% Berkeley Earth Surface Temperature
% 
% README file for Gridded Data
% 
% This file describes the format used by the Berkeley Earth Surface 
% Temperature project for gridded data fields.  These fields contain
% reconstructed monthly temperature anomaly values generated by the
% Berkeley Earth project based on our method of climate analysis.
%
% At present all gridded data is provided via the NetCDF format (version
% 4).  NetCDF, short for Network Common Data Form, is a standardized data
% format commonly used for the exchange of large data sets, including
% weather data.  Tools for reading NetCDF are available in most major
% programming languages, including Matlab, R, C++, and others.
%
% File Naming Convention
%
% Gridded data files have names with the format:
%
%    <dataset abbreviation>_<variable name>_<type specifier>.nc
%
% The <dataset abbreviation> indicates the temperature data set from which 
% the analysis was constructed.  Currently, the only valid value for this
% is "Complete", indicating that all data from the Berkeley Earth data set
% was used.  In the future, GHCN and other alternative data sets may also
% be added.
%
% The <variable name> is an indicator of the kind of data in the file.
% Currently, valid options are TAVG, TMAX, and TMIN indicating fields for
% average temperature, maximum temperature, and minimum temperature,
% respectively.
% 
% The <type specifier> indicates the type of gridded data provided.
% Currently, the supported choices are "EqualArea" and "LatLong1".  
% "EqualArea", indicates a 15,984 element equal area grid which is the 
% format commonly used by the Berkeley Earth project to represent the globe 
% for many applications.  "LatLong1" is a resampled field using a 
% 1 degree-by-1 degree latitude-longitude grid covering the Earth.  This
% format is likely to be more useful for many applications.
%
% File Contents
%
% The following variables are presently included in the gridded data set:
%
%    latitude
%    longitude
%    time
%    temperature
%    land_mask
%    climatology
%
% latitude: A list of latitude values indicating grid box centers.  For
%   the "EqualArea" product it lists every grid box, and for the "LatLong1"
%   product it lists the centers for a single column.  Values are in degrees,
%   with positive values used for the Northern Hemisphere.
%
% longitude: A list of longitude values indicating grid box centers.  For
%   the "EqualArea" product it lists every grid box, and for the "LatLong1"
%   product it lists the centers for a single row.  Values are in degrees,
%   with positive values used for the Eastern Hemisphere.
%
% time: A list of times at which data is reported.  Data format is decimal
%   with year and fraction of year reported, with each value corresponding
%   to the midpoint of the respective month.  For example, 1981.125
%   indicates February 1981.  
%
% temperature: A surface air temperature anomaly field.  For "LatLong1"
%   case, the dimension are latitude x longitude x time.  For the
%   "EqualArea" case, the dimensions are number of grid cells x time.  Each
%   element measure the local temperature anomaly, in degrees C, for the 
%   corresponding location and time.  Missing values are reported as NaN.  
%   A value is reported as missing if the grid cell is less than 5% land or
%   if the coverage diagnostic indicates that the locally available data 
%   provides less than a 20% constraint on the anomaly.
%
% land_mask: For each grid cell, the fraction of the cell which corresponds
%   to land (as opposed to ocean or other large water bodies).  
%
% climatology: For each grid cell, an estimate of the true surface
%   temperature for each month during the period January 1951 to December
%   1980 reported in degrees C.  For "LatLong1", the dimensions are 
%   latitude x longitude x month, where month has length 12 and corresponds 
%   to January through December respectively.  Hence the first month is an 
%   estimated average for all Januarys from 1951 to 1980, teh second month 
%   is for all Februarys, etc.  For the "EqualArea" case, the dimensions 
%   are grid cell number x month.
%
%
% The gridded data files do not currently contain uncertainty information.