Related Experiment Video
Updated: Mar 17, 2026
03:49
Evaluating Flight Performance and Eye Movement Patterns Using Virtual Reality Flight Simulator
Published on: May 19, 2023
1.6K
Physical interpretation of gray cloud observed from airplanes
Applied Optics
|July 28, 2016
Summary
Gray clouds appear darker than white clouds due to specific atmospheric conditions. This phenomenon occurs when optically thin, higher clouds overlap lower clouds along the line of sight, reducing brightness by approximately 25-30%.
Area of Science:
- Atmospheric Science
- Cloud Physics
- Radiative Transfer
Background:
- Clouds are essential components of Earth's climate system.
- Cloud appearance, including color and brightness, is influenced by light scattering and absorption.
- The perception of cloud color can be complex, especially under varying observation angles.
Purpose of the Study:
- To investigate the reasons behind the observation of gray clouds appearing to overlap with white clouds.
- To understand the optical conditions that lead to a perceived brightness depression in clouds.
Main Methods:
- Utilized photographic observations from an airplane.
- Employed simulations with a three-dimensional radiative transfer model.
Main Results:
- Observed gray clouds exhibited a brightness depression rate of approximately 25% compared to surrounding whitish clouds.
- Simulations indicated a brightness depression rate as high as 30% under specific conditions.
- Identified two key conditions for observing gray clouds: (1) near-horizontal observation of an optically thin higher cloud overlapping a lower cloud, and (2) the higher cloud being optically thick along the line of sight.
Conclusions:
- The apparent grayness of clouds is a result of their optical properties and their relative positions and altitudes.
- The overlap of an optically thin, higher cloud with a lower cloud, when viewed obliquely, causes a significant brightness depression.
- Radiative transfer modeling supports observational findings, confirming the conditions necessary for gray cloud perception.
More Related Videos
Related Concept Videos
01:26Influence of Earth's Curvature and Atmospheric Refraction on Leveling
1.1K
During leveling, the Earth's curvature and atmospheric refraction introduce deviations in the line of sight from a true horizontal reference. When the line of sight is leveled, it remains perpendicular to the plumb line only at a single point. Beyond this, it deviates due to the Earth’s curvature, represented by the correction C. For a sight distance D, the deviation can be derived using the relationship:This relationship shows that the deviation increases quadratically with distance. Over a...
1.1K
01:18Boundary Layer Characteristics
771
When a fluid encounters a solid surface, a boundary layer forms due to the interaction between the fluid's motion and the stationary surface. This phenomenon is characterized by a thin region adjacent to the surface where viscous forces dominate, influencing the fluid's velocity profile. The development of the boundary layer begins at the leading edge of the surface and evolves as the fluid moves downstream.As the fluid flows over the surface, friction between the fluid and the wall slows down...
771
01:23Lift
642
Lift is a fundamental aerodynamic force that acts perpendicular to the direction of airflow. It plays a central role in achieving and sustaining flight and in stabilizing various vehicles. Lift primarily originates from pressure differences created across surfaces, such as an airfoil. A lower pressure region forms above the wing, while a higher pressure region forms below it, generating an upward force. This differential results from the shape and orientation of the airfoil, enabling the wing...
642
01:24Absolute Motion Analysis- General Plane Motion
666
Visualize a drone, with its propellers spinning rapidly, hovering mid-air. The fascinating movements and operations of this drone can be comprehended by applying the principle of general plane motion.
As the drone's propellers rotate, an upward force is generated that counteracts the force of gravity, enabling the drone to lift off from the ground. This initial movement of the drone is along a straight path, representing a form of translational motion. In this phase, every point on the...
As the drone's propellers rotate, an upward force is generated that counteracts the force of gravity, enabling the drone to lift off from the ground. This initial movement of the drone is along a straight path, representing a form of translational motion. In this phase, every point on the...
666
01:13Attenuated Total Reflectance (ATR) Infrared Spectroscopy: Overview
1.5K
Attenuated total reflectance (ATR) infrared spectroscopy is a powerful analytical technique used to study the composition of materials. It is widely employed in chemistry, materials science, forensic science, and other fields where sample characterization is required. ATR has several advantages over traditional transmission IR spectroscopy, including the requirement of little to no sample preparation and the ability to analyze a wide range of samples.
The ATR process begins by directing a beam...
The ATR process begins by directing a beam...
1.5K
01:29Application of Linearization and Approximation
129
A drone flying through complex terrain often relies on more than one sensing method to estimate small changes in altitude. Along with direct measurements, air pressure provides a useful indirect indicator of vertical movement. Atmospheric pressure decreases as altitude increases, and this relationship is commonly described using an exponential model. Although accurate, converting pressure measurements into altitude values requires calculations that are too complex to perform repeatedly during...
129