A rich content and system of knowledge, mature research methods in dendrohydrology provide accurate methods for studying long-term hydrologic variability at regional scale.
树木年代学丰富的内容和知识体系，成熟的研究方法，为区域尺度上研究水文变化提供了精确的方法。
2
Climate change is all about longterm trends, which are hard to detect in a weather record which has very large natural variability.
气候变化是长期的，我们不能用一种天气情况来判断说有大的气候自然变异。
3
The negative correlation between the interannual variability of IODM and that of SCS summer monsoon is significant during the warm phase of long-term trend but insignificant during the cool phase.