NUMERICAL SIMULATION OF THE SEASONAL VARIATION OF TROPOSPHERIC OZONE OVER CHINA

An updated version of the Regional Acid Deposition Model(RADM)driven by meteorological fields derived from Chinese Regional Climate Model(CRegCM)is used to simulate seasonal variation of tropospheric ozone over the eastern China.The results show that: (1)Peak O_3 concentration moves from south China to north China responding to the changing of solar perpendicular incidence point from south to north.When solar perpendicular incidence point moves from north to south,so does the peak O_3 concentration. (2)In the eastern China.the highest O_3 month-average concentration appears in July.the lowest in January and the medium in April and October.The pattern mainly depends on the solar radiation,the concentration of O_3 precursors NO_x and NMHC and the ratio of NMHC/NO_x. (3)Daily variations of O_3 over the eastern China are clear.Namely,O_3 concentrations rise with the sun rising and the maximums appear at noon.then O_3 concentrations decrease.The highest daily variation range of O_3 appears in summer(40×10^(-9) in volume fraction)and the lowest in winter(20× 10^(-9) in volume fraction). (4)Daily variations of O_3 over the western China are not clear.The daily variation range of O_3 is less than 10×10^(-9) in volume fraction.

Numerical simulation on seasonal transport variations and mechanisms of suspended sediment discharged from the Yellow River to the Bohai Sea

Based on sediment and discharge flux data for the Yellow River, realistic forcing fields and bathymetry of the Bohai Sea, a suspended sediment transport module is driven by a wave-current coupled model to research seasonal variations and mechanisms of sus- pended load transport to the Bohai Sea. It could be concluded that surface sediment concentration indicates a distinct spatial distribution characteristic that varies seasonally in the Bohai Sea. Sediment concentration is rather high near the Yellow River estuary, seasonal variations of which are controlled by quantity of sediment from the YeUow River, suspended sediment concentration reaches its maximum during summer and fall. Furthermore, sediment concentration decreases rapidly in other seas far from the Yellow River estuary and maintains a very low level in the center of the Bohai Sea, and is dominated by seasonal variations of climatology wind field in the Bohai Sea. Only a small amount of sediments imported from the Yellow River are delivered northwestward to the southern coast of the Bohai Bay. Majority of sediments are transported southeastward to the Laizhou Bay, where sediments are con- tinuously delivered into the center of the Bohai Sea in a northeastward direction, and part of them are transported eastward alongshore through the Bohai Strait. 69% of sediments from the Yellow River are deposited near the river delta, 31% conveyed seaward, within which, 4% exported to the northern Yellow Sea through the Bohai Strait. Wind wave is the most essential contributor to seasonal variations of sediment concentration in the Bohai Sea, and the contribution of tidal currents is also significant in shallow waters when wind speed is low.

平流层臭氧季节变化的动力和光化学作用之比较

1992年到2005年的HALOE资料显示,在臭氧光化损耗中,ClOx和NOx的贡献大小和作用位置有所差异。SOCRATES3模式模拟表明,两半球夏季高纬极区的臭氧减少,主要是NOx的化学贡献;北极春季和南极冬季副极地臭氧的变化,主要是动力输送引起。南、北极春季臭氧减少的化学机制也有所不同,南极春季的臭氧耗损包括极区内ClOx的异相化学作用和副极区NOx的化学作用;北极春季的臭氧耗损主要以NOx和ClOx的气相化学作用为主,其中NOx的作用更大。动力和光化学在臭氧变化中的贡献表明,整个中低平流层及低纬平流层高层的动力输送贡献可达到45%,而高纬平流层中上层,化学作用贡献在65%以上。

南海北部海面高度季节变化的机制

利用POM模式对南海环流进行了数值模拟和数值试验 ,结果表明 :南海北部SSH的变化主要应归于南海局地的动力、热力强迫和黑潮的影响 ;黑潮对南海北部SSH平均态的影响要大于对SSH异常场的影响 ;对于南海北部深水区冬季局地风应力与浮力通量的作用相反量级相同 ,黑潮对南海北部SSH的控制作用在冬季显得最重要 ,约占 50 %～ 80 % ;春季 ,夏季和秋季 ,局地风应力、浮力通量和黑潮三者都使深水区SSH上升 ,局地风应力使深水海盆SSH上升的作用约占 4 0 %～ 6 0 % ,浮力通量的作用约占 2 0 % ,黑潮的影响约占 2 0 %～ 30 % .在夏季 ,尽管南海北部深水海盆SSH达到全年最高 ,但黑潮对南海北部深水海盆SSH的贡献最小 .在广东沿岸陆架海域 ,SSH季节变化的机制与深水海盆SSH季节变化的机制不同 :春、夏季 ,局地风应力使SSH上升的作用几乎与浮力通量使SSH下降的作用相当 ;秋、冬季 ,东北季风使SSH上升的作用大于浮力通量和黑潮使SSH下降的作用 ,陆架区SSH为正 。