Seamen have relied on the winds of the Indian Ocean since the days of Sinbad the Sailor. More recently, scientists have come to appreciate the impact these Indian Ocean winds have on weather occurring in the western hemisphere – on the opposite side of the globe from the Indian Ocean – through a weather phenomenon known as the Madden-Julian Oscillation (MJO).
Aerial view of Malé in the Maldives. The two dark lines are propeller wings.
Named after two scientists, this is a 40-60 day weather cycle that consists of a lot of rain over a large area, lasting for about three weeks, followed by a three-week period of calmer weather before transitioning back into heavier rains again.
This weather pattern occurs mostly at the equator, where the effects of Earth’s rotation do not influence weather systems. This happens because near the equator there is no jet stream, and therefore cold and warm weather fronts, like those experienced in the northern part of the US or in other mid-latitude regions, do not exist. This also makes weather at the equator difficult to model, because it is so different from what we experience in the mid-latitudes. Nevertheless, weather at the equator can affect weather in the US, for example by supplying moisture.
Addu Atoll lagoon at sunset
It’s difficult to model this type of weather pattern well, particularly how it begins. The Indian Ocean is known as a ‘genesis’ or ‘birth’ region for the MJO. A large field experiment, called DYNAMO (Dynamics of the MJO), is now underway in the Indian Ocean to study how large regions of rain can develop at the equator, and to use that information to improve weather models. Hundreds of scientists are stationed on islands and research ships. They are equipped with radars and other instruments all across the ocean in an effort to study how a peaceful, warm ocean and calm skies can turn into one of the wettest places on Earth, seemingly overnight. The field experiment, which began on October 1 is being led by Professor Chidong Zhang and includes many scientists and students from RSMAS.
Group photo of RSMAS faculty at the DYNAMO opening ceremony on Gan Island. From left to right: Chidong Zhang, Paquita Zuidema, David Zermeno, Brian Mapes
Photos taken in October, at the start of the research experiment, show the beautiful drier tropical days as the atmosphere is building up moisture. These photos were taken on Addu Atoll in the Maldives, which is located within a degree of the equator. This beautiful atoll encircles a lagoon, and is many miles long but only several blocks wide even at its widest.
DYNAMO will continue well into 2012. You can learn more about the MJO from the Australian weather bureau and follow the weekly weather discussions.
–UM Associate Professor, Dr. Paquita Zuidema