ISSN:0143-1161    

DOI:10.1080/01431169008954995

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0143-1161    

DOI:10.1080/01431169008954996

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Observations of ocean features and their interaction near Pt Conception, California, are reported for a two-month period during the early spring of 1983 at the time of the El Nino. The development of a body of warm water into a clockwise rotating eddy is described and the observed increase in the spatial scale of the eddy is found to compare favourably with the value calculated rrom a model of geostrophic adjustment. The subsequent interaction of the warm core eddy with a cold coastal jet directed offshore is discussed in relation to the approximate one-month lifetime observed for the eddy. The interaction of the eddy with incoming swell, and the resulting gradients in wave energy and wind stress are discussed in an accompanying paper in this issue (Sheres and Kenyon 1989). The measurements in this report are based mainly on NOAA-7 infrared images, but in situ current and wind data from moorings and temperature and salinity data from a California Cooperative Fisheries Investigation (CALCOFI) cruise are used as well. Water velocities up to 55cm/s (averaged over 12-24 hours) were calculated from tracing temperature features in successive infrared images; they compare well with CALCOFI and moored near-surface current data, when available.

ISSN:0143-1161    

DOI:10.1080/01431169008954997

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The interaction between an ocean eddy and incoming swell is investigated numerically producing characteristic refraction patterns of wave number and energy. The velocity distribution in the model eddy follows observations off Pt. Conception that are discussed in Sheres and Kenyon in this issue. The energy refraction patterns exhibit focus regions (caustics) where wave energy is concentrated; adjacent regions have a reduced wave energy concentration. Due to the eddy-induced refraction of incoming Pacific swell frequently observed in the area, approximately 20 km of coastline near Pt. Conception and about 5 km of coastline south of Morro Bay (California) would have relatively high waves. The Santa Maria Basin in between, as well as part of the entrance to the Santa Barbara Channel, would have relatively low waves. These gradients of wave energy depend on the velocity distribution of the eddy and the group velocity of the waves. Change in both the velocities while maintaining their ratio constant produces the same refraction patterns in the limited number of cases that were tested. During the 30 days residency of the eddy off Pt. Conception, the gradients of wave energy were likely to be significant. The potential effect of such gradients on the momentum exchange between wind and water (wind stress) and between waves and surface flow are discussed briefly.

ISSN:0143-1161    

DOI:10.1080/01431169008954998

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The Arabian Sea circulation is unique among the world ocean circulations in that the winds over it reverse semiannually from northeasterly to southwesterly. Complex patterns of eddies and strong temperature gradients are two aspects of its response linked to the monsoonal reversal. In this paper very high resolution radiometer (VHRR) digital data from INSAT-1B was processed and enhanced to observe the sea surface features and to locate a mesoscale eddy in the Somali region. The dimensions of the eddy and the horizontal movement are within the expected range of past observations and the model simulations.

ISSN:0143-1161    

DOI:10.1080/01431169008954999

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A method for retrieving broad band surface albedo from top of atmosphere reflected solar radiances measured by the visible and near-infrared channels of the Advanced Very High Resolution Radiometer (AVHRR) is described. The algorithm developed was applied to eight passes over the British Isles and near continent for relatively cloud-free conditions between the months of April and October. The retrieved surface albedos are presented both as high resolution images to show up the detail in the spatial variability and as tables where each value is an average over a 15 km grid square. The surface albedos of the agricultural areas of the British Isles showed a marked increase from 17 to 22 per cent between April and July. In contrast urban areas and rougher hilly terrain (e.g. the Scottish Highlands) gave lower surface albedos of ∼er cent which remained more constant throughout the period between April and October. The results presented here are compared with those derived by other workers and found to be consistent with them, bearing in mind the uncertainty of the method presented here which is about 4 per cent in reflectance.

ISSN:0143-1161    

DOI:10.1080/01431169008955000

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

L' étude concerne I' évaluation des performances du Thematic Mapper de Landsat applique à la cartographie de I'occupation du sol en milieu méditer-raneen. Dans un premier temps, on a cherché à sélectionner, parmi les 6 canaux TM, quels sont les plus performants. Apres une classification non supervisée des données multispectrales (Analyse Factorielle des Correspondances, Classification Ascendante Hierarchique, Agrégation autour des Centres Mobiles), les bandes TM3, TM4 et TM5 apparaissent corhme les plus performantes. Des classifications supervisees pratiquees sur ces trois canaux, il ressort des performances tres variables fortement liees au degre d'heterogeneite des cibles choisies au sol.

ISSN:0143-1161    

DOI:10.1080/01431169008955001

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The relationship between the leaf area index (LAI) of temperate coniferous forests in the western United States and Thematic Mapper (TM) data corrected for atmospheric effects and Sun-surface-sensor geometry was influenced by canopy closure, understory vegetation and background reflectance. Strong inverse curvilinear relationships were observed between coniferous forest LAI and both TM bands 3 (0-63-0-69μm) and 5 (1-55-1-75μm). The inverse relationships are explained by increased reflectance of understory vegetation and background in open stands of lower LAI and decreased reflectance of the overstory in closed canopy stands with higher LAI. A strong positive relationship was observed between LAI and TM band 4 (0-76-0-90μm) radiance in stands with greater than 89 per cent canopy closure. Open stands with low overstory LAI had elevated band 4 radiances caused by understory vegetation and/or a highly reflective granite background. Old growth stands with incomplete overstories had low band 4 radiances as a result of less reflective forest litter and shadows. A ratio of band 4/band 3 compensated for the elevated band 4 radiance in open stands with vegetated or highly reflective backgrounds, but did not compensate for the low band 4 radiance in old growth stands with less reflective backgrounds of forest litter and shadows. Analysis of atmospheric and Sun-surface-sensor geometry corrections applied to the TM data indicated that path radiance contributed approximately 50 per cent of the radiance in TM band 3,20 per cent in band 4, and less than 10 per cent in band 5.

ISSN:0143-1161    

DOI:10.1080/01431169008955002

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Simulations of the bidirectional reflectance distribution functions at the top of the atmosphere (TOA) over land surfaces were performed and compared with observations derived from NIMBUS-7. The two methods produce similar patterns even though the model computations were performed under the assumptions of a Lambertian surface. These results raise a question regarding the need to account for surface anisotropy in simulations intended for the interpretation of low-resolution satellite observations.

ISSN:0143-1161    

DOI:10.1080/01431169008955003

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

An attempt to derive downward longwave radiation at the surface in clear sky conditions is presented. A method that integrates satellite-measured infrared radiation temperatures with ground measurements of water vapour pressure is applied to Meteosat data. Satellite-derived fluxes are compared with corresponding ground-measured fluxes at three different sites in France and during various seasons. Comparison of the daily averaged fluxes shows a correlation coefficient of 0–88 and an r.m.s. difference between satellite estimates and ground measurements of 12 Wm-2.

ISSN:0143-1161    

DOI:10.1080/01431169008955004

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor