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  • ItemOpen Access
    Dataset associated with "A nonmonotonic precipitation response to changes in soil moisture in the presence of vegetation"
    (Colorado State University. Libraries, 2022) Drager, Aryeh Jacob; Grant, Leah D.; van den Heever, Susan C.
    In many parts of the world, humans rely on afternoon rainfall for their water supply. However, it is not fully understood how land surface properties influence afternoon precipitation. In fact, disagreement remains regarding the relative prevalence of “wet-soil advantage” regimes, in which wet soils receive more precipitation than do dry soils, and “dry-soil advantage” regimes, in which the opposite occurs. Recent studies have proposed that the permanent wilting point (PWP) soil moisture threshold influences the location and organization of convective clouds. Motivated by this work, we investigate how changes in soil moisture relative to the PWP affect the timing and amount of surface rainfall, as well as how this response depends on the presence or absence of vegetation. This investigation is carried out by conducting several series of high-resolution, idealized numerical experiments using a fully coupled, interactive soil-vegetation-atmosphere modeling system. From these experiments, a new soil moisture-precipitation relationship emerges: in the presence of vegetation, simulations with moderately dry soils, whose initial liquid water content slightly exceeds the PWP, generate significantly less surface precipitation than do those with the driest or wettest soils. This result suggests that simulated “wet-soil advantage” and “dry-soil advantage” regimes may not necessarily be mutually exclusive, insofar as extremely wet and extremely dry soils can both exhibit an “advantage” over moderately dry soils. This non-monotonic soil moisture-precipitation relationship is found to result from the PWP’s modulation of transpiration of water vapor by plants. In the absence of vegetation, a wet-soil advantage occurs instead in these idealized simulations.
  • ItemOpen Access
    Dataset associated with "Ocean Surface Flux Algorithm Effects on Tropical Indo-Pacific Intraseasonal Precipitation"
    (Colorado State University. Libraries, 2021) Hsu, Chia-Wei; DeMott, Charlotte; Branson, Mark
    Surface latent heat fluxes help maintain tropical intraseasonal precipitation. We develop a latent heat flux diagnostic that depicts how latent heat fluxes vary with the near-surface specific humidity vertical gradient (dq) and surface wind speed (|V|). Compared to fluxes estimated from |V| and dq measured at tropical moorings and the COARE3.0 algorithm, tropical latent heat fluxes in the NCAR CEMS2 and DOE E3SMv1 models are significantly overestimated at |V| and dq extrema. MJO sensitivity to surface flux algorithm is tested with offline and inline flux corrections. The offline correction adjusts model output fluxes toward mooring-estimated fluxes; the inline correction replaces the original bulk flux algorithm with the COARE3.0 algorithm in atmosphere-only simulations of each model. Both corrections reduce the latent heat flux feedback to intraseasonal precipitation, in better agreement with observations, suggesting that model-simulated fluxes are overly supportive for maintaining MJO convection.
  • ItemOpen Access
    Cross-Track Infrared Sounder (CrIS) Peroxyacetyl Nitrate (PAN) and Carbon Monoxide (CO) retrievals for the 2018 wildfire season over the western U.S.
    (Colorado State University. Libraries, 2021) Juncosa Calahorrano, Julieta Fernanda
    We use new peroxyacetyl nitrate (PAN) observations from the Cross-Track Infrared Sounder (CrIS) on the Suomi National Polar-orbiting Partnership satellite to investigate PAN over the western U.S. during the summer 2018 North American wildfire season. This period coincides with the Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN). When combined with favorable background conditions, the resolution and sensitivity of CrIS is sufficient to observe PAN production in plumes. CrIS PAN normalized excess mixing ratios (NEMRs) in the Pole Creek Fire increase from 0.2% to 0.4% within 3-4 hours of physical aging, consistent with NEMRs calculated from WE-CAN observations. CrIS is also able to detect PAN and CO enhancements in plumes that have been transported hours to days downwind. On average for the study period, 24-56% of PAN in the free troposphere during the afternoon over the western U.S. can be attributed to fires.
  • ItemOpen Access
    Dataset associated with "A tale of two dust storms: analysis of a complex dust event in the Middle East"
    (Colorado State University. Libraries, 2019) Miller, Steven
    Lofted mineral dust over data-sparse regions presents considerable challenges to satellite-based remote sensing methods and numerical weather prediction alike. The Southwest Asia domain is replete with such examples, with its diverse array of dust sources, dust mineralogy, and meteorologically-driven lofting mechanisms on multiple spatial and temporal scales. A microcosm of these challenges occurred over 3-4 August 2016 when two dust plumes, one lofted within an inland dry air mass and another embedded within a moist air mass, met over the Southern Arabian Peninsula. Whereas conventional infrared-based techniques readily detected the dry air mass dust plume, they experienced marked difficulties in detecting the moist air mass dust plume, which only became apparent when visible reflectance revealed it crossing over an adjacent dark water background. In combining information from numerical modelling, multi-satellite/multi-sensor observations of lofted dust and moisture profiles, and idealized radiative transfer simulations, we develop a better understanding of the environmental controls of this event, characterizing the sensitivity of infrared-based dust detection to column water vapor, dust vertical extent, and dust optical properties. Differences in assumptions of dust complex refractive index translate to variations in the sign and magnitude of the split-window brightness temperature difference commonly used for detecting mineral dust. A multi-sensor technique for mitigating the radiative masking effects of water vapor via modulation of the split-window dust-detection threshold, predicated on idealized simulations tied to these driving factors, is proposed and demonstrated. The new technique, indexed to an independent description of the surface-to-500 hPa atmospheric column moisture, reveals parts of the missing dust plume embedded in the moist air mass, with best performance over land surfaces.
  • ItemOpen Access
    Dataset associated with "Spatial and temporal patterns of sediment storage and erosion following a wildfire and extreme flood"
    (Colorado State University. Libraries, 2019) Nelson, Peter A.; Brogan, Daniel J.
    Post-wildfire landscapes are highly susceptible to rapid geomorphic changes at both the hillslope and watershed scales due to the increases in infiltration-excess overland flow, hillslope and channel erosion, and downstream deposition. While there have been numerous studies of these processes at the hillslope scale, relatively few studies have documented larger-scale post-fire geomorphic changes over time. In this study we used five airborne laser scanning (ALS) datasets collected over four years to quantify valley bottom changes in two ~15 km2 watersheds, Skin Gulch and Hill Gulch, after the June 2012 High Park fire in northern Colorado and followed by a large mesoscale flood 15 months later. The objectives were to: 1) quantify spatial and temporal patterns of erosion and deposition throughout the channel network following the wildfire and subsequent flooding; and 2) investigate the extent to which these changes can be related to precipitation amounts and intensities, burn severity, and valley and basin morphology. Geomorphic changes were quantified using a DEMs of difference (DoD) approach for the channel network segmented into 50-m lengths. The DoDs show net sediment accumulation after the wildfire in the valley bottoms in both watersheds, with the greatest accumulation after summer thunderstorms in the first two years after burning in areas with wider and flatter valley bottoms. In contrast, the mesoscale flood caused large amounts of net erosion, with the greatest erosion in those areas with the greatest post-fire deposition. Volume changes for the different time periods were low but significantly correlated to, in order of highest correlation, contributing area, channel width, percent burned at high and/or moderate severity, channel slope, confinement ratio, maximum 30-minute rainfall, and total rainfall. These results suggest that morphometric characteristics, when combined with burn severity and a specified storm, can indicate the relative likelihood and locations for post-fire erosion and deposition. This information can help assess downstream risks and prioritize areas for post-fire hillslope rehabilitation treatments.
  • ItemOpen Access
    Dataset associated with "Role modeling is a viable retention strategy for undergraduate women in the geosciences"
    (Colorado State University. Libraries, 2018) Hernandez, Paul; Bloodhart, Brittany; Adams, Amanda S.; Barnes, Rebecca T.; Burt, Melissa; Clinton, Sandra M.; Du, Wenyi; Godfrey, Elaine; Henderson, Heather; Pollack, Ilana B.; Fischer, Emily V.
    Gender diversity leads to better science; however, a number of STEM disciplines, including many geoscience sub-disciplines show a persistent gender gap. PROmoting Geoscience Research, Education, and SuccesS (PROGRESS) is a theory-driven role modeling and mentoring program aimed at supporting undergraduate women interested in geoscience-related degree and career pathways. This study is unique because it is being conducted in a long-term applied setting, rather than as a laboratory exercise. We compare female STEM majors in PROGRESS to a matched control group (N = 380) using a longitudinal prospective multi-site quasi-experimental design. College women in PROGRESS participated in a mentoring and role modeling weekend workshop with follow-up support, while women in the control group participated in neither the workshop nor the follow-up support. PROGRESS members identified more female STEM career role models than controls (60% vs. 42%, respectively), suggesting that deliberate interventions can develop the networks of undergraduate women. Undergraduate women that participate in PROGRESS have higher rates of persistence in geoscience-related majors (95% vs. 73%), although the rates of switching into a geoscience-related major did not differ across groups. More strikingly, we also find that the persistence of undergraduate women in geoscience-related majors is related to the number of female STEM career role models they identify, as their odds of persisting approximately doubles for each role model they identify. We conclude that our ability to retain undergraduate women in the geosciences will depend, in part, on helping them to identify same-gender career role models. Further, the success of PROGRESS points to steps universities and departments can take to sustain their students' interest and persistence, such as hosting interactive panels with diverse female scientists to promote the attainability and social relevance of geoscience careers.