Over the northern Atlantic Ocean, clouds that often produce heavy rain
storms grew taller and were more frequent when plumes of pollution from
North America or dust from Africa's Sahara Desert were present.

However, when smoke from large fires billowed into the sky over South
America's Amazon River basin, clouds were consistently fewer than when
the air was relatively clear.

Aerosols sometimes stop clouds from forming and in other cases increase
cloud cover. Clouds deliver water around the globe and they also help
regulate how much of the sun's warmth the planet holds.

The capacity of air pollution to absorb energy from the sun is the key.

Separating the real effects of the aerosols from the coincidental
effect of the meteorology was a hard problem to solve. In addition, the
impact of aerosols is difficult to observe because aerosols only stay
airborne for about one week

Observations suggest it is the darkness or brightness of aerosol
pollution and not weather factors that cause pollution to act as a
cloud killer or a cloud maker.

http://www.nasa.gov/vision/earth/env...on_clouds.html

Humm but the Saharan Air layer is usually real dry, so even if the dust
would act as a water seeking aerosol, the air would be to dry....



"Weatherlawyer" wrote in message
ps.com...
Over the northern Atlantic Ocean, clouds that often produce heavy rain
storms grew taller and were more frequent when plumes of pollution from
North America or dust from Africa's Sahara Desert were present.

However, when smoke from large fires billowed into the sky over South
America's Amazon River basin, clouds were consistently fewer than when
the air was relatively clear.

Aerosols sometimes stop clouds from forming and in other cases increase
cloud cover. Clouds deliver water around the globe and they also help
regulate how much of the sun's warmth the planet holds.

The capacity of air pollution to absorb energy from the sun is the key.

Separating the real effects of the aerosols from the coincidental
effect of the meteorology was a hard problem to solve. In addition, the
impact of aerosols is difficult to observe because aerosols only stay
airborne for about one week

Observations suggest it is the darkness or brightness of aerosol
pollution and not weather factors that cause pollution to act as a
cloud killer or a cloud maker.

http://www.nasa.gov/vision/earth/env...on_clouds.html

Weatherlawyer wrote:
wxguru wrote:

Humm but the Saharan Air layer is usually real dry, so even if the dust
would act as a water seeking aerosol, the air would be to dry....

Doesn't an Hadley cell cross the Sahara? There is a difference between
condensation and water content.

There was something on this that I was just reading from the
EarthObservatory:

NASA SATELLITES FIND BALANCE IN SOUTH AMERICA'S WATER CYCLE

For the first time, NASA scientists using space-based measurements have
directly monitored and measured the complete cycle of water movement
for an entire continent.

Using satellite data from QuikScat, GRACE and TRMM a science team at
NASA's Jet Propulsion Laboratory, Pasadena, Calif., directly observed
the seasonal cycling of water into and out of South America. They
confirmed that the amount of water as rain or snow flowing into the
continent from the marine atmosphere is in balance with the estimated
amount of water returned to the ocean by the continent's rivers.

There had been no direct way to monitor continental water balance.
Scientists estimated the balance through regional ground-based
measurements and computer models. We'll have greater understanding of
floods and drought, surface and ground water quality, and the
availability of freshwater resources for agriculture and ecosystems.

A statistical method was developed to estimate water transport using
QuikScat's surface wind data and atmospheric water vapor data from
microwave radiometers. Rainfall data from NASA's TRMM were used to
measure the rainfall over the continent. Water going out from the
continent was measured by combining data from river flow gauges with
projections from models that predict the amount of water discharged at
the rivers' mouths.

The river discharge rates were collected over periods ranging from a
few years to a century, depending on the river basin and locality, and
were averaged to determine an annual cycle. Scientists compared that
estimate with the monthly changes in South America's mass over two
annual cycles, from August 2002 to July 2004, as measured by GRACE.
They determined that the seasonal mass change is dominated by changes
in the amount of surface and underground water.

Liu said the large-scale geographic patterns of rainfall and mass
change rates follow an apparent counterclockwise annual march over the
northern half of South America. With relatively small amounts of
evaporation, and small or slow surface water outflow, the mass change
over a certain region is primarily driven by rainfall.

The team found the annual variation of rainfall in the Amazon and La
Plata basins correlates closely with the GRACE measurements of their
mass change. In addition, measurements of the flow of moisture across
relevant segments of the continent's Pacific and Atlantic coasts were
found to correspond with measurements of the annual cycle of rainfall
in the two basins and the Andes Mountains.

Planned reprocessing of QuikScat, GRACE and TRMM data to improve the
data quality and resolution, combined with data from planned future
missions, promises to further enhance our understanding of water
balance on a global basis. Those planned future missions include NASA's
Global Precipitation Measurement Mission, the European Space Agency's
Soil Moisture and Salinity Sensor and NASA's Aquarius satellite.

GRACE tracks changes in Earth's gravity field, primarily caused by the
movement of water.

QuikScat measures ocean surface winds by transmitting high-frequency
microwave pulses to Earth's ocean surface and measuring the strength of
the pulses that bounce back.

TRMM studies tropical rainfall.

http://earthobservatory.nasa.gov/New...070522669.html

It would seem that the way that these things are going, that the
veracity of the research can be checked. When the forest is cut down
the trees are burned and produce one kid of aerosol.

When the forest is in good health, the pollens and etc., produced are
another kind. Their effects can be assesed.

Then there is the stuff from the prarie farming that the corrupt
politicians and whoever, plant after the illegal logging and dust from
when the rains fail and the land turns to desert.