Font Size: a A A

The Tree-ring Record Of March To October Monthly Average Maximum Temperature Over The Past 195 Years For The Lin Xia Region, Gansu Province

Posted on:2016-09-14Degree:MasterType:Thesis
Country:ChinaCandidate:J L RenFull Text:PDF
GTID:2180330479993036Subject:Quaternary geology
Abstract/Summary:PDF Full Text Request
As we all know that present is the key to the past. And we can better predict the future from the past. Our country has historically been a large agricultural one, and climate has a great effect on it. Knowing past climate can better serve agricultural production. We can use proxies to study the past climate, such as loess, abyssal sediments, coral reefs, stalagmites, historical documents and so on. The above proxy data are often replenished by tree-ring because of wide distributiuon, high resolution, accurate dating, and strong continuity, while maybe above proxy data are the limitation of time and space, low resolution, and not easy to get.In China, the study area of tree-ring is located in arid and semi-arid regions and Tibetan Plateau, because trees in these regions are sensitive to the natural climate change. On the other round, the characteristic of tree rings can response to the past climate change. In recent years, China has made a series of achievements on dendroclimatology, which does benefits to research the global climate change and climatic spatial temporal features.Global warming was widely accepted in the 20 th century, but there were diversities in different regions. This paper analyzed the background of the regional response to global change in the LinXia region of the west of the loess plateau by tree-ring width. Sampling points is located in the Song Mingyan National Forest Park in LinXia City, Gan Su Province, and it belongs to the northern predmont of LinXia Taizi Mountain(35.24°N, 103.40°E). According to the growth conditions of the trees, 39 tree cores from 21 different trees were collected, and recorded as SMY. This sampling point’s altitude is from 2551 to 2638 m, which is located below the Picea Purpurea’s tree line.The tree-ring lab of Institute of Earth Environment, Chinese Academy of Science collected samples in May, 2013. The main conclusions of the dendroclimatical studies about Piceapurpurea Mast. for LinXia region Gansu province are listed as follows:(1) Using ARSTARN program, which handled the data of tree-ring width by removing the growing trend of trees(negative exponential or linear trend).(2) This study calculated the correlation between the STD chronology and the meteorological data from the near meteorological stations, LinXia station, LinTao station and MinXian station, and we also calculated the correlation between STD chronology and the data of PDSI(the data from Dai PDSI grid point). The results were STD chronology had a low correlation with precipitation and PDSI, but has a remarkable correlation with temperature. The highest correlation is between STD chronology and March to October monthly average maximum temperature from LinXia meteorological station.(3)Based upon the correlation analysis, a multiple regression equation was generated. We reconstructed the mean maximum temperature from March to October of 1818-2012 A.D. using the equation in study region. The explained variance reached 40%, and 38% after adjusting degree of the freedom. MTM analysis showed remarkable 42.74, 7.79-3.18 and 2.77 year cycles at a 95% confidence level for the past 195 years.(4)The reconstruction sequence displayed the fluctuation of temperature in this region. The years of high temperature and low temperature in reconstruction sequence are roughly same, respectively 14.9% and 12.9%. After an 11-year moving average, the reconstruction showed that cold and warm intervals appear alternatively in decadal scale. This presents four warm periods(1818-1854, 1882-1900, 1937-1966, 2001-2012), with temperatures lower than the mean; and three cold periods(1855-1881, 1901-1936, 1967-2000), with temperatures higher than the mean. Moreover, the reconstruction temperature curve didn’t show a significant warming trend at the early stage over the past 195 years, but a significant warming trend in the late 20 th century, and it was up to 0.79 from 1℃ 891-1900 mean maximum temperature to 2001-2010 mean maximum temperature, which matched well with the IPCC Fifth Report. This showed that LinXia region responded to this global warming event. During the past 195 years, the temperature of 1864 to 1870 a was the coldest period.(5) The reconstruction curve matched well with drought index of LanZhou, annual average temperature departure of West QinLing Mountain region, which explained that the climate change in this study region might represent temperature change in a large scale. Spatial analysis showed that 3-10 monthly mean temperature change has a certain spatial representation in LinXia region, which could stand for the variation of temperature on the central west of Loess Plateau.
Keywords/Search Tags:LinXia, Picea purpurea Mast., tree-ring width, temperature reconstruction
PDF Full Text Request
Related items