青海治多公元1374年以来树轮记录的青藏高原地面加热场强度变化

根据青海省南部玉树藏族自治州治多县629a树木年轮年表序列,依据相关等方法,分析了该年表与树木生长时气温、降水、地面加热场强度的关系。结果表明: 该年表对高原年地面加热场强度反映敏感,由其重建了该区域地面加热场强度的历史序列,并应用交叉检验方法对校准方程进行了检验,证明重建方程稳定,所重建的年地面加热场强度变化比较可靠,具有一定的区域代表性。通过对重建序列的进一步分析得出,重建序列在一定程度上反映了青藏高原年地面加热场强度年际的历史变化。1374年以来在年代际尺度上,持续时间较长的年地面加热场强度特强时段有4个,即1396~1416年、1684~1699年、1816~1826年和1875~1889年; 持续时间较长的年地面加热场强度特弱时段有4个,即1374~1384年、1417~1436年、1802~1812年和1897~1909年。在629a中共出现22个极端强年和8个极端弱年,15世纪出现7个极端强年和5个极端弱年。15~17世纪是年地面加热场强度的多变时期,18~20世纪是年地面加热场强度的相对稳定时段。

SURFACE HEATING FIELD INTENSITY CHANGE OVER TIBETAN PLATEAU FORM RECORDED OF QINGHAI ZHIDUO TREE RINGS SINCE 1374 A.D.

The tree-ring chronologies of the 629a were developed based on cores sampled in Zhiduo County(33°43'N, 96°17'E),southern Qinghai Plateau.Since the sites are situated in the cold region with high elevation from 3900m to 4500m,the stand condition is poor,the tree growth is slow,and the canopy coverage is generally low,the forest there is dominated by Sabina przewalskii Kom.So trees are affected little by human activities,which can reflect the change of environment.The paper analyzed the relationship between the chronology and the air temperature,precipitation,surface heating field intensity with correlation method,and reconstructed the historical series of the surface heating field intensity of the Tibetan Plateau.Through further analysis of the sequence reconstruction obtained that: the rebuilt sequence to some extent reflects the history changes of surface heating field intensity of Tibetan Plateau.The results showed that:(1)A significant positive relationship was found between the anomaly index of surface heating field intensity in the Tibetan Plateau and the ring width.It could be seen that radial growth was negative correlated with surface heating field intensity because of the high surface heat and big soil evaporation,and vise versa.Based on the relation of the high surface heat and tree growth,it reconstructed the historical variables sequence.To test the stability the construction equation,the cross-examination method performed.The sign test of original series,the sign test of the first-order difference series,the sign of average value of product and the reduction of error were calculated.Those results indicated that the regression equation of surface heating field were stable,reliable and typical of this region.(2)The index of surface heating field intensity showed that there existed ten significant cycles of 63.2a,52.7a,45.1a,39.5a,35.1a,31.6a,3.1a,2.6a,2.5a,2.2a at 0.05 confidence level.There were 15 years and 7 years strong periods of surface heating field intensity on the scale of 10a and 30a,respectively.While 14 years and 6 years weak periods.The surface heating field intensity was changeable from the 15th to 17th century,while stable from the 18th to 20th century.The reconstructed series indicated that the surface heating field intensity was larger in the 1960s and 1990s,and smaller in the 1970s and 1980s.(3)Through the inter-decadal variations of the reconstructed annual surface heating field intensity compared the width index series of Qumalai,Zaduo tree-ring and the average maximum temperature of Animaqing Hill,the results indicated that the reconstructed series were four extra strong stages,namely 1396~14161684~16991816~1826 and 1875 to 1889; while there were four extra weak stages,which was 1374~13841417~14361802~1812 and 1897 to 1909,and results were confirmed by science and technology documents,which further illustrate the results were stable.