Impacts of Land Use/Cover Change on Spatial Patterns of Summer Precipitation at Decadal Scale over Eastern China

Abstract:

The impacts of land use/cover change (LUCC) on the spatial distributions of summer precipitation over Eastern China at decadal timescale during the last millennium are investigated, using a set of land use/cover sensitivity experiments from the Last Millennium Ensemble (LME) archive conducted by (NCAR) with Community Earth System Model (CESM). We compared the two leading modes of summer precipitation over Eastern China at decadal scale before (with slightly LUCC) and after (with drastically LUCC) 1750 AD. The results show that the LUCC plays an important role in modulating the summer precipitation distribution pattern over Eastern China at decadal scale. Before 1750 AD, the first leading mode of decadal summer precipitation over Eastern China exhibits a meridionally dipole pattern while the second leading mode exhibits a meridionally tripolar pattern. After 1750 AD, the spatial distribution is reversed, the tripolar pattern becomes the first leading mode and the dipole pattern becomes the second leading mode. During both periods, the “dry north-wet south” dipole pattern is associated with an “A-C” (anticyclone-cyclone) circulation anomalies at low-level and the related water vapor divergence-convergence pattern from north to south over east part of East Asia. Whereas the tripolar pattern corresponds to an “A-C-A” (anticyclone-cyclone-anticyclone) circulation anomalies and the related tripolar pattern of the water vapor divergence/convergence. The regressed sea surface temperature (SST) shows that the precipitation distribution patterns are related to the PDO and AMO modes. The AMO shows a decreasing trend during the last millennium, with the increased anthropogenic land cover change. We suggest that the LUCC tends to modulate the distribution patterns of Eastern China precipitation at decadal scale by influencing the AMO mode.