BAMS Cover: Mapping Global Precipitation

Satellite observations are the main source of rain and snowfall measurements across the Earth’s surface. The general class of satellite sensors known as passive microwave radiometers are able to capture the distribution and intensity of precipitation (rain or snow) in all parts of the globe, including over the oceans and sparsely populated regions that do not have any rain gauges or weather radar data. These measurements are crucial for monitoring the availability of our freshwater, not only for domestic use, but for industry and agriculture. Monitoring the distribution and amount of precipitation over time is also important for studying the impact of climate change on freshwater and the implications this has on the natural world around us. The development of satellite systems to provide these observations has grown over the last 45 years and currently comprises of about 10-12 sensors which contribute to the Global Precipitation Measurement mission, jointly led by NASA and the Japanese Aerospace Exploration Agency (JAXA). Since precipitation changes rapidly over time it is necessary to observe it frequently enough to capture the variations in intensity and distribution. The current constellation provides observations every three hours (or less) about 90% of the time, which is considered sufficient for many purposes. However, this interval can only be maintained if new satellite missions are launched in a timely fashion to replace the older satellites that are now beyond their mission lifetimes. In other cases, observations are provided by sensors not designed for the retrieval of precipitation, and the global estimates would improve if these were replaced by sensors designed with precipitation as an intended observation. The article in this journal showcases current precipitation capabilities, and examines the future prospects for the estimate of precipitation from satellite systems.