Climate prediction: Progress,problems, and prospects

“Hundred year forecasts are made with the same models, which cannot predict the weather even several days ahead...”     

A quasi-static nucleation model. 1. Homogeneous nucleation

A homogeneous nucleation model is considered. It is based on the idea that in the parent phase, a quasi-static distribution is formed of the new phase nuclei as an effect of mechanisms of their generation and destruction. An estimate is presented of quantity and of generation rate for viable nuclei in supersaturated vapor and supercooled water. The calculation results are compared against earlier experimental data obtained by different authors.     

Influence of Changes in the Prevailing Synoptic Conditions on the Response of Aerosol Characteristics to Land- and Sea-Breeze Circulations at a Coastal Station

The changes in the response of near surfaceaerosol properties to land- and sea-breezecirculations, associated with the changes in the prevailing synoptic meteorological conditions, are examined for a tropical coastal station. Aerosol properties are nearly similar in both the breeze regimes (land and sea) during seasons of marine airmass while they are distinct during seasons of continental airmass. As the prevailing winds shift from continental to marine and the ambient weather changes from winter conditions to the humid monsoon season, the submicron mode, which dominated the aerosol mass-size distribution, is largely suppressed and the dominance of the super micron mode increases. During periods of continental air mass (winter), the aerosol loading is significantly higher in the land-breeze regime, (particularly in the submicron range) but as the winds shift to marine, the loading initially becomes insensitive to the breeze regimes and later becomes higher in the sea-breeze regime, particularly in the super micron range.     

An optimization scheme of instrumental soil water storage determination

An optimization scheme is considered of the method of instrumental determination of soil moisture used within the Roshydromet system. The scheme enables to reduce the volume of instrumental operations by 2.5–3 times using the empirical statistical dependences between the water content in different layers of the soil profile. Efficiency of the filtration of outliers in the data sample is studied on the basis of the analysis of regression residuals when deriving the regression equations.     

The influence of momentum advection on the Baltic Sea dynamics

Contribution of momentum advection to the formation of the low frequency fields of the Baltic Sea levels and currents is estimated using numerical experiments with a hydrodynamic model and statistical analysis of the experimental results. It is found that momentum advection has a significant influence on the formation of the mean level and its seasonal and synoptic variability in Neva Bay of the Gulf of Finland. The results show that nonlinear effects associated with advective accelerations can essentially contribute to the Neva River flood formation.     

Winter climatology of upper-level frontal zones in the Northern Hemisphere

Average long-term fields of geopotential gradients in the middle and upper troposphere and temperature gradients and geopotential Laplacian in the middle troposphere in the Northern Hemisphere in winter are analyzed. Based on the analysis of the distribution of the maximum values of gradients, the average long-term position of upper-level frontal zones and their axial lines was determined. Their spatial distribution is analyzed from the point of view of interaction between thermobaric fields over different regions of the globe. Average long-term parameters of upper-level frontal zones in the middle troposphere are presented. Average long-term fields of wind speed in the middle and upper troposphere are investigated. It is demonstrated that the zones of the maximum values of wind speed agree well with the position of separated upper-level frontal zones.     

SL-AV atmospheric model version using σ-<Emphasis Type="Italic">p</Emphasis> hybrid vertical coordinates

The SL-AV atmospheric model version using hybrid vertical coordinates combies the advantages of sigma and isobaric coordinates. The formulation and discretization of model equations maintain the equivalency of the new model version to the basic sigma version in the special case, when hybrid coordinates coincide with sigma coordinates. The SL-AV model version with hybrid vertical coordinate is verified with medium-range weather forecasts. The decrease in the errors of predicted geopotential height and wind as compared to the sigma model version is demonstrated. The use of hybrid coordinates also leads to a certain increase in forecast skill scores for some meteorological parameters characterizing aviation significant weather.     

Are Urban-Canopy Velocity Profiles Exponential?

Using analyses of data from extant direct numerical simulations and large-eddy simulations of boundary-layer and channel flows over and within urban-type canopies, sectional drag forces, Reynolds and dispersive shear stresses are examined for a range of roughness densities. Using the spatially-averaged mean velocity profiles these quantities allow deduction of the canopy mixing length and sectional drag coefficient. It is shown that the common assumptions about the behaviour of these quantities, needed to produce an analytical model for the canopy velocity profile, are usually invalid, in contrast to what is found in typical vegetative (e.g. forest) canopies. The consequence is that an exponential shape of the spatially-averaged mean velocity profile within the canopy cannot normally be expected, as indeed the data demonstrate. Nonetheless, recent canopy models that allow prediction of the roughness length appropriate for the inertial layer’s logarithmic profile above the canopy do not seem to depend crucially on their (invalid) assumption of an exponential profile within the canopy.     

Anthropogenic climate change over the Mediterranean region simulated by a global variable resolution model

Two 30-year simulations corresponding to 1960-1989 and 2070-2099 have been performed with a variable resolution atmospheric model. The model has a maximum horizontal resolution of 0.5° over the Mediterranean Sea. Simulations are driven by IPCC-B2 scenario radiative forcing. Sea surface temperatures (SSTs) are prescribed from monthly observations for the present climate simulation, and from a blend of observations and coupled simulations for the scenario. Another pair of forced atmospheric simulations has been run under these forcings with the same uniform low resolution as the coupled model. Comparisons with observations show that the variable resolution model realistically reproduces the main climate characteristics of the Mediterranean region. At a global scale, changes in latitudinal temperature profiles are similar for the forced and coupled models, justifying the time-slice approach. The 2 m temperature and precipitation responses predict a warming and drying of the Mediterranean region. A comparison with the coupled simulation and forced low-resolution simulation shows that this pattern is robust. The decrease in mean precipitation is associated with a significant decrease in soil wetness, and could involve considerable impact on water resources around the Mediterranean basin.