{"id":4894,"date":"2024-04-10T01:35:00","date_gmt":"2024-04-10T01:35:00","guid":{"rendered":"https:\/\/new.www.purdue.edu\/newsroom\/?post_type=purduetoday&#038;p=4894"},"modified":"2025-07-30T13:40:31","modified_gmt":"2025-07-30T17:40:31","slug":"cloudy-science-clear-insights-atmospheric-scientist-studies-clouds-causes-and-effects","status":"publish","type":"post","link":"https:\/\/www.purdue.edu\/newsroom\/2024\/Q2\/cloudy-science-clear-insights-atmospheric-scientist-studies-clouds-causes-and-effects","title":{"rendered":"Cloudy science, clear insights: Atmospheric scientist studies clouds\u2019 causes and effects"},"content":{"rendered":"\n<p><strong>WEST LAFAYETTE, Ind.<\/strong> \u2014 Every cloud is lined, not with silver, but with science \u2014 at least from cloud expert Alexandria Johnson\u2019s point of view.<\/p>\n\n\n\n<p>Clouds are ubiquitous. They are one of the most notable characteristics of planet Earth. Studying them is akin to studying the blood and arteries of the planet itself.&nbsp;<a href=\"https:\/\/www.eaps.purdue.edu\/people\/profile\/ablanch.html\" rel=\"noreferrer noopener\" target=\"_blank\">Johnson<\/a>, an atmospheric scientist and assistant professor in Purdue University\u2019s&nbsp;<a href=\"https:\/\/www.purdue.edu\/science\/\" rel=\"noreferrer noopener\" target=\"_blank\">College of Science<\/a>, studies clouds wherever they are: in her lab, on Earth, throughout the solar system and into the galaxy.<\/p>\n\n\n\n<p>\u201cThe coolest thing about my research is that I can see clouds every day,\u201d Johnson said. \u201cI can look up into our own atmosphere and watch them change and evolve. Then I can take that knowledge and apply it to other planetary bodies, both within and outside our solar system.\u201d<\/p>\n\n\n\n<p>The science of clouds covers a lot of ground, and her research often reveals the unexpected. How to make theories about the surface of a planet from its cloudy atmosphere, for example. Or the fact that almost every milliliter of raindrops, even in the landlocked Midwest, contains a shocking amount of microplastics.<\/p>\n\n\n\n    <div  class=\"purdue-home-quick-links-static \">\n        <div class=\"tagged-header-container\">\n\n            <h2 class=\"tagged-header\"><span>ADDITIONAL INFORMATION<\/span><\/h2>\n        \n        <\/div>\n\n       <ul class=\"quick-links-content\">\n                                        <li class=\"quick-link__item\">\n                                                                <a class=\"quick-link__link\"\n                                    href=\"https:\/\/www.youtube.com\/watch?v=MEccnizyO-o\" target=\"_blank\">\n                                    Purdue expert: Cloud research                                <\/a>\n                            <\/li>\n                                                <li class=\"quick-link__item\">\n                                                                <a class=\"quick-link__link\"\n                                    href=\"https:\/\/www.nytimes.com\/2023\/10\/26\/science\/venus-plate-tectonics-life.html\" target=\"_blank\">\n                                    Billions of years ago, Venus may have had a key Earthlike feature\u00a0(New York Times article, subscription required)                                <\/a>\n                            <\/li>\n                                                <li class=\"quick-link__item\">\n                                                                <a class=\"quick-link__link\"\n                                    href=\"Four EAPS professors chosen by NASA to study lunar science\" target=\"_blank\">\n                                    Four EAPS professors chosen by NASA to study lunar science                                <\/a>\n                            <\/li>\n                            <\/ul>\n\n<\/div>\n\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Raining buckets and pouring plastics<\/strong><\/h2>\n\n\n\n<p>Like a pearl forming around a speck of sand, clouds coalesce around motes of matter called nuclei. Usually, these nuclei are made of material from outside the atmosphere: a bit of space dust from a meteor skimming the atmosphere or a speck of sand kicked up from the Earth\u2019s surface. But a new type of nuclei is beginning to play a role in natural systems: microplastics.<\/p>\n\n\n\n<p>\u201cPlastic doesn\u2019t degrade,\u201d Johnson said. \u201cIt just breaks down into smaller and smaller pieces that show up in our environments. We have found these microplastics everywhere on the planet, even in remote regions like national parks and Antarctica. However, they are found most densely where humans are because we are the source of the plastic.\u201d<\/p>\n\n\n\n<p>Johnson and her team, including Gouri Prabhakar, assistant professor of practice in the&nbsp;<a href=\"https:\/\/www.eaps.purdue.edu\/index.html\" rel=\"noreferrer noopener\" target=\"_blank\">Department of Earth, Atmospheric, and Planetary Sciences<\/a>, collected samples from several large rain and snow events at&nbsp;<a href=\"https:\/\/ag.purdue.edu\/department\/agry\/acre\/index.html\" rel=\"noreferrer noopener\" target=\"_blank\">Purdue\u2019s Agronomy Center for Research and Education<\/a>&nbsp;in 2023. And they\u2019ve started looking through the samples for something to catch their eyes: brightly colored blips of plastic. They have identified microplastics in every sample they\u2019ve studied. They are now using a scanning electron microscope to find even smaller plastic pieces and better understand their properties.<\/p>\n\n\n\n<p>Microplastics are a health and environmental concern across the globe, but most research has focused on plastics in animals\u2019 bodies or in bodies of water. Johnson and her team are among the first to see that some of that plastic is falling from the sky in the Midwest and link it to clouds and precipitation.<\/p>\n\n\n\n<p>\u201cIn a pristine state, plastic is hydrophobic and won\u2019t act as cloud nuclei,\u201d Johnson said. \u201cHowever, if these microplastics reside in the environment long enough, they can become coated in organics, after which they may act as a cloud condensation or ice nuclei. These aged microplastics could be affecting clouds and precipitation patterns, the effects of which will grow with time as the number of microplastics in our environment increases.\u201d<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>How to catch a cloud and pin it down<\/strong><\/h2>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"alignright size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"876\" height=\"519\" src=\"https:\/\/www.purdue.edu\/newsroom\/wp-content\/uploads\/2024\/07\/johnsona-cloudlab.gif\" alt=\"\" class=\"wp-image-4921\" title=\"\" \/><figcaption class=\"wp-element-caption\">Studying the microphysics of clouds in her lab allows atmospheric scientist Alexandria Johnson to understand the behavior of clouds in the wild \u2014 in Earth\u2019s sky and those of other planets.<\/figcaption><\/figure>\n<\/div>\n\n\n<p>louds are difficult to study. They are, by definition, nebulous as well as enormous, and far from the comfortable climes where humans spend their lives. But understanding how they form and their physics are key to understanding weather, precipitation patterns and the planet itself.<\/p>\n\n\n\n<p>Johnson\u2019s solution is to grow her own clouds in her lab in the Department of Earth, Atmospheric, and Planetary Sciences. She uses minimalistic models to capture the dynamics of the systems, stripping them down to their basics to get a clear understanding on how the particles that make up clouds form, develop and interact with their environment. Using decidedly nonphotogenic setups of mostly lasers and big black boxes, Johnson\u2019s studies show how the behavior of these lab-based cloud particles mimics the behavior of cloud particles in massive sky-sweeping clouds, only in miniature.<\/p>\n\n\n\n<p>\u201cOf course, we don\u2019t grow them at quite the same scale you see in an atmosphere,\u201d Johnson said. \u201cInstead, we take one particle that is representative of a cloud, pump in different gases, change the temperature and pressure of the system. We then watch as that particle grows, shrinks or changes phase with time, all of which are processes that happen in clouds everywhere.\u201d<\/p>\n\n\n\n<p>The particles that act as the nuclei of Johnson\u2019s lab-grown clouds, like most particles, have a charge. Johnson and her team use an electric field to levitate and contain the individual particles so they can\u2019t move around. These particles are then stable for extended periods, which enables long-term research experiments \u2014 sometimes they stick around long enough to earn names. The scientists vary the pressure, temperature, electric field and laser illumination and study how the cloud particle reacts. Other methods build upon these to allow the team to look at groups of particles and observe how they scatter and polarize light.<\/p>\n\n\n\n<p>Johnson can extrapolate from these systems to understand how different conditions lead to certain cloud types and behaviors. Like aeronautical engineers using a wind tunnel to observe how currents move around structures, Johnson uses these particles to understand the microphysics that underpin vast and complex systems.<\/p>\n\n\n\n<p>Many scientists \u2014 climatologists, meteorologists and planetary scientists, to name a few \u2014 study clouds as part of their broader research. But Johnson is one of the few who studies the particular physics of clouds in the laboratory.<\/p>\n\n\n\n<p>\u201cThere are not many of us who dig into the small-scale processes of how clouds form,\u201d Johnson said. \u201cAnyone who studies the atmosphere has to have a general knowledge of clouds. But none of those systems work without the microphysics driving cloud formation and evolution. We have to understand these processes to truly grasp the complexities and implications at larger scales.\u201d<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Exoplanets under the weather<\/strong><\/h2>\n\n\n\n<p>It\u2019s a long-running joke that the nights of notable astronomical events on Earth seem to be almost supernaturally disposed to be cloudy. That is true of other planets, too. Humans awaited the April 2024 solar eclipse hoping for clear skies, not clouds, a hope that was rewarded in a wide swath of the U.S.<\/p>\n\n\n\n<p>But all too often, using enormous, advanced, vastly powerful telescopes, astronomers can peer through light-years of space just to find clouds blocking their view of the planet itself. Rather than the planet\u2019s surface, they can only perceive the opaque atmosphere that enrobes it.<\/p>\n\n\n\n<p>Every planetary body in the solar system that has a dense atmosphere, and many outside of it, has clouds in that atmosphere. Even bodies with thin, wispy or intermittent atmospheres \u2014 like Pluto \u2014 have particulates hanging in the atmosphere that, while not true clouds, are a haze of particles and share many of clouds\u2019 properties.<\/p>\n\n\n\n<p>\u201cClouds are a ubiquitous feature of planetary atmospheres,\u201d Johnson said. \u201cThis is something we\u2019ve seen from our own solar system, and when we look at exoplanet atmospheres, it\u2019s no surprise that we find clouds there too. Unfortunately, they tend to block our view of the atmosphere and surface that below.\u201d<\/p>\n\n\n\n<p>Scientists have been able to send probes and rovers to close planetary neighbors, including Venus and Mars. But for bodies that are farther away, including exoplanets \u2014 planets in other star systems entirely \u2014 scientists must come up with clever ways to conduct science.<\/p>\n\n\n\n<p>\u201cThe astronomers find the clouds to be an annoyance. They get in the way of the data they want, whether that\u2019s learning about the surface of the planet or its atmospheric composition,\u201d Johnson said. \u201cWe see it a little differently. Yes, they\u2019re there and we can\u2019t get rid of them. So let\u2019s use our understanding of clouds on Earth and planetary atmospheres of our solar system to learn about those things that we can\u2019t observe in exoplanets.\u201d<\/p>\n\n\n\n<p>Johnson and her team accumulate information about planetary bodies in Earth\u2019s solar system or exoplanets. Astronomers can collect spectrographic data to analyze the chemical compounds that make up the atmosphere and use mathematical models, observations and gravitation studies to determine a planet\u2019s mass, size and orbit. Combining that information with insights from her laboratory studies, Johnson can help astronomers determine what a planet\u2019s atmosphere and clouds might be and extrapolate its chance for hosting life \u2014 helping ground-truth telescope data.<\/p>\n\n\n\n<p>\u201cOur big questions are when, where and why do clouds form in these atmospheres?\u201d Johnson said. \u201cIf we want to understand these enshrouded exoplanets, we need to understand the clouds. That understanding gives us insights into the atmospheric chemistry at work, atmospheric circulations and the climate of these exoplanets. In a way, we ground-truth astronomical observations. The same physics is at work whether it\u2019s on Earth, in my lab or on an exoplanet. It\u2019s the same processes, all throughout the universe, and it brings me a huge amount of wonder and joy.\u201d<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>About Purdue University&nbsp;<\/strong><\/h2>\n\n\n\n<p>Purdue University is a public research institution demonstrating excellence at scale. Ranked among top 10 public universities and with two colleges in the top four in the United States, Purdue discovers and disseminates knowledge with a quality and at a scale second to none. More than 105,000 students study at Purdue across modalities and locations, including nearly 50,000 in person on the West Lafayette campus. Committed to affordability and accessibility, Purdue\u2019s main campus has frozen tuition 13 years in a row. See how Purdue never stops in the persistent pursuit of the next giant leap \u2014 including its first comprehensive urban campus in Indianapolis, the new Mitchell E. Daniels, Jr. School of Business, and Purdue Computes \u2014 at&nbsp;<a href=\"https:\/\/www.purdue.edu\/president\/strategic-initiatives\" rel=\"noreferrer noopener\" target=\"_blank\">https:\/\/www.purdue.edu\/president\/strategic-initiatives<\/a>.&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>WEST LAFAYETTE, Ind. \u2014 Every cloud is lined, not with silver, but with science \u2014 at least from cloud expert Alexandria Johnson\u2019s point of view. Clouds are ubiquitous. They are one of the most notable characteristics of planet Earth. Studying<\/p>\n","protected":false},"author":8,"featured_media":4895,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[19,7,524],"tags":[],"department":[32],"source":[29],"purdue_today_topic":[],"coauthors":[77],"class_list":["post-4894","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-general","category-research-excellence","category-space","department-science","source-purdue-news"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/posts\/4894","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/comments?post=4894"}],"version-history":[{"count":3,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/posts\/4894\/revisions"}],"predecessor-version":[{"id":8843,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/posts\/4894\/revisions\/8843"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/media\/4895"}],"wp:attachment":[{"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/media?parent=4894"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/categories?post=4894"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/tags?post=4894"},{"taxonomy":"department","embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/department?post=4894"},{"taxonomy":"source","embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/source?post=4894"},{"taxonomy":"purdue_today_topic","embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/purdue_today_topic?post=4894"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/coauthors?post=4894"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}