‘Bjerknes Compensation’ (BJC) refers to the anti-correlation observed between atmospheric and oceanic heat transport (AHT/OHT) variability, particularly on decadal to longer timescales that may be ...important to the predictability of the climate system. This study investigates the spread in BJC across fully coupled simulations of the Coupled Model Intercomparison Project Phase 6 (CMIP6) and critical processes (particularly related to sea ice and clouds) that may contribute to that spread. BJC on decadal to longer timescales is confirmed across all the simulations evaluated, and it is strongest in the northern hemisphere (NH) between 60°N-70°N. At these latitudes BJC appears primarily driven by the exchange of turbulent fluxes (sensible and latent) in Greenland, Iceland and the Barents Seas. Metrics to break down how sea ice and clouds uniquely modify the radiative balance of the polar atmosphere during anomalous OHT events are presented. These metrics quantify the impacts of sea ice and clouds on surface and top of atmosphere (latent, sensible, longwave and shortwave radiative) energy fluxes. Cloud responses tend to counter the clear sky impacts over the Marginal Ice Zone (MIZ). It is further shown that the degree of BJC present in a simulation at high latitudes is heavily influenced by the sensitivity of the sea ice to OHT, which is most influential over the MIZ. In conclusion, these results are qualitatively robust across models and explain the intermodel spread in NH BJC in the preindustrial control experiment.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Extreme weather and climate-related events occur in a particular place, by definition, infrequently. It is therefore challenging to detect systematic changes in their occurrence given the relative ...shortness of observational records. However, there is a clear interest from outside the climate science community in the extent to which recent damaging extreme events can be linked to human-induced climate change or natural climate variability. Event attribution studies seek to determine to what extent anthropogenic climate change has altered the probability or magnitude of particular events. They have shown clear evidence for human influence having increased the probability of many extremely warm seasonal temperatures and reduced the probability of extremely cold seasonal temperatures in many parts of the world. The evidence for human influence on the probability of extreme precipitation events, droughts, and storms is more mixed. Although the science of event attribution has developed rapidly in recent years, geographical coverage of events remains patchy and based on the interests and capabilities of individual research groups. The development of operational event attribution would allow a more timely and methodical production of attribution assessments than currently obtained on an ad hoc basis. For event attribution assessments to be most useful, remaining scientific uncertainties need to be robustly assessed and the results clearly communicated. This requires the continuing development of methodologies to assess the reliability of event attribution results and further work to understand the potential utility of event attribution for stakeholder groups and decision makers.
Fundamentos de Bioquímica Vegetal Correa-Salgado, María de Lourdes; Herrera-Feijoo, Robinson Jasmany; Ruiz-Sánchez, Clara Isabel ...
2024.
eBook
Odprti dostop
Se establecen los principios bioquímicos fundamentales que rigen el desarrollo de las plantas, explorando la composición y estructura de sus células. Además, se aborda la fotosíntesis como un proceso ...metabólico esencial. El metabolismo de biomoléculas, que incluye el transporte de nutrientes y la síntesis de carbohidratos, lípidos, proteínas y otros compuestos, es analizado en profundidad. Asimismo, se abordan temáticas cruciales como la respiración celular en plantas, la biosíntesis de metabolitos secundarios y el papel de las hormonas vegetales en el crecimiento y desarrollo. La enzimología vegetal, con énfasis en la cinética enzimática, se presenta como un componente esencial del metabolismo vegetal. Además, se examinan los mecanismos de defensa de las plantas frente al estrés abiótico y biótico, abordando la morfogénesis y los desafíos que enfrentan las plantas en su entorno. El libro concluye con una visión hacia el futuro en la investigación de la bioquímica vegetal.
Improving and homogenizing time and space reference systems on Earth and, more specifically, realizing the Terrestrial Reference Frame (TRF) with an accuracy of 1 mm and a long-term stability of ...0.1 mm/year are relevant for many scientific and societal endeavors. The knowledge of the TRF is fundamental for Earth and navigation sciences. For instance, quantifying sea level change strongly depends on an accurate determination of the geocenter motion but also of the positions of continental and island reference stations, such as those located at tide gauges, as well as the ground stations of tracking networks. Also, numerous applications in geophysics require absolute millimeter precision from the reference frame, as for example monitoring tectonic motion or crustal deformation, contributing to a better understanding of natural hazards. The TRF accuracy to be achieved represents the consensus of various authorities, including the International Association of Geodesy (IAG), which has enunciated geodesy requirements for Earth sciences. Moreover, the United Nations Resolution 69/266 states that the full societal benefits in developing satellite missions for positioning and Remote Sensing of the Earth are realized only if they are referenced to a common global geodetic reference frame at the national, regional and global levels. Today we are still far from these ambitious accuracy and stability goals for the realization of the TRF. However, a combination and co-location of all four space geodetic techniques on one satellite platform can significantly contribute to achieving these goals. This is the purpose of the GENESIS mission, a component of the FutureNAV program of the European Space Agency. The GENESIS platform will be a dynamic space geodetic observatory carrying all the geodetic instruments referenced to one another through carefully calibrated space ties. The co-location of the techniques in space will solve the inconsistencies and biases between the different geodetic techniques in order to reach the TRF accuracy and stability goals endorsed by the various international authorities and the scientific community. The purpose of this paper is to review the state-of-the-art and explain the benefits of the GENESIS mission in Earth sciences, navigation sciences and metrology. This paper has been written and supported by a large community of scientists from many countries and working in several different fields of science, ranging from geophysics and geodesy to time and frequency metrology, navigation and positioning. As it is explained throughout this paper, there is a very high scientific consensus that the GENESIS mission would deliver exemplary science and societal benefits across a multidisciplinary range of Navigation and Earth sciences applications, constituting a global infrastructure that is internationally agreed to be strongly desirable.
Graphical Abstract
The Antarctic ice sheet mass balance is a major component of the sea level
budget and results from the difference of two fluxes of a similar magnitude:
ice flow discharging in the ocean and net snow ...accumulation on the ice sheet
surface, i.e. the surface mass balance (SMB). Separately modelling ice
dynamics and SMB is the only way to project future trends.
In addition, mass balance studies frequently use regional climate models
(RCMs) outputs as an alternative to observed fields because SMB observations
are particularly scarce on the ice sheet. Here we evaluate new simulations of
the polar RCM MAR forced by three reanalyses, ERA-Interim, JRA-55, and MERRA-2,
for the period 1979–2015, and we compare MAR results to the last outputs of
the RCM RACMO2 forced by ERA-Interim. We show that MAR and RACMO2 perform
similarly well in simulating coast-to-plateau SMB gradients, and we find no
significant differences in their simulated SMB when integrated over the ice
sheet or its major basins. More importantly, we outline and quantify missing
or underestimated processes in both RCMs. Along stake transects, we show that
both models accumulate too much snow on crests, and not enough snow in
valleys, as a result of drifting snow transport fluxes not included in MAR
and probably underestimated in RACMO2 by a factor of 3. Our results tend
to confirm that drifting snow transport and sublimation fluxes are much
larger than previous model-based estimates and need to be better resolved and
constrained in climate models. Sublimation of precipitating particles in
low-level atmospheric layers is responsible for the significantly lower
snowfall rates in MAR than in RACMO2 in katabatic channels at the ice sheet
margins. Atmospheric sublimation in MAR represents 363 Gt yr−1 over the grounded ice sheet for the year 2015, which is 16 %
of the simulated snowfall loaded at the ground. This estimate is consistent
with a recent study based on precipitation radar observations and is more
than twice as much as simulated in RACMO2 because of different time
residence of precipitating particles in the atmosphere. The remaining spatial
differences in snowfall between MAR and RACMO2 are attributed to differences
in advection of precipitation with snowfall particles being likely advected too
far inland in MAR.
This monograph provides state-of-the-art numerical methods, procedures and algorithms in the field of computational geoscience, based on the authors' own work during the last decade.
Data Assimilation comprehensively covers data assimilation and inverse methods, including both traditional state estimation and parameter estimation. This text and reference focuses on various ...popular data assimilation methods, such as weak and strong constraint variational methods and ensemble filters and smoothers. It is demonstrated how the different methods can be derived from a common theoretical basis, as well as how they differ and/or are related to each other, and which properties characterize them, using several examples. It presents the mathematical framework and derivations in a way which is common for any discipline where dynamics is merged with measurements. The mathematics level is modest, although it requires knowledge of basic spatial statistics, Bayesian statistics, and calculus of variations. Readers will also appreciate the introduction to the mathematical methods used and detailed derivations, which should be easy to follow, are given throughout the book. The codes used in several of the data assimilation experiments are available on a web page. The focus on ensemble methods, such as the ensemble Kalman filter and smoother, also makes it a solid reference to the derivation, implementation and application of such techniques. Much new material, in particular related to the formulation and solution of combined parameter and state estimation problems and the general properties of the ensemble algorithms, is available here for the first time. The 2nd edition includes a partial rewrite of Chapters 13 an 14, and the Appendix. In addition, there is a completely new Chapter on 'Spurious correlations, localization and inflation', and an updated and improved sampling discussion in Chap 11.
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