Earth System Science Data | 2019
Completeness of radiosonde humidity observations based on the Integrated Global Radiosonde Archive
Abstract
Abstract. Radiosonde measurements\nfrom the 1930s to present give unique information on the distribution and\nvariability of water vapor in the troposphere. The sounding data from the\nIntegrated Global Radiosonde Archive (IGRA) Version\xa02 are examined here until\nthe end of 2016, aiming to describe the completeness of humidity observations\n(simultaneous measurements of pressure, temperature, and humidity) in\ndifferent times and locations. Upon finding the stations with a\nnon-negligible number of radiosonde observations in their period of record,\nthus removing pilot-balloon stations from IGRA, the selected set (designated\nIGRA-RS) comprises 1723\xa0stations, including 1300\xa0WMO stations, of which 178\nbelong to the current GCOS Upper-Air Network (GUAN) and 16 to the GCOS\nReference Upper-Air Network (GRUAN). Completeness of humidity observations\nfor a radiosonde station and a full year is herein defined by five basic\nparameters: number of humidity soundings, fraction of days with humidity\ndata, average vertical resolution, average atmospheric pressure and altitude\nat the highest measuring level, and maximum number of consecutive days\nwithout data. The observations eligible for calculating precipitable water\nvapor – i.e., having adequate vertical sampling between the surface and\n500\u2009hPa – are particularly studied. The present study presents the global\ncoverage of humidity data and an overall picture of the temporal and vertical\ncompleteness parameters over time. This overview indicates that the number of\nradiosonde stations potentially useful for climate studies involving humidity\ndepends not only on their record length, but also on the continuity,\nregularity, and vertical sampling of the humidity time series. Additionally,\na dataset based on IGRA is described with the purpose of helping climate and\nenvironmental scientists to select radiosonde data according to various\ncompleteness criteria – even if differences in instrumentation and observing\npractices require extra attention. This dataset consists of two main subsets:\n(1)\xa0 statistical metadata for each IGRA-RS station and year within the period\nof record; and (2)\xa0metadata for individual observations from each station.\nThese are complemented by (3)\xa0a list of the stations represented in the whole\ndataset, along with the observing periods for humidity (relative humidity or\ndew-point depression) and the corresponding counts of observations. The\ndataset is to be updated on a 2-year basis, starting in 2019, and is\navailable at https://doi.org/10.5281/zenodo.1332686 .