Huffman: The monsoon is a seasonal wind and rain pattern that was first described
over south Asia. You see the clouds
blossoming here during the summer part of the monsoon.
For centuries people have known about it, but only recently have we received
enough data from satellites to really describe what's going on.
Skofronick-Jackson: What you can see here is moist air that has evaporated from the ocean,
coming across India and providing rainfall, driving the monsoon
season. The great thing about GPM is that it allows us
to see precipitating systems as a whole, over land and
oceans, and then as they transition from one boundary to the next.
Huffman: All this rainfall drives soil moisture over land. It's
beneficial because it promotes the economic activity that people depend on,
for example, agriculture. As well it fills the rivers,
which provides water for human activity and the natural environment, as well as
transportation. If the rivers get too full,
of course, it becomes flooding. At first the floods you see here are fairly
minor and broad-scale but then they concentrate in the few wiggly lines
which are the river basins, for example, in central eastern China.
Skofronick-Jackson: In mountainous regions
when the ground becomes saturated due to heavy rains it can lead to
landslides. Landslides kill thousands of
people every year and are primarily triggered by rainfall. They
are especially common in the Himalayan region each monsoon season.
Huffman: One really cool way to look at the monsoon
is to do a split-screen and look at the summer and the winter at the same time.
In the summer the wind is blowing onshore, bringing
the moist rain-laden air into the continent. In the
winter time, it blows off the continent. Skofronick-Jackson: Now those winds are
basically driven by temperature differences between the ocean and the land.
And where the land is nice and warm, the air expands and it draws
in the moist precipitation from the ocean waters, but in the winter
time, it's very cold and you can see that the moisture then it goes
from the continent back into the oceans. Over the past fifty
years or so, satellites have been used to measure precipitation all around
our Earth. With that dataset we're able to understand
that monsoons occur not only in south Asia and India,
but in other parts of the world as well. Huffman: For example, Africa, where the
temperature gradient is between the Atlantic Ocean and the Sahara Desert, the
wind blows from the moist Atlantic Ocean onto west Africa
providing the moisture for the precipitation. Some of these westward
moving storms provoke hurricanes over the Atlantic that occasionally make it to
the U.S. Southwestern North America also has a summertime
monsoon. You see high soil moisture in regions where there's a lot
of precipitation in western Mexico, and later in the season this extends up
into the southwestern U.S. And the Southern Hemisphere has
a monsoon as well. This occurs in the Northern Hemisphere winter,
which is the Southern Hemisphere summer when Australia is warmer
than the ocean to the north. Skofronick-Jackson: Having a better
understanding of the global water cycle and monitoring changes over time
is important for society, for our everyday lives
and our long-term future.