Method of critical control of atmospheric radiosounding data in the range of extreme deviations

Abstract

The paper presents a new method of critical control of atmospheric radiosounding data in the range of extreme deviations of air temperature, isobaric level elevation, relative humidity and wind components. The method was developed based on atmospheric radiosounding data taken from 9 Ukrainian aerological stations over the period of 1973–2018. “Buoyant” threshold values form the basis of the developed method. These values correspond to the deviation threshold for each of aerological characteristics where statistical distribution of such characteristics reaches a zero value for the first time. Departure from constant threshold values in favor of “buoyant” values allowed for consideration of the main features of aerological characteristics dispersion, dependence from altitude and difference of distribution parameters observed during daylight and at night time. Potential errors in the range of extreme deviations may be identified when the values go beyond the thresholds of "the distribution body". The total percentage of such overrange amounts to 0.2% in the middle and upper troposphere, 0.3–1.8% in the lower troposphere, and up to 2% in the stratosphere. At the second stage of the developed method potential errors are checked using partial vertical, partial horizontal and temporal control techniques. The second stage of control is implemented for the levels where time series reach at least 3700 values. It allows for accurate calculation of average multi-year values required for performing the horizontal control. Potential errors are considered as real ones if there is a confirmation of existence of three extreme deviations taken from the “neighbor stations – neighbor observation periods – neighbor isobaric levels” set. It means that a potential error should be confirmed with at least two different types of critical control. At high altitudes two confirmations are enough provided a conclusion is made following the results of different types of control. The developed critical control method allowed rejection of the claim about incorrectness of 568 values with their maximum deviations reaching 6.2 and -6.4 σ for the total period of observation. The critical control of extreme deviations and the physical permissible limits control form necessary components of the complex critical control of atmospheric radiosounding data. They provide input information used for horizontal, vertical and hydrostatic control techniques.