冕洞观测研究的近期进展

简要介绍了在１９８８－１９９５年期间冕洞观测研究的主要进展。文中共分五个方面：１．冕洞磁场观测研究的新进展；２．冕洞在太阳活动周不同位相时的规律性；３．冕洞区高速太阳风观测的新结果；４．冕洞加热问题；５．存在问题。     

不同结构林带防风效能风洞模拟

防风林带结构是影响防风效能的主要因素。建立不同宽度、不同株行距林带防风效能与林带后距离之间的统计模型,可以为防风林建设提供指导性意见。通过风洞实验,在11 m·s^-1风速下,对4种宽度、5种株行距林带的背风面0~10H（H为林带高度）的风速进行测定,采用曲线参数估计法、傅立叶模型、SSF模型（Sum of Sin Functions）,构建了不同结构林带防风效能与林带后距离间的统计模型。结果表明：傅立叶模型拟合不同宽度林带的防风效能与林带后距离的关系效果最优,可决系数（R²）均在98%以上;SSF模型拟合不同株行距林带的防风效能与林带后距离的关系效果最优（R²>0.98）。根据构建的统计模型,风速为11 m·s^-1左右时,林带宽度8 m（两行一带）的防风林的防风效能存在明显优势;5种株行距的林带中,株行距为8 m×8 m的防风林带本试验条件下防风效果最好。     

NUMERICAL SIMULATION OF INTERANNUAL AND INTERDECADAL VARIABILITY OF SURFACE WIND OVER THE TROPICAL PACIFIC

A global atmospheric general circulation model (L9R15 AGCMs) forced by COADS SST was integrated from 1945 to 1993. Interannual and interdecadal variability of the simulated surface wind over the tropical Pacific was analyzed and shown to agree vey well with observation. Simulation of surface wind over the central-western equatorial Pacific was more successful than that over the eastern Pacific. Zonal propagating feature of interannual variability of the tropical Pacific wind anomalies and its decadal difference were also simulated successfully. The close agreement between simulation and observation on the existence of obvious interdecadal variability of tropical Pacific surface wind attested to the high simulation capability of AGCM.     

两次森林火灾的双偏振雷达探测特征分析

通过对2020年3月17日山东烟台、4月23日山东青岛发生的两次森林火灾的双偏振雷达探测资料进行分析,结果表明：（1）森林火灾燃烧产生的灰烬上升到空中,随环境风向下风方飘散,形成烟羽,烟羽的雷达反射率因子在20 dBZ左右,火灾点上空很小范围最大值达36 dBZ。（2）两次山火的灰烬飘浮物随环境风向下游扩散的最远距离分别是65 km和94 km,最高上升高度分别达3.7 km和4.8 km。（3）追踪烟羽的前沿可以估算相应高度上环境风的速度;两次火灾都发生在晴天,环境风速不大,除了烟羽边缘位置速度谱宽值较大外,其余部分速度谱宽都很小,大部分为1~2 m·s^-1。（4）相关系数（C_c）、差分反射率（Z_DR）和差分相移（Φ_DP）探测到的范围与雷达反射率因子的演变形态和面积接近,同样随烟羽的扩散而逐渐增大;C_c值非常小,大多数区域小于0.9,少数距离库库元的Cc值低于0.5;火灾点上空的Z_DR值有相对较小的区域,为2~3 dB,而火灾点下风方,大部分Z_DR值都很大,大多超过5 dB。（5）两次森林火灾的双偏振探测特征表明,产生回波的反射物主要是干草、松针等燃烧后的灰烬形成的水平尺度较大的非球形粒子反射物。     

Investment risk and return under renewable decarbonization of a power market

How does financial performance risk affect investments in low-carbon electricity-generating technologies to achieve climate policy targets? A detailed risk simulation of price formation in the Great Britain wholesale power market is used to show that the increasing replacement of fossil facilities with wind, ceteris paribus, may cause a deterioration of the financial risk–return performance metrics for incremental investments. Low-carbon investments appear to be high risk, low return, and as such may require a progressively higher level of support over time than envisaged by the conventional degression trajectories. The increasing riskiness of the wholesale market will to some extent offset the benefits of lower capital costs and operational efficiencies if investors need to satisfy cautious debt coverage ratios alongside positive expected returns. This increased risk is additional to the well-known ‘merit order effect’ of low-carbon investments progressively depressing wholesale prices and hence their expected investment returns.

Policy relevance

Policy support for renewable technologies such as wind is usually based upon levelized costs and is expected to reduce over time as capital costs and operational efficiencies improve. However, levelized costs do not take full account of the risk aversion that investors may have in practice. Expected policy support reductions may be moderated to some extent by the increased financial performance risk that intermittent technologies bring to the power market. The annual risk-return profiles for incremental investments deteriorate for all technologies as wind replaces fossil fuels. This extra risk premium will need to be incorporated into evaluating policy incentives for new investments in a decarbonizing power market.     

鄂尔多斯高原清代风灾

根据历史文献资料,利用数理统计等方法研究了鄂尔多斯高原清代的风灾。结果表明:鄂尔多斯高原清代发生风灾51次,平均每5.3 a发生1次。其中轻度风灾16次、中度风灾34次、大风灾1次,分别占风灾总数的31.3%、66.7%、2.0%。研究区清代风灾变化可分为3个阶段。第1阶段为1644-1783年,发生风灾24次,平均每5.8 a发生1次,为风灾频次居中的多发阶段。第2阶段为1784-1843年,发生风灾4次,平均每15 a发生1次,为风灾频次最少的低发阶段。第3阶段为1844-1911年,发生风灾23次,平均每3.0 a发生1次,为风灾频次最高的多发阶段。从清代早期到晚期,鄂尔多斯高原风灾频次呈上升趋势。鄂尔多斯高原清代有4次风灾爆发期,分别为公元1708-1710年、1851-1853年、1878-1884年和1908-1910年。在1878-1910年间有2次风灾爆发期,对应于中国东部和北半球的低温期。鄂尔多斯高原清代风灾有6 a左右的短周期和23 a左右的长周期,其中23 a的周期是第一主周期。该区风灾发生的主要原因是强冬季风的活动,在气候寒冷期或干旱期发生频率较高。     

江苏省龙卷发生特征及其在年际尺度上与ENSO的关系研究

利用1976—2005年江苏省龙卷信息化资料和高分辨率再分析资料,对江苏省龙卷的发生特征以及ENSO事件对江苏省龙卷发生数的影响进行了分析。结果表明:(1)1976—2005年,江苏省龙卷发生数年际和年代际变化明显,空间分布不均匀:1990s龙卷发生数较多;盐城南部和南通沿海地区是龙卷较为多发的区域。(2)ENSO事件对江苏省龙卷的发生频率有重要影响:ENSO冷事件月份平均龙卷发生数多于暖事件月份;非ENSO事件月份平均龙卷发生数居中。(3)ENSO冷事件时西南低空急流发生频率明显增加,由于低空急流增强而引起的江苏省地区水汽供应、动力条件和不稳定能量的分布均有利于龙卷的发生,导致在ENSO冷事件情况下江苏省龙卷发生数偏多。     

Analysis of ERS-2 scatterometer winds and wind-wave calculation for eastern China seas

The wind system over the China seas plays an important role in climate variation there. In this paper, ERS-2 scatterometer winds covering the period of 1998 and the area of 25-41°N, 117-130°E were analyzed and compared to NCEP winds and buoy winds in the same period and location, to assess how well the ERS-2 data reflect the real wind regime, at least for this area. The results indicated that ERS-2 scatterometer winds are closer to buoy observations than NCEP winds. In addition, a new wind-wave growth relation was applied to calculate wave parameters.     

Variations of the magnetic field near Mars caused by magnetic crustal anomalies

The possible avenues for photoelectron transport were determined during southern hemisphere winter at Mars by using a mapping analysis of the theoretical magnetic field. Magnetic field line tracing was performed by superposing two magnetic field models: (1) magnetic field derived from a three-dimensional (3D) self-consistent quasi-neutral hybrid model which does not contain the Martian crustal magnetic anomalies and (2) a 3D map of the magnetic field associated with the magnetic anomalies based on Mars Global Surveyor magnetic field measurements. It was found that magnetic field lines connected to the nightside of the planet are mainly channeled within the optical shadow of the magnetotail whereas magnetic field lines connected to the dayside of the planet are observed to form the remainder of the magnetosphere. The simulation suggests that the crustal anomalies create “a magnetic shield” by decreasing the region near Mars which is magnetically connected to the Martian magnetosphere. The rotation of Mars causes periodic changes in magnetic connectivity, but not to qualitative changes in the overall magnetic field draping around Mars.     

南黄海辐射沙脊群西洋水道污水输移扩散研究

采用沿深平均二维数值模型对南黄海辐射沙脊群西洋海域的潮流场和物质扩散场进行了模拟,计算和分析了大潮情况下海域5 m、7 m和10 m 3种水深(理论基准面下)排放位置处达标污水输移扩散的范围及分布规律。结果表明,污水排入海后,会很快被稀释,各排放位置200和500稀释度等值线包络面积均较小,且包络面积随水深增加有明显变小的规律。拟合了不同污水排放量对应的200和500稀释倍数包络面积,发现两者呈良好的幂级数关系。