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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.

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.

Stroeve J.C.,University of Colorado at Boulder | Kattsov V.,Voeikov Main Geophysical Observatory | Barrett A.,University of Colorado at Boulder | Serreze M.,University of Colorado at Boulder | And 3 more authors.
Geophysical Research Letters | Year: 2012

The rapid retreat and thinning of the Arctic sea ice cover over the past several decades is one of the most striking manifestations of global climate change. Previous research revealed that the observed downward trend in September ice extent exceeded simulated trends from most models participating in the World Climate Research Programme Coupled Model Intercomparison Project Phase 3 (CMIP3). We show here that as a group, simulated trends from the models contributing to CMIP5 are more consistent with observations over the satellite era (1979-2011). Trends from most ensemble members and models nevertheless remain smaller than the observed value. Pointing to strong impacts of internal climate variability, 16% of the ensemble member trends over the satellite era are statistically indistinguishable from zero. Results from the CMIP5 models do not appear to have appreciably reduced uncertainty as to when a seasonally ice-free Arctic Ocean will be realized. © 2012. American Geophysical Union. All Rights Reserved.

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.

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

The results of hourly measurements of sea roughness and hydrometeorological parameters, which were automatically taken from special buoys over a long period of time, were used. These buoys were located in the open regions of both the Atlantic and Pacific oceans in different climatic zones; the mean water-surface temperature around the buoys varies from 1-3°C to 26-28°C. In addition to measurement results, the tables contain data on the spectral density of sea roughness for a wide range of frequencies. An analysis of these data, which was made for a short-wave region of the wind-wave spectrum, for the first time revealed a noticeable water temperature dependence of the spectral density of wind waves within the frequency range 0.30-0.40 Hz, which corresponds to wave lengths of 9-4 m. The presence of such dependence is explained by a rapid temperature change in kinematic sea-water viscosity. Earlier, we indicated the temperature dependence of only very short spectral components that relate to a centimetric wavelength range. The statistical significance of the water temperature effect on the spectral density of waves of the indicated frequency is supported by the results of a variance analysis. Temperature variations in the parameter of sea-surface roughness, which is determined, first of all, by the energy of the spectral shortwave region, are estimated. Altimetry is the basic method which is used in remotely determining the velocity of near-water wind. This method allows one to obtain records of deviations of the sea surface from the geoid surface and to calculate (on the basis of these records) the spectral density of wave components of almost any frequency. It is known that the wave-spectrum components in the region of low frequencies are almost always affected by ripple. Consequently, the energy of these components is determined not only by wind forcing, and only the components in the range of frequencies exceeding approximately 0.3 Hz are purely windy. Therefore, using the results of sea-surface altimetry in order to determine the velocity of near-water wind, one should use the spectral densities of wave components in this frequency region. The water-temperature dependence of the spectral density of short wind waves is manifested only in a certain frequency interval, which supports this recommendation. © 2012 Pleiades Publishing, Ltd.

Titova E.A.,Voeikov Main Geophysical Observatory | Karol' I.L.,Voeikov Main Geophysical Observatory
Izvestiya - Atmospheric and Ocean Physics | Year: 2010

Having applied the method of discriminant analysis to the TOMS data of satellite sounding of the total ozone content (TOC) in the March months of 1979-2008, the authors could make a new estimate of the TOC field variability in the Northern Hemisphere and interlongitudinal regularities of its changes under the action of climatic variability. The effects of temperature variations in the polar stratosphere, El Niño, and quasi-biennial oscillation (QBO) have proven comparable and reach 80 DU in some regions. The influence of the Arctic Oscillation (AO) reaches 40 DU. The regions of TOC variations and their location and dimensions change depending on the phases of QBO, AO, and El Niño-Southern Oscillation (ENSO). Three regions of increased TOC-over Europe, Eastern Siberia, and the Pacific Ocean-are formed in years with a warm stratosphere. A compensating TOC decrease takes place in the tropics and over Greenland. In the years of El Niño and the easterly QBO phase, the TOC increases over Europe and drops over the central Pacific, as well as to the south from 45° N. The AO controls the ozone growth over most of Eurasia at tem perate latitudes and its weak drop over the Atlantic. It was impossible to obtain such quantitative estimates with the use of methods based on an independent analysis of the TOC series at individual points of the coor-dinate grid. Testing with the Monte Carlo method confirmed that the results obtained are significant with a probability of 95-99.9%. © Pleiades Publishing, Ltd., 2010.

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.

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.

Shkolnik I.M.,Voeikov Main Geophysical Observatory | Efimov S.V.,Voeikov Main Geophysical Observatory
Environmental Research Letters | Year: 2013

Decadal long simulations of atmospheric circulation in the high latitudes have been carried out using a multiscale atmospheric modeling system that consists of MGO global and regional atmospheric models with respective resolutions of 200, 50 and 25 km in the horizontal. The detailed analysis of extratropical cyclone activity including activity of polar mesocyclones has been conducted for the winter season using an advanced cyclone identification and tracking scheme. To enhance the applicability of high-resolution regional atmospheric modeling in the context of detailed general atmospheric circulation analysis, an end-to-end approach for cyclone trajectory calculation on a unified global and regional grid has been proposed. It has been shown that increasing modeling resolution in the high latitudes allows one to more realistically simulate the activity of baroclinic waves and the thermal regime of the Arctic troposphere. The statistical structure of cyclonic activity has been investigated depending on the spatial resolution of the modeling system and compared with that in the reanalyses and satellite-derived analyses. The performance of the atmospheric models in the simulation of extreme cyclones is evaluated. © 2013 IOP Publishing Ltd.

Shkolnik I.M.,Voeikov Main Geophysical Observatory | Nadyozhina E.D.,Voeikov Main Geophysical Observatory | Pavlova T.V.,Voeikov Main Geophysical Observatory | Molkentin E.K.,Voeikov Main Geophysical Observatory | Semioshina A.A.,Voeikov Main Geophysical Observatory
Environmental Research Letters | Year: 2010

An approach to ground thermodynamics description using a coupled system of atmospheric regional climate and ground heat transfer models is improved by accounting for the time varying snow density. The simulations are compared to available observational analyses, and the sensitivity of the ground thermal regime to variable snow density is analysed. Projected changes of the ground thermal regime in the 21st century relative to the late 20th century are shown and compared to earlier estimates. © 2010 IOP Publishing Ltd.

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