How a Laser Can Help Distinguish Water and Ice in Clouds ⚡ экспресс
Specular reflections hinder space lidars from determining whether clouds are made of water or ice. A quantum lidar with parametric mode separation (QPMS) has been proposed, which, thanks to nonlinear filtering, suppresses noise in the signal much more strongly than conventional methods. This allows the specular reflection component to be intentionally amplified, and, working in tandem with a traditional lidar, accurately calibrates phase measurements. This approach is akin to picking out a faint echo in a noisy room: extraneous sounds are cut off, making the soft reply discernible.
When a satellite laser beams downward at clouds, it often gets blinded by specular glare—especially if ice crystals form a smooth surface. This glare masks details, making it impossible to tell what's below: water or ice. Instead of fighting the blinding, scientists decided to use it. The quantum filter in the new lidar works like polarized sunglasses: it dampens scattered light, leaving only the direct mirror-like reflection. By comparing images taken with and without the filter, you can confidently distinguish droplets from crystals. Theoretical calculations confirm the method works even with a weak signal. Paradoxically, it's precisely that mirror-like quality that made lasers useless that became the key to solving the puzzle. In the future, this will allow satellites to peer into clouds without errors, improving weather forecasts and climate models.
🎯 The mirror reflection from icy clouds can be so strong that it completely 'blinds' satellite lasers, rendering them useless for analyzing cloud composition.