IGOR POLYAKOV
Igor V. Polyakov, Uma Bhatt, Roger L. Colony, Alexander P. Makshtas, and David Walsh
The data sets of monthly surface air temperature and sea level pressure contain data from land stations, Russian NP stations, and drifting buoys operated by the International Arctic Buoy Programme (IABP). Several databases are consolidated. The Arctic and Antarctic Research Institute (AARI) produced an extensive archive of SAT and SLP observations at Russian land stations. The EOS Distributed Active Archive Center (DAAC) at the National Snow and Ice Data Center (NSIDC), University of Colorado, Boulder, Meteorological Service of Canada, and NASA Goddard Institute for Space Studies provided monthly air temperatures for Europe, Greenland, Canadian Northwest Territories, and Alaska. The National Climatic Data Center (NCDC) database updated the records for the latter datasets to the end of 2000-beginning of 2001. Monthly SLP for western land stations have been obtained from UCAR, the EOS DAAC, and NCDC databases. The NP stations were continuously maintained from 1950 through 1991, with one to three stations operating at any given time. These observations are considered the most accurate for SAT in the Arctic Ocean (Rigor et al. 2000). Monthly gridded drifting buoy data for 1979-98 were obtained from the Polar Science Center of the University of Washington.
Historically, European countries have maintained good station coverage, providing the longest records of air temperature and pressure (Figure 1). Meteorological observations over land regions of Russia and Alaska also have reasonable station coverage and length. A few long time records are also available from the Northwest Territories of Canada. All the land station data have been assessed for homogeneity using interstation comparison (see discussion of homogeneity assessment techniques in Jones et al. (1999)). Monthly data have also been assessed for errors by identifying peaks exceeding 3 standard deviations and then checking them with nearby station records.
The region in the Canadian Basin from where the NP and buoy data were collected is highlighted in Figure 1 by a cross-hatched oval centered at 180E. This region was chosen because it contains the maximum density of NP stations. The size of the region is within the correlation length scale (CLS) introduced by Rigor et al. (2000) as a measure of how fast the SAT correlation decreases with distance. According to Rigor et al. (2000), a reasonable choice for the CLS is 900-1000 km for stations on the pack ice. A composite time series for SLP and SAT in the region for 1950-90 was constructed using the monthly data that was nearest the center of the NP region. SLP and SAT time series from the gridded IABP drifting buoy data for this same region were used to cover the period 1979-98. The overlapping period from these two data sets from 1979 through 1990 has been used to check the consistency between NP and buoy data. We compared monthly temperature and pressure from the NP stations with buoy observations interpolated to the location of the NP stations. On average, there was not a substantial bias in summer SAT between these two data sets because the buoy data have been previously filtered to match the statistics of the NP observations (Rigor et al. 2000). However, we found rather large differences in temperatures for the cold season (October-April) with an average bias of 1.5C (buoy SAT was warmer). We also found a slight, up to 0.5 mb, bias for the SLP records. These biases were removed from the buoy data before using these data to extend the NP region SAT and SLP time series to 1998.
Detailed description of the data may be found in (Polyakov et al., 2002a,b).
The SAT and SLP data are available on web (download the data now: Unix tar.gz format, or Windows zip format).
The Unix tar file "sat_slp.tar.gz" is compressed. To uncompress it, use the following command:
gunzip sat_slp.tar.gz
After this procedure the name of the file will become "sat_slp.tar".
This file is a converted form of a directory named "sat_slp". The command:tar xvf sat_slp.tar
will transfer this file to the directory "sat_slp".
This directory includes a README file containing instructions for reading data and a description of file structure.
The directory "sat_slp" also includes files with "raw" SAT and SLP data. For more information read the file "README" in "sat_slp".
Windows XP can handle the zip format internally, and there are several commercial and freeware programs (ZipCentral, StuffIt, WinZip, PKZip) for other versions of Windows.
Composite time series of the arctic (north of 62N) SAT (degC) and SLP (mb) anomalies are also available on web (download the data now). The form of the file is self-explanatory.
This data set is publicly available and its compilation was made possible through the cooperation of various international groups. We request that users acknowledge the use of this data set by including a citation to the paper [Polyakov I., et al., 2002a] in the reference list of published work. Thank you.
Jones, P. D., M. New, D. E. Parker, S. Martin, and I. G. Rigor, 1999: Surface air temperature and its changes over the past 150 years, Review of Geophysics, 37(2), 173-199.
Polyakov, I., R. V. Bekryaev, G. V. Alekseev, U. Bhatt, R. Colony, M. A. Johnson, D. Walsh, and A. P. Makshtas, 2002a: Variability and trends of air temperature and pressure in the maritime Arctic, 1875-2000, Journal of Climate 16 (12) : 2067-2077 [download PDF file]
Polyakov, I., G. V. Alekseev, R. V. Bekryaev, U. Bhatt, R. Colony, M. A. Johnson, V. P. Karklin, A. P. Makshtas , D. Walsh, and A. V. Yulin, 2002b: Observationally based assessment of polar amplification of global warming, Geophysical Research Letters1878 (doi:1029/2001GL011111) [download PDF file]
Rigor, I. G., R. L. Colony, and S. Martin, 2000: Variations in surface air temperature observations in the Arctic, 1979-97, J. Climate, 13, 896-914.
Last modified: December 10, 2004. 08:57:35 am