created by Stephen Po-Chedley and Chris Terai, Atmospheric Sciences (2012)
The MERRA Circulation Lab is intended to help illustrate some of the concepts involved with radiation and transport. It is crucial to understand that imbalances in heating lead to atmospheric circulations that redistribute heat and moisture (energy). This lab challenges students to interpret and map the Hadley Circulation using real output from the NASA MERRA reanalysis model. Some understanding of vectors, solar radiation distribution and its seasonal cycle, convection, and energy/mass conservation are required. This laboratory could be used to illustrate more advanced topics such as the effects of the Coriolis force, trade winds, the distribution of deserts in the downwelling (sinking air) branches of the Hadley cell, the reason for the sub-tropical highs, or to explain the intertropical convergence zone (ITCZ).
1. What is the Hadley Circulation?
2. What causes the Hadley Circulation?
3. Why does the Hadley Circulation move around throughout the year?
1. To understand what a reanalysis model is and why scientists use it.
2. To use reanalysis model data to trace a realistic Hadley cell (demonstrate that this is not just a conceptual figure, but shows up in the real Earth climatology).
3. To draw parallels to convection, understanding that the sun heats the surface causing upwelling (rising air), which induces a thermally direct cell.
4. To observe that the ITCZ or upwelling branch of the Hadley cell generally follows the region of most intense solar radiation.
5. To note that the entire cell is important to conserve mass - if any branch were missing mass would not be conserved.
6. Advanced: To make it clear that the Hadley Cell is redistributing the intense radiative energy at the equator to higher latitudes.