| Surface map analysis is one of the key component of weather analysis and forecasting, it can help forecasters diagnose the distribution of meteorological elements, analyze synoptic situation and the distribution and evolution of surface weather system, but do not analyze the surface isotherm because of the lack of observation. With the acquisition of the high spatial and temporal resolution data, Sanders suggest the application of using conventional analysis while analyzing surface isotherm, as well as a detailed classification conceptual model on fronts. Based on this, cases study on baroclinic zone is investigated, and the concept of wet baroclinic zone is introduced.The annual and seasonal mean surface potential temperature in eastern part of mainland China during the period of1st December,2008to30th November,2009, is discussed first, as well as the frequency of moderate and strong potential temperature gradients based on the daily analysis of surface potential temprature. The result shows that moderate potential temperature gradients mainly occur in Taihang mountain and its adjacent sloping terrain regions, coastal area of Yellow Sea and Bo Sea and southeast China, strong potential temperature gradients mainly occur in a small region of Taihang mountain and its south adjacence. Gradients in Taihang mountain and its adjacent sloping terrain regions show little seasonal and diurnal variability except a slight change of area. Gradients in other two region show evident seasonal and diurnal variability. In spring and summer, Moderate gradients occur in coastal area of Fujian, show little diurnal variability. In autumn and winter, Moderate gradients occur in coastal area of Yellow Sea and Bo Sea as well as southeast China in the early morning, and coastal area of Fujian and Zhejiang at dusk. The high frequency regions of potential temprature gradients revealed by the analysis on climatic characteristics indicate permanent or semipermanent gradients in this region, while gradients occurred in the low frequency regions are mostly caused by synoptic scale systems or indicate the high potentiality of weather system evolutionSurface weather system in Mei-yu period in Jiangsu, during the period of19th June to10th July,2007and the torrential rain occurred in Beijing on21th July,2012, is discussed based on the modified surface map analysis method. The results show that1) Dense surface observation data can represent the real surface thermal distribution, it makes the distinction between front and front-like system possible through surface isotherm analysis.2) Non-frontal baroclinic zones and baroclinic troughs do exist besides typical Meiyu front in the surface system during Mei-yu period in Jiangsu, the strong baroclinic zone corresponds with rainfall area, and frontogenesis occurs in the baroclinic zone. Moreover, it can be repetitive process of local frontogenesis and frontolysis sometimes rather than all quasi-stationary fronts in Yangtze-Huaihe region stay stationary.3) Wet baroclinic zone is introduced during the torrential rain occurred in Beijing, the wet baroclinic zone corresponds with rainfall area in the current time and some time in the future, especially in the warm area. Wet baroclinic zones are the symbol of strong precipitation area as well as a early warning area.The results of applying the surface isotherm analysis and the concept of baroclinic zones show the method is applicable in the Mei-yu period of Jiangsu in2007and the torrential rain occurred in Beijing on21th July2012. The classification of non-frontal baroclinic zones, baroclinic troughs and conventional fronts based on the surface isotherm analysis and wind field analysis can reduce the contradictory situation as’weak front’or missing report of weather system, and the analysis of baroclinic zones can provide weather forecasters early warning. They play a positive role in improving the subjective weather forecasting accuracy. |
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