Precipitation trends over the Russian permafrost‐free zone: removing the artifacts of pre‐processing

Abstract

Rain gauge changes, changes in the number of observations per day, and inconsistent corrections to observed 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.

A description of the global land-surface precipitation data products of the Global Precipitation Climatology Centre with sample applications including centennial (trend) analysis from 1901–present

“…The current GPCC collection encompasses regional data sets for the former Soviet Union (Groisman et al, 1991;Groisman and Rankova, 2001) with data from 2186 stations for the period 1891-2001, updated to 2009 by a data set comprising 518 Russian stations (available from http://meteo.ru/english/climate/precip. php) described by Bulygina et al (2010).…”

Precipitation characteristics of the Eurasian Arctic drainage system

“…Analysis of daily precipitation makes use of archived station time series for the FSU assembled by Groisman and Rankova (2001). The complete archive contains 2187 stations, with records for some available as far back as 1891.…”

“…From west to east, the watersheds are the Ob, Yenisey, Lena and Kolyma-Indigirka use records for the years 1960-92, which provides for a long period of overlap with reanalysis fields (see Section 2.2). The daily data are instrumentally homogeneous, but not bias adjusted (Groisman and Rankova, 2001). Bias adjustments relate primarily to gauge undercatch of blowing snow.…”

“…Figure 3 shows monthly mean precipitation totals and Figure 4 provides monthly means of the daily precipitation event size (the mean of all non-zero precipitation reports). Both are based on the Groisman and Rankova (2001) dataset. The most striking aspect of these figures is the approximate symmetry of the annual cycles around July maxima and winter minima.…”

Adjustment of global gridded precipitation for systematic bias

“…Wetting losses can be significant depending on the gauge type and the number of observations per day and are commonly on the order of 2 -10% [Sevruk, 1982]. However, as will be seen in section 4.3, recent studies have shown that average wetting losses are not as high as previously thought and that incorrect assumptions have been applied for some bias adjustment efforts [Bogdanova and Mestcherskaya, 1998;Groisman and Rankova, 2001]. Evaporation losses vary by gauge type and the time of year (i.e., winter losses are less than summer losses), and usually range from 0.1 to 0.8 mm/d [Goodison et al, 1998] or between 0 and 4% of the measured precipitation [Sevruk, 1982].…”