Kerbal Weather Project
Upper Air Analyses
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The videos below show the spatial and temporal evolution of weather, above Kerbin's surface, during the first year of the MPAS simulation (after the spin-up period). In each video, grey lines depict landmasses while gridded white lines show parallels of latitude and meridians of longitude. Weather animations are looped daily at 00 UT.
In this animation, one year of 250 hPa heights (contoured) and winds (shaded) are looped. Contours show the height of the 250 hPa pressure surface above sea level while wind barbs show the direction and speed of the wind. At mid-latitudes, strong westerly winds dominate the circulation in the form of Rossby waves. These waves are associated with narrow bands of very strong winds, called jet streams, which are visible in both hemispheres. Within the jet stream, height (black) contours are tightly packed. This is because the gradient in the height of a constant pressure surface is related to the strength of the wind. In the tropics, 250 hPa winds are generally quite light. Jet streams are associated with large gradients in temperature which are not observed in the tropics where the atmosphere is largely barotropic.
The above animation displays the vertical velocity at 500 hPa during the first year of the MPAS simulation. Black contours show the height of the 500 hPa surface above sea level. Note that vertical velocity is displayed in cm/s. Regions of rising air are shaded in red while regions of sinking air are shaded in blue. Examining the loop above one can see strong rising motion in the central cores of hurricanes. Hurricanes are warm-core low-pressure systems with strong vertical motion associated with deep convection in and around the eye-wall. Sinking motion within the eye of hurricanes is not visible in the above animations due to the coarse resolution of the MPAS simulation which poorly resolves hurricane structure. In the mid-latitudes, atmospheric waves are observed within the jet stream and in the vicinity of high terrain. These waves are characterized by an alternating pattern of rising and sinking motion.
The animations above display relative humidity at 700 hPa and temperature at 850 hPa, during the first year of the MPAS simulation. Wind barbs depict the wind speed/direction while black contours show the height of the pressure surface above sea level. At 850 hPa, temperatures are consistently warm over the tropics. Since 850 hPa is fairly low in the atmosphere (~1.5 km a.s.l.), fronts are visible in the temperature animation. Most notably, cold fronts are seen in the mid-latitudes bringing cool and dry polar air equatorward. At 700 hPa, lower relative humidity is observed behind mid-latitude cold fronts. In the tropics, high humidity is fairly persistent over the ocean. In contrast, low humidity is observed over the continent east of the KSC and in the sub-tropics.