WASHINGTON • A new study has revealed that the acrid haze that shrouded the region for months last year covered half the globe at the Equator, from East Africa to as far as the international dateline in the western Pacific Ocean.

The research data, published in the Proceedings Of The National Academy Of Sciences, was gathered by Nasa's Earth Observing System satellites, which have data records as far back as the early 2000s. It was combined with longer-term visibility records from airports.

The data gathered on the long-stretching plume, which originated from forest fires in Indonesia, exposed some important trends for fighting fire in the future, according to the National Geographic website.

Last year was an exceptionally dry year, driven by the El Nino phenomenon, and Indonesia's annual burning season to clear agricultural land was exacerbated by the dryness that lit up the country's extensive underground peat deposits.

However, the researchers discovered that little fire activity or pollution was evident when average dry-season precipitation was greater than 6mm per day. The less precipitation there was, the more fire activity there would be, up to a limit of 4mm per day, the team found when it studied a 15-year period that encompassed the two major fire seasons in 2006 and last year.

Below 4mm, pollution and fire activity would quickly go up, according to the study.

Climate scientist Robert Field, the study's lead author, said he hoped the trend that the study has discovered can help Indonesia stop the underground fires that worsen the haze.