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881.
Improvement of the semi-Lagrangian advection scheme in the GRAPES model: Theoretical analysis and idealized tests 总被引:2,自引:0,他引:2
ABSTRACT The Global/Regional Assimilation and PrEdiction System (GRAPES) is the newgeneration numerical weather predic- tion (NWP) system developed by the China Meteorological Administration. It is a fully compressible non-hydrostatical global/regional unified model that uses a traditional semi-Lagrangian advection scheme with cubic Lagrangian interpola tion (referred to as the SL_CL scheme). The SL_CL scheme has been used in many operational NWP models, but there are still some deficiencies, such as the damping effects due to the interpolation and the relatively low accuracy. Based on Reich's semi-Lagrangian advection scheme (referred to as the R2007 scheme), the Re_R2007 scheme that uses the low- and high-order B-spline function for interpolation at the departure point, is developed in this paper. One- and two-dimensional idealized tests in the rectangular coordinate system with uniform grid cells were conducted to compare the Re..R2007 scheme and the SL_CL scheme. The numerical results showed that: (1) the damping effects were remarkably reduced with the Re_R2007 scheme; and (2) the normalized errors of the Re_R2007 scheme were about 7.5 and 3 times smaller than those of the SL_CL scheme in one- and two-dimensional tests, respectively, indicating the higher accuracy of the Re..R2007 scheme. Furthermore, two solid-body rotation tests were conducted in the latitude-longitude spherical coordinate system with non uniform grid cells, which also verified the Re_R2007 scheme's advantages. Finally, in comparison with other global advection schemes, the Re_R2007 scheme was competitive in terms of accuracy and flow independence. An encouraging possibility for the application of the Re_R2007 scheme to the GRAPES model is provided. 相似文献
882.
The impact of asymmetric thermal forcing associated with land–sea distribution on interdecadal variation in large-scale circulation and blocking was investigated using observations and the coupled model intercomparison project outputs. A land–sea index (LSI) was defined to measure asymmetric zonal thermal forcing; the index changed from a negative to a positive anomaly in the 1980s. In the positive phase of the LSI, the 500 hPa geopotential height decreased in the polar regions and increased in the mid-latitudes. The tropospheric planetary wave activity also became weaker and exerted less easterly forcing on the westerly wind. These circulation changes were favorable for westerly wind acceleration and reduced blocking. In the Atlantic, the duration of blocking decreased by 38 % during the positive LSI phase compared with that during the negative phase; in Europe, the number of blocking persisting for longer than 10 days during the positive LSI phase was only half of the number during the negative phase. The observed surface air temperature anomaly followed a distinctive “cold ocean/warm land” (COWL) pattern, which provided an environment that reduced, or destroyed, the resonance forcing of topography and was unfavorable for the development and persistence of blocking. In turn, the responses of the westerly and blocking could further enhance continental warming, which would strengthen the “cold ocean/warm land” pattern. This positive feedback amplified regional warming in the context of overall global warming. 相似文献
883.
Samson Hagos L. Ruby Leung Yongkang Xue Aaron Boone Fernando de Sales Naresh Neupane Maoyi Huang Jin-Ho Yoon 《Climate Dynamics》2014,43(9-10):2765-2775
Land use and land cover (LULC) over Africa have changed substantially over the last 60 years and this change has been proposed to affect monsoon circulation and precipitation. This study examines the uncertainties of model simulated response in the African monsoon system and Sahel precipitation due to LULC change using a set of regional model simulations with different combinations of land surface and cumulus parameterization schemes. Although the magnitude of the response covers a broad range of values, most of the simulations show a decline in Sahel precipitation due to the expansion of pasture and croplands at the expense of trees and shrubs and an increase in surface air temperature. The relationship between the model responses to LULC change and the climatologists of the control simulations is also examined. Simulations that are climatologically too dry or too wet compared to observations and reanalyses have weak response to land use change because they are in moisture or energy limited regimes respectively. The ones that lie in between have stronger response to the LULC changes, showing a more significant role in land–atmosphere interactions. Much of the change in precipitation is related to changes in circulation, particularly to the response of the intensity and latitudinal position of the African Easterly Jet, which varies with the changes in meridional surface temperature gradients. The study highlights the need for measurements of the surface fluxes across the meridional cross-section of the Sahel to evaluate models and thereby allowing human impacts such as land use change on the monsoon to be projected more realistically. 相似文献
884.
文中材料采自黔北务川—正安—道真地区下二叠统大竹园组和梁山组。大竹园组孢粉化石类型单调,保存较差;而梁山组孢粉化石丰富,保存良好。孢粉组合特征为:(1)大竹园组包含丰富的Calamospora和Florinites及少量Torispora verrucosa,Gulisporites,Alisporites,Hamiapollenites和Striatopodocarpites,这一孢粉组合主要出现在上石炭统至下二叠统。按照大竹园组层位和孢粉化石特征,其地质时代应为早二叠世Asselian期—Artinskian期(相当于紫松期—隆林期)。(2)梁山组中可建立孢粉组合Laevigatosporites vulgaris-Gulisporites-Florinites ovalis,共计发现孢粉化石34属49种,其中蕨类植物孢子含量为51.6%~56.1%,裸子植物花粉含量为43.9%~48.4%。与大竹园组沉积时期相比,这一时期植被极为繁盛。根据孢粉组合特征,梁山组地质时代可能为早二叠世隆林期,即Kungurian期。 相似文献
885.
根据对渤海湾盆地沾化凹陷泥质岩、粉砂岩、砂岩和白云岩平行层面与垂直层面方向热导率差异及孔隙连通性差异特征的研究,探讨了沉积岩平行层面与垂直层面方向热导率与孔隙连通性之间的关系。热导率实验结果表明:沾化凹陷泥质岩、粉砂岩和砂岩的平行层面方向热导率大于垂直层面方向热导率;白云岩的平行层面方向热导率小于垂直层面方向热导率。沉积岩平行层面与垂直层面方向热导率差异和孔隙连通性差异之间具有正相关性。孔隙特征分析结果表明:孔隙连通性较好方向,热导率也较高;孔隙连通性较差的的方向,热导率也较低。 相似文献
886.
887.
地勘单位执行多年的经济指标考核体系一般由决算总收入、新增资本积累、净资产总额、应收账款与存货占经营收入比率、提取折旧额、提交煤炭资源量,人均年收入等七项指标组成。该指标体系经过多年运行,已经趋于成熟。但是该指标考核体系没有考虑到不同单位的综合经济实力和生产能力水平的差异,忽略了不同单位之间的主营业务性质和区域性差异,使考核结果公平性存在一定的缺陷。本文依据全面考核原则、科学考核原则、可操作性原则,探讨了如何改进经济指标考核体系,并提出了可供实施的企业经济效益综合指数考核指标体系。 相似文献
888.
High lipid content and productivity of microalgae cultivating under elevated carbon dioxide 总被引:1,自引:1,他引:0
This study examined the cell growth rate, lipid contents, lipid productivity, chlorophyll a concentration, and carbon dioxide tolerance of Chlorella vulgaris under various cultivation conditions. The pH, concentration of carbon dioxide in media, and light intensity variables were manipulated to obtain high lipid productivity. The optimum conditions were at pH 7.0, 2,930 lux, and 30 % carbon dioxide. Biomass concentration reached 1,288, 1,130, and 1,083 mg L?1 at 15, 30, and 50 % CO2 after 6 days, respectively, implying that this strain has appreciable tolerance to carbon dioxide. The highest concentration of chlorophyll a occurred at 2,930 lux and decreased with increasing light intensity gradually. The maximum specific growth rate was 3.25 day?1 based on the dry weight and 4.63 day?1 based on the cell number. The lipid content (45.68 %) and lipid productivity (86.03 mg day?1 L?1) obtained in this study are higher than reported values in literatures. Hence, C. vulgaris is a good candidate for subsequent research in biodiesel production under elevated carbon dioxide concentration by microalgae. 相似文献
889.
Hong-Yan Zeng Xiao-Li Cao Long-Bin Xiong Xi-Ling Cai Li-Qun Huang Cun-Ying Zhang Yu-Qin Li 《Environmental Earth Sciences》2014,71(3):1339-1348
Phenol biodegradation in an aerobic batch reactor was investigated using mixed two co-aggregating strains (Flavobacterium sp. and Acetobacter sp.). Response surface methodology by the Box–Behnken model was used to evaluate the optimal cell growth and phenol degradation conditions. The optimum temperature, pH value and inoculum size were found to be 33 °C, 6.06 and 13 %, respectively. In the conditions, phenol degradation rate and biomass were predicted to be 96.97 % and 410.78 mg/L within the range examined, respectively. Less toxic acetaldehyde, ethanol and acetic ether were identified as main intermediate products from the degraded samples using GC–MS. Substrate inhibition was calculated from experimental biomass growth and phenol degradation parameters using the Haldane equation. Kinetic parameters derived from nonlinear regression with correlation factors (R 2) were 0.9682 for phenol degradation and 0.9594 for biomass growth, respectively. The phenol concentration to avoid substrate inhibition was 278.17 mg/L. 相似文献
890.
Jianxiu Wang Tianrong Huang Jian Hu Lingao Wu Guo Li Ping Yang 《Environmental Earth Sciences》2014,71(7):3245-3257
A whirlpool foundation pit is a small-diameter, deep circular pit. Because of its depth and small diameter, a large drawdown is required, and a limited number of wells can be installed inside the pit. During excavation, partially penetrating wells inside and outside the foundation pit have to be installed to lower the water level when the aquifer is too thick. However, partially penetrating wells near partially penetrating curtains cannot be treated by analytical methods. Therefore, it is necessary to use numerical methods to predict dewatering during excavation. Field experiments were performed on whirlpool foundation pit 1880 of Baosteel Group, Shanghai, China, to obtain pumping rates and drawdown, pumping with a single well and two wells in the confined aquifer. The results indicate that the drawdown inside the pit induced by pumping wells outside the foundation pit was small, whereas it was large for pumping wells inside the pit. The pumping wells inside and outside the pit had to be combined to lower the water level. A three-dimensional numerical model was developed to simulate the dewatering process. The hydraulic conductivities of the confined aquifers were inversed by using the pumping tests. Operation schedules were simulated with the corrected model for different combinations of wells inside and outside the pit. The results suggest that different schedules and operation conditions affect drawdown. The monitored results during dewatering indicate that the simulation and field measurements were in agreement. The results can be applied to similar situations. 相似文献