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The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008 
2. STUDY SITE AND DATA 
The Tongyu observation site consists of two stations (figure 1) 
that are maintained by the Institute of Physics of Jilin province, 
Chinese Academy of Sciences. The stations are 5 km apart and 
located at Tongyu, Northeastern China (44.416N, 122.867E, 
elevation 184 m), on a flat Songliao plain. The area is semi-arid 
with a mean annual precipitation of 388 mm in Tongyu County, 
about 30 km northeast of the site. Precipitation totals are highly 
variable from year to year. Approximately 80% of precipitation 
occurs between May and September. The mean annual air 
temperature in Tongyu County is 5.70 °C . This experiment 
provided data at two nearby sites, the so-called Tongyu- 
cropland (TY-crop) and Tongyu-grassland (TY-grass), from 
October 2002 to September 2003. TY-crop was a flat cropland 
and TY-grass was flat and degraded grassland in the summer 
season, but they turned to bare soils in the winter season. Only 
the cropland station data was used in this study. The main crops 
within 1 km of the measurement location are com and 
sunflower, which achieve a height of 2 m during the growing 
season. The ground is partly bare in the winter. Soils are 
described as sandy, salty alkaline, black humus, or meadow soil. 
Turbulence measurements are taken by the ultra-sonic 
anemometer/thermometer at 3.5 m and an open-path infrared 
gas analyzer. Volumetric soil moisture content is measured 
using time domain reflectometry at 5, 10, 20, 40, 80 and 160 cm. 
Meteorological measurements are made from a 20-meter tower. 
Radiation measurements are made at 3 m height, 20 m away 
from the tower. More detailed description of the site can be 
found in the CEOP dataset documentation available at 
http://www.eol.ucar .edu/projects/ceop/dm/documents/rsite/.[6] 
Figure 1: Location of the study area in Google Earth, Jilin province, China. The upper right panel shows cropland picture in the 
study site(09-10-2003). The lower right panel shows the location of the eddy covariance system for sensible and latent. 
3. MODEL DESCRIPTION 
In order to define the upper boundary condition of mixture layer 
using air temperature which can be inferred from surface 
radiometric temperature using remote sensing, a time-integrated 
mixture layer model is coupled with a SVAT model. This 
combination requires no more air temperature as input, and is 
less sensitive to system errors in the surface temperature 
derivation. A brief overview of the two parts of this model is 
giving, when sensible heat flux converges from the comparison 
in both PBL and SVAT model, latent heat estimation could be 
possible based on the energy balance equation. 
3.1 Time-Integrated PBL Development Components 
We represent the convective PBL as a well-mixed slab of air. 
Above the PBL is the free atmosphere with specified potential 
temperature . Air from these levels is progressively 
entrained into the PBL, where it is instantaneously mixed as the 
PBL grows. McNaughton and Spriggs give a simplified 
conservation equation describing the growth of a convective 
boundary layer over time [7], neglecting the effects of 
subsidence and horizontal advection: 
p c p { z 2 0„,2 - 2 A.y ) = J(*)dt+pc p £ 2 e s ( z )dz ( 1 ) 
During the time interval from to ^ ,the top of the mixed layer 
z z 
rises from height 1 to 2 , and the potential temperature 
0 0 
within the mixed layer rises from m - 1 to . Such conservation 
equation is limit to clear-sky conditions. In order to make the 
sensible heat flux less sensitive to potential temperature profile 
and mixture layer height, the surface temperature measurement 
should happen at the time when large increase in sensible heat 
goes with large temperature-change and relative-limited 
boundary height variation. 
3.2 SVAT Components