Evaluation of NMC (National Meteorological Center) Global Analyses: 1979-1987

摘要

In order to make optimal use of the data set of global analyses from the U.S. National Meteorological Center (NMC), it is necessary to know of any problems that might exist and the effects of any changes in the operational system that produced the analyses. The researchers have summarized what is known about the analyses and produced under the Global Data Assimilation System (GDAS) and carried out a number of tests of their internal consistency. They have identified the missing analyses in the data and days where something clearly went wrong in the operational analysis/forecast cycle as revealed in the internal consistency checks. They recommend that such days should be omitted from all compilations of climatological statistics or in other uses of the data set such as forecasting experiments. A detailed chronology of the changes in GDAS has been compiled and they have identified the main impacts on the analyses. Discontinuities are found in certain characteristics of the analyses in most cases. These give rise to spurious trends in the data and can lead to false impressions as to what the real anomalies are. There is excessive noise in the tropics prior to May 1980 and the analyses south of 55 degree S are of very limited value for most of the record.