I can't say anything specific, since your comment has very little detail about where and when you are working. One thing that will be universal when considering reanalysis precipitation is that the quantity is derived from the background model forecast of the assimilation process. So, while the environment that produces precipitation is affected by the observational analysis, precipitation relies on the model physics, and has significant uncertainty. If observations of precipitation are available, you'll want to use those, at the least, in a comparison with the reanalysis data. Some reanalyses produce 1 hourly data, and some assimilate rainfall (see the North American Regional Reanalysis). Biases and uncertainty in reanalysis precipitation depends greatly on where and when you are looking. The papers listed in the pages Gil provided are a start, but be sure to follow those that they cite as well.
Re: Rainfall analysis
I can't say anything specific, since your comment has very little detail about where and when you are working. One thing that will be universal when considering reanalysis precipitation is that the quantity is derived from the background model forecast of the assimilation process. So, while the environment that produces precipitation is affected by the observational analysis, precipitation relies on the model physics, and has significant uncertainty. If observations of precipitation are available, you'll want to use those, at the least, in a comparison with the reanalysis data. Some reanalyses produce 1 hourly data, and some assimilate rainfall (see the North American Regional Reanalysis). Biases and uncertainty in reanalysis precipitation depends greatly on where and when you are looking. The papers listed in the pages Gil provided are a start, but be sure to follow those that they cite as well.