Assessing and forecasting atmospheric outflow of α-HCH from China on intra-, inter-, and decadal time scales.

Atmospheric outflow of α-HCH from China from 1952 to 2009 was investigated using Chinese Gridded Pesticide Emission and Residue Model (ChnGPERM). The model results show that the outflows via the northeast boundary (NEB, longitude 115-135 °E along 55 °N and latitude 37-55 °N along 135 °E) and the mid-south boundary (MSB, longitude 100-120 °E along 17 °N) of China account for 47% and 35% of the total outflow, respectively. Two climate indices based on the statistical association between the time series of modeled α-HCH outflow and atmospheric sea-level pressure were developed to predict the outflow on different time scales. The first index explains 70/83% and 10/46% of the intra-annual variability of the outflow via the NEB and MSB during the periods of 1952-1984 and 1985-2009, respectively. The second index explains 16% and 19% of the interannual and longer time scale variability in the outflow through the NEB during June-August and via the MSB during October-December for 1991-2009, respectively. Results also revealed that climate warming may potentially result in stronger outflow via the NEB than the MSB. The linkage between the outflow with large scale atmospheric circulation patterns and climate warming trend over China was also discussed.