Chapter 26
THE NASA EARTH SYSTEM SCIENCE
PROGRAM IN 21ST CENTURY
G. Asrar
NASA Headquarters, Washington D.C., USA.
1.
INTRODUCTION
The Earth is a dynamic system of land, oceans, and atmosphere that has
evolved as a result of the complex biological, chemical and physical
processes. These processes are interconnected by an intricate and fragile web
that helps modulate such things as weather, droughts and floods and can
ultimately have profound impacts on global food production, natural
resource management, commerce and the global economy. The recently
experienced 1997–98 El Niño cycle illustrates this complex interaction that
began when the normal state of the Pacific ocean was perturbed by a
weakening of the westerly trade winds; a state that is necessary to maintain a
“pool” of warm water within the western tropical Pacific. The weakening of
trade winds allowed warm water to flow eastward along the equator to
coastal Peru. The eastward-spreading water brought with it the associated
tropical rainfall. As the warm pool reached the coast of Peru, it spread to the
north and south progressively cutting off the nutrient-rich upwelling along
the Peruvian coast, and causing a collapse of the fishery and impacting the
seabird population. As the heat from the warm pool escaped into the
atmosphere it impacted global atmospheric circulation including the global
jet streams. This perturbed atmospheric state brought unusual weather
around the world, where normally wet regions such as Indonesia and
northern Australia, experienced drought and wildfires, and normally dry
regions, such as southern California, experienced floods and mudslides.
These changes, in turn, had a significant impact on plant, animal, and human
257
M.M. Verstraete et al. (eds.), Observing Land from Space: Science, Customers and Technology, 257–268.
© 2000 All Rights Reserved. Printed in the Netherlands.
THE NASA EARTH SYSTEM SCIENCE
PROGRAM IN 21ST CENTURY
G. Asrar
NASA Headquarters, Washington D.C., USA.
1.
INTRODUCTION
The Earth is a dynamic system of land, oceans, and atmosphere that has
evolved as a result of the complex biological, chemical and physical
processes. These processes are interconnected by an intricate and fragile web
that helps modulate such things as weather, droughts and floods and can
ultimately have profound impacts on global food production, natural
resource management, commerce and the global economy. The recently
experienced 1997–98 El Niño cycle illustrates this complex interaction that
began when the normal state of the Pacific ocean was perturbed by a
weakening of the westerly trade winds; a state that is necessary to maintain a
“pool” of warm water within the western tropical Pacific. The weakening of
trade winds allowed warm water to flow eastward along the equator to
coastal Peru. The eastward-spreading water brought with it the associated
tropical rainfall. As the warm pool reached the coast of Peru, it spread to the
north and south progressively cutting off the nutrient-rich upwelling along
the Peruvian coast, and causing a collapse of the fishery and impacting the
seabird population. As the heat from the warm pool escaped into the
atmosphere it impacted global atmospheric circulation including the global
jet streams. This perturbed atmospheric state brought unusual weather
around the world, where normally wet regions such as Indonesia and
northern Australia, experienced drought and wildfires, and normally dry
regions, such as southern California, experienced floods and mudslides.
These changes, in turn, had a significant impact on plant, animal, and human
257
M.M. Verstraete et al. (eds.), Observing Land from Space: Science, Customers and Technology, 257–268.
© 2000 All Rights Reserved. Printed in the Netherlands.