夏季城市热场的卫星遥感分析

利用1998年8月4日上海幅TM6图像,经定位、配准、纠正、图像处理、噪声剔除、亮温标定及特征提取等步骤,得出上海市亮温分布场,同时对其热力景观、细部结构及其成因做了分析。实践证明,TM6图像可作为城市热环境质量评价、生态城市规划的背景资料和依据。     

Swelter in the city: Urban greenery and its effects on temperature in Guwahati,India

Changing urban landscape with multistoried high rises, roads and pavements is continuously reducing urban green space. These structures result in high surface temperature variation within cities. To explore the relationship between surface temperature and normalized difference vegetation index (NDVI), this study estimates two models—geographically weighted regression (GWR) and a fixed effect panel data model in relation to the Guwahati Metropolitan Area (GMA), a secondary city in north east India. The results indicate the superiority of GWR regression in presence of spatial dependence. Panel data analysis shows that the densely populated urban areas in the GMA with less than 10 per cent greenery are 1°C warmer than the sub-urban areas with 50 per cent greenery.     

Bragg reflection of water waves by multiple floating horizontal flexible membranes with submerged rectangular bars on the seabed

Bragg reflection of water waves by multiple floating horizontal flexible membranes is investigated based on the linear wave theory and the assumption of small membrane response. Under the floating horizontal membranes, periodical submerged rectangular bars are arranged on the flat seabed. The total reflection and transmission coefficients are obtained by using the eigenfunction expansion method and the wide spacing approximation. The calculated coefficients are validated with the results available in the literature, which shows that the present method is applicable. The characteristics of Bragg reflection are systematically investigated by changing various parameters including the height of the rectangular bars, the number, the tension, the spacing, and the length of the flexible membranes. The results can help designing multiple floating horizontal flexible membranes as effective floating breakwaters by taking advantage of Bragg reflection.     

基于新型探测资料对西安一次弱降水预报失误的原因分析

利用微波辐射计、激光测风雷达、多普勒雷达、相控阵雷达等新型探测资料、地面加密观测资料、ERA5再分析及多模式数值预报结果对2022年4月24日西安城区一次弱降水预报出现明显失误的原因进行分析,结果表明：(1)全球数值预报模式和中尺度数值预报模式对本次过程西安城区均报有明显降水,主要原因为模式对低层相对湿度预报明显偏大;(2)多种新型探测数据分析认为近地层湿度条件较差及中层的绝对水汽含量低,中层的干暖空气不利于成云致雨,垂直上升运动不强,且由于低层非常干燥,使水滴在下沉过程中蒸发,从而无法形成雨滴下落,这些原因共同造成西安城区无降水,低层相对湿度预报偏大是造成这次西安城区降水预报失误的主要原因之一;(3)造成西安城区近地层湿度条件差的原因是城市干热岛效应和低层干暖平流输送,且降水云团翻越秦岭后其湿空气绝热下沉至城区后出现增温降湿,使得城区形成较为深厚的干层,即使有雨滴在下落过程中也会造成更强的蒸发,这也是城区没有降水的重要原因之一;(4)预报员主观预报订正出现空报主要是源于对边界层水汽、抬升条件等关键降水要素缺乏订正能力,且对大城市的干热岛效应和秦岭山区地形影响研究不足。     

西太平洋暖池热含量变化与东亚冬季风关系

利用 1955-2003 年 NCEP\NCAR 再分析资料和美国 Scripps 海洋研究所环境数据分析中心 ( JEDAC ) 提供的冬季热含量资料,采用小波分析、相关及合成分析等方法, 分析了西太平洋暖池热含量变化特征及其与东亚冬季风关系.结果表明,西太平洋暖池热含量与东亚冬季风有着非常密切的联系,当西太平洋暖池热含量异常偏高时,对流层低层在菲律宾及以东洋面形成一个异常的气旋性环流,中国大陆上空形成一个异常的反气旋性环流,从而使得东亚冬季风在东南区加强,西北区减弱.     

2023年全球重大天气气候事件

2023年,全球平均气温比工业化前高出约1.45℃(±0.12℃),是有观测记录以来最热的一年。全球海平面继续上升,且全球平均海平面达到了有卫星记录(1993年至今)以来的最高水平,反映了持续的海洋变暖以及冰川和冰盖的融化。北极海冰面积仍远低于常年值,南极海冰面积创下历史新低。巴基斯坦、中国京津冀地区、意大利、巴西圣保罗州北部沿海地区、新西兰北岛等地遭受暴雨洪涝灾害,非洲西北部、中国云南、中美洲和南美洲北部发生严重干旱,南欧、北美、南美、东亚和南亚等地遭遇创纪录高温热浪,欧洲和北美等地遭遇寒流和暴风雪侵袭,强对流天气频繁袭击世界各处,全球热带气旋活动频繁。     

Material exchange as heat engine for the corona-chromosphere transition region

We think that a steady material exchange in the upper solar atmosphere can act as a heat engine that cools the corona and heats the corona-chromosphere transition region. We have considered heat conduction from the corona and radiation loss in the transition region and have calculated the temperature, density and velocity distributions in the transition region. Also discussed is the relation between the material flux, the velocity boundary value and the thickness of the transition region.     

黄斑篮子鱼去毒相关基因的克隆与肝脏组成型表达分析

从基因水平探讨海洋鱼类对海洋藻毒素的去毒分子机理。采用RT-PCR法成功克隆了黄斑篮子鱼Siganus oramin肝脏I时相代谢酶细胞色素P450 1A(CYP1A)、II时相代谢酶alpha型谷胱甘肽S-转移酶(GSTA)和rho型谷胱甘肽S-转移酶(GSTR)、热休克蛋白70 (HSP70)、alpha 1型钠钾ATP酶(ATP1A1)及β-肌动蛋白(beta-actin, ACT)基因cDNA核心序列,序列分别长879 bp、582 bp、588 bp、660 bp、749 bp和554 bp。序列同源性分析发现,属鲈形目的黄斑篮子鱼CYP1A、GSTA和GSTR与同属鲈形目的牙鲆Paralichthys olivaceus、欧洲鲽Pleuronectes platessa、真鲷Pagrus major、鲤形目的斑马鱼Brachydanio rerio 相应氨基酸序列同源性较高,CYP1A和GSTA与非洲爪蟾(两栖类)、鸡(鸟类)、小鼠、大鼠和人(哺乳类)相应氨基酸序列同源性低,这可能与鱼类I、II时相去毒酶基因承担水环境毒素去毒代谢的特殊功能有关;而HSP70、ATP1A和β-肌动蛋白在鱼类、两栖类、鸟类、哺乳类中均有较高的同源性,这可能与这些基因在机体中承担的最基本的生命功能相关。应用半定量RT-PCR的方法,以β-肌动蛋白作为外参照,在指数期增长范围内分别得到了CYP1A、GSTA、GSTR、HSP70和ATP1A1 mRNA与β-肌动蛋白mRNA (%)的比值,确定黄斑篮子鱼肝脏去毒相关基因的组成型表达水平。其中,黄斑篮子鱼肝脏CYP1A、GSTA和GSTR基因组成型表达相对较高,HSP70和ATP1A1基因组成型表达相对较低,这可能与不同基因在黄斑篮子鱼海洋藻毒素去毒分子机理中承担的作用相关,为海洋藻毒素在海洋鱼类中的积聚及代谢去毒分子机制的研究提供了相关数据。     

Optical Spectroscopy of Comet C/2000 WM1 (LINEAR) at the Guillermo Harro Astrophysical Observatory in Mexico

We present a preliminary analysis of medium resolution optical spectra of comet C/2000 WM1 (LINEAR) obtained on 22 November 2001. Theemission lines of the molecules C₂, C₃, CN, NH₂,H₂O⁺ and presumably CO (Asundi and triplet bands) and C₂ ^-were identified in these spectra. By analysing the brightnessdistributions of the C₂, C₃, CN emission lines along theslit of the spectrograph we determined some physical parameters of theseneutrals, such as their lifetimes and expansion velocities inthe coma. The Franck–Condon factors for the CO Asundi bands and C₂ ^- bands were calculated using a Morse potential model.     

基于CFD技术的河谷型城市风环境模拟——以兰州市城关区为例

本文应用CFD软件对多种流场的强大模拟功能,模拟小尺度的兰州市城关区风环境。选用SRTM资料表征兰州市城关区的地形,应用ArcGIS生成兰州市地形模型,计算相关参数,将计算得到的地形粗糙度和兰州多年气候资料转化为CFD模型的数字参数及模拟边界条件等,首次模拟得到河谷型地区兰州城关区的风环境。结果表明:（1）河谷型地区中,气流过山时风速达最大值,依山体高度增大,而在背风坡风速值明显降低,达到0～1 m·s-1;（2）气流过境时在沿河谷前进,且在谷底风速值达0～1 m·s-1;（3）在模拟城市热岛效应的对比实验中,地块加热对气流过境有停滞作用。