WaterNASA balances water budget with new estimates of liquid assets
Many pressing questions about Earth’s climate revolve around water. With droughts and flooding an ongoing concern, people want to know how much water is on the move and where it is going. To help answer those questions, a new NASA study provides estimates for the global water cycle budget for the first decade of the twenty-first century, taking the pulse of the planet and setting a baseline for future comparisons.
Many pressing questions about Earth’s climate revolve around water. With droughts and flooding an ongoing concern, people want to know how much water is on the move and where it is going. To help answer those questions, a new NASA study provides estimates for the global water cycle budget for the first decade of the twenty-first century, taking the pulse of the planet and setting a baseline for future comparisons.
The water cycle is the catch-all phrase to describe the movement of water — in its different forms, for example, liquid, gas, and solid — around the planet. It includes freshwater used in households and for agriculture, so any changes to the patterns of where rain and snow occur due to the changing climate may have huge impacts for communities worldwide.
The study is a rigorous accounting of the movements of Earth’s water from 2000 to 2010, and the first to rely solely on satellite observations and data-integrating models. The new estimates were derived simultaneously with estimates for the amount of energy from the sun available to heat and move water. A hotter day outside means, for example, that more water evaporates from the soil, plants or the ocean, so putting a number on the amount of heat energy helps scientists put a number on the amount of water that lifts into the atmosphere and is then transported by winds around the world. Assessing these two major components of Earth’s climate system is the first step for evaluating how patterns of water and energy may be affected by climate change.
“To document change you need to understand what the current state is — really have a good, sound understanding and quantification of the current state. Then you can tease out changes in the future,” said lead author Matt Rodell, a hydrologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
The results, published July 7 online in the Journal of Climate, show that each year heat from the sun evaporates 107,841 cubic miles (449,500 cubic kilometers) of water from the world’s oceans. For reference, the Great Lakes in the United States hold about 5,446 cubic miles (22,700 cubic km) of water. On land, 16,938 cubic miles (70,600 cubic km) of water evaporates from soil and plants. The moisture collects as water vapor in the atmosphere, and winds blow it to other parts of the world where it condenses into clouds, rainfall and snowfall.
