2004 Vol. 10, No. 1
2004, 10(1): 1-13.
Abstract:
The relationship between the ENSO and abnormal variation of precipitation and temperature in China is investigated based on the monthly data. Firstly, interannual variability of precipitation and temperature are discussed in different sub-areas using Rotational EOF (REOF). Then, the variation of precipitation and temperature in different phases of ENSO cycle is each investigated with Complex Singular Value Decomposition (CSVD). Results show that, during the period of El Niño, precipitation in the eastern China, especially in the northeastern China and Yangtze River valley, is much more than normal and is apt to flood. Precipitation in northern China and Huanghe River valley, especially in the middle reach of Huanghe River, is less than normal and is apt to be less. Precipitation in the Yangtze River valley is closely related to the SSTA in the central and eastern tropical Pacific on the QFO scale, and the precipitation variation lags behind SSTA by about 3 months. For the variation of surface temperature, during the period of El Niño, it is usually colder than normal in northeastern China, and in other regions, especially in the region of Great Bend of the Yellow River and southwestern China, is warmer than normal. The temperature in northeast China is closely associated with SSTA in eastern Pacific on the QFO scale and the surface temperature variation in the northeast China lags behind that of SSTA about 2 months.
The relationship between the ENSO and abnormal variation of precipitation and temperature in China is investigated based on the monthly data. Firstly, interannual variability of precipitation and temperature are discussed in different sub-areas using Rotational EOF (REOF). Then, the variation of precipitation and temperature in different phases of ENSO cycle is each investigated with Complex Singular Value Decomposition (CSVD). Results show that, during the period of El Niño, precipitation in the eastern China, especially in the northeastern China and Yangtze River valley, is much more than normal and is apt to flood. Precipitation in northern China and Huanghe River valley, especially in the middle reach of Huanghe River, is less than normal and is apt to be less. Precipitation in the Yangtze River valley is closely related to the SSTA in the central and eastern tropical Pacific on the QFO scale, and the precipitation variation lags behind SSTA by about 3 months. For the variation of surface temperature, during the period of El Niño, it is usually colder than normal in northeastern China, and in other regions, especially in the region of Great Bend of the Yellow River and southwestern China, is warmer than normal. The temperature in northeast China is closely associated with SSTA in eastern Pacific on the QFO scale and the surface temperature variation in the northeast China lags behind that of SSTA about 2 months.
2004, 10(1): 14-22.
Abstract:
The interdecadal variability of the East Asia summer monsoon during 1951～1999 is analyzed by using two different East Asia monsoon indices. The results agree on the point that the East Asia monsoon has undergone an interdecadal variability in the mid-1970’s. The intensity of the East Asia monsoon is weaker after this transition. Moreover the intensity and location of subtropical high that is an important component in East Asia monsoon system also shows interdecadal variation obviously. It is the interdecadal variation in atmospheric circulation that causes the drought over North China and flooding along the middle and lower reaches of the Yangtze River after the mid-1970’s.
The interdecadal variability of the East Asia summer monsoon during 1951～1999 is analyzed by using two different East Asia monsoon indices. The results agree on the point that the East Asia monsoon has undergone an interdecadal variability in the mid-1970’s. The intensity of the East Asia monsoon is weaker after this transition. Moreover the intensity and location of subtropical high that is an important component in East Asia monsoon system also shows interdecadal variation obviously. It is the interdecadal variation in atmospheric circulation that causes the drought over North China and flooding along the middle and lower reaches of the Yangtze River after the mid-1970’s.
2004, 10(1): 23-33.
Abstract:
Based on the data of NCEP, OLR and rainfall of China, we studied the influences of the East Asian winter monsoon activities on the precipitation during the raining season over China by correlation analysis and composite analysis. The result shows that annual and interdecadal change of East Asian winter monsoon is distinct. It is strong from 1950s to the middle of 1980s but weak after the middle of 1980s. The effect of abnormal winter monsoon on the precipitation during raining season is significant over the middle and lower reaches of the Changjiang River basin. It is revealed that the precipitation will increase when preceding winter monsoon is weak but decrease when preceding winter monsoon is strong. In this paper, some appropriate reasons are given to explain the abnormal rainfall by analyzing the distribution of SSTA and the variation of summer circulation. It is pointed out definitely that the variation of SSTA and summer circulation is a primary cause for abnormal rainfall over the middle and lower reaches of the Changjiang River.
Based on the data of NCEP, OLR and rainfall of China, we studied the influences of the East Asian winter monsoon activities on the precipitation during the raining season over China by correlation analysis and composite analysis. The result shows that annual and interdecadal change of East Asian winter monsoon is distinct. It is strong from 1950s to the middle of 1980s but weak after the middle of 1980s. The effect of abnormal winter monsoon on the precipitation during raining season is significant over the middle and lower reaches of the Changjiang River basin. It is revealed that the precipitation will increase when preceding winter monsoon is weak but decrease when preceding winter monsoon is strong. In this paper, some appropriate reasons are given to explain the abnormal rainfall by analyzing the distribution of SSTA and the variation of summer circulation. It is pointed out definitely that the variation of SSTA and summer circulation is a primary cause for abnormal rainfall over the middle and lower reaches of the Changjiang River.
2004, 10(1): 34-42.
Abstract:
Based on the wavelet packet decomposition/reconstruction method and the NCEP/NCAR daily reanalysis data set, the relation between the south Asian summer monsoon and the west Pacific subtropical high seasonal variation was discussed, and a corresponding summer monsoon frequency-band energy criterion was defined and introduced for diagnosing the west Pacific subtropical high. Besides, some existing characteristics and rules about the west Pacific subtropical high were further argued and proofed, a few new phenomena and correlation between the south Asian summer monsoon and the west Pacific subtropical high were also revealed and presented.
Based on the wavelet packet decomposition/reconstruction method and the NCEP/NCAR daily reanalysis data set, the relation between the south Asian summer monsoon and the west Pacific subtropical high seasonal variation was discussed, and a corresponding summer monsoon frequency-band energy criterion was defined and introduced for diagnosing the west Pacific subtropical high. Besides, some existing characteristics and rules about the west Pacific subtropical high were further argued and proofed, a few new phenomena and correlation between the south Asian summer monsoon and the west Pacific subtropical high were also revealed and presented.
2004, 10(1): 43-52.
Abstract:
Based on the NCEP/NCAR reanalysis global SST, 500-hPa geopotential height, 850-hPa wind monthly mean data and summer precipitation from 80 observation stations of Northeast China for the period 1961-2000, the summer precipitation field of Northeast China was decomposed by using the principal component analysis method, then the relationships between the first three precipitation leading modes and the global SSTA in preceding seasons were studied, and the responses of the 500-hPa atmospheric circulation in East Asia to the preceding winter SSTA in north Pacific and its influence on the summer precipitation in Northeast China were probed. The results show that the SSTA, especially the ENSO event in preceding seasons has really very important influence on the occurrence of the whole coincident precipitation episode in Northeast China, and relates to the precipitation episodes of the reverse variation in south-north and in west-east direction closely. The north Pacific SST anomalies in preceding winters are associated with the summer precipitation in Northeast China through its influence on the western Pacific subtropical high and the East Asia subtropical monsoon in summer. Therefore, taking the global SSTA distribution in preceding seasons, especially the ENSO event, as the precursor signal to predict the precipitation anomaly in Northeast China has good reliability and definite indicative significance.
Based on the NCEP/NCAR reanalysis global SST, 500-hPa geopotential height, 850-hPa wind monthly mean data and summer precipitation from 80 observation stations of Northeast China for the period 1961-2000, the summer precipitation field of Northeast China was decomposed by using the principal component analysis method, then the relationships between the first three precipitation leading modes and the global SSTA in preceding seasons were studied, and the responses of the 500-hPa atmospheric circulation in East Asia to the preceding winter SSTA in north Pacific and its influence on the summer precipitation in Northeast China were probed. The results show that the SSTA, especially the ENSO event in preceding seasons has really very important influence on the occurrence of the whole coincident precipitation episode in Northeast China, and relates to the precipitation episodes of the reverse variation in south-north and in west-east direction closely. The north Pacific SST anomalies in preceding winters are associated with the summer precipitation in Northeast China through its influence on the western Pacific subtropical high and the East Asia subtropical monsoon in summer. Therefore, taking the global SSTA distribution in preceding seasons, especially the ENSO event, as the precursor signal to predict the precipitation anomaly in Northeast China has good reliability and definite indicative significance.
2004, 10(1): 53-68.
Abstract:
On the basis of multi-taper spectral analysis, the work not only has examined and reformed monthly mean temperature time series of the Northern Hemisphere (NH) and Southern Hemisphere (SH) from 1856 to 1998, but also has systematically contrasted the differences of interdecadal oscillation (IDO) between the hemispheres, ocean-land surface in different seasons, with special analysis of IDO signals effects on global warming. The results show that the warming trend plays a dominant role in hemispheric mean temperature variability during the last 150 years. However, there are significant IDO with periods of about 40, 60 –C 70 years superimposed on a linear warming trend for NH mean temperature which leads to the reduction of the linear warming rate in terms of its significance and stability, as opposed to that in the SH, especially in summer. Moreover, in comparison of land to sea surface temperature, IDO signals detected in the latter are found to be more remarkable than those in the former, as contrasted to the linear warming rate. It has been noticed that IDO shows its peak value in the middle 1990s and begins to descend recently, a fact that probably affects the coming warming rate of NH mean temperature. Meanwhile, In terms of the GCM results from the HadCM2 model, preliminary analysis implies that the IDO may be the inherent oscillation of the ocean and atmosphere system, but warming trends are not related to natural variability.
On the basis of multi-taper spectral analysis, the work not only has examined and reformed monthly mean temperature time series of the Northern Hemisphere (NH) and Southern Hemisphere (SH) from 1856 to 1998, but also has systematically contrasted the differences of interdecadal oscillation (IDO) between the hemispheres, ocean-land surface in different seasons, with special analysis of IDO signals effects on global warming. The results show that the warming trend plays a dominant role in hemispheric mean temperature variability during the last 150 years. However, there are significant IDO with periods of about 40, 60 –C 70 years superimposed on a linear warming trend for NH mean temperature which leads to the reduction of the linear warming rate in terms of its significance and stability, as opposed to that in the SH, especially in summer. Moreover, in comparison of land to sea surface temperature, IDO signals detected in the latter are found to be more remarkable than those in the former, as contrasted to the linear warming rate. It has been noticed that IDO shows its peak value in the middle 1990s and begins to descend recently, a fact that probably affects the coming warming rate of NH mean temperature. Meanwhile, In terms of the GCM results from the HadCM2 model, preliminary analysis implies that the IDO may be the inherent oscillation of the ocean and atmosphere system, but warming trends are not related to natural variability.
2004, 10(1): 69-78.
Abstract:
The temperature change trends in January and July are analyzed and the results show that the trends descend in July but ascend in January except in South China and Southwest China. The relation between the temperature in January and July are discussed by using the wavelet. The results show that the trend phase in July and January are nearly in-phase in Southwest and South China, but are out-of-phase in other regions. Reconstruction of original temperature series in each of the regions indicates that their change trends are consistent with the original temperature series
The temperature change trends in January and July are analyzed and the results show that the trends descend in July but ascend in January except in South China and Southwest China. The relation between the temperature in January and July are discussed by using the wavelet. The results show that the trend phase in July and January are nearly in-phase in Southwest and South China, but are out-of-phase in other regions. Reconstruction of original temperature series in each of the regions indicates that their change trends are consistent with the original temperature series
2004, 10(1): 79-86.
Abstract:
With the 500-hPa geopotential height / SST fields and polar ice from NCEP/NCAR reanalysis source, the work discusses the relationship between abnormal motion of tropical cyclones making landfall on Guangdong province and governing factors like general circulation, polar ice, SST and circulation indexes. It determines how the years of more or fewer tropical cyclones (TCs) distribute for the general circulation, polar ice, SST, conceptual models of all circulation indexes. The results show that (1) when the middle and higher latitudes of the Eurasian continent are mainly of meridional (zonal) circulation in autumn and winter, there are more (fewer) landfalls of TCs; (2) when the SST is warm (cold) in the equatorial eastern Pacific in January –C April, there are fewer (more) TCs landfall in the province in the current year but more (fewer) landfall the following year, indicating stable and obvious influence of the former on TCs; (3) when there are more (less) polar ice in summer, autumn and winter, or consistently more (less) ice in autumn and winter, there are mostly fewer (more) landfalls than usual.
With the 500-hPa geopotential height / SST fields and polar ice from NCEP/NCAR reanalysis source, the work discusses the relationship between abnormal motion of tropical cyclones making landfall on Guangdong province and governing factors like general circulation, polar ice, SST and circulation indexes. It determines how the years of more or fewer tropical cyclones (TCs) distribute for the general circulation, polar ice, SST, conceptual models of all circulation indexes. The results show that (1) when the middle and higher latitudes of the Eurasian continent are mainly of meridional (zonal) circulation in autumn and winter, there are more (fewer) landfalls of TCs; (2) when the SST is warm (cold) in the equatorial eastern Pacific in January –C April, there are fewer (more) TCs landfall in the province in the current year but more (fewer) landfall the following year, indicating stable and obvious influence of the former on TCs; (3) when there are more (less) polar ice in summer, autumn and winter, or consistently more (less) ice in autumn and winter, there are mostly fewer (more) landfalls than usual.
2004, 10(1): 87-94.
Abstract:
By making full use of GMS TBB data, diagnosis and analysis of the formation and development of El Nino event in 2002 and 2003 were made. It suggests that the first clue of the El Nino event appeared in December 2001. The event was formed at the end of 2002 after five phases of development, and came into the phase of flourishing in the winter of 2002. From the analysis the dynamics, it is noted that that the position of the ascending branch of Walker cell was moving from the equatorial west Pacific to the equatorial central Pacific in the phase of formation and development of the El Nino event. The process of diagnosis shows that it can provide an important clue for forecasting the genesis and development of the El Nino episodes.
By making full use of GMS TBB data, diagnosis and analysis of the formation and development of El Nino event in 2002 and 2003 were made. It suggests that the first clue of the El Nino event appeared in December 2001. The event was formed at the end of 2002 after five phases of development, and came into the phase of flourishing in the winter of 2002. From the analysis the dynamics, it is noted that that the position of the ascending branch of Walker cell was moving from the equatorial west Pacific to the equatorial central Pacific in the phase of formation and development of the El Nino event. The process of diagnosis shows that it can provide an important clue for forecasting the genesis and development of the El Nino episodes.
2004, 10(1): 95-105.
Abstract:
This paper analyzes the samples of rainwater from January to October 1999 at three monitoring sites of Baiyun Mountain and of aerosol composition in near-surface layer in January and June 1999 at two sites. The results suggest that (1) The pH value of rainwater is between 3.13 and 7.18, and the frequency of acid rain is more than 58 %. With the ascent of the monitoring sites, the pH value of rainwater decreases, and the frequency of acid rain increases. (2) In January, the chemical aerosol compositions at different altitudes are similar, but in June the acidity of aerosol rises at the higher site because of the increase of SO2-4. (3) In rainwater, the proportion is such that SO2-4 is the most significant anion and Ca2+ is the most important cation, but both of them decrease as the altitude ascends. The proportion of NO3- and NH4+ rise at the higher site and have more contribution to the acidity of rainwater. (4) As the impact of automobile emissions around Baiyun Mountain, the proportion of NO3-/SO2-4 molecular concentration reaches 0.40, and NO3 - is relatively more important to the rain acidity at the higher site.
This paper analyzes the samples of rainwater from January to October 1999 at three monitoring sites of Baiyun Mountain and of aerosol composition in near-surface layer in January and June 1999 at two sites. The results suggest that (1) The pH value of rainwater is between 3.13 and 7.18, and the frequency of acid rain is more than 58 %. With the ascent of the monitoring sites, the pH value of rainwater decreases, and the frequency of acid rain increases. (2) In January, the chemical aerosol compositions at different altitudes are similar, but in June the acidity of aerosol rises at the higher site because of the increase of SO2-4. (3) In rainwater, the proportion is such that SO2-4 is the most significant anion and Ca2+ is the most important cation, but both of them decrease as the altitude ascends. The proportion of NO3- and NH4+ rise at the higher site and have more contribution to the acidity of rainwater. (4) As the impact of automobile emissions around Baiyun Mountain, the proportion of NO3-/SO2-4 molecular concentration reaches 0.40, and NO3 - is relatively more important to the rain acidity at the higher site.
2004, 10(1): 106-112.
Abstract:
In designing the human comfort index (CI) used in Guangzhou, a Gaussian curve was adopted as the fundamental profile to develop a “straw hat” model of comfort index. The model projects low or high temperatures into low index values and the moderate temperatures into high index values. Air temperature was chosen as a basic factor in the model. Other factors such as humidity, sunshine and wind speed were introduced by considering them as temperature departures to an equivalent apparent temperature (EAT). Since the index is a relative index, 25°C was chosen as an ideal apparent temperature (the most comfortable state) and a maximum CI value of 100 was assigned at this temperature. While in other circumstances, the index would be lower than 100. By utilizing this model, the daily comfort index values had been calculated for Guangzhou city for 1998-1999, using mean temperature, mean humidity, mean wind speed and total hours of sunshine. Results show that the new model was reasonable and practicable. Not only could it reflect the monthly variation of human comfort in Guangzhou, but also was sensitive to short-term changes of weather conditions.
In designing the human comfort index (CI) used in Guangzhou, a Gaussian curve was adopted as the fundamental profile to develop a “straw hat” model of comfort index. The model projects low or high temperatures into low index values and the moderate temperatures into high index values. Air temperature was chosen as a basic factor in the model. Other factors such as humidity, sunshine and wind speed were introduced by considering them as temperature departures to an equivalent apparent temperature (EAT). Since the index is a relative index, 25°C was chosen as an ideal apparent temperature (the most comfortable state) and a maximum CI value of 100 was assigned at this temperature. While in other circumstances, the index would be lower than 100. By utilizing this model, the daily comfort index values had been calculated for Guangzhou city for 1998-1999, using mean temperature, mean humidity, mean wind speed and total hours of sunshine. Results show that the new model was reasonable and practicable. Not only could it reflect the monthly variation of human comfort in Guangzhou, but also was sensitive to short-term changes of weather conditions.
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