广东国家储备林树种湿加松、桉树的经济效益分析

国家储备林建设是一项投资期相对较长的建设项目,财务评价是投资决策中必不可少的重要内容。湿加松和桉树是广东重要的国家储备林树种,运用财务盈利能力分析方法分别对湿加松和桉树的项目投资可行性和经济合理性进行计算,得出湿加松和桉树的财务净现值为正值,且财务内部收益率较林业行业基准收益率高。可见,湿加松和桉树可作为储备林基地建设推荐的经营树种。同时,采用单因素敏感性分析方法,对影响财务内部收益率的各因子进行敏感性分析,结论显示,经营湿加松和桉树都具有一定的抗风险能力。

广东省杉木生长适宜性及分布预测

为科学指导广东杉木经营,依据森林资源清查数据,使用最大熵模型、ArcGIS技术和数理统计方法,研究杉木分布与生态环境因子的关系,预测杉木在当前与未来不同时期的潜在适生区,比较SSP126、SSP585气候模式下杉木适生区的变化趋势。结果表明:当前广东省杉木适生区分布范围广,高适生区主要集中在广东省北部区域。影响广东杉木分布的主要环境因子为海拔、最暖季度平均气温、气温季节变化标准差、最湿季度平均气温和最干月份雨量。当海拔≥235 m、最暖季度平均气温为19.4~27.1℃、气温季节变化标准差为620~800、最湿季度平均气温为15~24℃、最干月份雨量为35.2~52.1 mm时,最适合广东省杉木生长。随着未来气候的变化,广东省杉木适生区总体出现收缩趋势,杉木高适生区往高海拔区域聚集缩减,其中在SSP585气候模式下收缩的程度比SSP126气候模式大,杉木生境破碎化严重。

2001~2016年泛北极地区过火面积的时空变化特征

泛北极地区(50°N以北陆地)是全球两大火灾带之一,该地区火灾不仅影响局地植被演替,还影响区域乃至全球的碳循环及气候。以往研究主要针对泛北极某一特定区域火灾、个别极端大火事件或者某一特定陆表类型燃烧,对泛北极区域火灾特征尚缺乏全面认识。本研究使用3套卫星反演的全球火产品数据(GFED4.1s、MODIS C6、FireCCI51),深入研究2001~2016年泛北极过火面积的时空变化特征。结果表明泛北极地区多年平均的过火面积为7.47±0.72Mha/a,大值区主要位于阿拉斯加、加拿大中部、西伯利亚南部和中东部。泛北极过火面积的年际变率大;此外,泛北极和泛北极北美地区森林过火面积均呈现显著增大趋势,而泛北极欧洲地区农田过火面积显著减小。泛北极地区火灾主要发生在春季和夏季,但燃烧的主要陆表类型不同:多年平均而言,泛北极北美地区以夏季稀树草原和森林燃烧为主,泛北极欧洲地区以春季农田燃烧和夏季森林燃烧为主,泛北极亚洲地区以夏季森林、灌木燃烧和春季农田、森林燃烧为主。不同地区年过火面积极端大值年对应的主要陆表燃烧类型与多年平均结果类似。

不同基质和生长调节剂对乡土植物扦插生根的影响

在温室条件下,采用不同质量浓度ABT2号生根粉对蔓花生(Arachis duranensis)、碰碰香(Plectranthus tomentosa)和四季秋海棠(Begonia semperflorens)进行扦插试验,结果表明:质量浓度为100 mg/L的ABT2号生根粉溶液可以提高蔓花生的成活率;碰碰香在ABT2号生根粉为300 mg/L时比较容易生根;不同质量浓度ABT2号生根粉对四季秋海棠的生根没有显著影响,说明四季秋海棠比较容易生根。采用3种基质对天胡荽(Hydrocotyle sibthorpioides)、锦绣苋(Alternanthera bettzickiana)和铺地锦竹草(Callisia repens)进行扦插生根研究发现:天胡荽在田园土基质和泥炭土+珍珠岩基质中均有较好的生根效果;锦绣苋和铺地锦竹草均在泥炭土+珍珠岩基质中的生根效果最好。

Predictability of the Summer East Asian Upper-Tropospheric Westerly Jet in ENSEMBLES Multi-Model Forecasts

The interannual variation of the East Asian upper-tropospheric westerly jet （EAJ） significantly affects East Asian climate in summer. Identifying its performance in model prediction may provide us another viewpoint, from the perspective of uppertropospheric circulation, to understand the predictability of summer climate anomalies in East Asia. This study presents a comprehensive assessment of year-to-year variability of the EAJ based on retrospective seasonal forecasts, initiated from 1 May, in the five state-of-the-art coupled models from ENSEMBLES during 1960-2005. It is found that the coupled models show certain capability in describing the interannual meridional displacement of the EAJ, which reflects the models＇ performance in the first leading empirical orthogonal function （EOF） mode. This capability is mainly shown over the region south of the EAJ axis. Additionally, the models generally capture well the main features of atmospheric circulation and SST anomalies related to the interannual meridional displacement of the EAJ. Further analysis suggests that the predicted warm SST anomalies in the concurrent summer over the tropical eastern Pacific and northern Indian Ocean are the two main sources of the potential prediction skill of the southward shift of the EAJ. In contrast, the models are powerless in describing the variation over the region north of the EAJ axis, associated with the meridional displacement, and interannual intensity change of the EAJ, the second leading EOF mode, meaning it still remains a challenge to better predict the EAJ and, subsequently, summer climate in East Asia, using current coupled models.

Intercomparison of the Impacts of Four Summer Teleconnections over Eurasia on East Asian Rainfall

East Asian summer climate is strongly affected by extratropical circulation disturbances.In this study,impacts of four atmospheric teleconnections over Eurasia on East Asian summer rainfall are investigated using National Centers for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） reanalysis data and Climatic Research Unit （CRU） land precipitation data during 1979-2009.The four teleconnections include the Scandinavian （SCA）,the Polar/Eurasian （PEU）,the East Atlantic/Western Russian （EAWR）,and the circumglobal teleconnection （CGT）.Moreover,the related changes of lower-tropospheric circulation are explored,specifically,the low pressure over northern East Asia （NEAL） and the subtropical high over the western North Pacific （WNPSH）.The results presented are in the positive phase.The PEU and SCA induce significant negative anomalies in North China rainfall （NCR）,while the CGT induces significant positive anomalies.In the past three decades,the PEU and SCA explain more than 20％ of the variance in NCR,twice that explained by the CGT,suggesting a more important role of the former two teleconnections in NCR variation than the latter one.Meanwhile,the PEU and SCA reduce rainfall in Northeast China and South Korea,respectively,and the CGT enhances rainfall in Japan.The rainfall responses are attributed to the SCA-induced northward shift of the NEAL,and PEU-induced northward shift and weakening of the NEAL,respectively.For the CGT,the dipole pattern of rainfall anomalies between North China and Japan is affected by both westward extension of the NEAL and northwestward expansion of the WNPSH.In addition,the EAWR leads to an increase of sporadic rainfall in South China as a result of the eastward retreat of the WNPSH.

Improving Multi-model Ensemble Probabilistic Prediction of Yangtze River Valley Summer Rainfall

Seasonal prediction of summer rainfall over the Yangtze River valley（YRV） is valuable for agricultural and industrial production and freshwater resource management in China, but remains a major challenge. Earlier multi-model ensemble（MME） prediction schemes for summer rainfall over China focus on single-value prediction, which cannot provide the necessary uncertainty information, while commonly-used ensemble schemes for probability density function（PDF） prediction are not adapted to YRV summer rainfall prediction. In the present study, an MME PDF prediction scheme is proposed based on the ENSEMBLES hindcasts. It is similar to the earlier Bayesian ensemble prediction scheme, but with optimization of ensemble members and a revision of the variance modeling of the likelihood function. The optimized ensemble members are regressed YRV summer rainfall with factors selected from model outputs of synchronous 500-h Pa geopotential height as predictors. The revised variance modeling of the likelihood function is a simple linear regression with ensemble spread as the predictor. The cross-validation skill of 1960–2002 YRV summer rainfall prediction shows that the new scheme produces a skillful PDF prediction, and is much better-calibrated, sharper, and more accurate than the earlier Bayesian ensemble and raw ensemble.

Improvement of the simulation of the summer East Asian westerly jet from CMIP5 to CMIP6

The East Asian westerly jet(EAJ)plays a crucial role in affecting the East Asian summer rainfall(EASR).Therefore,evaluations of EAJ simulations are vital for improving the understanding and projections of climate change in East Asia.This study evaluates the simulations of the climatology and interannual variability in the present-day summer EAJ in the CMIP6 models and compares the results with those in the CMIP5 models by analyzing the historical climate simulations of 29 CMIP5 models and 21 CMIP6 models during the period from 1986–2005.In general,the CMIP6 models capture the EAJ more realistically than the CMIP5 models.The results show that the CMIP6 models reasonably capture the spatial features of the climatological zonal wind at 200 hPa and simulate a smaller zonal wind bias along the EAJ.The locations of the EAJ’s core are at the observed location in nearly all CMIP6 models but in only approximately two-thirds of the CMIP5 models.The EAJ’s intensity is closer to the observed value and exhibits a smaller intermodel dispersion in the CMIP6 models.The CMIP6 models also show an improved ability to reproduce the interannual variability in the EAJ’s meridional displacement and have a stronger relationship with the EASR.

Circulation anomalies associated with interannual variation of early- and late-summer precipitation in Northeast China

Summer rainfall is vital for crops in Northeast China. In this study, we investigated large-scale circulation anomalies related to monthly summer rainfall in Northeast China using European Center for Medium-Range Weather Forecast ERA-40 reanalysis data and monthly rainfall data from 79 stations in Northeast China. The results show that the interannual variation in rainfall over Northeast China is mainly dominated by a cold vortex in early summer (May-June) and by the East Asian summer monsoon in late summer (July-August). In early summer, corresponding to increased rainfall in Northeast China, an anomalous cyclonic anomaly tilted westward with height appears to the northwest and cold vortices occur frequently. In late summer, the rainfall anomaly is mainly controlled by a northward shift of the local East Asian jet stream in the upper troposphere and the northwest extension of the western Pacific subtropical high (WPSH) in the lower troposphere. The enhanced southwesterly anomaly in the west of the WPSH transports more moisture into Northeast China and results in more rainfall. In addition, compared with that in July, the rainfall in Northeast China in August is also influenced by a mid- and high-latitude blocking high over Northeast Asia.