Effects of multi-charge on aerosol hygroscopicity measurement by a HTDMA

The humidified tandem differential mobility analyzer (HTDMA) is widely used to measure the hygroscopic properties of submicron particles. The size-resolved aerosol hygroscopicity κ measured by a HTDMA will be influenced by the contribution of multiply charged aerosols, but this effect on field measurements has seldom been discussed for previous field measurements. Our calculations demonstrate that the number ratio of multiply charged particles is quite considerable for some specific sizes between 100 and 300 nm, especially during a pollution episode. The presence of multiple charges will lead to a compression effect on the aerosol hygroscopicity in HTDMA measurements. Therefore, we propose a new algorithm that performs multi-charge correction of the size-resolved hygroscopicity κ, taking both the compression effect and the multi-charge number contribution into consideration. Application of the algorithm to field measurements showed that the relatively high hygroscopicity in the accumulation size range leads to the overestimation of the hygroscopicity of particles smaller than 200 nm. The low hygroscopicity of coarse-mode particles leads to the underestimation of the hygroscopicity of accumulation particles between 200 and 500 nm in size. The difference between the corrected and measured κ values can be as large as 0.05, highlighting that special attention must be paid to the multi-charge effect when a HTDMA is used for aerosol hygroscopicity measurements.

Large-scale ion generation for precipitation of atmospheric aerosols

Artificial rain is explored as a remedy for climate change caused farmland drought and bushfires. Increasing the ion density in the open air is an efficient way to generate charged nuclei from atmospheric aerosols and induce precipitation or eliminate fog. Here we report on the development of a large commercial-installation-scale atmospheric ion generator based on corona plasma discharges, experimental monitoring, and numerical modeling of the parameters and range of the atmospheric ions, as well as the application of the generated ions to produce charged aerosols and induce precipitation at the scale of a large cloud chamber. The coverage area of the ions generated by the large corona discharge installation with the 7.2 km long wire electrode and applied voltage of −90 kV is studied under prevailing weather conditions including wind direction and speed. By synergizing over 300 000 localized corona discharge points, we demonstrate a substantial decrease in the decay of ions compared to a single corona discharge point in the open air, leading to large-scale (30 m ×23 m ×90 m) ion coverage. Once aerosols combine with the generated ions, charged nuclei are produced. Higher wind speed has led to larger areas covered by the plasma-generated ions. The cloud chamber experiments (relative humidity 130±10 %) suggest that charged aerosols generated by ions with a density of ∼104 cm−3 can accelerate the settlement of moisture by 38 %. These results are promising for the development of large-scale installations for the effective localized control of atmospheric phenomena.

Effects of Multi-Charge on Aerosol Hygroscopicity Measurement by HTDMA

The Humidified Tandem Differential Mobility Analyzer (HTDMA) is widely used to obtain the hygroscopic properties of submicron particles. Aerosol size-resolved hygroscopicity parameter κ measured by HTDMA will be influenced by the contribution of multiply charged aerosols, and this effect has seldom been discussed in previous field measurements. Our calculation demonstrates that the number ratio of multiply charged particles is quite considerable for some specific sizes between 100 nm and 300 nm, especially during the polluted episode. The multi charges will further lead to the shrinking effect of aerosol hygroscopicity in HTDMA measurements. Therefore, we propose a new algorithm to do the multi-charge correction for the size-resolved hygroscopicity κ considering both the shrinking effect and multi-charge number contribution. The application in field measurements shows that the relatively high hygroscopicity in the accumulation size range will lead to the overestimation of the particle's hygroscopicity smaller than 200 nm. The low hygroscopicity in coarse mode particles will lead to the underestimation of accumulation particles between 200 nm and 500 nm. The difference between corrected and measured κ can reach as large as 0.05, highlighting that special attention needs to be paid to the multi-charge effect when the HTDMA is used for the aerosol hygroscopicity measurement.

Large-scale ion generation for precipitation of atmospheric aerosols

Artificial rain is explored as a remedy to climate change caused farmland drought and bushfires. Increasing the ion density in the open air is an efficient way to generate charged nuclei from atmospheric aerosols and induce precipitation or eliminate fog. Here we report on the development of the large commercial installation scale atmospheric ion generator based on corona plasma discharges, experimental monitoring and numerical modeling of the parameters and range of the atmospheric ions, and application of the generated ions to produce charged aerosols and induce precipitation at a scale of a large cloud chamber. The coverage area of the ions generated by the large corona discharge installation with the 7.2 km long wire electrode and applied voltage of −90 kV is studied under prevailing weather conditions including wind direction and speed. By synergizing over 300 000 localized corona discharge points, we demonstrate a substantial decrease of the decay of ions compared to a single corona discharge point in the open air, leading to a large-scale (30 m × 23 m × 90 m) ion coverage. Once aerosols combine with the generated ions, charged nuclei are produced. The higher wind speed has led to the larger areas covered by the plasma generated ions. The cloud chamber experiments (relative humidity 130 ± 10 %) suggest that the charged aerosols generated by ions with the density of ~ 104/cm3 can accelerate the settlement of moisture by 38 %. These results are promising for the development of large-scale installations for the effective localized control of atmospheric phenomena.

Possibility of lightning in the Venusian clouds due to Super-rotation

<p>Lightning in Venus is still a matter of debate due to lack of evidence in optical and simultaneous radio emissions. Several evidence of electromagnetic emissions were previously measured by various landers and orbiters studying Venus atmosphere such as the Venera 13 and 14 landers, Venus Express and the Pioneer Venus Orbiter. This theoretical work proposes the mechanism of lightning is possibly due to the super-rotation of the clouds. Excessive amount of atmospheric turbulence and the formation of plumes in the clouds of Venus should possibly lead to the formation of charges in the clouds and thereby trigger lightning. As per Lorenz 2018, it is expected that there might exist charged aerosols in the lower atmosphere. This imposes another possibility of triboelectric charging mechanism which lead to lightning in the lower and middle cloud region. Lightning induced electromagnetic emissions that takes place in the clouds might be a result of momentum transfer and charge dispersion in the clouds of Venus. Venus can be considered to be an optically active planet with phenomenon like reflection and refraction ruling to some extent which possibly imposes a difficulty in lightning detection as the photons emitted during this process are scattered away. In the end, the possible lightning mechanism and difficulties related to its detection shall be discussed</p>

First results of combined ground- and rocket-based measurements for investigation of polar mesospheric winter echoes (PMWE)

<p>Two experimental sounding rockets were launched from Andøya Space Center<br>(Norway) devoted to investigate the phenomenon of polar mesospheric winter<br>echoes (PMWE). PMWE are relatively strong radar returns during winter,<br>observed at various frequencies (e.g. ≈ 50 MHz Maarsy or ≈ 224 MHz with<br>EISCAT). Despite possible tracing capabilities for dynamics in the Meso-<br>sphere over a wide annual and altitudinal extend, the formation process is<br>still not understood. To clarify the formation mechanism and proof theories,<br>an experimental setup consisting of two rocket payloads were designed. Aim-<br>ing for measuring neutral air temperature, relative and absolute densities of<br>plasma constituents (electrons, ions, charged aerosols), neutral air and trace<br>gases as well as turbulence. In-situ measurements were complemented by<br>ground based measurements of multiple radars and lidars.<br>We show results from contemporaneous multi instrumental in-situ measure-<br>ments and ground based observations based on the first part of the PMWE-<br>Project and discuss them in the context of most relevant theories.</p>