PRECIPITATION MEASUREMENT MISSIONS

Earth’s climate is changing. The accumulation of greenhouse gases has affected the oceans and ice systems as well as the atmosphere, which in turn impact the water cycle. According to the 2007 Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Synthesis Report of current research, frequency of heavy precipitation and precipitation at high latitudes of the Arctic and Antarctic will very likely increase, tropical cyclone intensity will likely increase, and precipitation over subtropical arid land regions will likely decrease.

To make such climate predictions, scientists use sophisticated computer models that try to recreate Earth’s climate conditions. Understanding current rainfall and snowfall variability, among other climate factors on regional and global scales, helps scientists model future behavior of precipitation patterns and climate.

But for a system as complicated as the Earth, the models are only as good as the data provided. Space-borne precipitation measurements from satellites like TRMM and GPM provide global scale observational data sets that are comprehensive and consistent over long time periods, two characteristics scientists need to understand the relationships between different parts of the climate system. The ultimate goal is to be able to predict changes in climate on time scales as short as the next hurricane season and as far into the future as changes that may occur in the coming decades or centuries.

Figure from the IPCC AR4 Synthesis Report showing relative changes in precipitation (in percent) for the period 2090-2099, relative to 1980-1999. Values are multi-model averages based on the SRES A1B scenario for December to February (left) and June to August (right). White areas are where less than 66% of the models agree in the sign of the change and stippled areas are where more than 90% of the models agree in the sign of the change.

Source: IPCC AR4 Synthesis Report, WG1, Figure 10.9, Summary for Policy Makers;
http://www.ipcc.ch/publications_and_data/ar4/syr/en/figure-3-3.html