National Oceanic and
Atmospheric Administration
United States Department of Commerce


 

FY 1983

Data Intercomparison Theory—Vol. V, Case study: Effects of objective analysis on a tropical Pacific sea surface temperature set

Preisendorfer, R.W., and C.D. Mobley

NOAA Tech. Memo ERL PMEL-42, NTIS: PB83-182345, 79 pp (1982)


A study is made of an objective analysis scheme by Liu which has SST-gradient-dependent smoothing and correction operations, along with data-weight and outlier cutoff features. The scheme is an elaboration of that originally devised by Cressman and subsequently expanded by Levitus and Oort. The object of the study is to apply certain new data intercomparison techniques (developed in the four earlier works of the present series) to the data set produced by Liu's scheme, with the goal in mind to determine how the various features of the new objective analysis scheme change the location (average), scale (variance), and pattern properties of the data set. In general it is found that the average properties of a data set are largely unchanged by application of the above features of Liu's scheme. However, the variance and pattern properties are significantly changed by the various smoothing operations in Cressman-type objective analysis schemes. In the case of Liu's data set the changes are by amounts (0.5°C) that are climatologically important. Thus a new objective analysis scheme may significantly affect location, scale and pattern properties of a data set, and therefore in ways that could affect the formation and verification of hypotheses of climatic change.




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