1:45 PM - 3:15 PM
[O11-P73] Quantification in Iridescent Clouds Model Experiments - Changes in Light Sources and Clouds Formation Conditions -
Keywords:Iridescent Clouds, Reproduction Experiment, Quantify
1 Introduction
Iridescent clouds are a phenomenon in which sunlight hitting the contours of cirrus and altocumulus clouds is diffracted and interfered with by cloud particles, causing the clouds to appear colored. Experiments to reproduce iridescent clouds are often taken up as an introduction to understanding atmospheric optical phenomena, but there are few examples of quantitative treatment of cloud and light source conditions.
As a previous study, Yamashita, 2004 reported that a cloud was created in a flask using the decompression of a rubber balloon when it deflated, and that a iridescent cloud was created by irradiating light.In this study, The depressurization was accurate, but the conditions for cloud formation other than the light source and atmospheric pressure were not changed. Sapporo Keisei High School (2023) conducted similar research using plastic bottles.In this report, the relationship between the angle at which iridescent clouds were observed and their color was quantified, but the relationship is not quantitative with respect to cloud conditions.
In this study, I used a desiccator to reduce the pressure, and changed the atmospheric pressure difference, water vapor content, and cloud volume in three steps, and compared them with sunlight and a white LED light source to find the conditions for creating highly saturated and persistent iridescent clouds.
2 Research Methods and Results
2-1 Experiments and results with different cloud formation conditions and light sources
(1) A wet rag was placed in an acrylic case and sealed it tightly.
(2) A barometer and the acrylic case were placed in a desiccator, and incense smoke that imitates a cloud nucleus was introduced into the acrylic case for 3 seconds.
(3) The inside was decompressed using a vacuum pump to generate a cloud.
(4) A light source was illuminated, and the light source, cloud, and observer were aligned in a straight line for observation. (Figure 1)
In the light source variation in (4), clouds generated using 50 ml water in 2316 cm3 volume under a 200 hPa pressure difference. These conditions produced relatively vivid iridescent clouds, which I then exposed to sunlight and LED light sources for comparison. I illuminated clouds generated under other conditions only with LEDs and made comparisons focusing on the conditions under which we generated the clouds.
The results are shown in Table 1. There was no significant difference in the observed color when the light source was varied.
2-2 Experiments and results with different light sources and pressure differences
The objective was to analyze the difference in color change due to diffraction by setting the air pressure difference finer than 2-1, changing the color range, and irradiating two different light sources.
(1) A barometer and a rag wetted with 50 ml of water were placed in a desiccator, and incense smoke imitating a cloud nucleus was introduced for 3 seconds.
(2) The inside of the desiccator was decompressed in six steps (50, 100, 150, 200, 250, and 300 hPa) using a vacuum pump to generate clouds.
(3) Two types of light sources (sunlight and LED light) were illuminated, and the light source, cloud, and observer were aligned in a straight line for observation.
In terms of light source, the full spectrum of colors was observed in sunlight, whereas colors were biased toward green, purple, magenta, and orange in the case of LED light. In addition, the color range became narrower as the pressure difference increased for both light sources (Figure 2).
3 Consideration
The method used in this study can reliably generate iridescent clouds when the pressure is reduced using an appropriate amount of water vapor. This method appears to produce more stable and readily observable cloud coloring because it generates the color across a wider area compared to the conventional methods. On the other hand, when the difference in water vapor and atmospheric pressure is large, the amount of clouds per an acrylic case is large, and the overlapping of clouds causes Mie scattering, which results in no coloration. I propose that larger pressure differences lead to a narrower color range in the observed clouds. This is because diffraction is dependent on both wavelength and particle size, and larger pressure differences tend to result in smaller cloud particle sizes.
The different colors observed in the clouds under various light sources are probably a result of the unique spectrum of each light source (Figure 3).
Since the spectrum of sunlight is relatively uniform, all spectra of the colored clouds can be observed, while white LEDs have extremely large blue and green spectra, so the colors of the colored clouds are also unevenly distributed.
Iridescent clouds are a phenomenon in which sunlight hitting the contours of cirrus and altocumulus clouds is diffracted and interfered with by cloud particles, causing the clouds to appear colored. Experiments to reproduce iridescent clouds are often taken up as an introduction to understanding atmospheric optical phenomena, but there are few examples of quantitative treatment of cloud and light source conditions.
As a previous study, Yamashita, 2004 reported that a cloud was created in a flask using the decompression of a rubber balloon when it deflated, and that a iridescent cloud was created by irradiating light.In this study, The depressurization was accurate, but the conditions for cloud formation other than the light source and atmospheric pressure were not changed. Sapporo Keisei High School (2023) conducted similar research using plastic bottles.In this report, the relationship between the angle at which iridescent clouds were observed and their color was quantified, but the relationship is not quantitative with respect to cloud conditions.
In this study, I used a desiccator to reduce the pressure, and changed the atmospheric pressure difference, water vapor content, and cloud volume in three steps, and compared them with sunlight and a white LED light source to find the conditions for creating highly saturated and persistent iridescent clouds.
2 Research Methods and Results
2-1 Experiments and results with different cloud formation conditions and light sources
(1) A wet rag was placed in an acrylic case and sealed it tightly.
(2) A barometer and the acrylic case were placed in a desiccator, and incense smoke that imitates a cloud nucleus was introduced into the acrylic case for 3 seconds.
(3) The inside was decompressed using a vacuum pump to generate a cloud.
(4) A light source was illuminated, and the light source, cloud, and observer were aligned in a straight line for observation. (Figure 1)
In the light source variation in (4), clouds generated using 50 ml water in 2316 cm3 volume under a 200 hPa pressure difference. These conditions produced relatively vivid iridescent clouds, which I then exposed to sunlight and LED light sources for comparison. I illuminated clouds generated under other conditions only with LEDs and made comparisons focusing on the conditions under which we generated the clouds.
The results are shown in Table 1. There was no significant difference in the observed color when the light source was varied.
2-2 Experiments and results with different light sources and pressure differences
The objective was to analyze the difference in color change due to diffraction by setting the air pressure difference finer than 2-1, changing the color range, and irradiating two different light sources.
(1) A barometer and a rag wetted with 50 ml of water were placed in a desiccator, and incense smoke imitating a cloud nucleus was introduced for 3 seconds.
(2) The inside of the desiccator was decompressed in six steps (50, 100, 150, 200, 250, and 300 hPa) using a vacuum pump to generate clouds.
(3) Two types of light sources (sunlight and LED light) were illuminated, and the light source, cloud, and observer were aligned in a straight line for observation.
In terms of light source, the full spectrum of colors was observed in sunlight, whereas colors were biased toward green, purple, magenta, and orange in the case of LED light. In addition, the color range became narrower as the pressure difference increased for both light sources (Figure 2).
3 Consideration
The method used in this study can reliably generate iridescent clouds when the pressure is reduced using an appropriate amount of water vapor. This method appears to produce more stable and readily observable cloud coloring because it generates the color across a wider area compared to the conventional methods. On the other hand, when the difference in water vapor and atmospheric pressure is large, the amount of clouds per an acrylic case is large, and the overlapping of clouds causes Mie scattering, which results in no coloration. I propose that larger pressure differences lead to a narrower color range in the observed clouds. This is because diffraction is dependent on both wavelength and particle size, and larger pressure differences tend to result in smaller cloud particle sizes.
The different colors observed in the clouds under various light sources are probably a result of the unique spectrum of each light source (Figure 3).
Since the spectrum of sunlight is relatively uniform, all spectra of the colored clouds can be observed, while white LEDs have extremely large blue and green spectra, so the colors of the colored clouds are also unevenly distributed.