制作nc文件流程——以站点降水数据为例

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netcdf文件制作流程

- - 1. define dimensions
  - 2. define variables
  - 3. put variables into nc
  - 4. put attribute into nc
  - 5. define global attribution
  - 6.附上代码全文

【提示】 事先想好需要存储变量的结构及维度，之后需要注意的是创建 nc 文件的 $\color{#FF0000}{类型}$ ，以下供参考：

Value of cmode	Description
‘NOCLOBBER’	Prevent overwriting of existing file with the same name.（不覆盖已经有的同名文件）
‘CLOBBER’	Overwrite any existing file with the same name.（覆盖任何已有的同名文件）
‘SHARE’	Allow synchronous file updates.（允许同步文件更新）
‘64BIT_OFFSET’	Allow easier creation of files and variables which are larger than two gigabytes.（可创建>2G的文件）
‘NETCDF4’	Create a NetCDF-4/HDF5 file（普通）
‘CLASSIC_MODEL’	Enforce the classic model; has no effect unless used in a bitwise-or with NETCDF4

outDir     = 'H:\TempData\SationPrecp';
outFile    = 'Precip_Daily_2481stations_China.nc';
outDirFile = [outDir, '\', outFile];
outid      = netcdf.create(outDirFile, '64BIT_OFFSET');

1. define dimensions

numStatdimID = netcdf.defDim(outid,'numStat', 2481);
yeardimID     = netcdf.defDim(outid,'year', 68);
mondimID     = netcdf.defDim(outid,'mon', 12);
daydimID    = netcdf.defDim(outid,'day', 31);

2. define variables

lon_id  = netcdf.defVar(outid,'lon','NC_FLOAT', numStatdimID);
lat_id  = netcdf.defVar(outid,'lat','NC_FLOAT', numStatdimID);
alt_id  = netcdf.defVar(outid,'alt','NC_FLOAT', numStatdimID);
Prec_id = netcdf.defVar(outid,'Prec','NC_FLOAT',[daydimID, mondimID, yeardimID, numStatdimID]);netcdf.endDef(outid);

3. put variables into nc

【提醒】 注意放置的数据时，变量一定要和自己在 2.定义维度 时的矩阵形状完全一致才行！这个形状也就是matllab 中用 $\color{FF0000}{ncdisp(ncname)}$ 函数显示出来的矩阵形状。

netcdf.putVar(outid, lon_id, UnqLon/100);
netcdf.putVar(outid, lat_id, UnqLat/100);
netcdf.putVar(outid, alt_id, UnqAlt/100);
netcdf.putVar(outid, Prec_id, Precmmd);netcdf.reDef(outid);

4. put attribute into nc

netcdf.putAtt(outid, lon_id, 'longname', 'longitude');
netcdf.putAtt(outid, lon_id, 'units', 'degrees_east');netcdf.putAtt(outid, lat_id, 'longname', 'latitude');
netcdf.putAtt(outid, lat_id, 'bounds', 'degrees_north');netcdf.putAtt(outid, alt_id, 'longname', 'height above sea level');
netcdf.putAtt(outid, alt_id, 'units', 'm');netcdf.putAtt(outid, Prec_id, 'longname', 'daily rainfall');
netcdf.putAtt(outid, Prec_id, 'units', 'mm/day');
netcdf.putAtt(outid, Prec_id, '_FillValue', single(-999));
netcdf.putAtt(outid, Prec_id, 'missing_value', single(-999));

5. define global attribution

netcdf.putAtt(outid, netcdf.getConstant('NC_GLOBAL'), 'title', 'station daily rainfall data');
netcdf.putAtt(outid, netcdf.getConstant('NC_GLOBAL'), 'Data_Period', '1951-2018');
netcdf.putAtt(outid, netcdf.getConstant('NC_GLOBAL'), 'Author', 'Dayang Wang, SYSU, Email : wangdy58@mail2.sysu.edu.cn');
netcdf.putAtt(outid, netcdf.getConstant('NC_GLOBAL'), 'History', ['created on: ',datestr(now)]);netcdf.close(outid);

6.附上代码全文

% % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % 
% Aim: this script aim at transfering Precp data of Station to nc type file
% Date: 2021-03-03
% Author: Dayang Wang, Sun Yat-sen University
% % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % tic
clc; clear;
% read data from station 
inDir = ('H:\TempData\SationPrecp');
inFile = ('PREC_Stn2481.mat');
inDirFile = [inDir, '\', inFile];
load (inDirFile);stationId = PREC(:, 1);
N = length(stationId);
Lat  = PREC(:, 2);
Lon  = PREC(:, 3);
Alt  = PREC(:, 4);
Year = PREC(:, 5);
Month = PREC(:, 6);
Day   = PREC(:, 7);
ValPrecp = PREC(:, 8);[Unqid, ind, ~] = unique(stationId, 'stable');
UnqLat = Lat(ind);
UnqLon = Lon(ind);
UnqAlt = Alt(ind);numStat = length(Unqid);
for i = 1 : numStat stationId(stationId == Unqid(i)) = i;
endYRbeg = min(Year);
YRend = max(Year);
numYR = YRend - YRbeg + 1;
for j = 1 : numYRYear(Year == YRbeg + j - 1 ) = j;
endPrecmmd = -999 * ones(31, 12, numYR, numStat);for k = 1 : NiDay  = Day(k);iMon  = Month(k);iYear = Year(k);iStat = stationId(k);Precmmd(iDay, iMon, iYear, iStat) = ValPrecp(k);% check scheduleif mod(k, 10^6) == 0disp(['----- ',num2str(k),' -----'])end
endPrecmmd = single(Precmmd);% PREC = [Day, Month, Year, stationId];%----------------------------------------------------------------------
% make nc
%----------------------------------------------------------------------
outDir     = 'H:\TempData\SationPrecp';
outFile    = 'Precip_Daily_2481stations_China.nc';
outDirFile = [outDir, '\', outFile];
outid      = netcdf.create(outDirFile, '64BIT_OFFSET');% define dimensions
numStatdimID = netcdf.defDim(outid,'numStat', 2481);
yeardimID     = netcdf.defDim(outid,'year', 68);
mondimID     = netcdf.defDim(outid,'mon', 12);
daydimID    = netcdf.defDim(outid,'day', 31);% define variables 
station_id  = netcdf.defVar(outid,'stid','NC_FLOAT', numStatdimID);
lon_id  = netcdf.defVar(outid,'lon','NC_FLOAT', numStatdimID);
lat_id  = netcdf.defVar(outid,'lat','NC_FLOAT', numStatdimID);
alt_id  = netcdf.defVar(outid,'alt','NC_FLOAT', numStatdimID);
Prec_id = netcdf.defVar(outid,'Prec','NC_FLOAT',[daydimID, mondimID, yeardimID, numStatdimID]);netcdf.endDef(outid);% put variables into nc
netcdf.putVar(outid, station_id, Unqid);
netcdf.putVar(outid, lon_id, UnqLon/100);
netcdf.putVar(outid, lat_id, UnqLat/100);
netcdf.putVar(outid, alt_id, UnqAlt/100);
netcdf.putVar(outid, Prec_id, Precmmd);netcdf.reDef(outid);% put attribute into nc
netcdf.putAtt(outid, lon_id, 'longname', 'original station id');netcdf.putAtt(outid, lon_id, 'longname', 'longitude');
netcdf.putAtt(outid, lon_id, 'units', 'degrees_east');netcdf.putAtt(outid, lat_id, 'longname', 'latitude');
netcdf.putAtt(outid, lat_id, 'bounds', 'degrees_north');netcdf.putAtt(outid, alt_id, 'longname', 'height above sea level');
netcdf.putAtt(outid, alt_id, 'units', 'm');netcdf.putAtt(outid, Prec_id, 'longname', 'daily rainfall');
netcdf.putAtt(outid, Prec_id, 'units', 'mm/day');
netcdf.putAtt(outid, Prec_id, '_FillValue', single(-999));
netcdf.putAtt(outid, Prec_id, 'missing_value', single(-999));% define global attribution
netcdf.putAtt(outid, netcdf.getConstant('NC_GLOBAL'), 'Title', 'Station daily rainfall data');
netcdf.putAtt(outid, netcdf.getConstant('NC_GLOBAL'), 'Data Period', '1951-2018');
netcdf.putAtt(outid, netcdf.getConstant('NC_GLOBAL'), 'Author', 'Dayang Wang, SYSU, Email : wangdy58@mail2.sysu.edu.cn');
netcdf.putAtt(outid, netcdf.getConstant('NC_GLOBAL'), 'History', ['created on: ',datestr(now)]);netcdf.close(outid);toc