UCSB geography researchers have published
a study that presents a link between
warming temperatures over the Indian Ocean
and projections of decreased precipitation in
East Africa.

The study, published online in the journal
Climate Dynamics, used principal component
analysis, or PCA, to measure precipitation
levels, wind velocity, vertical velocity and
air temperatures in East Africa and over
the Indo-Pacific warm pool. Chris Funk,
a professor of geography at UCSB, and his
postdoctoral research associate Park Williams
found that the warm pool, or the area where
the Indian and Pacific Oceans meet, has
been expanding due to global warming.
This expansion has moved westward and
is affecting the precipitation levels of East
Africa more than El Niño, the weather
phenomenon.

“For the area between the Pacific and
Indian Oceans, the more dominant [weather]
process has been the warming process, not
El Niño,” Williams said. “It’s really big news
because El Niño has always been the driving
force behind weather patterns.”

The area is under the path of Walker
circulation. As warm, humid air coming off
the warm pool rises and causes heavy rains
over the Indian Ocean, the dry air left after
the heavy rains then moves eastward and
westward into the central/western part of the
Indian Ocean and the eastern Pacific, where
it sinks and moves back toward the warm
pool to repeat the cycle.

In their research, Funk and Williams have
found that the Walker circulation is being
altered by warming global temperatures. As
the surface temperature of the warm pool
increases, it has expanded farther into the
central/western areas of the Indian Ocean.
This means that the cold, dry air that occurs
after rainfall is sinking farther west, over the
northern region of Africa. This causes a high
atmospheric pressure that causes air to escape
in a clockwise direction, blocking rainfall
coming off of the Indian Ocean and thus creating
dry conditions in Kenya and Ethiopia.
“The parts that are really facing changes
are mainly on the eastern plank of the
Ethiopian islands by the mountain range that
goes through Ethiopia south into Kenya. On
the eastern side of mountain range is where
we are seeing less rainfall,” Williams said.
“About a meter [of rain] falls during March
and June … and in the last 30 years it has
decreased in rainfall by about 30 percent,
with no evidence that it has bottomed out.”
“These climate processes are slow and
there are still occasionally wet and dry years,
so we looked at rainfall over a long period of
time and dry years are occurring more often
than they used to,” Williams said. “It’d take
another decade or so to tell whether or not
these dry years have ended.”

The research has received attention from
African governments due to fears of decreased
rainfall negatively affecting the economy and
agriculture of the countries in the area. Funk
is currently in the Kenyan capital of Nairobi
presenting his research to concerned officials.
The research is funded by USAID, a
government agency that provides economic
and humanitarian aid to foreign countries.
Williams said their research helps the agency
project how much money to set aside for
Africa for issues like famine.