CONSISTENCY CHECK FOR TRENDS IN SURFACE-TEMPERATURE AND UPPER-LEVEL CIRCULATION - 1950-1992

A time series of 43 years of observed monthly mean air temperature at 109 sites in the 48 contiguous United States is compared to monthly me an air temperature specified from hemispheric gridded 700-mb heights. Because both upper-air and surface data have problems that may limit t heir use in climate change studies, this comparison could be considere d a mutual consistency check. Cooling (by about 0.5 degrees C) from 19 51 to about 1970 and subsequent warming (also by 0.5 degrees C) that c ontinues through the present are found in both datasets, indicating th at these interdecadal changes are probably real. In the last several y ears the specified temperatures were often colder than those observed. This prompted an investigation of whether the ''residual'' (specified minus observed) has recently been large (and negative) compared to th e earlier part of the record. It was found that for the same 700-mb he ight field, surface temperatures were almost a degree Celsius warmer i n the last few years than they were in the early 1950s, but considerin g the variability of the residuals over the 1950-92 period, the recent cold residuals may not yet be strikingly unusual. By comparing the fu ll set of 109 stations to a ''clean'' subset of 24, the impact of comm on problems in surface data (station relocation, urbanization, etc.) w as found to be quite small. The rather favorable comparison of observe d surface temperatures and specified surface temperatures (which suffe r from upper-air analysis/observation changes over the years) indicate s that their respective data problems do not appear to invalidate thei r use in studies of interdecadal temperature change.