热带地区出射长波辐射的长程持续性研究

LONG-TERM MEMORY BEHAVIORS FOR OUTGOING LONGWAVE RADIATION IN THE TROPICS

为了探索热带地区出射长波辐射(OLR)的内在变化规律,利用去趋势波动分析(DFA)方法,对整个热带地区(0~357.5°E,22.5°S^22.5°N)1979—2013年NOAA逐日的OLR资料进行分析。研究结果表明:整个热带地区的OLR存在幂律相关,其标度指数值主要集中在0.65~0.72之间,具有较好的长程相关性(或持续性)。西太平洋、刚果盆地和南美洲因对流发展旺盛,导致上空高云量偏大,OLR值主要取决于云顶温度和云量,而云本身变化较快,使得该地区OLR表现出较弱的长程持续性;中东太平洋、大西洋和撒哈拉沙漠地区上空高云量偏少,OLR值主要取决于海表或陆表的温度,而海表或陆表温度变化相对比较缓慢,使得该地区OLR表现出较强的长程持续性。此外,通过随机打乱逐日OLR时间序列去除趋势和相关性,进一步验证了热带地区OLR的长程持续性是由时间序列的分形特征造成的。

In order to explore inner change patterns of OLR over the tropics, daily outgoing longwave radiation （OLR） records （1979-2010） from NOAA are analyzed by using the detrended fluctuation analysis （DFA） method. The results indicate that the OLR over the tropics is power-law correlation and the value of scaling exponents is between 0.65 and 0.72 in most of the cases. Therefore, the OLR has strong long-range correlation （or consistency）. The value of the OLR mainly depends on the cloud-top temperature and cloudiness due to strong convection in the western Pacific, the Congo Basin and South America. The clouds of these are asvary rapidly, which results in a weak long-term memory of the OLR in these regions. While the value of the OLR in the Middle East Pacific, Atlantic Ocean and Sahara Desert mainly relys on the sea surface or the land surface temperature, since the sea surface or land surface temperature barely change, which makes the OLR show a strong long-term memory. In addition, the long-term memory behaviors of the OLR in the tropics are caused by the fractal characteristics of time series, and further proved by randomly disrupting the time series to remove trends and correlation.