南海夏季风爆发迟早年对流层温度场演变特征及其热力成因

Evolutions of Temperature Fields in Troposphere and Corresponding Thermal Mechanisms in the Early and Late Onset Cases of South China Sea Summer Monsoon

分析了１９９３与１９９４年南海夏季风爆发前后华南上空温度场演变特征及其热力过程．结果表明：南海夏季风的爆发与华南及邻近地区对流层的季节性增温从而使得华南与赤道地区对流层的南北温差逆转的现象有密切联系；暖平流作用是导致南海季风爆发前华南地区上空对流层增温的一个重要因子．在此期间由上升运动引起的绝热冷却过程总是抑制对流层的增温；非绝热加热因子对温度局地变化的贡献依赖于华南地区降水的多寡．由于１９９４年４月中的南北温差及此后的赤道上空增温都比１９９３年的弱，而且１９９４年４月中至５月初华南上空的增温比１９９３年同期的明显、最终南海季风区的南北温度梯度逆转早，季风爆发较早．相对而言，１９９３年的南北温度梯度逆转比１９９４年迟，季风爆发也偏迟。

The evolutions of the troposphere temperature fields during March to June in 1993 and 1994 over South China Sea(SCS) monsoon area and their thermal mechanisms are analyzed. Results show that the onset of SCS summer mousoon is closely associated with the seasonal warming in troposphere over the zonal belt of 10 - 30°N, which leads to the inversion of meridional temperature gradient (MTG). Before the SCS monsoon onset, the warm horizontal advection plays an very important role for the local warming over the South China region, and the contribution from diabatic heating to the local warming mainly depends on the precipitation rate over the South China region, while the local warming is suppressed by the vertical adiabatic process(cooling). From middle April to early May the warming in the mid-upper troposphere over the South China in 1994 is stronger than that in 1993. However, the MTG during the middle of April and the warming rate over the equatorial region in 1994 are weaker than those in 1993. Consequentially, the, inversion of MTG occurs earlier in 1994 than in 1993.