Estimation of daily evapotranspiration by using MODIS data
Shigi Yang ^^, Rui Sun ??, Xuefeng Zhang”
(1. School of Geography, Beijing Normal University, Beijing,100875, China;
2. State key Laboratory of Remote Sensing Science, Beijing, 100875, China;
3. Beijing Key Laboratory for Remote Sensing of Environment and Digital Cities, Beijing, 100875, China)
4. The weather bureau of Henan province
Abstract: It is significant and necessary to estimate regional
evapotraspiration (ET) in the hydrology and water resource
research. Remotely sensed data conjunct with ground
observed data supply us a convenient approach to estimate ET.
A Surface Energy Balance System (SEBS) model was used to
estimate daily evapotranspiration in the Zhengzhou study area
in China. In order to validate SEBS model, the data observed
by Large Aperture Scintillometer (LAS) in Zhengzhou were
used. The results show that the SEBS model and MODIS data
can be effectively used to estimate daily ET.
Key words:
LAS
1. Introduction
evapotranspiration, SEBS model, MODIS,
Evapotranspiration (ET) includes transpiration from
vegetation and evaporation from soil and water, which relates
to^ the: energy. and mass. transfer. in the
soil-vegetation-atmosphere system. ET has been widely
applied in the field of agriculture, forestry and water resource
research. In early time, Thornthwait and Holzman (1944),
Monteith (1963) et al. put forward the ways to estimate the ET
from climate data. Remotely sensed data provides information
such as reflectance, surface temperature in large area, which
makes estimation of area ET applicable. The objective of this
study is to estimate daily ET with MODIS data and ground
observed meteorological data.
The study area locates in the east of China between 32?N —
37°N and 112.5°E—117.5°E (Figure 1). It includes south of
Hebei province, southeast of Shanxi province, east of Henan
province, west of Shandong province and northwest of Anhui
province. Most of the study area is plane with large area
croplands (Figure 2), the altitude from 0 to 200 m. In part of
the northwest, northeast and west area, the altitude ranges
from 750 to 2000 m.
ISPMSRS 2005 Conference Proceedings, Beijing, China
Figure 1. The map of the study area
Natural vegetation
Croplands
Urban and built
Cropland/natural
vegetation mosaic
: B Water bodies
Figure 2. The land cover map of study area from MODIS data
2. Data
MODIS (Moderate Resolution Imaging Spectroradiometer)
is a key instrument aboard the Terra (EOS AM) and Aqua
(EOS PM) satellite. The 16-day albedo, 16-day NDVI, daily
land surface temperature/emissivity and landcover data in
2001 were used, which are acquired from MODIS L4 level
land data sets. The resolution is 1 km and the data were
reprojected to Albers Conical Equal Area projection.
The ground observed data include the climate data from 31
weather stations and Large Aperture Scintillometer (LAS)
data from Zhengzhou weather station. The climate data
include daily wind speed, riaximum, minimum and mean
