The Characteristics of Climate Change over the Tibetan Plateau in the Last 40 Years and the Detection of Climatic Jumps

Through analyzing the yearly average data obtained from 123 regular meteorological observatories located in the Tibetan Plateau (T-P), this article studies the characteristics of climate change in T-P in the last 40 years. Prom the distribution of the linear trend, it can be concluded that the southeastern part of T-P becomes warmer and wetter, with an obvious increase of rainfall. The same characteristics are found in the southwestern part of T-P, but the shift is smaller. In the middle of T-P, temperature and humidity obviously increase with the center of the increase in Bangoin-Amdo. The south of the Tarim Basin also exhibits the same tendency. The reason for this area being humid is that it gets less sunshine and milder wind. The northeastern part of T-P turns warmer and drier. Qaidam Basin and its western and southern areas are the center of this shift, in which the living environment is deteriorating. Analyzing the characteristics of the regional average time series, it can be found that in the mid-1970s, a significant sudden change occurred to annual rainfall, yearly average snow-accumulation days and surface pressure in the eastern part of T-P. In the mid-1980s, another evident climatic jump happened to yearly average temperature, total cloud amount, surface pressure, relative humidity, and sunshine duration in the same area. That is, in the mid 1980s, the plateau experienced a climatic jump that is featured by the increase of temperature, snow-accumulation days, relative humidity, surface pressure, and by the decrease of sunshine duration and total cloud amount. The sudden climatic change of temperature in T-P is later than that of the global-mean temperature. Prom this paper it can be seen that in the middle of the 1980s, a climatic jump from warm-dry to warm-wet occurred in T-P.

The Effect of Climatic Jump on the Agricultural Production in Shenyang

Using conventional mathematical statistics,linear regression and the standard deviation,the quantitative analysis was made on the climate changes in Shenyang.The results showed that the trend of precipitation reduced 155 mm,which was made the greatest contribution by summer and autumn.It decreased 43 mm on the average after the climate jump.The precipitation variability in spring increased and drought risk in spring increased.The first soaking rain limited the spring planting time.The temperature trend raised 1.3℃,mainly in spring and winter.The frost-free period extended about 13 d.The accumulated temperature trends in crop growing season increased 290℃ and it had an average increase of 178℃ after the climate jump.This trend of climate warming made the end of last frost advanced.Early sowing of crops suitably was possible,which was beneficial for agricultural production.The precipitation decrease,the time delay and instability of the first soaking rain were unfavorable for crop growth and seeding.And they became the factors that constrained the normal growth and stabile yield raise of crops.

The Response of Climatic Jump in Summer in North China to Global Warming

To reveal climatic variation over North China, the climatic jumps in summer in Beijing are analyzed using the data of precipitation of summer (June, July, August) during the period of 1841-1993, in which those missed before 1950 were reconstructed by the stepwise regression method with minimum forecast error. The climatic jumps at different scales are analyzed using different diagnostic methods with different decade (10-100 years) windows. Some new methods and ideas are proposed. The variance difference, the linear tendency difference, and the difference of power spectral distribution between the samples before and after the period at the moving point in the center of the series are compared with other methods (for example, Mann—Kendall test, t— test, and accumulative anomaly etc.). Considering the differences among the statistics above, a synthetic jump index is also proposed in order to get the definite jump points in the moving series. The results show that the climatic jumps in the area occurred in the 1890s, the 1910s and the 1920s, and mostly in the 1920s, which suggests that the local climatic jumps in North China have a simultaneous response to the global warming in the hundred-year scales. Key words Climatic jump - New diagnostic statistics - Synthetic jump index - Response to global warming This Study was supported by the “ National Key Programme for Developing Basic Sciences” G1998040901-1.

THE CLIMATIC JUMP OF THE WESTERN PACIFIC WARM POOL AND ITS CLIMATIC EFFECTS

The climatic jump of the western Pacific warm pool and its climatic effects were analyzed using the SST (COADS, NCEP) datasets. The results show that the warm pool has significant interdecadal variability with periods of 10 to 20 years and four major climatic jumps with periods of 40 to 50 years for a time dating back for more than 100 years, which happened in the 1910s, 1930s, 1950s and 1980抯. The warm pool jumps have important climatic effects. After the jumps,the SST increases by about 0.5C in central and eastern tropical Pacific; the Pacific subtropical high at 500 hPa strengthens and goes southwestward, the precipitation bands tend to be in southern China. The results also show that El Ni駉 event will happen more often than the La Ni馻 event when the warm pool anomalously develops, and the La Ni馻 event will happen more often than the El Ni駉 event when the warm pool anomalously declines. Over the recent 40-to-50 year period,the warm pool is still in its strengthening stage and it is possible that the drought in northern China will continue in the first decade of 21st century.

CLIMATIC JUMP FROM LATE 1970S TO EARLY 1980S AND ITS EFFECT

By use of the moving T test to do research on the interdecadal climate jump of the Northern Hemisphere sea level pressure.500 hPa height and North Pacific sea surface temperature,we found that in recent 50 years an obvious interdecadal climate jump existed at the late 1970s to the early 1980s.There is significant difference before and after the jump in terms of the Northern Hemisphere sea level pressure,500 hPa height and North Pacific sea surface temperature. Furthermore,the focus is then placed on the effect of the jump on temperature and rainfall in China.

The NPO/ NAO and Interdecadal Climate Variation in China

This article discusses the interannual variation of the North Atlantic Oscillation (NAO) and North Pacific Oscillation (NPO), its relationship with the interdecadal climate variation in China which is associated with the climate jump in the Northern Hemisphere in the 1960’s, using the data analyses. It is clearly shown that both the amplitudes of the NAO and NPO increase obviously in the 1960’s and the main period of the oscillations changes from 3-4 years before the 1960’s to 8–15 years after the 1960’s. Therefore, interdecadal climate variation in China or the climate jump in the 1960’s is closely related to the anomalies of the NAO and NPO. Key words North Atlantic Oscillation (NAO) - North Pacific Oscillation (NPO) - Climate Jump - Interdecadal climate variation This work was supported by National Key Basic Science Program in China (G1998040903), Chinese Academy of Science and the National Natural Science Fundation of China (Grant No.49823002).The authors are also grateful to Ms. Wang Xuan for typing the manuscript.

Climate change in the Sanjiang Plain disturbed by large-scale reclamation

Up to 1949, wetlands stretched continuously and accounted for 80.17% of the total area of plain part of the Sanjiang Plain. However, wetlands in the plain have gone through 4 periods (1956–1960, 1960–1977, 1980–1986, 1986-the present) of large-scale reclamation from 1956 to the present. Over 50% wetlands had changed into agricultural fields. The underlying surface of the plain has changed tremendously. This study investigated the regional climate change by analyzing regional climatic variation and tendency and examining climate jumps over the last 45 years. Monthly records of 5 climatic factors (air temperature, precipitation, atmospheric pressure, sunshine time and wind speed) for 26 meteorological stations covering the period 1955–1999 were used. The annual mean temperature of the study region was tending to go up and increased by 1.2–2.3 °C during the last 45 years. The maximum of annual precipitation decrease in the region was 90 mm over the last 45 years. An abrupt warming of the annual mean temperature occurred in the mid-1980s, which had an increase amplitude of 0.9 °C. Of increase amplitudes of all the seasonal abrupt warming, the largest one was 1.8 °C in the winter since 1987. The plain used to be cold and humid with center of Heilongjiang province even till the late 1960s, for it had an underlying surface of wetlands in the main. However, based on the facts of the climate changes of the plain over the last 45 years, it is held that the plain had a larger warming amplitude than that of area around it in recent years probably resulted from the large-scale reclamation of various kinds of wetlands.

MULTI-SCALE ANALYSES OF SURFACE AIR TEMPERATURE VARIATIONS FOR THE NORTHERN HEMISPHERE AND CHINA DURING THE LAST ONE HUNDRED YEARS

Using multi-resolution theory of wavelet analysis,this paper studies the multi-scale structure of surface air temperature variations for the Northern Hemisphere and China during the last one hundred years.The results show that the climatic variations for the Northern Hemisphere can be described as 3 hierarchies corresponding to the larger-scale changes.They are the cold period be- fore 1919,the warm period from 1920 to 1978 and the warmer period after 1979.The larger-scale hierarchical changes obviously show qualities of climate jump.The years 1920 and 1979 are the jump points of climate change.The surface air temperature variations for China are not entirely analogous to the Northern Hemisphere,and the main contrasts are that China is in the cold period after 1955 and the jump point of warming is 1987.The surface air temperature variations for the Northern Hemisphere and China during the last one hundred years obviously show the hierarchical structure of multi-scale changes and the qualities of climate jump.