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Home / Science / Daily rainfall over Sumatra is associated with larger atmospheric phenomena

Daily rainfall over Sumatra is associated with larger atmospheric phenomena



  Daily rainfall over Sumatra in conjunction with a larger atmospheric phenomenon
Rain and clouds in Indonesia. Picture credits: Pixel PlaceboCC BY-NC 2.0

Around the globe, communities are dealing with rain and storms. An area known as the "maritime continent", which includes major islands such as Sumatra, Java, Borneo, Papua New Guinea, and a galaxy of smaller islands, has significant rainfall, including monsoon rains and flash floods.

In a new study conducted by atmospheric scientist Giuseppe Torri at the University of Hawaii (UH) at the Mānoa School of Ocean and Earth Science and Technology (SOEST), researchers uncovered details of the relationship between a larger atmospheric phenomenon called "Phenomenon" The Madden-Julian Oscillation (MJO) and the daily patterns of precipitation on the sea continent.

The MJO orbits the globe around the tropics and can affect the weather on weekly to monthly timescales, alternating between cloudy, rainy and sunny, drier periods.

Torri and co-authors found that the impact of the MJO on Sumatra's daily rainfall patterns was quite significant. When the MJO was active near the lake continent, there was more water vapor ̵

1; and therefore greater potential for significant rainfall events – and more variations in water vapor throughout the day than in the suppressed phase. During the active phase of the MJO, clouds and rain seemed to move faster off the coast at night.

The team relied on data from a network of GPS stations installed on Sumatra and on the neighboring islands by a team of scientists interested in monitoring tectonic activity along the west coast of Sumatra. As it turns out, the GPS signal is distorted by the amount of water vapor in the atmosphere. This distortion is bad news for people interested in location information – for which GPS technology was invented. However, scientists including UH Mānoa, professor of Atmospheric Science Steven Businger, found that the distortion can tell something about the state of the atmosphere, and pioneered its use as a data source.

  Daily rainfall over Sumatra in conjunction with a larger atmospheric phenomenon
Clouds over an Indonesian field. Picture credits: Wilson Loo CC BY-NC-ND 2.0

With comprehensive coverage of GPS stations on the island of Sumatra, the team had a dataset that provided a very detailed picture of the daily atmospheric changes.

"Given the existing scientific literature, we felt that the MJO had an impact on local convection on the sea continent," Torri said. "One thing that surprised me was how well we were able to see the late-evening convection spread out offshore, thanks to the density of GPS network stations that we considered."

The MJO is arguably one of the most important phenomena on the planet and can affect the weather and climate of regions even thousands of miles away from the sea continent. A better understanding of the MJO and a good way to simulate it are the keys to a better understanding of our current and future climate.

While the current study promotes understanding of the impact of the MJO on clouds and rain over Sumatra, Torri will work with SOEST atmospheric researcher Alison Nugent to investigate the causes of these effects and the mechanisms that drive the spread of rain to high altitudes Lake control.


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Further information:
Giuseppe Torri et al., On the Day Cycle of GPS-Derived Water Vapor Over Sumatra, Journal of the Atmospheric Sciences (2019). DOI: 10.1175 / JAS-D-19-0094.1

Provided by
University of Hawaii in Manoa




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Daily rainfall over Sumatra in combination with a larger atmospheric phenomenon (2019, 20 September)
retrieved on September 20, 2019
from https://phys.org/news/2019-09-daily-rainfall-sumatra-linked-larger.html

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