Potential Impacts of Wintertime Agricultural Irrigation at Low Latitudes on Global Climate

Abstract:

The effect of agricultural irrigation on environment has long been an important issue to investigate. Since the anthropogenic water management is able to change the surface energy budgets and the water cycle, some research has been done to assess its impacts on both regional and global climate. Note that much of the agricultural irrigation at boreal low latitudes is applied in wintertime. In this study, we use NCAR Community Earth System Model (CESM) to simulate the land-air interaction processes with water management and the consequent responses in atmospheric circulation and hydrological cycle. We conduct some perturbed experiments with different model complexities to clarify the corresponding effects of changes in surface energy balances and atmospheric circulation in both local and global manner. The preliminary results show that the wintertime agricultural irrigation at low latitudes is able to lower the surface Bowen ratio, and reduce the surface temperature in a continental scale through atmospheric feedbacks and to change the intensity of prevailing monsoon circulation. In addition, we observed anomalous tropical precipitation and mid-latitude climatic changes indicating tropical-extra tropical teleconnections. Based on these results, we propose that the location of heavily irrigated place is important to have impacts on remote regions which might be an important consideration on human sustainability. We also try to track the fingerprint of this potential climate forcing in observational data and to estimate its contribution relative to other anthropogenic and natural forcing in future climate projection.