Vertical methods

Built-in methods for handling files with multiple vertical levels — fixed z-levels or terrain-following coordinates alike.

Illustrated below using depth-resolved ocean temperature from NOAA's World Ocean Atlas for January, down to 1500 metres across 57 vertical levels.

Vertical statistics

Vertical means account for cell thickness where it's available — you must specify fixed, telling NCToolkit whether the vertical levels are consistent across space:

python

ds = nc.open_thredds("https://www.ncei.noaa.gov/thredds/dodsC/ncei/woa/temperature/decav/1.00/woa18_decav_t00_01.nc")
ds.vertical_mean(fixed=True)
ds.plot()

ds.plot() — interactive output Open interactive

Depth-averaged mean ocean temperature

vertical_max and vertical_min work the same way:

python

ds = nc.open_thredds("https://www.ncei.noaa.gov/thredds/dodsC/ncei/woa/temperature/decav/1.00/woa18_decav_t00_01.nc")
ds.vertical_max()
ds.plot()

ds.plot() — interactive output Open interactive

Vertical maximum ocean temperature

python

ds = nc.open_thredds("https://www.ncei.noaa.gov/thredds/dodsC/ncei/woa/temperature/decav/1.00/woa18_decav_t00_01.nc")
ds.vertical_min()
ds.plot()

ds.plot() — interactive output Open interactive

Vertical minimum ocean temperature

Vertical interpolation

vertical_interp interpolates to specific target levels — here, to a single depth of 1000m:

python

ds = nc.open_thredds("https://www.ncei.noaa.gov/thredds/dodsC/ncei/woa/temperature/decav/1.00/woa18_decav_t00_01.nc")
ds.subset(timestep=0)
ds.vertical_interp(levels=[1000], fixed=True)
ds.plot()

ds.plot() — interactive output Open interactive

Ocean temperature interpolated to 1000m depth

Top & bottom levels

Select the surface vertical level directly with top:

python

ds = nc.open_thredds("https://www.ncei.noaa.gov/thredds/dodsC/ncei/woa/temperature/decav/1.00/woa18_decav_t00_01.nc")
ds.top()       # select the sea-surface
ds.plot()

ds.plot() — interactive output Open interactive

Sea-surface ocean temperature, selected with top()

bottom works the same way, selecting the sea-floor level instead:

python

ds = nc.open_thredds("https://www.ncei.noaa.gov/thredds/dodsC/ncei/woa/temperature/decav/1.00/woa18_decav_t00_01.nc")
ds.bottom()    # select the sea-floor

Additional vertical methods

For quick reference, every vertical method NCToolkit provides:

Method	Description
`ds.top()`	Extract the top/surface level.
`ds.bottom(...)`	Extract the bottom (deepest valid) level.
`ds.vertical_interp(...)`	Interpolate to specific target vertical levels.
`ds.vertical_mean(...)`	Depth-averaged mean, accounting for cell thickness where available.
`ds.vertical_min()`	Vertical minimum at each grid cell and time step.
`ds.vertical_max()`	Vertical maximum at each grid cell and time step.
`ds.vertical_range()`	Vertical range (max − min) at each grid cell and time step.
`ds.vertical_sum()`	Vertical sum at each grid cell and time step.
`ds.vertical_integration(...)`	Vertically integrated total, accounting for cell thickness.
`ds.vertical_cumsum()`	Cumulative sum with depth/height.
`ds.invert_levels()`	Reverse the order of the vertical levels.
`ds.bottom_mask()`	Mask identifying the deepest valid (non-missing) cell — e.g. the seabed.