Frequently Asked Questions Get answers to some of the more frequently asked questions about the GPM and TRMM missions and precipitation measurement in general. Image Gallery Photos and illustrations from GPM, TRMM, and the Ground Validation missions. Video Gallery Videos and animations from GPM, TRMM, and the Ground Validation missions. Documents View the PMM document repository, in which you can download scientific papers and other documents from GPM, TRMM, and the Ground Validation missions. GPM Refereed Publications TRMM Refereed Publications Lists of published research articles from the

Water is fundamental to life on Earth, affecting the behavior of the weather, climate, energy and ecological systems as water moves through the Earth’s water cycle as vapor, liquid and ice. Precipitation, a key component of the water cycle, is difficult to measure since rain and snow vary greatly in both space and time. Obtaining reliable ground-based measurements of rain and snow often presents a formidable challenge due to large gaps between reliable instruments over land and, particularly, over the oceans. From the vantage point of space, satellites provide more frequent and accurate observations and measurements of rain and snow around the globe. This allows key insights into when, where and how much it rains or snows globally, supplying vital information to unravel the complex roles water plays in Earth systems.

Precipitation data from the GPM and TRMM missions are made available free to the public in a variety of formats from several sources at NASA Goddard Space Flight Center. This section outlines the different types of data available, the levels of processing, the sources to download the data, and some helpful tips for utilizing precipitation data in your research.