Abstract
Abstract. A site atmospheric state best estimate (SASBE) of the temperature profile above the GCOS (Global Climate Observing System) Reference Upper-Air Network (GRUAN) site at Lauder, New Zealand, has been developed. Data from multiple sources are combined within the SASBE to generate a high temporal resolution data set that includes an estimate of the uncertainty on every value.The SASBE has been developed to enhance the value of measurements made at the distributed GRUAN site at Lauder and Invercargill (about 180 km apart), and to demonstrate a methodology which can be adapted to other distributed sites. Within GRUAN, a distributed site consists of a cluster of instruments at different locations.The temperature SASBE combines measurements from radiosondes and automatic weather stations at Lauder and Invercargill, and ERA5 reanalysis, which is used to calculate a diurnal temperature cycle to which the SASBE converges in the absence of any measurements.The SASBE provides hourly temperature profiles at 16 pressure levels between the surface and 10 hPa for the years 1997 to 2012. Every temperature value has an associated uncertainty which is calculated by propagating the measurement uncertainties, the ERA5 ensemble standard deviations, and the ERA5 representativeness uncertainty through the retrieval chain. The SASBE has been long-term archived and is identified using the digital object identifier https://doi.org/10.5281/zenodo.1195779.The study demonstrates a method to combine data collected at distributed sites. The resulting best-estimate temperature data product for Lauder is expected to be valuable for satellite and model validation as measurements of atmospheric essential climate variables are sparse in the Southern Hemisphere. The SASBE could, for example, be used to constrain a radiative transfer model to provide top-of-the-atmosphere radiances with traceable uncertainty estimates.
Highlights
Measurements of the upper air are essential for atmospheric research and weather forecasts
This publication describes the development of a temperature site atmospheric state best estimate (SASBE) for the GCOS2 Reference Upper-Air Network (GRUAN) site at Lauder, New Zealand
A method to combine measurements from distributed sites is presented which accounts for the additional uncertainty that is introduced by using the measurement of an essential climate variable (ECV) made at one location as a proxy for the ECV at another location nearby
Summary
Measurements of the upper air are essential for atmospheric research and weather forecasts. While high vertical resolution temperature profiles can be retrieved from space-based instruments, these retrievals require validation, which is typically done by comparison with ground-based or in situ measurements. Ground-based techniques to observe upper-air temperatures include lidar and microwave radiometer, while in situ measurements are typically made using balloon-borne radiosondes. While radiosondes provide vertically highly resolved profiles of temperature, pressure and humidity, they are only used at about 800 upper-air sites worldwide (Ingleby, 2017), which typically launch two sondes per day. Given the limited spatio-temporal sampling of the radiosonde measurements, their use for satellite validation can be challenging as the number of collocations within a given time interval and distance is small If measurements from different instruments, or from collocated sites, can be combined in a best-estimate data product, the value of those measurements can be enhanced
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