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National Climatic Data Center, Asheville, NC 
A survey of data needs for the integrated assessment research community was conducted by ORNL. Comments and suggestions were received from individuals at 21 institutions in three countries (three government agencies, five national laboratories, nine universities, and four other research groups), providing valuable guidance to us in how we should proceed in documenting and formatting data bases to support this project. In general the monthly temperature time series for a country were of most interest (less so for annual values), with interest in both anomalies and min/max values. This group was also asked to prioritize which countries were most critical to their research. The three countries that were most important were India, China, and the United States. Other countries mentioned included Bangledesh, Nepal, Africa and Brazil. There are few products of gridded time series of temperature that can capture the trends for small spatial scales the size of countries. Most have been developed for signal detection of global climatic trends and have a coarse resolution (between 2.5 and 5 degrees longitude and latitude). This is why NCDC and ORNL decided to produce data and time series for a few countries as a pilot study to determine the usefulness to the scientific community at large. Initially, NCDC is providing monthly and annual temperature time series for India, China, and the United States. The time series that are produced use the GHCN Version 2 database and the Climate Analysis System (CAS) developed at NCDC. The anomalies are calculated using the First Difference Method, an approach developed to maximize the use of available station records (see, e.g., Peterson et al., 1998, 'The First Difference Method: Maximizing Station Density for the Calculation of Long-term Global Temperature Change', Journal of Geophysical Research). The First Difference Method involves calculating a series of calender-month differences in temperature between successive years of station data (FDyr = Tyr - Tyr-1). For example, when creating a station's first difference series for mean February temperature, we subtract the station's February 1880 temperature from the station's Februrary 1881 temperature to create a February 1881 first difference value. First difference values for subsequent years are calculated in the same fashion by subtracting the station's preceding year temperature for all available years of station data. Station coordinates are used to make grid box assignments for each station in the selected region based on the selected grid box size. For each year and month, the 'first difference' values of all stations located within a grid box are summed. The resulting sum is then divided by the total number of stations in the grid box to get an unweighted first difference value for each grid box. To obtain an average time series value for the selected region, a weighted average of the gridded first difference values is calculated. For every year and month, each gridded value is weighted by the cosine of the central latitude point of the grid box. All weighted grid box values are then averaged to obtain a global or region-wide first difference value. A time series is produced for each month by calculating a cumulative sum of the first difference values over all years. The cumulative sum is calculated for each month of first difference data independently through time.
The resulting time series is adjusted to create anomalies with respect to the base period, typically 1961 - 1990. Each country is gridded to a 1x1 grid and area weighted according to the intersection of the countries boundary with each grid box. The images of China, India, and the United States show the station distribution over the entire period of record (at any given time step this would be the maximum number of stations used to calculate the temperature for that particular country). DATA...
Additional Graphics
for further information , contact: NOAA/National Climatic Data Center 151 Patton Avenue Asheville, NC 28801-5001 fax: 828-271-4330 email: bruce.baker@noaa.gov Robert M. Cushman Carbon Dioxide Information Analysis Center Environmental Sciences Division Oak Ridge National Laboratory U.S. Department of Energy Building 1509, Mail Stop 6335 Oak Ridge, TN 37831-6335 U.S.A. email: rma@ornl.gov or further information on GHCN, contact: NOAA/National Climatic Data Center 151 Patton Avenue Asheville, NC 28801-5001 fax: 828-271-4328 email: thomas.c.peterson@noaa.gov
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