81 research outputs found
Utilisation de la grille pour la simulation de température de brillance dans une atmosphÚre nuageuse composée de cirrus
Utilisation de la grille pour la simulation de température de brillance dans une atmosphÚre nuageuse composée de cirru
Bericht ĂŒber die Verleihung der Jugendpreise 2010. Integration in lĂ€ndlichen Gebieten - Förderung des lĂ€ndlichen Raumes als Mittler zwischen unterschiedlichen Kulturen, Wiesbaden 17. 09. 2010
Incorporating EarthCARE observations into a multi-lidar cloud climate record: the ATLID (Atmospheric Lidar) cloud climate product
Despite significant advances in atmospheric measurements and modeling,
clouds' response to human-induced climate warming remains the largest source
of uncertainty in model predictions of climate. The launch of the Cloud-Aerosol
Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite in 2006
started the era of long-term spaceborne optical active sounding of
Earth's atmosphere, which continued with the CATS (Cloud-Aerosol Transport
System) lidar on board the International Space Station (ISS) in 2015 and the Atmospheric Laser Doppler
Instrument (ALADIN) lidar on board Aeolus in 2018. The next important step
is the Atmospheric Lidar (ATLID) instrument from the EarthCARE (Earth Clouds, Aerosols and Radiation Explorer) mission,
expected to launch in 2024.
In this article, we define the ATLID Climate Product, Short-Term (CLIMP-ST)
and ATLID Climate Product, Long-Term (CLIMP-LT). The purpose of CLIMP-ST is
to help evaluate the description of cloud processes in climate models,
beyond what is already done with existing space lidar observations, thanks
to ATLID's new capabilities. The CLIMP-LT product will merge the ATLID cloud
observations with previous space lidar observations to build a long-term
cloud lidar record useful to evaluate the cloud climate variability
predicted by climate models.
We start with comparing the cloud detection capabilities of ATLID and CALIOP
(Cloud-Aerosol Lidar with Orthogonal Polarization) in day- and nighttime, on
a profile-to-profile basis in analyzing virtual ATLID (355ânm) and CALIOP
(532ânm) measurements over synthetic cirrus and stratocumulus cloud scenes.
We show that solar background noise affects the cloud detectability in
daytime conditions differently for ATLID and CALIPSO.
We found that the simulated daytime ATLID measurements have lower noise than
the simulated daytime CALIOP measurements. This allows for lowering the cloud
detection thresholds for ATLID compared to CALIOP and enables ATLID to
better detect optically thinner clouds than CALIOP in daytime at high horizontal
resolution without false cloud detection. These lower threshold values will
be used to build the CLIMP-ST (Short-Term, related only to the ATLID
observational period) product. This product should provide the ability to evaluate
optically thin clouds like cirrus in climate models compared to the current
existing capability.
We also found that ATLID and CALIPSO may detect similar clouds if we convert
ATLID 355ânm profiles to 532ânm profiles and apply the same cloud detection
thresholds as the ones used in GOCCP (GCM-Oriented CALIPSO Cloud Product; general circulation model).
Therefore, this approach will be used to build the CLIMP-LT product. The CLIMP-LT
data will be merged with the GOCCP data to get a long-term (2006â2030s)
cloud climate record. Finally, we investigate the detectability of cloud
changes induced by human-caused climate warming within a virtual long-term
cloud monthly gridded lidar dataset over the 2008â2034 period that we
obtained from two oceanâatmosphere coupled climate models coupled with a
lidar simulator. We found that a long-term trend of opaque cloud cover
should emerge from short-term natural climate variability after 4Â years
(possible lifetime) to 7Â years (best-case scenario) for ATLID merged with
CALIPSO measurements according to predictions from the considered climate
models. We conclude that a long-term lidar cloud record built from the merging
of the actual ATLID-LT data with CALIPSO-GOCCP data will be a useful tool for
monitoring cloud changes and evaluating the realism of the cloud changes
predicted by climate models.</p
Scale dependence of cirrus heterogeneity effects. Part II: MODIS NIR and SWIR channels
In a context of global climate change, the understanding of the radiative
role of clouds is crucial. On average, ice clouds such as cirrus have a
significant positive radiative effect, but under some conditions the effect
may be negative. However, many uncertainties remain regarding the role of ice
clouds on Earth's radiative budget and in a changing climate. Global
satellite observations are particularly well suited to monitoring clouds,
retrieving their characteristics and inferring their radiative impact. To
retrieve ice cloud properties (optical thickness and ice crystal effective
size), current operational algorithms assume that each pixel of the observed
scene is plane-parallel and homogeneous, and that there is no radiative
connection between neighboring pixels. Yet these retrieval assumptions are
far from accurate, as real radiative transfer is 3-D. This leads to the
plane-parallel and homogeneous bias (PPHB) plus the independent pixel
approximation bias (IPAB), which impacts both the estimation of
top-of-the-atmosphere (TOA) radiation and the retrievals. An important factor
that determines the impact of these assumptions is the sensor spatial
resolution. High-spatial-resolution pixels can better represent cloud
variability (low PPHB), but the radiative path through the cloud can involve
many pixels (high IPAB). In contrast, low-spatial-resolution pixels poorly
represent the cloud variability (high PPHB), but the radiation is better
contained within the pixel field of view (low IPAB). In addition, the solar
and viewing geometry (as well as cloud optical properties) can modulate the
magnitude of the PPHB and IPAB. In this, Part II of our study, we simulate
TOA 0.86 and 2.13â”m solar reflectances over a cirrus uncinus
scene produced by the 3DCLOUD model. Then, 3-D
radiative transfer simulations are performed with the 3DMCPOL
code at spatial resolutions ranging from 50 m to 10 km, for 12
viewing geometries and nine solar geometries. It is found that, for simulated
nadir observations taken at resolution higher than 2.5 km, horizontal
radiation transport (HRT) dominates biases between 3-D and 1-D reflectance
calculations, but these biases are mitigated by the side illumination and
shadowing effects for off-zenith solar geometries. At resolutions coarser
than 2.5 km, PPHB dominates. For off-nadir observations at resolutions
higher than 2.5 km, the effect that we call THEAB (tilted and homogeneous
extinction approximation bias) due to the oblique line of sight passing
through many cloud columns contributes to a large increase of the
reflectances, but 3-D radiative effects such as shadowing and side
illumination for oblique Sun are also important. At resolutions coarser than
2.5 km, the PPHB is again the dominant effect. The magnitude and resolution
dependence of PPHB and IPAB is very different for visible, near-infrared and
shortwave infrared channels compared with the thermal infrared channels
discussed in Part I of this study. The contrast of 3-D radiative effects
between solar and thermal infrared channels may be a significant issue for
retrieval techniques that simultaneously use radiative measurements across a
wide range of solar reflectance and infrared wavelengths.</p
Acute mental health presentations before and during the COVID-19 pandemic
Background:
A number of community based surveys have identified an increase in psychological symptoms and distress but there has been no examination of symptoms at the more severe end of the mental health spectrum. //
Aims:
We aimed to analyse numbers and types of psychiatric presentations to inform planning for future demand on mental health services in light of the COVID-19 pandemic. //
Method:
We analysed electronic data between January and April 2020 for 2534 patients referred to acute psychiatric services, and tested for differences in patient demographics, symptom severity and use of the Mental Health Act 1983 (MHA), before and after lockdown. We used interrupted time-series analyses to compare trends in emergency department and psychiatric presentations until December 2020. //
Results:
There were 22% fewer psychiatric presentations the first week and 48% fewer emergency department presentations in the first month after lockdown initiated. A higher proportion of patients were detained under the MHA (22.2 v. 16.1%) and Mental Capacity Act 2005 (2.2 v. 1.1%) (Ï2(2) = 16.3, P < 0.0001), and they experienced a longer duration of symptoms before seeking help from mental health services (Ï2(3) = 18.6, P < 0.0001). A higher proportion of patients presented with psychotic symptoms (23.3 v. 17.0%) or delirium (7.0 v. 3.6%), and fewer had self-harm behaviour (43.8 v. 52.0%, Ï2(7) = 28.7, P < 0.0001). A higher proportion were admitted to psychiatric in-patient units (22.2 v. 18.3%) (Ï2(6) = 42.8, P < 0.0001) after lockdown. //
Conclusions:
UK lockdown resulted in fewer psychiatric presentations, but those who presented were more likely to have severe symptoms, be detained under the MHA and be admitted to hospital. Psychiatric services should ensure provision of care for these patients as well as planning for those affected by future COVID-19 waves
Laparoscopy in management of appendicitis in high-, middle-, and low-income countries: a multicenter, prospective, cohort study.
BACKGROUND: Appendicitis is the most common abdominal surgical emergency worldwide. Differences between high- and low-income settings in the availability of laparoscopic appendectomy, alternative management choices, and outcomes are poorly described. The aim was to identify variation in surgical management and outcomes of appendicitis within low-, middle-, and high-Human Development Index (HDI) countries worldwide. METHODS: This is a multicenter, international prospective cohort study. Consecutive sampling of patients undergoing emergency appendectomy over 6Â months was conducted. Follow-up lasted 30Â days. RESULTS: 4546 patients from 52 countries underwent appendectomy (2499 high-, 1540 middle-, and 507 low-HDI groups). Surgical site infection (SSI) rates were higher in low-HDI (OR 2.57, 95% CI 1.33-4.99, pâ=â0.005) but not middle-HDI countries (OR 1.38, 95% CI 0.76-2.52, pâ=â0.291), compared with high-HDI countries after adjustment. A laparoscopic approach was common in high-HDI countries (1693/2499, 67.7%), but infrequent in low-HDI (41/507, 8.1%) and middle-HDI (132/1540, 8.6%) groups. After accounting for case-mix, laparoscopy was still associated with fewer overall complications (OR 0.55, 95% CI 0.42-0.71, pâ<â0.001) and SSIs (OR 0.22, 95% CI 0.14-0.33, pâ<â0.001). In propensity-score matched groups within low-/middle-HDI countries, laparoscopy was still associated with fewer overall complications (OR 0.23 95% CI 0.11-0.44) and SSI (OR 0.21 95% CI 0.09-0.45). CONCLUSION: A laparoscopic approach is associated with better outcomes and availability appears to differ by country HDI. Despite the profound clinical, operational, and financial barriers to its widespread introduction, laparoscopy could significantly improve outcomes for patients in low-resource environments. TRIAL REGISTRATION: NCT02179112
Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.
Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability
Pooled analysis of WHO Surgical Safety Checklist use and mortality after emergency laparotomy
Background The World Health Organization (WHO) Surgical Safety Checklist has fostered safe practice for 10 years, yet its place in emergency surgery has not been assessed on a global scale. The aim of this study was to evaluate reported checklist use in emergency settings and examine the relationship with perioperative mortality in patients who had emergency laparotomy. Methods In two multinational cohort studies, adults undergoing emergency laparotomy were compared with those having elective gastrointestinal surgery. Relationships between reported checklist use and mortality were determined using multivariable logistic regression and bootstrapped simulation. Results Of 12 296 patients included from 76 countries, 4843 underwent emergency laparotomy. After adjusting for patient and disease factors, checklist use before emergency laparotomy was more common in countries with a high Human Development Index (HDI) (2455 of 2741, 89.6 per cent) compared with that in countries with a middle (753 of 1242, 60.6 per cent; odds ratio (OR) 0.17, 95 per cent c.i. 0.14 to 0.21, P <0001) or low (363 of 860, 422 per cent; OR 008, 007 to 010, P <0.001) HDI. Checklist use was less common in elective surgery than for emergency laparotomy in high-HDI countries (risk difference -94 (95 per cent c.i. -11.9 to -6.9) per cent; P <0001), but the relationship was reversed in low-HDI countries (+121 (+7.0 to +173) per cent; P <0001). In multivariable models, checklist use was associated with a lower 30-day perioperative mortality (OR 0.60, 0.50 to 073; P <0.001). The greatest absolute benefit was seen for emergency surgery in low- and middle-HDI countries. Conclusion Checklist use in emergency laparotomy was associated with a significantly lower perioperative mortality rate. Checklist use in low-HDI countries was half that in high-HDI countries.Peer reviewe
Mortality of emergency abdominal surgery in high-, middle- and low-income countries
Background: Surgical mortality data are collected routinely in high-income countries, yet virtually no low- or middle-income countries have outcome surveillance in place. The aim was prospectively to collect worldwide mortality data following emergency abdominal surgery, comparing findings across countries with a low, middle or high Human Development Index (HDI).
Methods: This was a prospective, multicentre, cohort study. Self-selected hospitals performing emergency surgery submitted prespecified data for consecutive patients from at least one 2-week interval during July to December 2014. Postoperative mortality was analysed by hierarchical multivariable logistic regression.
Results: Data were obtained for 10 745 patients from 357 centres in 58 countries; 6538 were from high-, 2889 from middle- and 1318 from low-HDI settings. The overall mortality rate was 1â
6 per cent at 24 h (high 1â
1 per cent, middle 1â
9 per cent, low 3â
4 per cent; P < 0â
001), increasing to 5â
4 per cent by 30 days (high 4â
5 per cent, middle 6â
0 per cent, low 8â
6 per cent; P < 0â
001). Of the 578 patients who died, 404 (69â
9 per cent) did so between 24 h and 30 days following surgery (high 74â
2 per cent, middle 68â
8 per cent, low 60â
5 per cent). After adjustment, 30-day mortality remained higher in middle-income (odds ratio (OR) 2â
78, 95 per cent c.i. 1â
84 to 4â
20) and low-income (OR 2â
97, 1â
84 to 4â
81) countries. Surgical safety checklist use was less frequent in low- and middle-income countries, but when used was associated with reduced mortality at 30 days.
Conclusion: Mortality is three times higher in low- compared with high-HDI countries even when adjusted for prognostic factors. Patient safety factors may have an important role. Registration number: NCT02179112 (http://www.clinicaltrials.gov)
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