The growing importance of oceanic moisture sources for continental precipitation

Luis Gimeno,Raquel Nieto,Rogert Sorí

doi:10.1038/s41612-020-00133-y

Abstract

The precipitation that falls on the continents defines the extent and nature of terrestrial ecosystems and human activity in them, all of which are adapted to and maintained by present-day precipitation. In essence, precipitation is supplied by moisture that either comes directly from the ocean, or is subsequently recycled from the continents themselves. Both the processes that control evaporation and the main mechanisms of moisture transport clearly differ between the ocean and the continent, thus within the context of a changing climate, it may be expected that the relationship between precipitation of oceanic and terrestrial origin varies globally and regionally, as will the influence of these two basic components of total precipitation on global and regional precipitation trends, especially in tropical regions. We describe an approach based on a Lagrangian technique for estimating the precipitation in a target region given the proportions of moisture transported from the two sources (ocean and continent) to reveal that the percentage of precipitation of oceanic origin has increased globally in the current climate (1980–2016). The greatest observed rate of increase is in the tropical regions; furthermore, the trends of precipitation in these regions are controlled by trends in precipitation for which the source of moisture is the ocean.

Highlights

IntroductionLong data sets of more than a century, which would allow us to control for the effects of low-frequency climate oscillation, tend to be incomplete for large continental areas, and this limits the extent of the possible analysis
One of the points of greatest uncertainty in ongoing investigations of climate change is the determination of whether global precipitation over the continents has changed with global warming, together with the regional patterns of any changes[1].Long data sets of more than a century, which would allow us to control for the effects of low-frequency climate oscillation, tend to be incomplete for large continental areas, and this limits the extent of the possible analysis
These results are in line with the intensification of the hydrological cycle with global warming, and with the support of thermodynamic considerations, this leads to an increase in moisture transport from the main sources, where evaporation exceeds precipitation and which are generally located over the oceans, towards the main sinks, where precipitation exceeds evaporation and which are largely located over the continents

Summary

Introduction

Long data sets of more than a century, which would allow us to control for the effects of low-frequency climate oscillation, tend to be incomplete for large continental areas, and this limits the extent of the possible analysis. From the conclusions of the last IPCC report[1] and since 1950, which includes the post-satellite period, there is a moderate level of confidence in the precipitation changes averaged over global land areas, with precipitation products showing significant negative trends in some cases and not in others. To improve confidence in these estimated precipitation trends, it is useful to examine the coherence of these changes with those seen in other components of the hydrological cycle directly related to precipitation[4], and for which these changes have a physical interpretation linked to increased temperature[5]. Moisture transport and changes in the source-sink relationship[6,7] can play a very important role here, which at a large scale allows the analysis of variations in the relative importance of oceanic sources versus terrestrial sources in continental precipitation[8,9]

Methods

Results

Conclusion