Three types of drought are commonly noted including meteorological,
agricultural, and hydrological droughts. This paper presents
a synergistic approach spatially and temporarily between two
types of drought indices associated with two reference years of
1987 and 2000. With the aid of advancements of contemporary
remote sensing technologies, cross-linkages and -comparisons can
be made possible to assess these three types of drought in an allinclusive
framework. Our culminating experience obtained in a
field-scale study in China proved the efficacy and effectiveness of
our approach.
Both drought indices of TVDIs and RWSI can be tied together
to address soil moisture dynamics and drought impacts. When the
values of RWSI may be integrated with TVDI SAVI, TVDI ANDVI and
TVDI MSAVI for drought assessment, we found that the shortage of
soil water in 1987 was more severe than that in 2000. However,
the use of TVDI NDVI cannot draw on the same conclusion. It was
due to that TVDIs are suitable for monitoring situations of wet, normal
and light dry conditions when RWSI < 0.752. In the situation of
medium dry as the value of RWSI is smaller than or equal to 0.8,
the TVDIs can still monitor drought correctly. Nevertheless, when
dealing with medium dry and heavy dry as the value of RWSI is
greater than 0.8, TVDIs cannot correctly portray the situation of
water shortage for drought assessment. As a consequence, TVDIs
should not be used to monitor the medium and heavy drought
(RWSI > 0.8).