Severe forest and peat fires in Indonesia have occurred more frequently in recent years. These fires have been associated with various types of ecosystems and land uses, ranging from the simplest to the most complex ones. However, recent fire control efforts in the country have primarily focused on fire suppression efforts instead of preventive measures. Fire prevention efforts are mostly statements of empty jargon rather than specific actions or policies. Fire suppression activities have been greatly preferred but have proceeded without properly accounting for whether the fires are on mineral soils or occurring within peat soils. Efforts to extinguish fires should be based upon their typology to be effective, especially for peat fires that having the distinct behavior of smoldering within the peat soils. However, field observations have shown that generalized approaches for extinguishing fire are undertaken on bot mineral soils where flaming surface fires predominate and peat soils where smoldering ground fires are common. Peat fires cannot be extinguished using the same suppression measures used for flaming surface fires and will, therefore, not achieve effective results without consideration of their unique burning typology. The severe peat fires in 2015 should be taken into account as a lesson learned and impetus for better peat fire control and prevention in the future. Keywords: Peat fires, fire typology, fire control, fire prevention

With temperatures rising in Arctic regions at double the global average, decomposition rates and subsequent greenhouse gas release into the atmosphere are expected to rise, potentially shifting these regions from carbon sinks to carbon sources. General circulation models predict the relationship between respiration and temperature using exponential functions, showing a temperature-independent rate of increase to decomposition rates with temperature. However, enzymes catalyzing carbon depolymerization reactions have demonstrated departures from this predicted increase between 10 and 15 °C. Organic tundra soils were incubated across this range (4 to 20 °C, 4 °C increments) and harvested consecutively after carbon losses equivalent to those after 2, 4, 8, and 12 days at 20 °C. During each harvest, β-glucosidase (BG) and β-xylosidase (BX) activities were measured at both the incubation temperature and at 20 °C to determine temperature limitations to enzyme activity and production. While enzyme activities in soils incubated at different temperatures diverged significantly when measured at different temperatures, these differences were overcome when measured at 20 °C, suggesting enzyme activities are more limited than enzyme production. Two exceptions to this trend were the first harvest of the 4 and 8 °C incubations, which had significantly higher BG and BX activities when assayed at 20 °C than soils incubated at higher temperatures, indicating larger enzyme pool sizes in soils incubated at lower temperatures. For BG activities, increased enzyme pool size offset low temperature limitations to enzyme activity, resulting in no difference in measured rates when the 4 and 8 °C soils were compared with the 12 and 16 °C soils, respectively. However, in subsequent harvests, BG and BX activities measured at 20 °C declined and activities at 4 and 8 °C were significantly lower than in assays at 12, 16, and 20 °C. Declining activities of these enzymes in the 4 and 8 °C incubations may indicate limited substrate accessibility or nutrient availability at lower temperatures due to changes in the relative rates of other decomposition reactions with temperature. Improving our understanding of the multifaceted impacts of temperature on decomposition reactions will be important to better model and predict future carbon release.

A number of studies in recent years have reported about the lunar tidal enhancements in the equatorial electrojet (EEJ) from ground- and space-based magnetometer measurements during stratospheric sudden warming (SSW) events. In this study, we make use of the ground magnetometer recordings at Huancayo observatory in Peru for the years 1978 – 2013 to derive a relationship between the lunar tidal enhancements in the EEJ and tropospheric eddy heat fluxes at 100 hPa during the SSW events. Tropospheric eddy heat fluxes are used to quantify the amount of wave activity entering the stratosphere. Anomalously large upward wave activity is known to precede the polar vortex breakdown during SSWs. We make use of the superposed epoch analysis method to determine the temporal relations between lunar tidal enhancements and eddy heat flux anomalies during SSWs, in order to demonstrate the causal relationship between these two phenomena. We also compare the lunar tidal enhancements and eddy heat flux anomalies for vortex split and for vortex displaced SSWs. It is found that larger lunar tidal enhancements are recorded for vortex split events, as compared to vortex displaced events. This confirms earlier observation; larger heat flux anomalies are recorded during vortex split SSW events than the heat flux anomalies during vortex displaced SSW events. Further, the temporal relations of lunar tidal enhancements in the EEJ have been compared separately for both the QBO phases and with the phases of the moon with respect to the central epoch of SSWs by means of the superposed epoch analysis approach. The EEJ lunar tidal enhancements in the east phase of QBO are found to be larger than the lunar tidal enhancements in the west phase of QBO. The phase of moon relative to the central SSW epoch also affects the lunar tidal enhancement in the EEJ. It is found that the lunar tidal enhancements are significantly larger when the day of new or full moon lies near the central SSW epoch, as compared to cases when new or full moon occur further away from the central SSW epoch.

In the paper summarized by this presentation we trace how maps aided the conceptualization and ensuing debate over one of the first inherently spatial and multiscale environmental issues, acid rain. Through interviews with early acid rain ecologists and a critical cartographic analysis of printed maps, we show that mapping was central for constructing this environmental issue. Rather than static representations of a scientific reality, acid rain maps were interconnected and relational processes that operated within political and economic discourses. Accordingly, we suggest that increased critical engagement and participation with the process of mapping can productively aid dialog on many issues, including other current multiscale environmental issues, such as climate change.

The Space Physics Data Facility (SPDF) has developed and/or leveraged standardized self-describing data formats, metadata for datasets and parameters, time conventions, and dataset and filenaming conventions that enable effective data analysis and browsing using generic easy-to-use software and web services. Software and services include SPDF’s CDAWeb , and external tools such as Autoplot and SPEDAS IDL library. Standards and conventions include: datasets and filenaming and , the CDF scientific data format (including its new Python library ), the ISTP/IACG/SPDF Guidelines for global and variable attributes , time variable types , and the SKTeditor metadata creation tool . The SPASE standards for describing datasets for easy searching are crucial to the Heliophysics Data Portal .

Continental shelves are important land-ocean interfaces where natural and anthropogenic processes, as well as sediment geochemistry regulate the sequestration of organic matter (OM) in the sediment. In the Northern Gulf of Mexico, along the Louisiana shelf, the Mississippi River discharge asserts strong seasonal controls over primary production and sedimentary reserves of minerals. Recent studies have shown the importance of mineral-organic matter interactions in the sedimentary OM preservation, both of which are abundant in this region. Thus, the major objective of this work is to understand the spatial and temporal variability of the sediment organic carbon (OC) directly bound to the reactive iron (rFe) mineral phases such as goethite, ferrihydrite, lepidocrocite and hematite. Sediment samples were collected from five sites along the river plume during periods of low (August/September 2016) and high (May 2017) river discharge. Average rFe content in the top 20 cm of sediment was significantly higher at all sites in May (6.9 ±1.5 mg gdw-1) compared to August (4.3± 0.6 mg gdw-1), while particulate OC content in these sediments was higher in August (11.9 ± 3.7 mg gdw-1) compared to May (7.4± 4.7 mg gdw-1). However, the bulk OC bound to rFe in these sediments did not vary significantly between the two seasons and ranged between 2.3 - 3.4 mg gdw-1. Molar OC: Fe ratios in the OC associated with rFe ranged between 0.9-6.2, with higher ratios in the deeper sediment sections (5-20 cm) than at the top (0-5 cm). Our results indicate that 27- 32% of the total OC in sediment is associated with rFe phase and preserved in these recent shelf sediments. A combination of X-ray diffractometry and Fe-K Edge X-ray absorption near edge structure spectroscopy analyses were carried out to identify the mineralogical composition of rFe bound to the organic carbon in the sediments. Preliminary findings indicate that most of the iron is found as non-reactive iron in clay mineral smectite, but the dominant form of rFe associated with OC is goethite.

ICESat-2 carries NASA’s next-generation laser altimeter, ATLAS, (Advanced Topographic Laser Altimeter System), designed to measure changes in ice sheet height, sea ice freeboard, and vegetation canopy height. ATLAS contains a photon-counting lidar which transmits green (532-nm) pulses at 10kHz. Each pulse is split into 3 pairs of beams (one strong and one weak). Approximately 1014photons per pulse travel from ATLAS through the atmosphere to reflect off the Earth’s surface. Some return back into the ATLAS telescope where they are recorded. Photons from sunlight and instrument noise at the same wavelength are also recorded. The flight software time tags all photons within a 500m to 6 km range window and generates histograms. Using the histograms, it selects a telemetry window which varies from 20m over flat surfaces to hundreds of meters over rougher terrain. ATL03 contains the time, height (relative to the WGS-84 ellipsoid), latitude and longitude of every photon within the telemetry window. The basic challenge is to determine which of these photons were reflected off the surface. We have developed an algorithm that identifies these signal photons and assigns a confidence level (low, medium, or high) to each signal photon based on the signal to noise ratio. We present an overview of the signal identification algorithm and show the results on actual ICESat-2 data over ice sheet, sea ice, vegetated, and water surfaces. Higher level ATLAS products work with aggregations of the photons in order to determine the ellipsoidal height of the Earth, canopy height and structure, and other quantities of geophysical interest.

Arctic warming is outpacing the global rate of climate change, with up to 11 degrees C of warming projected by the year 2100 if greenhouse gas emissions follow their current trajectories. Increasing temperatures are expected to result in permafrost thaw, and the combined effects of precipitation changes, soil warming, and active layer deepening are expected to result in net soil drying. While there is widespread agreement that increasing temperatures and active layer depth will release carbon from soils, the effect on vegetative C cycling is less certain. In 2017, we conducted an experiment to examine the effects of soil drying and active layer deepening on primary productivity in Eriophorum vaginatum, a dominant circumpolar Arctic sedge, and the extent to which those effects vary across ecotypes. We harvested E. vaginatum tussocks from three sites along a latitudinal gradient in the Alaskan Arctic, placed them in pots filled with peat soil, and assigned each to one of three drying treatments. In one treatment, the soils were kept saturated with water through the growing season. In the second treatment, rain was excluded in alternating two-week cycles. In the third treatment, rain was also excluded in alternating two-week cycles, and the soil column was approximately doubled in depth to allow deeper drainage. We measured soil moisture, leaf water potential, leaf area index (LAI), leaf-level phenology, and photosynthetic capacity (Amax) in each of the tussocks. We found that the southern ecotype was affected most severely by drying, with reductions in LAI, maximum leaf length, and Amax. We found that effects were greater with rain exclusion and soil column deepening than with rain exclusion alone. However, we found no difference in leaf water potential between populations or treatments, suggesting that E. vaginatum leaves function within a fairly narrow range of moisture conditions. These results demonstrate that changes in soil moisture may affect carbon storage in Arctic vegetation, but that the magnitude of the effect may vary depending on region and ecotype.

As a national strategic resource, trade activities of potassium resources（K） have changed its state of ownership. Futures and spot trading forms in the international market are mainly primary processed ore and deep-processed products. So, K trade can be replaced by the potassium salt trade. Its international trade will affect a country’s strategic resource management, and increase national resource security risks. Thence, it is necessary to study the evolution of international trade in K. This paper has constructed a weighted and directed complex network model of K trade using UN Comtrade 2000-2016 data and analyzed the scale and activity of international trade of K, trade relations, trade flow distribution and the importance of countries. By analyzing the international trade data of K in 224 countries, it is found that trade is active year by year and K is becoming more significant. From network density and diameter, resource allocation is more convenient. The network cluster is growing. It shows that some countries form trade groups. The correlation coefficient of degrees is less than 0, indicating that the trade relationship between small and major trade countries is enhancing. And, the reciprocal coefficient is between 0.1 and 0.35, showing that the trade order is poor. Moreover, it presents a state that the greater the country’s degree, the smaller the difference in trade flow distribution. So, resource flows in countries with more trade relations can promote a balanced distribution of K. Finally, from countries’ trade influence and hub status, Canada is a leading trade country, and the US, the Russian Federation, China and Brazil are trade-led countries. They are the main source of K flows. China, the Netherlands, the US, France and India are important hubs. So, countries should strengthen bilateral trade relations. So as to ensure the SD of international trade in K, major trading countries should focus on the exploit of K and improve the level of production and processing tech. Countries should also enhance their hub role to facilitate the flow of K. China, as a large country in agriculture and K demand, should increase self-sufficiency to reduce import dependence risks. Besides, attention should be paid to market changes in major trading countries and to reducing risks by adding the number of trade countries.

Immersion freezing is an important heterogeneous ice nucleation process in mixed-phase clouds. Many researches on immersion freezing focus on the parameterization using the classical nucleation theory. However, the ice nucleating abilities of the atmospheric aerosol particles are not well understood, and therefore cause difficulties of the parameterization of immersion freezing. In this study, we investigate the ice nucleating ability of Marigold pollen from the Beijing area by doing drop immersion freezing experiments in the laboratory. Marigold pollen are first mixed with pure water. A population of drops with a volume of 10 mL from the mixture are then put on a PE film in a chamber with a cooling rate of about 0.5 °C min-1. We find that the median freezing temperature of drops with pollen as ice nuclei is -17 °C. The contact angle parameterization of immersion freezing using the classical nucleation theory is also given in this study. We use the single-θ and the θ-pdf parameterization schemes to explain the data. The results show that the θ-pdf parameterization scheme is better for describing the ice nucleating behavior of the pollen in Beijing.

Water security hinges on water storage. Although the public and water resources planners habitually look to surface reservoirs for storage solutions, by far the largest ‘space’ to store water is underground. The very nature of freshwater distribution on Earth foreshadows future water storage solutions, as 97% of all circulating freshwater globally is in groundwater. Similarly, although 140 surface reservoirs in California can store 52 km3(42 MAF), in the Central Valley aquifer system there is room for another ~170 km3(~140 MAF) owing to past depletion. Despite the state’s Mediterranean climate in which nearly all of the precipitation occurs between November and March when demand is lowest, historically massive snow storage and spring-summer snow melt synchronized well with surface reservoir replenishment during April-July. This system built around snow storage as a means of mitigating winter flood threats and delaying runoff until the beginning of the peak demand season is clearly demonstrating significant vulnerabilities to climate change and drought. Climate warming has already produced decades of declining snowmelt runoff, making surface reservoir storage more difficult. Moreover, as demonstrated during the 2012-16 drought, in the face of droughts longer than a few years, the surface storage offers inadequate long-term water security. This fact, the fact that California during pre-development times of the last millennium experienced far longer droughts, and ongoing climate change clearly indicate the need for a different strategy that more fully leverages both surface and subsurface storage. Kocis and Dahlke (2017) show that increasing winter runoff during wet and normal years provide enough high-magnitude flows to support a strategy of diverting flood flows for groundwater storage. This “flood-MAR” (managed aquifer recharge) approach will require a massive change in winter water and land management that exploits recharge opportunities on irrigated farm lands and in areas with suitable soils and subsurface geology. A case study in the American-Cosumnes Rivers portion of the Central Valley shows how total system water storage can be increased dramatically through diversion of high-magnitude flows and reoperation of both the surface and subsurface reservoirs including economic incentives.

We present in-situ ion composition and velocity measurements from the Enhanced Polar Outflow Probe during the August 2017 solar eclipse, which crossed the path of totality at ~640 km altitude within 10 minutes of totality passing. These measurements reveal two distinct H+ ion populations, and show a ~40% decrease in topside plasma density, a similar drop in upward but not downward H+ ion flux, and a downward O+ ion velocity of ~100 m/s. These features are directly linked to changes in the H+/O+ composition and field-aligned or interhemispheric light ion flow, and reduction in the negative spacecraft potential. These observed features were absent on the preceding, non-eclipse days, and corroborate the reduction in F-region plasma density and topside Total Electron Content (TEC) observed by the Global Position System (GPS) receivers onboard. They are attributed to the temporary reduction of photoionization in the eclipsed F-region.

Radio science experiments for planetary geodesy or tests or relativistic gravity involve precise measurements of the spacecraft range rate enabled by two-way microwave links. Since the uncertainty on the estimated parameters depend almost linearly on the noise in the radio link, finding ways to reduce disturbances is essential for best scientific results. Tropospheric and antenna mechanical noises, among the leading noise sources in two-way Ka-band radio links, could be reduced using a suitable combination of Doppler data collected at the two-way antenna and at an additional, smaller and stiffer, three-way antenna [1]. The Time-Delay Noise Cancellation technique (TDMC) can provide significant reduction of the measurement noise if the listen-only antenna is located in a site with particularly favorable tropospheric conditions. This noise-reducing technique has only been tested by artificially producing a large mechanical noise event at the two-way antenna and using a similar three-way antenna to cancel the disturbance. We report on a practical demonstration of the capabilities of the TDMC technique applied to Doppler data from Cassini spanning 2004 through the last Titan gravity flyby in 2016. The tracking configuration in those passes was not tailored for the use of the TDMC, therefore the technique proves to be effective only with favorable noise conditions. Nonetheless, for those passes where tropospheric or antenna mechanical noises were relevant, we find substantial noise reduction. For example, Doppler data from the Titan-122 gravity flyby processed with the TDMC show about a factor-of-three noise reduction (at 60-s integration time) with respect to the two-way link. These results suggest that the choice of the three-way antenna and the scheduling of the tracking passes are crucial parameters that should be considered to fully exploit the improvement in accuracy provided by the TDMC technique. [1] Armstrong, J. W. et al., Radio Science 43 RS3010 (2008)

Addressing research problems in Earth and environmental science usually requires combining data from multiple sources. This is facilitated by the use of common practices, vocabularies, interfaces and standards and recently it has been accelerated through connected communities of practice. This abstract will focus on the Earth Science Information Partners (ESIP) and the Australian Earth and Environment Science Information Partners (E2SIP) Over the last 20 years ESIP has built a community of practice in USA, supported by NASA, NOAA & USGS, through regular meetings and online forums to examine and develop emerging technologies. ESIP has become a braintrust and professional home for the Earth science data and informatics community where both peer-led education & training and the codevelopment of conventions, practices and guidelines have helped make Earth science data more interoperable. Through connections in the ESIP network and these boundary objects, ESIP has influenced the international community. The Australian Earth and Environment Science Information Partners (E2SIP) was recently established through liaison with ESIP to support similar functions in Australia. E2SIP is working with the National Earth and Environmental Sciences Facilities Forum which provides a common voice to government on behalf of long term science infrastructure. In addition, E2SIP, supported by programs from the National Research Infrastructure Strategy (NCRIS) such as the newly formed Australian Research Data Commons (ARDC), will convene workshops, courses, hackathons, and develop guidance and best practices tailored for the Australian community. This talk will explore how ESIP and E2SIP will work together, utilizing the collective impact framework orienting around a common shared agenda and leveraging a shared backbone structure in the U.S. and Australia. We will highlight our current understanding through a few case studies.

Methane fluxes are often studied using eddy covariance flux towers or chambers placed on the soil surface. These measurement techniques have improved our understanding of methane emissions from wetlands. However, there are limitations with each measurement method. For example, chambers are fixed in place and have high maintenance costs, limiting spatial coverage and characterization of heterogeneity. Measurements taken in Interior Alaskan wetlands suggest that heterogeneity in methane fluxes from this region may increase during the fall and early winter, when the soils begin to freeze. Unfortunately, off-grid power limitations and freezing conditions complicate chamber operation during this time. Towers share similar demands with respect to maintenance and cost of operation, and, therefore, are not often replicated within a landscape. Moreover, towers provide an integrated measurement which masks any spatial heterogeneity in fluxes within the tower footprint. Therefore, although chamber and flux towers provide important insights into the carbon exchange between terrestrial and atmospheric pools, these methods have limitations, particularly when characterizing spatial heterogeneity. We tested a new technology that may be able to be counteract some of these limitations, thereby providing additional insights into methane emissions from wetlands. We outfitted a small-unmanned aerial system (sUAS, or drone), that can fly extremely close (<2 m) to the wetland’s surface, with a miniature open-path laser spectrometer methane sensor, LIDAR, and a miniature anemometer. We then tested this system in several bogs near Fairbanks, Alaska. We tested if this system could detect spatial and/or temporal variability of methane emissions within a bog. We also compared methane fluxes calculated using this system to values obtained from tower and chamber measurements. Results of these missions will be presented and we will discuss the ability of this new technology to provide additional information regarding methane emissions from wetlands.

Ultrasound Computer Tomography (USCT) is an emerging technique for breast cancer screening. Ultrasonic waves are propagated through the tissue and recorded by a set of transducers that are surrounding the breast. The experiment collects transmission and reflection data, which are used to obtain quantitative images of acoustic properties of the tissue (see Figure). This information is useful to characterize the breast tissue, and improves the specificity of standard imaging modalities. However, providing a diagnostic tool with high accuracy and clinically affordable time-to-solution (goal: ~15 min/patient) still remains a challenge. The goal of this work is to show that, despite the vast scale differences, experiments in seismology and USCT share many similarities. In both fields, the relative wave speed variations are comparable and the number of propagated wavelengths in the domain has the same order of magnitude. Because the wave equation is scale invariant, the cross-fertilization between both fields will benefit imaging methods on all scales. In this study, we present methods from seismic tomography that we have recently introduced to USCT: 1) We employ a linearized finite-frequency traveltime tomography approach for speed-of-sound reconstruction. Using the cross-correlation traveltime misfit functional, we compute analytically the sensitivity kernels using adjoint techniques. Our method can operate almost in real time while still including finite-frequency effects. It also can retrieve useful 3D information from 2D acquisition systems. 2) Similar to exploration geophysics, both speed-of-sound and reflectivity images are important for the interpretation. Here, we suggest a framework that combines full-waveform inversion for speed-of-sound and reverse time migration for reflectivity. 3) We apply the Sequential Optimal Experimental Design (SOED) method to optimize the position and number of transducers, in terms of accuracy and cost, to image both reflection and transmission information. Using the Bayesian approach, we define the quality of a design as the average of the posterior variances of the parameters. SOED provides cost-benefit curves that quantifies the information gain versus the computational cost. These are useful to control the trade-off between accuracy and practicality.

A wide variety of research applications require knowledge of total solar irradiance (TSI) and solar spectral irradiance (SSI) on time scales from minutes to centuries. The current satellite data record of TSI and ultraviolet SSI is 40 years long while observations of solar irradiance at visible wavelengths through the near-infrared span 15 years. In late 2017, the NASA Total and Spectral Solar Irradiance Sensor-1 (TSIS-1) mission was deployed on the International Space Station (ISS); these new TSI and SSI datasets are now extending the observational solar irradiance record with a planned 5-year mission. Recognizing the need for ongoing specification of solar irradiance, the National Centers for Environmental Information established the Solar Irradiance Climate Data Record (CDR) in 2014. The CDR includes a composite record of TSI observations and estimates of solar total and spectral irradiance variations during, and prior, to the space-based record based on the Naval Research Laboratory (NRL) models. Utilizing as inputs proxies of sunspot darkening and facular brightening, the models specify TSI and SSI annually since 1610 and daily since 1882. Both the observational composite and the model specifications are updated regularly and will eventually utilize the new TSIS-1 observations, both to extend the observational composite and to validate and improve the models. With the goal of establishing the utility of the NRL models in specifying the time and wavelength dependence of solar variability for the Solar Irradiance CDR, we compare the latest NRLTSI2 and NRLSSI2 modeled irradiances with observations, including composite records, and with independent models of solar irradiance variability. Our assessments quantify current understanding of solar irradiance variability on multiple timescales and identify areas where TSIS-1 observations are expected to provide improved understanding of solar irradiance variability. We use the following datasets in our comparisons: TSIS-1, Solar Radiation and Climate Experiment (SORCE), Ozone Monitoring Instrument (OMI), Solar Irradiance Data Exploitation (SOLID), Spectral and Total Irradiance Reconstructions for the Satellite Era (SATIRE-S), a three-dimensional extension of the SATIRE-S model (SATIRE-3D), and Empirical Irradiance Reconstruction (EMPIRE).

The 2018 eruption of Kīlauea Volcano included caldera collapse at the summit of the volcano that was well recorded by a network of both permanent and temporary seismometers and infrasound microphones. Volcanic activity prior to the start of the eruption was elevated, including high lava lake levels and increased seismicity. Deflation of the summit began shortly after the eruption in the lower East Rift Zone commenced and was accompanied by a drop in the summit lava lake, which eventually disappeared from view after lowering by several hundred meters. Continued volume loss from beneath the summit eventually led to caldera collapse, which was accompanied by increases in earthquake rates and tremor amplitudes. Infrasonic tremor that originally rose from spattering at the surface of the lava lake was replaced by discrete infrasonic events arising from rockfalls and slumps. On May 16, the first of tens of collapse events occurred, beginning a cycle of increasing earthquake rates and energy release in the presence of deflation. After an initial increase in rate, seismicity rates remained constant for several hours prior to the next collapse event. Earthquakes during these events were typically part of repeating earthquake families and occurred on one of several circumferential cracks that marked active collapsing blocks. Through time, earthquake activity has mirrored the morphology of the collapse, migrating primarily north and east as caldera down drop extended in those directions. Collapse-related infrasound arrivals were initially down, suggesting downdropping of the surface, followed several seconds later by higher frequency infrasound, which we interpret to reflect the explosive or expulsion phase reaching the surface. Infrasound signals were 2-3 times more energetic below 0.5 Hz than above. Especially after May 29, when caldera collapse became much larger in surface area, infrasound signals were highly repetitive with a strong downward first motion. The collapse events were also deficient at seismic frequencies > 0.5 Hz, compared to typical tectonic earthquake sources. Despite similarities in waveforms at low frequencies (<0.1 Hz) and in infrasound, the seismic waveforms at high frequencies were not similar, reflecting either a unique source in each collapse event or a change in location.