ISSN:0143-1161    

DOI:10.1080/014311698213920

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Images of atmospheric column water vapour derived from backscattered solar radiation measured by the biospectroradiometer B of the Modular Optoelectronic Scanner (MOS) are introduced. The method for derivation is based upon the technique of the Continuum Interpolated Band Radio (CIBR) for the 940 nm absorption band. A correction algorithm for the underestimation of the water vapour content due to low reflecting surface cover was applied. The instrument measures radiation in the 400-1010 nm region in 13 channels of 10 nm bandwidth and has a ground IFOV of 520 m x 520 m. The retrieved water vapour values were compared to radiosonde data. The derived equations are applicable over cloud-free land surfaces (separated in nonvegetation and vegetation cover) of the midlatitude regions with only small elevations (e.g., agricultural areas).

ISSN:0143-1161    

DOI:10.1080/014311698213939

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Since March 1996 the Modular Optoelectronic Scanner (MOS) of the German Aerospace Research Establishment (DLR) has provided spectral radiance data of the atmosphere-surface system in 18 spectral channels and up to 420 pixels in a 200 km swath from a 817 km sun synchronous polar orbit. The MOS consists of two imaging spectrometers, MOS-A (four channels with a halfwidth Delta lambda 1.4 nm in the O2 A absorption band) and MOS-B (13 channels between 400 and 1010 nm with Delta lambda 10 nm), and a camera, MOS-C, at 1.6 mu m. Beside the onground laboratory calibration as the basis for calculation of the spectral radiance data, a mission of such long duration requires a periodic recalibration or at least a stability check of instrument properties in orbit to support the reliability of the remote data. In this paper the two in-flight calibration methods will be described and their capabilities will be demonstrated on the basis of the real data during MOS's first year in orbit: the relative checking of the instrument parameters with internal lamps and the absolute calibration with the extraterrestrial sun radiation.

ISSN:0143-1161    

DOI:10.1080/014311698213948

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Image processing techniques have been utilized for enhanced visual displays of cloud imagery for clouds over the Indian subcontinent during July, month of the summer monsoon. Indian Satellite (INSAT-1D) bi-channel (infrared and visible band) data were used for contrast manipulation and false colour composite (FCC) production. Two combinations of the infrared and visible bands were used to form the third band required for the FCC method. It is shown here that for the third band, a new combination (IR2/VIS) is better than a previously suggested combination (2VIS-IR) for identifying clouds of different optical thickness during the monsoon season. Various colour combinations have also been studied experimentally in order to produce efficient displays of clouds which conform to common perceptions of their natural colour.

ISSN:0143-1161    

DOI:10.1080/014311698213957

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Significant contributions to studies in aerosol science have come from optical remote sensing techniques and, for several reasons, these studies have special importance over the tropics where convective and high-altitude convective (as well as dynamical) processes affect the distribution of aerosols. Atmospheric aerosol studies employing active remote sensing techniques such as light detection and ranging (lidar) have been in progress for the past decade at the Indian Institute of Tropical Meteorology (IITM), Pune (18 32' N, 73 51' E, 559 m above mean sea level), India. Simultaneous measurements of aerosol optical and physical properties using passive remote sensing techniques such as spectroradiometry have also been in practice at the IITM since 1992. The experimental techniques developed and the results of the studies that have been carried out at the IITM are reviewed in this paper. These observations have enabled the study of aerosol climatology over Pune and have led to a better description of the atmospheric aerosol structure and stratification in the nocturnal atmospheric boundary layer, the air quality, and their association with the experimental terrain and meteorological conditions of the observing station. Such tropospheric aerosol climatologies are sparse over the tropics and almost nonexistent in India. The stratospheric physical and dynamical aerosol aspects of recent major volcanic eruptions, studied from ground-based lidar and satellite observations, are also discussed.

ISSN:0143-1161    

DOI:10.1080/014311698213966

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Urban air pollution can be quantified in terms of atmospheric turbidity if satellite images of similar geometry acquired under clear atmosphere and pollution conditions are radiometrically compared. This comparison can be conveniently carried out by evaluating 'the apparent contrast reduction' due to aerosols over land. However, this method is subject to misclassification due to ground-reflectance temporal variations. This paper proposes the complementary application of 'the temperature attenuation' procedure, which allows one to decouple the results of the previous method from such variations and, thus, increase confidence in classification results. The respective image processing code developed has been tested successfully on Landsat-5/TM data of the urban area of Athens.

ISSN:0143-1161    

DOI:10.1080/014311698213975

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Daily ozone measurements from satellite sensor data (Total Ozone Mapping Spectrometer TOMS) over Dundee, Scotland (56.5 N, 3 W) during 1986-1992 with daily broad-band measurements of solar ultraviolet (UV) radiation reaching the ground deduced from ground-based instrumentation were used to investigate their correlation. The erythemally active UV radiation showed an increase of 35% during 1986-1992 while the total ozone amount showed a decrease of 10% during the same period. Furthermore, the ratio of the increase of UV radiation to the decrease in ozone concentration was maximum in July, showing that a small percentage decrease in total ozone during summer leads to a large percentage increase in solar UV radiation reaching the ground.

ISSN:0143-1161    

DOI:10.1080/014311698213984

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Dobson spectrophotometer measurements are known to be subject to stray light errors. To study these errors with Dobson spectrophotometer no. 188 in Athens, Greece, a series of total ozone measurements were taken out to high airmasses extending as far as mu = 3.0. The results were compared to the simple monochromatic-heterochromatic stray light model introduced by Basher. These comparisons showed that the instrument's Ro value was between 10-3.5 and 10-3.4. These Ro values indicate that the instrument does not introduce any stray light interference for the regular observations performed at Athens. The value of the other parameter, a, of the Basher model varied between 0.6 and 0.9, having a weak dependence on the total ozone amount.

ISSN:0143-1161    

DOI:10.1080/014311698213993

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The reprocessed (version 7) daily total ozone observations made by the Total Ozone Mapping Spectrometer (TOMS) on the Nimbus-7 satellite over Athens (37.6 N, 23.4 E) for the period from November 1978 until April 1993 have been used to investigate total ozone depletion. To estimate the trends in total ozone content a linear fitting to the data has been applied, given that the other components like the quasi-biennial oscillation, the El Nino/Southern Oscillation and the solar cycle have a very small contribution to the total ozone depletion effects over that geographical region. The total ozone depletion over the 15-year period was derived from version 7 shows a strong seasonal variation from more than 6% in winter and early spring to about 1.5% in summer. The total ozone depletion over Greece is found to be about 1% (per decade) less using version 7 than using version 6.

ISSN:0143-1161    

DOI:10.1080/014311698214000

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

An intercomparison of total ozone observations made with Solar Backscatter Ultraviolet (SBUV) experiment, the Total Ozone Mapping Spectrometer (TOMS), flown on the Nimbus-7 satellite, and the Dobson spectrophotometer installed at Athens, Greece, is presented in order to examine their precision and accuracy. The results show that there is a very good agreement between the compared datasets corresponding to a regression line coefficient interval of 0.932-0.934.

ISSN:0143-1161    

DOI:10.1080/014311698214019

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor