The climatology and the basic state of the summertime circulation and rainfall over South America are studied using assimilation products from the data assimilation system of Goddard Earth Observing System-1 (GEOS-1) and satellite-derived rainfall. Results indicate the existence of a regional summer monsoon circulation regime induced by strong diabatic heating over the subtropical South American highland centered at the Altiplano Plateau. Sensitivity of the results to the assimilation scheme is tested by comparing that with the National Centers for Environmental Prediction (NCEP) reanalysis and with satellite rainfall estimates. Results show general agreement between the model produced rainfall anomaly and the satellite estimates, as well as consistency between the basic circulation features in the GEOS-1 and the NCEP reanalyses. A case study of 1989-90 South American summer monsoon (SASM) reveals the following characteristics. 1) In late spring, the onset of SASM is signaled by an abrupt merging of the upper-tropospheric double westerly jets, one in the subtropics and the other in the subpolar region, into a single jet in the midlatitudes. This is followed by the establishment of a vortex to the southeast of Altiplano and occurrence of heavy precipitation over subtropical eastern Brazil. 2) During the mature phase of SASM, the heavy rainfall zone moves over the Altiplano Plateau and the southernmost Brazilian highland. The fully established SASM features are the following: (a) an enhancement of equatorial North Atlantic trade wind, which emanates from the Sahara high and crosses the equator over the South American continent; (b) a buildup of strong northwesterlies along the eastern side of the tropical Andes; and (c) development of the South Atlantic convergence zone in the southernmost position with strong convective activity. Meanwhile, the upper-tropospheric return flow emerges from an anticyclone formed over the Altiplano Plateau, crosses the equator, and sinks over northwestern Africa. 3) The withdrawal of SASM in late summer is signaled by the resplitting of the midlatitude westerly jet. At the same time, the low-level northwest monsoon flow diminishes, reducing the moisture supply and leading to the termination of heavy precipitation over the subtropical highland. Results also show that the above-mentioned characteristics of SASM are clearly linked to the tropospheric temperature changes over the central South American highland. Sensible versus latent heating over the highland are bound to play an important role in the evolution of SASM. To provide further support of presence of a monsoon climate over South America, SASM is compared and contrasted to the ''classic'' east Asian summer monsoon (EASM). Many similar features, including evolution characteristics between the two systems, have been identified. Contrasting aspects of the SASM from the EASM are also discussed. It is pointed out that a number of monsoonal characteristics of the climate of South America, such as the seasonal reversal of the low-leve...

Using the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) product together with the Goddard Earth Observing System (GEOS) reanalysis and the National Center for Environmental Prediction (NCEP) sea-surface temperature (SST) data, we have conducted a diagnostic study of the interannual and decadal scale variability of principal modes of summer rainfall over South America for the period 1979 -1995. By filtering the annual and short ( B 12 months) time-scale variations, results of empirical orthogonal function analysis show three leading modes of rainfall variation identified with interannual, decadal and long-term variability. Together, these modes explain more than half the total variance of the filtered data.The first mode is highly correlated with El Niñ o -Southern Oscillation (ENSO), showing a regional rainfall anomaly pattern largely consistent with previous results. This mode captures the summer season interannual variability, not only the Northeast Brazil drought but also its connection with excessive rainfall over Southern Brazil and the Ecuador coast in El Niñ o years. Another distinctive feature is the strengthening of the low-level flow along the eastern foothills of the eastern Andes, signifying an enhancement of the South American summer monsoon in response to an El Niñ o anomaly.The decadal variation displays a meridional shift of the Inter-Tropical Convergence Zone (ITCZ), which is tied to the anomalous cross-equatorial SST gradient over the Atlantic and the eastern Pacific. Associated with this mode is a large-scale mass swing between polar regions and the mid-latitudes. Over the South Atlantic and the South Pacific, the anomalous subtropical high and the associated anomalous surface wind are dynamically consistent with the distribution of local SST anomalies, suggesting the importance of atmospheric forcing at the decadal time scale.The long-term variation shows that since 1980 there has been a decrease of rainfall from the northwest coast to the southeast subtropical region and a southwards shift of the Atlantic ITCZ, leading to increased rainfall over northern and eastern Brazil. Possible links of this mode to the observed SST warming trend over the subtropical South Atlantic and to the interdecadal SST variation over the extratropical North Atlantic are discussed.

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bOxygenous terpenoids are active components of many medicinal plants. However, current studies that have focused on enzymatic oxidation reactions cannot comprehensively clarify the mechanisms of oxygenous terpenoid synthesis and diversity. This study shows that an endophytic bacterium can trigger the generation of reactive oxygen species (ROS) that directly increase oxygenous sesquiterpenoid content and diversity in Atractylodes lancea. A. lancea is a famous but endangered Chinese medicinal plant that contains abundant oxygenous sesquiterpenoids. Geo-authentic A. lancea produces a wider range and a greater abundance of oxygenous sesquiterpenoids than the cultivated herb. Our previous studies have shown the mechanisms behind endophytic promotion of the production of sesquiterpenoid hydrocarbon scaffolds; however, how endophytes promote the formation of oxygenous sesquiterpenoids and their diversity is unclear. After colonization by Pseudomonas fluorescens ALEB7B, oxidative burst and oxygenous sesquiterpenoid accumulation in A. lancea occur synchronously. Treatment with exogenous hydrogen peroxide (H 2 O 2 ) or singlet oxygen induces oxidative burst and promotes oxygenous sesquiterpenoid accumulation in planta. Conversely, pretreatment of plantlets with the ROS scavenger ascorbic acid significantly inhibits the oxidative burst and oxygenous sesquiterpenoid accumulation induced by P. fluorescens ALEB7B. Further in vitro oxidation experiments show that several oxygenous sesquiterpenoids can be obtained from direct oxidation caused by H 2 O 2 or singlet oxygen. In summary, this study demonstrates that endophytic bacterium-triggered ROS can directly oxidize oxygen-free sesquiterpenoids and increase the oxygenous sesquiterpenoid content and diversity in A. lancea, providing a novel explanation of the mechanisms of oxygenous terpenoid synthesis in planta and an essential complementarity to enzymatic oxidation reactions.A tractylodes lancea is a traditional Chinese medicinal plant and is the main ingredient of many famous Chinese medicines. Oxygenous sesquiterpenoids, such as hinesol, ␤-eudesmol, atractylone, and caryophyllene oxide, are the main active components in A. lancea and have medicinal efficacy against rheumatic diseases, digestive disorders, night blindness, and influenza (1). The quality of A. lancea strongly depends on the area in which the herb is produced, and A. lancea grown in the Maoshan area of the Jiangsu Province is the geo-authentic herb (2), which is characterized by higher oxygenous sesquiterpenoid content and diversity than herbs grown in other areas (3). In recent years, the geoauthentic A. lancea has become endangered due to habitat destruction and overexploitation. Although cultivation ensures the production of medicinal materials, the oxygenous sesquiterpenoid content and diversity in cultivated A. lancea is considerably decreased compared to that of the wild herb. Currently, knowledge on the biosynthesis and diversity of oxygenous sesquiterpenoids is insufficient. Some studies have explained...

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We describe the rainfall and circulation anomalies of the South American summer monsoon (SASM) during December-January-February (DJF) of 1997-98 (El Niño) and 1998-99 (La Niña). The most pronounced rainfall signals in DJF 1997-98 include (a) excessive rainfall over northern Peru and Ecuador, (b) deficient rainfall over northern and central Brazil, and (c) above-normal rainfall over southeastern subtropical South America. The rainfall anomalies in (a) and (b) are associated with the excitation of an anomalous east-west overturning cell with rising motion and low-level westerlies over the equatorial eastern Pacific, coupled to sinking motion and low-level easterlies over northern Brazil. The easterlies turn sharply southeastward on encountering the steep topography of the Andes, enhancing the summertime low-level jet (LLJ) along the eastern foothills of the Andes near 15-20°S, possibly contributing to the increased rainfall in (c).During DJF 1997-98, the sea-surface temperature-induced warming spreads and expands over the entire tropical troposphere. The eastward expansion of a warm upper tropospheric geopotential and temperature ridge from the Niño-3 region, across subtropical South America to the southeast Atlantic, enhances warming over the Altiplano Plateau, hydrostatically strengthening the Bolivia high. Similar to previous warming events, the South Pacific high is weakened, and the South Atlantic high is strengthened. During DJF 1998-99, as cold water develops over the equatorial central Pacific, the SASM anomalies in the tropics are weaker and less organized and appear to be in transition to the opposite phase to those found in DJF 97-98. In the subtropics, notable features include a weakening of the LLJ, a rainfall pattern associated with a poleward shift of the South Atlantic convergence zone, and development of the Pacific-South America teleconnection pattern. Published in