Based on a series of data analyses, the intimate relations between anomalous winter monsoon in East Asia and El Nino arc studied in this paper.Anomalistic circulation in the Northern Hemisphere caused by El Nino event...Based on a series of data analyses, the intimate relations between anomalous winter monsoon in East Asia and El Nino arc studied in this paper.Anomalistic circulation in the Northern Hemisphere caused by El Nino event can lead to enhancing the Ferre! cell and the westerlies in the mid-latitudes as the Hadley cell and result in the location of the front zone in East Asia to the north. These are unfavourable for the cold wave breaking out southward in East Asia. Therefore, there ate warmer weather and weaker winter monsoon in East Asia in El Nino winter.There are stronger and frequent cold waves in East Asia during the wintertime prior to the occurrence of El Nino event. They will induce stronger winter monsoon in East Asia. Thus, the weakened trade wind and enhanced cumulus convection in the equatorial middle-western Pacific area caused by the stronger winter monsoon will play an important role in the occurrence of El Nino event. Therefore, the anomalously strong winter monsoon in East Asia during wintertime might be an important mechanism to cause El Nino event.展开更多
A nonlinear reaction diffusion equations for activator inhibitor systems is considered. Under suitable conditions, firstly, the outer solution of the original problem is obtained, secondly, using the variables of mult...A nonlinear reaction diffusion equations for activator inhibitor systems is considered. Under suitable conditions, firstly, the outer solution of the original problem is obtained, secondly, using the variables of multiple scales and the expanding theory of power series the formal asymptotic expansions of the solution are constructed, and finally, using the theory of differential inequalities the uniform validity and asymptotic behavior of the solution are studied.展开更多
Based on the EAP (East Asia/Pacific) teleconnection in the summer circulation anomalies over the Northern Hemisphere, an index measuring the strength of the East Asian summer monsoon, i.e., the so-called EAP index, is...Based on the EAP (East Asia/Pacific) teleconnection in the summer circulation anomalies over the Northern Hemisphere, an index measuring the strength of the East Asian summer monsoon, i.e., the so-called EAP index, is defined in this paper. From the analyses of observed data, it is clearly shown that the EAP index defined in this study can well describe the interannual variability of summer rainfall and surface air temperature in East Asia, especially in the Yangtze River valley and the Huaihe River valley, Korea, and Japan. Moreover, this index can also reflect the interannual variability of the East Asian summer monsoon system including the monsoon horizontal circulation and the vertical-meridional circulation cell over East Asia. From the composite analyses of climate and monsoon circulation anomalies for high EAP index and for low EAP index, respectively, it is well demonstrated that the EAP index proposed in this study can well measure the strength of the East Asian summer monsoon.展开更多
A new North Atlantic Oscillation (NAO) index, the NAOI, is defined as the differences of normalized sea level pressures regionally zonal-averaged over a broad range of longitudes 80°W-30°E. A comprehensive c...A new North Atlantic Oscillation (NAO) index, the NAOI, is defined as the differences of normalized sea level pressures regionally zonal-averaged over a broad range of longitudes 80°W-30°E. A comprehensive comparison of six NAO indices indicates that the new NAOI provides a more faithful representation of the spatial-temporal variability associated with the NAO on all timescales. A very high signal-to-noise ratio for the NAOI exists for all seasons, and the life cycle represented by the NAOI describes well the seasonal migration for action centers of the NAO. The NAOI captures a larger fraction of the variance of sea level pressure over the North Atlantic sector (20°-90°N, 80°W-30°E), on average 10% more than any other NAO index. There are quite different relationships between the NAOI and surface air temperature during winter and summer. A novel feature, however, is that the NAOI is significantly negative correlated with surface air temperature over the North Atlantic Ocean between 10°-25°N and 70°-30°W, whether in winter or summer. From 1873, the NAOI exhibits strong interannual and decadal variability. Its interannual variability of the twelve calendar months is obviously phase-locked with the seasonal cycle. Moreover, the annual NAOI exhibits a clearer decadal variability in amplitude than the winter NAOI. An upward trend is found in the annual NAOI between the 1870s and 1910s, while the other winter NAO indices fail to show this tendency. The annual NAOI exhibits a strongly positive epoch of 50 years between 1896 and 1950. After 1950, the variability of the annual NAOI is very similar to that of the winter NAO indices.展开更多
Based on the reanalysis data fromNCEP/NCAR and other observational data, interannualvariability of Mascarene high (MH) and Australian high (AH) from 1970 to 1999 is examined. It is shown that interannual variability o...Based on the reanalysis data fromNCEP/NCAR and other observational data, interannualvariability of Mascarene high (MH) and Australian high (AH) from 1970 to 1999 is examined. It is shown that interannual variability of MH is dominated by the Antarctic oscillation (AAO), when the circumpolar low in the high southern lati-tudes deepens, the intensity of MH will be intensified. On the other hand, AH is correlated by AAO as well as El Nio and South Oscillation (ENSO), the intensity of AH will be inten-sified when El Nio occurs. Both correlation analysis andcase study demonstrate that summer rainfall over East Asia is closely related to MH and AH. When MH intensifies from boreal spring to summer (i.e. from austral autumn to winter)there is more rainfall over regions from the Yangtze Rivervalley to Japan, in contrast, less rainfall is found over south-ern China and western Pacific to the east of Taiwan, andmost of regions in mid-latitudes of East Asia. Compared with MH, the effect of AH on summer rainfall in East Asia is lim-ited to localized regions, there is more rainfall over southern China with the intensification of AH. The results in this study show that AAO is a strong signal on interannual time-scale, which plays an important role in summer rainfall over East Asia. This discovery is of real importance to revealing the physical mechanism of interannual variability of EastAsian summer monsoon and prediction of summer precipi-tation in China.展开更多
This paper proposes a new two-step non-oscillatory shape-preserving positive definite finite difference advection transport scheme, which merges the advantages of small dispersion error in the simple first-order upst... This paper proposes a new two-step non-oscillatory shape-preserving positive definite finite difference advection transport scheme, which merges the advantages of small dispersion error in the simple first-order upstream scheme and small dissipation error in the simple second-order Lax-Wendroff scheme and is completely different from most of present positive definite advection schemes which are based on revising the upstream scheme results. The proposed scheme is much less time consuming than present shape-preserving or non-oscillatory advection transport schemes and produces results which are comparable to the results obtained from the present more complicated schemes. Elementary tests are also presented to examine the behavior of the scheme.展开更多
Coupled ocean-atmospheric general circulation models are the only tools to quantitatively simulate the climate system. Since the end of the 1980s, a group of scientists in the State Key Laboratory of Numerical Modelin...Coupled ocean-atmospheric general circulation models are the only tools to quantitatively simulate the climate system. Since the end of the 1980s, a group of scientists in the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS), have been working to develop a global OGCM and a global coupled ocean-atmosphere general circulation modei (CGCM). Prom the original flux anomaly-coupling modei developed in the beginning of the 1990s to the latest directly-coupling modei, LASG scientists have developed four global coupled GCMs. This study summarizes the development history of these models and describes the third and fourth coupled GCMs and selected applications. Strengths and weaknesses of these models are highlighted.展开更多
Conditional nonlinear optimal perturbation (CNOP),which is a natural extension of singular vector (SV) into the nonlinear regime,is applied to ensemble prediction study by using a quasi-geostrophic model under the per...Conditional nonlinear optimal perturbation (CNOP),which is a natural extension of singular vector (SV) into the nonlinear regime,is applied to ensemble prediction study by using a quasi-geostrophic model under the perfect model assumption. SVs and CNOPs have been utilized to generate the initial pertur-bations for ensemble prediction experiments. The results are compared for forecast lengths of up to 14 d. It is found that the forecast skill of samples,in which the first SV is replaced by CNOP,is com-paratively higher than that of samples composed of only SVs in the medium range (day 6―day 14). This conclusion is valid under the condition that analysis error is a kind of fast-growing ones regardless of its magnitude,whose nonlinear growth is faster than that of SV in the later part of the forecast. Fur-thermore,similarity index and empirical orthogonal function (EOF) analysis are performed to explain the above numerical results.展开更多
A novel concept of nonlinear singular vector and nonlinear singular value is introduced, which is a natural generalization of the classical linear singular vector and linear singular value to the nonlinear category. T...A novel concept of nonlinear singular vector and nonlinear singular value is introduced, which is a natural generalization of the classical linear singular vector and linear singular value to the nonlinear category. The optimization problem related to the determination of nonlinear singular vectors and singular values is formulated. The general idea of this approach is demonstrated by a simple two-dimensional quasigeostrophic model in the atmospheric and oceanic sciences. The advantage and its applications of the new method to the predictability, ensemble forecast and finite-time nonlinear instability are discussed. This paper makes a necessary preparation for further theoretical and numerical investigations.展开更多
The El Nifio-Southern Oscillation （ENSO） is an interannual phenomenon involved in the tropical Pacific Oceanatmosphere interactions. In this paper, an asymptotic method of solving the nonlinear equation for the ENSO...The El Nifio-Southern Oscillation （ENSO） is an interannual phenomenon involved in the tropical Pacific Oceanatmosphere interactions. In this paper, an asymptotic method of solving the nonlinear equation for the ENSO model is used. And based on a class of oscillator of ENSO model, the approximate solution of a corresponding problem is studied by employing the perturbation method. Firstly, an ENSO model of nonlinear time delay equation of equatorial Pacific is introduced, Secondly, by using the perturbed method, the zeroth and first order asymptotic perturbed solutions are constructed. Finally, from the comparison of the values for a figure, it is seen that the first asymptotic perturbed solution using the perturbation method has a good accuracy. And it is proved from the results that the perturbation method can be used as an analytic operation for the sea surface temperature anomaly in the equatorial Pacific of the atmosphere-ocean oscillation for the ENSO model.展开更多
This paper presents a methodology which is very useful to design shape-preserving advection finite difference scheme on general E-grid horizontal arrangement of variables through introducing a two-step shape-preservi... This paper presents a methodology which is very useful to design shape-preserving advection finite difference scheme on general E-grid horizontal arrangement of variables through introducing a two-step shape-preserving positive definite advection scheme in the moisture equation of the LASG-REM (LASG regional E-grid eta-coordinate forecast model). By trial-forecasting six local heavy raincases, the efficiency of the shape-preserving advection scheme in practical application has been examined. The LASG-REM with the shape-preserving advection scheme has a good forecasting ability for local precipitation.展开更多
A pair of northeast-southwest-tilted mid-tropospheric ridges and troughs on the continental scale was observed to be the key circulation feature common among wintertime extensive and persistent low tempera-ture events...A pair of northeast-southwest-tilted mid-tropospheric ridges and troughs on the continental scale was observed to be the key circulation feature common among wintertime extensive and persistent low tempera-ture events (EPLTE) in China.During the persistence of such anomalous circulations,the split flow over the inner Asian continent and the influent flow over the southeast-ern coast of China correspond well to the expanded and amplified Siberian high with tightened sea level pressure gradients and hence,a strong,cold advection over south-eastern China.The western Pacific subtropical high tends to expand northward during the early stages of most EPLTEs.展开更多
Using the relative vorticity averaged over a certain area, a new index for measuring the longitudinal position of the subtropical high (SH) in the western Pacific is proposed to avoid the increasing trend of heights i...Using the relative vorticity averaged over a certain area, a new index for measuring the longitudinal position of the subtropical high (SH) in the western Pacific is proposed to avoid the increasing trend of heights in the previous indices based on geopotential height. The years of extreme westward and eastward extension of SH using the new index are in good agreement with those defined by height index. There exists a distinct difference in large-scale circulation between the eastward and westward extension of SH under the new definition, which includes not only the circulation in the middle latitudes but also the flow in the lower latitudes. It seems that when the SH extends far to the east (west), the summer monsoon in the South China Sea is stronger (weaker) and established earlier (later). In addition, there exists a good relationship between the longitudinal position of SH and the summer rainfall in China. A remarkable negative correlation area appears in the Changjiang River valley, indicating that when the SH extends westward (eastward), the precipitation in that region increases (decreases). A positive correlation region is found in South China, showing the decrease of rainfall when the SH extends westward. On the other hand, the rainfall is heavier when the SH retreats eastward. However, the anomalous longitudinal position of SH is not significantly related to the precipitation in North China. The calculation of correlation coefficients between the index of longitudinal position of SH and surface temperature in China shows that a large area of positive values, higher than 0.6 in the center, covers the whole of North China, even extending eastward to the Korean Peninsula and Japan Islands when using NCEP/NCAR reanalysis data to do the correlation calculation. This means that when the longitudinal position of the SH withdraws eastward in summer, the temperature over North China is higher. On the other hand, when it moves westward, the temperature there is lower. This could explain the phenomenon of the ser展开更多
文摘Based on a series of data analyses, the intimate relations between anomalous winter monsoon in East Asia and El Nino arc studied in this paper.Anomalistic circulation in the Northern Hemisphere caused by El Nino event can lead to enhancing the Ferre! cell and the westerlies in the mid-latitudes as the Hadley cell and result in the location of the front zone in East Asia to the north. These are unfavourable for the cold wave breaking out southward in East Asia. Therefore, there ate warmer weather and weaker winter monsoon in East Asia in El Nino winter.There are stronger and frequent cold waves in East Asia during the wintertime prior to the occurrence of El Nino event. They will induce stronger winter monsoon in East Asia. Thus, the weakened trade wind and enhanced cumulus convection in the equatorial middle-western Pacific area caused by the stronger winter monsoon will play an important role in the occurrence of El Nino event. Therefore, the anomalously strong winter monsoon in East Asia during wintertime might be an important mechanism to cause El Nino event.
基金the National Natural Science Foundation of China under Grant Nos.40676016 and 10471039the National Key Project for Basics Research under Grant Nos.2003CB415101-03 and 2004CB418304+1 种基金the Key Project of the Chinese Academy of Sciences under Grant No.KZCX3-SW-221in part by E-Insitutes of Shanghai Municipal Education Commission under Grant No.E03004
文摘A nonlinear reaction diffusion equations for activator inhibitor systems is considered. Under suitable conditions, firstly, the outer solution of the original problem is obtained, secondly, using the variables of multiple scales and the expanding theory of power series the formal asymptotic expansions of the solution are constructed, and finally, using the theory of differential inequalities the uniform validity and asymptotic behavior of the solution are studied.
基金supported jointly by the National Key Basic Research Development Program(Grant No.G1999043403)the Knowledge Innovation Project of the Chinese Academy of Sciences(CAS)(Grant No.KZCX3-SW-218)+1 种基金the National Natural Science Foundation of China project for young scientists fund(No.40305012) the Western Project of the CAS (KZCX1-10-07).
文摘Based on the EAP (East Asia/Pacific) teleconnection in the summer circulation anomalies over the Northern Hemisphere, an index measuring the strength of the East Asian summer monsoon, i.e., the so-called EAP index, is defined in this paper. From the analyses of observed data, it is clearly shown that the EAP index defined in this study can well describe the interannual variability of summer rainfall and surface air temperature in East Asia, especially in the Yangtze River valley and the Huaihe River valley, Korea, and Japan. Moreover, this index can also reflect the interannual variability of the East Asian summer monsoon system including the monsoon horizontal circulation and the vertical-meridional circulation cell over East Asia. From the composite analyses of climate and monsoon circulation anomalies for high EAP index and for low EAP index, respectively, it is well demonstrated that the EAP index proposed in this study can well measure the strength of the East Asian summer monsoon.
基金supported jointly by the NOAA Arctic Research,CAS Project ZKCX2-SW-210the National Natural Science Foundation of China(Grant No.40275025)
文摘A new North Atlantic Oscillation (NAO) index, the NAOI, is defined as the differences of normalized sea level pressures regionally zonal-averaged over a broad range of longitudes 80°W-30°E. A comprehensive comparison of six NAO indices indicates that the new NAOI provides a more faithful representation of the spatial-temporal variability associated with the NAO on all timescales. A very high signal-to-noise ratio for the NAOI exists for all seasons, and the life cycle represented by the NAOI describes well the seasonal migration for action centers of the NAO. The NAOI captures a larger fraction of the variance of sea level pressure over the North Atlantic sector (20°-90°N, 80°W-30°E), on average 10% more than any other NAO index. There are quite different relationships between the NAOI and surface air temperature during winter and summer. A novel feature, however, is that the NAOI is significantly negative correlated with surface air temperature over the North Atlantic Ocean between 10°-25°N and 70°-30°W, whether in winter or summer. From 1873, the NAOI exhibits strong interannual and decadal variability. Its interannual variability of the twelve calendar months is obviously phase-locked with the seasonal cycle. Moreover, the annual NAOI exhibits a clearer decadal variability in amplitude than the winter NAOI. An upward trend is found in the annual NAOI between the 1870s and 1910s, while the other winter NAO indices fail to show this tendency. The annual NAOI exhibits a strongly positive epoch of 50 years between 1896 and 1950. After 1950, the variability of the annual NAOI is very similar to that of the winter NAO indices.
基金the National Key Basic Development Program (Grant No. G1998040900Part I) and the National Natural Science Foundation of China (Grant Nos. 40125014 and 40075020)
文摘Based on the reanalysis data fromNCEP/NCAR and other observational data, interannualvariability of Mascarene high (MH) and Australian high (AH) from 1970 to 1999 is examined. It is shown that interannual variability of MH is dominated by the Antarctic oscillation (AAO), when the circumpolar low in the high southern lati-tudes deepens, the intensity of MH will be intensified. On the other hand, AH is correlated by AAO as well as El Nio and South Oscillation (ENSO), the intensity of AH will be inten-sified when El Nio occurs. Both correlation analysis andcase study demonstrate that summer rainfall over East Asia is closely related to MH and AH. When MH intensifies from boreal spring to summer (i.e. from austral autumn to winter)there is more rainfall over regions from the Yangtze Rivervalley to Japan, in contrast, less rainfall is found over south-ern China and western Pacific to the east of Taiwan, andmost of regions in mid-latitudes of East Asia. Compared with MH, the effect of AH on summer rainfall in East Asia is lim-ited to localized regions, there is more rainfall over southern China with the intensification of AH. The results in this study show that AAO is a strong signal on interannual time-scale, which plays an important role in summer rainfall over East Asia. This discovery is of real importance to revealing the physical mechanism of interannual variability of EastAsian summer monsoon and prediction of summer precipi-tation in China.
基金This work is supported by the Ntional Natural Science Foundation of China.
文摘 This paper proposes a new two-step non-oscillatory shape-preserving positive definite finite difference advection transport scheme, which merges the advantages of small dispersion error in the simple first-order upstream scheme and small dissipation error in the simple second-order Lax-Wendroff scheme and is completely different from most of present positive definite advection schemes which are based on revising the upstream scheme results. The proposed scheme is much less time consuming than present shape-preserving or non-oscillatory advection transport schemes and produces results which are comparable to the results obtained from the present more complicated schemes. Elementary tests are also presented to examine the behavior of the scheme.
基金supported by the Chinese Academy of Sciences(CAS)“Innovation Program”(ZKCX2-SW-210)State Key Project(G2000078502)the National Natural Science Foundation of China(Nos.40231004,40221503,and 40023001).
文摘Coupled ocean-atmospheric general circulation models are the only tools to quantitatively simulate the climate system. Since the end of the 1980s, a group of scientists in the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS), have been working to develop a global OGCM and a global coupled ocean-atmosphere general circulation modei (CGCM). Prom the original flux anomaly-coupling modei developed in the beginning of the 1990s to the latest directly-coupling modei, LASG scientists have developed four global coupled GCMs. This study summarizes the development history of these models and describes the third and fourth coupled GCMs and selected applications. Strengths and weaknesses of these models are highlighted.
基金the State Key Development Program for Basic Research of China (Grant No.2006CB400503)the Chinese Academy of Sciences (Grant No.KZCX3-SW-230)the National Natural Science Foundation of China (Grant Nos.40221503 and 40675030)
文摘Conditional nonlinear optimal perturbation (CNOP),which is a natural extension of singular vector (SV) into the nonlinear regime,is applied to ensemble prediction study by using a quasi-geostrophic model under the perfect model assumption. SVs and CNOPs have been utilized to generate the initial pertur-bations for ensemble prediction experiments. The results are compared for forecast lengths of up to 14 d. It is found that the forecast skill of samples,in which the first SV is replaced by CNOP,is com-paratively higher than that of samples composed of only SVs in the medium range (day 6―day 14). This conclusion is valid under the condition that analysis error is a kind of fast-growing ones regardless of its magnitude,whose nonlinear growth is faster than that of SV in the later part of the forecast. Fur-thermore,similarity index and empirical orthogonal function (EOF) analysis are performed to explain the above numerical results.
文摘A novel concept of nonlinear singular vector and nonlinear singular value is introduced, which is a natural generalization of the classical linear singular vector and linear singular value to the nonlinear category. The optimization problem related to the determination of nonlinear singular vectors and singular values is formulated. The general idea of this approach is demonstrated by a simple two-dimensional quasigeostrophic model in the atmospheric and oceanic sciences. The advantage and its applications of the new method to the predictability, ensemble forecast and finite-time nonlinear instability are discussed. This paper makes a necessary preparation for further theoretical and numerical investigations.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 40676016 and 10471039)the State KeyProgram for Basic Research of China (Grant Nos 2003CB415101-03 and 2004CB418304)+2 种基金the Key Project of the Chinese Academy of Sciences (Grant No KZCX3-SW-221)in partly by E-Institutes of Shanghai Municipal Education Commission (Grant NoN.E03004)the Natural Science Foundation of Zhejiang Province,China (Grant No Y606268)
文摘The El Nifio-Southern Oscillation （ENSO） is an interannual phenomenon involved in the tropical Pacific Oceanatmosphere interactions. In this paper, an asymptotic method of solving the nonlinear equation for the ENSO model is used. And based on a class of oscillator of ENSO model, the approximate solution of a corresponding problem is studied by employing the perturbation method. Firstly, an ENSO model of nonlinear time delay equation of equatorial Pacific is introduced, Secondly, by using the perturbed method, the zeroth and first order asymptotic perturbed solutions are constructed. Finally, from the comparison of the values for a figure, it is seen that the first asymptotic perturbed solution using the perturbation method has a good accuracy. And it is proved from the results that the perturbation method can be used as an analytic operation for the sea surface temperature anomaly in the equatorial Pacific of the atmosphere-ocean oscillation for the ENSO model.
文摘 This paper presents a methodology which is very useful to design shape-preserving advection finite difference scheme on general E-grid horizontal arrangement of variables through introducing a two-step shape-preserving positive definite advection scheme in the moisture equation of the LASG-REM (LASG regional E-grid eta-coordinate forecast model). By trial-forecasting six local heavy raincases, the efficiency of the shape-preserving advection scheme in practical application has been examined. The LASG-REM with the shape-preserving advection scheme has a good forecasting ability for local precipitation.
基金supported by the National Key Technologies R&D Program of China (Grant No.2009BAC51B02)
文摘A pair of northeast-southwest-tilted mid-tropospheric ridges and troughs on the continental scale was observed to be the key circulation feature common among wintertime extensive and persistent low tempera-ture events (EPLTE) in China.During the persistence of such anomalous circulations,the split flow over the inner Asian continent and the influent flow over the southeast-ern coast of China correspond well to the expanded and amplified Siberian high with tightened sea level pressure gradients and hence,a strong,cold advection over south-eastern China.The western Pacific subtropical high tends to expand northward during the early stages of most EPLTEs.
基金supported by the Innovation Key Prograrn of the Chinese Academy of Sciences ZKCX2-SW-210the National Natural Science Foundation of China under Grant Nol40135020,and 40233033.
文摘Using the relative vorticity averaged over a certain area, a new index for measuring the longitudinal position of the subtropical high (SH) in the western Pacific is proposed to avoid the increasing trend of heights in the previous indices based on geopotential height. The years of extreme westward and eastward extension of SH using the new index are in good agreement with those defined by height index. There exists a distinct difference in large-scale circulation between the eastward and westward extension of SH under the new definition, which includes not only the circulation in the middle latitudes but also the flow in the lower latitudes. It seems that when the SH extends far to the east (west), the summer monsoon in the South China Sea is stronger (weaker) and established earlier (later). In addition, there exists a good relationship between the longitudinal position of SH and the summer rainfall in China. A remarkable negative correlation area appears in the Changjiang River valley, indicating that when the SH extends westward (eastward), the precipitation in that region increases (decreases). A positive correlation region is found in South China, showing the decrease of rainfall when the SH extends westward. On the other hand, the rainfall is heavier when the SH retreats eastward. However, the anomalous longitudinal position of SH is not significantly related to the precipitation in North China. The calculation of correlation coefficients between the index of longitudinal position of SH and surface temperature in China shows that a large area of positive values, higher than 0.6 in the center, covers the whole of North China, even extending eastward to the Korean Peninsula and Japan Islands when using NCEP/NCAR reanalysis data to do the correlation calculation. This means that when the longitudinal position of the SH withdraws eastward in summer, the temperature over North China is higher. On the other hand, when it moves westward, the temperature there is lower. This could explain the phenomenon of the ser
