GFDL - Geophysical Fluid Dynamics Laboratory

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Will the Wet Get Wetter and the Dry Drier?

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2-D Graphics & Maps
Animations & Movies
  • GFDL scientist contacts for this topic:
    Isaac Held, NOAA/GFDL
    Gabriel Vecchi, NOAA/GFDL
  • GFDL Communications Officer: Maria Setzer, NOAA/GFDL
  • Graphics developed by:  Gabriel Vecchi, NOAA/GFDL
  • Animations developed by: Keith Dixon, NOAA/GFDL

Contact information (email, phone numbers) can be found for these people by entering their names into the NOAA Staff Directory.

The materials presented here help illustrate some of the key research results that GFDL scientists have reported on recently. These graphics are considered to be in the public domain, and thus can be downloaded freely. We do request that if these images are used in publications or media broadcasts credit be given to “NOAA Geophysical Fluid Dynamics Laboratory” or at least “NOAA GFDL“.

 2-D Graphics and Maps
[map of change in precipitation by end of 21st century - NOAA GFDL]
ABOVE: 500 x 200 png [150KB]

Also available in

figure caption: The change in annual average precipitation projected by the GFDL CM2.1 model for the 21st century. These results are from a model simulation forced according to the IPCC SRES A1B scenario [IPCC, 2000] in which atmospheric carbon dioxide levels increase from 370 to 717 ppm. The plotted precipitation differences were computed as the difference between the 2081 to 2100 twenty year average minus the 1951 to 2000 fifty year average. Blue areas are projected to see an increase in annual precipitation amounts. Brown areas are projected to receive less precipitation in the future. (Note the irregular color bar intervals.)

[zonally averaged precipitation change graphs]
ABOVE: 499 x 480 png [73KB]

figure captions:

[Above Left] Annual precipitation amounts averaged around the Earth along each latitude circle, as simulated by the GFDL CM2.1 model over the period 1951-2000. Notice the strong precipitation near the Equator, and the relative minima in precipitation near 20°S and 20°N – latitudes in the subtropical dry zones.

[Above Right] 21st Century precipitation changes as projected by the GFDL CM2.1 model, averaged around the Earth along each latitude circle. The precipitation changes are computed as differences between the 2081-2100 twenty-year average and the modeled 1951-2000 fifty-year average (the values shown to the left).

Note: Notice that latitude zones receiving relatively high amounts of precipitation in the late 20th century simulation (left), such as the near-equatorial tropics and the high latitudes centered at 60°N and 60°S, show a pronounced increase in 21st century precipitation (right). Also note that decreases in
precipitation are projected for the subtropical dry regions – particularly on their poleward flank. The projected changes are in response to increasing greenhouse gases and changing aerosols based on a “middle of the road” estimate of future emissions. This scenario is denoted as IPCC SRES A1B. General information about the GFDL CM2.1 model can be found in Delworth et al [2006].


  • For more details about the computer modeling studies that produced the information displayed in these animations, please refer to oursummary in PDF form.
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 Animations and Movies
[maps of model-simulated 21st century precipitation changes]

[mpg icon]years 1901 to 2100: 720 x 480 resolution, 30fps .mpg format, 1600 frames total, 53.3 seconds at 30 fps [21MB]
[quicktime player icon]years 1901 to 2100: 720 x 480 resolution, 30fps .mov format, 1600 frames total, 53.3 seconds at 30 fps [15MB]

animation description

This animation depicts the time evolution of five-year averages of annual precipitation as simulated in the GFDL CM2.1 model for the period 2000 to 2100. Rather than mapping rainfall amounts in units of inches or millimeters, we have chosen to bin the values at each model grid point into five categories (indicated by the five colors in the color bar at the bottom of the plot).

The categories were calculated as follows. After computing five year running averages of annual precipitation for each GFDL CM2.1 model grid point, the 1901-2000 period was analyzed. For each model grid point the maximum and minimum values for the 20th century were noted. Also, at each grid point, the individual 20th century five year rainfall values were ranked in order from driest to wettest, and then divided into three groups. Rainfall amounts falling in the driest third are designated below nomal (light tan), the wettest third are categorized as above normal (pale blue-green), and the middle third as near normal (off white). By definition these three middle colors will be the only ones would appear in maps the modeled 1901 to 2000 period.

After 2000, when a five year precipitation average is less than any of the one hundred five year running averages simulated for the 20th century, that point and time is classified as drier than the 20th century (saddle brown). Similarly, when a five year rainfall value is greater than any simulated for that grid point during 1901-2000 period, it is labelled wetter than the 20th century (darker blue-green).

These animations were produced using the output of the CM2.1 “H2” historical experiment for the 1901-2000 time period and the CM2.1 SRES A1B run for the 2001-2100 period.