Coupling a Bat Algorithm with XGBoost to Estimate Reference Evapotranspiration in the Arid and Semiarid Regions of China

Table 1

Statistics of the meteorological data of the three stations during the training and testing stages in the study.

Station/Meteorological data	Average		Maximum		Minimum		Skew		Kurtosis		CV
	Training	Testing	Training	Testing	Training	Testing	Training	Testing	Training	Testing	Training	Testing
Datong
	14.52	14.54	32.38	29.05	−6.85	−5.13	−0.24	−0.31	−1.34	−1.41	0.79	0.82
	1.44	0.37	19.6	18.01	−18.93	−18.06	−0.14	−0.14	−1.36	−1.26	7.97	30.97
	7.98	7.45	25.99	23.53	−12.89	−11.6	−0.19	−0.23	−1.35	−1.34	4.38	15.9
	14.73	15.72	24.79	24.75	5.55	6.06	−0.05	−0.09	−1.28	−0.93	0.37	0.46
U	2.07	1.86	3.37	2.89	0.96	1.12	0.46	0.8	0.33	0.97	0.2	0.3
RH	51.34	54.32	76.94	78.47	26.47	29.53	−0.11	−0.25	−0.61	1.34	0.22	0.36
ETo	2.83	2.76	6.46	5.72	0.44	0.5	0.17	0.21	−1.33	−1.21	0.58	0.69
Yinchuan
	16.55	17.03	32.06	31.43	−5.45	−2.27	−0.29	−0.34	−1.29	−1.35	0.65	0.7
	3.98	4.94	20.09	19.5	−17.27	−13.41	−0.16	−0.27	−1.33	−1.17	2.66	2.17
	10.26	10.98	26.08	25.47	−11.36	−7.84	−0.23	−0.3	−1.31	−1.26	1.66	1.43
	15.93	15.4	25.85	24.05	6.4	7.02	0.04	−0.03	−1.28	−0.5	0.33	0.43
U	1.78	1.26	2.77	1.78	0.98	0.84	0.27	2.06	−0.23	5.59	0.21	0.54
RH	54.1	48.7	78.67	77.4	23.93	24.19	−0.46	0.03	−0.58	0.91	0.21	0.38
ETo	2.98	2.85	6.17	5.37	0.46	0.48	0.13	0.09	−1.39	−1.33	0.57	0.66
Taiyuan
	17.62	17.79	32.75	31.22	−1.89	−0.16	−0.25	−0.35	−1.34	−1.37	0.57	0.63
	4.9	5.37	21.36	20.18	−13.84	−11.21	−0.08	−0.2	−1.37	−1.26	2.07	1.91
	11.26	11.58	27.06	25.7	−7.87	−5.69	−0.17	−0.27	−1.36	−1.32	1.32	1.27
	13.29	15.46	22.3	27.81	4.41	6.08	0.03	0.12	−1.21	−0.66	0.35	0.47
U	1.44	1.39	2.6	2.49	0.57	0.82	0.6	0.89	0.23	0.48	0.27	0.35
RH	57.05	55.12	85.74	79.57	28.79	35.52	−0.09	0.03	−0.88	2.01	0.22	0.35
ETo	2.61	2.83	5.51	5.6	0.49	0.63	0.2	0.2	−1.29	−1.3	0.53	0.65