193 research outputs found

    A fast method for the retrieval of integrated longwave and shortwave top-of-atmosphere upwelling irradiances from MSG/SEVIRI (RRUMS)

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    A new Rapid Retrieval of Upwelling irradiances from MSG/SEVIRI (RRUMS) is presented. It has been developed to observe the top-of-atmosphere irradiances of small scale and rapidly changing features that are not sufficiently resolved by specific Earth radiation budget sensors. Our retrieval takes advantage of the spatial and temporal resolution of MSG/SEVIRI and provides outgoing longwave and reflected shortwave radiation only by means of a combination of SEVIRI channels. The longwave retrieval is based on a simple linear combination of brightness temperatures from the SEVIRI infrared channels. The shortwave retrieval is based on a neural network that requires as input the visible and near-infrared SEVIRI channels

    Eighth Anniversary of the Intercultural Mayan University of Quintana Roo: Achieved Goals and Remaining Challenges

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    On October 30, 2006 the creation decree of the Intercultural Mayan University of Quintana Roo was signed (UIMQRoo) with the goal of a different, more inclusive, education model that would strengthen the Mayan language and culture. Now, eight years after its creation, we would like to share a brief summary of our achievements, reflecting on how we can tackle our remaining challenges

    VADUGS: a neural network for the remote sensing of volcanic ash with MSG/SEVIRI trained with synthetic thermal satellite observations simulated with a radiative transfer model

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    After the eruption of volcanoes around the world, monitoring of the dispersion of ash in the atmosphere is an important task for satellite remote sensing since ash represents a threat to air traffic. In this work we present a novel method, tailored for Eyjafjallajökull ash but applicable to other eruptions as well, that uses thermal observations of the SEVIRI imager aboard the geostationary Meteosat Second Generation satellite to detect ash clouds and determine their mass column concentration and top height during the day and night. This approach requires the compilation of an extensive data set of synthetic SEVIRI observations to train an artificial neural network. This is done by means of the RTSIM tool that combines atmospheric, surface and ash properties and runs automatically a large number of radiative transfer calculations for the entire SEVIRI disk. The resulting algorithm is called "VADUGS" (Volcanic Ash Detection Using Geostationary Satellites) and has been evaluated against independent radiative transfer simulations. VADUGS detects ash-contaminated pixels with a probability of detection of 0.84 and a false-alarm rate of 0.05. Ash column concentrations are provided by VADUGS with correlations up to 0.5, a scatter up to 0.6 g m-2 for concentrations smaller than 2.0 g m-2 and small overestimations in the range 5 %-50 % for moderate viewing angles 35-65°, but up to 300 % for satellite viewing zenith angles close to 90 or 0°. Ash top heights are mainly underestimated, with the smallest underestimation of -9 % for viewing zenith angles between 40 and 50°. Absolute errors are smaller than 70 % and with high correlation coefficients of up to 0.7 for ash clouds with high mass column concentrations. A comparison with spaceborne lidar observations by CALIPSO/CALIOP confirms these results: For six overpasses over the ash cloud from the Puyehue-Cordón Caulle volcano in June 2011, VADUGS shows similar features as the corresponding lidar data, with a correlation coefficient of 0.49 and an overestimation of ash column concentration by 55 %, although still in the range of uncertainty of CALIOP. A comparison with another ash algorithm shows that both retrievals provide plausible detection results, with VADUGS being able to detect ash further away from the Eyjafjallajökull volcano, but sometimes missing the thick ash clouds close to the vent. VADUGS is run operationally at the German Weather Service and this application is also presented

    Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

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    Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

    Contrail life cycle and properties from 1 year of MSG/SEVIRI rapid-scan images

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    The automatic contrail tracking algorithm (ACTA) – developed to automatically follow contrails as they age, drift and spread – enables the study of a large number of contrails and the evolution of contrail properties with time. In this paper we present a year’s worth of tracked contrails, from August 2008 to July 2009 in order to derive statistically significant mean values. The tracking is performed using the 5 min rapid-scan mode of the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board the Meteosat Second Generation (MSG) satellites

    Statistical analysis of contrail lifetimes from a satellite perspective

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    The study of the lifetimes of contrails from a satellite perspective benefits from the extended coverage and close temporal monitoring. However, the initial stages of the contrail development are not observed from a satellite platform due to the sub-pixel size of the forming cloud. The final stages may be unobserved as well when the contrails get spatially diluted and when they lose contrast with their background. In this paper we apply a Weibull distribution model to describe the survival rate of contrails during their observed life-span and adjust its two defining parameters (lambda and k) to fit a dataset of over 2300 contrails. Using the Weibull distribution, it is possible to estimate the expected further lifetime of the contrails after satellite observation ceased. Depending on the actually observed lifetime, the expected extension can range from about 1 to 4h, but the overall mean of this duration is about 1.3h. The time elapsed between contrail formation and first satellite observation is estimated from the initial width distribution of the contrails. Under the assumption of a 5km/h spreading rate, the average age of contrails at the time of their first satellite detection is 1.5+-0.4h. Using a Monte Carlo simulation, we are able to compute the cumulative distribution of the complete (i.e. initial spreading, tracking, and after-tracking periods) lifetime of persistent contrails. This complete lifetime has a mean value of 3.7+-2.8h. The Weibull distribution (k<1) shows that the probability to survive increases with contrail age, which corresponds to the actual decay rate of contrails in nature. Additionally, we analyse lifetime differences between daytime and nighttime contrails. We find that nighttime contrails have slightly shorter lifetimes than daytime contrails. Although this difference is statistically significant, it remains to be shown whether this has important physical consequences
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