Fractals, Multifractals and Scaling Laws in the Past and Future of Cloud Remote Sensing: From the Edge-of-Space to Far-Far Beyond
Abstract
Clouds are notoriously complex atmospheric phenomena that defy our understanding at least to the point where they are still identified in recent IPCC assessments as major sources of uncertainty in predicting future climate using Global Climate Models (GCMs). They top the list of challenging unresolved processes in GCMs with cloud feedbacks---What will clouds be like in a warmer climate?---and the so-called indirect aerosol impacts---How do the interactions of clouds and aerosols, both natural and anthropogenic, affect the climate system? They are also key agents in extreme weather events: tornadoes, hurricanes, floods, etc. Consequently, the National Academies have singled out clouds (along with convection, precipitation and aerosols) as "designated observables" (highest priority targets) in NASA's 2017 Earth Science Decadal Survey from which space-based missions and suborbital investigations will be formulated and deployed over the next 10 years.
Looking back, Mandelbrot's mantra "mountains are not cones, and clouds are not spheres" found quantitative validation in Lovejoy's seminal 1982 article in Science using a combination of thermal IR images from space and ground-based radar scans. Fractals, multifractals, and scaling laws have since then been used in numerous ways to understand cloud remote sensing data over the full range of scales from broad swaths to sub-pixel processes. Brownian motion and the law of first returns have been used to bring new clarity to classic radiative transfer (RT) theory, that is, the physics underlying the radiance signals observed from ground-based, airborne, and satellite sensors. Generalizations of RT that account for the stochastic turbulent structure of clouds have been developed. Some of these theoretical developments have found applications in practical cloud remote sensing, and more are coming that will address the challenges of cloud remote sensing in the next decade. We will survey the rich history and bright future of (multi)fractals, scaling laws, clouds, and remote sensing with special emphasis on high-altitude sensors such as JPL's AirMSPI deployed on NASA's ER-2 at 20 km above the Earth's surface (a.k.a. the "edge of space"), on satellites in low-Earth and geostationary orbits, as well as at the Lagrange-1 point (~10^6 miles from Earth toward the Sun).- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMNG13B0742D
- Keywords:
-
- 4430 Complex systems;
- NONLINEAR GEOPHYSICS;
- 4485 Self-organization;
- NONLINEAR GEOPHYSICS;
- 4490 Turbulence;
- NONLINEAR GEOPHYSICS;
- 4499 General or miscellaneous;
- NONLINEAR GEOPHYSICS