From Sea Salt to Rainfall

Above: Surfacing Basic Elements — Hong Xu, PhD

Our collaboration will attempt to show that ocean properties can help predict rainfall on land.

The key concept will evolve around the following components:

The ocean is the ultimate water source on our planet. What goes up due to evaporation from the ocean surface will come down somewhere else. The more water evaporates, the saltier the imprint seen at the ocean’s surface that is left behind. This allows us to recognize ocean areas where a lot of water is exported from as having a higher surface salt content. Changes in the global water cycle are also reflected in changing salt content seen in the surface ocean around the world.

One of the physical properties of the ocean is its salt content but few people are aware that water from different ocean regions varies in its physical properties. Salt is one of these elements, yet it does vary from time to time and location to location. The seemingly “inconsequential” variation of the regional ocean salt content (salinity) is an indication of the movement of moisture from the ocean’s surface. This way, tracking the ocean’s salt content globally from satellites may help predict rainfall events on land several months in advance.

The signature of salinity at the ocean surface can be measured from space with satellites. The salt content at the sea surface may change over time as a result of more or less evaporation and moisture export. Prior to major flood events on land, an unusual salinity signature can be detected from satellites – and used for predicting rainfall on land. Caroline, her team and other scientists have explored unusual ocean salinity signals and subsequently used that property to successfully predict rainfall and extreme events, such as droughts and floods in Australia, the African Sahel, and across cropping regions in the Midwest US.

The benefits to people across all ranges of lives and industries are immense. Farmers may benefit directly from the knowledge of ocean salt (salinity) changes to optimize their decisions of crop planting. Food industry from processing to restaurant business can better plan their choices, timing and budget. Moreover, having a better prediction of drought/rainfall severity months ahead could help disaster relief organizations and their efforts of resource distribution.