浅论我国农业新技术革命     

侯怀恩  宋殿宾  孟兆江 《地域研究与开发》1998,17(2):61-64

当今,农业与相关科学技术的迅速发展使世界农业正孕育着一场革命,结我国农业发展带来闻机遇和压力,我们需加强农业新技术和理论的研究,抢占制高点,加速农业产业化进程,改革科技体制,加强国际合作与交流,发展信息农业,抓住机遇迎接挑战。  相似文献   

松潘—甘孜造山带中丹巴地区变质岩演化及其地质意义     

钟宏  徐士进 《矿物学报》1998,18(4):452-463

丹巴地区位于松潘—甘孜造山带中部。区域动热变质作用主要发生于印支晚期—喜马拉雅早期,与深层滑脱-逆冲作用有关。根据特征矿物组合．丹巴地区变质岩可划分出六个变质带：绢云母—绿泥石带、黑云母带、石榴子石带、十字石带、蓝晶石带和夕线石带。石榴子石生长环带代表每段时间矿物晶体边部的平衡,可用于推测石榴子石生长时的P－t轨迹。利用石榴子石—黑云母温度计和石榴子石—斜长石—Al2SiO5-石英压力计得到石榴子石的参考温度、压力,根据环带定量计算得到的变质作用p-t轨迹为顺时外形式,与其所处的构造背景为大陆碰撞造山带是一致的。  相似文献   

雪峰山加里东造山运动及其体制转换   总被引：17，自引：0，他引：17  

侯光久  索书田 《湖南地质》1998,17(3):141-144

本文论述了雪峰山地区加里东造山运动的变形序列,加里东运动期间,至少存在３个连续的构造热事件。并且阐述了挤压体制向伸展体制的转换,形成低角度滑脱带,高角度正断层及变质核杂岩。  相似文献   

湘西北西向褶皱系的发育特征及其研究意义     

秦松贤  孟德保 《湖南地质》1998,17(3):145-149,159

湘西地区的北西向构造以北西向褶皱变形为主,它横跨于该区北东向构造带之上,并对汞矿床等具有重要控制作用。  相似文献   

基于闪电聚类方法的西北太平洋区域雷暴活动特征     

周鑫  张文娟  张义军  孙秀斌  郑栋  姚雯 《热带气象学报》2021,37(3):490-501

利用2010—2018年全球闪电定位网(WWLLN)观测资料, 采用基于闪电密度的空间聚类算法(DBSCAN)建立了西北太平洋地区雷暴数据集, 研究了该区域雷暴的时空分布特征, 并进行海陆差异对比。研究结果表明, 在合理设定DBSCAN参数阈值的条件下, 基于WWLLN闪电聚类的雷暴与天气雷达观测在时空分布和过程演变上具有一致性。西北太平洋区域的日均雷暴数为3 869, 雷暴的闪电密集区平均面积为557.91km2, 平均延展尺度为31.99 km, 平均闪电频次为33 str/(h·thu)。在空间分布上, 东南亚沿海地区与热带岛屿的雷暴活动最强, 南海的雷暴活动强于深海。距离海岸线越近的海域其雷暴面积越大。在季节分布上, 整个区域雷暴活动在夏季(6—8月)达到全年最强, 南海雷暴活动6月达到峰值, 而日本东部近海海域的雷暴活动则在冬季达到最强。我国内陆南方地区雷暴3月开始显著增多, 雷暴平均面积达到最大, 但雷暴平均闪电频次5月才达到峰值。在日变化方面, 陆地雷暴活动呈现典型的单峰型特征, 大部分雷暴发生在午后及傍晚。海洋雷暴日变化则较为平缓, 南海具有其独特的雷暴日变化特征。   相似文献   

1961—2010年南方双季稻区气候资源变化分析     

李祎君  吕厚荃 《热带气象学报》2021,37(4):590-601

中国南方双季稻播种面积占到全国水稻的85%以上, 研究该区域对气候变化的响应有助于科学地规划和管理双季稻生产。以江南、华南双季稻区为研究对象, 选取1961—2010年南方双季稻区275个数据完整性较好的气象观测站点, 对双季稻区平均气温、日照时数、降水量等气候资源演变规律及其可能变化的分析表明: 该研究区域正处于气温显著上升阶段, 气候倾向率为2℃/(10 a), 尤其是1997年气温突变之后升温幅度进一步增大, 气候倾向率增大为5℃/(10 a), 且秋冬季增温更为显著。研究区域降水年际波动较大, 无明显增减趋势; 从季节上看, 春秋降水有减少趋势, 而冬夏有增加趋势, 且使降水分布更为集中。从空间演变看, 双季稻区气候资源的演变趋势存在较大的差异, 其中华南稻区呈暖湿化, 对喜温好水的双季稻生产是利大于弊; 而江南稻区则呈暖干化趋势, 对水稻生产不利; 同时秋旱风险加大, 尤其是西部地区将面临水资源减少、水稻种植用水不足。另一方面, 随着双季稻区气候变暖, 早稻适宜播种期提前、早晚稻生长季延长, 热量资源增加以及薄膜育秧技术广泛应用等, 都将使双季稻种植格局调整。双季稻区高温日数增多, 早晚稻生长发育无效热量也随之增加, 整体上江南热量资源的有效性低于华南, 尤其是江西和湖南两省, 热量有效性均 < 85%;华南大部地区热量有效性均高于95%。因而, 各地可根据所处区域气候资源要素演变规律及热量有效性分布选取产量与品质更好的中晚熟品种种植, 提高水稻种植积极性, 促进早晚稻安全生产。   相似文献   

CMA_FEBLS低频三维全闪探测技术研究及观测10年进展     

张阳  王敬轩  郑栋  吕伟涛  张义军  樊艳峰  范祥鹏  姚雯 《热带气象学报》2021,37(3):298-308

三维全闪探测已经成为了深入认识闪电物理机制和雷暴电活动规律的重要手段。中国气象局雷电野外科学试验基地(CMA_FEBLS)自主研发了低频电场探测阵列(LFEDA), 并持续开展了针对广东地区雷暴全闪电活动的综合观测试验, 在精细化三维定位算法和基于三维全闪数据的闪电放电过程研究方面取得了若干研究结果。(1) LFEDA具备雷暴电活动的无死时间捕获能力、优于百米的定位精度和一定的通道定位能力。(2)发展了基于简单脉冲特征的三维全闪定位算法, 并进一步将经验模态分解及衍生方法引入到闪电信号处理中, 提高了定位的精细化水平; 发展了融合到达时差和时间反转技术的定位方法, 提升了抗干扰能力、降低了对站网的要求。(3)实现了典型放电事件的电流波形反演, 获得了窄偶极性放电事件(NBE)、初始击穿脉冲(IBP)和爆发式脉冲簇(RBPs)的放电特征; 研究发现绝大多数闪电始发于IBP, 而作为始发的NBE则具有更大的孤立性、更大的相对幅度和更快的发展速度。(4)发现随着起始放电高度增加, 初始阶段持续时间和步长增加, 发展速度和脉冲丰度下降; 始发于强对流区时始发阶段通常有更大的速度和脉冲丰度。   相似文献   

State of China's climate in 2021          下载免费PDF全文

Wei Li  Shanshan Zhao  Yu Chen  Ling Wang  Wei Hou  Yundi Jiang  Xukai Zou  Shuai Shi 《大气和海洋科学快报》2022,15(4):100211

This report is a summary of China's climate, as well as major weather and climate events, during 2021. In 2021, the mean temperature in China was 10.5°C, which was 1.0°C above normal (1981–2010 average) and broke the highest record since 1951. The annual rainfall in China was 672.1 mm, which was 6.7% above normal. Also, the annual rainfall in northern China was 40.2% above normal, which ranked second highest since 1961. The rainstorm intensity in the rainy season was strong and featured significant extremes, and disasters caused by rainstorms and flooding were more serious than the average in the past decade. In particular, the extremely strong rainstorm in Henan during July and autumn caused flooding in the middle and lower reaches of the Yellow River with severe consequences. Heatwaves occurred more frequently than normal, and their durations in southern China were longer than normal in summer and autumn. Phased drought was obvious, and caused serious impacts in South China. The number of generated and landfalling typhoons was lower than normal; however, Typhoon In-fa broke the record for the longest overland duration, held since 1949, and affected a wide area. Severe convective weather and extreme windy weather occurred frequently, causing serious impacts. The number of cold waves was more than normal, which caused wide-ranging extremely low temperatures in many places. Sandstorms appeared earlier than normal in 2021, and the number of strong dust storm processes was more than normal.摘要2021年, 中国气候暖湿特征明显, 全国平均气温10.5℃, 较常年偏高1.0℃, 创下了1951年以来最高纪录; 全国平均降水量672.1毫米, 比常年偏多6.7%, 其中北方地区平均降水量较常年偏多40.2%, 为1961年以来第二多. 汛期暴雨过程强度大, 极端性显著, 河南特大暴雨灾害影响重, 黄河中下游流域秋汛明显; 高温过程多, 夏秋南方高温持续时间长; 区域性, 阶段性气象干旱明显, 华南干旱影响较重; 台风生成和登陆均偏少, “烟花”陆地滞留时间长, 影响范围广; 强对流天气强发, 极端大风频发, 局地致灾重; 寒潮过程多, 强度大, 极端低温频现; 沙尘天气出现早, 强沙尘暴过程多.  相似文献   

Probabilistic modeling of disrupted infrastructures due to fallen trees subjected to extreme winds in urban community     

Hou  Guangyang  Chen  Suren 《Natural Hazards》2020,102(3):1323-1350

Natural Hazards - Tree failures due to strong winds in urban areas cause extensive direct and indirect economic and environmental loss, including disrupting adjacent infrastructures, such as...  相似文献   

Does canopy wetness matter? Evapotranspiration from a subtropical montane cloud forest in Taiwan          下载免费PDF全文

Hou‐Sen Chu  Shih‐Chieh Chang  Otto Klemm  Cheng‐Wei Lai  You‐Zhu Lin  Chi‐Chen Wu  Ji‐Yu Lin  Jhia‐Ying Jiang  Jiquan Chen  Johan F. Gottgens  Yue‐Joe Hsia 《水文研究》2014,28(3):1190-1214

Evapotranspiration (ET) and canopy wetness were measured over a 2‐year intensive field campaign at the Chi‐Lan Mountain cloud forest site in Taiwan. Eddy covariance and sap flow methods were applied to measure ET and tree sap flow of the endemic yellow cypress (Chamaecyparis obtusa var. formosana). ET was 553 mm yr^?1 over the study period with an annual rainfall and fog deposition of 4893 and 288 mm yr^–1, respectively. The duration of canopy wetness exceeded actual fog or rain events (mostly in the afternoon), and the intercepted water was evaporated later in the following dry morning. The cumulative wet duration accounted for 52% of time over the study period, which was longer than the duration of rainfall and fog altogether (41%). As it adapted to the extremely moist environment, the yellow cypress behaved in a wet‐enhanced/dry‐reduced water use strategy and was sensitive to short periods of dry atmosphere with high evaporation potential. During dry days, the sap flow rate rose quickly after dawn and led to conservative water use through midday and the afternoon. During periodically wet days, the canopy was mostly wetted in the morning, and the interception evaporation contributed largely to the morning ET. The initiation of morning sap flow was postponed 1–3 h, and the sap flow rate tended to peak later at midday. The midday canopy conductance was higher in the periodically wet days (10.6 mm s^–1) as compared with 7.6 mm s^?1 in the dry days. Consequently, the dry‐reduced water use strategy led to much lower annual ET with respect to the available energy (~46%) and high precipitation input (~11%). The moist‐adapted ecohydrology we report reveals the vulnerability of montane cloud forests to prolonged fog‐free periods. More research is urgently needed to better understand the resilience of these ecosystems and formulate adaptive management plans. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献