change version from 8 to 9

Author: Andy Barrett

notebooks/SMAP/README.md

@@ -4,7 +4,7 @@
 
 This set of three tutorials demonstrates how to search for, download and plot SMAP data using `xarray` and how to make the SMAP data into a georeferenced dataset. 
 
-We use the [SMAP L3 Radiometer Global Daily 36 km EASE-Grid Soil Moisture, Version 8](https://nsidc.org/data/SPL3SMP/versions/9) data set as an example.
+We use the [SMAP L3 Radiometer Global Daily 36 km EASE-Grid Soil Moisture, Version 9](https://nsidc.org/data/SPL3SMP/versions/9) data set as an example.
 
 All notebooks are self contained, so there is no particular order to run them.  However, [working_with_smap_data_in_xarray](notebooks/SMAP/working_with_smap_in_xarray.ipynb) provides the most basic introduction.