EFFECTS ON CLIMATE RECORDS OF CHANGES IN NATIONAL WEATHER SERVICE HUMIDITY PROCESSING PROCEDURES

The U.S. National Weather Service has recently corrected an error in r adiosonde humidity data reduction algorithms, eliminated a sonde thats processing contained another error, and recently made a further chang e in the humidity data reduction algorithm. They also introduced new p rocedures for reporting humidity from radiosondes. These changes will affect the climate records of U.S. upper-air humidity. Because the cha nges affect observations differently at different temperatures and rel ative humidities, their impact on monthly mean humidity quantities dep ends on the Frequency with which certain conditions occur. The authors calculated the effects on monthly mean humidity quantities of five sp ecific changes at a representative set of U.S. radiosonde stations. So me of these effects are quite substantial and should be considered in evaluating climate variability.