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The contrast between the eastern and central Pacific (EP- and CP-) El Nino is observed in the different responses of zonal and vertical circulation in the tropics. To measure the different responses of the atmospheric circulation to the two types of El Nino, an eastern and a central Pacific southern oscillation index (EP- and CP-SOI) are defined based on the air-sea coupled relationship between eddy sea level pressure and sea surface temperature. Analyses suggest that while the EP-SOI exhibits variability on an interannual (2–7-yr) time scale, decadal (10–15-yr) variations in the CP-SOI are more dominant; both are strongly coupled with their respective EP- and CP-El Nino patterns. Composite analysis suggests that, during EP-ENSO, the Walker circulation exhibits a dipole structure in the lower-level (850 hPa) and upper-level (200 hPa) velocity potential anomalies and exhibits a signal cell over the Pacific. In the case of CP-ENSO, however, the Walker circulation shows a tripole structure and exhibits double cells over the Pacific. In addition, the two types of ENSO events show opposite impacts on global land precipitation in the boreal winter and spring seasons. For example, seasonal precipitation across mainland China exhibits an opposite relationship with the EP- and CP-ENSO during winter and spring, but the rainfall over the lower reaches of the Yangtze River and South China shows an opposite relationship during the rest of the seasons. Therefore, the different relationships between rainfall and EP- and CP-ENSO should be carefully considered when predicting seasonal rainfall in the East Asian monsoon regions.

Spatial distributions and seasonal variations of tropospheric water vapor over the Tibetan Plateau and the surrounding areas are explored by means of water vapor products from the high-resolution Atmospheric Infrared Sounder (AIRS) on board the Aqua satellite and the NASA Water Vapor Project (NVAP). Because NVAP has a serious temporal inhomogeneity issue found in previous studies, the AIRS retrieval product is primarily applied here, though similar seasonal variations can be derived in both datasets. Intense horizontal gradients appear along the edges of the plateau in the lower-tropospheric (500–700 hPa) water vapor and columnar precipitable water, in particular over the regions along the southeastern boundary. Rich horizontal structures are also seen within the plateau, but with a weaker gradient. In the mid- to upper troposphere (300–500 hPa), horizontal gradients are relatively weak. It is shown that there is always a deep layer of high water vapor content over the plateau with a peak around 500 hPa, which can extend from the surface to roughly 300 hPa and even to 100 hPa at some locations. This layer of high water vapor content has consistent influence on precipitating processes in the downstream regions such as the valleys of the Yellow and Yangtze Rivers. Estimated vertically integrated water vapor flux and moisture divergence in the two layers (500–700 and 300–500 hPa) further confirm the effect of the Tibetan Plateau on the downstream regions. In particular, the mid- to upper-layer water vapor (300–500 hPa) tends to play an essential role during both the warm and cold seasons, confirmed by the spatial distribution of seasonal-mean precipitation.

The long-term trends of total surface solar radiation (SSR), surface diffuse radiation, and surface air temperature were analyzed in this study based on updated 48-yr data from 55 observational stations in China, and then the correlation between SSR and the diurnal temperature range (DTR) was studied. The effect of total solar radiation on surface air temperature in China was investigated on the basis of the above analyses. A strong correlation between SSR and DTR was found for the period 1961–2008 in China. The highest correlation and steepest regression line slope occurred in winter, indicating that the solar radiation effect on DTR was the largest in this season. Clouds and water vapor have strong influences on both SSR and DTR, and hence on their relationship. The largest correlations between SSR and DTR occurred in wintertime in northern China, regardless of all-day (including clear days and cloudy days) or clear-day cases. Our results also showed that radiation arriving at the surface in China decreased significantly during 1961–1989 (dimming period), but began to increase during 1990–2008 (brightening period), in agreement with previous global studies. The reduction of total SSR offset partially the greenhouse warming during 1961–1989. However, with the increase of SSR after 1990, this offsetting effect vanished; on the contrary, it even made a contribution to the accelerated warming. Nonetheless, the greenhouse warming still played a controlling role because of the increasing of minimum and mean surface temperatures in the whole study period of 1961–2008. We estimated that the greenhouse gases alone may have caused surface temperatures to rise by 0.31–0.46°C (10 yr)−1 during 1961–2008, which is higher than previously estimated. Analysis of the corresponding changes in total solar radiation, diffuse radiation, and total cloud cover indicated that the dimming and brightening phenomena in China were likely attributable to increases in absorptive and scattering aerosols in the atmosphere, respectively.

During year-to-year El Niño events in recent decades, major sea surface warming has occurred frequently in the central Pacific. This is distinct from the eastern Pacific warming pattern during canonical El Niño events. Accordingly, the central-Pacific El Niño exerts distinct impacts on ecosystems, climate and hurricanes worldwide. The increased frequency of the new type of El Niño presents a challenge not only for the understanding of El Niño dynamics and its change but also for the prediction of El Niño and its global impacts at present and future climate. Previous studies have proposed different indices to represent the two types of El Niño for better understanding, prediction and impact assessment. Here, we find that all popularly used indices for the central-Pacific El Niño show a dominant spectral peak at a decadal period with comparatively weak variance at interannual timescales. Our results suggest that decadal anomalies have an important contribution to the occurrence of the central-Pacific El Niño over past decades. Removing the decadal component leads to a significant reduction in the frequency of the central-Pacific El Niño in observations and in Coupled Model Intercomparison Project Phase 5 simulations of preindustrial, historical and future climate.

We investigate the variations of subsurface ocean temperature (SOT) based on the monthly-Simple Ocean Data Assimilation (SODA) during 1958–2007, and discuss the linkage between the variations of SOT and the eastern and central Pacific ENSO (EP and CP-ENSO) events. The wavelet analyses suggest that the variation of the EP and CP-ENSO events shows the 2–7 and the 10–15 years oscillation in the tropical sea surface temperature (SST), and coupled with a zonal dipole mode and a tripole mode in the SOT anomalous field reveled by the singular value decomposition (SVD) analysis. During the mature phase of CP-ENSO, the positive center of SOT at the subsurface layer locates in the west of dateline, which results in the increase of SOT in the Nino4 region and causes the CP-ENSO event. Statistical analysis implies that, the eastern and central Pacific subsurface indices which are defined by the expansion coefficients of the first and third SVD mode for SOT have shown the capabilities in disguising the EP and CP-ENSO events, respectively. In addition, corresponding to the increase of the SOT amplitude on the 10–15 years time scale, we found that the frequency and intensity of CP-El Nino events has exhibited an upward trend after the 1980s, which suggests that the CP-ENSO event has shown an enhanced impact on the global climate in the past decades.

This study focuses on the evolution of large-scale circulations before and after the beginning of the Meiyu and analyzes the formations of the typical vertical circulation pattern associated with Meiyu and its relationship with the Meiyu rainband. Results show that the typical vertical circulation pattern during the Meiyu season is characterized by the “two-leg”-type pattern in the vorticity field, a typhoon eye-like structure of the equivalent potential temperature field, as well as the sharp gradient of the equivalent potential temperature zone, i.e., the Meiyu front are typically presented in the Meiyu season. Tracking its evolution process, we find that the typical vertical circulation pattern is built at late March and early April along with the rainband locating at the area south to the Yangtze River. This typical pattern and the rainband both advance northward affecting Jianghuai valley since the beginning of Meiyu. Moreover, the typical vertical circulation pattern derived from Meiyu season has been formed in April and corresponds to the reverse of the land-sea thermal contrast between the Eastern Asia and western Pacific Ocean, demonstrating the close relationship of the movement between the rainband and the march of the East Asian subtropical summer monsoon.

Using station rainfall data and NCEP/NCAR reanalysis from 1978-2007, we charac- terize the spatial variations of the heavy rainfall (Meiyu) during June-July over the Jiang-Huai basin (JHB, ~28°-34° N and 110°-122° E) in East China and their associated atmospheric circula- tions. An empirical orthogonal function (EOF) analysis of the Meiyu rainfall revealed 2 other sig- nificant modes besides the dominant basin-wide in-phase mode. They include a north-south dipole (out-of-phase) pattern (EOF 2) and a roughly east-west dipole pattern (EOF 3). During the 'south flood and north drought' (SF/ND) phase of EOF 2, the western Pacific subtropical high (WPSH) is displaced southward, which prevents the East Asian summer monsoon from reaching as far north as in normal years. A cyclonic anomaly circulation at 850 hPa occurs over Southeast China and an ascending (descending) anomaly motion south (north) of ~30° N is seen over the JHB, which contributes to the excess (lack) of Meiyu rainfall south (north) of ~30° N over the JHB during the SF/ND years. During the opposite phase of this mode, these anomaly circulation pat- terns are roughly reversed. During the 'east wet and west dry' phase of EOF 3, the WPSH is dis- placed eastward, and a cyclonic anomaly circulation centered south of Japan brings more mois- ture from the Yellow and East China Seas into the eastern part of the JHB; while southwesterly vapor fluxes past over the western part of the JHB and converges over North China, leaving the western part of the JHB relatively dry. During the opposite phase, the WPSH is shifted northwest- ward, and the anomaly moisture transports are reversed over the JHB.

Here we use harmonic analyses to examine seasonal variations of China land rainfall, low-level winds, and atmospheric heating over East Asia during spring to summer and the associated subtropical summer monsoon activities. Our results indicate that the South China spring rainfall (SCSR) in March is the prophase of East Asian sub-tropical summer monsoon (EASSM), and the onset of EASSM and China summer rainy season starts in early April, characterized by the enhanced rainfall in South China and the seasonal reverse of zonal land-sea thermal contrast in sub-tropical East Asia. The EASSM onset is earlier than that of South China Sea summer monsoon, and it is active in east of 100°E and north of 20°N. Our analyses suggest that the subsequent heating appears over India-China Peninsula in March and South China in April and causes the low-level atmospheric warming and the zonal land-sea thermal contrast seasonal reverse in East Asian subtropics. The atmospheric heating over South China is the main force to drive the southwesterly winds, updrafts and strengthen the summer precipitation in South China.

Based on the daily NCEP/NCAR reanalysis data, the position variation of the western Pacific subtropical high (WPSH) in June 2005 and its relation to the diabatic heating in the subtropical East Asia are analyzed using the complete vertical vorticity equation. The results show that the position variation of the WPSH is indeed associated with the diabatic heating in the subtropical East Asian areas. In comparison with June climatology, stronger heating on the north side of the WPSH and relatively weak ITCZ (intertropical convergence zone) convection on the south side of the WPSH occurred in June 2005. Along with the northward movement of the WPSH, the convective latent heating extended northward from the south side of the WPSH. The heating to the west of the WPSH was generally greater than that inside the WPSH, and each significant enhancement of the heating field corresponded to a subsequent westward extension of the WPSH. In the mid troposphere, the vertical variation of heating on the north of the WPSH was greater than the climatology, which is unfavorable for the northward movement of the WPSH. On the other hand, the vertical variation of heating south of the WPSH was largely smaller than the climatology, which is favorable for the anomalous increase of anticyclonic vorticity, leading to the southward retreat of the WPSH. Before the westward extension of the WPSH in late June 2005, the vertical variation of heating rates to (in) the west (east) of the WPSH was largely higher (lower) than the climatology, which is in favor of the increase of anticyclonic (cyclonic) vorticity to (in) the west (east) of the WPSH, inducing the subsequent westward extension of the WPSH. Similar features appeared in the lower troposphere. In a word, the heating on the north-south, east-west of the WPSH worked together, resulting in the WPSH extending more southward and westward in June 2005, which is favorable to the maintenance of the rainbelt in South China.

In contrast to the weakened relationship between the Indian summer monsoon and El Nino–Southern Oscillation (ENSO) since 1970s, the East Asian summer monsoon (EASM) has exhibited a strengthened relationship with ENSO. In this study, observational and numerical evidences manifest that spring NAO may exert notable impacts on the enhancement of the EASM–ENSO relationship. Anomalous spring NAO induces a tripole sea surface temperature anomaly (SSTA) pattern in North Atlantic which persists into ensuring summer. The tripole SSTA excites downstream tele-connections of a distinct Rossby wave train prevailing over the northern Eurasia and a simple Gill-Matsuno-type quadrupole response over western Pacific. The former modulates the blocking highs over the Ural Mountain and the Okhotsk Sea. The latter enhances the linkage between the western Pacific subtropical high and ENSO. The co-effects of the two tele-connection patterns help to strengthen (or weaken) the subtropical Meiyu-Baiu-Changma front, the primary rain-bearing system of the EASM. As such, spring NAO is tied to the strengthened connection between ENSO and the EASM. Copyright © 2011 Royal Meteorological Society

This paper examines the effects of two largely contrasting aerosol emissions scenarios on regional climate using National Center for Atmospheric Research Community Climate System Model version 3: (1) increasing the anthropogenic aerosols over China and India by a factor of three and (2) reducing the global anthropogenic aerosols by a factor of 10. Dynamic footprints of the increased Asian aerosols with monthly variations are obtained from Model for OZone And Related chemical Tracers simulations. Increasing Asian aerosol emissions would result in cooling and reduction of precipitation over China and India, with large warming over the USA and southern Canada in winter and cooling in summer. Additionally, large changes in rainfall rate are identified over the tropical regions. In contrast, reducing the global aerosol emissions by a factor of 10 would significantly warm the atmosphere especially over the polluted land areas of both hemispheres. Increases in rainfall over polluted land areas are also noted. Deepening of the Aleutian low and weakening of the Icelandic low in winter are noted in the 500-mb geopotential height under both scenarios suggesting a strengthening of the North Pacific storm track and weakening of the North Atlantic Oscillation. The polar regions of winter hemisphere are subject to large changes in the 500-mb geopotential height. Teleconnection patterns associated with ENSO play important roles in causing large changes in surface air temperature and rainfall far away from the source regions of the altered aerosol concentrations. Copyright © 2009 Royal Meteorological Society

The Indian summer monsoon (ISM) tends to be intensified in a global-warming scenario, with a weakened linkage with El Niño–Southern Oscillation (ENSO), but how the East Asian summer monsoon (EASM) responds is still an open question. This study investigates the responses of the EASM from observations, theoretical, and modeling perspectives. Observational and theoretical evidence demonstrates that, in contrast to the dramatic global-warming trend within the past 50 years, the regional-mean EASM rainfall is basically dominated by considerable interannual-to-decadal fluctuations, concurrent with enhanced precipitation over the middle and lower reaches of the Yangtze River and over southern Japan and suppressed rainfall amount over the South China and Philippine Seas. From 1958 through 2008, the EASM circulation exhibits a southward shift in its major components (the subtropical westerly jet stream, the western Pacific Ocean subtropical high, the subtropical mei-yu–baiu–changma front, and the tropical monsoon trough). Such a southward shift is very likely or in part due to the meridional asymmetric warming with the most prominent surface warming in the midhigh latitudes (45°–60°N), which induces a weakened meridional thermal contrast over eastern Asia. Another notable feature is the enhanced ENSO–EASM relationship within the past 50 years, which is opposite to the ISM. Fourteen state-of-the-art coupled models from the Intergovernmental Panel on Climate Change show that the EASM strength does not respond with any pronounced trend to the global-warming “A1B” forcing scenario (with an atmospheric CO2 concentration of 720 ppm) but shows interannual-to-decadal variations in the twenty-first century (2000–99). These results indicate that the primary response of the EASM to a warming climate may be a position change instead of an intensity change, and such position change may lead to spatial coexistence of floods and droughts over eastern Asia as has been observed in the past 50 years.

In 2008 (January–February), East Asia (EA) experiences the most severe and long-persisting snowstorm in the past 100 years. Results in this study show that 2007/2008 winter is dominant by the third principal mode of the East Asian winter monsoon (EAWM) which explains 8.7% of the total surface air temperature variance over EA. Significantly distinguished from the first two leading modes, the third mode positive phase features an increased surface pressure over the northwestern EA, an enhanced central Siberian high (CSH), a strengthened and northwestward extended western Pacific subtropical high (WPSH) and anomalously strong moisture transport from western Pacific, Arabian Sea and Bay of Bengal to EA. It also exhibits an intimate linkage with the sea surface temperature anomalies (SSTAs) in the Arctic Ocean areas adjacent to northern Eurasian continent, central North Pacific and northeastern Pacific. Such SSTAs emerge in prior autumn and persist through ensuing winter, signifying precursory conditions for the anomalous third EAWM mode. Numerical experiments with a simple general circulation model demonstrate that the Arctic SSTAs excite geo-potential height anomalies over northern Eurasian continent and impacts on the CSH, while the extra-tropical Pacific SSTAs deform the WPSH. Co-effects of them play crucial roles on origins of the third EAWM mode. Based on these results, an empirical model is established to predict the third mode of the EAWM. Hindcast is performed for the 1957–2008 period, which shows a quite realistic prediction skill in general and good prediction ability in the extreme phase of the third mode of the EAWM such as 2007/2008 winter. Since all these predictors can be readily monitored in real time, this empirical model provides a real time forecast tool and may facilitate the seasonal prediction of high-impact weather associated with the abnormal EAWM.

NCEP/NCAR reanalysis data and a 47-year precipitation dataset are utilized to analyze the relationship between an atmospheric heat source (hereafter called 〈 Q1 〉) over the Qinghai-Xizang Plateau (QXP) and its surrounding area and precipitation in northwest China. Our main conclusions are as follows: (1) The horizontal distribution of 〈 Q1 〉 and its changing trend are dramatic over QXP in the summer. There are three strong centers of 〈 Q1 〉 over the south side of QXP with obvious differences in the amount of yearly precipitation and the number of heat sinks predominate in the arid and semi-arid regions of northwest China (NWC), beside the northern QXP with an obvious higher intensity in years with less precipitation. (2) In the summer, the variation of the heat source’s vertical structure is obviously different between greater and lesser precipitation years in eastern northwest China (ENWC). The narrow heat sink belt forms between the northeast QXP and the southwestern part of Lake Baikal. In July and August of greater precipitation years, the heating center of the eastern QXP stays nearly over 35°N, and at 400 hPa of the eastern QXP, the strong upward motion of the heating center constructs a closed secondary vertical circulation cell over the northeast QXP (40°-46°N), which is propitious to add precipitation over the ENWC. Otherwise, the heating center shifts to the south of 30°N and disappears in July and August of lesser precipitation years, an opposite secondary circulation cell forms over the northeast QXP, which is a disadvantage for precipitation. Meanwhile, the secondary circulation cell in years with more or less precipitation over the ENWC is also related to the heat source over the Lake Baikal. (3) The vertical structure of the heat source over the western QXP has obvious differences between greater and lesser precipitation years in western northwest China in June and July. The strong/weak heat source over the western QXP produces relatively strong/weak ascending motion and correspondingly constructs a secondary circulation cell in lesser/greater precipitation years.

In this study, the National Center for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis data from 1979 to 2005 is used to investigate the possible impact of IntraSeasonal Oscillation (ISO) of the South China Sea (SCS) monsoon on the West Pacific Subtropical High (WPSH) double ridges. Three WPSH modes are defined as the 3/6 mode, the 1/2 mode and the dual mode, for the amplitude of the 30–60-day oscillation of SCS summer monsoon which is larger, smaller and comparable to the 10–20-day oscillation, respectively. The results show that there are no double ridges of WPSH present during 3/6 mode, but a weak process can be found during 1/2 mode. However, a powerful double-ridge structure of WPSH is present in several phases of the dual mode during both the 10–20-day oscillation and the 30–60-day oscillation. Then two typical WPSH double ridge cases in 1999, a special year of the dual mode, are chosen to further discuss this interesting phenomenon. Case 1 (24 July–27 July) is much weaker, and in this case the southern ridge disappears after several days, while during case 2 (3 August–11 August), the southern ridge finally replaces the northern ridge. The double ridges are much stronger compared to case 1. The ISO evolution feature is different between case 1 and case 2. The anomalous circulation of 10–20-day oscillation is anticyclonic over the southern ridge during both case 1 and case 2. However, the anomalous circulation of 30–60-day oscillation is cyclonic during case 1 and anticyclonic during case 2. It is this difference that leads to the double ridges being more powerful in case 2 than in case 1. This indicates that the 10–20-day oscillation of the SCS summer monsoon plays a key role in the WPSH double-ridge formation, while the 30–60-day oscillation provides a favorable background for it.

Meiyu onset (MO) over Yangtze-Huaihe River Valley (YHRV) possesses obvious characteristics of interannual variations. Based on NCEP/NCAR reanalysis data sets, NOAA OLR and ERSST data, the interannual variability of MO(IVMO) and its previous strong influence signal (PSIS) are investigated. The possible mechanisms that the PSIS affecting IVMO are also discussed. The results show that the previous CP-ENSO (Central Pacific El Nino/Southern Oscillation) event is the PSIS affecting IVMO and it has a better accuracy rate of short-term climate prediction and practicality. The MO is most likely to be late (early) with the warm (cold) phase of CP-ENSO in previous boreal February and spring. CP-ENSO affects MO mainly by means of EAP (East Asian-Pacific) or JP (Japanese-Pacific) teleconnection, in which the tropical western North Pacific anticyclone plays an important role. In the years of CP-ENSO warm phase, the tropical warm wet water vapor transportation to YHRV is late. The anomalous positive sea surface temperature near the equatorial central Pacific results in late northward jump of the western Pacific subtropical high and late establishment of Indian southwest monsoon via air-sea interaction, which leads to late seasonal transition of the atmospheric circulations over East Asia from boreal spring to summer. Late seasonal transition of the atmospheric circulations and late tropical warm wet water vapor transport to YHRV are the primary reasons that cause the late MO. The situations are directly opposite in the years of CP-ENSO cold phase.

On the basis of NCEP/NCAR version I daily reanalysis data from 1971 to 2000 and by the methods of inverse calculation, correlation analysis and comparative analysis, the influences of atmospheric heat source (AHS) over the Tibetan Plateau on the large-scale AHS and the general circulation in summer are studied in this paper. The results show that AHS over the plateau in summer may trigger a heat source wavetrain propagating northeastward along the coast from the East Asian continent and West Pacific to Bering Strait-Arctic or even North America. In addition, if AHS over the eastern plateau is intense, South Asian High moves to southeast and West Pacific subtropical high moves to southwest; on the contrary, if AHS over the eastern plateau is weak, South Asian High moves to northwest and West Pacific subtropical high moves to northeast. Therefore, South Asian High and West Pacific subtropical high move in the horizontally-opposite directions in terms of interannual variation, for which AHS over the eastern plateau seems to be thermodynamically responsible.

The interdecadal variation of northward propagation of the East Asian Summer Monsoon (EASM) and summer precipitation in East China have been investigated using daily surface rainfall from a dense rain gauge network in China for 1957–2001, National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis, European Center for Medium-Range Weather Forecast (ECMWF) reanalysis, and Global Mean Sea Level Pressure Dataset (GMSLP2) from Climatic Research Unit (CRU). Results in general show a consistent agreement on the interdecadal variability of EASM northward propagations. However, it appears that the interdecadal variation is stronger in NCEP than in ECMWF and CRU datasets. A newly defined normalized precipitation index (NPI), a 5-day running mean rainfall normalized with its standard deviation, clearly depicts the characteristics of summer rainbelt activities in East China in terms of jumps and durations during its northward propagations. The EASM northward propagation shows a prominent interdecadal variation. EASM before late 1970s had a rapid northward advance and a northern edge beyond its normal position. As a result, more summer rainfall occurred for the North China rainy season, Huaihe-River Mei-Yu, and South China Mei-Yu. In contrast, EASM after late 1970s had a slow northward movement and a northern edge located south of its normal position. Less summer precipitation occurred in East China except in Yangtze River basin. The EASM northernmost position (ENP), northernmost intensity (ENI), and EASM have a complex and good relationship at interdecadal timescales. They have significant influences on interdecadal variation of the large-scale precipitation anomalies in East China.

High-resolution satellite measurements are used to study the air-sea interaction over the Kuroshio Extension (KE) region during spring time. There are two oceanic fronts in the KE region off the east coast of Japan. These fronts are generally associated with strong ocean currents, which may display unstable meander, resulting in remarkable warm sea surface temperature (SST) ridges and cold SST troughs. Analyses of these satellite observations reveal a significantly positive correlation between sea surface wind speed and its underlying SST along these fronts. This positive SST-wind correlation becomes even more significant when strong meanders occur along the fronts. This positive SST-wind correlation indicates an ocean-to-atmosphere feedback over the KE region during spring time. A high-resolution regional atmospheric model is used to investigate the atmospheric response to SST changes along the two fronts.

Based on analysis of the climatic temperature latitudinal deviation on middle troposphere, its seasonal cycle suggests that due to the rapid warming from eastern China continent to the east of Tibetan Plateau and the heating of Tibetan Plateau in spring, seasonal transition of the thermal difference between East Asia continent and West Pacific first takes place in the subtropical region with greatest intensity. On the accompanying low troposphere, the prevailing wind turns from northerly in winter to southerly in summer with the convection precipitation occurring at the same time. This maybe indicates the onset of the East Asian subtropical summer monsoon. Consequently, we advice that the seasonal cycle formed by the zonal thermal contrast between Asian continent and West Pacific may be an independent driving force of East Asian subtropical monsoon.

Double ridges in the Western North Pacific Subtropical High (WPSH) in 1998 are studied as a particular case using NCEP/NCAR reanalysis data and the Black Body Temperature (TBB) data. In contrast to typical single ridge in WPSH, double ridges are found during July in 1998 and associated with the second Meiyu activity in the Yangtze River valley. The second ridge of WPSH is built up in the south of the first one and contributes to the stagnancy of WPSH in the south in middle of July. It is different from the previous view that the stagnancy of WPSH in the south resulted from the sudden southward withdrawal of the original ridge. The characteristics of double ridges including the structure, evolution and possible mechanisms are investigated with the case of 1998. The results show that there are a lot of differences in the large-scale circulation, temperature and humidity between the single ridge and double ridges of the WPSH. The north branch of the double ridges has coherent characteristics with the traditional single ridge, while the south branch is characterized by the tropical systems. There are evidences to support that the formation of the double ridges is associated with the northward movement of equatorial buffer zone and the persistence is related to the evolution of tropical convections. The rainfall pattern in eastern China associated with the double ridges of WPSH is examined using the instrumental records of precipitation in China. Two rain belts shaped as an italic "L"-like pattern in eastern China are found to be related to the double ridges. This study provides new evidence to understand the variability of WPSH and associated East Asian summer monsoon activity on synoptic scales.

This paper reviews briefly advances in recent research on monsoon by Chinese scholars, including primarily: (1) the establishment of various monsoon indices. In particular, the standardized dynamic seasonal variability index of the monsoon can delimit the geographical distribution of global monsoon systems and determine quantitatively the date of abrupt change in circulation. (2) The provision of three driving forces for the generation of monsoon. (3) The revelation of the heating-pump action of the Tibetan Plateau, which strengthens southerlies in the southern and southeastern periphery of the Plateau and results in a strong rainfall center from the northern Bay of Bengal (BOB) to the Plateau itself. (4) Clarification of the initial onset of the Asian Summer Monsoon (ASM) in the BOB east of 90°E, Indochina Peninsula (ICP) and the South China Sea, of which the rapid northward progression of tropical convection in the Sumatra and the rapid westward movement of the South Asia High to the Indochina Peninsula are the earliest signs. (5) The provision of an integrated mechanism for the onset of the East Asian Summer Monsoon (EASM), which emphasizes the integrated impact of sensible heat over Indian Peninsula, the warm advection of the Tibetan Plateau and the sensible heat and latent heat over the Indochina Peninsula on the one hand, and the seasonal phase-lock effect of the northward propagation of low frequency oscillation on the other. (6) The revelation of the “planetary-scale moisture transport large-value band” from the Southern Hemisphere through to the Asian monsoon region and into the North Pacific, which is converged by several large-scale moisture transport belts in the Asian-Australian monsoon regions and whose variation influences directly the temporal and spatial distribution of summer rainfall in China. (7) Presenting the features of the seasonal advance of the EASM, the propagation of intraseasonal oscillation, and their relationship with rainfall in China; indicating that the intraseasonal oscillation of the EASM propagates in the form of a wave-train along the coast and behaves as monsoon surge propagating northward. (8) Describing the interannual and interdecadal variation of Asian monsoon, revealing the factors affecting it, and possible mechanisms of the variation of Asian monsoon. An elementary outlook on the existing problems and future direction of monsoon research is also provided.

Although Meiyu rainfall has its in-phase spatial variability over the Changjiang-Huaihe River Valley (CHRV) in most years, it is distributed in some years like a seesaw to the north and south of the Changjiang River, when the precipitation tends to be nearly normal throughout the valley, which would inevitably increase difficulties of making short-term prediction of the rainfall. For this reason, EOF analysis is made on 15 related stations’ precipitation from June to July during 1951–2004, revealing that the EOF2 mode shows largely a north-south seesaw-like pattern, and thereby classifying Meiyu patterns into two types: “northern drought and southern flood (NDSF)” and “northern flood and southern drought (NFSD)”. Afterwards, the authors investigated ocean-atmospheric characteristics when these two anomalous types occured using the NCEP reanalysis (version 1) and the extended reconstructed SSTs (version 2). The results show that in the NDSF years, the low-level frontal area and moisture convergence center lie more southward, accompanied by weaker subtropical summer monsoon over East Asia, with the western Pacific subtropical high and 200 hPa South Asia High being more southward. Both the Northern and Southern Hemisphere Annular Modes are stronger than normal in preceding February; SST is higher off China during boreal winter and spring and the opposite happens in the NFSD years. Also, this seesaw-form Meiyu rainfall distribution might be affected to some degree by the previous ENSO event.

The Northeast Cold Vortex (NECV) is an important weather system in the middle and high latitudes in East Asia. Its time scale is synoptic, yet the frequent activities of NECV have significant “climate effect” which influences not only the monthly temperature in the lower troposphere in Northeast China but also the Meiyu rainfall in East Asia. On the basis of ERA-40 reanalysis data provided by ECMWF, the “climate effect” of NECV and its relationship with Meiyu in East Asia are studied. It is shown that there is significant correlation between NECV during the Meiyu period and rainfall amount: strong NECV corresponds to more Meiyu rainfall and weak NECV corresponds to less rainfall. In strong NECV years, the dry and cold air from the north is led to the south by NECV, converges with the lower-level warm and wet southwesterly on the north verge of Meiyu region, thus forms an unstable stratification of “upper dryness and lower wetness”. Triggered by ascending motion, the Meiyu rainfall amount is more than usual. It is on the contrary in weak NECV years. The anomalous SST in north Pacific in the previous year may be a factor that results in the anomalous NECV at Meiyu period. The land-sea thermal contrast in summer facilitates NECV, while that in winter inhibits NECV. All of the above provide a meaningful result for the short-term climate prediction of NECV and Meiyu.

Due to rapid economic development, China has experienced one of the greatest rates of change in land use/land cover during the last two decades. This change is mainly urban expansion and cultivated land reduction in urban growth regions, both of which play an important role in regional climate change. In this paper, the variation of the urban heat island (UHI) caused by urbanization has been evaluated with an analysis of land use change in China. First, meteorological observation stations were grouped by different land cover types (dry land, paddy field, forest, grassland, water field, urban, rural inhabitable area, industrial and mineral land, and waste land) throughout China. These stations were subdivided into urban and non-urban classes. Then, a new method was proposed to determine the UHI intensity from the difference between the observed and the interpolated air temperature of urban type weather stations. The results indicate that the trends of UHI intensity in different land use change regions are spatially correlated with regional land use and its change pattern. During 1991-2000, the estimated UHI intensity has increased by 0.11 degrees C per decade in the spring and has fluctuated in other seasons throughout China resulting from land use change.

Using NCEP/NCAR reanalysis data for the period of 1957–2001, the climatological seasonal transition features of large-scale vertically integrated moisture transport (VIMT) in the Asian-Australian monsoon region are investigated in this paper. The basic features of the seasonal transition of VIMT from winter to summer are the establishment of the summertime “great moisture river” pattern (named the GMR pattern) and its eastward expansion, associated with a series of climatological events which occurred in some “key periods”, which include the occurrence of the notable southerly VIMT over the Indochina Peninsula in mid March, the activity of the low VIMT vortex around Sri Lanka in late April, and the onset of the South China Sea summer monsoon in mid May, among others. However, during the transition from summer to winter, the characteristics are mainly exhibited by the establishment of the easterly VIMT belt located in the tropical area, accompanied by some events occurring in “key periods”. Further analyses disclose a great difference between the Indian and East Asian monsoon regions when viewed from the meridional migration of the westerly VIMT during the seasonal change process, according to which the Asian monsoon region can be easily divided into two parts along the western side of the Indochina Peninsula and it may also denote different formation mechanisms between the two regions.

Based on summarizing previous achievements and using data as long and new as possible, the onset characteristics of Asian summer monsoon and the role of Asian-Australian “land bridge” in the onset of summer monsoon are further discussed. In particular, the earliest onset area of Asian summer monsoon is comparatively analyzed, and the sudden and progressive characteristics of the onset of summer monsoon in different regions are discussed. Furthermore, the relationships among such critical events during the onset of Asian summer monsoon as the splitting of subtropical high belt over the Bay of Bengal (BOB), the initiation of convection over Indo-China Peninsula, the westward advance, reestablishment of South Asian High, and the rapid northward progression of convection originated from Sumatra in early summer are studied. The important impact of the proper collocation of the latent heating over Indo-China Peninsula and the sensible heating over Indian Peninsula on the splitting of the subtropical high belt, the deepening of BOB trough, the activating of Sri Lanka vortex (twin vortexes in the Northern and Southern Hemispheres), and the subsequent onset of South China Sea summer monsoon are emphasized.

Using the 5-day averaged data from the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis, and precipitation from rain gauge stations in China for the period 1981–2000, we investigated seasonal variations and associated atmospheric circulation and precipitation of the southwesterly wind over eastern China. The southwesterly wind over eastern China begins earliest over southeastern China and strengthens gradually from spring to the early summer, as it extends northward. The strengthening of the spring southwesterly wind, the tropospheric upward motion, and the convergence of low-level water vapor over southeastern China results in the beginning of the local rainy season. The beginning of the Mei-yu (Plum rainfall) is connected with the northward march of the southwesterly wind. The southwesterly wind reaches the valley of the Yangtze River in the early summer and northern China in the middle summer. This signifies an onset of the large-scale southwesterly wind over eastern China. Accordingly, the rain belt over southeastern China moves to the valley of the Yangtze River in the early summer and to northern China in the middle summer. Moreover, the southerly wind extends southward to the South China Sea from the spring to summer, though it does not stretch from the South China Sea to southeastern China at those times. The strengthening of the southerly wind over southeastern China is associated with a weakening/strengthening of the eastward/westward subtropical tropospheric temperature gradient between southwestern China and the western North Pacific. The developments of a low-pressure system over southwestern China and the subtropical high-pressure system over the western North Pacific may contribute to the strengthening of the southwesterly wind. A northward advance of the high-pressure system favors the southwesterly wind stretching from southeastern China to northern China. The onset of the Indian summer monsoon also strengthens the summer southwesterly wind over eastern China.

The generality and some climatological charac- teristics of the double ridge systems of subtropical high (SH) are investigated statistically by using the daily NCEP/NCAR reanalysis data from 1958 to 1998. The results show that the SH double-ridge event is a common phenomenon in the Northern Hemisphere, with the distinct seasonal and re- gional features, that is, the majority of SH double-ridge geneses concentrate over the eastern North India Ocean- western North Pacific as well as the central North Pacific in the period from mid-July to mid-September. Especially over the western North Pacific subtropics, the SH double-ridge events are extremely active. It is found that the life cycle of most double-ridge events of western Pacific subtropical high (WPSH) is shorter but some still last longer. The WPSH dou- ble-ridge events occur most frequently from July to Septem- ber, while there is a paucity of occurrences during Novem- ber-March. Also, it is shown that the WPSH double-ridge events have a strong interannual variation with a certain periodicity which possesses a remarkably abrupt change in the mid-1970s. Additionally, the relationship between the WPSH double ridges and the meridional movement of WPSH is discussed.

A 3-D chemical transport model (OSLO CTM2) is used to investigate the impact of the increase of NO x emission over China. The model is capable to reproduce basically the seasonal variation of surface NO x and ozone over eastern China. NO x emission data and observations reveal that NO x over eastern China increases quite quickly with the economic development of China. Model results indicate that NO x concentration over eastern China increasingly rises with the increase of NO x emission over China, and accelerates to increase in winter. When the NO x emission increases from 1995 to its double, the ratio of NO2/NO x abruptly drops in winter over northern China. Ozone at the surface decreases in winter with the continual enhancement of the NO x level over eastern China, but increases over southern China in summertime. It is noticeable that peak ozone over northern China increases in summer although mean ozone changes little. In summer, ozone increases in the free troposphere dominantly below 500 hPa. Moreover, the increases of total ozone over eastern China are proportional to the increases of NO x emission. In a word, the model results suggest that the relationship between NO x and ozone at the surface would change with NO x increase.

Based on the reanalysis data from NCEP/NCAR and other observational data, interannual variability of the Mascarene high (MH) and Australian high (AH) during boreal summer from 1970 to 1999 is examined. It is shown that interannual variability of MH is dominated by the Antarctic oscillation (AAO), and MH tends to be intensified with the development of the circumpolar lows in high southern latitudes. On the other hand, AH is correlated with AAO as well as El Nino and Southern Oscillation (ENSO), and tends to be intensified when El Nino occurs. Since AH, especially MH, is positively correlated with AAO, composite analysis on the difference between the positive and negative MH is performed to reveal the physical mechanism responsible for the East Asian summer monsoon anomalies associated with AAO. The result shows that, with the intensifi- cation of MH, the Somali jet, and Indian monsoon westerlies, tend to be strengthened. Accordingly, AH and the associated cross-equatorial flow, become stronger whereas the trade wind over the tropical western and middle Pacific become weaker. In association with the above changes, convective activities near the Philippine Sea are largely suppressed, as a consequence, exciting a negative convection anomaly, and a Rossby wave train from East Asia via the North Pacific to the western coast of North America (a negative Pacific-Japan pattern). Corresponding to the negative Pacific-Japan pattern, an anomalous rainfall pattern appears in East Asia. Correlation analysis between AAO and sea level pressure, 500 hPa geopotential height further indicates that AAO is a strong signal influencing the climate anomaly in both hemispheres, including East Asia. Due to the seasonal persistence, AAO and the related MH and AH in boreal spring, may provide some useful information for the East Asian summer monsoon prediction. With the intensification of MH during boreal spring through summer, the Meiyu/Baiu rainfall from the Yangtze River valley to the Japan Islands tends to increase, while less rainfall is found outside of this region. In contrast with MH, the effect of AH on summer rainfall is confined to southern China.

Based on the reanalysis data from NCEP/NCAR and other observational data, interannual variability 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 latitudes deepens, the intensity of MH will be intensified. On the other hand, AH is correlated by AAO as well as El Nino and South Oscillation (ENSO), the intensity of AH will be intensified when El Nino occurs. Both correlation analysis and case 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 River valley to Japan, in contrast, less rainfall is found over southern China and western Pacific to the east of Taiwan, and most of regions in mid-latitudes of East Asia. Compared with MH, the effect of AH on summer rainfall in East Asia is limited 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 timescale, 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 East Asian summer monsoon and prediction of summer precipitation in China.

This work presents an intelligent monitoring feasibility on composite insulators. By implanting fiber Bragg grating (FBG) into the composite insulator rod, the intelligence rod structure can online monitor the operating condition of the composite insulator. The transmission matrix is used to get the relationships between the stress strain or the thermal strain and the wavelength drift of in the insulator rod, and based on the results, this work provides the feasibility analysis, the system design and field application.

This paper studied on the optimization and simulation of a production system in the green supply chain, and used the Flexsim simulation software to simulate the optimization process, then established the comprehensive evaluation model to evaluate the result of the simulation. This evaluation model can provide more clear reference for the reasonable planning and scientific decision-making.

[1] As one of the major predictability sources on an intraseasonal time scale, the Madden-Julian Oscillation (MJO) exerts a profound influence on the subseasonal forecast of the East Asian (EA) surface air temperature (SAT) and precipitation. In this study we examine the direct link of the MJO with the EA SAT and precipitation and its dynamical mechanism. To represent the MJO, we perform an empirical orthogonal function (EOF) analysis on pentad outgoing longwave radiation (OLR) over (20°S−20°N, 60°E−150°W). The EOF1 mode is mostly characterized by a single convection center near the maritime continent (90°−150°E), whereas the EOF2 mode has an east-west dipole structure with enhanced convection over the eastern Indian Ocean and suppressed convective activities over the tropical western Pacific. At the same pentad of a positive EOF1 phase, large areas of cold anomalies with reduced precipitation emerge in the EA region north of 20°N and persist through two pentads later. At the same pentad of a positive EOF2 phase, SAT and precipitation exhibit a zonal dipole pattern with cold and dry anomalies covering the EA region west of 120°E and warm and wet anomalies to the east. These dipole anomalies in SAT and precipitation systematically move eastward in the next two pentads. A linearized global primitive equation model is utilized to assess the cause of the intraseasonal variability in SAT and precipitation over East Asia associated with the tropical heating of the MJO. The model responses to heating sources that mimic the EOF1 and EOF2 OLR patterns match well the general features of the observed circulation anomalies. Under forcing of a positive phase of the EOF1 pattern, strengthened local Hadley cell or monsoon circulations within (90°E−150°E) are reproduced, with anomalous northerly winds and dry anomalies prevailing in the lower troposphere over East Asia. The processes that influence East Asia are mainly associated with intraseasonal changes in local Hadley circulation and the Northern Hemisphere branch of the equatorially trapped Rossby wave gyres forced by the MJO heating.

On the basis of the datasets from the routine meteorological observations, radar, satellite and NCEP reanalysis and using numerical simulation and diagnostic analysis, this paper studies the mechanism of cold-air snowstorms and the cause of locally strong cold-air snowstorms in the north of Shandong Peninsula. The results indicate that the mechanism of cold-air snowstorms in the Shandong Peninsula is that as the strong cold air moves through Bohai and Bohai Strait, it exchanges heat and water vapor with the warm sea surface. When it arrives in the Shandong Peninsula, the air in the lower troposphere becomes unstable. The convergence system in the northern coast, formed by the land-sea breeze due to the land-sea temperature difference and the environmental wind, triggers the release of the unstable energy and produces the cold-air snowstorms in the north of Shandong Peninsula. The cause of the locally strong coldair snowstorms in the northern coast of Shandong Peninsula is that the convergence system in the western coast of Liaodong Peninsula moves downstream along with the northwesterly and combines with the convergence belt in the northern coast of Shandong Peninsula, leading to the strengthening of the local convergence and the local cold-air snowstorms.

Using Doppler radar products from three intense convective precipitation events occurring on the night of June 12, early morning and night on July 12, 2006 over the Tianjin area, a comparative study is made, showing that typically, the radial velocity field changes earlier than does the echo-intensity field at the initial and mature stages of precipitation, such that much attention should be paid to the variation in the velocity field in doing nowcasts of rainfall, and the Doppler velocity variation in conjunction with Auto-Nowcaster predictions helps determine the change in radar echo intensity and its movement direction, thereby improving the accuracy of nowcasts of strongly convective precipitation.

The Tibetan long-term monthly mean rainfall exhibits a SE to NW decrease, showing strong regionality. The summertime vigorous rainfall centers are roughly coincident with those of heat sources averaged throughout the atmospheric extent, with latent heating making the greatest contribution to . In the heat source stronger (weaker) year than normal, the western Pacific subtropical high amplifies (falls off), making westward extension (eastward withdrawal); the South-Asian high intensifies (weakening), eastward expanding (westward extending); summer monsoon becomes intense (enfeebled). In that case, the precipitation is more (less) in the Jiang-Huai valley compared to normal in relation to the rainfall lower (higher) than mean over the littoral provinces of South China, and two parallel anomalously deep wavetrains (just one wavetrain) of cyclones alternate with anti-cyclones over the Pacific.