从NetCDF 4.5 Grib2Record提取天气预报数据

Question

更新 ：更改此问题以更好地反映我当前的理解。

我有一个NetCDF版本4.5 Grib2Record对象。 给定一个（x，y）网格点和一个变量名，我想按预测时间从对象中提取该变量的所有预测数据（如果记录包含该变量的预测）。 因为写磁盘索引文件的默认行为，我不希望使用更高级别的NetCDFFile接口。

我尝试查看较低级别的代码（Grib2Rectilyser，Grib2Customizer等），但是代码过于密集，我正在寻找从何处开始的帮助。

我将不胜感激关于如何获取Grib2Record的任何指示，以及1.检查是否包含特定的预测变量，以及2.如果包含，则按给定xy网格点的预测有效时间提取预测数据，并Z-水平。

Answer 1

我已经使用grib2文件进行风的预测，这就是我如何获取记录以及如何处理它以获取风（VU组件）的方法

Grib2Input input = new Grib2Input(getRandomAccessFile());
if (!input.scan(false, false)) {
    logger.error("Failed to successfully scan grib file");
    return;
}
Grib2Data data = new Grib2Data(getRandomAccessFile());

List<Grib2Record> records = input.getRecords();

for (Grib2Record record : records) {    
    Grib2IndicatorSection is = record.getIs();
    Grib2IdentificationSection id = record.getId();
    Grib2Pds pdsv = record.getPDS().getPdsVars();
    Grib2GDSVariables gdsv = record.getGDS().getGdsVars();

    long time = id.getRefTime() + (record.getPDS().getForecastTime() * 3600000);

    logger.debug("Record description at " + pdsv.getReferenceDate() + " forecast "
    + new Date(time)    + ": " + ParameterTable.getParameterName(is.getDiscipline(), pdsv.getParameterCategory(), pdsv.getParameterNumber()));

    float[] values = data.getData(record.getGdsOffset(), record.getPdsOffset(), 0);

     if ((is.getDiscipline() == 0) && (pdsv.getParameterCategory() == 2) && (pdsv.getParameterNumber() == 2)) {
        // U-component_of_wind
        int c = 0;
        for (double lat = gdsv.getLa1(); lat >= gdsv.getLa2(); lat = lat - gdsv.getDy()) {
            for (double lon = gdsv.getLo1(); lon <= gdsv.getLo2(); lon = lon + gdsv.getDx()) {
                logger.debug(lat + "\t" + lon + "\t" +
                values[c]);
                c++;
            }
        }
    } else if ((is.getDiscipline() == 0) && (pdsv.getParameterCategory() == 2) && (pdsv.getParameterNumber() == 3)) {
        // V-component_of_wind
        int c = 0;
        for (double lat = gdsv.getLa1(); lat >= gdsv.getLa2(); lat = lat - gdsv.getDy()) {
            for (double lon = gdsv.getLo1(); lon <= gdsv.getLo2(); lon = lon + gdsv.getDx()) {
                logger.debug(lat + "\t" + lon + "\t" +
                values[c]);
                c++;
            }
        }
    }
}

---

private RandomAccessFile getRandomAccessFile() {
    RandomAccessFile raf = null;
    try {
        raf = new RandomAccessFile(path, "r");
        raf.order(RandomAccessFile.BIG_ENDIAN);
    } catch (IOException e) {
        logger.error("Error opening file " + path, e);
    }
    return raf;
}