Wei Liu

The half‐precession cycle is a key climatic signal in global climate system, linking high‐ and low‐latitude climate variability and bridging orbital‐ and millennial‐scale climate changes. While it characterizes tropical insolation, its origin in high‐latitude climate records remains unclear. Based on a transient climate simulation spanning the past 800,000 years, here we find that in response to astronomical forcing, the eccentricity‐modulated half‐precession cycle emerges as an evident signal in the winter Arctic sea ice variability. It is driven by the combined influence of summer insolation at northern high latitudes and winter northward atmospheric heat transport, with the latter being primarily regulated by winter insolation at low latitudes. Moreover, the half‐precession cycle in winter Arctic sea ice leaves a distinct imprint on Arctic Ocean surface albedo as well as upward heat and moisture fluxes, which may serve as an important mechanism to explain the half‐precession signal observed in high latitudes.

Volcanic eruptions have been the most dominant natural forcing of climate change over the past millennium, affecting temperature change at multiple timescales. However, how volcanic eruptions affect regional temperature variability on the decadal timescale remains unclear. We analyzed the bidecadal effects of volcanic eruptions in the mid‐fifteenth century on two representative regions (the Tibetan plateau [TP] and the Arctic) in the Northern Hemisphere by combining proxy reconstructions, model ensemble simulations, and model sensitive experiments. The results show that the TP experienced bidecadal cooling during the mid‐fifteenth century as a result of the long‐term heat uptake in the midlatitude ocean that reduced latent heat transfer to the atmosphere. A positive sea ice–albedo feedback led to a bidecadal summer temperature decrease in the Arctic comparable to that on the TP, whereas the Arctic winter experienced stronger bidecadal cooling caused by a reduced ocean–atmosphere energy exchange and atmospheric poleward energy transport. In addition, our results show that it took ∼20 years for the temperature in these two regions to return to the level that existed before the first eruption, and this was linked to the strengthening of the Atlantic Meridional Overturning Circulation and ocean heat transport.

A high performance liquid chromatography( HPLC) method was established for the fast,and precise determination of ten nucleosides in Fritillariae Cirrhosae Bulbus and its counterfeits. Then multivariate statistical analyses,such as clustering analysis,principal component analysis( PCA),and Fisher' s linear discriminant analysis( LDA),were conducted to establish a discriminant function model for an integrated analysis. The results indicated that data acquisition time of a single sample was shortened within 16 min by the HPLC method. In the range of 5-1 000 mg·kg~(-1),the mass concentrations of all nucleosides exhibited good linear relationships with the corresponding peak areas( R2> 0. 999). The spiked recoveries were in the range of 93. 83%-108. 9% with RSDs of0. 12%-1. 3%( n = 5). The limit of quantitation( LOQ) was 0. 98-4. 13 mg·kg~(-1). As revealed by the clustering analysis,Fritillariae Cirrhosae Bulbus and the counterfeits could be discriminated into two clusters based on the content of nucleosides. Fisher's LDA could achieve this discrimination,while PCA dimension reduction failed. The accuracy of the discriminant function model established on the screened characteristic indicators reached 97. 5%. The present study proposed a new identification method of Fritillariae Cirrhosae Bulbus with one-dimensional indicators,which is simple,accurate,and reliable. It can provide a scientific basis for further optimizing the identification techniques for Fritillariae Cirrhosae Bulbus and inspiration for quality control strategy development of Chinese medicinal materials.