## 1 Introduction  
Chlorophyll Fluorescence (ChLF) is regarded as a prospective marker of vegetation photosynthetic activity and a vital indicator of the carbon cycle. Leaf chlorophyll molecules capture light energy and transmit it to the reaction centers to release through three pathways:photochemistry to drive photosynthesis, non-photochemical quenching (NPQ, i.e., thermal energy dissipation) and a small part re-emitted as ChlF [1; 2]. The physics-physiology mechanism linking the photosynthetic function to ChlF indicates that the fluorescence can be an observable and valid indicator of vegetation photosynthetic activity. With the recent advancements in remote sensing techniques, solar-induced chlorophyll fluorescence (SIF) can be detected by remote sensing instruments and has been found to be correlated with gross photosynthetic carbon dioxide (CO\({}_{2}\)) assimilation or gross primary production (GPP) at the canopy and landscape scales [3; 4; 5; 6]. Numerous satellite missions provide space-borne SIF datasets, including GOSAT [7], GOME-2 [8], SCIAMACHY [9], OCO-2 [10], TROPOMI [11] and TANSAT [12]. Therefore, the application of fluorescence signals to derive plant photosynthesis for regional and global carbon cycle research has received increasing attention. However, those satellite sensors only provide SIF data as passage grids, with a spatial resolution of at most several kilometers and unsatisfactory space coverage. Global satellite-based SIF data are only aggregated to biweekly and monthly at a coarse spatial resolution of \(1^{\circ}\) and \(0.5^{\circ}\) (e.g., OCO-2 and GOME-2). Spectroradiometer systems, which offer continuous tower-based SIF measurements at the canopy level, have gradually popularized. The systems semi-synchronously measure solar irradiance and plant canopy radiance for calculating the canopy SIF signals. Tower-based SIF observation systems include FluoSpec [6; 13], AutoSIF [14], FloX [15], PhotoSpec [16], FAME [17] and SIFspec [18], offering an opportunity to bridge the measurement gap between satellites and carbon flux towers. ChinaSpec, a network of collaborating sites to conduct ground-based continuous SIF measurements along with flux for ecosystem research, has founded starting in 2016 and been used to assist in the validation of fluorescence models and satellite SIF products [19]. However, the distribution of these sites is still too limited to verify the satellite SIF data for multi-biome and large-scale studies so far. Thus, more SIF data resources are still needed for the verification of satellite observations and the corroboration of its correlation with photosynthesis. Process models have been considered to be helpful approaches for quantifying the ecosystem processes and supplementing the limited practical measurements. SCOPE (Soil Canopy Observation Photosynthesis Energy) model [20] has been used provoribally as an essential tool for estimating continuous SIF and exploring fluorescence-photosynthesis linkages at different temporal scales. Holding a complete physiological expression of photosynthesis and fluorescence process, SCOPE has been considered to be a robust and reliable model for comprehending SIF and photosynthetic status in numerous research [21; 22; 23]. However, SCOPE model requests lots of input data, including leaf traits, leaf biochemical, canopy structure, meteorology and geometry, which might be difficult to obtain fully. SIF has usually been found sensitive to leaf chlorophyll content (Cab) and leaf area index (LAI) by a global sensitivity analysis using the SCOPE model [24]. Depending on that, an approach for estimating SIF at landscape and seasonal scale was established using the empirical non-linear logarithmic relationship between SIF and a product of Cab and LAI (i.e., canopy chlorophyll concentration, CCC) [25].