Abstract. The Tropical Ocean-Global Atmosphere (TOGA) program sought to determine the predictability of the coupled ocean-atmosphere system. The World Climate Research Programme's (WCRP) Global Ocean-Atmosphere-Land System (GOALS) program seeks to explore predictability of the global climate system through investigation of the major planetary heat sources and sinks, and interactions between them. The Asian-Australian monsoon system, which undergoes aperiodic and high amplitude variations on intraseasonal, annual, biennial and interannual timescales is a major focus of GOALS. Empirical seasonal forecasts of the monsoon have been made with moderate success for over 100 years. More recent modeling efforts have not been successful. Even simulation of the mean structure of the Asian monsoon has proven elusive and the observed ENSO-monsoon relationships has been difficult to replicate. Divergence in simulation skill occurs between integrations by different models or between members of ensembles of the same model. This degree of spread is surprising given the relative success of empirical forecast techniques. Two possible explanations are presented: difficulty in modeling the monsoon regions and nonlinear error growth due to regional hydrodynamical instabilities. It is argued that the reconciliation of these explanations is imperative for prediction of the monsoon to be improved. To this end, a thorough description of observed monsoon variability and the physical processes that are thought to be important is presented. Prospects of improving prediction and some strategies that may help achieve improvement are discussed. IntroductionThe annual cycle of the monsoon systems has led the inhabitants of monsoon regions to divide their lives, customs, and economies into two distinct phases: the "wet" and the "dry." The wet phase refers to the rainy season during which warm, moist, and very disturbed winds blow inland from the warm tropical oceans. The dry phase refers to the other half of the year when winds bring cool and dry air from the winter continents. This distinct variation of the annual cycle occurs over Asia, Australia, west Africa, and in the Americas. In some locations (e.g., in the Asia-Australia sector) the dry winter air flows across the equa- Agricultural practices have traditionally been tied strictly to the annual cycle. Whereas the regularity of the warm and moist and cool and dry phases of the monsoon would seem to be ideal for agricultural societies, their very regularity makes agriculture susceptible to small changes in the annual cycle. Small variations in the timing and quantity of rainfall have the potential for significant societal consequences. A weak monsoon year (i.e., significantly less total rainfall than normal) generally corresponds to low crop yields. A strong monsoon usually produces abundant crops, although too much rainfall may produce devastating floods. In addition to the importance of the strength of the overall monsoon in a particular year, forecasting the onset of the subseasonal vari...

The bulk properties of tropical cloud clusters, such as the vertical mass flux, the excess temperature, and, moisture and the liquid water content of the clouds, are determined from a combination of 1) the observed large-scale heat and moisture budqets overan are covering the cloud cluster, and 2) a model of a cumulus .ensemble which exchanges mass hecat, water vap o r an&d'liquid water with the environment through entrainnfent and detrainment. The method also !rovid6s ' understanding of how the environmental air is heated and moistened by the cumulus convection. An' estimat6 of the average cloudi cluster properties and the :heat and moisture balance of the environment, obtained from 1956 Marshall Islands data, is presented. (NASA-CR-132871) DETERMINATION OF BULK N74-12151 PROPERTIES OF TROPICAL CLOUD CLUSTERS FROM .LARGE SCALE HEAT AND MOISTURE BUDGETS, APPENDIX B (California Univ.) Uncl 33 p HC $

Using the objectively analyzed FGGE II-b upper-air data, the large-scale circulation, heat sources and moisture sinks over the Tibetan Plateau and surrounding areas are examined for a 9-month period from December 1978 to August 1979. In addition to the FGGE data, special soundings obtained during the Chinese Qinghai-Xizang (Tibet) Plateau Meteorological Experiment (QXPMEX) from May to August 1979 are also used in the objective analyses.The evolution of the large-scale flow patterns, temperature, outgoing longwave radiation (OLR) and vertical circulation is described in order to identify the distinct seasonal changes from winter to summer that lead to the onset of the Asian summer monsoon. The Tibetan Plateau maintains a large-scale thermally driven vertical circulation which is originally separated from the planetary-scale monsoon system. The rising motion exists only on the western Plateau in winter and then spreads to the whole Plateau as the season progresses. The monsoon onset over Asia is an interaction process between the Plateau-induced circulation and the circulation associated with the principal rainbelt migrating northward.

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