Effects of Continentally Polluted Air Mass on Aerosol Optical Properties over the East China Sea

Abstract

Aerosol physical and chemical properties and relative humidity (RH) in the marine atmosphere undergo their modifications under the influence of continentally polluted air mass. Effects of continentally polluted air mass on aerosol optical properties over the East China Sea were studied by using data of aerosol size and number, aerosol composition, and RH. These data were obtained under Atmospheric Particulate Environmental Change Experiment 2/Asian Pacific Regional Aerosol Characterization Experiment (APEX-E2/ACE-Asia). Data collected on 18, 21, 23, and 26 April 2001 were used in this study. In order to evaluate contributions of such modifications to aerosol optical thickness (AOT) and single scattering albedo (SSA), AOT and SSA of the continentally polluted marine atmospheres were compared with values calculated by replacing each parameter (aerosol composition, aerosol size and number, and RH) of the continentally polluted marine atmospheres with that of the marine atmosphere. Further, by not separating aerosol composition and aerosol size and number parameters, investigations were performed by replacing these parameters of the continentally polluted marine atmospheres with those of the marine atmosphere. Modification of aerosol size and number was found to have a tendency to increase AOT significantly, whereas modification of aerosol composition by only a few percentages. Since continental air had relatively low RHs, modification of RH was found to have a tendency to decrease the value. The result also suggested that the decrease of aerosol hygroscopicity by continentally polluted air mass tended to decrease AOT. On the other hand, not only aerosol composition and RH modifications, but also aerosol size and number modification had a tendency to decrease SSA. The study pointed out an important role of continentally polluted air mass on aerosol radiative forcing, due to the increase of AOT and the decrease of SSA over the East China Sea.

Use of 315 nm Channel Data of the Sky Radiometer to Estimate the Columnar Ozone Concentration: A Preliminary Study

“…4.2). A small difference in the refractive index between the wavelengths of 315 nm and 340 nm can be expected to have a negligible effect on the calculated τ aerosol (315 nm) because τ aerosol is a strong function of aerosol size distribution rather than the refractive index (King et al 1978;Khatri and Ishizaka 2007). Similarly, using the known value of the atmospheric pressure corresponding the observation site, one can calculate the Rayleigh optical thickness (τ Rayleigh ) at 315 nm (Frohlich and Shaw 1980); the relative optical air masses for ozone (m ozone ) and air (m air ), as well as the sun-earth distance (R) can be calculated using the observation time, latitude, and longitude.…”

Aerosol Effects on Water Cloud Properties in Different Atmospheric Regimes

“…On the contrary, the influence of increased AOT can be noted to be very weak in the clean maritime atmosphere. One of the most important differences in the characteristics of the polluted continental and the clean maritime atmospheres is that light‐absorbing aerosols are considerably high in the former than in the latter (Khatri & Ishizaka, 2007). Hence, the strong influence of increased AOT on the stability profile in the polluted continental atmosphere can be suggested due to the effect of such light‐absorbing aerosols.…”

Retrieval of cloud properties from spectral zenith radiances observed by sky radiometers

“…For 1.627 µm, F 0 derived from the NL method can be used, but the NL is less practical to implement routinely in short time intervals (e.g., each month) to derive temporal F 0 . We prefer to use temporal F 0 for all wavelengths to include filter degradation with time (e.g., Khatri et al, 2014). To derive temporal F 0 at 1.627 µm, we use an alternative IL method, as proposed by .…”