Scientists recalibrate the traditional Chinese Solar Terms with big meteorological data

The traditional calendar of the Twenty-four Solar Terms (24-STs) is a great intellectual invention of Chinese ancestors. It is a brilliant comprehensive summary of the knowledges and experiences on climate, astronomy, and agricultural activities which can be traced back to over 3,000 years ago. The 24-STs were originally defined according to the climate and phenology of the ancient Yellow River Basin (YRB). Although the basic philosophy of the 24-STs remains valid for the country as a whole to date, their regional robustness has been increasingly challenged by accumulating observational data in terms of temporal shift and spatial inhomogeneity.

"To tackle these issues, we propose to recalibrate the medically related critical timings of Great Heat (GH) and Great Cold (GC) in the classic ST system by using big meteorological data, and adjust them by introducing geographically correlated analytical models", according to Ge Chen, scientist at College of Information Science and Engineering, Ocean University of China, in the Chinese city of Qingdao.

Collaborated with Jie Shi, a senior pharmacologist at the Municipal Hospital of Qingdao, a novel calendric system, called the Twenty-four Medical Terms (24-MTs), has been developed as an upgraded version of the traditional 24-STs.

Two series of procedures are performed to upgrade the 24 Terms from a solar nature to a meteorological nature. First of all, a grid-based calibration is applied for correcting the long-term drift of these critical time nodes due to climate changes as a possible consequence of global warming and its hiatus as well as urbanization effects. The two extreme STs in terms of SAT, GH and GC, are naturally used as reference timings for adjusting these effects, while the remaining meteorologically related STs are rescaled to the new MT system. It turns out that the MT-GH and MT-GC may depart from their ST counterparts by -15~5 days depending on the region. Moreover, it is found that the assumption of a systematic 180? phase reversal between GH and GC as well as other corresponding STs is often misleading. The warming period of the year is in fact 10-20 days longer than the cooling period for many areas of China.

As follow-up steps, a 2-D map of each rescaled MT is constructed and integrated into an assembled model, resulting in a MT-GIS which is, to our knowledge, the first of its kind reported in the literature. Two fundamental features are revealed by this MT-GIS: (1) A systematic temporal drift up to +-20 days is observed between many corresponding STs and MTs. (2) For a given MT, a nationwide maximum spatial discrepancy in its timing can also exceed 20 days. These two features combine to confirm that the 24-MTs are indeed inconsistent in time and inhomogeneous in space. Therefore, a geographically dependent (localized) calendar is necessary to estimate their accurate timings and evaluate their precise impacts.

The two scholars emphasized in their study, which was published in SCIENCE CHINA Earth Sciences, that the proposed 24-MTs are characterized by two striking features with respect to the 24-STs: A varying duration of each MT instead of a fixed one for the ST, and a geographically dependent timing for each MT instead of a unified one for the entire nation. As such, the updated 24-MTs are expected to provide a more realistic estimate of these critical timings around the year, and hence, a more precise guidance to agronomic planning and health care activity in China.


This research was funded by National Natural Science Foundation of China (No. 61361136001).

See the article:

(1) Chen G, Shi J. 2017. From solar terms to medical terms (Part I): A first step with big data. Science China Earth Sciences, 60, doi: 10.1007/s11430-016-9059-0

(2) Shi J, Chen G. 2017. From solar terms to medical terms (Part II): Some implications for traditional Chinese Medicine. Science China Earth Sciences, 60, doi: 10.1007/s11430-016-9060-5

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