Insights into a historic severe haze event in Shanghai: synoptic situation,
boundary layer and pollutants

Abstract. A historic haze event, characterized by lengthy, large-scale and severe pollution, occurred in the Yangtze River Delta (YRD) of China from 1 to 10 December 2013. This haze event significantly influenced air quality throughout the region, especially in urban areas. Aerosol physical, chemical and optical properties were measured in Shanghai. Sometimes the 1 h average particle concentration (e.g., PM2.5) exceeded 600 µg m−3. Inorganic water-soluble ions in particles, trace gases and aerosol optical coefficients had a similar tendency to increase evidently from clear to hazy episodes. A combination of various factors contributed to the formation and evolution of the haze event, among which meteorological conditions, local anthropogenic emissions and pollutants are the major factors. High pressure system, calm surface wind and subsidence airflow were responsible for the decrease of planetary boundary layer (PBL) and the accumulation of pollutants. Atmospheric visibility correlated strongly with relative humidity (RH), particle number in size of 600–1400 nm other than particulate water-soluble species and particle mass (PM2.5). The particle hygroscopicity plays an important role in atmospheric visibility reduction. The results are somewhat helpful to forecast and eliminate regional atmospheric pollution in China.

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Insights into a historic severe haze weather in Shanghai: synoptic situation, boundary layer and pollutants

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-32561-2015 ◽

2015 ◽

Vol 15 (22) ◽

pp. 32561-32605 ◽

Cited By ~ 5

Author(s):

C. Leng ◽

J. Duan ◽

C. Xu ◽

H. Zhang ◽

Q. Zhang ◽

...

Keyword(s):

Boundary Layer ◽

Urban Areas ◽

Large Scale ◽

Surface Wind ◽

Water Soluble ◽

Synoptic Situation ◽

Pressure System ◽

Small Surface ◽

Atmospheric Visibility ◽

The Yrd

Abstract. A historic winter haze weather, characterized by long duration, large scale and strong pollution intensity, occurred in the Yangtze River Delta (YRD) region of China during the time frame of 1 to 10 December 2013. This severe haze event constituted of several hazy episodes and significantly influenced air quality throughout the region, especially in urban areas. Aerosol physical, chemical and optical properties were measured in Shanghai, where the instantaneous particulate mass burden per volume (e.g. PM2.5) exceeded 600 μg m−3 in some time, breaking the existing historical observation records, and examined to give insights into severe haze weathers. Inorganic water-soluble ions in particles, trace gases and aerosol scattering/absorption coefficients had the same tendency to increase evidently from clear episodes to hazy episodes. A combination of various factors contributed to the formation and evolution of the severe haze, among which meteorological conditions, local anthropogenic emissions and aerosol properties played the major roles. During the haze weather, the YRD region was under the control of a high-pressure system with extremely small surface pressure gradients. The calm surface wind and subsidence airflow were responsible for decreasing planetary boundary layer (PBL) height and constructive to the build-up of air pollutants wandering inside the region, and ultimately induced the haze occurrence. Nonlinear regression analyses indicated that single water-soluble ion did not correlated with the atmospheric visibility degradation so strong, while high ambient relative humidity (RH) indeed exerted a great impact with a correlation coefficient (R2) of 0.41. Moreover, the close relationship was derived between atmospheric visibility and aerosols in size of 600–1400 nm with R2 of 0.70, which further improved to 0.73 when combined aerosol hygroscopicity. This study may provide supports for the public and authorities to recognize severe haze weathers in urban environments, and act as a reference for forecasting and eliminating the occurrences of regional atmospheric pollutions in China.

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How is the marine atmospheric boundary layer turbulence organized in the trades ?

10.5194/egusphere-egu21-12339 ◽

2021 ◽

Author(s):

Pierre-Etienne Brilouet ◽

Marie Lothon ◽

Sandrine Bony

Keyword(s):

Boundary Layer ◽

Atmospheric Boundary Layer ◽

Vertical Velocity ◽

Large Scale ◽

Layer Structure ◽

Potential Temperature ◽

Surface Wind ◽

Cloud Amount ◽

Velocity Spectrum ◽

Marine Atmospheric Boundary Layer

Tradewind clouds can exhibit a wide diversity of mesoscale organizations, and the turbulence of marine atmospheric boundary layer (MABL) can exhibit coherent structures and mesoscale circulations. One of the objectives of the EUREC4A (Elucidating the role of cloud-circulation coupling in climate) field experiment was to better understand the tight interplay between the mesoscale organization of clouds, boundary-layer processes, and the large-scale environment.During the experiment, that took place East of Barbados over the Western Tropical Atlantic Ocean in Jan-Feb 2020, the French ATR-42 research aircraft was devoted to the characterization of the cloud amount and of the subcoud layer structure. During its 17 research flights, it sampled a large diversity of large scale conditions and cloud patterns. Multiple sensors onboard the aircraft measured high-frequency fluctuations of potential temperature, water vapour mixing ratio and wind , allowing for an extensive characterization of the turbulence within the subcloud layer. A quality-controled and calibrated turbulence dataset was produced on the basis of these measurements, which is now available on the EUREC4A AERIS data portal.The MABL turbulent structure is studied using this dataset, through a spectral analysis of the vertical velocity. Vertical profiles of characteristic length scales reveal a non-isotropic structure with a stretching of the eddies along the mean wind. The organization strength of the turbulent field is also explored by defining a diagnostic based on the shape of the vertical velocity spectrum. The structure and the degree of organization of the subcloud layer are characterized for different types of mesoscale convective pattern and as a function of the large-scale environment, including near-surface wind and lower-tropospheric stability conditions.&#160;

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Impact of the current feedback on kinetic energy over the North-East Atlantic from a coupled ocean/atmospheric boundary layer model

10.5194/os-2020-78 ◽

2020 ◽

Author(s):

Théo Brivoal ◽

Guillaume Samson ◽

Hervé Giordani ◽

Romain Bourdallé-Badie ◽

Florian Lemarié ◽

...

Keyword(s):

Boundary Layer ◽

Kinetic Energy ◽

Atmospheric Boundary Layer ◽

Large Scale ◽

Surface Wind ◽

Ocean Model ◽

Ekman Pumping ◽

Coupling Coefficients ◽

Current Feedback ◽

North East

Abstract. A one-dimensional Atmospheric Boundary Layer (ABL1D) is coupled with the NEMO ocean model and implemented over the Iberian–Biscay–Ireland (IBI) area at 1/36° resolution to investigate the retroactions between the surface currents and the atmosphere, namely the Current FeedBack (CFB) in this region of low mesoscale activity. The ABL1D-NEMO coupled model is forced by a large-scale atmospheric reanalysis (ERA-Interim) and integrated over the period 2016–2017. The mechanisms of eddy kinetic energy damping and ocean upper-layers re-energization are realistically simulated, meaning that the CFB is properly represented by the model. In particular, the dynamical coupling coefficients between the curls of surface stress/wind and current are in agreement with the literature. The effects of CFB on the kinetic energy (KE) are then investigated through a KE budget. We show that the KE decrease induced by the CFB is significant down to 1500 m. Near the surface (0–300 m), most of the KE decrease can be explained by a reduction of the surface wind work by 4 %. At depth (300–2000 m), the CFB induce a reduction of the pressure work (i.e: the PE to KE conversion) associated with a reduction of KE which is significant down to 1500 m. We show that this reduction of KE at depth can be explained by CFB-induced Ekman pumping above eddies that weakens the mesoscale activity and this over the whole water column.

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Multiple Regimes of Wind, Stratification, and Turbulence in the Stable Boundary Layer

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-14-0311.1 ◽

2015 ◽

Vol 72 (8) ◽

pp. 3178-3198 ◽

Cited By ~ 38

Author(s):

Adam H. Monahan ◽

Tim Rees ◽

Yanping He ◽

Norman McFarlane

Keyword(s):

Boundary Layer ◽

Wind Speed ◽

Cloud Cover ◽

Large Scale ◽

Potential Temperature ◽

Surface Wind ◽

Geostrophic Wind ◽

Gradient Force ◽

Pressure Gradient Force ◽

Near Surface

Abstract A long time series of temporally high-resolution wind and potential temperature data from the 213-m tower at Cabauw in the Netherlands demonstrates the existence of two distinct regimes of the stably stratified nocturnal boundary layer at this location. Hidden Markov model (HMM) analysis is used to objectively characterize these regimes and classify individual observed states. The first regime is characterized by strongly stable stratification, large wind speed differences between 10 and 200 m, and relatively weak turbulence. The second is associated with near-neutral stratification, weaker wind speed differences between 10 and 200 m, and relatively strong turbulence. In this second regime, the state of the boundary layer is similar to that during the day. The occupation statistics of these regimes are shown to covary with the large-scale pressure gradient force and cloud cover such that the first regime predominates under clear skies with weak geostrophic wind speed and the second regime predominates under conditions of extensive cloud cover or large geostrophic wind speed. These regimes are not distinguished by standard measures of stability, such as the Obukhov length or the bulk Richardson number. Evidence is presented that the mechanism generating these distinct regimes is associated with a previously documented feedback resulting from the existence of an upper limit on the maximum downward heat flux that can be sustained for a given near-surface wind speed.

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High-Resolution Satellite Measurements of the Atmospheric Boundary Layer Response to SST Variations along the Agulhas Return Current

Journal of Climate ◽

10.1175/jcli3415.1 ◽

2005 ◽

Vol 18 (14) ◽

pp. 2706-2723 ◽

Cited By ~ 148

Author(s):

Larry W. O’Neill ◽

Dudley B. Chelton ◽

Steven K. Esbensen ◽

Frank J. Wentz

Keyword(s):

Boundary Layer ◽

Atmospheric Boundary Layer ◽

Wind Stress ◽

Large Scale ◽

Surface Wind ◽

Sensible Heat Flux ◽

Wind Stress Curl ◽

Return Current ◽

Short Scale ◽

Sst Gradient

Abstract The marine atmospheric boundary layer (MABL) response to sea surface temperature (SST) perturbations with wavelengths shorter than 30° longitude by 10° latitude along the Agulhas Return Current (ARC) is described from the first year of SST and cloud liquid water (CLW) measurements from the Advanced Microwave Scanning Radiometer (AMSR) on the Earth Observing System (EOS) Aqua satellite and surface wind stress measurements from the QuikSCAT scatterometer. AMSR measurements of SST at a resolution of 58 km considerably improves upon a previous analysis that used the Reynolds SST analyses, which underestimate the short-scale SST gradient magnitude over the ARC region by more than a factor of 5. The AMSR SST data thus provide the first quantitatively accurate depiction of the SST-induced MABL response along the ARC. Warm (cold) SST perturbations produce positive (negative) wind stress magnitude perturbations, leading to short-scale perturbations in the wind stress curl and divergence fields that are linearly related to the crosswind and downwind components of the SST gradient, respectively. The magnitudes of the curl and divergence responses vary seasonally and spatially with a response nearly twice as strong during the winter than during the summer along a zonal band between 40° and 50°S. These seasonal variations closely correspond to seasonal and spatial variability of large-scale MABL stability and surface sensible heat flux estimated from NCEP reanalysis fields. SST-induced deepening of the MABL over warm water is evident in AMSR measurements of CLW. Typical annual mean differences in cloud thickness between cold and warm SST perturbations are estimated to be about 300 m.

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Impact of upper-level jet-generated inertia-gravity waves on surface wind and precipitation

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-7-15873-2007 ◽

2007 ◽

Vol 7 (6) ◽

pp. 15873-15909 ◽

Cited By ~ 3

Author(s):

C. Zülicke ◽

D. H. W. Peters

Keyword(s):

Baltic Sea ◽

Gravity Waves ◽

Large Scale ◽

Surface Wind ◽

Synoptic Situation ◽

Strong Wind ◽

The Baltic Sea ◽

The Baltic ◽

The Impact ◽

Inertia Gravity Waves

Abstract. A meteorological case study for the impact of inertia-gravity waves on surface meteorology is presented. The large-scale environment from 17 to 19 December 1999 was dominated by a poleward breaking Rossby wave transporting subtropical air over the North Atlantic Ocean upward and north-eastward. The synoptic situation was characterized with an upper tropospheric jet streak passing Northern Europe. The unbalanced jet spontaneously radiated inertia-gravity waves from its exit region. Near-inertial waves appeared with a horizontal wavelength of about 200 km and an apparent period of about 12 h. These waves transported energy downwards and interacted with large-scale convection. This configuration is simulated with the nonhydrostatic Fifth-Generation Mesoscale Model. Together with simplified runs without orography and moisture it is demonstrated that the imbalance of the jet (detected with the cross-stream ageostrophic wind) and the deep convection (quantified with the latent heat release) are forcing inertia-gravity waves. This interaction is especially pronounced when the upper tropospheric jet is located above a cold front at the surface and supports deep frontal convection. Weak indication was found for triggering post-frontal convection by inertia-gravity waves. The realism of model simulations was studied in an extended validation study for the Baltic Sea region. It included observations from radar (DWDPI, BALTRAD), satellite (GFZGPS), weather stations (DWDMI) and assimilated products (ELDAS, MESAN). The detected spatio-temporal patterns show wind pulsations and precipitation events at scales corresponding to those of inertia-gravity waves. In particular, the robust features of strong wind and enhanced precipitation near the front appeared with nearly the same amplitudes as in the model. In some datasets we found indication for periodic variations in the post-frontal region. These findings demonstrate the impact of upper tropospheric jet-generated inertia-gravity waves on the dynamics of the boundary layer. It also gives confidence to models, observations and assimilation products for covering such processes. In an application for the Gotland Basin in the Baltic Sea, the implications of such mesoscale events on air-sea interaction and energy and water budgets are discussed.

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Atmosphere-Ocean Interaction

10.1093/oso/9780195066180.001.0001 ◽

1995 ◽

Cited By ~ 2

Author(s):

Eric B. Kraus ◽

Joost A. Businger

Keyword(s):

Boundary Layer ◽

Large Scale ◽

Wind Waves ◽

Surface Wind ◽

Sea Surface ◽

Physical Oceanography ◽

Turbulent Transfer ◽

Ocean Engineering ◽

State Of Matter ◽

Surface Buoyancy

With both the growing importance of integrating studies of air-sea interaction and the interest in the general problem of global warming, the appearance of the second edition of this popular text is especially welcome. Thoroughly updated and revised, the authors have retained the accessible, comprehensive expository style that distinguished the earlier edition. Topics include the state of matter near the interface, radiation, surface wind waves, turbulent transfer near the interface, the planetary boundary layer, atmospherically-forced perturbations in the oceans, and large-scale forcing by sea surface buoyancy fluxes. This book will be welcomed by students and professionals in meteorology, physical oceanography, physics and ocean engineering.

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Performance of the WRF Model for Surface Wind Prediction around Qatar

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-17-0125.1 ◽

2018 ◽

Vol 35 (3) ◽

pp. 575-592 ◽

Cited By ~ 2

Author(s):

B. S. Sandeepan ◽

V. G. Panchang ◽

S. Nayak ◽

K. Krishna Kumar ◽

J. M. Kaihatu

Keyword(s):

Boundary Layer ◽

Large Scale ◽

Surface Wind ◽

Wrf Model ◽

Wave Model ◽

Sea Breeze ◽

Surface Winds ◽

Model Errors ◽

Sea Breezes ◽

Practical Applications

AbstractThe performance of the Weather Research and Forecasting (WRF) Model is examined for the region around Qatar in the context of surface winds. The wind fields around this peninsula can be complicated owing to its small size, to a complex pattern of land and sea breezes influenced by the prevailing shamal winds, and to its dry and arid nature. Modeled winds are verified with data from 19 land stations and two offshore buoys. A comparison with these data shows that nonlocal planetary boundary layer (PBL) schemes generally perform better than local schemes over land stations during the daytime, when convective conditions prevail; at nighttime, over land and over water, both schemes yield similar results. Among other parameters, modifications to standard USGS land-use descriptors were necessary to reduce model errors. The RMSE values are comparable to those reported elsewhere. Simulated winds, when used with a wave model, result in wave heights comparable to buoy measurements. Furthermore, WRF results, confirmed by data, show that at times sea breezes develop from both coasts, leading to convergence in the middle of the country; at other times, the large-scale wind impedes the formation of sea breezes on one or both coasts. Simulations also indicate greater land/sea-breeze activity in the summer than in the winter. Differences in the diurnal evolution of surface winds over land and water are found to be related to differences in the boundary layer stability. Overall, the results indicate that the WRF Model as configured here yields reliable simulations and can be used for various practical applications.

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Tornado-scale vortices in the tropical cyclone boundary layer: numerical simulation with the WRF–LES framework

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-2477-2019 ◽

2019 ◽

Vol 19 (4) ◽

pp. 2477-2487 ◽

Cited By ~ 4

Author(s):

Liguang Wu ◽

Qingyuan Liu ◽

Yubin Li

Keyword(s):

Boundary Layer ◽

Tropical Cyclone ◽

Large Scale ◽

Surface Wind ◽

Wrf Model ◽

Surface Wind Speed ◽

Horizontal Scale ◽

Lower Altitude ◽

Near Surface ◽

Research Aircraft

Abstract. A tornado-scale vortex in the tropical cyclone (TC) boundary layer (TCBL) has been observed in intense hurricanes and the associated intense turbulence poses a severe threat to the manned research aircraft when it penetrates hurricane eyewalls at a lower altitude. In this study, a numerical experiment in which a TC evolves in a large-scale background over the western North Pacific is conducted using the Advanced Weather Research and Forecast (WRF) model by incorporating the large-eddy simulation (LES) technique. The simulated tornado-scale vortex shows features similar to those revealed with limited observational data, including the updraft–downdraft couplet, the sudden jump of wind speeds, the location along the inner edge of the eyewall, and the small horizontal scale. It is suggested that the WRF–LES framework can successfully simulate the tornado-scale vortex with grids at a resolution of 37 m that cover the TC eye and eyewall. The simulated tornado-scale vortex is a cyclonic circulation with a small horizontal scale of ∼1 km in the TCBL. It is accompanied by strong updrafts (more than 15 m s−1) and large vertical components of relative vorticity (larger than 0.2 s−1). The tornado-scale vortex favorably occurs at the inner edge of the enhanced eyewall convection or rainband within the saturated, high-θe layer, mostly below an altitude of 2 km. In nearly all the simulated tornado-scale vortices, the narrow intense updraft is coupled with the relatively broad downdraft, constituting one or two updraft–downdraft couplets, as observed by the research aircraft. The presence of the tornado-scale vortex also leads to significant gradients in the near-surface wind speed and wind gusts.

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Response of Surface Wind Divergence to Mesoscale SST Anomalies under Different Wind Conditions

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-18-0204.1 ◽

2019 ◽

Vol 76 (7) ◽

pp. 2065-2082 ◽

Cited By ~ 9

Author(s):

A. Foussard ◽

G. Lapeyre ◽

R. Plougonven

Keyword(s):

Boundary Layer ◽

Atmospheric Boundary Layer ◽

Boundary Layers ◽

Wind Stress ◽

Large Scale ◽

Surface Wind ◽

Storm Track ◽

First Case ◽

Weak Winds ◽

Sst Anomalies

Abstract The response of the atmospheric boundary layer to mesoscale sea surface temperature (SST) is often characterized by a link between wind stress divergence and downwind SST gradients. In this study, an idealized simulation representative of a storm track above a prescribed stationary SST field is examined in order to determine in which background wind conditions that relationship occurs. The SST field is composed of a midlatitude large-scale frontal zone and mesoscale SST anomalies. It is shown that the divergence of the surface wind can correlate either with the Laplacian of the atmospheric boundary layer temperature or with the downwind SST gradient. The first case corresponds to background situations of weak winds or of unstable boundary layers, and the response is in agreement with an Ekman balance adjustment in the boundary layer. The second case corresponds to background situations of stable boundary layers, and the response is in agreement with downward mixing of momentum. Concerning the divergence of the wind stress, it generally resembles downwind SST gradients for stable and unstable boundary layers, in agreement with past studies. For weak winds, a correlation with the temperature Laplacian is, however, found to some extent. In conclusion, our study reveals the importance of the large-scale wind conditions in modulating the surface atmospheric response with different responses in the divergences of surface wind and wind stress.

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