Spatial and Temporal Distribution of Visibility under Fog and Haze Conditions in Guangdong Province:Annual and Inter-Annual Change

Analysis on the temporal and spatial distribution of visibility under fog and haze conditions is of great significance to understanding and forecasting the occurrence of the fog and haze.In this paper,meteorological visibility collected from 26 ground stations in Guangdong Province from 1980 to 2003 was used for the fog and haze analysis.Empirical orthogonal function(EOF) method and continuous power spectral analysis method were applied to the 24 years observation data.The spatial and temporal distribution of the visibility under fog and haze weather condition was then analyzed.The EOF results show that the inter-annual changes of the visibility under fog and haze condition of Guangdong Province can be divided into two main modes.The spatial distribution of the first mode(which rated at 17.4%) is exactly corresponding to the geographical divisions of Guangdong Province.The time series distribution of the first mode reflects the inter-annual changes of the visibility in fog and haze conditions.The decrease of the time sequence from positive to negative in 1992 is mainly due to the economic development of Guangdong Province since 1990s.The second mode(rated at 11.8%) reflects consistent spatial and temporal changes of the visibility.Its time sequence indicates 3 inter-annual periodical oscillations,which are the 2-year periodical oscillations,4-year periodical oscillations and 8-year periodical oscillations.This annual periodicity of the visibility under fog and haze conditions may be primarily related to the large-scale tele-connection of monsoon and ENSO(El Nino /South Oscillation).