Global radiosonde balloon drift statistics

Abstract

[1] The drift of radiosonde balloons during their ascent has generally been considered a negligible factor in applications involving radiosonde observations. However, several applications envisioned for observations from the Global Climate Observing System (GCOS) Reference Upper Air Network (GRUAN) require estimates of balloon drift. This study presents a comprehensive global climatology of radiosonde balloon drift distance and ascent time, based on 2 years of data from 419 stations, with particular attention to GRUAN stations. Typical drift distances are a few kilometers in the lower troposphere, ∼5 km in the midtroposphere, ∼20 km in the upper troposphere, and ∼50 km in the lower stratosphere, although there is considerable variability due to variability in climatological winds. Drift distances tend to increase with height above the surface, be larger in midlatitudes than in the tropics, be larger in winter than in summer, and vary with wind (and consequent balloon drift) direction. Most estimates of elapsed time from balloon launch to various pressure levels, due to vertical balloon rise, have median values ranging from about 5 min at 850 hPa to about 1.7 h at 10 hPa, with ranges of about 20% of median values. Observed elapsed times exceed those estimated using assumed 5 or 6 m/s rise rates.

Assessment of GPS radiosonde descent data

“…The observed drifts closely match with the background wind velocities as expected (i.e., the higher the wind velocities, the larger the radiosonde drifts and vice versa). Though we cannot directly compare our results with those reported by Houchi et al (2010) and Seidel et al (2011) (as they have not included any Indian radiosonde observations) on the balloon drifts, note that drifts are larger at our location in contrast to those reported by them. Seidel et al (2011) reported that drifts are larger at mid-latitudes than the tropics, but even at a tropical latitude station like Gadanki, we could notice large drifts.…”

“…Though we cannot directly compare our results with those reported by Houchi et al (2010) and Seidel et al (2011) (as they have not included any Indian radiosonde observations) on the balloon drifts, note that drifts are larger at our location in contrast to those reported by them. Seidel et al (2011) reported that drifts are larger at mid-latitudes than the tropics, but even at a tropical latitude station like Gadanki, we could notice large drifts. Another striking difference observed is that summer season drifts are larger than winter drifts unlike those reported by Seidel et al (2011).…”

“…Seidel et al (2011) reported that drifts are larger at mid-latitudes than the tropics, but even at a tropical latitude station like Gadanki, we could notice large drifts. Another striking difference observed is that summer season drifts are larger than winter drifts unlike those reported by Seidel et al (2011). These differences are arising mainly due to prevailing strong tropical easterly jets over the Indian region, whereas the drifts at the mid-latitudes are due to the prevailing subtropical jets (Seidel et al, 2011).…”

Toward improved corrections for radiation‐induced biases in radiosonde temperature observations

“…GPSRO and radiosonde profiles differ in several ways in terms of measurement characteristics, including profile geometry and horizontal resolution. A radiosonde makes point measurements but balloon drifts an average of 50 km horizontally during the~100 min ascent from the surface to the stratosphere [Seidel et al, 2011]. Although GPSRO profiles have fine vertical resolution (0.5 km in the low troposphere and 1.5 km in the middle atmosphere) by satellite retrieval standards, they have a wide horizontal resolution, ranging from~160 km at the low troposphere to 320 km in the upper atmosphere (i.e.,~250 km, defined by the distance traversed by the radio path as it enters and exits a layer [Kursinski et al, 1997]).…”

Modelling collocation uncertainty of 3D atmospheric profiles

“…Understanding collocation mismatch is particularly relevant for atmospheric profiles obtained by radiosondes, as the ballons containing the measuring instruments tend to drift uncontrollably from their initial launch position (see [26] and [5]). In particular, collocation mismatch may depend on potential covariates.…”