Font Size: a A A

Variation And Temporal And Spatial Distribution Of Extreme Climate Events In The Arid Area Of Northwest China

Posted on:2016-01-27Degree:MasterType:Thesis
Country:ChinaCandidate:J X LiFull Text:PDF
GTID:2180330476950284Subject:Physical geography
Abstract/Summary:PDF Full Text Request
Human activities have a profound effect on climate change, global warming is an indisputable fact, which is causing frequency and intensity increase of extreme weather events. Northwest arid area includes the whole Xinjiang region, Hexi Corridor of Gansu region and the westen Helan Mountain of Inner Mongolia.This area has the less annual precipitation, fragile ecological environment and serious land desertification, which is the sensitive area of climate change. This article selects the data of daily maximum temperature, daily minimum temperature and daily precipitation of 72 ground stations from 1960 to 2013 in the northwest arid area, uses the index system of “index of climate change detection and the determination” which is recommended by the world meteorological organization committee, climate change detection, monitoring and index expert group. select eight extreme temperature and six extreme precipitation indices, use climate tendency rate and tendency coefficient method, Mann-Kendall trend test and mutation test, wavelet analysis, DFA long-range trend wave analysis, principal component analysis(PCA) to study the characteristics, temporal and spatial distribution of extreme weather events in the northwest arid area. The 8 extreme temperature indices are cold spell duration indicator(CSDI), warm spell duration indicator(WSDI), cool nights(TN10p), warm nights(TN90p), cool days(TX10p), warm days(TX90p), frost days(FD), summer days(SU); the 6 extreme precipitation indices are max 1-day precipitation amount(RX1day), max 5-day precipitation amount(RX5day), number of heavy precipitation days(R10), Consecutive wet days(CWD), very wet days(R95p), annual total wet-day precipitation(PRCPTOT). The results show that:1) On the inter-annual variability, the extreme climate indices fluctuate change. reflecting the extreme low temperature indices have a downward trend, and the extreme high temperature and extreme precipitation indices are on the rise.2) From the era change, extreme low temperature indices are on the decline, 80 to 90 era is a turning period of extreme weather, before 90 s, it is a positive anomaly, after 90s(including 90s), it is a negative anomaly, the era change of extreme high temperature opposes to the extreme precipitation indices.3) The mutated year of each index is from 80 s to 90 s, it shows that 80 s to 90 s is a transitional phase alternating cold and warm climate change.4) The wavelet analysis results indicate that the extreme temperature indices have three types of 3-8,10-15,25-30 cycle variation, combining the wavelet analysis of variance show that the extreme temperature events have 14 years and 28 years periodic variation; extreme precipitation indices have three types of 3-8,15-20,25-30 cycle variation, combining the wavelet analysis of variance show that extreme precipitation events have 28 years periodic variation.5) Using DFA method to predict the direction and extent of extreme weather events in the coming years, the results show that the extreme temperature and precipitation indices have long-range correlations, each index will continue to rise or fall in the coming years.6) On the space variation, calculate the inter-annual trend of each station, the results show that extreme low temperature indices have a large proportion of stations decline, the stations of largest decline trend are in Turpan, Qijiaojing, Turpan, Tacheng; extreme high temperature indices have a large proportion of stations rise, the stations of largest rise trend are in Aksu, Mazongshan, Qijiaojing, Mazongshan; extreme precipitation indices have a large proportion of stations rise, multiple indices have the largest rise trend in Urumqi, it shows that Urumqi has the maximum frequency of extreme precipitation events.7) The era of space massive research show that the era of mass of extreme temperature events are change. The extreme low temperature events mainly mass in the northern Xinjiang in the 1960 s, mainly mass in the south of Tianshan Mountains in the 1970 s, mainly mass in the north of Tianshan Mountains in the 1980 s, mainly mass in the Tianshan region in the 1990 s, mainly mass in the west of Hexi Corridor region from 2000 to 2013 year; extreme high temperature events mainly mass in the Hexi Corridor region in the 1960 s, mainly mass in the southern Xinjiang in the 1970 s, mainly mass in the northern Xinjiang and the south of Tianshan Mountains in the 1980 s, mainly mass in the south of Tianshan Mountains in the 1990 s, mainly mass in the southern of Xinjiang from 2000 to 2013 year; each era of extreme precipitation events are mainly mass in the northern of Xinjiang, the east areas of Hexi Corridor and the west of Helan Mountains, the era of mass change is not large.8) Correlation analysis of extreme temperature and extreme precipitation indices show that extreme low temperature and extreme precipitation indices have an essentially negative correlation(except cool days and extreme precipitation indices which have a litter positive correlation), extreme high temperature have a positive correlation with the extreme precipitation indices, indicate the extreme low temperature events are rise while the extreme precipitation events are fall; extreme high temperature events are rise and the extreme precipitation events are also rise. Frost days and very wet days have the biggest negative correlation, warm nights and very wet days have the biggest positive correlation, the frost days and the warm nights are the indices which reflect the change of daily minimum temperature, indicate that the daily minimum temperature rise is the main reason for average temperature rise, and lead to precipitation increase.
Keywords/Search Tags:extreme climate indices, inter-annual variability, trend forecasting, spatial distribution, era of mass
PDF Full Text Request
Related items