Differentiation of Wetland Areas in the West Siberian Lowland Using NOAA/AVHRR Imagery
Masayuki Tamuraa, Hiroto Shimazakia, Hirato Shimazakia, Mitsushiro Tomodadaa, Fumiko, Makitaa, Zhao Wenjina and Yoshifumi Yasuoka b
aNational Institute for Environmental Studies, Tsukuba, 305-0053 Japan
b Institute of Industrial Science, University of Tokyo, Tokyo, 106-8558 Japan
Abstract
A method is presented for differentiating wetland areas in northern high-latitude zones using Normalized Difference Vegetation Index (NDVI) and land surface temperature (T
s) calculated from midday NOAA/AVHRR imagery. Wetland areas have been distinguished from other land-cover types using signatures on a scattergram of NDVI vs. T
s . The method was applied for differentiating wetland areas in the basin of the Ob River in the west Siberian lowland. The result have been verified with ground-truth data and land-cover classification results obtained from high-resolution satellite images.
1. Introduction
The west Siberian lowland is presumed to be a large source of atmospheric methane, which is the most important greenhouse gas after carbon dioxide. The Japan-Russia joint research project conducted since 1991 by the National Institute for Environmental Studies (NIES) and Russian researchers has produced results confirming the presumption
1. As basic data for estimating regional-scale methane fluxes from the west Siberian lowland, it is necessary to necessary to measure the distribution and areal extent of wetlands and to monitor seasonal changes of vegetation and surface conditions such as surface temperature and water level. Since detailed geographic information is not available in west Siberia and it is often difficult to access wetlands by ground vehicles, satellite or aerial images are necessary for investigating wetland ecosystems and mapping the geographic distribution of wetlands. In this study we present a method for differentiating wetland areas in west Siberia using midday NOAA/AVHRR imagery. Use of AVHRR data makes it possible to map the geographic distribution of wetlands with 1 km ground resolution.
Fig. (a) AVHRR image (in Band 1) obtained on 8th July 1995 in the Ob Basin. Area size: 450 km wide and 415 km long. Scene center: (82°E, 58°N). (b) Ground-observation site.
2. Study Area
Fig. 1(a) shows the AVHRR image taken at 7:21 GMT (around 13:00 in local solar time) on 8th July 1995 in the basin of the Ob River. It covers a rectangular area centered at (82°E, 58°N) with a width 450 km and a height 415 km. The Ob River flows from bottom right to top left. Wetlands and forests occupies most part of the image area, and there are also several villages and agricultural lands along rivers. The Wetlands are mainly covered with sphagnum mosses, sedges, cotton grasses, reeds, dwarf shrubs and low pine trees. The forest vegetation consists of both deciduous tree (birches and aspens) and coniferous trees (pines and larches).
The image includes the mires where the NIES and Russian researches are making ground observations of wetland vegetation, methane fluxes, surface temperatures and water levels. The location of the ground-observation site is indicated by the white rectangle in Fig. 1(a) and its enlarged image is shown in Fig. 1(b).
