synoptic meteorology

the branch of meteorology that studies the atmospheric processes determining weather conditions and changes in such conditions in order to develop methods of weather forecasting. Synoptic meteorology investigates atmospheric processes that unfold over vast areas and are of sufficiently large scale as to be regarded as links in the general atmospheric circulation (circulation systems). The studies of such processes are backed by the physical laws governing the changes of the air properties and air motion. Latitude is taken into account here, since it determines the amount of incoming solar energy. Consideration is also given to the character and properties of the underlying surface. Land and sea have different effects on weather processes; the nature of the relief is also an important factor in such processes.

Heat, moisture, and various types of impurities are continuously exchanged between the underlying surface and the atmosphere. Tropospheric air masses with different properties form over different regions of the earth’s surface under the influence of heat exchange with the surface. Under certain conditions, the transition zones between these air masses become sharp boundaries called fronts. Atmospheric waves hundreds or thousands of kilometers long arise at these fronts (seeWAVES IN THE ATMOSPHERE) and subsequently develop into cyclones and anticyclones—vortices with decreased and increased atmospheric pressure, respectively. The appearance, development, and motion of cyclones and anticyclones mark changes in the distribution of air masses, indicate the transformation of air masses, and, consequently, determine the movement and evolution of fronts. When cyclones, anticyclones, air masses, and fronts move, the associated cloud and precipitation regions move with them, and local changes occur in the wind, air temperature, humidity, and other properties of the atmosphere.

Since cyclonic and anticyclonic activity determines the continuous changes in the general atmospheric circulation and in the distribution of the weather, the successful prediction of such activity makes possible weather forecasting, at least for periods of up to several days. The study of the sequential alternation of the types of general atmospheric circulation also underlies most present-day attempts to solve the problem of long-range weather prediction. Synoptic meteorology makes use of synoptic weather charts, or weather maps, to carry out a synchronous spatial analysis of the development of atmospheric processes and the associated weather conditions. Commonly used are surface charts, which are based on observations at the earth’s surface, and upper-air charts, which are made for various levels of the atmosphere and are based on surfaces of constant pressure. Constant-pressure charts are used to gain an idea of the state of the atmosphere at different heights—particularly the distribution of pressure, temperature, humidity, and wind. Weather maps permit establishment of the structure, evolution, and movement of air masses, fronts, cyclones, anticyclones, jet streams, and other formations.

In addition to weather maps, synoptic analysis uses such material as cloud photographs taken from meteorological satellites and data from observations made of clouds, precipitation, and other weather phenomena by means of weather radars. Weather forecasts are made primarily by numerical methods on the basis of hydrodynamic theory and the patterns identified by study of the empirical material.

History. The first attempts at weather forecasting were based on local signs and were made in ancient times. After the invention of the barometer in the 17th century, efforts were made to forecast the weather from the change in atmospheric pressure at a given point. The first prognostic charts were drawn up by the German scientist H. W. Brandes in 1826. Not until the invention of the telegraph, however, did it become possible to employ the synoptic method on a broad scale and to create a weather service. A stimulus was given to the development of a weather service by the storm that on Feb. 14, 1854, destroyed in Bala-klava Bay many ships of the Anglo-French fleet operating in the Black Sea during the Crimean War of 1853–56. Using the available observational data, the French scientist U. Leverrier tracked the motion of the storm in Europe and came to the conclusion that the storm could have been predicted in time if there had been an exchange of data between the various countries. Meteorological data began arriving by telegraph at the Main Physical Observatory in St. Petersburg in 1856. In 1872 the publication of a daily weather bulletin was begun in Russia under the direction of M. A. Rykachev. The first storm warning for the Baltic Sea was issued on Oct. 10, 1874.

Even before the organization of the first weather service, the German scientist H. W. Dove in 1837 came to the conclusion that weather changes in the temperate latitudes can be explained by the sequential alternation of polar and equatorial air currents. He believed that all atmospheric motions have a vortical character. In the 1860’s the British scientist R. Fitzroy elaborated Dove’s views and proved that alternating currents of polar and tropical air are always present in the atmosphere of the temperate latitudes. He suggested that cyclones arise at the boundaries between such currents. Because of the sparse network of meteorological stations at that time, these views could not be verified and therefore were not developed. For the same reason, research in subsequent years was limited primarily to the study of the characteristics of the pressure field at the earth’s surface.

In the 1920’s a group of Norwegian scientists V. Bjerknes, J. Bjerknes, and T. Bergeron—formulated the concepts of air masses and atmospheric fronts more precisely. The group proposed models of the evolution of cyclones and anticyclones and elaborated the wave theory of cyclogenesis. The Soviet school of synoptic meteorology was established by the work of such scientists as A. I. Asknazii, S. P. Khromov, and A. F. Diubiuk.

The further development of synoptic meteorology was associated with the introduction into synoptic analysis of aerologi-cal observations, which became possible after the invention of the radiosonde. (P. A. Molchanov proposed the first radiosonde design to be put into practice.) In the late 1940’s and early 1950’s the growth of the aerological network and the increasing height to which radiosondes were being sent made possible the introduction of new ideas into synoptic meteorology—in particular, with respect to jet streams. Since the 1950’s intensive work has been carried out on techniques for describing and predicting atmospheric processes through the formulation and numerical solution of equations of dynamic meteorology. The work of the Soviet scientist I. A. Kibel’ and his followers played a seminal role in the development of numerical prediction methods. The foundations of long-range numerical weather prediction were laid by E. N. Blinova. Outside the USSR, important contributions have been made in this area by such scientists as the Swede C. Rossby, the Norwegian R. Fjø fjørtaft, and the Americans Y. Mintz and J. Charney.

A new stage in the development of synoptic meteorology began in the 1960’s. J. Smagorinsky and other scientists of the USA made use of hydrodynamic theory and numerical methods of analysis and prediction of pressure, temperature, and wind fields to consider atmospheric processes in the large, that is, on a planet-wide scale. On the basis of hydrodynamic theory and numerical methods, it became possible to make short-range numerical predictions of the general character of the weather over large areas. As before, in order to make accurate local weather forecasts on the basis of such general forecasts, detailed analysis of synoptic charts must be carried out in the regional weather offices. The international Global Atmospheric Research Program (GARP) is directed toward solving the fundamental problems involved in creating a reliable numerical method for long-range weather forecasts.