An evaluation of problems affecting the measurement of low relative humidity on the United States radiosonde

Abstract

This study examines a number of factors that can potentially affect the accuracy of NWS radiosonde low-humidity data, including 1) characteristics of the hygristor response curve, 2) characteristics of the NWS analog radiosonde and methods used to transmit and record the radiosonde signal, and 3) reduction techniques used to convert the radiosonde signal into RH. It is shown that the primary factor that biases the NWS low-humidity data, and that makes the hygristor appear to lose its sensitivity below 20% RH, is an error in the placement of the 10% and 15% RH lines on the humidity evaluator used to convert the radiosonde signal into RH. -from Author