Weekly cycle of aerosol‐meteorology interaction over China

Abstract

[1] Weekly cycles of the concentration of anthropogenic aerosols have been observed in many regions around the world. The phase and the magnitude of these cycles, however, vary greatly depending on region and season. In the present study the authors investigated important features of the weekly cycles of aerosol concentration and the covariations in meteorological conditions in major urban regions over east China, one of the most polluted areas in the world, in summertime during the period 2001-2005/2006. The PM10 (aerosol particulate matters of diameter < 10 mm) concentrations at 29 monitoring stations show significant weekly cycles with the largest values around midweek and smallest values in weekend. Accompanying the PM10 cycle, the meteorological variables also show notable and consistent weekly cycles. The wind speed in the lower troposphere is relatively small in the early part of the week and increases after about Wednesday. At the same time, the air temperature anomalies in low levels are positive and then become negative in the later part of the week. The authors hypothesize that the changes in the atmospheric circulation may be triggered by the accumulation of PM10 through diabatic heating of lower troposphere. During the early part of a week the anthropogenic aerosols are gradually accumulated in the lower troposphere. Around midweek, the accumulated aerosols could induce radiative heating, likely destabilizing the middle to lower troposphere and generating anomalously vertical air motion and thus resulting in stronger winds. The resulting circulation could promote ventilation to reduce aerosol concentrations in the boundary layer during the later part of the week. Corresponding to this cycle in anthropogenic aerosols the frequency of precipitation, particularly the light rain events, tends to be suppressed around midweek days through indirect aerosol effects. This is consistent with the observed anthropogenic weather cycles, i.e., more (less) solar radiation near surface, higher (lower) maximum temperature, larger (smaller) diurnal temperature range, and fewer (more) precipitation events in midweek days (weekend).

Change of precipitation intensity spectra at different spatial scales under warming conditions

“…Heavy precipitation usually forms in fastgrowing convective clouds, which are intimately connected with robust moisture rising caused by dynamic convergence, orographic uplifting or surface heating [2][3][4]. In contrast, low-intensity precipitation is more associated with cloud microphysical processes, which are affected by aerosols, moisture content and so on [5][6][7][8].…”

Characterising and visualizing spatio-temporal patterns in hourly precipitation records

“…Strong correlations in daily, monthly, and yearly data can persist over relatively large distances, whereas patterns in distance-decay rates for sub-daily data are normally not as clear. Aghakouchak (2010) noted that occurrence of large amounts of hourly precipitation can exhibit strong spatial dependence for sites up to 10 km apart, whereas other studies have indicated relatively weak dependencies (Serinaldi, 2008;Garcia, 2002;Barbaliscia, 1992).…”

Does it really rain more often on weekends than on weekdays? A case study for Slovenia

“…Higher air pollution may increase the amount of aerosols in the air, which influences the probability of rainfall occurrence (Bell et al 2008). This means that the accumulation of small solid particles (PM 10 ) in the air, which may increase during the weekends, could trigger the changes in the atmospheric circulations that can result in non-uniform weekly rainfall patterns (Gong et al 2007).…”

“…Several studies dealing with this phenomenon have been carried out in recent years (Bell et al 2008;DeLisi et al 2011;Gong et al 2007;Seibert et al 2013;Shultz et al 2007). In most of these studies, data on rainfall and PM 10 particles (particles with a diameter up to 10 µm) were used, and their conclusions depended on the location of the study and the selected data.…”

“…2007;Shultz et al 2007;Bell et al 2008;DeLisi et al 2011;Stjern 2011). The theory is related to anthropogenic influence that became more pronounced over the last century with daily commuting and development of heavy industry (Gong et al 2007;Arts 2008;Bell et al 2008;DeLisi et al 2011;Stjern 2011). Higher air pollution may increase the amount of aerosols in the air, which influences the probability of rainfall occurrence (Bell et al 2008).…”