COMPARISON OF NMCS GLOBAL PRESSURE ANALYSIS TO NCDCS US OBSERVATIONS

The National Meteorological Center's (NMC's) twice-daily, global 2.5 d egrees pressure analyses of temperature, relative humidity, and wind s peed are compared, over the coterminous United States, to the National Climatic Data Center's twice-daily, upper-air rawinsonde observations and hourly, first-order, surface observations for the period 1 Januar y 1988 through 31 December 1992. NMC's analyses have clearly improved during this time period. Still, there are some noticeable differences, especially near the surface and at 1200 UTC. During the early morning there is a warm bias, relative humidity is too low, and the surface w ind speed is too strong. Weaker systematic errors occur during the lat e afternoon: there is a cold bias, relative humidity is too high, and the surface wind speed is still too strong. Aloft, the bias is noticea bly reduced except for the wind speed, which is somewhat too weak. The analysis wind speed also has too strong temporal variations near the surface and too weak temporal variations aloft. The analysis climatolo gy can be corrected at each station by removing the bias. Transient va riations can be corrected simply by multiplying the analysis anomalies by the ratio of the station standard deviation to the analysis standa rd deviation. Correcting for the biases and variances and spatially in terpolating the analysis and station corrections to a 0.5 degrees grid provides a useful guess for local conditions, especially if there is not a surface or rawinsonde station within about 200 km.