ISSN:0143-1161    

DOI:10.1080/01431169108955278

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Agricultural applications using surface temperatures obtained from NOAA AVHRR thermal infrared data involve the difficulty of obtaining the actual surface temperature of the crop, due to the atmospheric and crop's emissivity effects. The split-window method is often used to correct atmospheric effects, but generally is valid only for sea surface temperature. Two original methods to obtain the split-window equation are presented: the first one uses ground measurements, the second one uses atmospheric information contained in NOAA data itself (i.e. the difference between brightness temperatures of AVHRR's bands 4 and 5). Both lead to a mean error of 2 deg K on the equivalent black body temperature. An original method to obtain directly from NOAA data the difference between emissivities of the surface in bands 4 and 5 is presented. The error on the actual surface temperature obtained is I deg K. for an error of 1 per cent on the mean emissivity. Finally the surface temperature can be estimated from NOAA data with an error of 3 deg K.

ISSN:0143-1161    

DOI:10.1080/01431169108955279

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In this paper a methodology for obtaining the crop temperature from NOAA-9 AVHRR data has been developed, which is based on a theoretical model that permits interpreting the remote sensing temperature measurement in heterogeneous and rough surfaces. This procedure determines the crop temperature by evaluating prsviously: (1) the temperature difference between crop and ground, (2) the atmospheric and emissivity corrections, (3) the ground and vegetation emissi-vities in the AVHRR bands 4 (10-3-11-3 μm) and 5 (11 -5-12-5 μm), and (4) the proportion of ground in each pixel. We have applied this method to obtain a map of orange-tree temperatures for the Valencian region and satisfactory results have been obtained.

ISSN:0143-1161    

DOI:10.1080/01431169108955280

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Wheat plays an important role in the Brazilian commodity production. Therefore, objective and reliable methods for yield estimation are needed particularly at the farm level where several management actions have to be taken. TM Landsat and agrometeorological data were integrated in a model for wheat yield estimation at the farm level for a test site in the south of Sao Paulo State. Landsat data for the crop years of 1986 (three acquisitions) and 1987 (two acquisitions), agronomic and meteorological data were related to yield estimates at the field level (250 fields approximately). Results have shown that the vegetation index derived from TM Landsat explained 60 and 40 per cent of wheat yield variability for the two crop years analysed. The joint use of both vegetation index and agrometeorological data in a single model improved significantly the results as compared to either vegetation index or agrometeorological data separately. The proposed model is to be validated for future crop seasons. Nevertheless, it provided objecctive and reasonably accurate results for wheat estimation on the two crop seasons analysed (R2= 0.65 with a standard error of 339 Kg/ha).

ISSN:0143-1161    

DOI:10.1080/01431169108955281

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Three bands of multispectral video imagery (0.543-0.552μm, 0.644-0.656μm, 0.815-0.827μm) were acquired from nine lakes in Vigo County, Indiana on l8 May 1988 using a multispectral video system. Eleven different scenes covering the nine lakes were digitized and used in computer-assisted analysis of secchi transparency. Individual band data and a yellow-green/red ratio band were correlated with secchi disc measurements taken concurrently with aerial video acquisition. The significant correlations (0.05 level) between the video data and secchi disc depths, were —0.83 and —0.91 for the red band (original and log) and 0.93 and 0.84 for the yellow-green/red ratio (original and log).

ISSN:0143-1161    

DOI:10.1080/01431169108955282

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The Scanning Multichannel Microwave Radiometer (SMMR) aboard the Seasat satellite measured emitted radiation in both horizontal and vertical polarizations at microwave frequencies of 6.6, 1069, 18.0, 21.0 and 37.0 GHz. Retrieval algorithms, for sea surface temperature (SST) determination, from subsets of one to three SMMR channels, are obtained by a two-step statistical technique. The technique first selects the best subsets of a given size defined by an R2 criterion (coefficient of determination), of a given size by the application of an efficient leaps and bounds technique on a statistical data base. It then performs a regression analysis on the selected subsets. The statistical data base employed a large (600) set of seasonally and geographically diverse atmospheric and surface parameters for radiative transfer calculations. The results of the study of one to three-channel subset retrieval algorithms indicate the possibility of using 6.6 V, 6.6 H and 18 V channels for SST determinatidn from Seasat-SMMR data. A comparison of SMMR-SST derived from three channels mentioned above and expendable bathythermograph (XBT) measurements over the North Pacific provided an r.m.s. difference of ∼ 1.4 K which is comparable to the accuracy obtained from a five-channel subset (6 6 V, 6-6 H, 10-69 H, 180V, 21 OH) retrieval algorithm. The retrieval technique has the ability to recognize severe noise in brightness temperature measurements which may lead to unacceptable parameter retrieval. This may be achieved by setting up a quality control criteria either using different subsets of the same size or of different sizes. The three-channel retrieval compares within ∼ 1.2 K with Chester's algorithm, which is being used at the Jet Propulsion Laboratory for geophysical processing.

ISSN:0143-1161    

DOI:10.1080/01431169108955283

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

By using the match-up data sets of Advanced Very High Resolution Radiometer (AYHRR) brightness temperatures of NOAA-9 and buoy sea surface temperatures in Mutsu Bay in northern Japan, the accuracy of the five split-window functions derived from the regional data sets and the fourteen published SWFs were evaluated. The match-ups were carefuly screened from the HRPT scenes of all seasons in 1985-1988. The temporal and the spatial coincidences are within 30 minutes and one pixel resolution, respectively.

ISSN:0143-1161    

DOI:10.1080/01431169108955284

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The determination of both the normal and tangential components of the total velocity is important in the study of cross- and along-isopycnal transport processes in the ocean. A pattern-matching method is used to determine objectively the total velocity. Sensitivity of this method to pattern and search tile sizes and to correlation threshold also is examined. Three methods for estimating the cross-isopycnal or normal component of the total flow are compared and discussed: Marr-Ullman, optical flow and minimum norm. It is also shown that optical flow and minimum norm are equivalent when the parameter a in the optical flow formulation is set to zero. The direct computation of the tangential component is not possible because it lies in the null-space of the solution set of the basic constraint equations used in velocity estimation methods which are based on the rate of change of image brightness (or temperature). A new method for indirectly estimating the tangential component of the total flow based on vector subtracting of the total flow and the normal component of flow is introduced. Several sequences of satellite images are analysed and the resulting total flow, normal component of flow, and the tangential component determined using this new method are consistent with motion inferred from edge maps. Recommendations are then made for the best normal component of flow to use in the determination of the tangential component.

ISSN:0143-1161    

DOI:10.1080/01431169108955285

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Using satellite data only, a unique model of the upper-ocean mixed-layer has been developed recently by Yan for calculating the thermal inertia (or the heat flux change per unit temperature change per day) of the mixed-layer from which daily mean mixed-layer depth is estimated. Thus digital maps of the oceanic daily mixed-layer depth in the vicinity of the Sargasso Sea for 14 May-30 August, 1982 have been generated from visible, near-infrared, thermal-infrared and microwave observations made by radiometers on board the NOAA-7, -8, GOES and Nimbus-7 satellites. The errors incurred in producing such maps are of two general type: measurement from satellites and model simplification. The sensitivity of the modelled mixed-layer depth to simplifications in the model (modelling errors) and to errors in data used for forcing the model (data errors) is considered here. To emph isize the oceanographic relevance of these errors, we express the errors in mixed-layer depth as a function of model errors and data errors, and compare these errors with the daily mixed-layer depth changes of in situ data. We also discuss some of the error sources in this paper. Thus the applications and practical limitations of the model are evaluated. The results of this study show that errors in the surface temperature field cause the largest errors in the predicted mixed-layer depth, because the surface temperature errors affect both the heat flux estimation and the thermal inertia estimation. The errors in wind speed field are less severe although these errors may become more significant at wind speed higher than 8.5 ms−1, below which most of our field comparisons were made. The smallest uncertainty is found to occur with remotely estimated changes in sea-surface albedo as this error in a very small way affects the heat flux. These results imply that the errors due to direct atmospheric radiative effects or those which determine radiative fluxes and the determination of sea surface temperature should be reduced to improve prediction of mixed-layer thermal inertia and mixed-layer depth in summer using satellite data.

ISSN:0143-1161    

DOI:10.1080/01431169108955286

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The study presented here examined the tectonically active Mendha River basin, Rajasthan, India. Landsat TM data in bands 2, 3 and 4 were used in this study. The neotectonic features were extracted through the digital analysis of the principal component (PC) and directional filtered images. However, the regional view of the study area was examined through the false colour composite (FCC). A map of the neotectonic features was generated by incorporating the limited field observations and this yielded the extensions of the neotectonic features.

ISSN:0143-1161    

DOI:10.1080/01431169108955287

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor