摘要:

The status of obtaining geophysically useful observations of ice and snow through the interpretation of satellite data is discussed. Over the last decade, the examination of satellite data for information on ice and snow has developed rapidly; datasets of results have been generated; the connections between ice and snow microscopic properties and their electromagnetic behaviour are now better understood; and a good deal of accurate satellite-derived information on ice and snow can now be obtained.

ISSN:0143-1161    

DOI:10.1080/01431169208904021

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

It is shown here that clouds can be monitored over the Polar Regions with respect to their occurrence and even water phase using the multispectral data of the AVHRR onboard of NOAA satellites. Estimates of their transmittance for the total downward solar radiation appear feasible, while no method has yet been developed to estimate the downward atmospheric radiation.

ISSN:0143-1161    

DOI:10.1080/01431169208904022

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Data from meteorological satellites have been received operationally in Berlin since 1966. The position of the sea ice edge between Greenland in the west and the Kara Sea in the east is extracted from these data monthly. An overview of methods for deriving ice information from operational satellite data is given, with special attention to AVHRR data: the use of single channel and channel difference images, minimum brightness, and microwave data from the MSU onboard the NOAA satellites. On the basis of monthly ice maps the ice-covered area between 50° W and 60° E has been computed. These data can be useful for studying interannual and seasonal variations of the ice cover within this sector of the Arctic.

ISSN:0143-1161    

DOI:10.1080/01431169208904023

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Effects of wind, water vapour, and cloud liquid water on ice concentration and ice type calculated from passive microwave data are assessed through radiative transfer calculations and observations. These weather effects can cause overestimates in ice concentration and more substantial underestimates in multi-year ice percentage by decreasing polarization and by decreasing the gradient between frequencies. The effect of surface temperature and air temperature on the magnitudes of weather-related errors is small for ice concentration and substantial for multi-year ice percentage. The existing weather filter in the NASA Team Algorithm addresses only weather effects over open ocean; the additional use of local open-ocean tie points and an alternative weather correction for the marginal ice zone can further reduce errors due to weather. Ice concentrations calculated using 37 versus 18 GHz data show little difference in total ice covered area, but greater differences in intermediate concentration classes. Given the magnitude of weather-related errors in ice classification from passive microwave data, corrections for weather effects may be necessary to detect small trends in ice covered area and ice type for climate studies.

ISSN:0143-1161    

DOI:10.1080/01431169208904024

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A low-light visible/near-infra-red satellite image of the Ross Ice Shelf area at 15 10 UTC on 1 November 1986 showed a cloud-free region along the Transantarctic Mountains from the Liv Glacier northward. The corresponding thermal infra-red image indicated that the clear area was a katabatic air mass, fed by katabatic winds blowing from the main glacier valleys that dissect the Transantarctic Mountains. The cloud-free area broadened to the north and its western edge passed just to the east of Minna Bluff. The katabatic air mass crossed the edge of the Ross Ice Shelf, extended about 350 km offshore and developed cloud streets. Thus, this katabatic airstream appeared to propagate horizontally for over 1300 km. Analyses are presented of its association with the regional atmospheric circulation, of its time evolution and of its probable impact on the sea ice cover over the Ross Sea. Aspects of the governing dynamics are discussed.

ISSN:0143-1161    

DOI:10.1080/01431169208904025

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Wind and temperature are the most important factors in describing the climate on an Antarctic plateau. Japanese Antarctic Research Expeditions have conducted a series of oversnow traverses in Mizuho Plateau, East Antarctica. Data have been collected on the annual mean temperatures, which are inferred From 10 m depth snow temperatures, and on the prevailing wind directions, which are inferred from the snow surface reliefs. The data from the ground-based observations have been combined with remotely sensed data both from satellites and airplanes. Annually averaged NOAA channel 5 brightness temperatures correlate well with the 10 m snow temperatures. The synthesized prevailing windfield shows a clear distinction between the katabatic wind system and that of the synoptic disturbances. Confluence zones are also identified but their presence seems only intermittent. A slight but significant climate difference has been observed between ridges and troughs of the plateau due to the difference in katabatic wind forces.

ISSN:0143-1161    

DOI:10.1080/01431169208904026

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

An atmospheric transmittance model has been applied to Antarctic radiosonde ascents in order to examine the high-latitude normalized weighting functions (NWF) of the water vapour channels on the High Resolution Infrared Radiation Sounder (HIRS). In the Antarctic coastal region the 6·7 μ radiances are shown to be largely atmospheric in origin and imagery created from these data can provide useful diagnostic information on tropospheric water vapour, even during the winter months. The 7·3μm data contain a large surface contribution and have less value as a diagnostic tool. An example is shown of HIRS water vapour imagery of the Antarctic at a time when a cold front was descending from the Antarctic Plateau to the coastal area. The imagery clearly showed the dry air behind the front and provided information that was not available with any other imagery channel. A second example of a North Atlantic polar low shows the contaminating effect of cloud when deep atmospheric systems are being examined.

ISSN:0143-1161    

DOI:10.1080/01431169208904027

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A pattern recognition algorithm is demonstrated which classifies eighteen surface and cloud types in high-latitude AVHRR imagery based on several spectral and textural features, then estimates the cloud properties (fractional coverage, albedo, and brightness temperature) using a hybrid histogram and spatial coherence technique. The summertime version of the algorithm uses both visible and infrared data (AVHRR channels 1—4), while the wintertime version uses only infrared data (AVHRR channels 3-5). Three days of low-resolution AVHRR imagery from the Arctic and Antarctic during January and July 1984 were analysed for cloud type and fractional coverage. The analysis showed significant amounts of high cloudiness in the Arctic during one day in winter. The Antarctic summer scene was characterized by heavy cloud cover in the southern ocean and relatively clear conditions in the continental interior. A large region of extremely low brightness temperatures in East Antarctica during winter suggests the presence of polar stratospheric cloud.

ISSN:0143-1161    

DOI:10.1080/01431169208904028

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Cloud distributions were analysed from the AVHRR data of the NOAA satellite received at Syowa Station (69°S, 39°35' E) in Antarctica. Algorithms to derive cloud amount using the brightness temperature difference of infrared channels 3 and 4, or 4 and 5, were assessed by comparing the satellite cloud amount to the manual cloud amount and the downward longwave radiation at the ground surface. Cloud amounts obtained by the brightness temperature difference of channels 3 and 4 in summer agreed with the manual cloud amounts at the surface, and was highly correlated to the downward longwave fluxes. Cloud amounts from channels 4 and 5 showed a rough agreement with the surface cloud amounts. Distributions of cloud derived from the pilot datasets were examined.

ISSN:0143-1161    

DOI:10.1080/01431169208904029

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Global observations from the satellites of the TIROS-N/NOAA series over polar regions, where thein situmeasurements are scarce, constitute a valuable help for the study of mesoscale meteorological phenomena after interpretation of these observations into atmospheric and surface parameters. The 31 (Improved Initialization Inversion) system, which relies on a pattern-recognition-type approach, has been applied to NOAA-9 and NO A A-10 passes of both hemispheres and at different periods of the year. Results show that the 31 method is able to identify cyclonic conditions. Comparisons between retrieved products and conventional products show a good agreement. The first assimilation experiments of 31 temperature profiles into a fine mesh model seem promising.

ISSN:0143-1161    

DOI:10.1080/01431169208904030

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor