scholarly journals Influence of COVID-19 Lockdown on Aerosol Optical Depth over Pokhara and Kyanjin Gompa in Nepal

2021 ◽  
Author(s):  
Ashok Silwal ◽  
Sujan Prasad Gautam ◽  
Monika Karki ◽  
Prakash Poudel ◽  
Arati Thapa ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Pollution Control ◽  
Research Work ◽  
Precipitable Water ◽  
Temporal Fluctuation ◽  
The Past ◽  
Global Emission ◽  
Time Period ◽  
Theoretical Assumptions

Abstract The outbreak of the COVID-19 pandemic and the subsequent global economic shutdown provided an opportunity to conduct a real-time experiment assessing the influence of global emission reductions in the Aerosol Optical Depth (AOD) level, an indicator of air pollution over Nepal. Nepal's government imposed a lockdown on the country for approximately three months (from 24 March onwards) in 2020. The purpose of this study is to examine the temporal fluctuation in Aerosol Optical Depth (AOD) caused by the COVID-19 shutdown by comparing its value during the same time period of the past year over two sites: Pokhara and Kyanjin Gompa. We comparatively analyzed the variation of diurnal mean and monthly average AOD of two selected sites, from the month of January to May 2020 and January to May 2018. By examining the time-series graph of daily average AOD prior to and during the lockdown period, our study showed an apparent fluctuation in AOD throughout the studied areas. The major findings of the research revealed that after the lockdown, a significant variation in monthly averaged AOD was observed, ranging from 20–60% deviation over Pokhara and 25–50% deviation in Kyanjin Gompa at different wavelengths. This confirms previous studies on aerosols and other particulate matter during COVID-19 lockdown, as well as theoretical assumptions. In addition, we performed the heatmap correlation analysis among AOD, Total precipitable water (Tpw), Angstrom exponent (α), Turbidity coefficient (β), and Visibility (V) during the studied period with possible explanations. We believe this research work serves as a crucial reference for our government to implement appropriate policies for pollution control over the studied areas in the future.

Validation of satellite and model aerosol optical depth and precipitable water vapour observations with AERONET data over Pune, India

2018 ◽  
Vol 39 (21) ◽  
pp. 7643-7663 ◽  
Author(s):  
K. Vijayakumar ◽  
P. C. S. Devara ◽  
David M. Giles ◽  
Brent N. Holben ◽  
S. Vijaya Bhaskara Rao ◽  
...  
Keyword(s):  
Water Vapour ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Precipitable Water ◽  
Precipitable Water Vapour ◽  
Model Aerosol

scholarly journals Effect of Urban Growth on Aerosol Optical Depth—Tucson, Arizona, 35 Years Later

2014 ◽  
Vol 53 (8) ◽  
pp. 1876-1885 ◽  
Author(s):  
Gouri Prabhakar ◽  
Eric A. Betterton ◽  
W. Conant ◽  
Benjamin M. Herman
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Urban Growth ◽  
Solar Irradiance ◽  
Monthly Variation ◽  
The Past ◽  
Ozone Column

AbstractMultiwavelength solar irradiance measurements between 400 and 900 nm were made on cloudless days in Tucson, Arizona, over a 30-month period between March 2010 and August 2012. They were analyzed to simultaneously retrieve aerosol optical depth (AOD) and ozone column abundance and to examine their monthly variation. These retrievals were compared with results from a similar study done at the same location between 1975 and 1977. The near tripling of population in Tucson over the past 35 years may have contributed to a 19% increase in the AOD, and the annual-mean ozone column abundance was found to be 11% lower than that inferred during the mid-1970s.

scholarly journals Study of Linke Turbidity Factor over Bode, Bhaktapur

2020 ◽  
Vol 6 (2) ◽  
pp. 66-73
Author(s):  
P. M. Shrestha ◽  
N. P. Chapagain ◽  
I. B. Karki ◽  
K. N. Poudyal
Keyword(s):  
Sea Level ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Meteorological Parameters ◽  
Research Work ◽  
Solar Insolation ◽  
Annual Average ◽  
Atmospheric Turbidity ◽  
Linke Turbidity Factor ◽  
One Year

The daily aerosol optical depth (AOD) data are derived from AERONET over Bode, Bhaktapur (27.68° N, 85.39° E, 1297 m above sea level) for a period of one year 2013. Annual mean of Atmospheric turbidity factors are calculated. The effect of different physical as well as meteorological parameters on the Linke turbidity factor was analyzed. The yearly mean of solar insolation, Angstrom exponential (α),Angstrom coefficient of turbidity (β) and Linke turbidity (LT) were found 4.70 ± 1.10kWh/m2/day, 1.13 ± 0.21 ,0.18 ± 0.14 and 5.70 ± 2.46 respectively. Annual average of visibility is 2.98 ± 2.13 km. Result of this research work is beneficial for the further identification, impact and analysis of atmospheric turbidity at different places.

scholarly journals A 30-year climatology (1990-2020) of aerosol optical depth and total column water vapor and ozone over Texas

2021 ◽  
pp. 1-22
Author(s):  
Forrest M. Mims
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Precipitable Water ◽  
Texas History ◽  
Total Column Ozone ◽  
Annual Cycles ◽  
Total Column

AbstractA 30-year time series (4 Feb 1990 to 4 Feb 2020) of aerosol optical depth of the atmosphere (AOD), total precipitable water (TPW) and total column ozone has been conducted in Central Texas using simple, highly stable instruments. All three parameters in this ongoing measurement series exhibited robust annual cycles. They also responded to many atmospheric events, including the historic volcanic eruption of Mount Pinatubo (1991), a record El Niño (1998), an unprecedented biomass smoke event (1998) and the La Niña that caused the driest drought in recorded Texas history (2011). Reduced air pollution caused mean AOD to decline from 0.175 to 0.14. The AOD trend measured for 30 years by an LED sun photometer, the first of its kind, parallels the trend from 20 years of measurements by a modified Microtops II. While TPW responded to El Niño-Southern Oscillation conditions, TPW exhibited no trend over the 30 years. The TPW data compare favorably with 4.5 years of simultaneous measurements by a nearby NOAA GPS (r2 = 0.78). The 30 years of ozone measurements compare favorably with those from a series of NASA ozone satellites (r2 = 0.78). In 2016, 194 comparisons of Microtops II and world standard ozone instrument Dobson 83 at the Mauna Loa Observatory agreed within 1.9% (r2 = 0.81). The paper concludes by observing that students and citizen scientists can collect scientifically useful atmospheric data with simple sun photometers that use one or more LEDs as spectrally selective photodiodes.

scholarly journals Aerosol radiative forcings induced by substantial changes in anthropogenic emissions in China from 2008 to 2016

2021 ◽  
Vol 21 (8) ◽  
pp. 5965-5982
Author(s):  
Mingxu Liu ◽  
Hitoshi Matsui
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Radiative Forcing ◽  
Eastern China ◽  
Radiation Budget ◽  
Anthropogenic Emissions ◽  
Radiative Forcings ◽  
The Past ◽  
Positive Direct ◽  
Aerosol Radiative

Abstract. Anthropogenic emissions in China play an important role in altering the global radiation budget. Over the past decade, the strong clean-air policies in China have resulted in substantial reductions of anthropogenic emissions of sulfur dioxide (SO2) and primary particulate matter, and air quality in China has consequently improved. However, the resultant aerosol radiative forcings have been poorly understood. In this study, we used an advanced global climate model integrated with the latest localized emission inventory to quantify the aerosol radiative forcings by the changes of anthropogenic emissions in China between 2008 and 2016. By comparing with multiple observation datasets, our simulations reproduced the considerable reductions of sulfate and black carbon (BC) mass loadings reasonably well over eastern China (the key region subject to stringent emission controls) during the period and accordingly showed a clear decline in both aerosol optical depth and absorption aerosol optical depth. The results revealed a regional annual mean positive direct radiative forcing (DRF) of +0.29 W m−2 at the top of the atmosphere (TOA) due to the reduction of SO2 emissions. This positive aerosol radiative forcing was comprised of diminished sulfate scattering (+0.58 W m−2), enhanced nitrate radiative effects (−0.29 W m−2), and could be completely offset by the concurrent reduction of BC emissions that induced a negative BC DRF of −0.33 W m−2. Despite the small net aerosol DRF (−0.05 W m−2) at the TOA, aerosol–radiation interactions could explain the surface brightening in China over the past decade. The overall reductions in aerosol burdens and associated optical effects mainly from BC and sulfate enhanced the regional annual mean downward solar radiation flux at the surface by +1.0 W m−2 between 2008 and 2016. The enhancement was in general agreement with a long-term observational record of surface energy fluxes in China. We also estimated that aerosol effects on cloud radiative forcings may have played a dominant role in the net aerosol radiative forcings at the TOA in China and over the northern Pacific Ocean during the study period. This study will facilitate more informed assessment of climate responses to projected emissions in the future as well as to sudden changes in human activities (e.g., the COVID-19 lockdown).

scholarly journals Ship borne rotating shadow band radiometer observations for the determination of multi spectral irradiance components and direct sun products for aerosol

2016 ◽  
Author(s):  
Jonas Witthuhn ◽  
Hartwig Deneke ◽  
Andreas Macke ◽  
Germar Bernhard
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Precipitable Water ◽  
Gas Absorption ◽  
Spectral Irradiance ◽  
Total Uncertainty ◽  
Direct Beam ◽  
Sun Photometer ◽  
Beam Transmittance ◽  
Band Radiometer

Abstract. The 19 channel rotating shadow band radiometer GUVis-3511 built by Biospherical Instruments is introduced as an instrument which is able to provide automated ship borne measurements of the direct, diffuse and global spectral irradiance components without a requirement for stabilization. Several direct sun products, including spectral direct beam transmittance, aerosol optical depth, Angström exponent, and precipitable water can be derived from these observations. The individual steps of the data analysis are described, and the different sources of uncertainty are discussed. The total uncertainty of the observed direct beam transmittances is estimated to be 4.24 % at 95 % CI for ship borne operation. The calibration is identified as the dominating contribution to the total uncertainty. A comparison of direct beam transmittance with those obtained from a Cimel sun photometer at a land site and a manually operated Microtops II sun photometer on a ship is presented, yielding relative deviations of less than 3 % and 4 % on land and on ship, respectively, for most channels and in agreement with our previous uncertainty estimate. These numbers demonstrate that the instrument is well suited for ship borne operation, and the applied methods for motion correction work accurately. Based on spectral direct beam transmittance, aerosol optical depth at 510 nm can be retrieved with an uncertainty of 0.0032 for a 95 % CI. Only minor deviations occur due to the different methods used for estimating Rayleigh scattering and gas absorption optical depths, as implemented by AERONET and in our processing. Relying on the cross-calibration of the 940 nm water vapor channel with the Cimel sun photometer, the column amount of precipitable water has been estimated with an uncertainty of +−0.034 cm. More research is needed to estimate the accuracy of the instrument for low sun (solar zenith angles larger than 70°) and during periods with strong swell.

scholarly journals Trends of Aerosol Optical Properties over the Heavy Industrial Zone of Northeastern Asia in the Past Decade (2004–15)

2018 ◽  
Vol 75 (6) ◽  
pp. 1741-1754 ◽  
Author(s):  
Dandan Zhao ◽  
Jinyuan Xin ◽  
Chongshui Gong ◽  
Xin Wang ◽  
Yongjing Ma ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Radiative Forcing ◽  
Source Area ◽  
Industrial Zone ◽  
Anthropogenic Aerosols ◽  
Northeastern Asia ◽  
Air Masses ◽  
The Past ◽  
Aerosol Emission

The heavy industrial zone of northeastern Asia is dominated by year-round industrial scattering aerosols that undergo hygroscopic growth in summer. With the rapid economic development over the past decade, aerosol optical depth (AOD) has increased (6.35% yr−1) with an annual-mean AOD of 0.61 ± 0.13. Simultaneously, the aerosol particle size and aerosol scattering have increased, with an annual-mean scattering aerosol optical depth (SAOD) reaching 0.58 ± 0.15. However, considering that the annual AOD/gross domestic product (GDP) per capita decreased, the environmental degradation caused by aerosol emission is expected to reach a turning point based on the environmental Kuznets curve (EKC) hypothesis. In addition, annual-mean radiative forcing at the top, bottom, and interior of the atmospheric column reached −2.35 ± 2.33, −54.16 ± 7.26, and 51.81 ± 7.93 W m−2, respectively. The increase in unit SAOD contributes to the growth in net negative top-of-atmosphere (TOA) forcing and surface (SFC) forcing, and unit absorption aerosol optical depth (AAOD) increases together with atmosphere (ATM) forcing. Moreover, the cooling effect of aerosols on the Earth–atmosphere system showed an increase over the most recent 10 years related to the increase in scattering aerosol from development in the old industrial base. Except for local sources, under the western air masses, the circum–Bohai Sea economic zone was the potential source area of anthropogenic aerosols throughout the year with annual daily mean AOD, single-scattering albedo (SSA), TOA forcing, and SFC forcing values of 0.88, 0.93, −8.08, and −63.05 W m−2, respectively. The Mongolian Plateau was the potential natural dust source area under the northeastern air masses.

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