Effects of water vapour on the structure parameter of the refractive index for near-infrared radiation   总被引：2，自引：2，他引：0  

A. F. Moene 《Boundary-Layer Meteorology》2003,107(3):635-653

The refractive index of air (n) mainly depends on temperature andwater vapour content. For near-infrared radiation, temperature isthe main determining factor. To determinethe structure parameter of temperature ( ) fromthe structure parameter of the refractive index( ), the influence ofwater vapour content on n needs to be taken into account as acorrection. Three levels of approximation are presented. The firstinvolves the standard deviations of T and q (_T and_q) as well as the correlation coefficient betweenT and q (R_Tq). The second approximation involvesR_Tq and the Bowen ratio (), and the last uses only the Bowen ratio.The latter is the classical Bowen ratio correction.Evaluation of the validity of the assumptions used in the derivationreveals that a large error may be introduced (for situations withR_Tq < 0.8) by replacing _T/_qwith the Bowen ratio.Consequently, estimating from using the Bowen ratiocan contain errors of 5–40% for || < 1. Adding R_Tqas extra information reduces the errors only marginally. For || > 1,the correction is small, and all three approximations give errors of lessthan 1% in . When is used to compute the sensible heat flux,the influence of the quality of the correction forwater vapour fluctuations on the measured energy balance is small: forsmall ||, the correction is large, but the absolute value ofthe heat flux is small, whereas for large ||, the correctionis insignificant.  相似文献   

Research Progresses and Prospect of Chimney Effect about Carbon Cycle in the Karst Cave System   总被引：4，自引：0，他引：4  

Luo Weijun Wang Shijie  Wang Shijie  Liu Xiuming 《地球科学进展》2014,29(12):1333-1340

There is a long history of several decades for the systemic study of global carbon cycles, and many important achievements have been obtained. However, these studies of carbon cycles in the karst area that accounts for about 10% of the entire Earth’s land area were paid attention gradually only in the past twenty. Recent researches suggest that karstification has important effects of the global carbon cycle. At present, scientists have had a very comprehensive and systemic understanding of various factors affecting the carbon cycle in the karst area, and estimated the carbon source or sink. However, unlike non karst area, there are generally many caves and fractures that have various sizes and morphologies in the karst area. These caves and fractures provide gas exchange between epikarst zone and atmosphere with a channel (as a window) in the karst area. There have been few reports about the role of the channel in the carbon cycle in the karst area. Previous studies have shown there is an obvious chimney effect in the karst cave system, which cannot be ignored. However, through the overview of the previous studies on carbon cycle of chimney effect in the karst cave system, we found that there were still many problems need to be further studied, such as the contribution of chimney effect to regional and global atmospheric CO₂; the regional differences, the seasonal changes and its reason (driving force) of chimney effect; the influences of chimney effect on the local ecosystem. With the development of modern science and technology (such as eddy covariance, large aperture scintillation and isotope), it becomes possible to solve the above problems. Therefore, it is necessary to use these advanced means for automatic and continuous monitoring and researching the carbon cycles in the karst cave system, which are of important significance for the researches of carbon cycles in the karst area, even for the global carbon cycle studies.  相似文献