time

a

b

c

d

R2

Jan.

-19.811

0.000260

-0.051

0.231

0.207

Feb.

-70.701

0.001103

0.221

0.626

0.331

Mar.

-249.545

0.003390

0.433

2.336

0.406

Apr.

-16.862

0.004009

-4.289

1.879

0.584

May

408.331

0.009569

-12.540

0.869

0.810

Jun.

530.716

0.021000

-13.656

0.016

0.863

Jul.

689.699

0.029650

-12.485

1.018

0.870

Aug.

495.902

0.018520

-19.839

2.869

0.879

Sep.

196.940

0.009100

-15.049

4.003

0.856

Oct.

-5.170

0.002153

-5.737

2.341

0.841

Nov.

-136.015

0.000984

0.240

1.283

0.455

Dec.

-81.180

0.000480

0.493

0.627

0.166

Annual

1742.001

0.097260

-87.915

17.197

0.861
Table 2: Monthly linear regression coefficients and R2 needed to calculate monthly mean precipitation using altitude (H), latitude (Y) and longitude (X) for the southern Qilian Mountains (P = a + bH + cY + dX).