Effects of solar activity and geomagnetic field on noise in CALIOP profiles above the South Atlantic Anomaly

Abstract

By documenting noise levels in 6.5 yr of nighttime measurements by the spaceborne lidar CALIOP above the South Atlantic Anomaly (SAA), we show they contain information about the evolution of upwelling high-energy radiation levels in the area. We find the amount of noisy profiles is influenced by the 11 yr cycle of solar activity, fluctuates by ±5% between 2006 and 2013, and is anticorrelated with solar activity with a 1 yr lag. The size of the SAA grows as solar activity decreases, and an overall westward shift of the SAA region is detectable. We predict SAA noise levels will increase anew after 2014, and will affect future spaceborne lidar missions most near 2020. In other areas, supposedly unaffected by incoming sunlight, nighttime noise levels are much weaker but follow the same 11 yr cycle, superimposed with a one-year cycle that affects both hemispheres similarly and could be attributed to geomagnetic activity

An EarthCARE/ATLID simulator to evaluate cloud description in climate models

“…In particular, we will use the first year of ATLID Level 1 data to built a statistically significant estimate of the ATLID actual SNR in aerosol‐free stratosphere areas, during daytime and during nighttime over different regions, different seasons, and over different surface types (ocean, continent, and ice sheet) as well as above highly reflecting low‐level liquid clouds. These information will be used to test and change [as in, e.g., Noel et al ., ; Chepfer et al ., ] the threshold values consistently in the simulator and in the algorithm to be used for processing ATLID actual data. In any case, because of the solar photons, the daytime cloud detection threshold will be applicable for comparison with profiles collected in both daytime and nighttime, whereas the nighttime threshold will be applicable for comparison with profiles collected in nighttime data only.…”