426
Multiscale Hydrologic Remote Sensing: Perspectives and Applications
Below 40°N latitude, vegetation cover is dominated by mixed forest and cropland
in the regions of eastern and southern China, India, and Pakistan and the countries
surrounding Thailand. The range of NDVI values from April to July exhibits only a
small change, but more areas have higher values. Similar behavior was also observed
in the seasonal change of the MVIs. The evergreen broadleaf forest in Southeast
Asia remained almost unchanged, with values characteristic of very high levels of
vegetation for both the optical and microwave vegetation indices. The barren areas in
Tibet and western Asia show only a slight change in both the optical and microwave
images.
18.4.2.2 Africa and Australia
From the north to south over the African continent, the land cover types exhibit a
clear pattern that reflects the transition of increasing vegetation from dessert/barren–shrubs–savannas–woody savannas to the evergreen broadleaf forest, followed by
decreasing vegetation from woody savannas–savannas and back to shrubs. The corresponding vegetation indices derived from both MODIS and AMSR-E show not only
that the spatial distributions of vegetation are related with the land cover types but also
the strong spatial consistency between the optical and microwave measurements.
The desert and barren regions have values that indicate bare surfaces or no vegetation cover in both the optical- and microwave-derived vegetation information for both
April and July and exhibit no significant change with season. It is interesting to note that
the B parameters for the low- and high-frequency pairs have a similar range (~0.9). The
A parameter ranges from 26 to 29 K for the low-frequency pair and from 10 to 100 K
for the high-frequency pair in both April and July. However, there is a noticeable change
in mean values over this region from April to July, with more areas covered by lower B
(decreased from 0.82 to 0.77) and higher A (increased from 52 to 66 K) values (Figures
18.2c, 18.2e, 18.3c, and 18.3e). This change might result from the sparse shrubs in these
regions that are dominated by the woody component with leaves.
In regions of evergreen broadleaf forest, the MODIS-derived NDVI exhibits very
high values. The AMSR-E-derived MVIs exhibit some of the highest A parameter
and the lowest B parameters values. As expected, both the NDVI and MVIs show no
significant change between April and July. Regions with the values of the vegetation
indices that indicate denser vegetation in the northern hemisphere extend further
north between April and July, while the reverse occurs in the southern hemisphere
reflecting seasonal changes in vegetation.
In Australia, where most regions are covered by shrubs, the vegetation distribution
patterns in both the MODIS- and AMSR-E-derived vegetation indices agree very
well. When compared to April, the July observations show a significant decrease
in the MVIs derived by the high-frequency pair observations for the seasonal difference in the southern hemisphere, while both NDVI and the MVIs derived by the
low-frequency pair observation show no significant change.
18.4.2.3 South America
The distribution patterns of all optical- and m icrowave-derived vegetation index
images agreed well and correlated to the land cover types. The evergreen broadleaf
forest area is characterized by low MVI B values and high A values as well as high
Multiscale Hydrologic Remote Sensing: Perspectives and Applications
Below 40°N latitude, vegetation cover is dominated by mixed forest and cropland
in the regions of eastern and southern China, India, and Pakistan and the countries
surrounding Thailand. The range of NDVI values from April to July exhibits only a
small change, but more areas have higher values. Similar behavior was also observed
in the seasonal change of the MVIs. The evergreen broadleaf forest in Southeast
Asia remained almost unchanged, with values characteristic of very high levels of
vegetation for both the optical and microwave vegetation indices. The barren areas in
Tibet and western Asia show only a slight change in both the optical and microwave
images.
18.4.2.2 Africa and Australia
From the north to south over the African continent, the land cover types exhibit a
clear pattern that reflects the transition of increasing vegetation from dessert/barren–shrubs–savannas–woody savannas to the evergreen broadleaf forest, followed by
decreasing vegetation from woody savannas–savannas and back to shrubs. The corresponding vegetation indices derived from both MODIS and AMSR-E show not only
that the spatial distributions of vegetation are related with the land cover types but also
the strong spatial consistency between the optical and microwave measurements.
The desert and barren regions have values that indicate bare surfaces or no vegetation cover in both the optical- and microwave-derived vegetation information for both
April and July and exhibit no significant change with season. It is interesting to note that
the B parameters for the low- and high-frequency pairs have a similar range (~0.9). The
A parameter ranges from 26 to 29 K for the low-frequency pair and from 10 to 100 K
for the high-frequency pair in both April and July. However, there is a noticeable change
in mean values over this region from April to July, with more areas covered by lower B
(decreased from 0.82 to 0.77) and higher A (increased from 52 to 66 K) values (Figures
18.2c, 18.2e, 18.3c, and 18.3e). This change might result from the sparse shrubs in these
regions that are dominated by the woody component with leaves.
In regions of evergreen broadleaf forest, the MODIS-derived NDVI exhibits very
high values. The AMSR-E-derived MVIs exhibit some of the highest A parameter
and the lowest B parameters values. As expected, both the NDVI and MVIs show no
significant change between April and July. Regions with the values of the vegetation
indices that indicate denser vegetation in the northern hemisphere extend further
north between April and July, while the reverse occurs in the southern hemisphere
reflecting seasonal changes in vegetation.
In Australia, where most regions are covered by shrubs, the vegetation distribution
patterns in both the MODIS- and AMSR-E-derived vegetation indices agree very
well. When compared to April, the July observations show a significant decrease
in the MVIs derived by the high-frequency pair observations for the seasonal difference in the southern hemisphere, while both NDVI and the MVIs derived by the
low-frequency pair observation show no significant change.
18.4.2.3 South America
The distribution patterns of all optical- and m icrowave-derived vegetation index
images agreed well and correlated to the land cover types. The evergreen broadleaf
forest area is characterized by low MVI B values and high A values as well as high