昆明地区南墙面上小时太阳辐射量的计算

以昆明地区的南向墙面为例,模拟计算了两分、两至日的小时太阳辐射量随时间的变化关系.经计算机辅助计算得:四个典型日的最大负荷都出现在中午十二点附近.其中,春分日的最大瞬时辐射量为1.84 MJ/m2;夏至日的最大瞬时辐射量为0.59 MJ/m2;秋分日和冬至日的辐射量分别为1.81 MJ/m2和2.05 MJ/m2.     

Changes in global potential vegetation distributions from 1911 to 2000 as simulated by the Comprehensive Sequential Classification System approach

Vegetation classification models play an important role in studying the response of the terrestrial ecosystem to global climate change. In this paper, we study changes in global Potential Natural Vegetation (PNV) distributions using the Comprehensive Sequential Classification System (CSCS) approach, a technique that combines geographic information systems. Results indicate that on a global scale there are good agreements among maps produced by the CSCS method and the globally well-accepted Holdridge Life Zone (HLZ) and BIOME4 PNV models. The potential vegetation simulated by the CSCS approach has 6 major latitudinal zones in the northern hemisphere and 2 in the southern hemisphere. In mountainous areas it has obvious altitudinal distribution characteristics due to topographic effects. The distribution extent for different PNV classes at various periods has different characteristics. It had a decreasing trend for the tundra and alpine steppe, desert, sub-tropical forest and tropical forest categories, and an increasing trend for the temperate forest and grassland vegetation categories. The simulation of global CSCS-based PNV classes helps to understand climate-vegetation relationships and reveals the dynamics of potential vegetation distributions induced by global changes. Compared with existing statistical and equilibrium models, the CSCS approach provides similar mapping results for global PNV and has the advantage of improved simulation of grassland classes.     

The application of large volume airgun sources to the onshore-offshore seismic surveys： implication of the experimental results in northern South China Sea

Onshore-offshore seismic experiments were carried out for the first time in northern South China Sea using large volume airgun sources at sea and seismic stations on land. The experimental results indicate that seismic signals from the new airgun array of R/V Shiyan 2 can be detected as far as 255 km. The signal effective area reaches nearly 50000 km2, which covers Hong Kong and Pearl River Delta. Compared with the old airgun array, the signal amplitude, propagation distance and effective area of the new airgun array have been increased notably, which demonstrates that the upgrade of the airgun source was successful. Comparisons with previous experimental results in other regions show that the shooting effect of the new airgun array is similar to those best airgun sources in the world. Especially, it is a new breakthrough in using the permanent seismic stations onshore to record long distance airgun signals offshore, which has great significance to the realization of the "seismic radar" concept and the 3D seismic surveys of crustal structure in coastal areas.