卫星高光谱大气CO2探测精度验证研究进展

卫星高光谱大气CO₂遥感探测对全球气候变化研究意义重大,卫星CO₂反演产品的地基观测验证是获得产品精度评价、发现算法可适用范围和局限性的重要环节,因此地基高光谱CO₂的观测验证研究对提高卫星产品定量精度至关重要。本文综述了当前国际上大气CO₂探测卫星的研制进展,短波红外大气CO₂的反演方法进展,重点阐述了地基高光谱CO₂探测技术进展及其对卫星大气CO₂的定量探测精度验证方法和技术研究进展,并对该研究领域未来的发展提出展望。     

中国近海海面高度异常资料再处理

卫星海面高度异常产品再处理的研究多集中在欧洲和美国近海,中国近海尚未有过。在产生AVISO(Archiving Validation and Interpolation of Satellite Oceanographic Data)全球0.25°多颗卫星海面高度异常产品时,只用了1/3~1/2的部分沿轨资料,给区域海洋动力学研究造成了一定的限制。本研究尝试利用多颗卫星的所有沿轨资料及25个测潮站的观测资料,通过最优插值方法产生一份新的中国近海海面高度异常资料。新资料的空间分辨率仍为0.25°,但使用了来自3颗卫星(Jason-1、Jason-2、Cryo Sat-2)的所有沿轨资料及25个测潮站的观测资料。新资料的范围为10°S~50°N、90°~160°E。新资料与AVISO资料的对比分析表明新资料更接近沿轨海面高度异常观测,同时也更接近测潮站资料。与AVISO资料相比,新资料与沿轨海面高度异常观测的均方根误差降低了10.03%,与测潮站资料的均方根误差降低了9.6%。     

Geocoding crime and a first estimate of a minimum acceptable hit rate

The Fuzzy Kappa statistic expresses the agreement between two categorical raster maps. The statistic goes beyond cell‐by‐cell comparison and gives partial credit to cells based on the categories found in the neighborhood. When matching categories are found at shorter distances the agreement is higher. Like the well‐established Kappa statistic the Fuzzy Kappa statistic expresses the mean agreement relative to the expected agreement. The model underlying the expected agreement assumes absence of spatial autocorrelation in both compared maps. In reality however, spatial autocorrelation does lower the expected agreement as matching categories become less likely to be found close‐by. Since most maps have some degree of spatial autocorrelation, the calculated expected agreement is generally higher than the true expected agreement. This leads to counterintuitive results when maps that appear to have considerable agreement obtain negative Fuzzy Kappa values. Furthermore, the Fuzzy Kappa may be biased, as it systematically attributes lower agreement to maps with stronger spatial autocorrelation. This paper proposes an improved Fuzzy Kappa statistic that is based on the same local agreement and has the same attractive properties as the original Fuzzy Kappa. The novelty is that the new statistic accounts for spatial autocorrelation, such that the expected Fuzzy Kappa for maps that are not cross‐correlated is equal to zero. The improved statistic is applied on two cases to demonstrate its properties.     

Satellite surface soil moisture from SMOS and Aquarius: Assessment for applications in agricultural landscapes

Satellite surface soil moisture has become more widely available in the past five years, with several missions designed specifically for soil moisture measurement now available, including the Soil Moisture and Ocean Salinity (SMOS) mission and the Soil Moisture Active/Passive (SMAP) mission. With a wealth of data now available, the challenge is to understand the skill and limitations of the data so they can be used routinely to support monitoring applications and to better understand environmental change. This paper examined two satellite surface soil moisture data sets from the SMOS and Aquarius missions against in situ networks in largely agricultural regions of Canada. The data from both sensors was compared to ground measurements on both an absolute and relative basis. Overall, the root mean squared errors for SMOS were less than 0.10 m³ m⁻³ at most sites, and less where the in situ soil moisture was measured at multiple sites within the radiometer footprint (sites in Saskatchewan, Manitoba and Ontario). At many sites, SMOS overestimates soil moisture shortly after rainfall events compared to the in situ data; however this was not consistent for each site and each time period. SMOS was found to underestimate drying events compared to the in situ data, however this observation was not consistent from site to site. The Aquarius soil moisture data showed higher root mean squared errors in areas where there were more frequent wetting and drying cycles. Overall, both data sets, and SMOS in particular, showed a stable and consistent pattern of capturing surface soil moisture over time.     

44 Years Hindcast of the sea level and circulation in the Baltic Sea

The subject of the investigation was the multiyear hindcast of the sea level elevations and currents over the Baltic Sea. The approach follows to the HIPOCAS project conception and contained the 3D hydrodynamic model using boundary conditions from the atmosphere and catchment for 44-year period referring to the second half of the 20th century.     

Research on the Characteristics and Repeatability of Strong Earthquake Activity in Sichuan-Yunnan

According to the method for predicting strong earthquakes using seismicity patterns, this paper summarizes the seismicity anomalies, generally called anomalous seismicity patterns, as the basis for prediction based on some historical data in the Sichuan-Yunnan seismic zone. Using our results, it can be confirmed that these anomaly patterns, which reflect the features of the late stage of strong earthquake preparation process and stress release in the main shock rupture zone, did exist before many earthquake cases. This paper also introduced the characteristics of seismic repeatability and its validation result, and discussed the mechanism of repeatability, which will have an application value for strong earthquake tendency prediction.     

Validation of interannual simulations from the 1/8° global Navy Coastal Ocean Model (NCOM)

A 1/8° global version of the Navy Coastal Ocean Model (NCOM) is used for simulation of upper-ocean quantities on interannual time scales. The model spans the global ocean from 80°S to a complete Arctic cap, and includes 19 terrain-following σ- and 21 fixed z-levels. The global NCOM assimilates three-dimensional (3D) temperature and salinity fields produced by the Modular Ocean Data Assimilation System (MODAS) which generates synthetic temperature and salinity profiles based on ocean surface observations. Model-data intercomparisons are performed to measure the effectiveness of NCOM in predicting upper-ocean quantities such as sea surface temperature (SST), sea surface salinity (SSS) and mixed layer depth (MLD). Subsurface temperature and salinity are evaluated as well. An extensive set of buoy observations is used for this validation. Where possible, the model validation is performed between year-long time series obtained from the model and time series from the buoys. The statistical analyses include the calculation of dimensionless skill scores (SS), which are positive if statistical skill is shown and equal to one for perfect SST simulations. Model SST comparisons with year-long SST time series from all 83 buoys give a median SS value of 0.82. Model subsurface temperature comparisons with the year-long subsurface temperature time series from 24 buoys showed that the model is able to predict temperatures down to 500 m reasonably well, with positive SS values ranging from 0.18 to 0.97. Intercomparisons of MLD reveal that the model MLD is usually shallower than the buoy MLD by an average of about 15 m. Annual mean SSS and subsurface salinity biases between the model and buoy values are small. A comparison of SST between NCOM and a satellite-based Pathfinder data set demonstrates that the model has a root-mean-square (RMS) SST difference of 0.61 °C over the global ocean. Spatial variations of kinetic energy fields from NCOM show agree with historical observations. Based on these results, it is concluded that the global NCOM presented in this paper is able to predict upper-ocean quantities with reasonable accuracy for both coastal and open ocean locations.     

The impact of freshwater discharges on the ocean circulation in the Skagerrak/northern North Sea area Part I: model validation

We assess the performance of an eddy-recognizing numerical ocean model in simulating the pattern and variability of the hydrography in the Skagerrak/northern North Sea area. The model we use is a version of the widely used Princeton ocean model employing a terrain-following vertical coordinate. Results from a series of five multi-year simulations of the mesoscale response are described. The simulations differ in their representation of the lateral freshwater supply to the model ocean of which the first is a reference simulation. The next four are variations in which the river discharges and/or the Baltic outflow are given more realistic representations. For validation, we have used in situ hydrographic data. A novelty is that we use the concepts of freshwater height and potential energy anomaly as objective validation tools. We find that, in general, the model faithfully reproduces many of the observed hydrographic features including their mean patterns and their variance. Not surprisingly, we find that the Baltic outflow is by far the most significant freshwater source in terms of its influence on the hydrography in the area, a result corroborating earlier findings. The best validation is obtained when all freshwater supply is made as realistic as possible, in particular the Baltic outflow. We also find that the large scale cyclonic circulation and the location of fronts are robust characteristics of the Skagerrak/northern North Sea circulation given the impact changes in the freshwater input has on the hydrography. Finally, we find that a further exploration of the impact of the lateral open boundary forcing, e.g., the input of Atlantic water, is needed.     

Validation of Spatial Prediction Models for Landslide Hazard Mapping

This contribution discusses the problemof providing measures of significance ofprediction results when the predictionswere generated from spatial databases forlandslide hazard mapping. The spatialdatabases usually contain map informationon lithologic units, land-cover units,topographic elevation and derived attributes(slope, aspect, etc.) and the distributionin space and in time of clearly identifiedmass movements. In prediction modelling wetransform the multi-layered databaseinto an aggregation of functional values toobtain an index of propensity of the landto failure. Assuming then that the informationin the database is sufficiently representativeof the typical conditions in which the massmovements originated in space and in time,the problem then, is to confirm the validity ofthe results of some models over otherones, or of particular experiments that seem touse more significant data. A core pointof measuring the significance of a prediction isthat it allows interpreting the results.Without a validation no interpretation is possible,no support of the method or of theinput information can be provided. In particularwith validation, the added value canbe assessed of a prediction either in a fixedtime interval, or in an open-ended time orwithin the confined space of a study area.Validation must be of guidance in datacollection and field practice for landslidehazard mapping.     

GOALS/LASG模式对气候平均态的模拟

中国科学院大气物理研究所LASG最近发展了全球海洋 大气 陆面耦合气候模式系统 (GOALS)的新版本 ,实现了全球大气环流谱模式 (R42L9)与海洋环流模式 (T63L3 0 )在 40°S～ 40°N之间的开洋面上海 气通量交换的完全耦合。该模式系统已积分了 40a ,基本上不存在明显的气候漂移。文中通过对所模拟的后 3 0a平均的热带、副热带地区海温、海表风应力、洋面净通量和降水等的气候平均态与多种实测资料的对比分析 ,结果表明 ,GOALS模式基本上模拟再现了当今气候的一些主要特征 ,对热带气候平均态已具有一定的模拟能力 ,但也注意到 ,与观测相比 ,区域性差异是明显存在的 ,比如沿赤道西太平洋“暖池”区和靠近南美沿岸的东太平洋海域以及印度洋海表温度明显偏高约 2℃ ,所模拟的赤道东太平洋海温冷舌西伸明显 ,造成赤道中太平洋海温明显偏冷等偏差。这些模拟误差 ,与模式中海表风应力和洋面所得到或释放的净热通量有密切的关系。SST的模拟误差反过来也影响到对降水的模拟