(Phys.org) -- Direct, reliable observations of atmospheric conditions stretch as far back as the mid seventeenth century, with otherwise consistent records being punctuated by periodic updates in methods, practitioners, and observational equipment. To bridge these shifts in technique and technology, scientists develop reanalysis models designed to tie together diverse observations into a coherent picture of the system's evolution. But, like all models or analytical techniques, reanalysis data sets can suffer from errors or biases. Identifying how the records produced by different reanalyses vary can be a difficult practice, but determining if a cluster of models consistently produces biased results can be even more difficult.
A number of reanalyses have recently been developed to track the rapidly changing Arctic atmosphere, and Serreze et al.compared them with one another and with the observational record. The authors focused on how the reanalyses represent the change in Arctic tropospheric water vapor from 1979 to 2010. They compared three of the most recent and complex reanalyses against meteorological measurements made using radiosondes at nine sites north of 70 degrees North. They find that the reanalyses consistently overestimate low-altitude temperatures and winter humidity. It is important to note that these positive biases caused the reanalyses to miss low-altitude wintertime temperature and humidity inversions identified by the radiosondes.
A finding shared by both reanalyses and radiosonde observations, however, is of an increasing availability of precipitable water in the low-altitude Arctic, which the authors suggest is associated with increasing air-sea surface temperatures, reduced sea ice extent, and other markers consistent with the polar amplification of global warming. Increasing Arctic humidity is a troubling result, as heightening atmospheric water vapor could further drive up regional temperatures.
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More information: Recent changes in tropospheric water vapor over the Arctic as assessed from radiosondes and atmospheric reanalyses Journal of Geophysical Research-Atmospheres, doi:10.1029/2011JD017421 , 2012.