改进NetCDF数据读取

MeteoInfo

改进了NetCDF数据读取，可以处理不同的变量有不同的level维的情况，需要MeteoInfo最新文件（见置顶帖子）。来看下面的一个NetCDF数据：
File Name: F:\Temp\nc\fnl_20070716_00_00.nc
Dimensions: 12
    initial_time0_hours = 1;
    lat_3 = 181;
    lon_3 = 360;
    lv_PVL3 = 2;
    lv_ISBL4 = 26;
    lv_GPML5 = 3;
    lv_DBLY6 = 4;
    lv_ISBL7 = 2;
    lv_ISBL8 = 21;
    lv_SIGY9 = 4;
    lv_ISBL10 = 6;
    ncl_strlen_0 = 18;
Global Attributes: 6
    : creation_date = "Wed May  9 03:44:28 MDT 2012";
    : NCL_Version = "6.0.0";
    : system = "Linux mirage0 2.6.18-194.17.4.el5 #1 SMP Wed Oct 20 13:03:08 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux";
    : Conventions = "None";
    : grib_source = "fnl_20070716_00_00.grb";
    : title = "NCL: convert-GRIB-to-netCDF";
Variations: 89
    NC_CHAR initial_time0(initial_time0_hours,ncl_strlen_0);
        initial_time0: NCL_converted_from_type = "string";
        initial_time0: units = "mm/dd/yyyy (hh:mm)";
        initial_time0: long_name = "Initial time of first record";
    NC_FLOAT lon_3(lon_3);
        lon_3: units = "degrees_east";
        lon_3: grid_description = "65160-point (181x360) global longitude-latitude grid.  (0,0) at 0E, 90N, matrix layout.  N.B.: prime meridian not duplicated.";
        lon_3: long_name = "longitude";
    NC_FLOAT lat_3(lat_3);
        lat_3: units = "degrees_north";
        lat_3: grid_description = "65160-point (181x360) global longitude-latitude grid.  (0,0) at 0E, 90N, matrix layout.  N.B.: prime meridian not duplicated.";
        lat_3: long_name = "latitude";
    NC_INT lv_PVL3(lv_PVL3);
        lv_PVL3: units = "10^-6Km^2/kgs";
        lv_PVL3: long_name = "potential vorticity (pv) level";
    NC_INT lv_ISBL4(lv_ISBL4);
        lv_ISBL4: units = "hPa";
        lv_ISBL4: long_name = "isobaric level";
    NC_INT lv_GPML5(lv_GPML5);
        lv_GPML5: units = "m";
        lv_GPML5: long_name = "fixed height level";
    NC_INT lv_DBLY6_l0(lv_DBLY6);
        lv_DBLY6_l0: units = "cm";
        lv_DBLY6_l0: long_name = "layer between two depths below land surface";
    NC_INT lv_DBLY6_l1(lv_DBLY6);
        lv_DBLY6_l1: units = "cm";
        lv_DBLY6_l1: long_name = "layer between two depths below land surface";
    NC_INT lv_ISBL7(lv_ISBL7);
        lv_ISBL7: units = "hPa";
        lv_ISBL7: long_name = "isobaric level";
    NC_INT lv_ISBL8(lv_ISBL8);
        lv_ISBL8: units = "hPa";
        lv_ISBL8: long_name = "isobaric level";
    NC_INT lv_SIGY9_l0(lv_SIGY9);
        lv_SIGY9_l0: units = "sigma";
        lv_SIGY9_l0: long_name = "layer between two sigma levels";
    NC_INT lv_SIGY9_l1(lv_SIGY9);
        lv_SIGY9_l1: units = "sigma";
        lv_SIGY9_l1: long_name = "layer between two sigma levels";
    NC_INT lv_ISBL10(lv_ISBL10);
        lv_ISBL10: units = "hPa";
        lv_ISBL10: long_name = "isobaric level";
    NC_DOUBLE initial_time0_encoded(initial_time0_hours);
        initial_time0_encoded: units = "yyyymmddhh.hh_frac";
        initial_time0_encoded: long_name = "initial time encoded as double";
    NC_DOUBLE initial_time0_hours(initial_time0_hours);
        initial_time0_hours: units = "hours since 1800-01-01 00:00";
        initial_time0_hours: long_name = "initial time";
...

数据中有好几个Level维：lv_PVL3, lv_ISBL4 = 26, lv_GPML5 = 3, lv_DBLY6 = 4, lv_ISBL7 = 2, lv_ISBL8 = 21, lv_SIGY9 = 4, lv_ISBL10 = 6。后面还有很多变量，不同变量的Level维可能不一样。这个数据还存在一个问题，数据解码中需要确定每个维的具体数值（通常是个一维数组），维的数值要从“坐标变量”中读取，所谓坐标变量就是一维变量的名称和变量的维的名称是一样的，比如这个x维变量：
NC_FLOAT lon_3(lon_3);
        lon_3: units = "degrees_east";
        lon_3: grid_description = "65160-point (181x360) global longitude-latitude grid.  (0,0) at 0E, 90N, matrix layout.  N.B.: prime meridian not duplicated.";

但是此数据中有几个维没有确切的坐标变量，比如维：lv_SIGY9，和它相关的两个变量的名称都不是lv_SIGY9:
NC_INT lv_SIGY9_l0(lv_SIGY9);
        lv_SIGY9_l0: units = "sigma";
        lv_SIGY9_l0: long_name = "layer between two sigma levels";
NC_INT lv_SIGY9_l1(lv_SIGY9);
        lv_SIGY9_l1: units = "sigma";
        lv_SIGY9_l1: long_name = "layer between two sigma levels";

这种情况只能随机用其中一个变量来当做坐标变量读取维的数值了。不知道还有什么更好的处理方法？

mofangbao

这个不容易，下载新版的试一下。可惜俺还没有对NC的格式去仔细的了解