Climate variations in the Northern Hemisphere based on the use of an atmosphere-ocean IPCC model

Forced and natural variability of modelled and observed Atlantic Ocean temperature and Atlantic Meridional Overturning Circulation (AMOC) is studied. In the observations and in a forced climate model run, we find increasing temperature at 1000m in the Atlantic (20N). SVD analysis shows that, for both model data and observations, a high index of North Atlantic Oscillation (NAO) corresponds to negative temperature anomaly at 1000m to the north of 55N, although geographical details of temperature anomaly distribution are different for the model and observations. Particular attention has been paid to the influence of the fresh water flux due to the present global warning on the slowing down of the AMOC. It is shown that fresh water flux change is only a secondary cause of reduced AMOC in global warming conditions, while heat flux change is probably the main reason. Finally, it is shown that internal model AMOC variability is positively correlated with the near-surface air temperature in Atlantic-European Arctic sector on a 10-year time scale

Changes in temperature and precipitation extremes in the IPCC ensemble of global coupled model simulations

Temperature and precipitation extremes and their potential future changes are evaluated in an ensemble of global coupled climate models participating in the Intergovernmental Panel on Climate Change (IPCC) diagnostic exercise for the Fourth Assessment Report (AR4). Climate extremes are expressed in terms of 20-yr return values of annual extremes of near-surface temperature and 24-h precipitation amounts. The simulated changes in extremes are documented for years 2046–65 and 2081–2100 relative to 1981–2000 in experiments with the Special Report on Emissions Scenarios (SRES) B1, A1B, and A2 emission scenarios. Overall, the climate models simulate present-day warm extremes reasonably well on the global scale, as compared to estimates from reanalyses. The model discrepancies in simulating cold extremes are generally larger than those for warm extremes, especially in sea ice–covered areas. Simulated present-day precipita-tion extremes are plausible in the extratropics, but uncertainties in extreme precipitation in the Tropics are very large, both in the models and the available observationally based datasets. Changes in warm extremes generally follow changes in the mean summertime temperature. Cold ex-tremes warm faster than warm extremes by about 30%–40%, globally averaged. The excessive warming of cold extremes is generally confined to regions where snow and sea ice retreat with global warming. With th

Evaluation of Arctic Sea Ice Thickness Simulated by AOMIP Models

We compare results from six AOMIP model simulations with estimates of sea ice thickness obtained from ICESat, moored and submarine-based upward looking sensors, airborne electromagnetic measurements and drill holes. Our goal is to find patterns of model performance to guide model improvement. The satellite data is pan-arctic from 2004-2008, ice-draft data is from moored instruments in Fram Strait, the Greenland Sea and the Beaufort Sea from 1992-2008 and from submarines from 1975-2000. The drill hole data are from the Laptev and East Siberian marginal seas from 1982-1986 and from coastal stations from 1998-2009. While there are important caveats when comparing modeled results with measurements from different platforms and time periods such as these, the models agree well with moored ULS data. In general, the AOMIP models underestimate the thickness of measured ice thicker than about 2 m and overestimate thickness of ice thinner than 2 m. The simulated results are poor over the fast ice and marginal seas of the Siberian shelves. Averaging over all observational data sets, the better correlations and smaller differences from observed thickness are from the ECCO2 and UW models

Marine Dynamics and Productivity in the Bay of Bengal

The Bay of Bengal provides important ecosystem services to the Bangladesh delta. It is also subject to the consequences of climate change as monsoon atmospheric circulation and fresh water input from the major rivers are the dominating influences. Changes in marine circulation will affect patterns of biological production through alterations in the supply of nutrients to photosynthesising plankton. Productivity in the northern Bay will also be sensitive to changes in riverborne nutrients. In turn, these changes could influence potential fish catch. The Bay also affects the physical environment of Bangladesh: relative sea-level rise is expected to be in the range of 0.5–1.7 m by 2100, and changing climate could affect the development of tropical cyclones over the Bay

Changing Northern Hemisphere storm tracks in an ensemble of IPCC climate change simulations

Winter storm-track activity over the Northern Hemisphere and its changes in a greenhouse gas scenario (the Special Report on Emission Scenarios A1B forcing) are computed from an ensemble of 23 single runs from 16 coupled global climate models (CGCMs). All models reproduce the general structures of the observed climatological storm-track pattern under present-day forcing conditions. Ensemble mean changes resulting from anthropogenic forcing include an increase of baroclinic wave activity over the eastern North Atlantic, amounting to 5%–8% by the end of the twenty-first century. Enhanced activity is also found over the Asian continent and over the North Pacific near the Aleutian Islands. At high latitudes and over parts of the subtropics, activity is reduced. Variations of the individual models around the ensemble average signal are not small, with a median of the pattern correlation near r = 0.5. There is, however, no evidence for a link between deviations in present-day climatology and deviations with respect to climate change

North Atlantic simulations in Coordinated Ocean-ice Reference Experiments phase II (CORE-II). Part I: Mean states

Simulation characteristics from eighteen global ocean–sea-ice coupled models are presented with a focus on the mean Atlantic meridional overturning circulation (AMOC) and other related fields in the North Atlantic. These experiments use inter-annually varying atmospheric forcing data sets for the 60-year period from 1948 to 2007 and are performed as contributions to the second phase of the Coordinated Ocean-ice Reference Experiments (CORE-II). The protocol for conducting such CORE-II experiments is summarized. Despite using the same atmospheric forcing, the solutions show significant differences. As most models also differ from available observations, biases in the Labrador Sea region in upper-ocean potential temperature and salinity distributions, mixed layer depths, and sea-ice cover are identified as contributors to differences in AMOC. These differences in the solutions do not suggest an obvious grouping of the models based on their ocean model lineage, their vertical coordinate representations, or surface salinity restoring strengths. Thus, the solution differences among the models are attributed primarily to use of different subgrid scale parameterizations and parameter choices as well as to differences in vertical and horizontal grid resolutions in the ocean models. Use of a wide variety of sea-ice models with diverse snow and sea-ice albedo treatments also contributes to these differences. Based on the diagnostics considered, the majority of the models appear suitable for use in studies involving the North Atlantic, but some models require dedicated development effort

Моделирование разливов нефти в море для планирования мероприятий по обеспечению экологической безопасности при реализации нефтегазовых проектов. Часть 2. Особенности реализации прикладных задач

In the second part of the article, peculiarities of the oil spills modeling for applied problems are marked, and some examples of simulation results are submitted. As an example of a oil spill model, which able to ensure the needs of information support of applied problems, the description of model SPILLMOD is presented in the final part of the article. Also a set of parameterizations allowing to take into account the role of hydrometeorological conditions for use skimmers and booms in oil spill response operations are described.Во второй части статьи отмечены особенности постановки задачи моделировании разливов нефти для (подготовки планов ликвидации разливов нефти в море (ПЛАРН), анализа совокупной экологической выгоды при выборе стратегий реагирования на разливы (АСЭВ) и оценки воздействия на окружающую среду (ОВОС), представлены примеры результатов моделирования. В качестве примера модели нефтяного разлива, обеспечивающей потребности информационного обеспечения ПЛАРН и АСЭВ, в заключительной части статьи приведено описание модели SPILLMOD с набором параметризаций, позволяющих учитывать роль гидрометеорологических условий при использовании в операции ЛАРН скиммеров и боновых заграждени

The Hydrologic Responses of Semiarid Watersheds to the Cultivation of Switchgrass (Panicum virgatum L.)

Due in part to the very recent influx of federal and state policies promoting the development of ethanol as a gasoline additive, switchgrass (Panicum virgatum L.) has received much attention. Nevertheless, investigations of the hydrological responses to switchgrass production are few, with those existing largely interested in the Southern or Upper Midwestern regions of the United States. First, a contextualization of switchgrass as a potential biofuel crop vis-à-vis the history of land use change in the Great Plains region of the US is presented. Then, an investigation of the hydrologic responses of two Great Plains watersheds: a 1641 km2 portion of the Middle North Canadian watershed and the 1061 km2 Skeleton Creek Watershed to the cultivation of switchgrass using the semidistributed Soil and Water Assessment Tool (SWAT) hydrological model, specifically the hydrologic responses on total monthly and seasonal discharge, and evapotranspiration, are evaluated. Model results indicate that switchgrass cultivation is associated with decreased spring and summer seasonal runoff and increased spring and summer evapotranspiration relative to those under native land uses including native range grass and winter wheat. When the confounding impacts of changing precipitation and temperature patterns associated with climate change are considered, the impact of switchgrass cultivation on wintertime hydrology is a function of the particular General Circulation Model (GCM) utilized. With the addition of switchgrass, changes in surface runoff are amplified during the winter and summer and changes in evapotranspiration are amplified during all three seasons. Depending on the GCM utilized, either climate change or land use change (switchgrass cultivation) was the dominant driver of change in surface runoff while switchgrass cultivation was the major driver of changes in evapotranspiration. Therefore, any cultivation of switchgrass for biofuel production in the Great Plains region of the US must take into account hydrologic impacts and be accompanied by programs to ensure the sustainability of water supplies

Upper mixed layer temperature anomalies at the North Atlantic storm-track zone

Synoptic sea surface temperature anomalies (SSTAs) were determined as a result of separation of time scales smaller than 183 days. The SSTAs were investigated using daily data of ocean weather station "C" (52.75°N; 35.5°W) from 1 January 1976 to 31 December 1980 (1827 days). There were 47 positive and 50 negative significant SSTAs (lifetime longer than 3 days, absolute value greater than 0.10 °C) with four main intervals of the lifetime repetitions: 1. 4–7 days (45% of all cases), 2. 9–13 days (20–25%), 3. 14–18 days (10–15%), and 4. 21–30 days (10–15%) and with a magnitude 1.5–2.0 °C. An upper layer balance model based on equations for temperature, salinity, mechanical energy (with advanced parametrization), state (density), and drift currents was used to simulate SSTA. The original method of modelling taking into account the mean observed temperature profiles proved to be very stable. The model SSTAs are in a good agreement with the observed amplitudes and phases of synoptic SSTAs during all 5 years. Surface heat flux anomalies are the main source of SSTAs. The influence of anomalous drift heat advection is about 30–50% of the SSTA, and the influence of salinity anomalies is about 10–25% and less. The influence of a large-scale ocean front was isolated only once in February-April 1978 during all 5 years. Synoptic SSTAs develop just in the upper half of the homogeneous layer at each winter. We suggest that there are two main causes of such active sublayer formation: 1. surface heat flux in the warm sectors of cyclones and 2. predominant heat transport by ocean currents from the south. All frequency functions of the ocean temperature synoptic response to heat and momentum surface fluxes are of integral character (red noise), though there is strong resonance with 20-days period of wind-driven horizontal heat advection with mixed layer temperature; there are some other peculiarities on the time scales from 5.5 to 13 days. Observed and modelled frequency functions seem to be in good agreement