CSIRO ERA-40 2.5 deg by 2.5 deg archive (Grib & netCDF format ERA-40 datasets)

ERA-40 2.5° by 2.5° reanalysis archive containing primary (4-times daily GRIB) and processed (4-times daily and climatological netCDF)data. The atmospheric model used for ERA-40 has the identifier IFS CY23r4 and is comprehensively documented on the ECMWF website at http://www.ecmwf.int/research/ifsdocs/CY23r4/index.html. It has 60 levels in the vertical, uses a T159 spherical-harmonic representation for the dynamical fields, and a reduced Gaussian grid with an approximately uniform 125 kilometre spacing for surface and other grid-point fields. An essential part of the ERA-40 activity was the production of an archive of data in GRIB format. Parameters such as the 4-times daily surface and pressure level files were processed to produce COARDS conforming netCDF files which are self describing, machine transperant and which employ a similar metacode specification to that in the NCEP re-analysis files. This makes it possible for users of the NCEP/NCAR reanalysis to be able to easily switch data input to ERA-40. Only the 4-times daily GRIB files have been further processed and are on a 2.5 by 2.5 degree horizontal grid (144 by 73 regular grid points) for each of the standard 23 pressure levels (0001, 0002, 0003, 0005, 0007, 0010, 0020, 0030, 0050, 0070, 0100, 0150, 0200, 0250, 0300, 0400, 0500, 0600, 0700, 0775, 0850, 0925 and 1000)

ERA-40 2.5°×2.5°再分析数据集档案，包含原始数据（每日4次采样的GRIB格式）与经处理的数据（含每日4次采样及气候学netCDF格式数据）。用于ERA-40的大气模式标识符为IFS CY23r4，其完整文档可于欧洲中期天气预报中心（ECMWF）官网的http://www.ecmwf.int/research/ifsdocs/CY23r4/index.html 查阅。该模式垂直方向共60层，动力场采用T159球谐函数（spherical harmonic）表示，地表及其他格点场则使用约125公里均匀间距的缩减高斯格点（reduced Gaussian grid）。ERA-40项目的核心工作之一是构建GRIB格式的数据档案库。诸如每日4次采样的地表与等压层文件等参数，经处理后生成符合COARDS标准的netCDF文件——此类文件具备自描述性、机器透明性，且采用与美国国家环境预报中心（NCEP）再分析文件相似的元代码规范。这使得美国国家环境预报中心/美国国家大气研究中心（NCEP/NCAR）再分析数据的使用者能够轻松将数据输入切换至ERA-40数据集。仅每日4次采样的GRIB文件得到了进一步处理，被重采样至2.5°×2.5°的水平格网（共144×73个规则格点），覆盖标准的23个等压层：0001、0002、0003、0005、0007、0010、0020、0030、0050、0070、0100、0150、0200、0250、0300、0400、0500、0600、0700、0775、0850、0925及1000。