Considering the different uplifting time of different subregions of the Himalaya-Tibetan Plateau(TP),a series of numerical simulations have been conducted with the Community Atmosphere Model(CAM4) developed at the National Center for Atmospheric Research to explore the effects of the phased tectonic uplift of the Himalaya-TP on the evolution of Asian summer monsoons.The results show that the uplifts of the Himalaya and northern TP significantly affect the evolutions of South Asian summer monsoon and northern East Asian summer monsoon respectively.That is,the tectonic uplift of the Himalaya intensifies the South Asian summer monsoon circulation and increases the precipitation in South Asia,whereas the uplift of the northern TP intensifies the northern East Asian summer monsoon circulation and increases the precipitation in northern East Asia.Compared with previous simulations,current comparative analyses of modeling results for different subregional uplifts within the Himalaya-TP help deepen our understanding of the evolutionary history of Asian monsoons.
ZHANG Ran 1,JIANG DaBang 1,2,3,LIU XiaoDong 4 & TIAN ZhiPing 2,5 1 Climate Change Research Center,Chinese Academy of Sciences,Beijing 100029,China
Atmospheric CO2 concentrations from January 2010 to December 2010 were simulated using the GEOS-Chem(Goddard Earth Observing System-Chemistry) model and the results were compared to satellite Gases Observing Satellite(GOSAT) and ground-based the Total Carbon Column Observing Network(TCCON) data. It was found that CO2 concentrations based on GOSAT satellite retrievals were generally higher than those simulated by GEOS-Chem. The differences over the land area in January and April ranged from 1 to 2 ppm, and there were major differences in June and August. At high latitudes in the Northern Hemisphere in June, as well as south of the Sahara, the difference was greater than 5 ppm. In the high latitudes of the Northern Hemisphere the model results were higher than the GOSAT retrievals, while in South America the satellite data were higher. The trend of the difference in the high latitudes of the Northern Hemisphere and the Saharan region in August was opposite to June. Maximum correlation coefficients were found in April, reaching 0.72, but were smaller in June and August. In January, the correlation coefficient was only 0.36. The comparisons between GEOS-Chem data and TCCON observations showed better results than the comparison between GEOS and GOSAT. The correlation coefficients ranged between 0.42(Darwin) and 0.92(Izana). Analysis of the results indicated that the inconsistency between satellite observations and model simulations depended on inversion errors caused by data inaccuracies of the model simulation's inputs, as well as the mismatch of satellite retrieval model input parameters.
The relationship between winter sea surface temperature (SST) east of Australia and summer precipitation in the Yangtze River valley and a possibly related physical mechanism were investigated using observation data.It is found that winter SST east of Australia is correlated positively to summer precipitation in the Yangtze River valley.When the SST east of Australia becomes warmer in winter,the western Pacific subtropical high and the East Asian westerly jet tend to shift southward the following summer,concurrent with low-level southwesterly anomalies over eastern China.These conditions favor precipitation increase in the Yangtze River valley,whereas the opposite conditions favor precipitation decrease.The influence of winter SST east of Australia on East Asian summer atmospheric circulations may occur in two ways.First,by an anomalous SST signal east of Australia in winter that persists through the following summer,thus affecting East Asian atmospheric circulations via the inter-hemispheric teleconnection.Second,when the SST east of Australia is warmer in winter,higher SST appears simultaneously in the southwest Indian Ocean and subsequently develops eastward by local air-sea interaction.As a result,the SST in the Maritime Continent increases in summer,which may lead to an anomalous change in East Asian summer atmospheric circulations through its impact on convection.
