2006年春季珠江口海岸带近地面层热通量收支的观测研究

Observational study on heat flux in the coastal zone of Pearl River mouth in spring 2006

利用中国气象局广州热带海洋气象研究所在珠江口岸边2006年3—5月观测的气象资料,用涡动相关法计算了该区域近地面层的热通量(潜热和感热通量),同时分析了海面净辐射和净热通量的一些特征。经分析发现,热通量在观测期内逐月增大,其在5月份的增幅比前两个月更加明显。各个不同时段和天气过程的平均值显示,热通量的交换在此季节内以潜热为主。冷锋入侵时带来的干、冷空气活动引起的水汽蒸发、感热巨变的"脉冲"过程对热通量有较大的影响,观测期内冷空气出现的天数占总观测天数的16.5%,而在冷空气活动期间交换的热通量值占总观测期内的25.6%,其中潜热占17.4%。月平均的海面净辐射和净热通量从3月到4月有一个较大的增幅,净辐射从4月到5月也是增加的,增幅较小,但是净热通量的值在5月反而小于4月,只略高于3月,这归因于5月份热通量的交换能力增强,海水释放的热量增多,使得海洋储存起来的净热通量在5月份反而减少,表明春季该海域储存在海洋中的热量在4月份是最多的。在各月或者季节平均的日变化中,各通量在相同时次的量值都逐月增大。潜热在15时左右达到峰值,感热在9时前后达到最大,感热的最小值发生在夜间而非午间,二者均在夜间比较稳定、少变。海面净辐射与净热通量基本同步变化,都呈单峰型。白天,二者均为正值,且净辐射值大于净热通量值;夜间,二者均为负值,净热通量的绝对值大于净辐射的绝对值。在3—4月的日变化中,净辐射与净热通量之间的差值较小,5月份二者的差值增大,虽然净辐射强度在5月接近4月的值,但是感热和潜热在日变化中的相同时次都有较大幅度的增加,使得海洋净支出热量增多。

Based on the observed data at the mouth of the Pearl River from March to May in 2006 and eddy covariance measurements,the heat fluxes of the atmospheric boundary layer（ABL）,including sensible heat flux（QH）,latent heat flux（QLE）,the sea surface net radiation（RN） and net heat flux（QN）,are analyzed.Both QHand QLEincrease from March to May,and they are much larger in May than in the two previous months.Data of different synoptic processes or time periods shows that QLE dominates the ABL heat flux exchange.Several ＂pulse＂ processes induced by incursions of cold surges with cold and dry air masses influence the heat flux greatly.During the observational period,about 16.5% of the total observational days encountered cold surges,while the heat fluxes in the cold surge days accounted for approximately 25.6% of the total heat flux variation,suggesting that the incursions of cold surges had significant impacts on the ABL heat flux.Monthly average data of RN and QN reveals that both of them increase by a large margin from March to April,and RN also increases from April to May;but at the same time QN decreases,which indicates that the heat flux stored in the ocean in April is the largest.During the average diurnal cycle,the latent heat flux,with a maximum at 15：00 in the afternoon,is always positive.However,the sensible heat flux is positive during the daytime but negative during many hours at night,reaching its peak at about 9：00 in the morning.RN and QN vary at the same time.Both of them are positive during the day,and RN is bigger than QN;at night,both of them are negative,and the absolute value of QN is a little bigger than RN.The difference between RN and QN in May is much greater than in March and April,because the exchange capacity of heat flux has been reinforced in May,which makes the ocean release much more potential energy.