Distinctive impacts of atmospheric intraseasonal oscillations on the net ecosystem exchange of the southeastern China forest between spring and summer

Abstract

The southeastern China (SEC) forest is an important terrestrial biospheric carbon sink in the global carbon cycle, with its total net ecosystem exchange (NEE) accounting for about 3.2% of the global forest NEE. The prevailing atmospheric intraseasonal oscillations (ISOs) over East Asia strongly modulate climatic conditions over the SEC during spring and summer, thus leading to significant ISOs in the NEE of the SEC forest. As atmospheric ISOs show strong seasonality, this study examined the distinctive impacts of atmospheric ISOs on the NEE of the SEC forest between spring and summer.During spring, the vertical coupling of 10–30-d atmospheric ISOs in the lower and upper troposphere leads to strong 10‒30-d ISOs of solar radiation and temperature over the SEC. The 10‒30-d ISOs of solar radiation and temperature further result in the 10‒30-d ISOs of gross primary productivity (GPP) and terrestrial ecosystem respiration (TER). With the covariation in GPP and TER, the NEE of the SEC forest exhibits significant 10‒30-d ISOs. In contrast, the intraseasonal variations in climatic conditions over the SEC are associated with the 15‒60-d tropical atmospheric ISO during summer. While the induced 15‒60-d ISO of solar radiation leads to that of GPP, the induced 15‒60-d ISO of temperature is small and less effective; thus, the 15‒60-d ISO of NEE mainly originates from that of GPP.