English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The mixing layer is an important meteorological factor that affectsair pollution. In this study, the atmospheric mixing layerheight (MLH) was observed in Beijing from July 2009 to December 2012using a ceilometer. By comparison with radiosonde data,we found that the ceilometer underestimates the MLH under conditions ofneutral stratification caused by strong winds, whereas itoverestimates the MLH when sand-dust is crossing. Usingmeteorological, PM<sub>2.5</sub>, and PM<sub>10</sub> observationaldata, we screened the observed MLH automatically;the ceilometer observations were fairly consistent with theradiosondes, with a correlation coefficient greater than 0.9.Further analysis indicated that the MLH is low in autumnand winter and high in spring and summer in Beijing. There is a significantcorrelation between the sensible heat flux and MLH, and thediurnal cycle of the MLH in summer is also affected by the circulation ofmountainous plain winds. Using visibility as an index to classifythe degree of air pollution, we found that the variation in the sensible heat andbuoyancy term in turbulent kinetic energy (TKE)is insignificant when visibility decreases from 10 to 5 km,but the reduction of shear term in TKE is near 70 %. Whenvisibility decreases from 5 to 1 km, the variation ofthe shear term in TKE is insignificant, but the decrease in thesensible heat and buoyancy term in TKE is approximately 60 %.Although the correlation between the daily variation of the MLH and visibility isvery poor, the correlation between them is significantly enhanced whenthe relative humidity increases beyond 80 %. This indicatesthat humidity-related physicochemical processes is theprimary source of atmospheric particles under heavy pollution andthat the dissipation of atmospheric particles mainly depends on theMLH. The presented results of the atmospheric mixing layerprovide useful empirical information for improving meteorological andatmospheric chemistry models and the forecasting and warning ofair pollution

Mixing layer height and its implications for air pollution over Beijing, China