Mosaics of the World

On this entry I just want to post some global images. I find them very interesting since they show how different weather can be at different areas of the world at any given time. I will keep this entry simple and free of some of the technicalities and jargon of our field.

The first one is a global mosaic image of water vapor obtained from the University of Washington's dataset.  In this image we can appreciate how different patterns dominate different latitudes. Near the equator we see a long band of patchy cloudiness. This is what we know as the Intertropical Convergence Zone (ITCZ), and we usually associate it with ascending motion and convergence of the trade winds. In previous centuries, sailors despised this area because of its tendency to be either calm (weak winds), or because of the terrible storminess associated with the ITCZ.  Clouds in this region can be very high (more than 15 km high) and very intense!

The other area that is quite apparent is in the midlatitudes. Here we see a little waviness and some big looking storms, known as extratropical cyclones. This area is dominated by the troughs and ridges that make the everyday weather of areas like the United States and Europe. These guys are usually embedded in a west to east motion that we like to call the westerlies.

Even these features just look like everyday weather patterns that just move around, making some places sunny and other rainy, they also constitute important pieces of our planet's general circulation, and are key to the poleward transport of energy, cooling the tropics and warming the poles.


In this infrarred (IR) image, obtained from the CLAUS database, we can observe the same features. Here, bright white colors denote cold temperatures. Notice how tropical clouds can be very white, evidencing how high these clouds can be. The image is more grey-ish closer to the poles because it is much colder there than in the tropics and hence the satellite captures less outgoing radiation. A lot of satellite sensors obtain their data this way and we call them passive sensors.

This last image, recently taken from CIMMS MIMIC-TPW shows some of the aforementioned features. The big line packed with precipitable water near the equator is the ITCZ, the circle is the currently active tropical storm 5, and the black rectangle is the active phase of the MJO, which I have mentioned in previous posts. There are also some interesting river-like features at higher latitudes, which is often related to moistures being carried by frontal systems and troughs.