A climatological northern boundary index for the East Asian summer monsoon and its interannual variability

A long-term perspective on the spatial variation of the northern boundary of the East Asian summer monsoon(EASM) and the related physical mechanisms is important for understanding past climate change in Asia and for predicting future changes. However, most of the meteorological definitions of the EASM northern boundary do not correspond well to the actual geographical environment, which is problematic for paleoclimatic research. Here, we use monthly CMAP and GPCP precipitation data to define a new EASM northern boundary index by using the concept of the global monsoon, which is readily applicable to paleoclimatic research. The results show that the distribution of the 2 mm day^(-1) precipitation isoline(i.e., 300 mm precipitation)has a good relationship with the spatial distribution of modern land cover types, the transitional climate zone and the potential natural vegetation types, in China. The locations of the precipitation isolines also correspond well to the locations of major shifts in wind direction. These results suggest that the 2 mm day^(-1) isoline has a clear physical significance since the climatic, ecological,and geographical boundary can be used as the northern boundary index of the EASM(which we call the climatological northern boundary index). The index depicts the northeast-southwest orientation of the climatological(1981-2010) EASM northern boundary, along the eastern part of the Qilian Mountains-southern foothills of the Helan Mountains-Daqing Mountains-western margin of the Greater Khingan Range, from west to east across Northwest and Northeast China. The interannual change of the EASM northern boundary from 1980 to 2015 covers the central part of Gansu, the northern part of Ningxia, the eastern part of Inner Mongolia and the northeastern region in China. It can extend northward to the border between China and Mongolia and retreat southward to Shangdong-central Henan. There is a 200-700 km fluctuation range of the interannual EASM northern boundaries around the locations of the climatological northern boundary. In addition, the spatial variation of the interannual EASM northern boundaries gradually increases from west to east, whereas the trend of north-south fluctuations maintains a roughly consistent location in different regions.

The northern boundary of the Asian summer monsoon and division of westerlies and monsoon regimes over the Tibetan Plateau in present-day

Precipitation patterns and their variations over the Tibetan Plateau(TP) are mainly dominated by the Asian summer monsoon, westerlies, and their interactions. The exact extent of the Asian summer monsoon’s influence, however, remains undetermined. Referencing the climatological northern boundary index of the East Asian summer monsoon, we demonstrate that the 300 mm precipitation isoline from May to September can be utilized as an indicator of the northern boundary of the Asian summer monsoon over the TP, allowing for an analysis of the spatial distribution characteristics of the climatological and interannual northern boundary. Our results indicate that the climatological northern boundary of the Asian summer monsoon over the TP lies along the eastern Qilian Mountains-Tanggula Mountains-Qiangtang Plateau-Gangdise Mountains-Western Himalayas during 2001–2020. This position corresponds well with the position of the convergence of westerly(westerlies) and southerly wind(monsoon) in the lower troposphere, representing the interface between dry and wet regions in the rainy season over the TP. There is a significant positive correlation between changes in the zonal/meridional water vapor budget and variations in precipitation to the north/south of the climatological northern boundary, respectively. Additionally, a close relationship exists between the interannual fluctuation range of the northern boundary and the distribution of vegetation across the TP. Compared to the northern boundary of the summer monsoon defined by meteorological criteria, which is established based on 5-day(pentad)mean precipitation(exceeding 4 mm day^(-1)), our climatological northern boundary offers a more objective portrayal of the region that experiences persistent influence from the summer monsoon. These indicate that climatological northern boundary has a clear significance for natural geographical distribution such as the westerlies-monsoon circulation, ecology, and climate. Based on the interannual fluctuation range of the northern boundary, we divided the TP into domains of westerlies, monsoon, and westerliesmonsoon transition. This study could serve as a foundation for further investigation into the interactions between westerlies and monsoon, variations in precipitation patterns and hydrological-ecological systems over the TP.

Integration system research and development for three-dimensional laser scanning information visualization in goaf

An integration processing system of three-dimensional laser scanning information visualization in goaf was developed. It is provided with multiple functions, such as laser scanning information management for goaf, cloud data de-noising optimization, construction, display and operation of three-dimensional model, model editing, profile generation, calculation of goaf volume and roof area, Boolean calculation among models and interaction with the third party soft ware. Concerning this system with a concise interface, plentiful data input/output interfaces, it is featured with high integration, simple and convenient operations of applications. According to practice, in addition to being well-adapted, this system is favorably reliable and stable.