基于scPDSI的东北地区气象干旱时空特征分析

干旱已成为全球陆地生态系统面临的普遍问题,其发展具有明显的地域特征,了解区域干旱的时空分布特征是防灾减灾、应对气候变化的基础。基于scPDSI数据集,采用经验正交函数和统计分析方法,分析2002-2017年东北地区气候干湿状况的时空分布和演变特征,探讨了干湿状况的季节变化对年际变化的贡献率,结果表明:东北地区4个季节的干旱面积为52.27%-62.03%,虽然季节和年际尺度的干旱均有减弱趋势,其中冬季干旱程度显著减弱,但干旱仍然是东北地区的主要气候背景;春季和夏季scPDSI的协同作用对年际scPDSI变化的贡献率达88.64%,夏季的贡献率达86.13%;东北地区的西部干旱程度高于东部的,其中呼伦贝尔草原中部和浑善达克沙地东部以严重干旱和中等干旱为主;EOF分析表明,东北地区4个季节和年度的干湿状况呈现一致的正变化趋势,高值中心主要出现在南部地区。     

1983与1985年夏季北半球500hPa高度场大气低频波的振荡特征

本文利用观测资料分析了1983与1985年夏季半球500hPa高度场大气低频波的振荡特征。结果表明，1983年（厄尔尼诺年）夏季热带中、东太平洋和印度洋以及东亚季风区上空的低频振荡比1985年（反厄尔尼诺年）夏季的低频振荡强，而热带西太平洋的情况恰好相反。这是由于反厄尔尼诺年夏季热带西太平洋对流活动强盛所致。分析结果还表明：1983年夏季低频波基本上是东传的；1985年夏季，在中高纬度地区低频波主要还是东传，热带是西传。西藏高原是大气低频振荡的汇区。     

全球越赤道气流的时空变化

本文首先通过850和200毫巴空间、时间剖面图讨论了全球越赤道气流的时空变化。在东半球夏季各月大气低层存在5条越赤道的偏南气流通道,冬季转为偏北气流,呈现了季节性的年变。在西半球,有3条偏南气流和2条偏北气流通道,它们都未呈现出季节性的年变。其次阐述了它们与环流系统的关联。索马里急流的建立与维持,看来与澳大利亚、西太平洋副高和西风的某些先期变化有关系。它们可能说明全球不同地区大气环流系统季节性变化过程存在一定的时间序列。      

气象条件对奶牛产奶量的影响及对策

在分析奶牛产奶量时间和空间分布的基础上,将乌兰浩特市全市产奶量和乌兰哈达奶牛场观测站产奶量与乌兰浩特市气象资料进行相关分析,确定了影响当地牛奶产量的关键气象因子和关键时期。结果表明,温度是当地春秋季节和冬季影响奶牛产奶量的主要限制因子,其次是气压和相对湿度,而降雨量和日照时数的影响不明显。     

A FUMIGATION DIFFUSION MODEL DURING THE MOUNTAIN-VALLEY WIND SHIFT PERIOD

The fumigation during the mountain-valley wind shift has been first identified as a special type of pol-lutant diffusion using the monitoring measurements of Dukou,Southwest Sichuan,China.Such a pheno-menon occurs frequently all year around but summer,particularly in winter months.A new model for thefumigation during the mountain-valley wind shift period is developed that allows satisfactory explanation ofthe fact.Analyses indicate that the model can more accurately predict not only the high concentration ofPollutants but the time and locality of the occurrence as well.The ground concentration of SO_2 during fumigation is several times up to over a decade higher thanthe daily mean for the whole region,one of the main contamination processes that affect the air quality ofthe city.The medel analyses provide a basis for more effective prediction of the quality and precautionstudy against the disaster.     

The potential transient dynamics of forests in New England under historical and projected future climate change

Projections of vegetation distribution that incorporate the transient responses of vegetation to climate change are likely to be more efficacious than those that assume an equilibrium between climate and vegetation. We examine the non-equilibrium dynamics of a temperate forest region under historic and projected future climate change using the dynamic ecosystem model LPJ-GUESS. We parameterized LPJ-GUESS for the New England region of the United Sates utilizing eight forest cover types that comprise the regionally dominant species. We developed a set of climate data at a monthly-step and a 30-arc second spatial resolution to run the model. These datasets consist of past climate observations for the period 1901?C2006 and three general circulation model projections for the period 2007?C2099. Our baseline (1971?C2000) simulation reproduces the distribution of forest types in our study region as compared to the National Land Cover Data 2001 (Kappa statistic?=?0.54). Under historic and nine future climate change scenarios, maple-beech-basswood, oaks and aspen-birch were modeled to move upslope at an estimated rate of 0.2, 0.3 and 0.5?m?yr^?1 from 1901 to 2006, and continued this trend at an accelerated rate of around 0.5, 0.9 and 1.7?m?yr^?1 from 2007 to 2099. Spruce-fir and white pine-cedar were modeled to contract to mountain ranges and cooler regions of our study region under projected future climate change scenarios. By the end of the 21^st century, 60% of New England is projected to be dominated by oaks relative to 21% at the beginning of the 21^st century, while northern New England is modeled to be dominated by aspen-birch. In mid and central New England, maple-beech-basswood, yellow birch-elm and hickories co-occur and form novel species associations. In addition to warming-induced northward and upslope shifts, climate change causes more complex changes in our simulations, such as reversed conversions between forest types that currently share similar bioclimatic ranges. These results underline the importance of considering community interactions and transient dynamics in modeling studies of climate change impacts on forest ecosystems.     

A brief introduction to BNU-HESM1.0 and its earth surface temperature simulations

Integrated assessment models and coupled earth system models both have their limitations in understanding the interactions between human activity and the physical earth system. In this paper,a new human–earth system model,BNUHESM1.0,constructed by combining the economic and climate damage components of the Dynamic Integrated Model of Climate Change and Economy to the BNU-ESM model,is introduced. The ability of BNU-HESM1.0 in simulating the global CO2 concentration and surface temperature is also evaluated. We find that,compared to observation,BNU-HESM1.0underestimates the global CO2 concentration and its rising trend during 1965–2005,due to the uncertainty in the economic components. However,the surface temperature simulated by BNU-HESM1.0 is much closer to observation,resulting from the overestimates of surface temperature by the original BNU-ESM model. The uncertainty of BNU-ESM falls within the range of present earth system uncertainty,so it is the economic and climate damage component of BNU-HESM1.0 that needs to be improved through further study. However,the main purpose of this paper is to introduce a new approach to investigate the complex relationship between human activity and the earth system. It is hoped that it will inspire further ideas that prove valuable in guiding human activities appropriate for a sustainable future climate.