摘要:

A survey of the applications of satellite imagery to weather analysis and prediction in China is presented. The principal topics considered include their use in analysing and forecasting the weather systems over the Qinghai-Xizang plateau, typhoons, subtropical anticyclones and mesoscale cloud clusters. From 18 years' experience we conclude that satellite imagery is a new and useful tool for watching severe storms and studying weather systems over China.

ISSN:0143-1161    

DOI:10.1080/01431168808954842

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The number and spatial distribution of SPOT-1 HRV images acquired over northern France and southern Britain during the first commercial year of the SPOT satellite system (officially 6 May 1986–6 May 1987) have been evaluated in response to concern about the lack of cloud-free imagery. The results confirm that despite large numbers of images being acquired per scene (1 panchromatic and 12 multispectral on average over northern France; 8 panchromatic and 12 multispectral over southern Britain) most are of limited use because of cloud cover. Only 30 per cent of the images collected (or 5 images/scene/year) have at least one quadrant with <25 per cent cloud cover and 10 per cent (or 2 images/scene/year) have < 10 per cent cloud cover in each quadrant. The implications of acquiring large amounts of marginally useful data are two-fold: (1) the efficiency of the ground segment is reduced, delaying the supply of data to the user and (2) the use of HRV data for monitoring environmental change and agricultural use (for example) during the year is limited. To obtain more cloud-free data a more efficient management of the present HRV instruments must be established, and alternative strategics (for example using information from on-board forward-looking sensors or geostationary meteorological satellites) should be considered for future sensors.

ISSN:0143-1161    

DOI:10.1080/01431168808954843

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Global observations at 37 GHz frequency by the scanning multichannel microwave radiometer (SMMR) on board the Nimbus-7 satellite are related to zonal variations of land surface evaporation and primary productivity, and to temporal variation of atmospheric CO2concentration. The ground resolution of the 37 GHz data used in this study is 0·25° × 0·25° (latitude × longitude) and is composited monthly from January 1979 to December 1985. The annual actual evaporation and primary productivity data are extracted from the literature and correspond to averages for 5° latitude bands from 75° N to 55°S, while the CO2data are monthly observations at 20 globally distributed monitoring stations from August 1981 to July 1983. The satellite sensor data have been averaged for 7 years and then averaged zonally in 5° latitude bands to relate to evaporation and primary productivity, while the monthly satellite sensor data have been averaged from 75° N to 55° S to relate to the CO2data. The temporal variation of CO2concentration and the zonal variations of evaporation and primary productivity are shown to be highly correlated with the satellite sensor data. Evaporation and primary productivity for latitude bands in the Sahel zone of Africa appear anamolous when compared with the satellite sensor data, perhaps because the estimated evaporation and primary productivity values do not represent the recent drought conditions over the Sahel zone. Potential usefulness of the 37 GHz data for global biospheric and climate studies are suggested.

ISSN:0143-1161    

DOI:10.1080/01431168808954844

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The relationship between above-ground vegetation biomass (biomass) and reflectance in red (R) and near-infrared (NIR) wavelengths is well documented. In recent work it has been observed that the accuracy of biomass estimation using these relationships is higher than that based solely on traditional ground data measurement. It was posulated that the accuracy of these estimates allowed field assessment of leaf nitrogen content to be undertaken when leaf nitrogen, green reflectance and near-infrared reflectance were not strongly related because of the relationships between biomass and leaf nitrogen. This paper presents the results of a pilot study that sought to explore the links between biomass, leaf ‘kjeldahl’ nitrogen, R and NIR reflectance. It was observed that biomass was related to R and NIR reflectance and leaf kjeldahl nitrogen, but the variance in each relationship was high, despite taking into account leaf and soil moisture and site topography. It is proposed that much of the unexplained variance is due to different proportions of live, dead, erectophile and planophile biomass at each site.

ISSN:0143-1161    

DOI:10.1080/01431168808954845

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor