Precipitation trends over the Russian permafrost-free zone: Removing the artifacts of pre-processing

Rain gauge changes, changes in the number of observations per day, and inconsistent corrections to ob;served precipitation data during the 20th century of the meteorological network of the former Soviet Union make it difficult to address the issue of century time-scale precipitation changes. In this paper, we use daily and sub-daily synoptic data to account for the effects of these changes on the instrumental homogeneity of precipitation measurements over the Russian permafrost-free zone (RPF, most populous western and central parts of the country). Re-adjustments that were developed during this assessment allow us to (a) develop a system of scale corrections that remove the inhomogeneity owing to wetting/observation time changes over most of the former Soviet Union during the past century, and (b) to estimate precipitation trends over the RPF, reconciling previously contradictory results. The trend that emerges is an increase of about 5% per century. This estimate can be further refined after a more comprehensive set of supplementary data (precipitation type and wind) and metadata (information about the exposure of meteorological sites) is employed. Copyright (C) 2001 Royal Meteorological Society.