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1988 .

(3 publications)

Z. X. Li. A homogeneous z-term series of astrometric latitude observations (January 5, 1962-December 31, 1981). , 75:151-156, October 1988. [ bib | ADS link ]

Optical astrometric data for 1962-1982 has been reduced in order to redetermine the earth rotation parameters. A homogeneous series of z-terms of latitude observations has also been obtained. A total of 1461 z-terms at five-day intervals in the 20 years are given in this paper. The typical precisions of the z-terms are of the order of + or - 0.014 arcsec for the first five years and from + or - 0.008 arecsec to + or - 0.005 arcsec for the following years.

N. Capitaine, Z. X. Li, and S. Z. Nie. Determination of the principal term of nutation from improved BIH astrometric data. Astronomy Astrophysics, 202:306-308, August 1988. [ bib | ADS link ]

New series of the common latitude term z as obtained by Li (1985) from an improved reduction, referred to the IAU - 1976 System of Astronomical Constants and to the IAU - 1980 theory of nutation, of the BIH astrometric data at five-day intervals from 1962 to 1982 are used for deriving the coefficients of the principal term of nutation. The derived coefficients are in good agreement with similar previous astrometric determinations (Feissel and Guinot, 1981; Capitaine and Xiao, 1982) with improved formal errors, which are, in the present work, of the order of 0arcsec.001.

H. Le Treut and Z.-X. Li. Using meteosat data to validate a prognostic cloud generation scheme. Atmospheric Research, 21:273-292, 1988. [ bib | DOI | ADS link ]

We have designed a cloud generation scheme for use in the LMD GCM. It predicts the mixing ratio of the cloud's condensed water as a new prognostic variable. At present it does not fully interact with the radiation schemes, but the aim is to predict the cloud optical properties. We have used the Meteosat/ISCCP data to evaluate this scheme. Such a comparison allows us to place some constraints on the coefficients which are used in the parameterizations, such as the precipitation thresholds for the cloud's liquid water content and the relative variability of water vapour within a grid box. There is generally a good agreement between observed and simulated results, although there appear some discrepancies in the cloud's apparent temperatures.

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