Kerbal Weather Project
Clouds and Precipitation
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The following videos show the spatial and temporal evolution of cloud cover and precipitation on Kerbin, 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.
The animation above shows simulated infrared satellite (IR) imagery. In MPAS simulations this simulated IR satellite imagery is derived from the top of atmosphere (TOA) outgoing longwave radiation (OLR). Real-world IR satellites convert the amount of outgoing IR radiation incoming into a temperature. This "brightness" temperature is displayed in IR satellite imagery. Higher brightness temperatures are represented by darker shades of gray, while lower brightness temperatures are represented by brighter shades of gray and white. In the troposphere temperature decreases with height. Consequently, low clouds appear darker on an infrared image and higher clouds appear brighter. The very dark shades of gray and black indicate regions where cloud cover is absent and the ground is being heated by the sun.
Above, total precipitable water (TPW) is shown for the first year of the MPAS simulation. Precipitable water, like rainfall, is measured in millimeters. It is derived by calculating the amount of liquid water that could be obtained from the surface to the top of the atmosphere if all of the water was condensed. The highest values of TPW are observed over the oceans, especially near the equator, where high levels of evaporation enhance the moisture content of the atmosphere. In the loop above, tropical cyclones (hurricanes) are visible forming in the tropics north and south of the equator. These hurricanes are visible as compact regions of high TPW rotating counter-clockwise (clockwise) in the northern (southern) hemisphere. Branches of elevated TPW are also observed, extending from the tropics into the mid-latitudes. These atmospheric rivers transport moisture from the tropics toward the poles and are associated with extratropical (mid-latitude) cyclones and heavy precipitation.
Daily accumulated rainfall and snowfall are displayed above, for the first year of the MPAS simulation. In these maps, daily precipitation refers to the amount of precipitation that has accumulated over the previous Kerbin day (i.e., 6-hours). Rainfall is most intense over the ocean where the moisture content of the atmosphere is typically higher than over land. In the extratropics, rainfall is associated with fronts and areas of low pressure. At high-latitudes and over high-terrain precipitation falls as snow. Daily accumulated precipitation is minimal at the poles where frigid temperatures severally limit the amount of moisture the atmosphere can contain.