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

Meteorological conditions within the planetary boundary layer(PBL) are closely governed by large-scale synoptic patterns and playimportant roles in air quality by directly and indirectly affecting theemission, transport, formation, and deposition of air pollutants. Partly dueto the lack of long-term fine-resolution observations of the PBL, therelationships between synoptic patterns, PBL structure, and aerosol pollutionin Beijing have not been well understood. This study applied the obliquelyrotated principal component analysis in T-mode to classify the summertimesynoptic conditions over Beijing using the National Centers for EnvironmentalPrediction reanalysis from 2011 to 2014, and investigated their relationshipswith PBL structure and aerosol pollution by combining numerical simulations,measurements of surface meteorological variables, fine-resolution soundings,the concentration of particles with diameters less than or equal to2.5 µm, total cloud cover (CLD), and reanalysis data. Among theseven identified synoptic patterns, three types accounted for 67 % of thetotal number of cases studied and were associated with heavy aerosolpollution events. These particular synoptic patterns were characterized byhigh-pressure systems located to the east or southeast of Beijing at the925 hPa level, which blocked the air flow seaward, and southerly PBL windsthat brought in polluted air from the southern industrial zone. Thehorizontal transport of pollutants induced by the synoptic forcings may bethe most important factor affecting the air quality of Beijing in summer. Inthe vertical dimension, these three synoptic patterns featured a relativelylow boundary layer height (BLH) in the afternoon, accompanied by high CLD andsoutherly cold advection from the seas within the PBL. The high CLD reducedthe solar radiation reaching the surface, and suppressed the thermalturbulence, leading to lower BLH. Besides, the numerical sensitiveexperiments show that cold advection induced by the large-scale synopticforcing may have cooled the PBL, leading to an increase in near-surfacestability and a decrease in the BLH in the afternoon. Moreover, when warmadvection appeared simultaneously above the top level of the PBL, the thermalinversion layer capping the PBL may have been strengthened, resulting in thefurther suppression of PBL and thus the deterioration of aerosol pollutionlevels. This study has important implications for understanding the crucialroles that meteorological factors (at both synoptic and local scales) play inmodulating and forecasting aerosol pollution in Beijing and its surroundingarea

Classification of summertime synoptic patterns in Beijing and their associations with boundary layer structure affecting aerosol pollution