Completeness of radiosonde humidity observations based on the Integrated Global Radiosonde Archive

Abstract

Abstract. Radiosonde measurements from the 1930s to present give unique information on the distribution and variability of water vapor in the troposphere. The sounding data from the Integrated Global Radiosonde Archive (IGRA) Version 2 are examined here until the end of 2016, aiming to describe the completeness of humidity observations (simultaneous measurements of pressure, temperature, and humidity) in different times and locations. Upon finding the stations with a non-negligible number of radiosonde observations in their period of record, thus removing pilot-balloon stations from IGRA, the selected set (designated IGRA-RS) comprises 1723 stations, including 1300 WMO stations, of which 178 belong to the current GCOS Upper-Air Network (GUAN) and 16 to the GCOS Reference Upper-Air Network (GRUAN). Completeness of humidity observations for a radiosonde station and a full year is herein defined by five basic parameters: number of humidity soundings, fraction of days with humidity data, average vertical resolution, average atmospheric pressure and altitude at the highest measuring level, and maximum number of consecutive days without data. The observations eligible for calculating precipitable water vapor – i.e., having adequate vertical sampling between the surface and 500 hPa – are particularly studied. The present study presents the global coverage of humidity data and an overall picture of the temporal and vertical completeness parameters over time. This overview indicates that the number of radiosonde stations potentially useful for climate studies involving humidity depends not only on their record length, but also on the continuity, regularity, and vertical sampling of the humidity time series. Additionally, a dataset based on IGRA is described with the purpose of helping climate and environmental scientists to select radiosonde data according to various completeness criteria – even if differences in instrumentation and observing practices require extra attention. This dataset consists of two main subsets: (1) statistical metadata for each IGRA-RS station and year within the period of record; and (2) metadata for individual observations from each station. These are complemented by (3) a list of the stations represented in the whole dataset, along with the observing periods for humidity (relative humidity or dew-point depression) and the corresponding counts of observations. The dataset is to be updated on a 2-year basis, starting in 2019, and is available at https://doi.org/10.5281/zenodo.1332686.

Radiosounding HARMonization (RHARM): a new homogenized dataset of radiosounding temperature, humidity and wind profiles with uncertainty

“…Table 2 confirms the low number of measurements available in the Southern Hemisphere (SH), although it is already known that the quantity of measurements alone cannot address the value of the dataset for a specific study without a representativeness study (Weatherhead et al, 2017). Further in-depth statistical analysis of the IGRA Version 2 historical times series and their temporal and spatial coverage at different pressure levels is available in Durre et al (2018) and in Ferreira et al (2019), the latter for relative humidity observations only. Another statistical analysis of the missing data and of their spatial coverage is provided in Sy et al (2020).…”

Atmospheric River Signatures in Radiosonde Profiles and Reanalyses at the Dronning Maud Land Coast, East Antarctica

“…During 2009−19, radiosondes were regularly launched once per day, at 1200 UTC, at Neumayer station (which is also local time), and twice per day, at 0000 and 1200 UTC, at Syowa station (local time UTC+3). According to Ferreira et al (2019), Neumayer and Syowa stations have an acceptable completeness of radiosonde observations for our analysis. Because of the low temporal resolution of regular radiosonde observations and reduced vertical resolution available via IGRA2, these data can be used only for detecting large-scale features and not for detailed analysis of small-scale variability.…”

Sensitivity of trends to estimation methods and quantification of subsampling effects in global radiosounding temperature and humidity time series

“…For instance, as we mentioned above, missing data are an intrinsic dataset characteristic due to a lack of continuity in operations contingently occurring at each measuring station. Although the completeness of historical radiosounding observations is improving over the years (Ferreira et al ., 2019), missing data in the time series are still frequent. This implies that, to provide a reliable assessment of the uncertainties affecting the estimation of trends using radiosounding data, the separate roles of temporal and spatial sampling effects due to the missing data must be considered.…”

“…Among the list of stations available from the IGRA data repository, a substantial subset of globally distributed radiosounding stations (656 stations) was used in this paper (Figure 1), namely, those with metadata available since 2000 to present. Ferreira et al (2019) found that the total number, spatial distribution and temporal completeness of IGRA stations vary considerably over the years due to several factors, and the number of vertical levels and the vertical extent in radiosonde reports depend on the standard and mandatory pressure levels provided according to the World Meteorological Organization (WMO) recommendations (WMO, 1996) to the Met services, as well as on the number of reported significant levels. Finally, due to various reasons, missing data are frequently found.…”