Soil respiration in tropical seasonal rain forest in Xishuangbanna, SW China

With the static opaque chamber and gas chromatography technique, from January 2003 to January 2004 soil respiration was investigated in a tropical seasonal rain forest in Xishuangbanna, SW China. In this study three treatments were applied, each with three replicates: A (bare soil), B (soil+litter), and C (soil+litter+seedling). The results showed that soil respiration varied seasonally, low from December 2003 to February 2004, and high from June to July 2004. The annual average values of CO2 efflux from soil respiration differed among the treatments at 1% level, with the rank of C (14642 mgCO2· m-2. h-1)＞B (12807 mgCO2· m-2. h-1)＞A (9532 mgCO2· m-2. h-1). Diurnal variation in soil respiration was not apparent due to little diurnal temperate change in Xishuangbanna. There was a parabola relationship between soil respiration and soil moisture at 1% level. Soil respiration rates were higher when soil moisture ranged from 35% to 45%. There was an exponential relationship between soil respiration and soil temperature (at a depth of 5cm in mineral soil) at 1% level. The calculated Q1o values in this study,ranging from 2.03 to 2.36, were very near to those of tropical soil reported. The CO2 efflux in 2003was 5.34 kgCO2· m-2. a-1 from soil plus litter plus seedling, of them 3.48 kgCO2· m-2. a-1 from soil (accounting for 62.5%), 1.19 kgCO2· m-2. a-1 from litter (22.3%) and 0.67 kgCO2·m-2. a-1 from seedling (12.5%).     

Studies on wind environment around high buildings in urban areas

High buildings or architectural complex in urban areas remarkably distort the urban surface wind fields. As the air flow approaches,local strong wind may appear around the buildings. The strong wind makes the pedestrians on sidewalks, entrances and terrace very uncomfortable and causes the pedestrian level wind environment problem. In this studies, hot-wire wind measurement, wind scouring in wind tunnel and numerical computation were carried out to evaluate the wind environment of tall buildings in the prevailing flow conditions in Beijing areas. The results obtained by three techniques were compared and mutually verified. The conclusions drawn from three approaches agree with each other. Also the advantages and limitations of each method were analyzed. It is suggested that the combination of different techniques may produce better assessment of wind environment around high buildings.     

Study of statistically correcting model CMAQ-MOS for forecasting regional air quality

Based on analysis of the air pollution observational data at 8 observation sites in Beijing including outer suburbs during the period from September 2004 to March 2005, this paper reveals synchronal and in-phase characteristics in the spatial and temporal variation of air pollutants on a city-proper scale at deferent sites; describes seasonal differences of the pollutant emission influence between the heating and non-heating periods, also significantly local differences of the pollutant emission influence between the urban district and outer suburbs, i.e. the spatial and temporal distribution of air pollutant is closely related with that of the pollutant emission intensity. This study shows that due to complexity of the spatial and temporal distribution of pollution emission sources, the new generation Community Multi-scale Air Quality (CMAQ) model developed by the EPA of USA produced forecasts, as other models did, with a systematic error of significantly lower than observations, albeit the model has better capability than previous models had in predicting the spatial distribution and variation tendency of multi-sort pollutants. The reason might be that the CMAQ adopts average amount of pollutant emission inventory, so that the model is difficult to objectively and finely describe the distribution and variation of pollution emission sources intensity on different spatial and temporal scales in the areas, in which the pollution is to be forecast. In order to correct the systematic prediction error resulting from the average pollutant emission inventory in CMAQ, this study proposes a new way of combining dynamics and statistics and establishes a statistically correcting model CMAQ-MOS for forecasts of regional air quality by utilizing the relationship of CMAQ outputs with corresponding observations, and tests the forecast capability. The investigation of experiments presents that CMAQ-MOS reduces the systematic errors of CMAQ because of the uncertainty of pollution emission inventory and improves the forecast level of air quality. Also this work employed a way of combining point and area forecasting, i.e. taking the products of CMAQ for a center site to forecast air pollution for other sites in vicinity with the scheme of model products "reanalysis" and average over the "area".     

The diurnal and seasonal characteristics of urban heat island variation in Beijing city and surrounding areas and impact factors based on remote sensing satellite data

Based on the land surface temperature (LST), the land cover classification map,vegetation coverage, and surface evapotranspiration derived from EOS-MODIS satellite data, and by the use of GIS spatial analytic technique and multivariate statistical analysis method, the urban heat island (UHI) spatial distribution of the diurnal and seasonal variabilities and its driving forces are studied in Beijing city and surrounding areas in 2001. The relationships among UHI distribution and landcover categories, topographic factor, vegetation greenness, and surface evapotranspiration are analyzed. The results indicate that: (i) The significant UHI occur in Beijing city areas in the four seasons due to high heat capacity and multi-reflection of compression building, as well as with special topographic features of its three sides surrounded by mountains,especially in the summer. The UHI spatial distribution is corresponding with the urban geometry structure profile. The LST difference is approximately 4-6℃ between Beijing city and suburb areas, comparatively is 8- 10℃ between Beijing city area and outer suburb area in northwestern regions. (ii) The UHI distribution and intensity in daytime are different from nighttime in Beijing city area, the nighttime UHI is obvious. However, in the daytime, the significant UHI mainly appears in the summer, the autumn takes second place, and the UHI in the winter and the spring seem not obvious. The surface evapotranspiration in suburb areas is larger than that in urban areas in the summer, and high latent heat exchange is evident, which leads to LST difference between city area and suburb area. (iii) The reflection of surface landcover categories is sensitive to the UHI, the correlation between vegetation greenness and UHI shows obviously negative.The scatterplot shows that there is the negative correlation between NDVI and LST (R2 = 0.6481).The results demonstrate that the vegetation greenness is an important factor for reducing the UHI,and large-scale construction of greenbelts can considerably reduce the UHI effect.     

沙坡头没蒿和柠条叶片δ13C 和 N 含量的季节变化特征

通过对腾格里沙漠东南缘沙坡头人工固沙区油蒿和柠条叶片稳定碳同位素分辨率（△）和N 含量的测定，研究了不同种植方式下油蒿和柠条叶片△ 和 N 含量的季节变化及其关系。结果表明：在不同种植方式下，两种植物的△ 与 N 含量在不同月份之间均存在显著差异。油蒿叶片 △ 极显著高于柠条的：在不同种植方式下，油蒿单种下 △ 显著高于混种，柠条则反之。 油蒿叶片 N 含量极显著低于柠条的：不同种植方式下柠条叶片 N 含量无显著差异，而单种油蒿叶片 N 含量则显著低于混种。在 △ 与 N 含量的关系中，柠条叶片 △ 与 N 在两种生境、单种和混种下均极显著正相关，雨明柠条叶片 N 含量可以作为其 △ 与 N 含量的季节变化及其关系在不同微生境有所差异。     

大学城的另类定位--广州旅游的"太阳"

从旅游的角度,运用定性分析和比较分析的方法,分析广州大学城,发现它在广州所有景区中,最有资格和条件担当广州旅游的“太阳”。它位于广州市番禺区新造镇小谷围岛,投资规模、大学数量、占地面积和规划人口容量皆为中国之最,是世界最大的人造景区,具有浓浓的文化氛围、时代气息,能够体现与闪烁广州的灵魂与精神。为此,广州应在大学城的建设中为未来角色创造更好的条件。     

基于高通量测序的表层水体纤毛虫多样性评估方法比较与优化

基于扩增子的高通量测序技术广泛应用于微型生物多样性的研究, 不同的测序手段和数据分析流程, 影响着微型生物多样性与群落结构的分析结果。本研究以易于形态鉴定的砂壳纤毛虫作为研究对象, 比较DNA测序、RNA测序和形态学方法检获的多样性和物种组成等, 探究序列分析流程中关键步骤: 嵌合体处理、可操作分类单元分析方法选择、合并相似分类单元以及去除稀有类群等对多样性结果的影响。研究结果显示无论基于DNA还是RNA的分子手段与形态学方法检获的主要物种基本一致, 与DNA测序相比, RNA测序检获的物种数少, 但差异不显著。基于97%以上相似度聚类和单核苷酸变异所得群落结构相似, 无显著差异; 且所有分析方法都能在一定程度上反映出自然界中不同类群的相对丰度。相较于单核苷酸变异和其他相似度阈值, 99%相似度下聚类所得多样性更为接近形态学结果。去除嵌合体和稀有类群(去除阈值: DNA测序0.05%; RNA测序0.07%), 可明显改善分子多样性虚高的问题。本研究为纤毛虫等真核微生物的分子多样性研究提供了科学的数据分析流程, 对未来真核微生物多样性研究具有指导意义。     

超低频电磁声源非线性动力学建模与分析

电磁声源输出力大、体积小、易于实现超低频输出,在无人反水雷作战中具有显著优势。其动力学行为受到机械回复力和电磁力的耦合作用影响,当施加电流超过坍塌电流,电磁力将超过机械回复力, 就会发生吸和,造成声源的损坏。为准确描述电磁声源非线性动力学特性,预先评估坍塌电流,建立考虑动态漏磁系数的声源非线性动力学模型。通过三维有限元仿真计算动铁芯运动到不同位置处气隙的漏磁系数, 拟合得到动态漏磁系数。根据等效磁路法建立声源的改进电磁力模型,进而建立电磁声源非线性动力学模型。 通过 Runge-Kutta 算法计算得到阶跃激励下声源振动的位移和速度,绘制相平面图。研究稳定与失稳 2 种情况下的相轨迹的动态变化规律,为电磁声源的设计和控制提供理论支撑。     

能见度集合预报及后处理技术应用

基于污染物情况、环流系统和时空分布特征分析,利用神经网络对历史数据进行建模,生成了能见度集合预报产品。在2022年冬季的TS评分检验中,预报产品优于欧洲中期数值预报中心模式(ECMWF)的能见度预报产品。利用概率匹配、最优百分位和神经网络三种后处理方法生成后处理产品,这些产品的TS评分优于集合预报产品。预报输入的ECMWF模式2 m湿度与实况的偏差是误差的主要来源。利用集成方法对三种后处理产品进行集成,其TS评分结果在低能见度区间总体接近或略优于原始产品。生成的能见度集合预报后处理最优集成预报产品成功提高了对中期延伸期能见度天气的预测准确性。     

辽宁省精细化暴雨洪涝灾害风险评估与预评估

基于辽宁省61个国家气象站1961—2020年和998个区域自动气象观测站建站至2020年逐小时、逐日降水资料,分析了辽宁省暴雨洪涝灾害主要致灾因子,计算了暴雨洪涝孕灾环境指标,完成了辽宁省暴雨洪涝灾害危险性评估。结果表明：暴雨洪涝高危险性地区主要位于丹东;暴雨洪涝灾害人口高风险区主要位于沈阳和大连市区;经济高风险区主要位于大连和盘锦市区;水稻、玉米高风险区主要位于锦州、盘锦和丹东。利用辽宁省无缝隙智能网格预报数据对2022年7月28—29日的暴雨过程灾害风险进行了预评估,发现暴雨灾害危险性高值区域主要分布在朝阳、葫芦岛以及辽宁中部。暴雨灾害可能造成的人口、经济高风险区域主要位于辽宁西部和中部地区;暴雨灾害可能造成的水稻和玉米高风险区主要位于沈阳、铁岭和朝阳北部等地区。预计高风险区主要影响人口约为449万人,经济损失约为1432万元,受影响的水稻面积约为1.028万公顷、玉米面积约为1.798万公顷。通过灾后效果检验,发现预评估模型效果良好,可在实际的暴雨洪涝灾害风险评估业务中使用。