Fig. 6: Annual and monthly variations of AOD and relative humidity in different regions.
From: Using particle swarm optimization to improve visibility-aerosol optical depth retrieval method
a Annual series of AOD from 1960 to 2014 (The regions in the red boxes represent trend significance t-test at 95% confidence level). b Annual series of relative humidity from 1960 to 2014. c Monthly distribution of AOD. d Monthly distribution of relative humidity.
