An Analysis of Seasonal and Decadal-long Variations of Aerosols over the Asian Pacific Region using NOAA/AVHRR Data

Abstract

Seasonal and decadal-long variations of aerosols in the Asia Pacific region, over the seas east off the Asian continent, have been analyzed using AVHRR data from NOAA-11 and NOAA-14 satellites. The aerosol optical thickness at wavelength 0.5 mm and Å ngström exponent were retrieved by means of the so-called two-channel algorithm for the period of about 12 years, between November 1988 and January 2001. Evident seasonal variation was found in the geographical distributions of aerosols over the region. Excepting the interval of strong influence by the Pinatubo volcanic eruptions, the aerosol optical thickness has gradually increased almost all over the region during the analyzed period. The present results verified the fact that the Asian Pacific region is under significant influence of natural and anthropogenic aerosols from the Asian continent.

Increasing trend of submicron aerosol particles over East Asian waters observed in 1998-2004 by Sea Wide Field-of-view Sensor (SeaWiFS)

“…It is interesting to observe a slightly increasing trend of Ångström exponent from the monthly mean data, with a mean slope of 0.0139 (per year) and standard deviation of 0.0017 for the first 5 sub-areas. The uptrend is consistent with the result of Sobajima et al11 who used the AVHRR data from NOAA-11 and NOAA-14, while they found a rapid increase in Ångström exponent during 1998-2000, which is different from the steady and gradual increase we found from the SeaWiFS data. The mean increasing slopes (per year) of Ångström exponent for each sub-area are 0.0144, 0.0134, 0.0151, 0.0112, 0.0153 and The annual mean sub-micron fraction (SMF) of AOT at 550nm above the Asian ocean.Marked numbers represent different sub-areas shown inFig 1.…”

Increase in Global Solar Radiation with Total Cloud Amount from 33 Years Observations in Japan

“…SO 2 emitted from East Asia forms aerosols during its transport and hence may affect the atmosphere over Japan, located east of East Asia. The aerosol optical thickness was found to increase over the Asia-Pacific region from 1988 to 2001, as indicated by satellite observation (Sobajima et al 2004). However, this observation was inconsistent with an observation over Japan: the atmospheric transparency (Feussner-Dubois' turbidity coefficient) averaged for Japan, derived from direct solar radiation observations at 14 stations of the Japan Meteorological Agency (JMA), showed a increasing (clearer) trend from the 1980s to the early 2000s except during the influences of eruptions of Mt.…”

Trends in aerosol radiative effects over China and Japan inferred from observed cloud cover, solar “dimming,” and solar “brightening”

“…Long‐term variations in solar radiation over Japan have received less attention. Sobajima et al [2004] found that satellite‐retrieved aerosol optical depth increased over the western North Pacific between 1988 and 2001, principally owing to transport from the Asian continent. This, however, did not apparently lead to a declining trend in solar radiation over Japan since Wild et al [2005] report that annual mean solar radiation has been increasing over Japan since the mid‐1980s, according to a polynomial fit to the time series.…”