摘要:

The attenuation of radio waves due to rain can be predicted with a good degree of accuracy, provided the rain rate characteristics over the entire path of propagation are known. The attenuation due to rain is usually deduced on the basis of point rain rate, which can lead to inaccuracy in the estimation of attenuation. We use the concept of rate of decay of rain path profile to estimate the attenuation due to rain. The attenuation has been deduced at 11GHz and 13.4 GHz for 56 elevation angle by using the theory of decay rate of rain path profile, its controlling factor, gamma, and rain rate distribution over Delhi, a tropical station in India. The theoretically-estimated attenuation is compared with observed values, as well as with values obtained using the International Radio Consultative Committee (CCIR) method. The CCIR model is found to overestimate the attenuation.

ISSN:0143-1161    

DOI:10.1080/014311697216865

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Infrared images obtained from instruments on environmental satellites have revealed long straight lines across the Nullarbor Plain in southern Australia. These features, which are up to 400km long and 10 to 20km wide, are not normally visible in satellite sensor imagery, but were observed for several days in October 1992. Subsequent investigations have shown the tracks to be caused by increased soil moisture following the passage of localised storms across the area.

ISSN:0143-1161    

DOI:10.1080/014311697216874

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Remotely sensed measurements at optical wavelengths may provide information on crop water status and increase the accuracy of crop production forecasts. Previous research has shown that canopy spectral response to water stress is attributable to change in leaf water content, canopy structure and soil moisture. This experiment was designed to study leaf spectral response resulting from changes in leaf water content and to evaluate the use of a radiative transfer model for predicting the spectral behaviour of the leaf. The difference between measured and modelled reflectance increased as leaf water content decreased and it was hypothesized that this may be due to a change in leaf internal structure that was unaccounted for by the model.

ISSN:0143-1161    

DOI:10.1080/014311697216883

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor