Occurrence of nonsurface superadiabatic lapse rates within RAOB data

Abstract

As part of creating an atmospheric database for research purposes, 73 497 radiosonde observation (RAOB) soundings from 1983 through 1987 were checked for nonsurface (at least 50 mb above the surface) superadiabatic lapse rates (SLRs). About 60% of the input profiles contain a nonsurface SLR, most of which are subtle. Some of the superadiabatic reports are extreme, indicating probable RAOB error. These erroneous upper-air data are capable of corrupting derived meteorological parameters and analyses. A check for nonsurface SLRs allows these suspect data to be flagged for deletion or correction. The occurrence of superadiabatic reports is somewhat correlated with season and geographic location. However, all meteorological conditions are prone to these reports of nonsurface SLRs. A quality control criterion is developed to check for nonsurface SLRs using potential temperature, which is not overly sensitive in thin layers (as opposed to lapse rate). During RAOB ascent, any nonsurface report of a potential temperature decrease of more than 1 K is flagged for superadiabatic quality control failure. This threshold rejects the worst 4.3% of input upper-air profiles, allowing the vast majority of minor occurrences to pass. The meteorological and climatological communities should be aware of the occurrence of nonsurface SLRs within RAOB data.