Multi-level temporal autoregressive modelling of daily activity satisfaction using GPS-integrated activity diary data

In this research, we match web-based activity diary data with daily mobility information recorded by GPS trackers for a sample of 709 residents in a 7-day survey in Beijing in 2012 to investigate activity satisfaction. Given the complications arising from the irregular time intervals of GPS-integrated diary data and the associated complex dependency structure, a direct application of standard (spatial) panel data econometric approaches is inappropriate. This study develops a multi-level temporal autoregressive modelling approach to analyse such data, which conceptualises time as continuous and examines sequential correlations via a time or space-time weights matrix. Moreover, we manage to simultaneously model individual heterogeneity through the inclusion of individual random effects, which can be treated flexibly either as independent or dependent. Bayesian Markov chain Monte Carlo (MCMC) algorithms are developed for model implementation. Positive sequential correlations and individual heterogeneity effects are both found to be statistically significant. Geographical contextual characteristics of sites where activities take place are significantly associated with daily activity satisfaction, controlling for a range of situational characteristics and individual socio-demographic attributes. Apart from the conceivable urban planning and development implications of our study, we demonstrate a novel statistical methodology for analysing semantic GPS trajectory data in general.     

Solubility of HOCl in water and aqueous H2SO4 to stratospheric temperatures

Henry's law constants K_H (mol kg^–1 atm^–1) for the reaction HOCl_(g)=HOCl_(aq) near room temperature, literature data for the associated enthalpy change, and solubilities of HOCl in aqueous H₂SO₄ (46 to 60 wt%) at temperatures relevant to the stratosphere (200 KT230 K) are shown to be thermodynamically consistent. Effective Henry's law constants [H*=mHOCl/pHOCl, in mol kg^–1 atm^–1] of HOCl in aqueous H₂SO₄ are given by: ln(H*)=6.4946–mH₂SO₄(–0.04107+54.56/T)–5862 (1/T_o–1/T) where T(K) is temperature and T_o=298.15K. The activity coefficient of HOCl in aqueous H₂SO₄ has a simple Setchenow-type dependence upon H₂SO₄ molality.     

Modeling spatiotemporal topological relationships between moving object trajectories along road networks based on region connection calculus

Considering the attempts to model spatiotemporal topological relationships between moving object trajectories, the conceptual and computational framework for moving objects along a road network has not received much attention. This paper aims to draw an improved model based on Region Connection Calculus (RCC) theory to represent the spatiotemporal topological relationships between moving object trajectories along road networks. This paper first uses a dimension reduction method based on a linear-reference transformation to model the moving object trajectories segments, and then defines new time–connection and space–connection relations between two trajectory segments. On this basis, the paper proposes an extension to the RCC-based spatiotemporal binary relationship set so that the combined semantics of the spatiotemporal predicates can be described completely. A case study was carried out using Floating Car Data in Guangzhou city. The computational results show that in a real application, the occurrence frequencies of the RCC-based binary relationships are distributed nonuniformly and the semantics of some binary relationships with the highest occurrence are coarse. Therefore, the partition of the spatiotemporal connection relations and the finer aspects of the spatiotemporal relationship model may require further research work.     

1997年和2011年春季北极臭氧损耗事件的对比分析

采用SLIMCAT化学传输模式以及再分析资料,对比分析了1997和2011年北极地区平流层臭氧异常偏低事件及其成因。结果表明,1997和2011年3月北极地区大气臭氧柱总量（TCO）异常值都达到了约-80 DU,并且在30-200 hPa（中下平流层）区域的大气臭氧柱总量异常约占整层大气臭氧柱总量异常的80%。分析表明发生在这两年的极端臭氧偏低事件均可能是由于上一年冬季的拉尼娜事件导致上传的行星波减少,使得北极极涡加强,平流层温度异常偏低,生成了更多极地云,引起更强的臭氧化学损耗导致的。对比这两年的大气臭氧柱总量变化发现,2011年的柱总量减少得更快。2011年北极地区上对流层下平流层（UTLS）区域臭氧下降要明显强于1997年,其主要原因应该是2010-2011冬季的拉尼娜活动更强,北太平洋海温更高,进一步减弱阿留申低压和平流层波活动。这导致2011年极涡温度异常偏低更强烈,形成了更多的极地平流层云甚至出现了第二类极地平流层云,最终加速该年春季的臭氧化学损耗引起的。     

合肥地区平流层气溶胶地基激光雷达与SAGE卫星探测比较

为了解中国上空SAGE反演的平流层气溶胶数据质量,将合肥地区地基激光雷达观测10年(1996年—2005年)的气溶胶数据与SAGE资料进行比较。通过较为系统全面的比较分析,得到如下结果:(1)10—30 km内SAGE与Li DAR分析的气溶胶变化趋势较为一致,出现峰值和低值的位置也较为接近;(2)SAGE结果普遍比Li DAR测量的偏小,对应的平流层气溶胶AOD差异显著,定量表现为:激光雷达获取的平流层气溶胶AOD基本约为0.004,SAGE反演的平流层气溶胶AOD基本约为0.002,只有前者的一半;(3)两者分析的20—35 km气溶胶季节分布差异较小,再次表明平流层气溶胶比较稳定。     

Numerical simulation of larval shrimp dispersion in the Northern Region of the Gulf of California

The trajectories of shrimp larvae in the northern part of the Gulf of California were studied from a Lagrangian point of view using a three-dimensional numerical model. The advection of particles was carried out over fortnightly periods starting at spring and neap tides. The northernmost region of the gulf has important shrimp fisheries and nursery areas have been located off the coast of Baja California at San Felipe (SF) and off the Sonora coast at Santa Clara (SC). Though the reproduction zone is believed to be south of these nursery areas, there is much that remains unknown about the zone and the routes used by shrimps to reach these areas. Passive and active simulations of shrimp larvae drift were carried out in order to study the possible areas of shrimp spawning and their migratory routes. The active migration schemes were based on assumptions that the larvae can be advected only: (1) during the day, (2) at night or (3) when the currents flow in the northward direction toward the nursery areas. It was found that the larvae in Santa Clara and San Felipe came from different production zones. No differences were found between the spring and neap tide scenarios except for the diurnal migration experiments. The distance traveled by shrimp larvae was always less than 40–50 km, except in the cases when the larvae selected the appropriate direction to the nursery areas when the larvae travel 140 km to SC and 95 km to SF.     

Assessment of water exchange between a discharge region and the open sea – A comparison of different methodological concepts

Two different methods of estimating the water exchange through the Baltic coastal region of Laxemar have been used, consisting of particle trajectories and passive tracers. Water is traced from and to a small discharge region near the coast. The discharge material in this region is treated as zero-dimensional particles or tracers with neutral buoyancy. The real discharge material could be a leakage of radio-nuclides through the sea floor from an underground repository of nuclear waste.Water exchange rates between the discharge region and the model domain are estimated using both forward and backward trajectories as well as passive tracers. The Lagrangian trajectories can account for the time evolution of the water exchange while the tracers give one average age per model grid box. Water exchange times such as residence time, age and transient times have been calculated with trajectories but only the average age (AvA) for tracers. The trajectory calculations provide a more detailed time evolution than the tracers.On the other hand the tracers are integrated “on-line” simultaneously in the sea circulation model with the same time step while the Lagrangian trajectories are integrated “off-line” from the stored model velocities with its inherent temporal resolution, presently 1 h. The sub-grid turbulence is parameterised as the Laplacian diffusion for the passive tracers and with an extra stochastic velocity for trajectories. The importance of the parameterised sub-grid turbulence for the trajectories is estimated to give an extra diffusion of the same order as the Laplacian diffusion by comparing the Lagrangian dispersions with and without parameterisation. The results of the different methods are similar but depend on the chosen diffusivity coefficient with a slightly higher correlation between trajectories and tracers when integrated with a lower diffusivity coefficient.     

Analysis and Simulation of the Stratospheric Quasi-zero Wind Layer over Korla,Xinjiang Province,China

The stratospheric quasi-zero wind layer (QZWL) is a transition region with low zonal wind speeds in the lower stratosphere at an altitude of ~20 km. The zonal wind direction above the QZWL layer is opposite to that below the QZWL layer and the north–south wind component is small. The atmospheric wind field near the stratospheric QZWL is an important factor affecting the flight altitude and dynamic control of stratospheric airships. It is therefore necessary to study the stratospheric QZWL to provide better environmental information for these aircraft. High-resolution radiosonde data were used to analyze the characteristics of the stratospheric QZWL over Korla, Xinjiang Province, China. A weak wind layer in which the wind direction suddenly reversed from westerly to easterly was observed at ~20 km in the lower stratosphere, characteristic of the stratospheric QZWL. The Weather Research and Forecasting model was used to simulate the profiles of the horizontal wind speed and direction over Korla. The forcing effect of each diagnostic term in the equation on the zonal wind speed was analyzed. The results showed that the advection term was the dominant factor forcing the zonal wind speed. The wave term had a secondary forcing role, although the forcing effect of the wave term on the zonal wind speed was significant in some regions.     

曲率积分约束的GPS浮动车地图匹配方法

提出了以轨迹曲线的曲率积分值作为地图匹配特征的匹配方法,利用轨迹曲率积分值约束前后相邻轨迹点的关联匹配,采用不同类型行驶路径以及不同采样间隔,实施了浮动车地图匹配试验,结果表明,以匹配正确率和稳定性评判,本文提出的曲率积分约束的浮动车地图匹配方法优于现有的未采用曲率特征匹配的经典浮动车地图匹配方法。     

Longitudinal analysis of the road network development and land-cover change in Lop Buri province, Thailand, 1989-2006

Land use and land-cover change (LUCC) is mainly a consequence of human activities such as road network development. In Thailand, the explicit objective of road network development has been to foster economic and social development. The extent of change in roads and land-cover change in Lop Buri between 1989-2006 is analyzed. We hypothesized that road development is a key driver of land-cover change and will cause, substantial changes in areas of forest cover, cultivated food and cash crops. We used land-cover classifications of Landsat imagery and resultant class trajectories to measure change. We then analyzed the relationships between roads, land-cover types, and land-cover trajectories. Overall, cash crops increased while forest and food crops declined between 1989-2006. The relationships between distance to roads and land- cover trajectories indicate that as the distance to roads increase, there are fewer changes in LUCC. The results suggest that in this case study, an increase in road network contributes to an increase in upland crops. In turn, the increase in upland crop production is one of the factors linked to economic development.