Global radiosonde network under pressure

Ingleby, Bruce ; Rodwell, Mark ; Isaksen, Lars

Année de publication
In early January 2015, ECMWF's automated monitoring system started warning of reductions in the number of Russian radiosonde reports. As a result of budget constraints, Russia had cut its radiosonde programme from two ascents per day to one. There were representations from ECMWF and WMO to the Federal Service for Hydrometeorology and Environmental Monitoring of Russia (Roshydromet) that this was a serious reduction in the global observing system. In its representations to Roshydromet, ECMWF was able to present results from experiments which showed that reductions in Russian radiosonde reports as seen in 2015 have a significant impact on forecast performance. At short range the increased errors are mainly over Russia, moving downstream over the Pacific at longer range and then affecting forecast scores for the whole of the northern hemisphere. In April 2015, Roshydromet reversed its decision and resumed making two ascents per day. More recently there were similar reductions to one ascent per day in Mexico and Brazil, where the number of stations affected is smaller but regionally significant. Over the last few years a number of remote island stations have also stopped making radiosonde reports or are planning to do so. The effects of smaller-scale reductions in the number of reports in other parts of the world are more difficult to assess. In some cases radiosonde reports are particularly important because they come from data-sparse areas. Beyond numerical weather prediction (NWP), radiosonde reports are also useful for general forecasting, climate studies and the calibration of satellite data.

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