Influence Of Aerosol Concentration Research Articles

Effect of aerosol concentration on post-corona unipolar diffusion charging: Ion density retro-controlled by aerosol space charge versus geometry of ion-aerosol mixing

The influence of aerosol concentration on the charge per particle is investigated in post-DC corona diffusion chargers for particle diameter between 10 nm and 1 µm. Particles are charged as they pa...

THE INFLUENCE OF AEROSOL CONCENTRATION ON CHANGES IN THE VOLUMETRIC ACTIVITIES OF INDOOR RADON SHORT-TERM DECAY PRODUCTS

The article describes the influence of aerosol concentration on changes in the volumetric activities of indoor radon short-term decay products. The concentration of aerosol in the air, equilibrium factors and unattached fraction were measured under normal living conditions when the concentration of aerosol increases, i.e. burning a candle or frankincense in accommodations, smoke-filled accommodations, a steamy kitchen etc. It has been established that when the concentration of aerosol in the air rises, the number of free atoms of radon short-term decay products attached to aerosol particles also increases, and therefore higher volumetric activity of alpha particles is fixed. A tight positive connection of the correlation between equilibrium factor (F) and aerosol particle concentration in the air of accommodations as well as a negative correlation between unattached fraction and an equilibrium factor have been determined.

Impacts of aerosols on the development and precipitation of a mesoscale squall line

The effects of aerosols on the development and precipitation for a mesoscale squall line occurring in the south plains of the United States have been investigated using a cloud‐resolving Weather Research and Forecasting (CR‐WRF) model with a two‐moment bulk microphysical scheme. Different aerosol scenarios are considered in the CR‐WRF model experiments, including polluted continental aerosols with a mean concentration of 2000 cm−3. The simulated temporal evolution of composite radar reflectivity and the 24‐h accumulated precipitation in the polluted aerosol experiment are in agreement with the measurements. The influence of aerosol concentrations is insignificant on the rainfall distribution but is remarkable on the precipitation intensity. The CR‐WRF experiment with the polluted aerosol case predicts about 13% more precipitation and more locally intensive rainfall than do those with the clean aerosol case. Both the convection zone and the storm convective strength are increased in the polluted aerosol experiment in response to the increase in aerosol concentrations. The two‐moment microphysical scheme is compared with three single‐moment bulk schemes in the WRF model, including the Lin, WRF single‐moment six‐class, and Thompson schemes. Only the Thompson schemes reproduce the observed precipitation and radar reflectivity pattern, in agreement with the two‐moment scheme with a leading convective line and a trailing stratiform precipitation regime. All of the single‐moment schemes significantly overestimate the precipitation, especially with the Lin scheme, while the two‐moment scheme yields the precipitation simulation comparable with the measurement.

Influence of aerosol concentration on precipitation formation in low-level, warm stratiform clouds

A one-dimensional model with size-resolved cloud microphysics is used to investigate possible reinforcement or inhibition effects of different concentrations of cloud condensation nuclei (CCN) on precipitation formation in low-level, warm stratiform marine and continental clouds. Precipitation is found to be inhibited due to newly activated droplets when a precipitating marine cloud moves over a polluted environment with higher CCN concentrations. Precipitation can be initiated in a non-precipitating cloud having a high concentration of small droplets by seeding giant CCN ( > 1 μ m in radius) into the cloud. Precipitation intensity in warm, stratiform clouds with and without background giant CCN differs little, implying very limited effects of background giant CCN on precipitation formation. The limited effects include a slightly slower precipitation formation, which is found to be caused by lower supersaturation, in clouds containing the background giant CCN compared to clouds without giant CCN. The delay of precipitation development is longer for continental clouds with high CCN concentration than for marine clouds with low CCN concentration. Sensitivity tests show that by increasing the giant CCN concentration an earlier precipitation can be initiated, especially in higher CCN concentration cases. It is concluded that the role of giant CCN on precipitation formation in warm, stratiform clouds is minor and is only important when concentrations of both the CCN and giant CCN (especially the largest CCN, e.g., > 5 μ m ) are high.

The influence of aerosol concentrations on the glaciation and precipitation of a cumulus cloud

AbstractThe response of the glaciation and precipitation of a multi‐thermal cumulus cloud to changes in the aerosol concentration has been assessed in a series of sensitivity tests with the UMIST Explicit Microphysics Model (EMM). A simulation of this cloud from the Met Office cloud‐resolving model (CRM) has been utilized in these tests. This cumulus cloud was observed by aircraft during the initial stage of its growth over New Mexico on 10 August 1987. The growth of the simulated cloud is divided into two parts: a shallow phase followed by a deep phase. Maximum values of the cloud depth in these two phases were 5 and 9 km, respectively.In the EMM simulations including only the shallow phase, the precipitation efficiency was found to decrease substantially with increasing atmospheric concentrations of cloud condensation nuclei (CCN). Also, the graupel mixing ratio and total ice concentration were found to decrease as normalized CCN concentrations were increased above typical continental values. These changes are explicable in terms of: (1) the Hallett–Mossop (H–M) process at −3 to −8°C and the freezing of supercooled raindrops in collisions with ice splinters dominating the glaciation; and (2) the warm‐rain process being more significant for the overall precipitation production than the ice process in these particular simulations. The almost complete suppression of precipitation by extreme CCN concentrations corresponding to a forest‐fire plume in the EMM simulation is consistent with the analysis by Rosenfeld of satellite images of Indonesian cumuli engulfed by smoke from biomass burning.A clear tendency for ice crystals to be smaller and more numerous in the anvil was found with increasing CCN concentrations beyond typical continental values in long‐term simulations that included the deep phase. The sensitivity of the precipitation rate to the normalized CCN concentration was found to be relatively low in these deep cases. Copyright © 2002 Royal Meteorological Society.