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Saint Petersburg, Russia

Bortkovskii R.S.,Voeikov Main Geophysical Observatory
Izvestiya - Atmospheric and Ocean Physics | Year: 2012

Sea ice differs significantly from that formed by frozen fresh water in its abundance of pores. The pores are filled either by liquid, i. e., by brine, or by gas, i. e., by air. The gas permeability of the pore visibly exceeds the gas permeability of continuous solid ice with no pores. Expressions for the diffusion coefficients of oxygen and CO 2 through sea ice at a given ice temperature and salinity are obtained. Calculations of the gas transfer for the central part of the Chukchi Sea are fulfilled. Numerical experiments have shown that gas fluxes through thin sea ice are not negligibly small. The fluxes significantly decrease only if one-year ice thickness exceeds about 100 cm. © 2012 Pleiades Publishing, Ltd.

Sall' M.A.,Voeikov Main Geophysical Observatory
Russian Meteorology and Hydrology | Year: 2015

The idea is developed that the consideration of the climate change even in the form of the linear trend can provoke the dramatic nonlinear increase in the probability of adverse weather events. Considered is a possibility of using the concept of heteroscedasticity (the heterogeneity of the variance of the random error of the regression model) for studying climatic time series. Discussed are the cases of temporal and factor heteroscedasticity. Introduced is a concept of the trend-type climate risk. Considered are the issues related to the risk assessment in global climate models. © 2015, Allerton Press, Inc.

McVicar T.R.,CSIRO | Roderick M.L.,Australian National University | Donohue R.J.,CSIRO | Li L.T.,CSIRO | And 11 more authors.
Journal of Hydrology | Year: 2012

In a globally warming climate, observed rates of atmospheric evaporative demand have declined over recent decades. Several recent studies have shown that declining rates of evaporative demand are primarily governed by trends in the aerodynamic component (primarily being the combination of the effects of wind speed (u) and atmospheric humidity) and secondarily by changes in the radiative component. A number of these studies also show that declining rates of observed near-surface u (termed 'stilling') is the primary factor contributing to declining rates of evaporative demand. One objective of this paper was to review and synthesise the literature to assess whether stilling is a globally widespread phenomenon. We analysed 148 studies reporting terrestrial u trends from across the globe (with uneven and incomplete spatial distribution and differing periods of measurement) and found that the average trend was -0.014ms -1a -1 for studies with more than 30 sites observing data for more than 30years, which confirmed that stilling was widespread. Assuming a linear trend this constitutes a -0.7ms -1 change in u over 50years. A second objective was to confirm the declining rates of evaporative demand by reviewing papers reporting trends in measured pan evaporation (E pan) and estimated crop reference evapotranspiration (ET o); average trends were -3.19mma -2 (n=55) and -1.31mma -2 (n=26), respectively. A third objective was to assess the contribution to evaporative demand trends that the four primary meteorological variables (being u; atmospheric humidity; radiation; and air temperature) made. The results from 36 studies highlighted the importance of u trends. We also quantified the sensitivity of rates of evaporative demand to changes in u and how the relative contributions of the aerodynamic and radiative components change seasonally over the globe. Our review: (i) shows that terrestrial stilling is widespread across the globe; (ii) confirms declining rates of evaporative demand; and (iii) highlights the contribution u has made to these declining evaporative rates. Hence we advocate that assessing evaporative demand trends requires consideration of all four primary meteorological variables (being u, atmospheric humidity, radiation and air temperature). This is particularly relevant for long-term water resource assessment because changes in u exert greater influence on energy-limited water-yielding catchments than water-limited ones. © 2011.

Kobysheva N.V.,Voeikov Main Geophysical Observatory
Russian Meteorology and Hydrology | Year: 2014

Presented are the recommendations for the content of the national segment of the Global Framework for Climate Services based on the long-term interaction with the users of climatological information. The "Research Studies" section includes the method assessing the risk of credibility to the climatic fore casting. Discussed are the methods of disaster risk computation, risk management, and adaptation to the climate change. It is asserted that normative parameters are mainly taken into account by operational services of technical sectors. Analyzed are the normative documents of the Russian Federation that are up dated and agreed with Eurocodes and worked out in partnership with Roshydromet. To build up the capacity of climate ser vices, it is recommended to use up-to-date training facilities for graduate students and further education courses. Considered are the ways of interaction between users and climatologists. © 2014 Allerton Press, Inc.

Overland J.E.,National Oceanic and Atmospheric Administration | Wang M.,University of Washington | Bond N.A.,University of Washington | Walsh J.E.,University of Alaska Fairbanks | And 2 more authors.
Journal of Climate | Year: 2011

Climate projections at regional scales are in increased demand from management agencies and other stakeholders. While global atmosphere-ocean climate models provide credible quantitative estimates of future climate at continental scales and above, individual model performance varies for different regions, variables, and evaluation metrics-a less than satisfying situation. Using the high-latitude Northern Hemisphere as a focus, the authors assess strategies for providing regional projections based on global climate models. Starting with a set of model results obtained from an "ensemble of opportunity," the core of this procedure is to retain a subset of models through comparisons of model simulations with observations at both continental and regional scales. The exercise is more one of model culling than model selection. The continental-scale evaluation is a check on the large-scale climate physics of the models, and the regional-scale evaluation emphasizes variables of ecological or societal relevance. An additional consideration is given to the comprehensiveness of processes included in the models. In many but not all applications, different results are obtained from a reduced set of models compared to relying on the simple mean of all available models. For example, in the Arctic the top-performing models tend to be more sensitive to greenhouse forcing than the poorer-performing models. Because of the mostly unexplained inconsistencies in model performance under different selection criteria, simple and transparent evaluation methods are favored. The use of a single model is not recommended. For some applications, no model may be able to provide a suitable regional projection. The use of model evaluation strategies, as opposed to relying on simple averages of ensembles of opportunity, should be part of future synthesis activities such as the upcoming Fifth Assessment Report of the Intergovernmental Panel on Climate Change. © 2011 American Meteorological Society.

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