ABSTRACT
We describe the Northern Hemisphere terrestrial snow water equivalent (SWE) time series covering 1979-2018, containing daily, monthly and monthly bias-corrected SWE estimates. The GlobSnow v3.0 SWE dataset combines satellite-based passive microwave radiometer data (Nimbus-7 SMMR, DMSP SSM/I and DMSP SSMIS) with ground based synoptic snow depth observations using bayesian data assimilation, incorporating the HUT Snow Emission model. The original GlobSnow SWE retrieval methodology has been further developed and is presented in its current form in this publication. The described GlobSnow v3.0 monthly bias-corrected dataset was applied to provide continental scale estimates on the annual maximum snow mass and its trend during the period 1980 to 2018.
ABSTRACT
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
ABSTRACT
Warming surface temperatures have driven a substantial reduction in the extent and duration of Northern Hemisphere snow cover1-3. These changes in snow cover affect Earth's climate system via the surface energy budget, and influence freshwater resources across a large proportion of the Northern Hemisphere4-6. In contrast to snow extent, reliable quantitative knowledge on seasonal snow mass and its trend is lacking7-9. Here we use the new GlobSnow 3.0 dataset to show that the 1980-2018 annual maximum snow mass in the Northern Hemisphere was, on average, 3,062 ± 35 billion tonnes (gigatonnes). Our quantification is for March (the month that most closely corresponds to peak snow mass), covers non-alpine regions above 40° N and, crucially, includes a bias correction based on in-field snow observations. We compare our GlobSnow 3.0 estimates with three independent estimates of snow mass, each with and without the bias correction. Across the four datasets, the bias correction decreased the range from 2,433-3,380 gigatonnes (mean 2,867) to 2,846-3,062 gigatonnes (mean 2,938)-a reduction in uncertainty from 33% to 7.4%. On the basis of our bias-corrected GlobSnow 3.0 estimates, we find different continental trends over the 39-year satellite record. For example, snow mass decreased by 46 gigatonnes per decade across North America but had a negligible trend across Eurasia; both continents exhibit high regional variability. Our results enable a better estimation of the role of seasonal snow mass in Earth's energy, water and carbon budgets.
Subject(s)
Geographic Mapping , Snow , Spatio-Temporal Analysis , Bias , Carbon/analysis , Earth, Planet , Global Warming/statistics & numerical data , History, 20th Century , History, 21st Century , North America , Seasons , Siberia , Snow/chemistry , Temperature , Uncertainty , Water/analysisABSTRACT
BACKGROUND: The purpose of this study was to determine the prevalence of atrial fibrillation (AF) in the general population and to validate an administrative diagnosis register, ie, the National Patient Register (NPR), and an electrocardiography (ECG) database in estimating disease prevalence. METHODS: The study was conducted in a well defined region in northern Sweden (population n=75,945) which consists of one hospital and eleven primary health care centers. Subjects with AF were identified by searching the combined inpatient and outpatient International Classification of Diseases (ICD)-based NPR (ICD-10 code I48) and an ECG database with computer-interpreted AF from January 1, 2004 to December 31, 2010. All identified cases with AF were validated. RESULTS: AF was confirmed in 2,274 patients. The overall prevalence was 3.0% (3.4% in men and 2.6% in women). AF prevalence rose steadily with age, and was 16.8% in patients aged 75 years and older and 21.9% in patients 85 years and older. Of all patients with validated AF, the NPR identified 93.2%. The ECG database identified an additional 6.8%, of which 81% were over 70 years of age. According to the NPR, the proportion of false positives and false negatives was 3.5% and 6.8%, respectively. The corresponding figure for the ECG database was 11.3% and 9.2%, respectively. CONCLUSION: Our study shows a high prevalence of AF, especially among the elderly. Searching the ECG database enhanced the detection of AF. The reliability of the NPR was high, with a relatively low proportion of false positives and negatives.
