Fig. 5: Dependence of changes of ozone with and without lockdown reductions on VOCs/NOx ratios.

The x-axis was the simulated VOCs/NOx ratios in each grid from the Base case grouped over 0.1 ppbC/ppbv VOCs/NOx bins, which indicated the present status in the YRD region. There were 862 grids in the YRD domain in the model. The horizontal bar presented the dependence of changes of ozone between the Base and COVID cases during lockdown period on VOCs/NOx ratios (those from Base case during lockdown), with the color bar axis as well as the x-axis, and the blank areas indicated no data samples under these ratios. The lines were the frequency of different VOCs/NOx ratios from the Base case indicated by the y and x arises.