Interdecadal changes in the frequency of winter extreme cold events in North China during 1989–2021

全球变暖背景下,极端天气气候事件的变化受到关注.本文研究发现, 1989-2021年期间,华北地区极端冷日数在2003和2013年发生了年代际变化.极端冷日数先增加后减少. 2003-2012年,西伯利亚-乌拉尔高压偏强,极地西风急流偏弱,有利于冷空气南下入侵华北地区,华北极端冷日数偏多.而在1989-2002年和2013-2021年,情况相反.虽然三个时段华北极端冷日的强度没有显著差异,但与其相联系的冷空气强度变得更强, 2013-2021年冷空气中心区域往西北扩张到了贝加尔湖以西地区.

Interdecadal changes in the western Siberian summer mean and extreme rainfall during 1982-2021

本文研究发现,西西伯利亚夏季降水在1995年后显著增加,2012年后又有所减少,极端降水日数和强度呈现一致的变化特征.伴随这两次降水的年代际增加/减少,西西伯利亚上空出现异常气旋/反气旋和水汽幅合/幅散.极端降水发生时的区域环流特征在三个时段基本一致:西西伯利亚低空出现气旋性异常,高空为西北-东南向的异常气旋-反气旋偶极子型.1995-2011年期间,极端降水日数更多,强度更强,上述异常环流型也更强.

Estimation of Potential Habitat of Caragana acanthophylla in Xinjiang Based on Maximum Entropy Model

[Objectives]To determine the potential habitat range of Caragana acanthophylla in Xinjiang.[Methods]The known distribution points of C.acanthophylla were used as samples,and a MaxEnt model was developed based on their climatic variables to identify key environmental factors affecting the potential habitats of C.acanthophylla through jackknife method and construction of a response relationship between representative variables and habitat suitability;the suitability of habitats for C.acanthophylla in Xinjiang was evaluated based on the output results of the model.[Results](i)The accuracy of the model verified by AUC curve was 0.971,indicating that the potential habitats of C.acanthophylla in Xinjiang predicted by MaxEnt model were highly credible.(ii)The optimum climatic characteristics for the distribution of C.acanthophylla in Xinjiang were:isothermality 18.8%-34%,minimum temperature of coldest month-30℃to-13℃,mean temperature of coldest quarter-18℃ to-4℃,annual precipitation 80-410 mm,precipitation of driest month 0-25 mm,precipitation of driest quarter 0-82 mm,and precipitation of coldest quarter 0-75 mm.(iii)The total potential distribution area of C.acanthophylla in Xinjiang was modeled to be 1.03×10^(5) km^(2),of which 8.54×10^(3)km^(2) was high suitability area,mainly in the front mountain belt of the north slope of Tianshan Mountain in Urumqi City,Changji Hui Autonomous Prefecture,Bortala Mongol Autonomous Prefecture,and Yili Kazak Autonomous Prefecture and the front mountain belt of Barluk Mountain in Tacheng Prefecture.[Conclusions]This study is of great significance for the future scientific management,regeneration,vegetation restoration and ecological protection of C.acanthophylla.

Influence of Internal Decadal Variability on the Summer Rainfall in Eastern China as Simulated by CCSM4

The combined impact of the Pacific Decadal Oscillation （PDO） and Atlantic Multidecadal Oscillation （AMO） on the summer rainfall in eastern China was investigated using CCSM4. The strongest signals occur with the combination of a positive PDO and a negative AMO （＋PDO- AMO）, as well as a negative PDO and a positive AMO （-PDO ＋ AMO）. For the ＋PDO- AMO set, significant positive rainfall anomalies occur over the lower reaches of the Yangtze River valley （YR）, when the East Asian summer monsoon becomes weaker, while the East Asian westerly jet stream becomes stronger, and ascending motion over the YR becomes enhanced due to the jet-related secondary circulation. Contrary anomalies occur over East Asia for the -PDO ＋ AMO set. The influence of these two combinations of PDO and AMO on the summer rainfall in eastern China can also be observed in the two interdecadal rainfall changes in eastern China in the late 1970s and late 1990s.

A tripole winter precipitation change pattern around the Tibetan Plateau in the late 1990s

Classical monsoon dynamics considers the winter/spring snow amount on the Tibetan Plateau(TP)as a major factor driving the East Asian summer monsoon(EASM)for its direct influence on the land-sea thermal contrast.Actually,the TP snow increased and decreased after the late 1970s and 1990s,respectively,accompanying the two major interdecadal changes in the EASM.Although studies have explored the possible mechanisms of the EASM interdecadal variations,and change in TP snow is considered as one of the major drivers,few studies have illustrated the underlying mechanisms of the interdecadal changes in the winter TP snow.This study reveals a tripole pattern of change,with decreased winter precipitation over the TP and an increase to its north and south after the late 1990s.Further analyses through numerical experiments demonstrate that the tropical Pacific SST changes in the late 1990s can robustly affect the winter TP precipitation through regulating the Walker and regional Hadley circulation.The cooling over the tropical central-eastern Pacific can enhance the Walker circulation cell over the Pacific and induce ascending motion anomalies over the Indo-Pacific region.These anomalies further drive descending motion anomalies over the TP and ascending motion anomalies to the north through regulating the regional Hadley circulation.Therefore,the positive-negative-positive winter precipitation anomalies around the TP are formed.This study improves the previously poor understanding of TP climate variation at interdecadal timescales.

Relative contribution of the anthropogenic forcing and natural variability to the interdecadal shift of climate during the late 1970s and 1990s

Global warming accelerated after the late1970 s and slowed down after the late 1990 s, accompanying the significant interdecadal changes in the regional climate.We hypothesized that the interdecadal changes linearly consisted of two independent components, anthropogenic forcing and natural decadal variability, which can be represented simply by the radiative forcing effect of carbon dioxide (RFCO_2) and the Pacific Decadal Oscillation(PDO), respectively. The combined effect of the RFCO_2 and PDO could explain the majority of the surface temperature changes during the late 1970 s and 1990 s, but the magnitudes of the relative contribution of the RFCO_2 and the PDO are inconsistent in different regions. For both the surface temperature and geopotential height, the RFCO_2 could induce significantly positive anomalies over almost the entire globe for these two shifts, exhibiting a larger magnitude in the mid–high latitudes and in the late 1990 s shift.The PDO could induce opposite anomalies for the two interdecadal shifts due to its phase transitions(negativepositive–negative). Furthermore, for the shift in the late 1970s, both the RFCO2(53.7 %–66.7 %) and the PDO(33.3 %–46.3 %) were important in regulating the tropical geopotential height, whereas the RFCO_2 dominated the changes in the mid-latitudes. For the western Pacific subtropical high, the RFCO2(PDO) could explain 52.3 %–62.1 %(37.9 %–47.7 %) of the change. The negative effect of the PDO counteracted most of the RFCO_2 effects for the late 1990 s shift.

NLP1 reciprocally regulates nitrate inhibition of nodulation through SUNN-CRA2 signaling in Medicago truncatula

Most legume plants can associate with diazotrophic soil bacteria called rhizobia,resulting in new root organs called nodules that enable N2 fixation.Nodulation is an energy-consuming process,and nodule number is tightly regulated by independent systemic signaling pathways controlled by CLE/SUNN and CEP/CRA2.Moreover,nitrate inhibits legume nodulation via local and systemic regulatory pathways.In Medicago truncatula,NLP1 plays important roles in nitrate-induced inhibition of nodulation,but the relationship between systemic and local pathways in mediating nodulation inhibition by nitrate is poorly understood.In this study,we found that nitrate induces CLE35 expression in an NLP1-dependent manner and that NLP1 binds directly to the CLE35 promoter to activate its expression.Grafting experiments revealed that the systemic control of nodule number involves negative regulation by SUNN and positive regulation by CRA2 in the shoot,and that NLP1’s control of the inhibition of rhizobial infection,nodule development,and nitrogenase activity in response to nitrate is determined by the root.Unexpectedly,grafting experiments showed that loss of CRA2 in the root increases nodule number at inhibitory nitrate levels,probably because of CEP1/2 upregulation in the cra2 mutants,suggesting that CRA2 exerts active negative feedback regulation in the root.

A 2D Metal-Organic Framework Based on 9-（Pyridin-4-yl）-9H- carbazole-3,6-dicarboxylic Acid： Synthesis, Structure and Properties

A metal-organic framework （MOF） formulated as [Cd2（μ3-L）2（DMF）4]·H2O （CdL） [H2L=9-（pyridin-4-yl）- 9H-carbazole-3,6-dicarboxylic acid, DMF=N,N-dimethylformamide] was synthesized under solvothermal condition. Crystal structural analysis reveals that CalL features the layered 2D framework with L2- ligands as 3-connected nodes. The compound CdL emits blue-violet light with the narrow emission peak and the emission maximum at 414 nm upon excitation at the maximum excitation wavelength of 340 nm. The compound CalL has a similar emission spectrum curve to the free H2L ligand that indicates the emission of compound CdL should be originated from the coordinated L2 ligands.

A water-stable metal-organic framework as a luminescent Fe^(3+) sensor under weak acidic and weak basic conditions

A three-dimensional （3D） metal-organic framework （MOF） ZnL＇O.5H20＂O.75DMF （H2L=9-（pyridin-4-yl）-9H-carbazole- 3,6-dicarboxylic acid, DMF=N,N-dimethylformamide） has been synthesized under solvotherrnal condition. Crystal structure analysis shows that, in ZnL, each dinuclear Zn2（COO）2 unit is doubly-bridged to the other two by the carbazole moieties to form the 1D chains, which are further connected together by pyridine moieties to lead to the 3D framework. ZnL exhibits both high structural stability and good luminescent stability in water with the pH range of 4-10. ZnL displays the luminescent quenching response for Fe3＋ in water with good linear correlation between the quenching efficiency and the concentration with Ksv of 10800 M 1 in the low concentration range of 0-0.1 mM. Interestingly, it is observed that the sensing performance for Fe3＋ is stable in the pH range of 4-9, enabling ZnL to detect Fe3＋ ions in weak acidic and weak basic solutions.