Analysis of the Haze Weather Process in the East of China from January 21 to 28, 2021

Haze is a pollution weather phenomenon that has been widely concerned by people in recent years. It has a significant impact on people’s production, life, and health. This study focuses on large-scale haze weather that happened in eastern China in late January 2021. The research uses multi-party data and synoptic analysis methods to analyze the occurrence, evolution, and end of the haze weather. The polar vortex, the change of the atmospheric circulation, the change of the cold air force, the temperature and humidity, and the rain and snow weather are the important reasons for this weathering process. It can be used for reference in future research on haze weather.

Intraseasonal variation and future projection of atmospheric diffusion conditions conducive to extreme haze formation over eastern China

Future projection of diffusion conditions associated with extreme haze events over eastern China is of great importance to government emission regulations and public human health.Here,the diffusion conditions and their changes under future warming scenarios are examined.The relative strength of haze events in the Northern China Plain region increase from 150%during 2006–15 to 190%during 2090–99 under RCP8.5 scenarios,induced by a stronger and longer-lasting anticyclone anomaly in eastern China.The strengthened anticyclone anomaly is mainly induced by increased northern wave train convergence emanating from the Barents–Kara Sea,and the longer duration of the anticyclone anomaly is mainly induced by stronger local feedback that can extract more energy from the basic state to maintain the anticyclone anomaly in eastern China.Aerosol reduction is found to play a dominant role in strengthening the upstream wave train near the Barents–Kara Sea and the downstream anticyclone in eastern China,while the effects from increased greenhouse gases are small.The results of this study indicate that future aerosol emissions reduction can induce deteriorating diffusion conditions,suggesting more stringent regulations on aerosol emissions in China are needed to meet air quality standards.

The Lifetime of Diffusion Processes with Application to Conditioned Diffusions

Let τ_D denote the lifetime of a diffusion process on domain DR^d. This paper presents a sufficient condition for the exponential moment of τ_D to be finite. Here, both of the domain and the diffusion operator are general. As an application, the main result of Gao(1995) for conditioned diffusions is improved on.

DIFFUSION PROCESSES ON COMPLETE RIEMANNIAN MANIFOLDS

In this paper,a basic estimate for the conditional Riemannian Brownian motion on a complete manifold with non-negative Ricci curvature is established.Applying it to the heat kernel estimate of the operator 1/2△+b,we obtain the Aronson′s estimate for the operator 1/2△+b,which can be regarded as an extension of Peter Li and S.T.Yau's heat kernel estimate for the Laplace-Beltrami operator.

Analysis on the impact of two winter precipitation episodes on PM_(2.5) in Beijing

In this paper,the circulation background,the characteristics of meteorological elements configuration in the boundary layer and the stable meteorological conditions in two precipitation episodes(during February 19-21,2015 and February 10-13,2016,respectively)within the Beijing-Tianjin-Hebei region are compared and analyzed.Data from conventional meteorological observations,air quality monitoring,reanalysis and numerical models are used.The results show that before the two precipitation processes in 2015 and 2016,the circulations in the middle and high latitudes of Asia and Europe demonstrate“two troughs and one ridge”.Besides,the weather is stable and the pollutant concentration is relatively high.During the precipitation,the circulation is relatively stable for the episode in 2015,and no obvious change in the synoptic system is observed.However,during the episode in 2016,the formation of blocking high and the enhancement of the average ridge in western Asia cause obvious change in the circulation.The simulation results show that significant removal can be detected in both cases,and the PM_(2.5) wet deposition fluxes are 647 g/ha and 486 g/ha,respectively,with the removal in 2015 slightly stronger than that in 2016.The removal and dissipation of pollutants is determined by the atmospheric diffusion conditions and the precipitation,especially in the former episode.In the case of February 2016,good diffusion conditions and the precipitation demonstrate obvious PM_(2.5) removal effect.In the case of February 2015,the longstanding calm wind with high humidity and the physical quantity configuration in the lower mixed layer lead to the poor pollutant removal.