Time-to-detect trends in precipitable water vapor with varying measurement error

This study determined the theoretical time-to-detect (TTD) global climate model (GCM) precipitable water vapor (PWV) 100-yr trends when realisticmeasurement errors are considered.Global trends ranged from 0.055 to 0.072mmyr^-1 and varied minimally from season to season. Global TTDs with a 0% measurement error ranged from3.0 to 4.8 yr,while a 5%measurement error increased the TTDby almost 6 times, ranging from17.6 to 22.0 yr. Zonal trends were highest near the equator however, zonal TTDs were nearly independent of latitude when 5% measurement error was included. Zonal TTDs are significantly reduced when the trends are analyzed by season.Regional trends (15° × 30°) show TTDs close to those in the 158 latitude zones (15° × 360°). Detailed case study analysis of four selected regions with high population density-eastern United States, Europe, China, and India-indicated that trend analysis on regional spatial scales may provide the most timely information regarding highly populated regions when comparing detection time scales to global and zonal analyses.