Contents

2-D Graphics

Animations

Contacts

• GFDL scientist contacts for this topic:
  Isaac Held, NOAA/GFDL
  Thomas Delworth, NOAA/GFDL
  
• GFDL Communications Officer: Maria Setzer, NOAA/GFDL
  
• Animations developed by: Keith Dixon, NOAA/GFDL
  

Up to date 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

ABOVE: 500 x 200 png [41KB]

Select the camera icon to the left to access a Higher Resolution Version 1040 x 420 png [108KB]

figure caption

Trends in July-Aug.-Sept. (wet season) rainfall over the period 1950 to 2000. Blue areas trend towards more rain, and brown areas toward a drier climate. (Left) The observed trend over land computed from the CRUTS_ 2.1 data set [Dai et al., 2004]. (Center) The average trend simulated in an eight member ensemble of GFDL CM2 coupled atmosphere-ocean model runs. (Right) The average trend simulated in a ten member ensemble of GFDL atmosphere-land model runs with observed sea surface temperatures (SSTs).

ABOVE: 440 x 280 png [32KB]

Select the camera icon to the left to access a Higher Resolution Version 880 x 600 png [86KB]

figure caption

5-year running means (July-Aug.-Sept.) of Sahel rainfall, normalized so its average value over 1901-2000 is equal to 1.0. Black curve = observations. Thick light blue line = historical CM2 ensemble mean (n=8). Red line = CM2 simulation that most resembles the observed 1950-2000. The gray area represents ±1 standard deviation within the ensemble. The six curves for 2000-2100 are projections for three future emissions scenarios, one set of three from from CM2.0 and another from CM2.1. The dark blue line highlights results from the CM2.0 SRES A1B experiment. See Held et al. (2006) for details.

Animations

Animations of the type indicated by the picture above are available in two different sizes.
Select an icon below to access the animation described to its right. We provide multiple versions of this animation, including versions using the mpg-4 format (well-suited for Windows Media Player viewing) and others in .mov format that is well-suited for viewing with QuickTime viewer.
(Clicking the picture above will direct you to the mpg-4 version of the lower resolution animation.)

720 x 480 resolution, 6fps mpg-4 format, 200 frames total, 33.3 seconds at 6 fps [3.0MB]
720 x 480 resolution, 6fps .mov format, 200 frames total, 33.3 seconds at 6 fps [1.8MB]

720 x 480 resolution, 4fps mpg-4 format, 200 frames total, 50 seconds at 4 fps [3.0MB]

1280 x 720 resolution, 6fps mpg-4 format, 200 frames total, 33.3 seconds at 6 fps [5.1MB]
1280 x 720 resolution, 6fps .mov format, 200 frames total, 33.3 seconds at 6 fps [2.9MB]

1280 x 720 resolution, 4fps mpg format, 200 frames total, 50 seconds at 4 fps [5.1MB]

animation description

This animation depicts the time evolution of five-year averages of African precipitation as simulated in the GFDL CM2.0 model for the period 1901 to 2100. On the left side of the frame, 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 (seen as 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 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 that appear in the 1901 to 2000 period of the animation.

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).

The red box that appears on the map of Africa focuses on the Sahel region. It is the modeled rainfall inside the area of this box that is averaged over for the line plot that appears on the right side of the frame. The graph to the right shows how the 5 year running mean precipitation values averaged over the Sahel region varies in time during the GFDL CM2.0 model simulation. For this calculation, the rainfall that falls over the Sahel is not treated as a category, by rather in the more typical units of inches or millimeters of precipitation that fell across that region during each five year period. For plotting purposes, values are normalized (scaled) so the 1901-2000 average = 1.0. The lower limit of the graph's vertical axis lies at 0.60, indicating 60 percent of the 1901-2000 Sahel rainfall average.

These animations were produced using the output of the CM2.0 "h1" historical experiment for the 1901-2000 time period and the CM2.0 SRES A1B run for the 2001-2100 period. This experiment was one of those highlighted in the paper:
Held, et al., (2005): Simulation of Sahel drought in the 20th and 21st centuries. Proceedings of the National Academy of Sciences, Vol. 102, No. 50, page 17891-17896.

For more details about the computer modeling studies that produced the information displayed in these animations, please refer to the Sahel Drought: Past Problems, an Uncertain Future summary in PDF form.