Variations in the Global Water Budget

R.E. Newell President, International Commission on Climate International Association of Meteorology and Atmospheric Physics Water is the active ingredient in the global climatic system, its physical properties ensuring that it plays a major role. Its high thermal capacity provides a mechanism for moderating mid­ latitude winter temperatures; solar energy is absorbed by the surface layers of the middle latitude oceans in summer and is released to the atmosphere in winter as the ocean cools. The variation of saturation vapour pressure with temperature is the factor which causes oceanic surface temperatures at low latitudes to be limited by evaporation to values near 29°C, thereby limiting tropical marine air temperatures to about the same value. The substantial amount of energy involved in phase changes - the latent heat - governs the passage of solar energy to the atmo­ sphere; visible solar radiation is absorbed at the Earth's surface, energy is supplied to evaporate water and the latent heat is released to the atmosphere when and where condensation occurs, which is often a considerable distance from the source of the moisture. The infrared radiative characteristics of water vapour, namely the broad vibration-rotation bands typical of a triatomic molecule, permit it to act as the principal agent of energy loss from the atmosphere, throu?,h infrared radiation to space.

Contenu

TECHNIQUES OF MEASUREMENT AND ANALYSIS: I, ATMOSPHERIC PROCESSES.- The atmospheric branch of the hydrological cycle and climate.- The atmospheric water vapour budget over Europe.- Remote sensing of atmospheric water content from satellites.- Comparison of water vapour data from Monex-79 and the Tiros-N satellite.- Atmospheric water distributions determined by the Seasat multi-channel microwave radiometer.- Variations of deuterium and oxygen-18 in continental precipitation and groundwater, and their causes.- TECHNIQUES OF MEASUREMENT AND ANALYSIS: II. SURFACE PROCESSES.- Monthly and areal patterns of mean global precipitation.- Comparison of rainfall rates derived from radar and Nimbus 5 microwave observations in the tropical Atlantic.- Evaporation models in the global water budget.- The use of long-term river level and discharge records in the study of climatic variations in the Federal Republic of Germany.- Plant and soil water storage in Arctic and boreal forest ecosystems.- Recent fluctuations of Alpine glaciers and their meteorological causes 1880-1980.- Radiometric chronology of some Himalayan glaciers.- SECULAR VARIABILITY: INTERACTIONS AND TELECONNECTIONS.- Recent rainfall fluctuations in Africa - Inter-hemispheric teleconnections.- Droughts and floods over India in summer monsoon seasons 1871-1980.- The heavy rainfall in China in 1980 and a comparison with earlier extremes.- Variability of rainfall over northern Australia.- Moisture variations associated with El Nino events.- Surges of tropical Pacific rainfall and tele-connections with extratropical circulation patterns.- Antarctic sea ice variations 1973-1980.- LONG-TERM CHANGES.- Late-glacial circulation over central North America revealed by aeolian features.- Fluctuations in closed-basin lakes as an indicator of post atmospheric circulation patterns.- Present-day and early-Holocene evaporation of Lake Chad.- Marine shorelines in estuaries as palaeoprecipi-tation indicators.- Monsoon rains of the late Pleistocene and early Holocene Patterns, intensity and possible causes of changes.- Sea-level control of ice sheet disintegration.- A climate feedback mechanism involving oceanic upwelling, atmospheric CO2 and water vapour.- Illusions and problems in water-budget synthesis.- MODELLING AND PREDICTION.- The hydrological cycle as simulated by an atmospheric general circulation model.- Effects of soil moisture anomalies over Europe in summer.- Some simulation model results of the effect of vegetation change on the near-surface hydro-climate.- The concept of runoff in the global water budget.