Temporal Duration of the East Asian Summer Monsoon Substantially Affects Surface Energy Exchange over the Summer Monsoon Transition Zone of China

Abstract

Investigating the response of land surface energy exchange to key climatic signals such as the East Asian summer monsoon (EASM) is essential for understanding the intensive interactions in the Earth system. This study focuses on the summer monsoon transition zone (SMTZ) in China, which has a climate rather sensitive to the EASM activity, and examined the response of land surface energy exchange over the SMTZ to summer monsoon activity. A flux evaluation of five reanalysis/modeling data sets indicates that JRA-55(the Japane 55-year Reanalysis) reasonably represents interannual variations of surface heat fluxes over the SMTZ. The EASM activity is accurately identified in the SMTZ by introducing a monsoon temporal duration index (MTDI), which presents climate variations of summer rainfall and EASM activity better than commonly used summer monsoon indexes. Based on MTDI and long-term flux data sets, it was found that the interannual fluctuation of the EASM intensively controls surface energy partitioning and turbulent heat exchange but has a weak impact on radiative processes over the SMTZ. Furthermore, surface sensible and latent heat fluxes significantly responded to the influential period of the summer monsoon, exhibiting approximately quadratic/logarithmic relationships with the MTDI. More prominent interannual variabilities of turbulent heat fluxes were observed in weak summer monsoon years, during which an active interaction between surface energy exchange and a warming and drying climate occurred. An ensemble empirical mode decomposition (EEMD) analysis confirms that EASM activity dominates the quasi-biennial and multidecadal variations of turbulent heat fluxes over the SMTZ, which may be achieved by the transport of tropical quasi-biennial and Pacific Decadal Oscillation (PDO) signals to the mid-latitudes of East Asia. The expected intensification of summer monsoon activity in the future may induce acceleration of energy and hydrological cycle and exert a substantial impact on the availability of water and the ecosystem stability over the SMTZ.

Environmental factors driving evapotranspiration over a grassland in a transitional climate zone in China

“…The energy balance of SACOL can basically reach a closed degree of more than 0.7 (Li et al, 2021), which ensures the good quality of flux observation data. In order to strictly control the quality of the observed data, the original half‐hour flux data affected by precipitation and the flux observations exceeding the threshold (net radiation: −200 to 900 W m −2 ; sensible heat: −200 to 500 W m −2 ; latent heat: −200 to 500 W m −2 ) were excluded.…”

Investigating the Coupling Relationship between Soil Moisture and Evaporative Fraction over China’s Transitional Climate Zone

“…The gross primary productivity (GPP) represents the growth of the terrestrial vegetation and was derived from the Global OCO-2 based SIF product (GOSIF). This is a new global product of solar-induced chlorophyll fluorescence [27]. The LAI was derived from the MOD15A2H version 6.1 moderate-resolution imaging spectroradiometer (MODIS).…”