One of the best discoveries during my two years as a PhD student has been the International Research Institute for climate and society (IRI)’s Data Library.
While overwhelming at first, once you get the hang of what to look for and how to look for it, it is a great data source that seems rather undiscovered among the environment/climate researchers I’ve been talking to.
It provides a large database of free (gridded) data from many different sources. The ones I have used more frequently are MODIS NDVI and EVI, GIMMS NDVI, CRU and GPCC climate data, but that’s just a small fraction of what’s available.
So what makes this different from downloading the data from its original source? Because you can process the data before you download it, for example avoiding having to download global data when you’re only interested in a small area. It get’s better, you can also do calculations in the DL’s expert mode before you download the data, allowing you to calculate for example yearly average NDVI values, or precipitation anomalies. This requires some knowledge about the INGRID functions, but once you learn it, it’s very useful.