Regional Difference Analysis of Climate Change in Gansu Province in Recent 58 Years and Its Impact on Circulation

Abstract

According to the grid point data of precipitation， average temperature， maximum and minimum temperature in Gansu Province from 1962 to 2019， combined with climate zoning， and using the methods of least squares， CEEMDAN analysis， cross wavelet transforms， wavelet coherence and Hurst Index， etc.， analysis of regional differences in climate change and circulation effects in Gansu over the past 58 years. The results showed that： （1） The linear trend analysis shows that the climate of Gansu has been warming and wetting in recent 58 years， and the warming trend is more significant than the precipitation increase trend.Spatial analysis shows that climate change varies greatly in different regions of Gansu province in the past 58 years， with the exception of the Hexi region， the precipitation in other regions shows a decreasing trend.Gannan’s cold and humid regions experienced the largest decreases in precipitation and the largest increases in temperature.（2） According to CEEMDAN analysis， the period of precipitation increase is about 9 years and the period of precipitation decrease is about 12 years in Gansu province.The average temperature rises and fall cycle is about 7 years.The cycle of maximum temperature increase is about 7 years， and the cycle of decrease is about 9 years.The rising cycle of minimum temperature is about 7 years， and the decreasing cycle is about 5 years.Overall， the change of temperature in Gansu province is about 15 years earlier than that of precipitation.The lowest temperature change is the earliest， and it began to increase obviously from 1962， and the precipitation change is the latest and began to increase obviously from 1992.（3） The Hurst index analysis shows that the climate change in each region has a strong continuity， and the future climate change trend in Gansu Province will be roughly consistent with that in 1962 -2019.（4） By monitoring the relationship between the Nino3.4 index and regional climate change in Gansu， the mean annual precipitation and ENSO events in the subtropical humid region of the southern Southern Gansu River Valley， the warm temperate humid region of the northern Southern Gansu Valley， the temperate and semi-humid region of the southern Gansu， and the temperate and semi-arid region of the northern Gansu are all negatively correlated with each other， the negative correlation coefficients were -0.29， -0.27， -0.29 and -0.3， respectively， which passed the reliability test of 0.05.The highest temperature in the temperate semi-arid region of northern Gansu was positively correlated with ENSO events， and the positive correlation coefficient was 0.28， and passed the reliability test of 0.05.（5） Cross wavelet transforms and wavelet coherence analysis show that the cooperative variation relationship between ENSO and rainfall in the temperate sub-humid zone in the southern part of Central Gansu and the temperate semi-arid zone in the northern part of Central Gansu has high consistency.

Keywords

• climate change
• ceemdan
• cross wavelet transform method
• wavelet coherence method