Spatial distribution and temporal variation of aerosol optical depth in the Western Pacific Ocean

The temporal and spatial characteristics of the aerosol optical depth (AOD) in the Western Pacific Ocean are analyzed using the field observation data and AVHRR remote sensing data. The observation AOD shows a significant north-south difference with a boundary of 25 N. In the north, the AOD spectral distribution shows a feature of decrease with the increase of wavelength in the range of 440-870 nm. In the south, the AOD maximum is at 500 nm. The average AOD (440) in the north is 0.177 larger than that in the south. The northern average Angstrom exponent (alpha) is 3.2 times as large as that of the south. In terms of climatology, as the subtropical high ridge moves northward up to 12 from February to August, the location of AOD(630) maximum around 35 N moves northward by 10.5 . In addition to the northern maximum, the zonal mean of AOD (630) from AVHRR shows another maximum, located at 10N. The AOD(630) at 35N reaches its maximum in April, while the AOD(630) at 10N reaches its maximum in March. The multi-year variation of AOD(630) at 35N is consistent with that at 10N with a correlation coefficient of 0.77. Research on the month of the climatological AOD(630) maximum at around 10N shows that it is attributed to the joint action of aerosols from the sea south of 10N and East Asia.