COSMIC-2 Satellites Improve Tropical Weather Forecasts
[COSMIC-2 spacecraft image. From NOAA]
[NOAA] The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) are satellites launched in 2006 to orbit the earth about 500 miles above ground. They use radio signals from Global Positioning System satellites in a process called “radio occultation” to measure temperature and moisture with high accuracy and resolution. These data have proven to improve global weather forecasts since they became available.
A new study looked at how much weather forecast models would improve by adding more radio-occultation temperature and moisture data from satellites similar to COSMIC that were launched this past June (COSMIC-2), along with another proposed set of satellites. This second set of satellites consists of 6 satellites that stay near the equator and 6 more that move north and south somewhat close to the poles, what we call high-inclination orbit. The work uses a technique known as an Observing System Simulation Experiment (OSSE). Observations like real ones that this new set of satellites would produce are created and added to a weather forecast model along with the data that are usually available. This study also investigates the impact of reducing the number of satellites for the high-inclination orbit from 6 to 4, and the impact of slightly degrading the 6 satellites in high-inclination orbit to the older COSMIC level of accuracy.
Important Conclusions:
- The biggest forecast improvement from the 6 COSMIC-2 satellites near the equator is in the tropics, and the addition of a high-inclination orbit constellation is necessary to improve weather forecasts globally.
- The largest impact from reducing COSMIC-2 from 6 to 4 satellites is to slightly degrade weather forecasts in the northern hemisphere outside the tropics.
- The impact of degrading the 6 high-inclination orbit COSMIC-2 satellites to COSMIC level of accuracy, in terms of penetration into the lower troposphere, is mostly neutral.