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1.
利用1980—2015年6—8月我国逐日降水观测数据评估CWRF模式（Climate-Weather Research and Forecasting model）多种参数化方案对我国夏季日降水的模拟能力,并考察累积概率变换偏差订正法（CDFt）的订正效果。通过将广义帕累托分布（GPD）引入到偏差订正模型中,提出针对极端降水的累积概率变换偏差订正法（XCDFt）,检验和评估其对极端降水订正的适用性。结果显示:CWRF模式微物理过程选用Morrison-aerosol参数化方案组合对我国降水场的模拟较好,CDFt订正效果良好;XCDFt偏差订正模型能够较好地提取模式建模与验证时期变化信号,订正后相比订正前与观测极端降水的概率分布更为接近;经过XCDFt订正后华南、华中和华北地区20年一遇的极端降水重现水平较模拟值更接近观测值,可为CWRF模式提高极端降水的业务预测水平提供参考。 相似文献
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利用CWRF(Climate-Weather Research and Forecasting model)对中国区域气候的31 a多物理集合模拟试验,分析了该模式对青藏高原气温和降水的模拟效果及其对水平分辨率和物理过程参数化方案的敏感性。结果表明:1)CWRF降尺度全面改善了全球模式对高原气温和降水的模拟,使气温年循环的均方根误差减小近1℃,月降水量年循环的均方根误差减小10~40 mm,同时显著提高了各月气温和降水与实测资料年际变化的相关系数,最高提升0.6;2)模式分辨率对降水模拟有显著影响,不同分辨率模拟降水差异高达60 mm(54%),模拟偏差随分辨率提高先降低后上升,转折在30 km左右;3)物理过程参数化方案对气温和降水模拟影响显著,不同方案模拟的各月平均气温相差1~4℃,夏季各月降水量相差20~100 mm,其中对气温模拟影响最大的是辐射方案,对降水影响最大的是积云方案。本文为CWRF局地优化对物理参数化及水平分辨率等如何选择提供了依据。 相似文献
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Additional studies of the ion composition results obtained from the OGO-6 satellite support earlier observations of irregularities in the distribution of H+ and He+ within the light ion trough near L = 4, which has been associated with the plasmapause. These irregularities are in the form of sub-troughs superimposed upon the major mid latitude decrease of the light ions. In the sub-troughs, ionization depletions and recoveries of as much as an order of magnitude are observed within a few degrees of latitude, usually exhibited in a pattern which changes significantly with longitude as the Earth rotates beneath the relatively fixed satellite orbit. The location and properties exhibited by these sub-troughs appear to be consistent with the concept of a plasmasphere distortion in the form of “plasmatails” resulting from the combined effects of magnetospheric convection plus corotation. Like the light ion trough, the “plasmatail” irregularity in H+ may be obscured on the day side by the dominant topside distribution of O+. Consequently, these light ion irregularities are seen as an important factor for studies of plasmapause-trough relationships. 相似文献
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Fire detection using satellites is an important source of information for fire management, ecological studies and emission estimates. However, little is known about the minimum sizes of fires that are being detected. This paper presents an approach using fire radiative power estimated from MODIS satellite data to determine the detection threshold for fire-prone savannas in Northern Australia. The results indicate that fires with an active flaming area 100–300 m2 can be detected in the study region. It is also shown that the algorithm is slightly more sensitive at night. As expected the detection threshold shows strong view angle dependence. While this study has been undertaken in the savannas of Northern Australia, the results should be transferable to other savanna regions worldwide and other areas where fires are not obscured by a dense tree canopy. 相似文献
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《Geomorphology》2001,36(3-4):155-165
Sand transport by wind is a special case of two-phase flow of gas and solids, with saltating grains accounting for about 75% of the transport rate. This form of flow is not only the main external agent moulding aeolian landforms but also the motive force responsible for transport, sorting and deposition of aeolian sediments. High-speed multiflash photography is an effective method of studying the distribution of velocity and energy of saltating grains within the boundary layer of wind tunnel. The experimental wind shear velocities were set at 0.63, 0.64, 0.74 and 0.81 ms−1. The statistical study of the results showed that there is a power function relation between mean velocity and height of saltating grains. As the height is divided into 0.5-cm intervals, the sand grain velocities at various levels are consistent with the Pearson VII distribution pattern. The variations in kinetic energy and total energy of sand grains with height accord with the pulse peak modified with power term (Pulsepow) law; the maximum values occur at heights of 6 cm or so and tend to shift upward with increasing wind velocity. 相似文献
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Based on a large number of energy-economic and integrated assessment models, the Energy Modeling Forum (EMF) 27 study systematically explores the implications of technology cost and availability for feasibility and macroeconomic costs of energy system transformations toward climate stabilization. At the highest level, the technology strategy articulated in all the scenarios in EMF27 includes three elements: decarbonization of energy supply, increasing the use of low-carbon energy carriers in end-use, and reduction of energy use. The way that the scenarios differ is in the degree to which these different elements of strategy are implemented, the timing of those implementations, and the associated macroeconomic costs. The study also discusses the value of individual technologies for achieving climate stabilization. A robust finding is that the unavailability of carbon capture and storage and limited availability of bioenergy have the largest impact on feasibility and macroeconomic costs for stabilizing atmospheric concentrations at low levels, mostly because of their combined ability to remove carbon from the atmosphere. Constraining options in the electric sector such as nuclear power, wind and solar energy in contrast has a much smaller impact on the cost of mitigation. 相似文献