G. S. Golitsyn

Probability distributions for cyclones and anticyclones from the NCEP/NCAR reanalysis data and the INM RAS climate model

Analysis of statistical characteristics of cyclones and anticyclones in the latitudinal belt between 20° and 80°N has been performed with the NCEP/NCAR reanalysis data and simulations with the general circulation climate model of the Institute of Numerical Mathematics of the Russian Academy of Sciences (INM RAS GCCM). The model results have been analyzed for the second half of the 20th century against the NCEP/NCAR reanalysis data and for the 21st century with the SRES-A2 anthropogenic scenario. Overall for the 20th century, no statistically significant changes in the number of cyclones and anticyclones are obtained from either the NCEP/NCAR reanalysis data [1] or from simulations with the INM RAS GCCM [2]. It is found that the total number of cyclones and anticyclones decreased in the 20th century as compared to the 21st century. It is shown that cumulative distributions of the number of cyclones and anticyclones by their intensities and areas have an exponential form from both the reanalysis data and the model simulations, although the corresponding exponents are different.

Polar lows and tropical hurricanes: Their energy and sizes and a quantitative criterion for their generation

Similarity and dimension considerations applied to convection in a rotating fluid allows one to estimate the sizes and horizontal velocities of generated vortices. To do this, it is necessary to know the buoyancy flux in the fluid and the angular velocity of fluid rotation [1, 2]. The author’s preliminary efforts [3] have shown that the sizes, wind speeds, and total kinetic energy can thus be estimated correctly for tropical cyclones (TCs), as well as for polar lows (PLs) (which are often called explosive mesocyclones because they take just a few hours to develop). In this study, the sensible and latent heat fluxes for U = 33 m/s and the related buoyancy fluxes are estimated on the basis of climatology, bulk formulas, and the velocity scale of convection in a rotating fluid. In the tropics, at hurricane wind speeds U ≥ 33 m/s and climatological air humidity r = 80%, the total heat flux at the water surface temperature Ts ≥ 26°C becomes equal to or greater than 700 W/m2. Due to the Clausius-Clapeyron equation, the latent heat flux to the atmosphere (the main part of the flux in the tropics) decreases substantially at lower values of Ts. Thus, an energy flux from the ocean to the atmosphere of 700 W/m2 or greater should be regarded as the first necessary condition for TC genesis instead of the temperature Ts. Low static stability, which must be at least half its climatological value as estimated here, is another necessary condition [4]. In polar regions, total fluxes roughly twice those in the tropics are needed for the formation of explosive mesocyclones, PLs, which is explained by the much smaller role of latent heat, greater geostrophicity, and stronger static stability of the atmosphere there. Enthalpy fluxes and wind speeds are interrelated: the larger the flux is, the stronger the convection, the higher the concentration of angular momentum in an ascending convective air column, and the greater the azimuthal velocity in the vortex are, which in turn enhances the transfer of energy from the ocean. Considering the problem with the use of simple analytic relations makes it possible, for the first time, to find a numerical criterion for their generation. It is hoped that this material may be useful for educational purposes as well.

The energy cycle of wind waves on the sea surface

The problems of wind-induced waves on the sea surface are considered. To this end, the empirical fetch laws that determine variations in the basic periods and heights of waves in relation to their fetch are used. The relation between the fetch and the physical time is found, as are the dependences of the basic characteristics of waves on the time of wind forcing. It is found that about 5% of wind energy dissipated in the near-water air layer contributes to the growth of wave heights, i.e. wave energy, although this quantity depends on the age of waves and the exponent in the fetch laws. With consideration for estimates of the probability distribution functions for the wind over the world ocean [11], it is found that the rate of wind-energy dissipation in the near-water air layer is on the order of 1 W/m2. The calculations of wind waves [19] for the world ocean for 2007 have made it possible to assess the mean characteristics of the cycle of wave development and their seasonal variations. An analysis of these calculations [19] shows that about 20% of wind energy is transferred to the water surface. The remaining amount (80%) of wind energy is spent on the generation of turbulence in the near-water air layer. About 2%, i.e., one tenth of the energy transferred to water, is spent on turbulence generation due to the instability of the vertical velocity profile of the Stokes drift current and on energy dissipation in the surf zones. Of the remaining 18%, 5% is spent directly on wave growth and 13% is spent on the generation of turbulence during wave breaking and on a small-scale spectral region. These annually and globally mean estimates have a seasonal cycle with an amplitude on the order of 20% in absolute values but with a smaller amplitude in relative values. According to [19] and to the results of this study, the annually mean height of waves is estimated as 2.7 m and their age is estimated as 1.17.

Studying the pollution of Moscow and Beijing atmospheres with carbon monoxide and aerosol

The measurements of submicron aerosol and black carbon (BC) surface concentrations, and carbon monoxide (CO) total column in 1992–2012 in Beijing and Moscow are illustrated. The specific features in the long-term variations in the studied impurities in these megacities are discussed. The level of pollution with all three impurities in Beijing is substantially higher than in Moscow. From 1992 to 1999, the monthly means of black carbon and aerosol increased in Beijing. These concentrations substantially decreased beginning from 2000. From 2007 to 2011, black carbon decreased and submicron aerosol increased. In 1996–2003 the urban part of CO total column (TC) in Beijing was on average higher than in 2006–2012 by a factor of 1.4. The anthropogenic part of CO in Moscow decreased in 2006–2012. High aerosol and CO concentrations, comparable with concentrations rather typical of Beijing, were observed in Moscow only during wildfires in 2010. Using the cluster analysis statistical methods, it has been indicated that the main sources of the air pollution in Beijing are located 100–500 km southward.

On the nature of spiral eddies on the surface of seas and oceans

350 The emergence of satellite imagery of the Earth’s surface was a great breakthrough for our planet, mak ing it possible to reveal some of its features and phe nomena that had been completely unknown until that time. One example was the finding of spiral eddies on the surface of seas and oceans around 10 km in size (from several kilometers up to 20 km), which were dif ferent from the Gulf Stream and Kurosio rings (between 200 and 300 km in size). The first compre hensive description of spiral eddies was initiated in 2000 by Walter Munk [1], which included a history of their visual observations from space and an attempt to theoretically describe them as a result of shear flow instabilities.

Coefficient of horizontal eddy diffusion of a tracer on the water surface as a function of the wave age

A relationship between the statistical parameters of horizontal diffusion and the parameters of the energy-containing part of the frequency spectrum of sea-surface elevations is found depending on the wave age Ω and the ratio between the wind speed at 10 m and the phase velocity of the peak of a wave. It has been observed in [1–7] that the diffusion coefficient K(r) of a patch of size r increases as rβ, where 1.15 < β < 4/3, and the patch area S(t) increases with time as tγ, where 2 < γ < 3. As was calculated in [15], in the energy-containing part of the elevation frequency spectrum, S(ω) ∼ ω−n, where n = 13/3 for young waves with Ω > 2, n = 4 for waves with 1.2 < ψ < 2, and n = 11/3 for developed waves with 0.83 < Ω < 1.2. It is found that β = (n + 1)/4 and γ = 8/(7 − n). These relations explain the entire set of observed exponents: β = 4/3 and γ = 3 for young waves and β = 1.15 and γ = 2.34 for large sizes (up to 1000 km) and times (up to a month) when it is found here that β = 7/6 and γ = 2.4.

Effect of viscosity on admixture horizontal diffusion in the wind-wave field

In the problem of admixture diffusion on the sea surface in the presence of wind waves, it has been indicated that the flow potential character is disturbed when viscosity in the wind-wave velocity field is taken into account. Modeling indicates that this allows a liquid particle to pass from one wave into another wave, as a result of which diffusion is maintained on the water surface. A distance between adjacent liquid particles increases in time, which is also evidence of diffusion. Observational data coincide with calculations if viscosity about turbulent, i.e., several cm2 s−1, is introduced. The study was performed because liquid particles do not go beyond a wave (i.e., diffusion is formally impossible) in the classical potential theory of sea waves.

Development of a Subcloud Layer over the Sea during a Cold Air Invasion

Evaporation and vertical moisture and heat transfer from the underlying surface are the basis of cloud formation. The situation when the coming relatively cold stably stratified air moves over a warm ocean is a typical problem in the development of a turbulent convective layer. The problem of cloud formation is also of scientific and practical interest. This paper considers the problems of the formation of a turbulent convective layer over a warmer ocean and the vertical distribution of relative humidity. The results of the theoretical model are compared with the data of observations of the development of the turbulent convective layer at low latitudes (in the Indian Ocean) and at higher latitudes (in autumn over Lake Michigan). Approximate equations describe well the dynamics of temperature and humidity of the layer as a function of the difference between the temperatures of the approaching and near-surface air layers. The theoretical results are compared with the data on measurements of the condensation heights obtained at the Novosibirsk Tolmachevo Airport. Some discrepancy between them is due to the unsteadiness measurement and the approximations adopted in the theoretical model.

Long-Term Trends of Carbon Monoxide Total Columnar Amount in Urban Areas and Background Regions: Ground- and Satellite-based Spectroscopic Measurements

A comparative study was carried out to explore carbon monoxide total columnar amount (CO TC) in background and polluted atmosphere, including the stations of ZSS (Zvenigorod), ZOTTO (Central Siberia), Peterhof, Beijing, and Moscow, during 1998–2014, on the basis of ground- and satellite-based spectroscopic measurements. Interannual variations of CO TC in different regions of Eurasia were obtained from ground-based spectroscopic observations, combined with satellite data from the sensors MOPITT (2001–14), AIRS (2003–14), and IASI MetOp-A (2010–13). A decreasing trend in CO TC (1998–2014) was found at the urban site of Beijing, where CO TC decreased by 1.14%±0.87% yr−1. Meanwhile, at the Moscow site, CO TC decreased remarkably by 3.73%±0.39% yr−1. In the background regions (ZSS, ZOTTO, Peterhof), the reduction was 0.9%–1.7% yr−1 during the same period. Based on the AIRSv6 satellite data for the period 2003–14, a slight decrease (0.4%–0.6% yr−1) of CO TC was detected over the midlatitudes of Eurasia, while a reduction of 0.9%–1.2% yr−1 was found in Southeast Asia. The degree of correlation between the CO TC derived from satellite products (MOPITTv6 Joint, AIRSv6 and IASI MetOp-A) and ground-based measurements was calculated, revealing significant correlation in unpolluted regions. While in polluted areas, IASI MetOp-A and AIRSv6 data underestimated CO TC by a factor of 1.5–2.8. On average, the correlation coefficient between ground- and satellite-based data increased significantly for cases with PBL heights greater than 500 m.摘要基于1998-2014年期间地基和卫星高光谱辐射测量数据对污染和背景地区的CO总量进行了综合比较研究, 包括了莫斯科郊区ZSS (Zvenigorod)站, 西伯利亚中部ZOTTO站, 圣彼得堡Peterhof站, 北京和莫斯科观测站所代表的附近地区. 利用较长时期的地基高光谱观测结合卫星高光谱观测数据获得了欧亚大陆不同地区的CO柱总量的年际变化特征. 采用的卫星数据有MOPITT (2001–2014), AIRS (2003–2014)和IASI MetOp-A (2010–2013). 观测数据分析表明, 北京都市区的CO柱总量(1998-2014)呈现下降趋势, 年均速率为1.14% ± 0.87%, 而莫斯科地区下降幅度很大, 达到年均3.73% ± 0.39%. 在作为大都市参照的乡村背景地区(如ZSS, ZOTTO, Peterhof), 同期CO柱总量下降趋势为年均0.9%–1.7%. 基于2003-2014年间的AIRSv6卫星数据产品分析发现, 欧亚大陆中纬度地区CO柱总量有小幅度下降, 只有0.4%–0.6% 每年, 而东南亚地区下降幅度较大, 达到0.9%–1.2%每年. 从卫星数据(MOPITTv6, AIRSv6和IASI MetOp-A)的相关性分析看出, 洁净地区的相关性较高, 而对于污染地区, IASI MetOp-A 和AIRSv6 数据严重低估了CO柱总量, 达到1.5–2.8倍. 当大气边界层高度大于500米时, 地基和卫星观测数据的相关系数总体上显著增大.

Numerical estimates of mechanical energy transfer from the atmosphere to the Indian ocean

The field of mechanical energy transfer from the atmosphere to the ocean is computed for the first time. The numerical simulation of waves within the Indian Ocean (IO) water area for the period of 1998–2009 is used. Mechanical energy transfer is described by two integrated parameters calculated per area unit: the speed of complete energy flux from wind to waves, IE(x, t), and the speed of complete losses in the energy of wind waves, DE(x, t). In order to solve this problem, the wind field W(x, t) (the NCEP/NOAA data) is used; the IE(x, t) and DE(x, t) fields are calculated on the basis of the WAM numerical model containing a modified source function. The results obtained allow us, first, to assess the characteristic spatial distribution of zones “pumped” by the wind with mechanical energy for both the wave field and the upper layer of the ocean by seasons, years, and the whole period discussed, second, to determine the extreme and average zonal values of IE(x, t) and DE(x, t), the degree of their shift spacing and balance BE = (IE + DE); and third, to define the characteristic time scales of variations in the wind field and wave field energies, caused by energy transfer from the wind to waves in the zones and within the Indian ocean as a whole. These results significantly specify the climatic estimates obtained earlier.