## 1 Introduction
However, it is still unclear whether and how these altitudinal factors influence photosynthesis-related traits and the sensitivity of these traits to environmental changes, and different results may be obtained in different regions [2]. While previous studies based on field investigations discovered altitudinal variations in the photoproduction strategies, photosynthetic parameters, and biochemical composition of the photosynthetic apparatus [13; 16; 17], the insufficient representativeness of field investigation limits the applicable range of these conclusions. Models do contribute to explaining photosynthetic changes along the altitude [2; 14], but their oversimplified process and the complexity of the real world make it hard for them to show the diverse altitudinal patterns in the real world. Therefore, further studies are required to give an overall view of photosynthesis and its sensitivity to environmental changes at the ecosystem scale. Gross primary production (GPP) estimation products provide an opportunity to study photosynthesis productivity directly, but they are still insufficient to capture the spatial distribution of photosynthesis in some places. For instance, the data-driven FLUXCOM GPP products, derived from observations of the global micrometeorological flux site network (FLUXNET), is considered to be biased when applied to alpine regions, because the network's EC towers are generally located in the temperate zone of the northern hemisphere below 1000 m [18]. As a special photosynthesis-related physiological trait detectable from remote distances, solar-induced chlorophyll fluorescence (_SIF_) has paved the way for research on altitudinal variations in the physiological status of alpine vegetation at large scale. Linked with light reaction in the photosynthetic process, _SIF_ is emitted by light-inspired chlorophyll molecules and contains photosynthesis-related physiological information in addition to absorbed light information. Thus, it is able to reflect photosynthetic-related physiological responses of alpine vegetation to the environment. Numerous satellite-based _SIF_ products have been developed [19; 20; 21; 22; 23; 24] since the first satellite-based _SIF_ retrieval in 2007 [25], which is valuable in places that lack ground observations, such as alpine regions. _SIF_ contains information on both incident light intensity and plant properties, whereas _SIF_\({}_{yield}\), derived from _SIF_ normalized by absorbed photosynthetically active radiation (_APAR_), can be used to reflect photosynthetic traits of plants [26] as well as their responses to environmental stress [27; 28]  
Previous studies have observed the effect of altitude on photosynthesis in various regions by various methods, and their results involved different latent factors and revealed different mechanisms [1]. Here, based on the Global Ozone Monitoring Experiment 2 (GOME-2) satellite-based _SIF_ dataset on the Tibetan Plateau meadow, we aim to (1) investigate and compare the relationship between altitude and \(SIF_{yield}\) from different perspectives, which may involve the influence of vegetation adaptation, seasonal changing factors, and interannual environmental changes; (2) find whether there is variation in the temperature sensitivity of \(SIF_{yield}\) along the altitude gradient; and (3) find the spatial distribution of temperature sensitivity in the study area and compare the temperature sensitivity of \(SIF_{yield}\) to seasonal changes and to interannual changes, which may help us find areas that need extra attention in the context of global change.