Trends in Dryness Index Based on Potential Evapotranspiration and Precipitation over 1961–2099 in Xinjiang, China

Table 4

The selected predictors used for developing a relationship between the predictand and predictor.

Number	PR	NPP	NPE
1	Mean sea level pressure	7	13
2	Surface airflow strength	2	3
3	Surface zonal velocity	5	9
4	Surface meridional velocity	12	6
5	Surface velocity	24	12
6	Surface wind direction	2	1
7	Surface divergence	10	1
8	500 hPa airflow strength	10	1
9	500 hPa zonal velocity	13	3
10	500 hPa meridional velocity	19	7
11	500 hPa velocity	24	1
12	500 hPa geopotential height	29	20
13	500 hPa wind direction	0	0
14	500 hPa divergence	0	0
15	850 hPa airflow strength	1	2
16	850 hPa zonal velocity	9	10
17	850 hPa meridional velocity	8	8
18	850 hPa velocity	6	7
19	850 hPa geopotential height	0	0
20	850 hPa wind direction	0	0
21	850 hPa divergence	0	0
22	500 hPa relative humidity	17	5
23	850 hPa relative humidity	17	14
24	Near surface relative humidity	8	8
25	Surface specific humidity	1	25
26	Mean temperature at 2 m	6	41

PR: Predictor, NPP and NPE: numbers of stations used for establishing predictor-predictand relationship of rainfall and .