使用 ncks 的 4D netcdf 变量的 Hyperslab答案

【问题标题】：Hyperslab of a 4D netcdf variable using ncks使用 ncks 的 4D netcdf 变量的 Hyperslab
【发布时间】：2019-01-25 14:30:48
【问题描述】：

我有一个很大的 netcdf 文件，我只需要其中的某些数据。因此，我想使用 ncks 创建这个 netcdf 文件的细分。 netcdf文件如下：

Source:
           F:\LECOB\Model\20091208_195356.nc
Format:
           64bit
Global Attributes:
           Model = 's26.bobshelf.20141113'
           Title = 'S-NWM_BiP'
Dimensions:
           ni_t = 682
           nj_t = 712
           nk_t = 29
           time = 1     (UNLIMITED)
           ni_w = 682
           nj_w = 712
           nk_w = 30
           ni_u = 681
           nj_u = 712
           nk_u = 29
           ni_v = 682
           nj_v = 711
           nk_v = 29
           ni_f = 681
           nj_f = 711
           nk_f = 29
Variables:
    time 
           Size:       1x1
           Dimensions: time
           Datatype:   double
           Attributes:
                       units         = 'seconds from 2009-dec-08 17:00:14'
                       long_name     = 'time'
                       standard_name = 'time'
                       time_origin   = '2009-dec-08 17:00:14'
                       calendar      = 'gregorian'
                       content       = 'T'
                       axis          = 'T'
                       associate     = 'undefined'
    ni_t 
           Size:       682x1
           Dimensions: ni_t
           Datatype:   single
           Attributes:
                       long_name     = 'x_grid_index'
                       standard_name = 'x_grid_index'
                       content       = 'X'
                       axis          = 'X'
    nj_t 
           Size:       712x1
           Dimensions: nj_t
           Datatype:   single
           Attributes:
                       long_name     = 'y_grid_index'
                       standard_name = 'y_grid_index'
                       content       = 'Y'
                       axis          = 'Y'
    nk_t 
           Size:       29x1
           Dimensions: nk_t
           Datatype:   single
           Attributes:
                       long_name     = 'z_grid_index'
                       standard_name = 'z_grid_index'
                       content       = 'Z'
                       axis          = 'Z'
                       positive      = 'up'
    ni_w 
           Size:       682x1
           Dimensions: ni_w
           Datatype:   single
           Attributes:
                       long_name     = 'x_grid_index_at_w_location'
                       standard_name = 'x_grid_index_at_w_location'
                       content       = 'X'
                       axis          = 'X'
    nj_w 
           Size:       712x1
           Dimensions: nj_w
           Datatype:   single
           Attributes:
                       long_name     = 'y_grid_index_at_w_location'
                       standard_name = 'y_grid_index_at_w_location'
                       content       = 'Y'
                       axis          = 'Y'
    nk_w 
           Size:       30x1
           Dimensions: nk_w
           Datatype:   single
           Attributes:
                       long_name     = 'z_grid_index_at_w_location'
                       standard_name = 'z_grid_index_at_w_location'
                       content       = 'Z'
                       axis          = 'Z'
                       positive      = 'up'
    ni_u 
           Size:       681x1
           Dimensions: ni_u
           Datatype:   single
           Attributes:
                       long_name     = 'x_grid_index_at_u_location'
                       standard_name = 'x_grid_index_at_u_location'
                       content       = 'X'
                       axis          = 'X'
    nj_u 
           Size:       712x1
           Dimensions: nj_u
           Datatype:   single
           Attributes:
                       long_name     = 'y_grid_index_at_u_location'
                       standard_name = 'y_grid_index_at_u_location'
                       content       = 'Y'
                       axis          = 'Y'
    nk_u 
           Size:       29x1
           Dimensions: nk_u
           Datatype:   single
           Attributes:
                       long_name     = 'z_grid_index_at_u_location'
                       standard_name = 'z_grid_index_at_u_location'
                       content       = 'Z'
                       axis          = 'Z'
                       positive      = 'up'
    ni_v 
           Size:       682x1
           Dimensions: ni_v
           Datatype:   single
           Attributes:
                       long_name     = 'x_grid_index_at_v_location'
                       standard_name = 'x_grid_index_at_v_location'
                       content       = 'X'
                       axis          = 'X'
    nj_v 
           Size:       711x1
           Dimensions: nj_v
           Datatype:   single
           Attributes:
                       long_name     = 'y_grid_index_at_v_location'
                       standard_name = 'y_grid_index_at_v_location'
                       content       = 'Y'
                       axis          = 'Y'
    nk_v 
           Size:       29x1
           Dimensions: nk_v
           Datatype:   single
           Attributes:
                       long_name     = 'z_grid_index_at_v_location'
                       standard_name = 'z_grid_index_at_v_location'
                       content       = 'Z'
                       axis          = 'Z'
                       positive      = 'up'
    ssh  
           Size:       682x712x1
           Dimensions: ni_t,nj_t,time
           Datatype:   single
           Attributes:
                       units         = 'm'
                       long_name     = 'sea surface height above geoid'
                       standard_name = 'sea_surface_height_above_geoid'
                       content       = 'TYX'
                       associate     = 'time latitude_t longitude_t'
                       coordinates   = 'time latitude_t longitude_t'
                       _FillValue    = -9999
    CFL2D
           Size:       682x712x1
           Dimensions: ni_t,nj_t,time
           Datatype:   single
           Attributes:
                       units         = 's'
                       long_name     = 'CFL2D'
                       standard_name = 'CFL2D'
                       content       = 'TYX'
                       associate     = 'time latitude_t longitude_t'
                       coordinates   = 'time latitude_t longitude_t'
                       _FillValue    = -9999
    tem  
           Size:       682x712x29x1
           Dimensions: ni_t,nj_t,nk_t,time
           Datatype:   single
           Attributes:
                       units         = 'degrees_Celsius'
                       long_name     = 'sea_water_potential_temperature'
                       standard_name = 'sea_water_potential_temperature'
                       content       = 'TZYX'
                       associate     = 'time depth_t latitude_t longitude_t'
                       coordinates   = 'time depth_t latitude_t longitude_t'
                       _FillValue    = -9999
                       positive      = 'up'
    sal  
           Size:       682x712x29x1
           Dimensions: ni_t,nj_t,nk_t,time
           Datatype:   single
           Attributes:
                       units         = '1e-3'
                       long_name     = 'sea water salinity'
                       standard_name = 'sea_water_salinity'
                       content       = 'TZYX'
                       associate     = 'time depth_t latitude_t longitude_t'
                       coordinates   = 'time depth_t latitude_t longitude_t'
                       _FillValue    = -9999
                       positive      = 'up'
    vel_u
           Size:       681x712x29x1
           Dimensions: ni_u,nj_u,nk_u,time
           Datatype:   single
           Attributes:
                       units         = 'm s-1'
                       long_name     = 'sea_water_x_velocity_at_u_location'
                       standard_name = 'sea_water_x_velocity_at_u_location'
                       content       = 'TZYX'
                       associate     = 'time depth_u latitude_u longitude_u'
                       coordinates   = 'time depth_u latitude_u longitude_u'
                       _FillValue    = -9999
                       positive      = 'up'
    vel_v
           Size:       682x711x29x1
           Dimensions: ni_v,nj_v,nk_v,time
           Datatype:   single
           Attributes:
                       units         = 'm s-1'
                       long_name     = 'sea_water_y_velocity_at_v_location'
                       standard_name = 'sea_water_y_velocity_at_v_location'
                       content       = 'TZYX'
                       associate     = 'time depth_v latitude_v longitude_v'
                       coordinates   = 'time depth_v latitude_v longitude_v'
                       _FillValue    = -9999
                       positive      = 'up'
    kh   
           Size:       682x712x30x1
           Dimensions: ni_w,nj_w,nk_w,time
           Datatype:   single
           Attributes:
                       units         = 'm2/s'
                       long_name     = 'kh'
                       standard_name = 'kh'
                       content       = 'TZYX'
                       associate     = 'time depth_w latitude_t longitude_t'
                       coordinates   = 'time depth_w latitude_t longitude_t'
                       _FillValue    = -9999
                       positive      = 'up'
    tken 
           Size:       682x712x30x1
           Dimensions: ni_w,nj_w,nk_w,time
           Datatype:   single
           Attributes:
                       units         = '(m/s)2'
                       long_name     = 'tken'
                       standard_name = 'tken'
                       content       = 'TZYX'
                       associate     = 'time depth_w latitude_t longitude_t'
                       coordinates   = 'time depth_w latitude_t longitude_t'
                       _FillValue    = -9999
                       positive      = 'up'
    w    
           Size:       682x712x30x1
           Dimensions: ni_w,nj_w,nk_w,time
           Datatype:   single
           Attributes:
                       units         = 'm s-1'
                       long_name     = 'vertical_sea_water_velocity_at_w_location'
                       standard_name = 'vertical_sea_water_velocity_at_w_location'
                       content       = 'TZYX'
                       associate     = 'time depth_w latitude_t longitude_t'
                       coordinates   = 'time depth_w latitude_t longitude_t'
                       _FillValue    = -9999
                       positive      = 'up'

现在我对 4D 变量 vel_u (ni_u,nj_u,nk_u,time) 感兴趣。我想提取 ni_u 151 到 152、nj_u 234 到 235、nk_u 一切和 time 一切。这个问题帮助了我NCO: Extract a variable from NetCDF file using NCO ncks，以下链接http://nco.sourceforge.net/nco.html#crd也是如此使用这些，我在我的 linux 计算机上尝试了以下代码：

ncks -C -F -d vel_u,151,152,1 20091208_195356.nc test.nc

这给了我两个问题：

它复制所有变量，而不仅仅是 vel_u，即使我使用了 -C，正如问题 NCO: Extract a variable from NetCDF file using NCO ncks 中所建议的那样
我不知道如何指定仅使用 234 到 235 的维度 nj_u

那么如何将vel_u 变量的这些部分（ni_u 151 到 152、nj_u 234 到 235 ）放在我的 test.nc 文件中？

任何答案都非常感谢！

【问题讨论】：

标签： netcdf ncks

【解决方案1】：

我想我找到了答案：-d 用于维度，-v 用于变量，因此我的问题的答案如下：

ncks -C -F -d nj_u,234,235,1 -d ni_u,151,152,1 -v vel_u 20091208_195356.nc test.nc

-C 确保您只复制变量 vel_u

-F 因为计算应该从 1 而不是 0 开始

-d NameDimension,Min,Max,Step

-vNameVariable

输入.nc

输出.nc

这似乎正是我想要的。

【讨论】：