a broadband spectrum (from Rayleigh scattering). The tails and central part of the spectrum are being processed separately to yield so-called Rayleigh channel and Mie channel winds respectively.</p><p>Signals in both channels are being accumulated onboard the satellite to segments of 2.85 km length along the satellite track, denoted measurements. Rayleigh winds are obtained by on-ground processing through accumulating typically 30 measurements to yield a single Rayleigh wind observation of sufficient quality for use in Numerical Weather Prediction (NWP). The vertical resolution of the horizontally projected LOS wind profiles is typically 500 m in the boundary layer, 1 km in the free-troposphere and 1.5-2 km in the stratosphere, but this can and has been changed in a flexible way during the mission.</p><p>In case of clouds and/or aerosols presence within the sensing atmospheric volume, signal from Mie scattering leaks into the Rayleigh channel signal. Since the Rayleigh-channel signal processing assumes a pure molecular signal this so-called Mie contamination causes biases in retrieved winds. This is solved through classifying measurements as either ‘clear’ or ‘cloudy’ before accumulation to observation level. Clear measurements (out of a total of 30) are accumulated to yield a Rayleigh-clear wind. This procedure has proven successful and Aeolus Rayleigh-clear winds are used operationally today by a number of meteorological centers around the world.</p><p>A similar procedure for cloudy measurements is less trivial and requires correction for Mie contamination. So far, implemented corrections were not successful in producing Rayleigh-cloudy winds of sufficient quality for use in NWP. A new correction scheme has been introduced and tested recently and proved successful to produce bias-free winds and a random error slightly larger as compared to Rayleigh-clear winds. The latter is explained by increased heterogeneous atmospheric conditions in which Rayleigh-cloudy winds are obtained. Interestingly, Rayleigh-cloudy and Mie-cloudy winds are obtained for identical atmospheric conditions and as such provide independent information on the atmospheric flow, which allows to characterize the error sources of the different types of wind observations, including instrumental/calibration errors, but also errors due to incorrect height assignment and representativity.</p><p>This paper describes the new scheme to correct Rayleigh winds for Mie contamination and its application to Aeolus data. The results show that resulting Rayleigh-cloudy winds are of good quality to be considered for operational use in NWP.</p>

scholarly journals Radiative Effect and Mixing Processes of a Long-Lasting Dust Event over Athens, Greece, during the COVID-19 Period

Atmosphere ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 318
Author(s):  
Panagiotis Kokkalis ◽  
Ourania Soupiona ◽  
Christina-Anna Papanikolaou ◽  
Romanos Foskinis ◽  
Maria Mylonaki ◽  
...  
Keyword(s):  
Atmospheric Pollutants ◽  
Saharan Dust ◽  
Radiative Effect ◽  
Atmospheric Conditions ◽  
Dust Event ◽  
Mixing Processes ◽  
Hysplit Model ◽  
European Continent ◽  
Dust Layer ◽  
Ground Based Lidar

We report on a long-lasting (10 days) Saharan dust event affecting large sections of South-Eastern Europe by using a synergy of lidar, satellite, in-situ observations and model simulations over Athens, Greece. The dust measurements (11–20 May 2020), performed during the confinement period due to the COVID-19 pandemic, revealed interesting features of the aerosol dust properties in the absence of important air pollution sources over the European continent. During the event, moderate aerosol optical depth (AOD) values (0.3–0.4) were observed inside the dust layer by the ground-based lidar measurements (at 532 nm). Vertical profiles of the lidar ratio and the particle linear depolarization ratio (at 355 nm) showed mean layer values of the order of 47 ± 9 sr and 28 ± 5%, respectively, revealing the coarse non-spherical mode of the probed plume. The values reported here are very close to pure dust measurements performed during dedicated campaigns in the African continent. By utilizing Libradtran simulations for two scenarios (one for typical midlatitude atmospheric conditions and one having reduced atmospheric pollutants due to COVID-19 restrictions, both affected by a free tropospheric dust layer), we revealed negligible differences in terms of radiative effect, of the order of +2.6% (SWBOA, cooling behavior) and +1.9% (LWBOA, heating behavior). Moreover, the net heating rate (HR) at the bottom of the atmosphere (BOA) was equal to +0.156 K/d and equal to +2.543 K/d within 1–6 km due to the presence of the dust layer at that height. On the contrary, the reduction in atmospheric pollutants could lead to a negative HR (−0.036 K/d) at the bottom of the atmosphere (BOA) if dust aerosols were absent, while typical atmospheric conditions are estimated to have an almost zero net HR value (+0.006 K/d). The NMMB-BSC forecast model provided the dust mass concentration over Athens, while the air mass advection from the African to the European continent was simulated by the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model.

AN EMPIRICAL MODEL OF PRODUCTION AND ATTENUATION OF FLUORESCENCE LIGHT IN ATMOSPHERE FOR SATELLITE-BASED ULTRA HIGH ENERGY COSMIC RAY EXPERIMENTS

2011 ◽  
Vol 20 (03) ◽  
pp. 299-317
Author(s):  
E. STRAZZERI ◽  
O. CATALANO ◽  
B. SBARUFATTI
Keyword(s):  
Stratospheric Ozone ◽  
Cosmic Ray ◽  
High Energy ◽  
Fluorescence Yield ◽  
Ultra High Energy ◽  
Atmospheric Conditions ◽  
Atmospheric Transmission ◽  
Emission Point ◽  
Geographical Variations ◽  
Fluorescence Light

In the context of detection of Ultra High Energy Cosmic Ray (UHECR) showers from space the details of fluorescence light production and transmission in the atmosphere are given. An analytical model of the fluorescence yield, in dependence on nitrogen molecular parameters and the atmospheric conditions, is presented. Seasonal and geographical variations of the total fluorescence photon yield between 300 nm and 400 nm in air excited by 0.85 MeV electrons are shown as a function of the altitude, using different atmospheric models. In the frame of a satellite-based UHECR experiment the fluorescence yield has been corrected by the overall atmospheric transmission which takes into account, in the simplest approximation, the wavelength-dependent scattering and absorption of the fluorescence light from air molecules, from stratospheric ozone, and from aerosol. The effect of the atmospheric attenuation on the fluorescence yield is shown as a function of the altitude of the emission point of light.

Assessing the impacts of seasonal and vertical atmospheric conditions on air quality over the Pearl River Delta region

2018 ◽  
Vol 180 ◽  
pp. 69-78 ◽  
Author(s):  
Cheuk Hei Marcus Tong ◽  
Steve Hung Lam Yim ◽  
Daniel Rothenberg ◽  
Chien Wang ◽  
Chuan-Yao Lin ◽  
...  
Keyword(s):  
Air Quality ◽  
Pearl River Delta ◽  
River Delta ◽  
Pearl River ◽  
Atmospheric Conditions ◽  
Pearl River Delta Region ◽  
Delta Region ◽  
The Pearl River Delta ◽  
The Pearl River

scholarly journals Use of Low-Cost Ambient Particulate Sensors in Nablus, Palestine with Application to the Assessment of Regional Dust Storms

Atmosphere ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 539
Author(s):  
Abdelhaleem Khader ◽  
Randal S. Martin
Keyword(s):  
Low Cost ◽  
Dust Storms ◽  
Air Pollutant ◽  
World Health ◽  
Back Trajectory ◽  
Hysplit Model ◽  
Air Masses ◽  
Palestinian Territories ◽  
Back Trajectory Analysis ◽  
Lower Elevation

Few air pollutant studies within the Palestinian territories have been reported in the literature. In March–April and May–June of 2018, three low-cost, locally calibrated particulate monitors (AirU’s) were deployed at different elevations and source areas throughout the city of Nablus in Northern West Bank, Palestine. During each of the three-week periods, high but site-to-site similar particulate matter less than 2.5 µm in aerodynamic diameter (PM2.5) and less than 10 µm (PM10) concentrations were observed. The PM2.5 concentrations at the three sampling locations and during both sampling periods averaged 38.2 ± 3.6 µg/m3, well above the World Health Organization’s (WHO) 24 h guidelines. Likewise, the PM10 concentrations exceeded or were just below the WHO’s 24 h guidelines, averaging 48.5 ± 4.3 µg/m3. During both periods, short episodes were identified in which the particulate levels at all three sites increased substantially (≈2×) above the regional baseline. Air mass back trajectory analyses using U.S. National Oceanic and Atmospheric Administration’s (NOAA) Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model suggested that, during these peak episodes, the arriving air masses spent recent days over desert areas (e.g., the Saharan Desert in North Africa). On days with regionally low PM2.5 concentrations (≈20 µg/m3), back trajectory analysis showed that air masses were directed in from the Mediterranean Sea area. Further, the lower elevation (downtown) site often recorded markedly higher particulate levels than the valley wall sites. This would suggest locally derived particulate sources are significant and may be beneficial in the identification of potential remediation options.

scholarly journals Remote sensing of aerosols by synergy of caliop and modis

2018 ◽  
Vol 176 ◽  
pp. 08012
Author(s):  
Rei Kudo ◽  
Tomoaki Nishizawa ◽  
Akiko Higurashi ◽  
Eiji Oikawa
Keyword(s):  
Remote Sensing ◽  
Biomass Burning ◽  
Sea Salt ◽  
Water Soluble ◽  
Dust Particles ◽  
Vertical Profiles ◽  
Dust Event ◽  
Carbonaceous Particles ◽  
The Individual ◽  
Better Than

For the monitoring of the global 3-D distribution of aerosol components, we developed the method to retrieve the vertical profiles of water-soluble, light absorbing carbonaceous, dust, and sea salt particles by the synergy of CALIOP and MODIS data. The aerosol product from the synergistic method is expected to be better than the individual products of CALIOP and MODIS. We applied the method to the biomass-burning event in Africa and the dust event in West Asia. The reasonable results were obtained; the much amount of the water-soluble and light absorbing carbonaceous particles were estimated in the biomass-burning event, and the dust particles were estimated in the dust event.

Control of a Robotic UV Curing Process With Thermal Vision Feedback Through Two IR Cameras

2009 ◽  
Author(s):  
Fan Zeng ◽  
Beshah Ayalew ◽  
Mohammed Omar
Keyword(s):  
Control Variable ◽  
Ultra Violet ◽  
Uv Curing ◽  
High Energy ◽  
Curing Process ◽  
Radiant Intensity ◽  
Loop Control ◽  
Thermal Vision ◽  
Uv Curing Process ◽  
Vision Feedback

Robotic ultra-violet (UV) curing is considered to be one of the effective ways to replace the current convection-based methods in various manufacturing processes due to its fast curing rate and high energy efficiency. This paper presents a closed-loop control of a robotic UV curing system by using thermal vision feedback through two infrared (IR) cameras. The proposed approach is developed based on a mathematical analysis of the fundamental UV curing process and the integration of the local and global IR cameras in a cascade manner. A computer simulation study is conducted to evaluate the proposed strategy by regarding two control variables: the radiant intensity of the UV heater and the sweeping speed of the robot end effector. The results indicate that controllers using either control variable can compensate for interferences and improve curing quality under this thermal-vision-based architecture.

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