Aerosols strengthen storm clouds, according to new study


An abundance of aerosol particles in the atmosphere can increase the lifespans of large storm clouds by delaying rainfall, making the clouds grow larger and live longer, and producing more extreme storms when the rain finally does come, according to new research from The University of Texas at Austin.


New research from the University of Texas at Austin shows that aerosols create larger storm clouds capable of producing more rain. CREDIT Brian Khoury

The study, published in the journal of theProceedings of the National Academy of Sciences on June 13, is the first to address the impact that aerosol particles have on the lifespans of large thunderstorm systems called mesoscale convective systems. These storms are complex, often violent systems that can span over several hundred kilometers. The systems are “the primary source of precipitation over the tropics and mid?latitudes, and their lifetime can have a large influence on the variability of rainfall, especially extreme rainfall that causes flooding,” noted the paper.

The research, led by scientists from The University of Texas at Austin Jackson School of Geosciences, looked at satellite data from 2,430 convective cloud systems and found that aerosols can help increase the lifespans of convective cloud systems by as much as three to 24 hours, depending on regional meteorological conditions.

“A cloud particle is basically water and aerosols. It’s like a cell. The aerosol is the nucleus and the water is the cytoplasm,” said lead author Sudip Chakraborty, who recently received his Ph.D. from the Jackson School. “The more aerosols you have, the more cells you get. And if you have more water, you should get more rain.”

Researchers from the University of Colorado Boulder and NASA’s Jet Propulsion Laboratory also worked on the study.

Aerosols are minute particles in the atmosphere that form the nucleus within a cloud around which water condenses to form the cloud. Aerosols can come from natural sources such as volcanic eruptions or desert dust, or human-made sources such as the burning of wood, coal or oil.

This study is the first to try to look at aerosols’ relative importance in the lives of storm clouds compared with meteorological conditions such as relative humidity, available convective energy and wind shear, said Rong Fu, a professor in the Jackson School Department of Geological Sciences and co-author of the study. Although meteorological conditions remain the most important element in the lifetime of a convective cloud system, Fu said the research shows that aerosols have a significant impact.

One of the difficulties in conducting this type of study, Fu said, is that the satellites that give data on cloud aerosol content generally pass over the same spot on Earth twice a day, which doesn’t provide enough data on the lifetime of a convective cloud system. Chakraborty was able to break new ground by turning to data from geostationary satellites that fly much higher and stay in the same location relative to the Earth’s surface.

“He painstakingly matched the geostationary satellite data, which gives you some information about the lifecycle of the convective systems, with data from the polar orbital satellite that passes by twice a day,” Fu said. “He really raised the bar for how we analyze satellite data.”

Professor Daniel Rosenfeld of the Hebrew University of Jerusalem, one of the world’s leading researchers in the field, said that aerosols’ effects on deep convective clouds and climate have been major questions for more than a decade. Of particular interest is the role of clouds in reflecting solar radiation and emitting thermal radiation to space, which can influence the radiative balance in the atmosphere and the Earth’s temperature. This study, Rosenfeld said, significantly advances the science.

“This is the first study that shows the full lifecycle of convective clouds in a statistically meaningful way on a climate scale,” said Rosenfeld, who did not work on the paper. “This is an important step towards determining the impact of clouds on radiative forcing. The next step is to quantify.”


41 thoughts on “Aerosols strengthen storm clouds, according to new study

  1. “He painstakingly matched the geostationary satellite data, which gives you some information about the lifecycle of the convective systems, with data from the polar orbital satellite that passes by twice a day,” Fu said. “He really raised the bar for how we analyze satellite data.”

    Oh painstaking. Like he actually did some research. In view of the last 30 years of climatology that is ‘raising the bar’ I suppose.

    and their lifetime can have a large influence on the variability of rainfall, especially extreme rainfall that causes flooding,” noted the paper.

    Now maybe the press release is not accurately representing what the paper but note that they don’t miss the chance to play the ‘extreme weather’ card.
    As usual no link to the actual paper to see what it actually says.

  2. Not to mention that secondary cosmic rays are
    another source of tropospheric cloud aerosols,
    so I won’t. Nor will I mention turpenes over forests.

    • Yeah, well done. Why don’t you just go ahead and start making a handy list of those areas of inquiry that may need to have their funding scaled back in order to protect the “climate consensus”!!
      Plus, people are obviously not to be blamed for turpenes from trees or cosmic rays from space.
      So, what would possibly be the merit of concluding that such things may influence the climate?
      Your theories could take environmentalists back 30 years.
      They’d be trying to save the rainforest again.
      But, this time, they’d be trying to save the rainforest in order to save the Polar Bears.
      Nothing, now, would surprise me!!

    • Yes – my first thought too. If this hypothesis should be correct, it would fit nicely with the Svensmark effect and its recent confirmation by the CLOUD team of CERN. (At least for the pre-industrial period following Kirkby et al. “Ion-induced nucleation of pure biogenic particles” Nature, Doi 10.1038/nature17953 (2016))
      And that could explain why the colder periods of the Holocene (going together with a lower sun activity and therefore more cosmic rays and hence more naturally induced aerosols) were stormier than warm ones, as it is e.g. shown in this study:

    • How do aerosols make heavy rain without water ??
      Aerosols; AKA ” DUST ” can turn H2O vapor into H20 liquid, or H2O solid, both of which can form clouds; meaning lots of water drops or ice crystals. Those can fall to the ground as rain or hail or sleet. Aerosols CANNOT turn Nitrogen, Oxygen or Argon, into heavy rain.

  3. So the real science is progressing at its normal stately pace.
    I predict that by 2100 we will be likely to have learned enough about the climate system know, by then, why all of the previous predictions regarding the climate system were wrong.
    Predictions made in 2100 regarding the development of the climate towards 2200 are quite likely to me more accurate and more cautiously communicated.
    We are living in the age of bold over-confidence. Arrogance even.
    Aerosols and cloud formation could conceivably reveal themselves to be one of the dominant factors driving long-term climatic shifts. Or even, THE dominant factor. But, then again, maybe such thinking will turn out to lead nowhere.
    More science needed.
    But while we wait – let’s all just go completely mad and desperately panic about things that we don’t yet understand.
    (Sarc. – last sentence only).

  4. This topic has already lead me to the slightly refreshing discovery that NASA is permitting some person to make realistic statements regarding what we do and do not understand about the role of clouds.
    This from NASA ISCCP:
    “The ways that clouds respond to changes in the climate are so complex that it is hard to determine their net effect on the energy and water balances and to determine how much climate might change.”
    “The global climate is such a complex system that no one knows how even a small increase in temperature will alter other aspects of climate or how such alterations will influence the rate of warming. Moreover, changes in any of these climatic features may also affect the distribution and properties of clouds , but the understanding of clouds is so rudimentary that no one knows whether climate feedbacks involving clouds will dampen or amplify a warming trend.”
    And then, that analysis, which states uncertainties of great magnitude or of sign does not consider the role of aerosols.
    SO if we add aerosols into the mix then we know even less about the thing that we already knew that we didn’t know very much about!!

    • Gotta love the language of cause and effect:
      “The ways that clouds respond to changes in the climate are so complex that it is hard to determine their net effect on the energy and water balances and to determine how much climate might change.”
      Reads to me like chicken-and-egg… Climate change changes clouds in a complex, not-understood manner leading to undetermined changes to climate.

  5. But I thought that cloud seeding to increase the aerosols in a cloud was intended to make it rain sooner rather than later. What am I missing?

    • It is all about particle size. The smaller the particle the more stable the raindrop, plus dispersion.
      For example, if a cloud is spread out because of aerosol distribution the moisture is spread out, as in that white haze we see much of today, even now as I type there are straight lines (clouds?) going for miles along flight paths from Helsinki Airport, created by contrails apparently.
      So what is going on with aviation fuel? It has changed. I’d heard 30 year serving United pilots say contrails just dont last for hours and spread out and turn into clouds. This is what we are seeing though. As here×8091.gif?
      If there is more moisture being suspended artificially on a large scale, then it is certainly going to affect weather.×8091.gif?w=720&h=569

      • I dont believe in coincidences, those images look like SRM is already being carried out.

      • What IS up with the jet fuel, Mark?
        Skeptics may claim contrails have always “spread out” but that is not accurate. Back in the day, contrails sublimated — they were composed of ice crystals. I may be wrong about this, but I think the efficient jet engine introduced in the late ’70s did not produce nearly as much condensation vapor as the preceding design; as a result, contrail phenomena decreased in the ’80s. Beginning in the ’90s, contrails increased and they began almost invariably to “spread out.” Something had changed.
        The mystery is, why aren’t ALL the jets at cruising altitude emitting contrails on those days when spreading jet exhaust occludes the sky? UN climatologists have lately taken notice of these “persistent” contrails as a possible factor in “Climate Change(tm),” though they don’t claim to understand their effect. Indeed, are those jets that produce persistent contrails using a different sort of fuel?

      • “For example, if a cloud is spread out because of aerosol distribution ”
        Calling bull-hockey on this; additional aerosols WON’T materially change cyclogenesis and the formation of rotating cumulus which form the heart of a mesocyclone which which is the heart of said convective system …

    • Mark in Helsinki: What have contrails got to do with my question which is about cloud seeding and the apparent contradiction with the reported results of this research?
      As for your comment that contrails do not last for hours and spread out, yes they can and do. It all depends on the meteorological conditions close to the tropopause where they form.

      • Jet aircraft do not burn coal, which is mostly carbon that turns into CO2 and is invisible. Most modern jets burn hydrocarbons, which turn into CO2 which is invisible and water vapor, which is also invisible.
        The water vapor part of the jet exhaust is very hot, so it stays invisible until it cools down. It cools down because the surrounding atmospheris is sub zero Temperature and might be -40, -50, or -60 deg C, or even -30 deg C.
        But the atmosphere there is very sparse, so the H2O molecules spread out so that their partial pressure is low. If it doesn’t get above the equilibrium vapor pressure at that Temperature, then the H2O remains invisible vapor.
        If the partial pressure of H2O gets above the equilibrium value, we can say that it is at the dew point or thereabouts, and solid or liquid particles of water can form and those are visible.
        You are seeing the visible part of jet engine exhaust waste products.
        What’s the big deal. You can see the H2O sometimes, but you can’t see the CO2.

  6. Storms are formed in oceans and move on to land. Cloud condensation nuclei — such nuclei are largely particles of sea salt.Mason in 1957 estimated that the bursting of minute bubbles from the sea surface might produce 1000 nuclei per square cm per sec. This is natural part. Other types of aerosols are short lived [with the type of wind they washed on to the ground in no time] with limited impact on cloud formation and thus cyclonic activity.
    Dr. S. Jeevananda Reddy

    • “Storms are formed in oceans and move on to land.”
      I’ve seen squall lines/entire thunderstoem complexes develop out of ‘thin air’ as the dry line approached the western edge of Dallas (Texas) in the afternoon.

      • _jim — storms are different from local thunderstorms that form instantly and disappear instantly. Few days back Hyderabad City in India [where I live] experienced such thunderstorms with devastating effect on trees but they are highly localized. Cyclonic storms — tropical storms, hurricanes & typhoons] form in ocean and not on land as they need moisture feed back.
        Dr. S. Jeevananda Reddy

  7. War on Farmers: A few years back I read an article about EPA wanting to regulate dust. This study sounds like ammunition for their goal.

  8. Finally…!
    Anthropogenic Climate Science News We Can Use
    second article this year!
    Warm up, you cool too fast
    gotta make this crisis last… just
    Kickin’ down the Arctic chill
    fishin’ for fear and fleecin’ boobies!
    Got no axe to grind
    no temperatures to fix
    I’m gladdened and happy
    in this Ice Age betwixt
    Let La Nina drop little snowflakes on me
    CO2… I love you!
    All is nom-i-nal….


  9. Clouds have a great deal of effect on climate, and this reveals we don’t know all that much about cloud behavior. So the climate models are accurate enough to set policy on energy use, but ignore a major factor./sarc

  10. Bottom line: cloud seeding causes rain. Lots of seeding, from whatever source, causes bigger storms, more rain, and lots of hail.
    Been there. Done that. Don’t fly near TSTMs in/around the MARFA Front.

  11. “The more aerosols you have, the more cells you get. And if you have more water, you should get more rain.”
    Only until there is no more water vapour. This statement reads as if there is an unlimited source of water vapour.
    I note that a major form of aerosol is missing from the conversation: H2S from the ocean. This is a significant source of cloud condensation nuclei (CCN). Anything including a ten nanometer water droplet serves as a raindrop formation particle. Farmland is a major source of particles as are forests. Think of the ‘blue’ in the Blue Ridge Mountains. Those are particles formed from tree emissions. Forest fires are majors contributors as well. There are thousands of them a year.
    I wonder if the GCR was factored out of the cloud cover and cloud formation. The satellite data is available to enable this. It would be a bit of a let down if it turns out the aerosol effect was significantly affected by GCR and proportionately less by ‘natural’ aerosols.

    • Does anybody have a graph of the distribution of the size of either water droplets or ice crystals in clouds. In other words, what is the minimum to maximum size range of visible cloud particles, either solid or liquid ?? are they angstrom size or are they centimeter size; or possibly something in between.
      I know a hydrogen atom is a few angstroms diameter, but how big are raindrops ??

  12. It’s an interesting claim in light of cloud seeding, which adds silver iodide to the atmosphere. The Snowy Mountains Authority in Australia says that between 2004 and 2012 an average of 20kg of silver iodide was used per season over 2000 square kilometres and it caused an average of 14% more snow under suitable conditions. (Ref “Snowy Hydro News”, July 2013). If an increase in aerosols produces longer-lasting clouds that have moe rain or snow, then it follows that a decrease in aerosols will have the opposite effect.
    Doesn’t that mean that when governments legislate to reduce aerosol emissions and developing countries switch from burning dung and wood to the bottled gas, with its less aerosol emissions, then total cloud cover will be reduced? And won’t a reduction in cloud cover mean higher temperatures, and while there will be more heat to lose via LWR at night, some of that extra heat won’t be lost because it’s been absorbed.
    That’s what I argued here on this blog after my 2014 paper suggested that reduced cloud cover, especially at low levels, was a likely cause of warming from 1987 to 1997.

    • John McLean — You noted that “caused an average of 14% more snow under suitable conditions” — What are those suitable conditions? Those suitable conditions might have given more snow than with cloud seeding? How, anybody say such statements. You can take the case of China Olympics — Chinese government undertook cloud seeding operation to see no rain in sports arena. That means, the downwind direction of seeded area will not get any rain by making clouds pre-mature and rain and dissipate. With this the farmers in downwind direction fought with the government for depriving the rains for their crops by cloud seeding.
      Dr. S. Jeevananda Reddy

  13. Please. By definition a cloud is an aerosol, regardless of how it is formed. An aerosol is simply a condensed particle suspended in a gas or a mixture of gases.

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