通过影响高度多路径质量控制改进热带对流层低层GPS掩星资料同化效果          下载免费PDF全文

邹晓蕾  刘辉 《大气科学学报》2020,43(1):116-127

与观测气象、电离层和气候的GPS卫星计划COSMIC-1相比,COSMIC-2有更大功率的GPS接收天线,高2倍的采样率(100 Hz),小3倍的轨道倾角(24°)。因此,COSMIC-2和未来小卫星将为热带地区提供前所未有的大量无线电掩星观测资料。因为热带对流层低层水汽含量高,折射率有局地大梯度,违背大气球对称性假定,造成影响多路径现象,所以热带地区的掩星资料同化具有较大挑战性。本文首先利用之前研究中提出的影响参数多路径质量控制方法,去除热带对流层低层弯角模拟中出现影响参数多路径现象的资料,然后使用有限射线长度二维(2D)路径追踪观测算子和一维(1D)Abel变换观测算子,进行GPS弯角资料同化。结果表明,如果射线路径限制在离近地面点±300~400 km的水平距离以内,有限射线长度2D路径追踪观测算子得到的弯角模拟与2D射线追踪观测算子得到的弯角廓线之差不仅无偏,而且其标准差远比1D Abel的弯角模拟精度高。此外,无论采用1D Abel变换还是有限射线长度2D路径追踪观测算子来模拟弯角,影响参数多路径质量控制方案都能进一步改进GPS掩星弯角资料同化和预报精度。  相似文献   

误差订正对2018年夏季次季节尺度海冰预测的作用   总被引：1，自引：1，他引：0  

赵杰臣  舒启  李春花  吴兴仁  宋振亚  乔方利 《海洋学报(英文版)》2020,39(9):50-59

北极海冰次季节尺度预测在针对破冰船和商船的实际服务中十分重要，但常常受制于气候模拟的模拟能力。本研究提出了一种误差订正方法并分别应用到两个气候模式：海洋一所地球系统模式（FIOESM）和美国国家环境预报中心（NCEP）的气候预报系统（CFS），来改善北极海冰60天尺度的预测。本研究的预测工作是中国第9次北极科学考察和2018年夏季中远集团北极商业航行的业务化海冰服务保障的重要部分。模式起报时间分别是2018年7月1日、8月1日和9月1日，预报时效均是60天。结果显示，FIOESM整体上低估了海冰密集度的数值，平均偏差可达30%。误差订正对海冰密集度（SIC）的均方根偏差（RMSE）的改进比例可达27%，对海冰外缘线（SIE）的整体偏差（IIEE）的改进比例为10%。而对于CFS，SIE在边缘区域的过高估计是其主要特点。误差订正导致了SIC的RMSE改进了7%，而对SIE的IIEE改进了17%。在海冰范围预测方面，FIOESM预测的最小范围数值和时间点都和观测接近，而CFS的预测结果偏差较大。另外和其他S2S模式的结果比较发现，本研究提出的误差订正方法对存在较大偏差的预测结果改进更为有效。  相似文献   

Energy balance of the Deep Impact experiment     

O. Groussin  M. A’Hearn  T. Farnham  J. Kissel  J. Melosh  J. Sunshine 《Icarus》2010,205(2):627-637

We present results on the energy balance of the Deep Impact experiment based on analysis of 180 infrared spectra of the ejecta obtained by the Deep Impact spacecraft. We derive an output energy of 16.5 (+9.1/−4.1) GJ. With an input energy of 19.7 GJ, the error bars are large enough so that there may or may not be a balance between the kinetic energy of the impact and that of outflowing materials. Although possible, no other source of energy other than the impactor or the Sun is needed to explain the observations. Most of the energy (85%) goes into the hot plume in the first few seconds, which only represents a very small fraction (<0.01%) of the total ejected mass. The hot plume contains 190 (+263/−71) kg of H₂O, 1.6 ± 0.5 kg of CO₂, 8.2 (+11.3/3.1) kg of CO (assuming a CO/H₂O ratio of 4.3%), 27.9 (+25.0/−8.9) kg of organic material and 255 ± 128 kg of dust, while the ejecta contains ∼10⁷ kg of materials. About 12% of the energy goes into the ejecta (mostly water) and 3% to destroy the impactor. Volatiles species other than H₂O (CO₂, CO or organic molecules) contribute to <7% of the energy balance. In terms of physical processes, 68% of the energy is used to accelerate grains (kinetic energy), 16% to heat them, 6% to sublimate or melt them and 10% (upper limit) to break and compress dust and/or water ice aggregates into small micron size particles. For the hot plume, we derive a dust/H₂O ratio of 1.3 (+1.9/−1.0), a CO₂/H₂O ratio of 0.008 (+0.009/−0.006), an organics/H₂O ratio of 0.15 (+0.29/−0.11) and an organics/dust ratio of 0.11 (+0.30/−0.07). This composition refers to the impact site and is different from that of the bulk nucleus, consistent with the idea of layers of different composition in the nucleus sub-surface. Our results emphasize the importance of laboratory impact experiments to understand the physical processes involved at such a large scale.  相似文献   

Is the Isentropic Surface Always Impermeable to the Potential Vorticity Substance?     

Chanh Q. KIEU  Da-Lin ZHANG 《大气科学进展》2012,29(1):29-35

The impermeability of isentropic surfaces by the potential vorticity substance (PVS) has often been used to help understand the generation of potential vorticity in the presence of diabatic heating and friction.In this study,we examined singularities of isentropic surfaces that may develop in the presence of diabatic heating and the fictitious movements of the isentropic surfaces that are involved in deriving the PVS impermeability theorem.Our results show that such singularities could occur in the upper troposphere as a result of intense convective-scale motion,at the cloud top due to radiative cooling,or within the well-mixed boundary layer.These locally ill-defined conditions allow PVS to penetrate across an isentropic surface.We conclude that the PVS impermeability theorem is generally valid for the stably stratified atmosphere in the absence of diabatic heating.  相似文献   

Tracking a tropical cyclone through WRF–ARW simulation and sensitivity of model physics     

Tanvir Islam  Prashant K. Srivastava  Miguel A. Rico-Ramirez  Qiang Dai  Manika Gupta  Sudhir K. Singh 《Natural Hazards》2015,76(3):1473-1495

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Predicting dissolved oxygen in the Chesapeake Bay: applications and implications     

M. Bala Krishna Prasad  Wen Long  Xinsheng Zhang  Robert J. Wood  Raghu Murtugudde 《Aquatic Sciences - Research Across Boundaries》2011,73(3):437-451

Eutrophic depletion of dissolved oxygen (DO) and its consequences for ecosystem dynamics have been a central theme of research, assessment and management policies for several decades in the Chesapeake Bay. Ongoing forecast efforts predict the extent of the summer hypoxic/anoxic area due to nutrient loads from the watershed. However, these models neither predict DO levels nor address the intricate interactions among various ecological processes. The prediction of spatially explicit DO levels in the Chesapeake Bay can eventually lead to a reliable depiction of the comprehensive ecological structure and functioning, and can also allow the quantification of the role of nutrient reduction strategies in water quality management. In this paper, we describe a three dimensional empirical model to predict DO levels in the Chesapeake Bay as a function of water temperature, salinity and dissolved nutrient concentrations (TDN and TDP). The residual analysis shows that predicted DO values compare well with observations. Nash–Sutcliffe efficiency (NSE) and root mean square error-observations standard deviation ratio (RSR) are used to evaluate the performance of the empirical model; the scores demonstrate the usability of model predictions (NSE, surface layer = 0.82–0.86; middle layer = 0.65–0.82; bottom layer = 0.70–0.82; RSR surface layer = 0.37–0.44; middle layer = 0.43–0.58 and bottom layer = 0.43–0.54). The predicted DO values and other physical outputs from downscaling of regional weather and climate predictions, or forecasts from hydrodynamic models, can be used to forecast various ecological components. Such forecasts would be useful for both recreational and commercial users of the Chesapeake Bay.  相似文献   

Managing the transition to climate stabilization     

RICHARD G. RICHELS  THOMAS F. RUTHERFORD  GEOFFREY J. BLANFORD  LEON CLARKE 《Climate Policy》2013,13(5):409-428

It is becoming increasingly clear that economically efficient climate policies are unlikely to be implemented in the near term. Therefore an analysis is warranted that considers the implications of certain suboptimal transition policies. This analysis constructs a transition scenario based on realistic assumptions about the current trends in policy-making. The transition is examined in the context of varying assumptions about the stringency of the target and the availability of low- or no-carbon energy technologies in the future. In addition to evaluating the effects of suboptimal policies, the transitional analysis offers new insights about the intrinsic uncertainty regarding both the appropriate stabilization target and technology.  相似文献   

基于静风期污染物的PM2.5排放清单空间精细化方法     

钟雨桐  韦晶  郑月明  阎福礼 《地球信息科学学报》2021,23(11):1971-1983

有利气象条件之后的静风期,极大降低了PM_2.5跨区域传输的影响,能够揭示本地源的排放状况。本文尝试性引入了静风期污染物分布揭示本地源排放特征的概念,提出了一种基于遥感数据的PM_2.5排放清单空间精细化方法：首先,利用 MODIS MCD19A2反演的ChinaHighPM_2.5数据,构建高时空分辨率PM_2.5数据融合方法;然后,构建唐山市有利气象条件之后的静风期污染物遴选方法（合理风向和风速：有利气象条件为东风,地面10 m高度风速大于3 m/s,其他风向,持续的较大风力5~10 m/s;静风期风速小于1.5~2.0 m/s）;其次,基于遴选的静风期PM_2.5数据分配MEIC清单中的PM_2.5总排放量,同时对比传统插值方法：基于GDP、人口密度、路网、土地利用类型数据,实现清单各污染源PM_2.5的1 km×1 km空间分配;最后,利用WRF-CMAQ模拟数据和地面台站实测数据进行真实性检验。研究结果表明：① PM_2.5数据填补融合方法能够有效提高PM_2.5监测数据的时空分辨率,且与地面监测值显著相关（R²=0.94,RMSE=4.64 µg/m³,NMB=2%,NME=7%）;② 引入有利气象条件后的静风期概念,提出了静风期污染物的遴选方法,有效降低了PM_2.5跨区域传输的影响,更好地反映了本地源排放的空间分布特征;③ WRF-CMAQ模拟方法的精度验证结果表明,该方法较传统面积插值法NME降低7%,NMB降低10%,RMSE降低1.54 µg/m³,R²提高11%。该方法为排放清单的空间精细化提供了新的研究思路。  相似文献   

Can radiative forcing be limited to 2.6 Wm−2 without negative emissions from bioenergy AND CO2 capture and storage?     

James Edmonds  Patrick Luckow  Katherine Calvin  Marshall Wise  Jim Dooley  Page Kyle  Son H. Kim  Pralit Patel  Leon Clarke 《Climatic change》2013,118(1):29-43

Combining bioenergy and carbon dioxide (CO₂) capture and storage (CCS) technologies (BECCS) has the potential to remove CO₂ from the atmosphere while producing useful energy. BECCS has played a central role in scenarios that reduce climate forcing to low levels such as 2.6 Wm^?2. In this paper we consider whether BECCS is essential to limiting radiative forcing (RF) to 2.6 Wm^?2 by 2100 using the Global Change Assessment Model, a closely coupled model of biogeophysical and human Earth systems. We show that BECCS can potentially reduce the cost of limiting RF to 2.6 Wm^?2 by 2100 but that a variety of technology combinations that do not include BECCS can also achieve this goal, under appropriate emissions mitigation policies. We note that with appropriate supporting land-use policies terrestrial sequestration could deliver carbon storage ranging from 200 to 700 PgCO₂-equiavalent over the 21st century. We explore substantial delays in participation by some geopolitical regions. We find that the value of BECCS is substantially higher under delay and that delay results in higher transient RF and climate change. However, when major regions postponed mitigation indefinitely, it was impossible to return RF to 2.6 Wm^?2 by 2100. Neither finite land resources nor finite potential geologic storage capacity represented a meaningful technical limit on the ability of BECCS to contribute to emissions mitigation in the numerical experiments reported in this paper.  相似文献   

The effect of global climate change, population distribution, and climate mitigation on building energy use in the U.S. and China     

Yuyu Zhou  Jiyong Eom  Leon Clarke 《Climatic change》2013,119(3-4):979-992

Climate change will affect the energy system in a number of ways, one of which is through changes in demands for heating and cooling in buildings. Understanding the potential effect of climate change on heating and cooling demands requires taking into account not only the manner in which the building sector might evolve over time, but also important uncertainty about the nature of climate change itself. In this study, we explore the uncertainty in climate change impacts on heating and cooling requirement by constructing estimates of heating and cooling degree days (HDD/CDDs) for both reference (no-policy) and 550 ppmv CO₂ concentration pathways built from three different Global Climate Models (GCMs) output and three scenarios of gridded population distribution. The implications that changing climate and population distribution might have for building energy consumption in the U.S. and China are then explored by using the results of HDD/CDDs as inputs to a detailed, building energy model, nested in the long-term global integrated assessment framework, Global Change Assessment Model (GCAM). The results across the modeled changes in climate and population distributions indicate that unabated climate change would cause building sector’s final energy consumption to decrease modestly (6 % decrease or less depending on climate models) in both the U.S. and China by the end of the century as decreased heating consumption more than offsets increased cooling using primarily electricity. However, global climate change virtually has negligible effect on total CO₂ emissions in the buildings sector in both countries. The results also indicate more substantial implications for the fuel mix with increases in electricity and decreases in other fuels, which may be consistent with climate mitigation goals. The variation in results across all scenarios due to variation of population distribution is smaller than variation due to the use of different climate models.  相似文献