## 3 Results and Discussion  
### Temporal Variation of Hydrometeorological Conditions  
Figure 2 the shows time series of the hydrometeorological variables (_i.e._, precipitation, soil water content, vapor pressure deficit (VPD), and air temperature) to understand the algorithms of the GPP and ET. The temporal variation of the soil water content was similar with that of the precipitation in both 2007 and 2008 (Figure 2). The maximum precipitation was occurred from July to August (_i.e._, from 200 to 250 day of year) and the air temperature was also high during this period (Figure 3).  
These results were supported by the many previous studies. [PERSON] _et al_. [18] analyzed the temporal variation of hydrometeorological variables at three sites (CBS, QYZ, and DHS) in eastern China. Among these sites, the CBS site showed that precipitation, air temperature, soil water content, and VPD were synchronous. Their results showed the similar trends with our results because CBS and our study site, GDK are characterized as dense forest ecosystems which include the monsoon climate region [46, 47]. [PERSON] _et al_. [48] investigated the effect of climate change on the thermal structure of lakes in response to watershed hydrology and showed the similar tendency between precipitation and air temperature in the Asian monsoon climate region. [PERSON] _et al_. [49] discussed temporal variation of rainfall and showed the positive correlation between rainfall and soil moisture. Inversely, other two  
Figure 3: Temporal variation of air temperature (T\({}_{\text{a}}\)) and saturated vapor pressure deficit (VPD) at GDK site in South Korea.  
Figure 2: Temporal variation of precipitation and soil water content (SWC) at depth of 10, 30, and 60 cm at GDK site in South Korea.  
sites, the QYZ and the DHS introduced in [PERSON] _et al_. [18], showed frequently seasonal drought resulting in low efficiency of water use in a subtropical forest ecosystem in eastern China. Their results indicated that the seasonal distribution of precipitation, air temperature, and soil water content were asynchronous. Their results also specified that the precipitation decreased, to some degree, whereas the air temperature reached its maximum as the vapor pressure deficit (VPD) increased significantly. For this reason, we know that the carbon absorption and vegetation growth were controlled by the activities of this meteorological variable.  
The seasonal trends of ground measured GPP and ET showed similar pattern with air temperature as shown in Figure 4. In dormant season (from DOY 1 to 100 and 300 to 365), air temperature showed high variability while GPP and ET were generally stable by non-vegetation activities. Conversely, these variables showed active variation caused by vegetation activities in growing season (from DOY 100 to 300). Comparison of air temperature with GPP and ET showed that GPP and ET had many spike data which was affected by atmospheric condition such as cloud effects. This spike data was removed by adopting of the various calibration methods. The temporal variation of VPD was in good agreement with ground-based GPP and ET as shown in Figure 5. Generally, variables in Figure 5 showed the similar trends with those in Figure 4. The hydrometeorological variables of Figures 4 and 5 were closely related to the ground measured GPP and ET.