Diurnal and seasonal variations of the small‐, intermediate‐, and large‐ion concentrations and their contributions to polar conductivity

Abstract

Simultaneous measurements of the concentrations of small, intermediate and large ions and of polar conductivity of both polarities were made at a height of 1 m above ground at Pune (18° 32′N, 73° 51′E, 559 m above msl), India during February 1990 to January 1991. Diurnal and seasonal variations of concentrations of ions of all three categories show their peak values in the morning hours throughout the year. Concentrations of all categories of ions are higher during the nighttime as compared to that during the daytime and are higher in winter than in other seasons. Although small‐ion concentrations show only a small change, intermediate‐ and large‐ion concentrations undergo a change of up to 1 to 2 orders of magnitude over a period of a year. Most of the time, our observations do not exhibit any inverse relationship between the small‐ and large‐ion concentrations. The results have been explained in terms of the stability of the lower atmosphere and accumulation of radioactive gases, aerosols, etc., below nocturnal inversions. The diurnal and seasonal variations of the percentage contribution of three different categories of ions to the polar conductivity show that although contribution of small ions is dominant for most of the day, contributions of intermediate and large ions become very large in the morning hours, especially in winter. Diurnal variations of the mean values of polar conductivity calculated from the ion concentrations are compared with those of the measured values of polar conductivity. The two values show good agreement during the daytime when the polar conductivity is small. However, the measured values of polar conductivity are always higher than its calculated values during nighttime or in the morning hours when polar conductivity is large.

Estimation of small ion concentration near the Earth's surface

“…The small ions formed due to radioactivity of the Earth's surface are destroyed by recombination of ions of opposite signs, by combination with uncharged or oppositely charged aerosol particles. Even small changes in the size distribution of aerosols due to changes in meteorological conditions or to changes in the production rate of aerosol particles may largely affect the electrical state of atmosphere (Dhanorkar and Kamra, 1993). Tammet (1988) has surveyed the studies of small air ions and their interactions with the air molecules and aerosols in the surface layer and points out that the application of atmospheric electricity methods in monitoring the natural environment might play a central role in future studies.…”

Charged nanoparticles produced by splashing of raindrops

“…In absence of any local source of ion generation such as waterfall, rain shower, dust storm, corona, combustion, and volcano, the ion concentration close to ground is generally determined by thermodynamic and electrical process in the lower atmosphere. In fair-weather conditions, therefore, ion concentration near to ground normally shows a diurnal variation with a maximum in the morning hours [e.g., Dhanorkar and Kamra, 1993]. However, the background level of this diurnal variation of ion concentration shows significant variation.…”

“…This period at this station is otherwise associated with relatively much higher values of ion concentrations as depicted in their diurnal variations [Dhanorkar and Kamra, 1993]. In both cases, the heavy large ion concentration dropped to very low values during these periods.…”

The Electrical Conductivity as an Index of Air Pollution in the Atmosphere

“…In the morning, the vertical mixing caused due to increased eddy diffusivity will dilute the concentration of aerosols and radioactive emanations close to the ground. This may explain the occurrence of large concentrations at nighttime as compared to daytime (Dhanorkar and Kamra, 1993). Figure 4(a) represents two hourly values of the aerosol concentration obtained for each of the eight size categories in the range of 13 to 750 nm.…”

“…The outer electrodes are shielded from any external electric field by two coaxial cylinders of 11 cm diameter and 35 cm length separated from the outer electrodes with Bakelite rings. Opposite but equal potentials of ± 35 V are applied to the (Dhanorkar and Kamra, 1993) and is capable of resolving the values of conductivity as small as 3 x 10 -16 Ω -1 m -1 (Dhanorkar and Kamra, 1992). To avoid leakages along the insulators at higher humidity, Teflon is used to insulate all high impedance points in the apparatus because it maintains good insulation even at high humidity.…”