参数数据库
GRIB 1 参数（WMO 编码）
10 metre U wind component
indicatorOfParameter = 33 [u-compoment of wind (m/s)]
table2Version = 3
indicatorOfTypeOfLevel = 105 [Specified height level above ground (m)]
level = 10
GRIB 2 参数（WMO 编码）
10 metre U wind component
discipline = 0 [Meteorological products]
parameterCategory = 2 [Monmentum]
parameterNumber = 2 [u-component of wind (m s-1)]
typeOfFirstFixedSurface = 103 [Specified height level above ground (m)]
scaleFactorOfFirstFixedSurface = 0
scaledValueOfFirstFixedSurface = 10
GRIB 1 参数（ECMWF 本地编码）
10 metre U wind component
indicatorOfParameter =165 [10 metere u-compoment of wind (m/s)]
table2Version = 128
ecCodes 的解决方案
有多种编码变量的方法。
ecCodes 使用一个虚拟的 key（计算key）来解耦用户层和编码层。
用户代码获取/设置一个虚拟 key，ecCodes 获取/设置实际编码的 key。
本地配置用于处理本地编码。
ecCodes 变量
ecCodes 提供一些版本无关的 key 用于定义变量：
paramIdshortNamenameunitscentre
GRIB 1 使用如下 key：
centretable2VersionindicatorOfParameterlevelTypelevel- ...
GRIB 2 使用如下 key：
disciplineparameterCategoryparameterNumbertypeOfFirstFixedSurfacescaleFactorOfFirstFixedSurfacescaledValueOfFirstFixedSurfacetypeOfSecondFixedSurfacescaleFactorOfSecondFixedSurfacescaledValueOfSecondFixedSurface- ...
概念
之前的章节中介绍过 ecCodes 的架构：
下面介绍几个与变量有关的重要概念。
shortName
GRIB 2：
'2t' = {
discipline=0;
parameterCategory=0;
parameterNumber=0;
typeOfFirstFixedSurface=103;
scaleFactorOfFirstFixedSurface=0;
scaledValueOfFirstFixedSurface=2;
}
GRIB 1：
'2t' = {
indicatorOfParameter=11;
table2Version=3;
levelType=105;
level=2;
}
GRIB 1 ECMWF 本地编码：
'2t' = {
indicatorOfParameter=167;
table2Version=128;
}
paramId
GRIB 2：
167 = {
discipline=0;
parameterCategory=0;
parameterNumber=0;
typeOfFirstFixedSurface=103;
scaleFactorOfFirstFixedSurface=0;
scaledValueOfFirstFixedSurface=2;
}
GRIB 1：
167 = {
indicatorOfParameter=11;
table2Version=3;
levelType=105;
level=2;
}
GRIB 1 ECMWF 本地编码：
167 = {
indicatorOfParameter=167;
table2Version=128;
}
ecCodes 使用的 GRIB 参数
访问如下网址，查询参数数据库：
http://apps.ecmwf.int/codes/grib/param-db/
练习
创建两个文件
#include <iostream> #include <eccodes.h> using namespace std; int main(int argc, char** argv) { if(argc < 3) { cout<<"Usage: "<<argv[0]<<" grib1_path grib2_path"; return 1; } const char* grib1_path = argv[1]; const char* grib2_path = argv[2]; const char* sample_filename = "regular_ll_pl_grib2"; int err = 0; codes_handle *h = codes_grib_handle_new_from_samples(nullptr, sample_filename); if(h == nullptr) { cout<<"ERROR: unable to create handle from sample "<<sample_filename<<endl; return 1; } size_t short_name_size; codes_get_size(h, "shortName", &short_name_size); codes_set_string(h, "shortName", "10u", &short_name_size); size_t value_size; codes_get_size(h, "values", &value_size); auto values = new double[value_size]; double v = 0; for(auto i=0; i<value_size; i++) { values[i] = v; v++; } // codes_set_long(h, "bitsPerValue", 16); codes_set_double_array(h, "values", values, value_size); codes_write_message(h, grib2_path, "wb"); codes_set_long(h, "edition", 1); codes_write_message(h, grib1_path, "wb"); delete [] values; codes_handle_delete(h); return 0; }使用
grib_ls -n parameter p.grib1 p.grib2查看有何不同。$ grib_ls -n parameter p.grib1 p.grib2 p.grib1 centre paramId units name shortName ecmf 130 K Temperature t 1 of 1 messages in p.grib1 p.grib2 ecmf 130 K Temperature t 1 of 1 messages in p.grib2 2 of 2 total messages in 2 files使用
grib_dump -o比较两个文件不同。查看 GRIB 1 文件
p.grib1：$ grib_dump -O p.grib1 ***** FILE: p.grib1 #============== MESSAGE 1 ( length=1596 ) ============== 1-4 identifier = GRIB 5-7 totalLength = 1596 8 editionNumber = 1 ====================== SECTION_1 ( length=52, padding=0 ) ====================== 1-3 section1Length = 52 4 table2Version = 128 5 centre = 98 [European Centre for Medium-Range Weather Forecasts (common/c-1.table) ] 6 generatingProcessIdentifier = 128 7 gridDefinition = 255 8 section1Flags = 128 [10000000] 9 indicatorOfParameter = 165 [10 metre U wind component (m s**-1) (grib1/2.98.128.table) ] 10 indicatorOfTypeOfLevel = 105 [Fixed height above ground height in meters (2 octets) (grib1/local/ecmf/3.table , grib1/3.table) ] 11-12 level = 10 13 yearOfCentury = 7 14 month = 3 15 day = 23 16 hour = 12 17 minute = 0 18 unitOfTimeRange = 1 [Hour (grib1/4.table) ] 19 P1 = 0 20 P2 = 0 21 timeRangeIndicator = 0 [Forecast product valid at reference time + P1 (P1>0) (grib1/local/ecmf/5.table , grib1/5.table) ] 22-23 numberIncludedInAverage = 0 24 numberMissingFromAveragesOrAccumulations = 0 25 centuryOfReferenceTimeOfData = 21 26 subCentre = 0 [Unknown code table entry (grib1/0.ecmf.table) ] 27-28 decimalScaleFactor = 0 29-40 reservedNeedNotBePresent = 12 { 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00 } # pad reservedNeedNotBePresent 41 localDefinitionNumber = 1 [MARS labelling or ensemble forecast data (grib1/localDefinitionNumber.98.table) ] 42 marsClass = 1 [Operational archive (mars/class.table) ] 43 marsType = 2 [Analysis (mars/type.table) ] 44-45 marsStream = 1025 [Atmospheric model (mars/stream.table) ] 46-49 experimentVersionNumber = 0001 50 perturbationNumber = 0 51 numberOfForecastsInEnsemble = 0 52 padding_local1_1 = 1 { 00 } # pad padding_local1_1 ====================== SECTION_2 ( length=32, padding=0 ) ====================== 1-3 section2Length = 32 4 numberOfVerticalCoordinateValues = 0 5 pvlLocation = 255 6 dataRepresentationType = 0 [Latitude/Longitude Grid (grib1/6.table) ] 7-8 Ni = 16 9-10 Nj = 31 11-13 latitudeOfFirstGridPoint = 60000 14-16 longitudeOfFirstGridPoint = 0 17 resolutionAndComponentFlags = 128 [10000000] 18-20 latitudeOfLastGridPoint = 0 21-23 longitudeOfLastGridPoint = 30000 24-25 iDirectionIncrement = 2000 26-27 jDirectionIncrement = 2000 28 scanningMode = 0 [00000000] 29-32 zero = ====================== SECTION_4 ( length=1500, padding=0 ) ====================== 1-3 section4Length = 1500 4 dataFlag = 8 [00001000] 5-6 binaryScaleFactor = -15 7-10 referenceValue = 0 11 bitsPerValue = 24 12-1500 values = (496,1489) { ... } # data_g1simple_packing values ====================== SECTION_5 ( length=4, padding=0 ) ====================== 1-4 7777 = 7777查看 GRIB 2 文件
p.grib2：$ grib_dump -O p.grib2 ***** FILE: p.grib2 #============== MESSAGE 1 ( length=1667 ) ============== 1-4 identifier = GRIB 5-6 reserved = MISSING 7 discipline = 0 [Meteorological products (grib2/tables/4/0.0.table) ] 8 editionNumber = 2 9-16 totalLength = 1667 ====================== SECTION_1 ( length=21, padding=0 ) ====================== 1-4 section1Length = 21 5 numberOfSection = 1 6-7 centre = 98 [European Centre for Medium-Range Weather Forecasts (common/c-11.table) ] 8-9 subCentre = 0 10 tablesVersion = 4 [Version implemented on 7 November 2007 (grib2/tables/1.0.table) ] 11 localTablesVersion = 0 [Local tables not used (grib2/tables/4/1.1.table) ] 12 significanceOfReferenceTime = 1 [Start of forecast (grib2/tables/4/1.2.table) ] 13-14 year = 2007 15 month = 3 16 day = 23 17 hour = 12 18 minute = 0 19 second = 0 20 productionStatusOfProcessedData = 0 [Operational products (grib2/tables/4/1.3.table) ] 21 typeOfProcessedData = 2 [Analysis and forecast products (grib2/tables/4/1.4.table) ] ====================== SECTION_3 ( length=72, padding=0 ) ====================== 1-4 section3Length = 72 5 numberOfSection = 3 6 sourceOfGridDefinition = 0 [Specified in Code table 3.1 (grib2/tables/4/3.0.table) ] 7-10 numberOfDataPoints = 496 11 numberOfOctectsForNumberOfPoints = 0 12 interpretationOfNumberOfPoints = 0 [There is no appended list (grib2/tables/4/3.11.table) ] 13-14 gridDefinitionTemplateNumber = 0 [Latitude/longitude (Also called equidistant cylindrical, or Plate Carree) (grib2/tables/4/3.1.table) ] 15 shapeOfTheEarth = 6 [Earth assumed spherical with radius of 6,371,229.0 m (grib2/tables/4/3.2.table) ] 16 scaleFactorOfRadiusOfSphericalEarth = MISSING 17-20 scaledValueOfRadiusOfSphericalEarth = MISSING 21 scaleFactorOfEarthMajorAxis = MISSING 22-25 scaledValueOfEarthMajorAxis = MISSING 26 scaleFactorOfEarthMinorAxis = MISSING 27-30 scaledValueOfEarthMinorAxis = MISSING 31-34 Ni = 16 35-38 Nj = 31 39-42 basicAngleOfTheInitialProductionDomain = 0 43-46 subdivisionsOfBasicAngle = MISSING 47-50 latitudeOfFirstGridPoint = 60000000 51-54 longitudeOfFirstGridPoint = 0 55 resolutionAndComponentFlags = 48 [00110000] 56-59 latitudeOfLastGridPoint = 0 60-63 longitudeOfLastGridPoint = 30000000 64-67 iDirectionIncrement = 2000000 68-71 jDirectionIncrement = 2000000 72 scanningMode = 0 [00000000] ====================== SECTION_4 ( length=34, padding=0 ) ====================== 1-4 section4Length = 34 5 numberOfSection = 4 6-7 NV = 0 8-9 productDefinitionTemplateNumber = 0 [Analysis or forecast at a horizontal level or in a horizontal layer at a point in time (grib2/tables/4/4.0.table) ] 10 parameterCategory = 2 [Momentum (grib2/tables/4/4.1.0.table) ] 11 parameterNumber = 2 [u-component of wind (m s-1) (grib2/tables/4/4.2.0.2.table) ] 12 typeOfGeneratingProcess = 0 [Analysis (grib2/tables/4/4.3.table) ] 13 backgroundProcess = 255 14 generatingProcessIdentifier = 128 15-16 hoursAfterDataCutoff = 0 17 minutesAfterDataCutoff = 0 18 indicatorOfUnitOfTimeRange = 1 [Hour (grib2/tables/4/4.4.table) ] 19-22 forecastTime = 0 23 typeOfFirstFixedSurface = 103 [Specified height level above ground (m) (grib2/tables/4/4.5.table) ] 24 scaleFactorOfFirstFixedSurface = 0 25-28 scaledValueOfFirstFixedSurface = 10 29 typeOfSecondFixedSurface = 255 [Missing (grib2/tables/4/4.5.table) ] 30 scaleFactorOfSecondFixedSurface = MISSING 31-34 scaledValueOfSecondFixedSurface = MISSING ====================== SECTION_5 ( length=21, padding=0 ) ====================== 1-4 section5Length = 21 5 numberOfSection = 5 6-9 numberOfValues = 496 10-11 dataRepresentationTemplateNumber = 0 [Grid point data - simple packing (grib2/tables/4/5.0.table) ] 12-15 referenceValue = 0 16-17 binaryScaleFactor = -15 18-19 decimalScaleFactor = 0 20 bitsPerValue = 24 21 typeOfOriginalFieldValues = 0 [Floating point (grib2/tables/4/5.1.table) ] ====================== SECTION_6 ( length=6, padding=0 ) ====================== 1-4 section6Length = 6 5 numberOfSection = 6 6 bitMapIndicator = 255 [A bit map does not apply to this product (grib2/tables/4/6.0.table) ] ====================== SECTION_7 ( length=1493, padding=0 ) ====================== 1-4 section7Length = 1493 5 numberOfSection = 7 6-1493 codedValues = (496,1488) { ... } # data_g2simple_packing codedValues ====================== SECTION_8 ( length=4, padding=0 ) ====================== 1-4 7777 = 7777