Detecting Arctic Change Using the Koppen Climate Classification
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Detecting Arctic Change Using the Koppen Climate
Classification
Muyin Wang1
James E. Overland2
1 JISAO/UW, 2 PMEL/NOAA,
Seattle, WA
Photos from the Ayiyak River (Alaska) show an increase in shrubs. Sturm et al., 2001, Nature
& Satellite NDVI
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The Koppen Classification
Temperate D T>= 10oC for 4 or more months
Boreal E T>= 10oC for 1-3 months
PolarTundra Ft 0oC <= T <10oC in summer
Perpetual Frost
Fi T < 0oC in summerData
NCEP/NCAR reanalysis 2.5x2.5 1948-2002
CRU/UA TS2.0 0.5x0.5 1901-2000Mitchell, et al, 2003
Kalnay, et al, 1996
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TundraFrostBoreal
Temperate
Vegetation Distribution based on Koppen Classification
NCEP
CRU
1978
1950
1998
1998
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Calculated Vegetation Distribution Based on CRU/
Tundra
Boreal
Temperate
NCEP10
6 km
2
106 k
m2
106 k
m2
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Satellite Normalized Differences Vegetation Index (NDVI) is calculated from the visible (VIS) and near-infrared (NIR) light reflected by vegetation in the AVHRR channels.
NIR – VISNIR + VIS
NDVI =
Global monthly NDVI data set is provided by NASA on 1x1o resolution from July 1981 to September 2001.
The value increases from 0.1 to 0.9 for progressively increasing amounts of green vegetation.
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1.0
0.8
0.6
0.4
0.2
0.0
Distribution of vegetation type based on Koppen classification
The lost tundra areas
The summer NDVI climatology
The change in NDVI from 1980s to 90s
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CONCLUSIONSThe potential impact of vegetation
changes to feedbacks on the climate system is enormous because of their large land area and multiyear memory of the vegetation cover in the Arctic region.
• The Koppen classification based on SAT agrees well with satellite NDVI. Both indicate a significant decrease in the tundra area in the past 20 years – about 1 million km2 lost.
• A similar decreasing trend was seen in the early 1900s, but with smooth slope.
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The Area of Tundra Group Based on CRU SATAnd the Averaged NASA NDVI for 50-90oN
Correlation Correlation = = -0.70-0.70
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Scandinavia
Siberia
N.W. America
N.E. America
Tundra Boreal + Temperate
Anomalies of Vegetation Group for Sub-regions
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THE LOST TUNDRA AREA: Max - Min
CRU: 1950 – 1998 NCEP: 1978 -1998
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Anomalies of Tundra & Boreal for sub-regions in Arctic
Scandinavia
Siberia
N.W. America
N.E. America
Tundra Boreal
106 k
m2
106 k
m2
106 k
m2
106 k
m2
10oW ~120oE
120oE ~170oW
170oW ~80oW
80oW ~40oW
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