1990 
1992 
1994 
1996 
1998 
2000 
Water/Lake 
536.65 
469.65 
126.76 
1091 
1102.3 
1251.23 
Glacier/Snow 
43.57 
13.33 
46.55 
133.56 
82.6 
135.46 
Alpine meadow 
8764.8 
1466.23 
133.32 
1933.8 
1225.31 
96.7 
Alpine grassland 
38029.66 
40349.75 
40850.26 
33964.1 
32627.64 
29204.5 
alpine steppe& 
9188.32 
13471.96 
14238.26 
14335.6 
15958.4 
20047.32 
Alpine desert 
693.96 
1458.36 
1999.21 
6290.45 
6647.45 
7152.3 
Subalpine meadow 
33066.32 
15046.31 
8488.76 
11165.65 
14187.89 
2625.4 
Subalpine grassland 
9695.98 
27684.52 
33612.23 
30188.2 
27767.33 
38602.3 
Subalpine desert 
267.2 
313.66 
840.56 
1495.32 
915.64 
1576.2 
grassland 
Subalpine desert 
18.78 
10.78 
37.33 
129.29 
72.14 
113.6 
Meadow grassland 
877.5 
235.88 
76.21 
252.35 
179.3 
54.2 
Steppe 
3882.4 
4329.63 
4374.31 
2776.45 
2912.12 
2236.1 
Desert grassland 
2420.32 
2515.85 
2516.56 
2412.8 
2536.3 
2425.31 
Desert 
979.77 
1098.81 
1124.87 
2297.36 
2251.4 
2944.6 
Tab. 2 Area of Each Landcoverage Type During 1990—2000 (Uint: km 2 ) 
AAA 
AAMa 
AAMi 
AAP 
AAA 
AAM 
AAMi 
AAP 
Water 
0.44 
0.43 
-0.38 
0.23 
Subalpine 
grassland 
0.23 
0.65 
-0.04 
0.19 
Snow&Glacier 
0.55 
0.80 
0.08 
0.43 
Subalpine desert 
grassland 
0.53 
0.87 
0.12 
-0.28 
Alpine 
meadow 
-0.26 
-0.42 
0.15 
-0.45 
Subalpine desert 
0.57 
0.76 
0.00 
-0.30 
Alpine 
-0.47 
-0.59 
0.16 
0.33 
Meadow 
-0.29 
-0.46 
0.11 
-0.42 
alpine steppe& 
desert steppe 
0.30 
0.68 
-0.15 
0.03 
Steppe 
-0.50 
-0.63 
0.15 
0.35 
Alpine desert 
0.66 
0.58 
-0.19 
-0.03 
Desert grassland 
0.13 
-0.54 
-0.20 
0.13 
Subalpine 
meadow 
-0.25 
-0.68 
0.03 
-0.16 
Desert 
0.50 
0.69 
-0.18 
-0.21 
Tab.3 Relationship Between Landcoverage Type and Climate Factors 
5. CONCLUSION 
According to NOAA-AVHRR data and meteorological data we 
studied the relation between land coverage changes and climate 
transition during the period of 1900-2000 and how the process 
is. The follow conclusions are drawn: 
1) As the global climate becoming warmer, the climate in 
headstream region of Yellow River changes continuously 
during 1990 — 2000 period, among which the annual highest 
temperature increased greatly as long as the annual lowest 
temperature increased slowly, while the annual average 
precipitation decreased with fluctuates. 
2) Within the 11 years, from 1990 to 2000, the land coverage 
type in headstream region of Yellow River changed a lot. A 
large area of grassland degraded, the average vegetation 
coverage of this region reduced obviously, the area of land 
desertification increased greatly which indicates the ecological 
environment in headstream region of Yellow River became 
worse. 
3) There is correlativity between change of land coverage type 
in headstream region of Yellow River and the climate factors 
changes. The increase of temperature and the decrease of 
precipitation have different influence of different land coverage 
type. Therefore the climate change is a very important factor of 
the land coverage change. 
4) According to the study of land coverage change in 
headstream region of Yellow River at the kilometer scale, it 
shows that NOAA-AVHRR has a great foreground on the study 
of middle size geography problems and it is helpful to the study 
of middle size special problems. 
5) BP NN(Nerve Net) is a very prosper model of NN and 
useful to the study of classification of images and decomposing 
mixed pels.