INTRODUCTION TO METEOROLOGY BY A. K. DAS, M.Sc. (Cal.), D.Sc. (Paris) Indian Meteorological Service AND B. N. SRIVASTAVA, M.Sc. Department of Physics Allahabad University > Price Rs. 2\- CONTENTS CHAPTER XII METEOROLOGY HISTORICAL AND GENERAL I, SECTION PAGE 1, Introduction 359 2, History of meteorology 360 3, The meteorological elements 363 II. METEOROLOGICAL INSTRUMENTS MEASUREMENT OF TEMPERATURE MEASUREMENT OF PRESSURE 11. Two types of barometers 369 12. Standard Fortin's barometer 369 13 The Kew pattern barometer 370 14. The aneroid barometer 370 15. Barograph 37- 16. Units 372 MEASUREMENT OF WIND 17. Wind 372 18. Wind vane 373 19. Velocity estimations, Beaufort scale 374 ....... 20 Anemometers 375 21. Pressure-plate anemometer.... ... 375 22. Rotation anemometer H75 CONTENTS CONTENTS III SECTION PAGE IV. THE HEATING AND COOLING OK THE ATMOSPHERE. SOLARRADIATION 55 Sources ofenergy ofthe atmosphere 400 56. Distanceofthe sun .... 401 57. Directness and duration of solar radiation 401 58. Variation of insolation with latitude and time . . . 402 59. Absorption by the atmosphere 404 60. Pyrheliometers 405 61. The solarconstant 406 62. Variation of solar constant 407 63 Effective radiation 407 64. Distribution of weatherelements 408 V. DISTRIBUTION OF TEMPERATURE 65. Vertical distribution of temperature , , 408 66. Troposphereand stratosphere 411 67 Physical explanation of the existence of the stratosphere . 412 68. Inversions .... 414 69. Distribution oftemperature over theglobe 414 70. Annual variations 415 71. Isothermal Charts 416 72. Diurnal variation of temperature 419 7B. Variation with latitude 420 74. Influenceof altitudeon diurnal variation of temperature . 420 VI DISTRIBUTION OF PRESSURE 75. Vertical distribution of pressure .... 421 76. Distribution of pressure in the stratosphere 428 77. Convective or adiabatic equilibrium 424 78. Diurnal variation of pressureon the earth's surface . . 426 79. Variation with latitude 426 80. Annual variation of pressure 427 81. Isobaric charts 427 82. Monthly isobaric charts 428 VII. WATERVAPOUR IN THE ATMOSPHERE 83. Distribution of watervapourin the lower atmosphere . . 430 84. Water vapour in the stratosphere .... 432 85. Diurnal and annual variation ofhumidity 432 86. Methods of causing condensation 43B CONTENTS V SECTION PAGE 116. Evolution of a depression 477 117. Theory of General circulation based on polar front theory . 480 118. Anticyclones of temperate zones 481 119. Tropical cyclones 482 120. Energy of cyclones and depressions 488 121. Thunderstorms 488 122. Tornadoes 492 128. Whirlwinds 493 124. Nor'westers of Bengal 493 XII. WEATHER FORECASTING AND WEATHER SERVICE 125. Weather forecasting 494 126. Long-range and short-range forecasts 495 127. Weather service , 496 128. Methods of forecasting 498 APPENDIX 501 INDEXOF CHAP. XII (METEOROLOGY) . 507 CHAPTER XII METEOROLOGY* HISTORICAL AND GENERAL I. 1 Introduction. ' Meteorology ' is a branch of the larger science of Geophysics, or Physics of the earth. It de*ls with the phenomena which take place in the atmosphere surround- ing the earth and has nothing- to do with meteors. It is derived from a Greek word ra jiere'w/x*, meaning *' the things above." The Science of Meteorology is again subdivided into numerous branches each dealing with a particular class of atmospheric phenomena But the two important divisions are Climatology and Dynamical Meteorology. Climatology deals with climate in general, i.e., description of various atmospheric phenomena over the globe, their study, inves- tigation and speculation regarding their origin, as well as their relation to one another, their influence on animal and vegetable life, on public health, and also a proper estimation of the influence of geographical and topographical conditions on these phenomena. Dynamical meteorology consists principally in the study of the general laws of motion of the atmosphere, and the mode of formation and propagation of storms, depressions, etc. Djnamical meteorology also includes "thermodynamics of the atmosphere" which deals with the application of the laws of heat to such topics as formation of clouds, precipitation and study of general weather conditions. These two branches will be chiefly treated in this book. But we have, in addition, other branches such as the following: (i) Meteorological Optics . . . which deals with such pheno- mena as formation of haloes, corona, problems of visibility, etc.; * We are deeply indebted to Mr. S. Basu of the Indian Meteorological Departmentforhiskindly going through the manuscript of this chapter and forhisvaluablecriticisms andsuggestions. 359