Numerical Investigation of Climate Factors Impact on Carbon Cycle in the East Asian Terrestrial Ecosystem

Using a regional climate model that includes a terrestrial biosphere model, numerical simulations were performed to clarify the mechanism of the carbon cyclebetween the terrestrial ecosystemand the atmosphere and to investigate the climate factors impact on the carbon cyclein the East Asian terrestrial ecosystem.Model verifications were performed with regard to the principal elements: precipitation and vegetation phenology. The variations of the atmospheric carbon dioxide concentration simulated by the model were validated using the data at six in situ observatories.After the confirmations of the model performance, regional features of the impact of climate factors on the gross primary production (GPP) were analyzed. The downward short-wave radiation (DSW), the soil wetness (SW), and the surface temperature (TA) were chosen as the effective climate factors. In the NE-Asia region, a positive anomaly of DSW in warm season induces a positive anomaly of GPP. High anomalous TA in the cold season also induces a large value of GPP. In the China region, similarly to that in NE-Asia, DSW is important for GPP. The effect of SW is also important in the spring. While the correlation between the variation of TA and that of GPP is positive and high in winter, the positive anomaly of TA in the warm season induces negative anomaly of GPP. In the Indochina region, DSW is important throughout the year. In contrast, the correlations between the variations of SW and those of GPP are negative in all seasons, indicating that GPP becomes a negative anomaly when the precipitation is a positive anomaly. In the India region, DSW in the warm season and SW in the cold season are important for increasing GPP. In the Mongolia and Inland regions, SW is a more important climate factor than DSW for GPP. High temperature in the cold season is also important. In summer, unusually high temperature and dry climateconditions reduce GPP. In the Philippines region, main factor affecting GPP is DSW.