基于气候系统内在层次性的气象干旱指数研究

Research on the Meteorological Drought Index Based on the Hierarchy of Climate System

气候系统除了具有非线性/非平稳性,还有层次性,许多大小不一的时空尺度构成了多层次结构,不同层次的气候系统具有不同的可预报性和稳定性。对于一种气象干旱指数而言,主要考虑从某一时段(尺度)内降水、温度、土壤湿度等要素测量值来建立干旱指数。本文首先从气候系统的非线性/非平稳性和内在层次性出发,针对中国不同地区的区域气候及其变化特征,使用信息熵方法从降水观测资料中提取出区域降水的两个(均态和变化)本征尺度,提出一种基于区域气候系统层次性内在特征的气象干旱指数MSPI。以2011年长江中下游春季严重气象干旱的发生、发展、持续、缓解情况为例,对MSPI的干旱监测能力进行检验。发现MSPI对不同程度的干旱都有较好的表征能力,并且对于干旱过程也有较好的识别能力。从各方面综合考虑,MSPI是一种可以较好满足逐日气象干旱监测、检测需求的气象干旱指数。在实际应用中,气象干旱指数MSPI可以作为其他不同时间尺度上的各种干旱指数的有益补充。

The climate system is nonlinear and non-stationary, in addition, it is also hierarchic, thus it is a multi-level structure formed by many different spatio-temporal scales, and each spatio-temporal scale has different predictability and stability respectively. When we research a meteorological drought index, we generally consider the precipitation, temperature, relative moisture of soil and other essential factors in certain period of time. By taking account of the climatic characteristics of different regions, the comentropy method is first used to obtain the two intrinsic scales of zonal precipitation i.e. the homogeneous state in- trinsic scale and the variational state intrinsic scale because of the conception that the climate system is nonlinear, non-stationary and hierarchic, then a new meteorological drought index named MSPI is devel- oped. Afterwards, the appearance, development, continuance and alleviation of the severe meteorological drought in the middle and lower reaches of the Changjiang River in 2011 are taken as an example to exam- ine the ability of MSPI to monitor the meteorological drought. The result shows that MSPI can monitor meteorological drought at different grades and can distinguish the course of meteorological drought perfect- ly. Taking all factors into consideration, we think that the MSPI is an efficacious meteorological drought index which can meet the demands to monitor and detect meteorological drought. In practice, the MSPI could be as a useful complement to other meteorological drought indices.