Satellite Data Shows Increase in Tropical Rainfall
Using data provided by satellite and ground-based systems from 1979 through the present, scientists have discovered that the wettest years in the tropics were after 2001. The rainiest year was 2005, followed by 2004, 1998, 2003 and 2002.Overall rainfall across the entire globe has not changed very much, but the tropics, which receive almost two-thirds of the total, saw an increase of five percent. Most of the increase occurred over tropical oceans with a small decrease over land areas. A warming global climate is considered the most likely explanation for this increase, as warming temperatures would increase the rate at which water is evaporated from the Earth’s surface and recycled as rain and snow.
The advent of satellite technology has made possible the estimates of rainfall over oceans to supplement the traditional land-based measurements of rain gauges. Satellite and land-based data have been combined into the Global Precipitation Climatology Project sponsored by the World Climate Research Program. NASA scientists provide the project’s monthly rainfall updates that are available to be used by scientists all over the world.
Initially, the slight increase in tropical rainfall was not necessarily seen as something other than natural variability, and it was not until researchers decided to remove effects of El Nino-Southern Oscillation and major volcanic eruptions which can change rainfall amounts. El Nino is a warming of tropical waters in the central and eastern Pacific about every three to seven years which affects weather patterns around the globe. During the El Nino years, the total amount of rainfall over the tropics changed little, but more rain fell over the oceans
Volcanic eruptions eject particles into the stratosphere and upper troposphere which hinder the formation of rain by forming more small cloud drops and keeping some of the sun’s energy from reaching the Earth. With less energy reaching the surface of the Earth, the temperature is lowered, the rate of evaporation is slowed, and less rainfall is produced. Over the twenty-seven- year period two major volcanic eruptions, El Chicon in Mexico and Mount Pinatubo in the Philippines occurred, and, in the two years following the eruptions total tropical rainfall decreased by about five percent.
With the effects of El Nino and the volcanic eruptions eliminated from the rainfall record the long-term trend of increased tropical rainfall appeared more clearly in data obtained over both the land and sea. As more information is received, the trend is continuing with 2006 appearing to be another record year for rainfall in the tropics, tying 2005 as the period’s rainiest year.
This entry was posted on Friday, August 31st, 2007 at 6:51 am and is filed under Mars News, Public Relations. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
