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A GPS dropsonde is a scientific instrument deployed from research and operational aircraft that descends through the atmosphere by a parachute. The dropsonde provides high-quality, high-vertical-resolution profiles of atmospheric pressure, [...]

Water vapor concentration structures in the atmosphere are well approximated by Gaussian Random Fields at small scales (≤ 6 km). These Gaussian Random Fields have a spatial correlation in accordance with a structure function with a twothirds slope, following the corresponding law from Kolmogorov's theory of turbulence. This is proven by showing that the structure function measured by several satellite instruments and radiosonde measurements do indeed follow the two-thirds law. High spatial resolution retrievals of Total Column Water Vapor (TCWV) obtained from the Ocean and Land Color Instrument (OLCI) on board of the Sentinel-3 series of satellites qualitatively also show a Gaussian Random Field structure. As a consequence, the atmosphere has an inherently stochastic component associated to the small scale water vapor features which, in turn, can make deterministic forecasting or Nowcasting difficult. These results can be useful in areas where a high resolution modeling of water vapor is required, such as the estimation of the water vapor variance within a region or when searching for consistency between different water vapor measurements in neighboring locations. [ABSTRACT FROM AUTHOR]

The Workshop to Improve the Usefulness of Operational Radiosonde Data was held at the NOAA National Climatic Data Center (NCDC) in Asheville, North Carolina, from 11 through 13 March 2003. It brought together users of global radiosonde data in numerical weather prediction, climate, and satellite data applications, along with a number of experts concerned with radiosonde instrument development, validation, and operational programs. This report provides a set of findings and recommendations produced by the group. The recommendations address issues in the areas of accuracy, calibration, and corrections of radiosonde measurements, sampling strategies, and the exchange of and response to information on data integrity, metadata, and data processing strategies.

This paper describes the GRUAN-wide approach to manage the transition from the Vaisala RS92 to the Vaisala RS41 as the operational radiosonde. The goal of the GCOS Reference Upper-Air Network (GRUAN) is to provide long-term high-quality reference observations of upper air Essential Climate Variables (ECVs) such as temperature and water vapor. With GRUAN data being used for climate monitoring, it is vital that the change of measurement system does not introduce inhomogeneities in to the data record. The majority of the 27 GRUAN sites were launching the RS92 as their operational radiosonde, and following the end of production of the RS92 in the last quarter of 2017, most of these sites have now switched to the RS41. Such a large-scale change in instrumentation is unprecedented in the history of GRUAN and poses a challenge for the network. Several measurement programmes have been initiated to characterize differences in biases, uncertainties and noise between the two radiosonde types. These include laboratory characterization of measurement errors, extensive twin sounding studies with RS92 and RS41 on the same balloon, and comparison with ancillary data. This integrated approach is commensurate with the GRUAN principles of traceability and deliberate redundancy. A two-year period of regular twin soundings is recommended, and for sites that are not able to implement this burden sharing is employed, such that measurements at a certain site are considered representative of other sites with similar climatological characteristics. All data relevant to the RS92-RS41 transition are archived in a database that will be accessible to the scientific community for external scrutiny. Furthermore, the knowledge and experience gained about GRUAN's RS92-RS41 transition will be extensively documented to ensure traceability of the process. This documentation will benefit other networks in managing changes in their operational radiosonde systems. Preliminary analysis of the laboratory experiments indicates that the manufacturer's calibration of the RS41's temperature and humidity sensors is more accurate than for the RS92; with uncertainties of < 0.1 K for the temperature and < 1 % RH for the humidity sensor. A first analysis of 224 RS92-RS41 twin soundings at Lindenberg Observatory show nighttime temperature differences < 0.1 K. However, daytime temperature differences in the stratosphere increase steadily with altitude, with TRS92-GDP.2 up to 0.6 K higher than TRS41 at 35 km. RHRS41 values are up to 8 % higher, which is consistent with the analysis of satellite-radiosonde collocations. [ABSTRACT FROM AUTHOR]