Moisture Sources and Their Contributions to Summer Precipitation in the East of Southwest China

Complex topography,special geographical location and sea-land-air interactions lead to high interannual variability of summer precipitation in the east of Southwest China(ESWC).However,the contributions,influencing factors and mechanisms of remote and local evaporation remain to be further investigated.Using clustering analysis and Hybrid Single-Particle Lagrangian Integrated Trajectory version 5 model,we analyze the contributions of remote moisture transport and local evaporation to summer precipitation in the ESWC and their causes.There are mainly five remote moisture channels in the ESWC,namely the Arabian Sea channel,Bay of Bengal channel,western Pacific channel,Northwest channel 1 and Northwest channel 2.Among the five channels,the western Pacific channel has the largest number of trajectories,while the Bay of Bengal channel has the largest contribution rate of specific humidity(33.33%)and moisture flux(33.14%).The amount of regional average precipitation is close to that of the precipitation caused by remote moisture transport,and both are considerably greater than the rainfall amount caused by local evaporation.However,on interannual time scales,precipitation recirculation rates are negatively correlated to regional average precipitation and precipitation caused by remote moisture transport but are consistent with that caused by local evaporation.An apparent"+-+"wave train can be found on the height anomaly field in East Asia,and the sea surface temperature anomalies are positive in the equatorial Middle-East Pacific,the South China Sea,the Bay of Bengal and the Arabian Sea.These phenomena cause southwest-northeast moisture transport with strong updrafts,thereby resulting in more precipitation in the ESWC.

Features of the Extremely Severe Drought in the East of Southwest China and Anomalies of Atmospheric Circulation in Summer 2006

The spatial-temporal features of the extremely severe drought and the anomalous atmospheric circulation in summer 2006 are analyzed based on the NCEP/NCAR reanalysis data,the characteristic circulation indices given by the National Climate Center of China,and the daily precipitation data of 20 stations in the east of Southwest China（ESC） from 1959 to 2006.The results show that the rainless period started from early June and ended in early September 2006 with a total of more than 80 days,and the rainfall was especially scarce from around 25 July to 5 September 2006.Precipitation for each month was less than normal,and analysis of the precipitation indices shows that the summer precipitation in 2006 was the least since 1959.The extremely severe drought in the ESC in summer 2006 was closely related to the persistent anomalies of the atmospheric circulation in the same period,i.e.,anomalies of mid-high latitude atmospheric circulation,western Pacific subtropical high（WPSH）,westerlies,South Asian high,lower-level flow,water vapor transport,vertical motion,and so on.Droughts usually occur when the WPSH lies anomalously northward and westward,or anomalously weak and eastward.The extreme drought in summer 2006 was caused by the former.When the WPSH turned stronger and shifted to the north and west of its normal position,and the South Asian high was also strong and lay eastward,downdrafts prevailed over the ESC and suppressed the water vapor transfer toward this area.At the same time,the disposition of the westerlies and the mid-high latitude circulation disfavored the southward invasion of cold air,which jointly resulted in the extremely severe drought in the ESC in summer 2006.The weak heating over the Tibetan Plateau and vigorous convective activities over the Philippine area were likely responsible for the strong WPSH and its northwestward shift in summer 2006.

The potential drivers in forming avian biodiversity hotspots in the East Himalaya Mountains of Southwest China

Little has been published to describe or interpret Asian biodiversity hotspots,including those in the East Himalayan Mountains of Southwest China(HMSC),thus making necessary a review of the current knowledge.The Pliocene and Pleistocene geological and glacial histories of the Asian continent differ from those of Europe and North America,suggesting different mechanisms of speciation and extinction,and,thus,different responses to climate changes during the Quaternary glaciations.This short review summarizes potential drivers in shaping and maintaining high species richness and endemism of birds in the HMSC.The geographical location at the junction of different biogeographical realms,the wide range of habitats and climates along the extensive elevational range,the complex topography and the distinct geological history of this region have probably contributed to the evolution of an exceptionally species-rich and endemic-rich,specialized montane avian fauna.The Mountain systems in the HMSC may have provided refugia where species survived during the glacial periods and barriers for preventing species dispersal after the glacial periods.More studies are required to further test this refugia hypothesis by comparing more cold-tolerent and warm-tolerent species.