从 NetCDF 4.5 Grib2Record 中提取天气预报数据

Question

更新：更改了这个问题以更好地反映我目前的理解。

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）。由于写入磁盘索引文件的默认行为，我不想使用更高级别的 NetCDFFile 接口。

我尝试查看较低级别的代码（Grib2Rectilyser、Grib2Customizer 等），但代码太密集，我正在寻求帮助以了解从哪里开始。

如果有任何关于如何获取 Grib2Record 和 1. 检查特定预测变量是否包含在其中，以及 2. 如果包含，则按预测有效时间提取预测数据的指示，我将不胜感激给定 x-y 网格点和 z 级别。

Answer 1

我曾使用 grib2 文件进行风力预测，这就是我如何获取记录以及如何处理它以获得风力（V U 分量）

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;
}

从 NetCDF 4.5 Grib2Record 中提取天气预报数据

Extract weather forecast data from NetCDF 4.5 Grib2Record

java

hadoop

netcdf

grib