MAKE IT RAIN: THE SCIENCE BEHIND ALTERING THE WEATHER DARREL BAUMGARDNER MAKE IT RAIN: THE SCIENCE BEHIND ALTERING THE WEATHER WHENEVER HUMANKIND BELIEVES IT HAS CONTROL OVER THE NATURAL WORLD, THE WEATHER LIKES TO PROVE US WRONG. STORMS, FLOODS AND DROUGHTS ARE JUST SOME OF THE WEATHER PATTERNS THAT CAN COMPLICATE OR EVEN THREATEN HUMAN LIFE. WE HAVE INCREASINGLY SOPHISTICATED TECHNIQUES FOR WEATHER FORECASTING, BUT NOW SCIENTISTS ARE LOOKING EVEN FURTHER: TOWARDS DARREL BAUMGARDNER, OF THE DIRECTLY MODIFYING THE WEATHER ITSELF. AND DROPLET MEASUREMENT NATIONAL AUTONOMOUS UNIVERSITY OF MEXICO TECHNOLOGIES, RESEARCHES THE INTRIGUING TECHNIQUE OF CLOUD SEEDING TALK LIKE AN ATMOSPHERIC SCIENTIST GEOENGINEERING – deliberate, large-scale intervention in the Earth’s climate system, usually to mitigate climate change. CLIMATE – the general weather conditions over a long period. ICE NUCLEI (IN) – similar to CCN, particles in the atmosphere that ice crystals form around. CLOUD CONDENSATION NUCLEI (CCN) – small particles around which water vapour condenses and ultimately forms clouds. PRECIPITATION – water that falls from clouds to the ground, such as rain, hail, snow or sleet. CLOUD SEEDING – intentionally adding CCN to the atmosphere to change precipitation patterns. SPECTROMETER – an instrument that measures spectral properties, such as the reflective properties of cloud particles. DISDROMETER – a ground-based instrument to measure precipitation properties. WEATHER – the state of the atmosphere of a particular area at a particular time. Rain, or the lack of it, can cause problems. of investigating clouds, not only how they vapour in the atmosphere condenses into Too little rain can lead to droughts, which form but also how humans can influence clouds, but this process can only occur carries risks of crop failure and scarcity of their formation. As well as working with the presence of cloud condensation drinking water. Too much rain can cause within academia, he is the founder and nuclei (CCN). These are essentially small flooding and other forms of precipitation, Chief Scientist at Droplet Measurement particles of any number of substances, such such as hail, can cause physical damage to Technologies, which provides scientific as dust, soot or salt. To transition from a gas crops and property. Being able to influence instruments and expertise to researchers to a liquid, water molecules have to have when, where and how much rain falls could investigating aspects of cloud formation. something to cling onto, and CCN fulfil help prevent these negative effects. this function. Ice nuclei (IN) are the CCN WHAT IS CLOUD SEEDING? equivalent for the formation of ice crystals in Darrel Baumgardner has made a career A key step in the water cycle is when water the atmosphere. DARREL BAUMGARDNER National Autonomous University of Mexico and Chief Scientist at Droplet Measurement Technologies, Longmont, Colorado, USA FIELD OF RESEARCH Cloud seeding is a human-made technique that how they will respond to seeding, there are Atmospheric Science adds extra CCN or IN into the atmosphere, many factors to take into account, and at which can either enhance or suppress many different scales. For instance, the precipitation, depending on how, when and nucleation of cloud droplets around a CCN RESEARCH PROJECT where it’s done. This technique was famously happens at the microscopic level and in a used to keep the 2008 Beijing Olympics dry: matter of milliseconds, whereas the time to Investigating how clouds form, rockets containing silver iodide particles (a grow to visible raindrops (and eventually entire and how we can influence type of IN) were fired into the atmosphere, clouds) can take minutes to hours. When this their formation. intercepting incoming rainclouds and triggering is expanded to include the interconnected premature showers before they could reach cloud formation over entire regions, it gets the capital. complicated very fast. HOW CAN YOU MEASURE SUCH A However, this complexity is not COMPLEX SYSTEM? insurmountable. “Modern computers have Atmospheric science is very complex, and provided cloud modellers with the tools needed scientists simply don’t have all the information to create such models,” says Darrel. Model required to guarantee that cloud seeding will inputs include temperature, pressure, relative news for coral reefs and other underwater have the intended effect. In some instances, humidity, CCN and IN specific to a certain ecosystems. One project is looking into cloud seeding can even lead to the opposite time and area, and then different seeding seeding stratus clouds over the Great Barrier effect to that intended. There is also a certain scenarios are run to see how they affect cloud Reef, which would deflect sunlight away from lack of control. “Once the seeding material properties. As with any model, it remains a the sea’s surface and mitigate warming in that is released, there is nothing more that can be simplified representation of the real world, so area. In theory, this practice could be carried done,” says Darrel. results aren’t perfect, but are getting more out worldwide. precise all the time. Measuring cloud properties, and how they However, given the complex nature of react to different conditions, is essential. THE BIGGER PICTURE atmospheric science, geoengineering efforts “There are two general types of instruments Cloud seeding could help mitigate against on a global scale pose many challenges for used to measure cloud properties,” says droughts, floods and even air pollution, but scientists. For example, stimulating rainfall Darrel. The first are called disdrometers, and there are, perhaps, even bigger and more long- to alleviate drought in one area could lead to measure precipitation at the ground, including term applications. Geoengineering is the name extreme monsoons in another. Experts in this variables such as drop size, velocity and type of given to techniques that aim not just to alter field are mindful that they need to consider precipitation. The second type measures the the weather but also the climate, to attempt the intricacies of the bigger picture. As Darrel properties of clouds themselves and are called to counteract the effects of climate change. explains, with processes such as cloud seeding, spectrometers. By fixing a spectrometer to an When carried out at a global scale, cloud there is always the, “Goldilocks conundrum” aircraft or drone and flying it through a cloud, seeding and similar techniques are the most and the challenge is in getting things ‘just scientists can record cloud water content significant of these proposed measures. right’. He adds, “As atmospheric scientists, we and a number of other variables. Similar know that climate change is real.” Scientists measurements can also be taken from a great “Geoengineering has the potential to offset like Darrel can make a huge difference to our distance, using radar or even satellites. the negative impacts of climate change,” says world – will you be one of them? Darrel. For instance, one effect of climate HOW CAN SCIENTISTS MODEL CLOUD change is the absorption of the sun’s heat by PROPERTIES? the oceans, which raises marine temperatures When it comes to modelling clouds to predict and can lead to ocean acidification – bad ABOUT ATMOSPHERIC SCIENCE WHAT IS ATMOSPHERIC SCIENCE? instruments,” says Darrel. “We can also run know that climate change is real and is the Atmospheric science studies the layers of gas computers hundreds of times more powerful greatest danger that the world faces today,” that surround the planet, specifically their than just a few decades ago.” These huge says Darrel. Not only does atmospheric chemistry and their dynamics. This includes advancements mean that understanding of science provide us with much of the data interactions within the atmosphere, and atmospheric science is accelerating. “We about climate change – its predicted evolution between the atmosphere and other entities, know so much more about how clouds evolve and effects –, it also suggests ways we could such as the ocean or human activity. than we did 50 years ago, but we still have a protect ourselves against it. long way to go before we can truly ‘control’ Our atmosphere is the relatively thin barrier weather,” says Darrel. Atmospheric science has a huge amount to that separates the Earth’s surface from space. teach us about the present and the future of “Although the atmosphere makes up a small WHAT ARE THE REAL-WORLD our planet, and a career in it could have far- fraction of the Earth’s volume, it is critical to APPLICATIONS OF ATMOSPHERIC reaching positive impacts for society. life, not only for the oxygen we need but also SCIENCE? for the hydrological cycle.” The science that Weather forecasting, although it might seem attempts to explain it is complex and detailed, a rather bland aspect of everyday life, has the but has come on in leaps and bounds in recent potential to save countless lives. Forecasting decades. tropical storms, tornados or hurricanes, for instance, can help people prepare and HOW HAS THE FIELD CHANGED OVER safeguard themselves and their livelihoods. THE YEARS? “We are now able to make faster and more Atmospheric science also underpins much Seeding material is dispensed by burning flares like accurate measurements with much smaller of what we know about climate change. “We those seen attached to the trailing edge of the wing of this seeding aircraft. How to become an atmospheric scientist • According to NASA, a career in