R. M. Goody

Why monitor the climate

Abstract A successful global climate monitoring system must fulfill clear societal objectives. For some aspects of climate monitoring, the societal goals are understood and are clearly stated, but long-term, decadal/centennial climate predictions have, in the past, been judged more in terms of curiosity-led criteria. A curiosity-led climate programis not, however, the effective way to achieve the required societal objective, which is to produce thebest possible long-term climate projections. In terms of the universal use of numerical models for climateprojections, this leads to the need for monitoring programs that provide data to test model output against reliable observations. This requires an operational climate model (which the United States does not now have), and observationsthat emphasize accurate and reproducible data designed to provide critical tests of model output. The priorities for specific monitoring programs can be formulated in terms of these requirements, which can also provide metrics o...

Analysis of Sampling Errors for Climate Monitoring Satellites

Abstract Sampling retrievals of high-accuracy first-moment statistics constitute a central concern for climate research. Considered here is the important case of brightness temperature retrievals from a selection of possible orbits. Three-hourly global satellite brightness temperature data are used to predict the sampling error of monthly to annual mean brightness temperature retrieved by one or more satellites in low earth orbits. A true polar orbit is found to offer substantial advantages over a sun-synchronous orbit in the retrieval of annual mean brightness temperature, since the rotation of the local time of observation through two full diurnal cycles greatly reduces the error due to imperfect sampling of diurnal variations. Thus, a single polar orbiting satellite can produce annual mean, zonal mean brightness temperatures with typical sampling errors of less than 0.1 K, while even three sun-synchronous orbiters have high-latitude errors of up to 0.4 K. The error in retrievals of the annual mean diur...