Table 3.

ADF and PP unit root tests

Variables	ADF test statistics	PP test statistics
AMI	− 28.22	− 28.19
Average temperature	− 14.34	− 14.25
Average humidity	− 16.61	− 16.66
Raining	− 23.74	− 23.73
Sunshine hours a day	− 12.32	− 17.36
Daily evaporation rate	− 3.53	− 10.17
Wind direction	− 25.93	− 25.94
Wind speed	− 24.75	− 24.78
Critical values
1%	− 3.43	− 3.44
5%	− 2.86	− 2.86
10%	− 2.56	− 2.57

The maximum lag length is taken as 20