python-data/exercises/ex03b_xr_masking.ipynb

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    "# Exercise 3b: Masking"
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    "## Aim: Learn to mask data in xarray"
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    "Find the teaching material here: https://tutorial.xarray.dev/intermediate/indexing/boolean-masking-indexing.html"
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    "### Issues covered: \n",
    "- Create re-usable masks for data\n",
    "- Plot masked data"
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    "Q1. For masking, we're back to using our ocean dataset. Load it now from `../data/vbhubo.pgc0apr.nc`."
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    "Q2. Determine which grid cells sea surface temperaturevis more than the mean."
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    "Q3. Combine this with another .where() lookup to show only cells where the temperature is more than the mean and salinity is more than the mean."
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    "Q4. Masks are just boolean arrays. Create a re-usuable mask for the temperature and sst criteia above, and a combined one."
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    "Q5. Use this mask to make the same temperature plot, and a similar one for sst."
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