Statistical characteristics of chlorophylla concentration in Hong Kong’s coastal waters

In this paper seven of the ten Water Control Zones (WCZs) in Hong Kong’s coastal waters with monthly or bi-weekly sampling data of 17 parameters collected at 37 monitoring stations from 1988 to 1999 were selected to analyze the spatial and temporal variations of chlorophyll-a and its influencing factors. Cluster analysis was employed to group the monitoring stations based on the structure of the data set. Multiple step regression was employed to determine the significant influencing factors of chlorophyll-a level. The results suggest that all the monitoring stations could be grouped into two clusters. Cluster I with frequent red tide incidents comprises two WCZs which are semi-enclosed bays. Cluster II with less red tide occurrence comprises the other five WCZs in an estuarine environment in the west. For both clusters, the organic contents indicator, BOD5, was a common significant influencing factor of the chlorophyll-a level. Nitrogen and light penetration condition related to turbidity, total volatile solids and suspended solids had more influence on the cholophyll-a level in Cluster I than in Cluster II, while phosphorus and oceanographic conditions associated with salinity, temperature, dissolved oxygen and pH were more important in Cluster II than in Cluster I. Generally, there was a higher average chlorophyll-a level in winter and autumn in a year. The chlorophyll-a level was much higher in Cluster I than in Cluster II among all seasons. Although the chlorophyll-a concentration had great variations from place to place in Hong Kong’s coastal waters, it seemed to have a common long term fluctuation period of 8–10 years with a high-low-high variation in the period in the whole region, which might be influenced by other factors of global scale.     

太平洋大尺度环流数值模拟 Ⅲ：季节变化

本文在年平均环流数值模拟基础上,用季节变化的大气强迫场又积分了12年,并对由模拟得到的太平洋海面起伏、洋流、温度、海表热通量和上层热储存率等的季节变化特征作了较为详细的阐述和与已有观测结果进行了比较,事实证明,模式基本上模拟出了观测到的太平洋大尺度环流基本特征及其季节变化,证实基于理论考虑设计的IAP OGCM模式具有较好的性能和对实际环流的模拟能力,有些结果并优于国外一些具有同等分辨率的海洋模式。     

利用、振幅比资料测定澜沧—耿马震区中、小地震震源机制

本文采用P、S最大振幅比资料测定中、小地震震源机制参数的方法,测定了澜沧—耿马地震前后震区182个中、小震的震源机制参数。并将这些结果结合大震及强余震震源机制P波初动解,对大震前后震区应力场方向的时空调整变化,以及序列的震源错动性质等进行了分析和讨论。     

利用深井观测速度型记录的最大振幅测定近震震级的一种方法

根据上海台网观测记录到的上海及邻近地区1985年至1990年期间179次地震事件的资料,以虹桥台、南汇台的两口深井观测地震记录为例,探讨如何利用深井观测速度型记录的最大振幅来测定近震震级。对于400公里以内的地震,本文根据统计规律,提出:在已知系统速度灵敏度K,地震记录的最大振幅A和地震震中距Δ的前提下,速度型记录的近震震级可以表示为M_v=logA/K+blog(Δ)+c误差分析表明,M_v与M_L是比较接近的,结果是可用的。     

本世纪中国西北地区的干旱变化

本文分析了陕西、甘肃、宁夏、青海和新疆五省区有气象观测资料以来的干旱变化,并与历史时期的变化做了比较。同时还对该地区干旱变化与气温的关系作了分析。     

Wave to wave and wave to zonal mean flow kinetic energy exchanges during contrasting monsoon years

Fourier analysis of the monthly mean northern hemispheric geopotential heights for the levels 700 mb and 300 mb are undertaken for the months of April through to August. The wave to wave and wave to zonal mean flow kinetic energy interactions are computed for specified latitude bands of the northern hemisphere during the pre-monsoon period (April to May) and monsoon period (June through to August) for bad monsoon years (1972, 1974, 1979) and for years of good monsoon rainfall over India (1967, 1973, 1977). Planetary scale waves (waves 1 to 4) are the major kinetic energy source in the upper atmosphere during the monsoon months. Waves 1 and 2 in particular are a greater source of kinetic energy to other waves via both wave to wave interactions as well as wave to zonal mean flow interactions in good monsoon years than in bad monsoon years. The zonal mean flow shows significantly larger gains in the kinetic energy with a strengthening of zonal westerlies in good monsoon years than in bad monsoon years.     

Mismatch between variations of solar indices, stratospheric ozone and UV-B observed at ground

In solar cycles 22–23, all solar indices showed maxima near 1990 and 2000 and minima in 1996. The maximum to minimum variation was only 1–2% in the UV range 240–350 nm. Dobson ozone intensities did not show any clear relationship with solar cycle and ozone variations were less than 10%. The UV-B (295–325 nm) observed at ground by Brewer spectrophotometers at some locations had variations of 50–100% for 295–300 nm, and 20–50% for 305–325 nm. The maxima were in different years at different locations (even with separations of only 300 km), did not match with the solar cycle, and were far too large to be explained on the basis of ozone changes (1% decrease of ozone is expected to cause 2% increase of UV-B). Thus, if the data are not bad, the UV-B changes do not match with solar activity or ozone changes and must be mostly due to other local effects (clouds, etc.?). When data are averaged over wide geographical regions, UV-B variation ranges are smaller (10–20%, probably because localised, highly varying cloud effects get filtered out), and are roughly as expected from ozone variations.     

苏南地区夏季面雨量与北半球500hPa环流遥相关的年代际变化

用40年（1961－2000年）观测资料，分成1951－1980年和1981－2000年两个时段，研究了江苏南部地区夏季（6－8月）面积平均雨量与北半球500hPa季平均环流时滞遥相关的年代际变化。结果表明这两个时段遥相关的空间分布存在显著差异，且后一时期时滞遥相关强度明显强于前一时期，它反映了北太平洋年代际振荡（PDO）对东亚季风降水和环流年际相关的影响，与年代际和年际时间尺度振荡之间的相互作用有密切联系。