Seasonal and episodic influence of local meteorology on fine particulate matter at a regional background site in North East India.

2021 ◽  
Author(s):  
Adnan Qadri ◽  
Shahadev Rabha ◽  
Binoy Saikia ◽  
Tarun Gupta
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Ambient Air ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Wind Speeds ◽  
Background Site ◽  
North East ◽  
Regional Background ◽  
Ventilation Coefficient

<p>Climatological parameters like wind speed, temperature, boundary layer height facilitate in dispersion and accumulation of aerosols. Stagnant condition of atmosphere promote accumulation while the pollutants are more likely to get dispersed when non stagnation conditions exist. Sparse studies exist to assess the seasonal and episodic impact of stagnant weather conditions on enhancing aerosol formation in the North-East region of India.PM<sub>2.5 </sub>sampling was carried from January to November 2019 at a regional background site in Jorhat,Assam. Meteorological variables like wind speed, surface ambient temperature and relative humidity were obtained at one-minute resolution from a collocated air weather sensor. Ventilation coefficient was calculated from wind speed and Boundary Layer Height (BLH) ( from ERA5 reanalysis dataset)</p><p>Episodic days were identified as those exceeding permissible values of PM<sub>2.5 </sub>(National Ambient Air Quality Standards) i.e, 60µg/m<sup>3</sup>. Average wind speed on polluted and non-polluted days was 0.58±0.08 and 0.77 ± 0.17 m/s respectively. The average BLH was lower for the polluted days (243±73) than the non-polluted days (316±79). Pearson corelation coefficient of PM<sub>2.5 </sub>and wind speeds on polluted days was low (-0.23) compared to the non-polluted days (-0.54).</p><p>Wind rose plots reveal a seasonality trend with winter and summer winds being mostly between North East and South South-West while in monsoon and autumn it lies predominantly between SSW and South South-East (from the Bay of Bengal).  The Pearson correlation coefficients between PM<sub>2.5 </sub>and wind speeds are -0.66, -0.54 and -0.52 (all p <0.01) in winter, summer and autumn, respectively.Low average BLH persists in Winter and autumn . The seasonal maxima of BLH during winter, summer, monsoon and autumn was 847±167m, 932 ± 271m, 871 ±275m and 814 ± 256m, respectively.  Low night-time BLH (≈ 50m) in winter and autumn contributes to higher aerosol loading. The ventilation coefficient reaches its maxima during daytime around noon with summer season having the maximum daytime VC. High VC (≈270m<sup>2</sup>/s) in summer and monsoon  signify the seasonal effect on the pollutant dispersion and consequent high PM<sub>2.5 </sub>loading. Statistically significant negative correlations were obtained between PM<sub>2.5 </sub>and VC in winter and autumn seasons (-0.75 and -0.43).</p><p>Wind speeds have a strong correlation with PM<sub>2.5 </sub>except for the monsoon season and play a major role in aerosol dispersion.During monsoon, weak dependence of PM<sub>2.5 </sub>with wind speed and ventilation coefficient suggest significance of precipitation  which cause sscavenging of aerosols. Low correlations exist in summer for PM<sub>2.5 </sub>and VC due to possible interference due to regional transport of aerosols. 5-day backward trajectory analysis suggest  transport of air masses across the Thar desert and Indo Gangetic Plains to the site during the March(summer) suggesting transport of dust across the region.</p>

scholarly journals Set of Algorithms and Techniques for Accurate 3D, Single Beam – Single Pointing, Lidar Measurements for Slant Range Visibility, Planetary Boundary Layer Height and Wind Speed Retrieval, Atmospheric Layers Spatial Distribution and Categorization in Real Time

2020 ◽  
Vol 237 ◽  
pp. 02031
Author(s):  
Alexandros Pantazis ◽  
Alexandros Papayannis
Keyword(s):  
Boundary Layer ◽  
Spatial Distribution ◽  
Wind Speed ◽  
Real Time ◽  
Planetary Boundary Layer ◽  
Planetary Boundary Layer Height ◽  
Layer Height ◽  
Single Beam ◽  
Slant Range ◽  
Boundary Layer Height

In this work, a full set of recently developed algorithms and techniques is presented, for a single beam-single pointing lidar to be able to perform operational and independent accurate 3 Dimensional (3D) measurements, for slant range visibility, wind speed retrieval, atmospheric layers spatial distribution and categorization, as well as Planetary Boundary Layer Height (PBLH) retrieval, in real or Near Real Time (NRT).The idea behind this development was for any single lidar to be able to perform a set of accurately measured products, either mobile or stationary, with or without network connectivity with other sensors for data-information exchange. The products were determined by the needs of lidar remote scientific and commercial community, in order to be even more attractive and valuable to atmospheric scientists, meteorologists, aviation and shipping safety operators, as well as to the Space lidar community.

scholarly journals Hurricane Boundary Layer Height Relative to Storm Motion from GPS Dropsonde Composites

Atmosphere ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 339 ◽  
Author(s):  
Yifang Ren ◽  
Jun A. Zhang ◽  
Stephen R. Guimond ◽  
Xiang Wang
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Layer Depth ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Tangential Wind ◽  
Hurricane Boundary Layer ◽  
The Right

This study investigates the asymmetric distribution of hurricane boundary layer height scales in a storm-motion-relative framework using global positioning system (GPS) dropsonde observations. Data from a total of 1916 dropsondes collected within four times the radius of maximum wind speed of 37 named hurricanes over the Atlantic basin from 1998 to 2015 are analyzed in the composite framework. Motion-relative quadrant mean composite analyses show that both the kinematic and thermodynamic boundary layer height scales tend to increase with increasing radius in all four motion-relative quadrants. It is also found that the thermodynamic mixed layer depth and height of maximum tangential wind speed are within the inflow layer in all motion-relative quadrants. The inflow layer depth and height of the maximum tangential wind are both found to be deeper in the two front quadrants, and they are largest in the right-front quadrant. The difference in the thermodynamic mixed layer depth between the front and back quadrants is smaller than that in the kinematic boundary layer height. The thermodynamic mixed layer is shallowest in the right-rear quadrant, which may be due to the cold wake phenomena. The boundary layer height derived using the critical Richardson number ( R i c ) method shows a similar front-back asymmetry as the kinematic boundary layer height.

scholarly journals The “urban meteorology island”: a multi-model ensemble analysis

2020 ◽  
Vol 20 (23) ◽  
pp. 15061-15077
Author(s):  
Jan Karlický ◽  
Peter Huszár ◽  
Tereza Nováková ◽  
Michal Belda ◽  
Filip Švábik ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Regional Climate Model ◽  
Cloud Cover ◽  
Climate Model ◽  
Regional Climate ◽  
Meteorological Variables ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Induced Changes

Abstract. Cities and urban areas are well-known for their impact on meteorological variables and thereby modification of the local climate. Our study aims to generalize the urban-induced changes in specific meteorological variables by introducing a single phenomenon – the urban meteorology island (UMI). A wide ensemble of 24 model simulations with the Weather Research and Forecasting (WRF) regional climate model and the Regional Climate Model (RegCM) on a European domain with 9 km horizontal resolution were performed to investigate various urban-induced modifications as individual components of the UMI. The results show that such an approach is meaningful, because in nearly all meteorological variables considered, statistically significant changes occur in cities. Besides previously documented urban-induced changes in temperature, wind speed and boundary-layer height, the study is also focused on changes in cloud cover, precipitation and humidity. An increase in cloud cover in cities, together with a higher amount of sub-grid-scale precipitation, is detected on summer afternoons. Specific humidity is significantly lower in cities. Further, the study shows that different models and parameterizations can have a strong impact on discussed components of the UMI. Multi-layer urban schemes with anthropogenic heat considered increase winter temperatures by more than 2 ∘C and reduce wind speed more strongly than other urban models. The selection of the planetary-boundary-layer scheme also influences the urban wind speed reduction, as well as the boundary-layer height, to the greatest extent. Finally, urban changes in cloud cover and precipitation are mostly sensitive to the parameterization of convection.

scholarly journals Seasonal Variability in the Diurnal Evolution of the Boundary Layer in a Near-Coastal Urban Environment

2012 ◽  
Vol 29 (5) ◽  
pp. 697-710 ◽  
Author(s):  
Christine L. Haman ◽  
Barry Lefer ◽  
Gary A. Morris
Keyword(s):  
Boundary Layer ◽  
Surface Layer ◽  
Vertical Profiles ◽  
High Wind ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Wind Speeds ◽  
Early Evening ◽  
Stable Surface Layer

Abstract Boundary layer height is estimated during a 21-month period in Houston, Texas, using continuous ceilometer observations and the minimum-gradient method. A comparison with over 60 radiosondes indicates overall agreement between ceilometer- and radiosonde-estimated PBL and residual layer heights. Additionally, the ceilometer-estimated PBL heights agree well with 31 vertical profiles of ozone. Difficulty detecting the PBL height occurs immediately following a frontal system with precipitation, during periods with high wind speeds, and in the early evening when convection is weakening, a new stable surface layer is forming, and the lofted aerosols detected by the lidar do not represent the PBL. Long-term diurnal observations of the PBL height indicate nocturnal PBL heights range from approximately 100 to 300 m throughout the year, while the convective PBL displays more seasonal and daily variability typically ranging from 1100 m in the winter to 2000 m in the summer.

scholarly journals Tracking atmospheric boundary layer in tehran using combined lidar remote sensing and ground base measurements

2018 ◽  
Vol 176 ◽  
pp. 06011 ◽  
Author(s):  
Hossein Panahifar ◽  
Hamid Khalesifard
Keyword(s):  
Remote Sensing ◽  
Boundary Layer ◽  
Air Pollution ◽  
Wind Speed ◽  
Atmospheric Boundary Layer ◽  
Vertical Structure ◽  
Temperature Inversion ◽  
Meteorological Model ◽  
Layer Height ◽  
Boundary Layer Height

The vertical structure of the atmospheric boundary layer (ABL) has been studied by use of a depolarized LiDAR over Tehran, Iran. The boundary layer height (BLH) remains under 1km, and its retrieval from LiDAR have been compared with sonding measurements and meteorological model outputs. It is also shown that the wind speed and direction as well as topography lead to the persistence of air pollution in Tehran. The situation aggravate in fall and winter due to temperature inversion.

scholarly journals The `urban meteorology island': a multi-model ensemble analysis

2020 ◽  
Author(s):  
Jan Karlický ◽  
Peter Huszár ◽  
Tereza Nováková ◽  
Michal Belda ◽  
Filip Švábik ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Cloud Cover ◽  
Anthropogenic Heat ◽  
Specific Humidity ◽  
Meteorological Variables ◽  
Urban Meteorology ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Induced Changes

Abstract. Cities and urban areas are well-known for their impact on meteorological variables and thereby modification of the local climate. Our study aims to generalize the urban-induced changes of specific meteorological variables by introducing a single phenomenon – the urban meteorology island (UMI). A wide ensemble of 24 model simulations with the WRF and RegCM regional climate models on European domain was performed to investigate various urban-induced modifications as individual components of the UMI. The results show that such an approach is meaningful, because nearly in all meteorological variables considered, statistically significant changes occur in cities. Besides previously documented urban-induced changes of temperature, wind speed and boundary-layer height, the study is focused also on changes of cloud cover, precipitation and humidity. An increase of cloud cover in cities, together with a higher amount of sub-grid scale precipitation is detected in summer afternoons. Specific humidity is significantly lower in cities. Further, the study shows that different models and parameterizations can have a strong impact on discussed components of UMI. Multi-layer urban scheme with anthropogenic heat considered increases winter temperatures by more than 2 °C and reduces wind speed more strongly than other urban models. Also the selection of planetary boundary-layer scheme influences the urban wind speed reduction, as well as boundary-layer height with the greatest extent. Finally, urban changes in cloud cover and precipitation are mostly sensitive to the parameterization of convection.

scholarly journals Pollutant Concentration Changes During the COVID-19 Lockdown in Barcelona and Surrounding Regions: Modification of Diurnal Cycles and Limited Role of Meteorological Conditions

2021 ◽  
Author(s):  
Miguel García-Dalmau ◽  
Mireia Udina ◽  
Joan Bech ◽  
Yolanda Sola ◽  
Joan Montolio ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Quality ◽  
Wind Speed ◽  
Road Traffic ◽  
Regional Scale ◽  
Meteorological Conditions ◽  
Surrounding Area ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Concentration Changes

AbstractOne of the consequences of the COVID-19 lockdowns has been the modification of the air quality in many cities around the world. This study focuses on the variations in pollutant concentrations and how important meteorological conditions were for those variations in Barcelona and the surrounding area during the 2020 lockdown. Boundary-layer height, wind speed, and precipitation were compared between mid-March and April 2016–2019 (pre-lockdown) and the same period in 2020 (during lockdown). The results show the limited influence of meteorological factors on horizontal and vertical dispersion conditions. Compared with the pre-lockdown period, during lockdown the boundary-layer height slightly increased by between 5% and 9%, mean wind speed was very similar, and the fraction of days with rainfall increased only marginally, from 0.33 to 0.34, even though April 2020 was extremely wet in the study area. Variations in nitrogen dioxide ($$\hbox {NO}_{{2}}$$ NO 2 ), particulate matter with a diameter less than 10 $${\mu }$$ μ m (PM10), and ozone ($$\hbox {O}_{{3}}$$ O 3 ) concentrations over a 10-year period showed a 66% reduction in $$\hbox {NO}_{{2}}$$ NO 2 , 37% reduction in PM10, and 27% increase in $$\hbox {O}_{{3}}$$ O 3 at a traffic station in Barcelona. The differences in the daily concentration cycle between weekends and weekdays were heavily smoothed for all pollutants considered. The afternoon $$\hbox {NO}_{{2}}$$ NO 2 peak at the traffic station was suppressed compared with the average daily cycle. The analysis of ozone was extended to the regional scale, revealing lower concentrations at rural sites and higher ones in urban zones, especially in Barcelona and the surrounding area. The results presented not only complement previous air quality COVID-19 lockdown studies but also provide insights into the effects of road-traffic reduction.

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