Come Rain or Shine

The Nitty Gritty of Dust

December 02, 2020 USDA Southwest Climate Hub & DOI Southwest Climate Adaptation Science Center Season 1 Episode 7
Come Rain or Shine
The Nitty Gritty of Dust
Show Notes Transcript

Drs. Dave Dubois, New Mexico State Climatologist, and Nick Webb,  research scientist  at the Jornada Experimental Range, discuss the nitty gritty of dust (pun intended). While it may seem dry (haha, okay we'll stop now), it's important to know about moving forward.  What weather conditions produce dust? What kind of modeling and monitoring projects are being implemented currently? They go over this and some speculations for the future. Photo courtesy of USDA ARS

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DOI Southwest CASC: https://www.swcasc.arizona.edu/

USDA Southwest Climate Hub: https://www.climatehubs.usda.gov/hubs/southwest

Sustainable Southwest Beef Project: https://southwestbeef.org/

Emile Elias: [00:00:00] Welcome to Come Rain or Shine, podcast of the USDA Southwest Climate Hub 

Sarah Leroy: [00:00:06] and the Department of Interior Southwest Climate Adaptation Science Center, or Southwest CASC. I'm Sarah Leroy Science Communications Coordinator for the Southwest CASC. 

Emile Elias: [00:00:17] And I'm Emile Elias, Director of the USDA Southwest Climate Hub.

Here, we highlight stories to share the most recent advances in climate science, weather and climate adaptation, and innovative practices to support resilient landscapes and communities. 

Sarah Leroy: [00:00:34] We believe that sharing some of the most forward thinking and creative climate science and adaptation will strengthen our collective ability to respond to even the most challenging impacts of climate change in one of the hottest and driest regions of the world.

Emile Elias: [00:00:56] Welcome to another episode of Come Rain or Shine. Today's topic is dust. Dust is more than just a nuisance. Airborne particulate matter can have impacts on local, regional, and even global scales and can be a hazard for health, visability, crops, and the environment. Of course, foremost in many people's minds right now are the air quality impacts we're seeing from wildfire smoke.

But wind erosion is in some ways, a more persistent problem. Today we're with two experts on wind erosion and dust measurement monitoring and modeling, Dr. Dave Dubois, New Mexico State climatologist, and Dr. Nick Webb, a physical scientist at the Jornada Experimental Range. Welcome. Thanks for being here.

Sarah Leroy: [00:01:41] Welcome Dave and Nick. Dave, you work more on the meteorological side of things. And Nick you've been involved with some cutting edge wind erosion modeling work, both important aspects of this issue. So Dave, maybe you could start us off with the weather side of things. You know, we know wind erosion is something that fluctuates.

Can you tell us how a dust storm forms and what factors dictate the intensity and duration of adjustment? 

Dave Dubois: [00:02:10] Yeah, I'm glad to answer that. So I mean, some of the ingredients you need for wind erosion of course are high winds, or at least the turbulent winds, and then maybe Nick can talk about the other components.

You know, maybe the dry soils, crusts that can break up that can release a lot of particles, but at least on the wind side, we look at the different drivers and then you can classify them. And it depends on the time of year. Even time of day, you can get local scale dust storms, from things like dry microbursts, when we get really dry surface area and we get some really gusty wounds from thunderstorm outflow.

And then in the spring time, we get these synoptic scale, when cold fronts swish through the area. We can get high winds. So it all depends on the area and even location to, proximity to mountains. Um, we get some in the summertime, we get storms pop-up and the outflow from the thunderstorms, create some dust locally and they may just, um, hit areas that are on the scale of, you know, 10-20 kilometers. Whereas the synoptic scale can cover much greater areas.

Sarah Leroy: [00:03:30] Great so do you think we might be seeing more or less of these events in the future?

Dave Dubois: [00:03:38] Yeah. Well, I think it depends a lot on area geographically, in some areas it's being driven by aridity producing warmer temperatures and, you know, where we get what we see, um, PM 10, PM 2.5 are some of the highest on when we have drought years.

And you see this all over the area and looking at visibility impacts when it's drier years, but we're also seeing trends. I know there was a publication in 2016 by Hand et al. saying that the spring dust seasons shifted earlier by one or two weeks. And so there's and, there's also some studies done - I was just looking at a 2018 Harvard paper looking at the, looking at the SPEI, the, the, Okay. That's combined precipitation and evapotranspiration, and they're predicting an increase in fine dust across the Southwest. So it all depends on where you are geographically. And there's some areas that are going to get wetter and some areas are going to get drier.

But even short term, when we have drought. Um, those are the times when we're going to see more, the likelihood of seeing more, uh, dust events, but it all depends on the, the drivers. So like this year is kind of an interesting, you know, we, in terms of the summertime monsoonal, we need more of those thunderstorm outflows in order to produce the dust.

So it's sort of a, you have to have both droughts drying conditions and the drivers to create that, the winds. So if you don't have the wind generator, um, then you have, you know, kind of a less probability of high winds and dust. So, um, it all, it really does depend, and I think there's a lot of work being done in that area.

I think that's kinda it's ripe for more research. 

Emile Elias: [00:05:30] Thanks, Dave. That leads me to a question that I've been thinking about and I wonder if you have just one word or phrase that describes this year's dust season, what would that be? 

Dave Dubois: [00:05:41] Well, for me, I would say just below par. We didn't have, I take a lot of pictures and photography of storms.

And I was, uh, I was really hoping for a lot more. And, uh, you know, it depends on what area of the state you're in. There were a few more on the East side of the state, but where I am here in Las Cruces, um, it was below par for me. 

Emile Elias: [00:06:04] Great. Thanks. And I want to ask Nick that same question. There's one word or phrase that describes 2020 in terms of the Dust season, what would that be?

Nick Webb: [00:06:14] I think it would be disappointing heavily for a few reasons. I think the same reasons as Dave, it wasn't a particularly dusty year here. Um, but also sort of on the research side of things COVID has made it extremely difficult for us to get out and do the field work that we need to, to really understand processes and support the work we're doing. So, yeah.

Emile Elias: [00:06:42] Great. So Nick, I wanted to ask you a little bit more, about sort of the key elements of dust emission. And we know that it's not just the weather events, as Dave mentioned um, that put dust in the air, but also where the airborne dust comes from to begin with. And I know you've been working for a while now on aeolian erosion to address the need for a generalizable, physically based wind erosion and dust emission model.

Can you tell us a bit more about that?

Nick Webb: [00:07:19] Yeah, certainly. So, Dave earlier mentioned the importance of wind and weather in driving wind erosion and dust emission. After wind probably the most important control is how much vegetation you have on the landscape because that can directly protect the soil. And it shelters the soil from the wind and can trap sediment that’s moving around. So vegetation of course responds to land management. So we're really interested in how we can develop a model that is very sensitive to changes in vegetation and soil plots across the landscape to predict where wind erosion and dust emission might be an issue.

Um, So for the last eight years we've been working on an aeolian erosion or AERO model and our objective or approach with developing this model, um, is to develop a tool that can both use and contribute to larger ecosystem monitoring datasets that agencies like NRCS, BLM, Forest Service, National Parks Service are all collecting across rangeland and grazing lands in the States. Um, so AERO uses, uh, indicators from these monitoring dataset maps, surface soil texture, amount of bare ground at the site, as well as information about the vegetation plot, and how its sort of arranged with its spatial distribution in the landscape, and it lets us predict at each monitoring plot what the sort of fluxes of erosion or sediment are. So we can predict the horizontal resulting flux of sentiment, which is how much sort of sand is moving across the landscape and that can be an indicator of site stability, instability. And we also predict what we call the site result dust emission. So we can look at particulate matter emissions, like PM 10 and PM 2.5 that are regulated by the National Ambient Air Quality Standard. So we can use monitoring data to produce sort of plot scale estimates, fluxes in sediment, dust emission of course is a good indicator of air quality, but it's also an indicator of the soil loss and nutrient loss from a site. Um, with the idea of being able to run a model on these monitoring data sets is that it allows us to sort of value add to them and enable producers and managers to assess wind erosion alongside other indicators of ecosystem services. So often these monitoring data sets are used to look at things like biotic integrity, um, soil and site stability, wildlife habitat, that kind of thing. And we really want to be able to sort of mainstream wind erosion information with these monitoring data sets so managers can see wind erosion alongside these other resource concerns.

Sarah Leroy: [00:10:19] Thanks, Nick. So my next question is for both of you really, um, what other monitoring or decision support tools do you know of that are available to end users interested in measuring, mitigating, or managing dust emissions? 

Dave Dubois: [00:10:39] There's a lot of work being done in using satellite imagery, resolutions of satellite imagery, or, you know, just like, um, your cell phone, the resolution and the quality are getting much better.

So there's, a lot of more, you know, really quick advances in, uh, you know, not only the technology, but the uses of the satellite imagery to, um, assess where wind erosion is taking place. And I was looking at some of these commercial satellite products and they're amazing, you know, where they can look at individual fields and tell you exactly where in the field, wind erosion is taking place.

Um, so that's one. And then there's um, in terms of the monitoring, we got, um, a, a great resource in the US uh, called the Improved Monitoring Network that basically they look at, um, um, aerosols across, um, not in the urban areas, but in the rural areas, protected areas. There's a nice, really long dataset and there's been some papers published on looking at trends, you know?

And one of the things that we're looking at is, um, you know, typically like in the Great Plains, there's, they're seeing a trend in the fine dust over the last twenty years. And so without that, those kinds of networks, we wouldn't really be able to sense those and, um, you know, be able to apply models that Nick was talk about in terms of management.

So we have to know the geographic areas that we're seeing as well as the timing and how bad in terms of the trends. 

Nick Webb: [00:12:30] Yeah, I think, um, the air quality monitoring networks and satellites that Dave just described have been a fantastic resource and are continuing to improve. What we have really been missing is an ability to connect how much dust is blowing around in the air to what are the conditions on the ground and why is it being emitted? Um, And sort of from that angle, a big focus of our work at the Jornada is looking at how we can connect dust in the air to vegetation and management on the ground. And one of those approaches is through the AERO model and another is sort of directly interpreting the large ecological monitoring data sets that we already have available to us.

Um, so I think a part of that is actually helping managers interpret the indicators that they already have about vegetation and soils so that they can understand how they relate to dust in the atmosphere. Um, one approach that we're taking to do that is, is, uh, helping to include interpretations of  wind erosion in ecological site descriptions, which are used by managers across rangelands to interpret how vegetation is changing in response to management.

Um, and if we can include more interpretation and information about wind erosion in that it will help managers to identify where they can adopt conservation practices that might be appropriate with helping to reduce air quality impacts. 

Dave Dubois: [00:14:10] Yeah, these are real important because, um, we get a growing increase in visibility in terms of the health, the human health impacts, from wind erosion.

Um, you know, I was reading a paper recently looking at the Valley fever, um, extending north in terms of the endemic areas. So if we get a handle on that integrated approach, Um, we can, you know, help out the health community by, by, by looking at, you know, uh, what are some of the, um, um, the drivers and how can we monitor areas that, you know, we're, um, building up very close to agriculture areas when we build our, um, expanding urban areas.

So there's this great need for that kind of work. 

Emile Elias: [00:14:58] Thanks. And that makes me think of some of the national monitoring networks as well. And Nick, I know that you lead or direct the National Wind Erosion Research Network. I wonder if you can tell us a little bit about what that is.

Nick Webb: [00:15:12] Yeah, certainly! Um, we established the National Wind Erosion Research Network in 2014 and it's a multi-part directive, so it involves a number of agencies. Uh, the USDA through NRCS and ARS. It's part of the ARS' Long-Term Agro-ecosystem Research Network, uh, also the Bureau of Land Management, Department of Defense, USGS, and the Nature Conservancy have been involved.

Um, and the objective of the network, uh, is really to, uh, establish a set of focus research sites that enable us to collect really detailed information about  wind erosion and dust emission processes across different agro-ecosystems, uh, under different management conditions. Uh, and use that information to support more basic research, uh, into how wind erosion and dust is responding to management in different landscapes, as well as development of decision support tools, like the AERO model, uh, the Wind Erosion Prediction System, or WEPS, which is widely used by NRCS to support wind erosion assessments, uh, as well as to really facilitate collaboration on wind erosion and dust issues across the partnered agencies. So we're continuing to expand the network, continuing to think of research questions, and yeah, it's really exciting.

Emile Elias: [00:16:48] Thanks Nick. Dave did you have anything to add? 

Dave Dubois: [00:16:51] Well, no, I mean just, um, you know, dust has many other impacts. I know I work in an area where we look at impacts to transportation. You know, there's, there's some hotspots that we're very concerned about all over and there’s actually hotspots, all over the West, Western US. And, uh, here in New Mexico, we've been working on one on I-10 and looking at, and actually, Nick has one of his network sites there.

And to help out in his endeavor to look at, um, the frequency, intensity, duration of dust storms, um, on the Lordsburg Playa, and, um, in those actively working on a mitigation on that. And, um, you know, basically protect, uh, the people driving on I-10 who may not be aware of the hazards in that area.

So there's a lot of work to be done to increase, uh, and make the areas more resilient to extreme weather events, and that's kind of the, one of the goals of our work is to provide the instrumentation knowledge and translate that into things that, uh, you know, like transportation departments can use actively and, you know, use some of the tools and that they, that they normally use. But use it more smartly in terms of providing the work, you know, how do we warn people? And I mean, there's just, there's a social part as well that we need to be thinking about, it's not only just the physical science, but there's, how do we behave and manage and conduct our lives in a little safer when there's these events that occur.

Emile Elias: [00:18:29] Thanks Dave. And that actually reminds me of the Dust Mitigation Handbook that both you and Nick contributed to and how that links with agricultural producers and provides them with some options for, um, trying to minimize dust emissions and wind erosion from their lands. And it also makes me think of a recently published article in geophysical research letters that links dust impacts with rapid agricultural expansion in the Great Plains. The authors of that article state that throughout the US Great Plains, satellite data combined with surface networks have shown a significant increase in airborne dust over the last two decades.

And this airborne dust is negatively influencing both human health and visibility, and it coincides with these increases in agricultural production. And so I wonder, do you think that we're entering into a dustier future? And if so, besides the Dust Mitigation Handbook, what can land managers do? 

Dave Dubois: [00:19:37] With drought becoming more frequent and they're actually hotter droughts than they used to be, like the fifties droughts.

And so, so they're- we're stressing not only the evaporation from just the temperatures, but, um, you know, the evapotranspiration is a big, big deal. I know that, um, we were seeing it this year. Um, with, you know, in New Mexico, August was like the hottest on record. And, um, we're seeing the evapotranspiration, you know, stress, the plants, um, very high.

Um, so there's the natural and the, you know, human induced changes, but there's also the social part that you know, that we're dealing with drought and um, you know, fallow agricultural areas, you know, so there's, decision-making going on that, um, you know, that are, may not be anticipated. Um, you know, we're seeing those in other places, you know, where there's lack of, of irrigation.

So, um, some people can afford to pump water out of the, uh, at a groundwater and some can't. And so there that, that, um, produces a dust source and we're seeing that in Mexico, you know, and a lot of the dust that we get here in Southern New Mexico is from, um, Chihuahua. And so, um, so it's not only the U S decision-making but international is, is big deal.

So, um, you know, I think there, the risk is high in terms of, um, in the future to look at, um, I've, you know, talked around with my colleagues, you know, aridification is one of the words that we've, we talked a lot about in terms of drying of the, uh, the whole, um, water basin and, you know, and, and even, uh, you know, the end product, you know, desertification is even being brought up, um, and you know, talked about cause it's, it's happened before and it's, you know, in China we've seen that occur and, uh, where they had to, I mean, they've, they took over entire towns and desertified it. And, you know, we in looking back and learning from those, how can we manage, um, our systems and not get to that point?

You know, I think. We've got a lot of history and knowledge in this, you know, things that Nick's been working on are really going to transform our look at things, but we have to use them and it has to get to the decision makers in order to make it so that, you know, even if, even if it does get more dustier and it's likely, um, but we have to be able to manage and become more resilient and, uh, adapt to these changes so that we don't really see the impacts that we're, I hope these papers are wrong! That's kinda, my goal is, um, but we, we we're, we're seeing the, you know, getting a glimpse of the future and we have to, have to make those course corrections now, before we, we see them, we can't wait until we see them and do those things. 

Nick Webb: [00:22:33] Yeah. I think that a lot of the management options that might be available to producers are going to become, more and more difficult to implement on the hotter and drier droughts. So probably the most effective strategy and anticipatory strategy is to ensure that we really maintain our land in a healthy, productive condition now and avoid the sorts of state changes that we might regard as desertification. Um, that's perhaps easier said than done in some areas I think in rangelands that means, you know, taking whatever measures we can to ensure that we maintain our perennial grass cover, where we can, um, or avoid transitions of our landscapes to more degraded states, losing our grasses, perhaps could increase or accelerate wind erosion and, and further perpetuate those changes. Um, that's a big issue here in the Chihuahuan desert.

Um, I think in croplands, um, I mean the most basic way to control wind erosion is to maintain surface cover. So in some cases that may be achievable through some minor changes to practices. In other cases it may mean looking at alternative crop varieties and that kind of thing that enables us to maintain ground cover at critical times of the year when it's windy.

Um, I think sort of in all of this, um, what's going to be really important is us as scientists and the agencies, equipping managers with the information that they need to, um, make informed decisions. Um, we really still know fairly little about which landscapes are eroding in the US when, why and how much, and really building that sort of knowledge base understanding of what's going on, is going to be important. And then getting that information out to managers along with tools that help them interpret wind erosion information to support decisions is going to be really critical. 

Sarah Leroy: [00:24:41] Thanks, Nick. That's a, that's an excellent thought.

Um, and I just want to open it up to both of you. If you have any other final thoughts before we wrap this podcast up. I'll take that as a no.

Well, I think that's a great point to end on anyway, isn't it. Um, so we appreciate both of you being here with us today. And yeah. Thank you very much.

Emile Elias: [00:25:11] Thanks for listening to Come Rain or Shine, podcast of the USDA Southwest Climate Hub 

Sarah Leroy: [00:25:17] and the DOI Southwest Climate Adaptation Science Center. If you liked this podcast, don't forget to subscribe, like, or follow for more great episodes. If you want more information, have any questions for the speakers, or would like to offer feedback, please visit climatehubs.usda.gov or swcasc.arizona.edu.

Emile Elias: [00:25:51] Our sincere thanks to USDA Agricultural Research Service, the Sustainable Southwest Beef Project and the US Geological Survey for supporting this podcast.