Global water vapor content and vegetation change analysis based on remote sensing data

Abstract

Water vapor in the Earth's upper atmosphere plays a crucial in the radiative balance, hydrological process, and climate change. Based on the latest MODIS data, this study probes the spatio-temporal variations of global water vapor content in the past decade. It is found that overall the global water vapor concentrations declined over 2003–2012 (b=− 0.0149, R2=0.797, p=0.0005). The decreasing trend over the ocean surface (b= −0.017, R2=0.824, p=0.0003) is more explicit than over terrestrial surface (b= −0.010, R2=0.612, p=0.007), more significant over the Northern Hemisphere (b= −0.0175, R2=0.852, p=0.0001) than over the Southern Hemisphere (b= −0.0123, R2=0.682, p=0.003). Vegetation cover change is critical for an understanding of the impacts and responses of vegetation to climate change. The global vegetation growth has been analysised from 2001 to 2012. After thorough analysis based on satellite data, we find evidence that the global vegetation change little, and it is increasing slightly in Northern hemisphere while it is deceasing slightly in Southern Hemisphere. For different latitudes, the vegetation is increasing 0.17% every year from 60°N to 70 °N (R2=0.47, P>0.013), while the vegetation is decreasing 0.11% every year from 10°N to 10°S (R2=0.54, P>0.004). For different continents, the vegetation in South America is decreasing 0.16% every year (R2=0.78, P>0.0001) and it is increasing 0.05% every year in Asia (R2=0.28, P>0.072) and 0.25% every year in Oceania (R2=0.24, P>0.1).