Mathematics
Recent Submissions
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A generalized poloidal-toroidal decomposition and an absolute measure of helicity
(IOP Publishing, 2018-11-12)In fluid mechanics and magneto-hydrodynamics it is often useful to decompose a vector field into poloidal and toroidal components. In a spherical geometry, the poloidal component contains all of the radial part of the ... -
An unexpected disruption of the atmospheric quasi-biennial oscillation
(American Association for the Advancement of Science, 2016-09-23)One of the most repeatable phenomena seen in the atmosphere, the quasi-biennial oscillation (QBO) between prevailing eastward and westward wind jets in the equatorial stratosphere (approximately 16 to 50 kilometers altitude), ... -
Contrasting interannual atmospheric CO2 variabilities and their terrestrial mechanisms for two types of El Niños
(European Geosciences Union (EGU) / Copernicus Publications, 2018-07-19)El Niño has two different flavors, eastern Pacific (EP) and central Pacific (CP) El Niños, with different global teleconnections. However, their different impacts on the interannual carbon cycle variability remain unclear. ... -
Challenges in constraining anthropogenic aerosol effects on cloud radiative forcing using present-day spatiotemporal variability
(National Academy of Sciences, 2016-05-24)A large number of processes are involved in the chain from emissions of aerosol precursor gases and primary particles to impacts on cloud radiative forcing. Those processes are manifest in a number of relationships that ... -
On Elementary Estimates of Arithmetic Sums for Polynomial Rings over Finite Fields
(Elsevier, 2018)In this paper, a simple and elementary method is given for deriving estimates of sums of arithmetic functions in Fq[t]. The method is the function eld analogue of a result rst proved by Stefan A. Burr in 1973 in the number ... -
Quantification of extremal dependence in spatial natural hazard footprints: independence of windstorm gust speeds and its impact on aggregate losses
(European Geosciences Union (EGU) / Copernicus Publications, 2018-11-08)Natural hazards, such as European windstorms, have widespread effects that result in insured losses at multiple locations throughout a continent. Multivariate extreme-value statistical models for such environmental phenomena ... -
Constraining the instantaneous aerosol influence on cloud albedo
(National Academy of Sciences, 2017-04-26)Much of the uncertainty in estimates of the anthropogenic forcing of climate change comes from uncertainties in the instantaneous effect of aerosols on cloud albedo, known as the Twomey effect or the radiative forcing from ... -
A simple tool for refining GCM water availability projections, applied to Chinese catchments (discussion paper)
(European Geosciences Union (EGU) / Copernicus Publications, 2018-04-27)There is a growing desire for reliable 21st-century projections of water availability at the regional scale. Global climate models (GCMs) are typically used together with global hydrological models (GHMs) to generate such ... -
The importance of fronts for extreme precipitation
(American Geophysical Union (AGU) / Wiley, 2013-09-21)Extratropical cyclones and their associated frontal systems are well known to be related to heavy precipitation events. Here an objective method is used to directly link extreme precipitation events with atmospheric fronts, ... -
Can Climate Models Capture the Structure of Extratropical Cyclones?
(American Meteorological Society, 2010-04-01)Composites of wind speeds, equivalent potential temperature, mean sea level pressure, vertical velocity, and relative humidity have been produced for the 100 most intense extratropical cyclones in the Northern Hemisphere ... -
Skillful long-range prediction of European and North American winters
(American Geophysical Union (AGU) / Wiley, 2014-03-28)Until recently, long-range forecast systems showed only modest levels of skill in predicting surface winter climate around the Atlantic Basin and associated fluctuations in the North Atlantic Oscillation at seasonal lead ... -
High risk of unprecedented UK rainfall in the current climate
(Springer Nature, 2017-07-24)In winter 2013/14 a succession of storms hit the UK leading to record rainfall and flooding in many regions including south east England. In the Thames river valley there was widespread flooding, with clean-up costs of ... -
The status and challenge of global fire modelling
(European Geosciences Union (EGU) / Copernicus Publications, 2016-01-25)Biomass burning impacts vegetation dynamics, biogeochemical cycling, atmospheric chemistry, and climate, with sometimes deleterious socio-economic impacts. Under future climate projections it is often expected that the ... -
On the causes of trends in the seasonal amplitude of atmospheric CO2
(Wiley, 2017-08-15)No consensus has yet been reached on the major factors driving the observed increase in the seasonal amplitude of atmospheric CO2 in the northern latitudes. In this study, we used atmospheric CO2 records from 26 northern ... -
Reconciling global-model estimates and country reporting of anthropogenic forest CO2 sinks
(Springer Nature, 2018-09-24)Achieving the long-term temperature goal of the Paris Agreement requires forest-based mitigation. Collective progress towards this goal will be assessed by the Paris Agreement’s Global stocktake. At present, there is a ... -
Lower land-use emissions responsible for increased net land carbon sink during the slow warming period
(Springer Nature, 2018-08-20)The terrestrial carbon sink accelerated during 1998–2012, concurrently with the slow warming period, but the mechanisms behind this acceleration are unclear. Here we analyse recent changes in the net land carbon sink (NLS) ... -
Widespread seasonal compensation effects of spring warming on northern plant productivity
(Springer Nature, 2018-10-03)Climate change is shifting the phenological cycles of plants1, thereby altering the functioning of ecosystems, which in turn induces feedbacks to the climate system2. In northern (north of 30° N) ecosystems, warmer springs ... -
Historical carbon dioxide emissions caused by land-use changes are possibly larger than assumed
(Springer Nature, 2017-01-30)The terrestrial biosphere absorbs about 20% of fossil-fuel CO 2 emissions. The overall magnitude of this sink is constrained by the difference between emissions, the rate of increase in atmospheric CO 2 concentrations, and ... -
Radiological progression of end colostomy trephine diameter and area
(Wiley, 2018-10-24)Background Development of a parastomal hernia is common following abdominoperineal excision (APE). The true incidence is difficult to assess fully owing to differing lengths of follow‐up and techniques used to assess ... -
Carbon budgets for 1.5 and 2 °C targets lowered by natural wetland and permafrost feedbacks
(Springer Nature, 2018-07-09)Global methane emissions from natural wetlands and carbon release from permafrost thaw have a positive feedback on climate, yet are not represented in most state-of-the-art climate models. Furthermore, a fraction of the ...