Modeling of scattering enhancement factor, f(RH), in Chiba using visibility and ground measurements

[ABSTRACT]Monthly scattering enhancement factor, f(RH), is evaluated in Chiba in 2014. Hourly extinction coefficients at 875 nm are obtained from visibility meter operated at a Japan Meteorological Agency station located 2.5km south of Chiba University. Absorption coefficients at 875 nm are extrapolated from aethalometer measurements. Scattering coefficients are obtained as the difference between the extinction and absorption coefficients. These scattering coefficients in a month are averaged for every ambient relative humidity (RH). To obtain the dry scattering coefficient, a 7-point running average is applied to the visibility with RH to acquire the power-law fit of the visibility with RH. The scattering coefficient in the 0-30% RH range is the dry scattering coefficient obtained from the fit. The monthly f(RH) is the ratio of the scattering coefficients and the dry scattering coefficient in a month. A power-law is used to fit the f(RH) with RH. The winter months show increasing f(RH) with RH for RH>80%. November, December, January and February show that f(RH) starts to increase at around RH=75%. The high f(RH) values in February is considered as the effect of high RH in early morning. The change of f(RH) with RH is relatively insignificant in the summer months, although f(RH) rapidly changes with RH for RH>90%. This rapid increase can be explained as the effect of the presence of higher volume concentration of organics in the atmosphere, as revealed in the chemical component analysis previously conducted by our group.

https://opac.ll.chiba-u.jp/da/curator/107915/

https://opac.ll.chiba-u.jp/da/curator/107915/ceresIntlSympo-24-P846.pdf

Chiba University. Center for Environmental Remote Sensing

千葉大学環境リモートセンシング研究センター

会議発表用資料

Proceedings of the CEReS international symposium = CEReS国際シンポジウム資料集

24

846

849

2016-11-21

publisher

環境リモートセンシング研究センター「CEReSシンポジウム資料集」