Simulation of modern climate with the new version of the INM RAS climate model

The INMCM5.0 numerical model of the Earth’s climate system is presented, which is an evolution from the previous version, INMCM4.0. A higher vertical resolution for the stratosphere is applied in the atmospheric block. Also, we raised the upper boundary of the calculating area, added the aerosol block, modified parameterization of clouds and condensation, and increased the horizontal resolution in the ocean block. The program implementation of the model was also updated. We consider the simulation of the current climate using the new version of the model. Attention is focused on reducing systematic errors as compared to the previous version, reproducing phenomena that could not be simulated correctly in the previous version, and modeling the problems that remain unresolved.     

Role of wind and thermal forcing in the formation of the water circulation variability in the Japan/East Sea Central Basin in 1958–2006

Based on the numerical experiment on simulation of the Japan/East Sea (JES) water circulation response to the atmospheric forcing for 1958–2006, the analysis is made of its long-term variability in the JES Central Basin (CB). It was found that during the climatic year, the circulation remains cyclonic, strengthening in spring and weakening in autumn. The analysis of mean relative vorticity (MRV) at intermediate depths in the JES CB showed one that the spectrum of its interannual variability is formed mainly by oscillations of periods ～2, ～4 and ～5 years, and in the decadal range with ～10 and ～14 years. Along the depth, the spectral composition of MRV variability does not change, but there is a noticeable weakening of decadal variability amplitude, which does not occur with the 4- and 5-year oscillations. Using SVD-analysis, the connection is established between MRV variability, wind stress curl (WSC), as well as sensible heat flux. The strong connection between MRV and WSC is revealed in the range of 4–5 years, and in the decadal range (period is 10 years) the significant connection is with both WSC and air-sea temperature as a result of winter cooling and following deep convection.     

Influence of the interaction between the Atlantic and the Arctic Ocean on the Gulf Stream

Numerical experiments with the circulation model of the North Atlantic based on the splitting algorithms in the σ-coordinate system with a spatial resolution allowing for reproducing synoptic eddies were performed in two versions: with the Arctic Ocean and without it (boundary along 78°N). They showed that the account for the water exchange with the Arctic is fundamentally important for reproducing jet dynamics at the western boundary of the Atlantic down to the subtropical zone. The influence of the conditions at the liquid boundary that separates the Atlantic and the Arctic extends not only over the subarctic area [29] but is also “transferred” by the Labrador Current and the Slope Water Current (SWC) to the area of the Gulf Stream proper. One cannot properly describe the detachment of the Gulf Stream from the coast without adequate reproducing of the Labrador Current and SWC. An hypothesis is posed that the location of the detachment region at 35°N is caused by strong vertical motions at the interface between the SWC and the Gulf Stream jet with horizontal velocities that are almost equal to those at the exit from the Florida Strait. A comparison of the model circulation with that retrieved from the hydrological data and the drift of neutral buoyancy floats [14, 22] showed both qualitative and quantitative coincidences of the features of the northward warm water transfer such as the streamline around the so-called northwestern “corner” (motion “along the topography”) and the jet-wise transport of these waters from Labrador to the northeast inside a kind of “pipeline,” which is limited in the upper baroclinic layer 1 km thick by mean velocity contour lines of about 10 cm/s. A comparison between the experimental [19] and model fields of the ocean level showed that, at the absence of direct representation of the water (mass) exchange between the Atlantic and the Arctic Ocean, the decrease of the gradient velocities in the Gulf Stream may reach 30%.     

Splitting Numerical Technique with Application to the High Resolution Simulation of the Indian Ocean Circulation

The aim of this paper is twofold : To present an efficient numerical technique for the simulation of the ocean general circulation (OGC) and to apply it to the simulation of the Indian Ocean dynamics with high spatial resolution. To solve model equations we use the splitting method by physical processes and space coordinates. We select the main parts of the model operator and then perform their numerical treatment independently of one another. We describe the general methodology and some special aspects of this approach. Numerical treatment of the monsoon circulation is performed on the basis of the sigma-coordinate primitive equation model, which was developed at the Institute of Numerical Mathematics (Moscow, Russia). We present and briefly analyze the results of the numerical experiment with high spatial resolution 1/8° along latitude, 1/12° along longitude, and with 21 vertical sigma levels.The work was supported by the Russian Foundation for the Basic Research (03-05-64354, 02-05-64909) and by the Russian Academy of Sciences (10002-251/OMN-03/026-020/240603-807)     

Modeling the seasonal variability of marine ecosystem in the region of the Central-Eastern Atlantic

A 3D eco-hydrodynamical model of high resolution (0.25° × 0.25°, 27 σ-levels) is used to simulate the seasonal variability of the ocean circulation and marine ecosystem in the Central-Eastern Basin of the North Atlantic including the Canary upwelling system. According to the model results, in the winter period, the “patches” of maximal phytoplankton and zooplankton biomass are often located in upwelling zones in the open ocean on the periphery of cyclonic eddies rather than in the coastal upwelling zones. In the summer period, when the phytoplankton biomass reaches maximal (in the annual cycle) values, the maxima of the phytoplankton are located in the coastal upwelling zones. As shown, there is no simple relationship between the nitrate distributions, on the one hand, and the phytoplankton and zooplankton ones, on the other hand.     

New model and field data on estimates of Antarctic Bottom Water flow through the deep Vema Channel

We used a numerical model of the ocean circulation with a high spatial resolution to obtain estimates of the kinematic characteristics of Antarctic Bottom Water flow through the abyssal Vema Channel in the southwestern part of the Atlantic Ocean. The results of simulations correspond to the data of direct velocity measurements made at several locations in the channel. The high horizontal and vertical resolution of the model in the bottom layer allowed us to study in detail the hydrodynamics of this flow over its entire length.     

Thermohaline Structure of Waters in the North Atlantic in Different Phases of the Atlantic Multidecadal Oscillation

Izvestiya, Atmospheric and Oceanic Physics - The meridional structure of climatic trends and anomalies of potential temperature and salinity in the North Atlantic waters in different periods of the...     

High resolution modeling of the monsoon circulation in the Indian Ocean

The goal of this paper is to present some results on the monsoon circulation in the Indian Ocean simulated with a σ-coordinate ocean model developed at the Institute of Numerical Mathematics, RAS. The model has a horizontal resolution of (1/8)° × (1/12)° and contains 21 σ-layers of uneven thickness. Realistic bottom topography and land geometry are used. The numerical experiments were carried out for 15 years starting from the Levitus climatology for January and monthly mean climatic atmospheric forcing from the NCEP reanalysis data. The annual cycle of the surface and subsurface currents and temperature and salinity fields were analyzed. The model reproduces well the Summer Monsoon and the Winter Monsoon currents and their time evolution and spatial structures. The Somali Current is adequately modeled. During the Summer Monsoon, the velocities of the current exceed 2 m/s, while the total mass transport is approximately 70 Sv. The model results show that a reversal of the Somali Current from the northern direction in the summer to the southern direction in the winter is accompanied by the generation of anticyclonic eddies, which drift westward owing to the β-effect and dissipate either near the Somali shore or in the Gulf of Aden. The monsoon variability of the equatorial surface current and equatorial subsurface countercurrent system are analyzed. It is shown that these currents are generated predominantly by the zonal component of wind stress, in which the half-year harmonic dominates. This leads to the fact that the equatorial surface current also changes its direction with a half-year periodicity almost in phase with the wind. The oppositely directed subsurface compensational countercurrent changes its direction with a time lag of approximately one month. Gradient currents, which appear in the Bay of Bengal due to the riverine runoff, make an important contribution to the circulation. This effect manifests itself especially strongly in the summer during the peak of the Ganges River runoff, which transports fresh turbid waters. The principal features of the large-scale quasi-stationary gyre structure of the Indian Ocean such as the Great Whirl, Socotra high, and Laccadive high and low are simulated.     

Simulation of Extreme Surges in the Taganrog Bay with Atmosphere and Ocean Circulation Models

The simulation the most extreme surges over the period of instrumental observations in the Taganrog Bay since 1881, the surges occurred on March 24, 2013 and September 24, 2014. The objective of the simulation is to study surge formation features and to reveal requirements for the accuracy of simulating atmospheric and oceanic circulation in the Sea of Azov. For this purpose, the Institute of Numerical Mathematics Ocean Model (INMOM) with the spatial resolution of ~4 km and ~250 m was used. The atmospheric forcing over the Black Sea region was specified using ERA-Interim reanalysis data and WRF model data with the spatial resolution of 80 and 10 km, respectively. It is shown that the quality of simulation of extreme surges in the Sea of Azov is more dependent on the quality of the input atmospheric forcing than on the spatial resolution of the ocean circulation model. The usage of WRF data as atmospheric forcing allows the more accurate simulation of extreme surges. However, the simulation of the extreme surge of 2014 overestimates, and simulations for the 2013 surge underestimate the surge level. Evidently, as the used version of INMOM does not take into account the coastal zone flooding, the maximum surge value is overestimated.     

Simulations of currents and pollution transport in the coastal waters of Big Sochi

We suggested a method for modelling the transport of pollutants over the Black Sea water basin adjacent to Big Sochi. The model is based on the application of the Institute of Numerical Mathematics Ocean Model (INMOM) over the entire basin of Big Sochi in two versions: M1 and M2. In the first version, we use uniform spatial resolution of the model with a step of ～4 km; in the M2 version, the resolution is not uniform. The step decreases to 50 m in the basin of Big Sochi. The M2 version is used only in the periods when pollution transport is simulated, for which the initial hydrothermodynamic state is specified from the M1 version. Both versions reflect a complex character of Black Sea circulation; however, the M2 version more adequately reproduces the eddy circulation in its eastern part, where the horizontal resolution of the M2 version is higher. A conclusion is made on this basis that, in order to reproduce the eddy structure of the Black Sea circulation, the resolution of the model should be on the order of 1.5 km and the main factor of the formation of the quasi-stationary Batumi anticyclonic eddy is the topographic peculiarities in this part of the sea. The pollution spreading from the Sochi, Khosta, and Mzymta rivers and from 18 pipes of deep-water sewage was simulated for the flood periods from April 1, 2007, to April 30, 2007. It was shown that mesoscale eddy formations that form a complex three-dimensional structure of pollution spreading make the greatest contribution to the spread of pollution.