Continuous ground-based observation of aerosol optical properties in Tsukuba, Japan (trend and climatology)

 

Authors

Akihiro Uchiyama — Meteorological Research Institute
Akihiro Yamazaki — Meteorological Research Institute
Rei Kudo — Meteorological Research Institute

Category

Aerosol Properties

Description

In order to investigate optical properties of aerosol, scattering coefficients and absorption coefficients have been continuously measured since January 2002 using an integrating nephelometer (TSI model 3563) and an absorption photometer (Radiance Research PSAP, PSAP3) during dry conditions at Tsukuba, Japan. Using these data, the recent 10 years trend of aerosol properties and climatology was investigated.

The results show that the aerosol characteristics have seasonal variation and the tendency to decrease or increase. These tendencies were significant in the confidence level 95%. The extinction, scattering, and absorption coefficients (1/m) had trends to decrease in the period from 2002 to 2012: -6.05x10-6, -4.94x10-6(1/year) at wavelength of 550nm and -1.11x10-6(1/year) at wavelength 526nm, respectively. The single-scattering albedo (SSA) has the trends to increase in the same period: 4.27x10-3(1/year) at wavelength of 550nm. Asymmetry factors have the trends to decrease in the same period: -2.22 x10-3(1/year) at wavelength 550nm. The extinction Ångström exponent has the tendency to increase, and the effective radius has the tendency to decrease. These tendencies are consistent with the tendency of asymmetry factor. The values of absorption Ångström exponent were about 1.0 and have seasonal variation. The absorption Ångström exponent had the trend to increase in the period from 2006 to 2012: 1.15x10-2(1/year). The change of absorption Ångström exponent suggests the change in the composition of light-absorbing aerosol. These tendencies are consistent with the results of radiometer data analysis.

Using data in the period from 2006 to 2012, the frequency distributions of aerosol properties were investigated. In this period, a 3-wavelength PSAP 3 was used. The most frequent values of extinction and absorption coefficients are 35x10-6(1/m) at wavelength of 550nm and 5x10-6(1/m) at wavelength of 526nm, respectively. The most frequent value of SSA was 0.855 at wavelength of 550nm. The characteristic of frequent distribution in every season was characterized by the dominant air mass in every season.