Abstract:The authors adopt a new two-way land-atmosphere coupled model R42_AVIM. By contrast of experiments with and without vegetation cover, the possible impact of global vegetation distribution on climate and atmosphere circulation is discussed. The results show that the actual vegetation coverage on land can alter the surface characteristic parameters obviously on planetary scale, especially for tropical rainforest and boreal forest. Under the distribution of actual vegetation, the surface net radiation and the latent heat flux will increase, while the surface sensible heat flux will decrease. In the areas where the leaf area index (LAI) is relatively large, the surface temperature will decrease. Moreover, this effect can also extend to the middle and upper troposphere. In addition, the present vegetation distribution enhances the evaporation as well as the corresponding condensation latent heating in the tropics and mid-high latitudes, which makes the meridional circulation stronger. And then, the precipitation increases in the tropics and mid-high latitudes, while decreases in the subtropics. Meanwhile, vegetation can also reduce the sea-land temperature contrast and weaken the Asian summer monsoon.

Abstract:Based on the daily precipitation data from 740 stations, by means of linear trend estimate, Mann-Kendall test method, the long-term trends and interdecadal variation of precipitation, frequency, contribution to the total rainfall over North China during rainy seasons are analyzed. Some new results are discovered as follows: the rainfall over North China during rainy seasons, and five kinds of precipitation frequency and contribution over North China during rainy seasons have a certain decreased trend with different decreased rates. The most obvious decreased trend is the rainfall over North China during rainy seasons. The long-term decreased trend of the five kinds of precipitation frequency has obvious characteristic of gradual change, and the decreased trend of light rain frequency is biggest while the decreased trend of torrential rain and excessively heavy rainfall frequency is not significant. Meanwhile, the decreased trend of contribution of heavy rain to the total rainfall over North China are biggest. The biggest contribution to the total rainfall over North China is from heavy rain and close to one-third of the total rainfall in the past 50 years. The rainfall over North China during rainy seasons is mainly influenced by the heavy rain frequency and the excessively heavy rainfall contribution. The interdecadal abrupt change took placed in 1978 for both rainfall and excessively heavy rainfall contribution over North China during the rainy season, so the interdecadal abrupt change of excessively heavy rainfall contribution during rainy seasons results in the interdecadal abrupt change of rainfall over North China.

Abstract:Using data from X-band dual-polarization radar system set up by the Institute of Atmospheric Physics, Chinese Academy of Sciences, the paper discusses various dual-polarization radar parameters and their physical essence of representing hydrometeors. On the basis of reflectivity and differential reflectivity attenuation correction, the paper analyzes vertical structure and hydrometeor phase distribution structure of stratiform cloud, puts forward methods to position the melting layer and retrieve the vertical temperature profile in combination with the ground temperature. Statistical analysis for specific layers in the stratiform cloud is conducted, and with reference to international C- and S-band radar studies, ranges of X-band radar parameters, i.e. reflectivity, differential reflectivity, specific differential phase shift, and correlation coefficient, for several main hydrometers are acquired. On the basis of above results, hydrometeors are classified using the fuzzy logical method. The results reflect the phase distribution characteristics of stratiform cloud and hydrometeors. Then, possible precipitation mechanism is discussed according to two cases. The retrieved hydrometeor distribution is used to study microphysical processes of precipitation instead of using the radar echo structure. The results verify the three-layer conceptual model introduced by Koo Zhen-Chao (1980) in the 1960s. The studies provide the method for dual-polarization radar application to cloud and precipitation physics studies, and indicate its broad potential application prospect.

Abstract:With the analysis of the precursory signal observed in the key regions of the air－sea system, this study has developed a statistical prediction method for the East Asian winter monsoon (EAWM) intensity, by using the monthly data of the NCEP reanalysis and NOAA extended reconstructed sea surface temperature (SST). The EAWM intensity is closely associated with the prior September－October SST anomalies in the Kuroshio and its extension region and the tropical western Indian Ocean. A strong EAWM activity corresponds well to the positive SST anomaly in the Kuroshio and its extension region and to the negative anomaly in the tropical western Indian Ocean. On the other hand, the EAWM intensity is also significantly correlated with a prior (October) northern hemispheric circulation pattern, whose action centers are located in the central North Pacific, the Northeastern Pacific, North America and the North Atlantic, respectively. The potential of above-mentioned three precursory factors in predicting the EAWM intensity has been discussed and the possible physical linkages between the EAWM intensity and the three precursory factors have also been explored. The fitting analysis and trial predicting examination indicate that the prediction method established here has a high accuracy and is applicable for the qualitative prediction of the East Asian winter monsoon intensity.

Abstract:Based on the successful numerical simulation of typhoon Durian (2001) with the PSU/NCAR nonhydrostatic mesoscale model (MM5), the authors diagnose the contributions of middle tropospheric mesoscale convective vortex (MCV) to the Durian's genesis using the high resolution data (6 km) produced by MM5. The results show that the MCV have three important performances. First, playing the role of mesoscale organization system, the second vertical cycle of MCV transports the convective hot towers to the central area of MCV, making the hot towers have the trend to contest or merge each other, so that some hot towers become stronger or died. The feedback of the collective effect of hot towers makes the MCV intensify or maintain, and the MCV further pushes the assembling, merging and axisymmetrization of hot towers. Second, playing the role of memory system, because the MCV have the longer life time than individual hot tower, the MCV can reserve the heat, moisture, and vorticity left by the died hot towers, which will make the MCV area favorable to the TC genesis, and ultimately become the ‘embryo’ of Durian. Third, the MCV, the low tropospheric trough (vortex), and the hot towers conduct together the vertical uniformization between the lower and middle tropospheric systems through their interaction.

Abstract:The data from precipitation radar (PR), lightning imaging sensor (LIS), and passive microwave imaging (TMI) onboard the Tropical Rainfall Measuring Mission (TRMM) satellite have been used to investigate lightning activity and its relationship with precipitation structure of a strong squall line over south China on May 6, 2005. The results show that convective rains only occupied half of the area of stratiform rains, but the former contributed much more rainfall to the total than the latter. Most lightning flashes occur near the strong convective region, and a few flashes occur in the stratiform region of the squall line. At 6-km altitude, most of lightning flashes occur in the echo region between 35 and 50 dBZ, which peak during 40－45 dBZ, and fewer flashes can be seen in the echo region with reflectivity smaller than 30 dBZ. The results also indicate that the vertical profile of the maximum radar reflectivity has capability to reveal flash rate and vertical development of convective cells. Furthermore, it is found that most of lightning flashes occur in the region of low brightness temperature, especially the region lower than 200 K, and a few flash can also be seen in the region of 240－260 K, which usually corresponds to the stratiform region of squall lines. A combined study with another squall line over the Huanghe River－Huaihe River area on April 17, 2003 shows that there is a close relationship between flash rate and ice precipitation content between 7－11 km altitude at a convective cell scale, and the correlation coefficient is 0.92, which suggest that the stable relationship between flash rate and ice precipitation content can be valuable in the study of both the assimilation of lightning data into mesoscale models and lightning flash parameterizations of squall lines.

Abstract:High-resolution satellite observation data TRMM and AIRS are used to analyze the effect of mesoscale mountains on vertical structure and horizontal distribution of different types of rainfall during the Asian summer monsoon region from the perspective of climatological rainfall microphysical processes. It was found that the stratiform precipitation is the predominant rainfall type on both the windward and leeward sides of mesoscale mountains, and the rainfall on the windward side is stronger than that on the other side. In the meanwhile, the convective precipitation is mainly shallow convective precipitation on the windward side and deep convective precipitation on the leeward side, and the leeward rainfall is stronger. The results also demonstrate that along the direction followed by the southwest monsoon, the discrepancies of rainfall pixel numbers and microphysical processes between both the sides of mesoscale mountains reduce gradually. During the whole process, the convective precipitation changes from the windward side to the leeward side distincty, the stratiform precipitation is just the opposite. Also, atmospheric stability corresponds well to the convective precipitation on both the sides. In addition, this research on mesoscale orographic precipitation can provide a robust basis for the simulation of high-resolution terrain rainfall in regional climate models.

Abstract:Through analyzing radiosonde observation data during pre-onset and onset period of monsoon, the authors find that the second tropopause (ST) (also called tropical tropopause) is the main tropopause in western Tibetan Plateau. This kind of characteristic can be seen in the two seasons. Double tropopause frequency is high in winter, while the first tropopause (FT) (also called polar tropopause) is rarely seen in summer, in which there is only the second tropopause. Before the monsoon onset, the height of FT is about 10752 m, with its temperature about 219 K, pressure 245.2 hPa; the height of ST is about 16826 m, with its temperature about 202 K, pressure 93 hPa. During the monsoon onset, the height of FT is 10695 m, with its temperature 229 K, pressure 257 hPa; the height of ST is 17360 m, with temperature 198 K, pressure 89.4 hPa. The difference of average temperature between the two periods demonstrate that the temperature of ST is high in winter and low in summer; the FT's temperature is high in summer, low in winter. At hourly scale, the second tropopause height is in opposite phase separately with its temperature, pressure, and wind speed, which means that higher tropopause height is accompanied with lower pressure, temperature, wind speed. The FT's inversion layer inhibits upward heat transporting and cloud height. The FT plays an important role in atmosphere heating. From uniform mixing of wind speed, the authors can conclude that boundary layer height can be as high as 3500 m in May and July. The westerly jet have obvious seasonal change. It is stronger in winter with hardly any easterlies. During the monsoon onset period, the westerly jet becomes weaker due to its moving away from Gaize to the north. While the easterlies becomes stronger due to moving nearer to Gaize, and is on top of the subtropical westerlies.

Abstract:Based on the lightning location detection data, Doppler radar data, and synoptic information, this paper presents the lightning characteristics of a typical mesoscale convective system (MCS) in the north of Shandong Province on 1 August 2005. It is found that the negative cloud-to-ground (-CG) lightning is predominant over the positive cloud-to-ground (+CG) lightning during the whole thunderstorm lifetime. At the dissipation stage, IC (intra-cloud lightning) /CG is 2∶1 within the detection range. And when the electric field changed greatly, the lightning happened frequently. The CG lightning mainly occurred in the regions with high values of convective available potential energy (CAPE) and surface equivalent potential temperature. The comparison between the location of lightning activity and radar echo shows that -CG usually clusters in the intense echo region with high reflectivity (>40 dBZ), while +CG usually disperse in the weak echo (30 dBZ－40 dBZ) region. Relation between the cloud-top brightness temperature and the CG lightning location indicates that most flashes occurred in the area with temperature lower than -40℃, while the +CG lightning clustered in the region with the cloud-top temperature between -40℃ and -50℃. The comparison between the wind field retrieved from Doppler radar and the location of CG flashes indicates that the flashes are usually located in the cyclonic shear or wind shear areas which corresponds to the intense echo. The CG flashes are easier to happen in the stage that updraft reaches the maximum and downdraft appears.

Abstract:A new hourly rainfall dataset is formed using variational method, based on raingauge and radar-retrieved rainfall intensity. The new data are used to investigate temporal and spatial variations of precipitation structure within 111-km radius centered the typhoon, especially the evolution of rainfall structure during the concentric eyewalls cycle before Saomai landfall. The authors find that typhoon Saomai had concentric eyewalls before it landed, and the mean radii of the inner and outer eyewalls were 24 km and 59 km, respectively. The radius of the outer eyewall did not minish due to the rapid landfall of typhoon Saomai after the concentric eyewalls combination. During concentric eyewalls circulation, the precipitation in the inner and outer eyewalls and rainband regions was very heavy. In the outer eyewall region, the time series of mean rainfall rate was more variable than that in the inner eyewall and rainband regions. And in the inner and outer eyewalls regions, the mean rainfall rate increased with time, but in the rainband region it decreased. The precipitation in the inner-core and outer regions was also heavy, and the mean rainfall rate in the inner-core region increased abruptly about the three hours before Saomai landed, and then it decreased, accompanied with the reduction of the typhoon intensity after Saomai landed. The distribution of precipitation of typhoon Saomai was asymmetric. Before Saomai landfall, the maximum rainfall rates in the inner eyewall, outer eyewall, and rainband regions occurred in the right quadrant relative to the storm moving track, and the azimuth in the rainband region was always to the right of those in the inner and outer eyewalls regions. The azimuth of the maximum precipitation in outer eyewall and rainband regions varied with time during the concentric circulation. After typhoon Saomai landfall more precipitation in the inner-core and outer regions appeared in the back quadrant relative to the storm track.

Abstract:The field experiment of ozone dry deposition over grassland was performed by using the concentration gradient method in the suburban area of Beijing which is often situated downwind of urban plumes and then influenced by high ozone concentration episode. The vertical profiles of ozone concentration and meteorological parameters were measured in early autumn (23 September－13 October 2007) in a valley of Mangshan Forest Park. Strict data quality control procedures were performed to guarantee the credibility of following analysis. Results show that: (1) Both ozone flux and dry deposition velocity were characterized by strong diurnal variation, with daily mean values of －0.40 μg?m-2?s-1 (minus sign refers the direction towards the ground) and 0.55 cm/s respectively.(2) The ozone dry deposition flux is significantly influenced by the topographic wind, and the maximum ozone dry deposition flux occurs during the valley-wind prevailing period (0900－1500 LST) with a mean value of －0.67 μg?m-2?s-1, and it comes to averagely －0.44 μg?m-2?s-1 over the mountain-valley wind shift period (0800 LST in the morning and 1600 LST in the afternoon). When the observation site is predominated by mountain breeze, the downward ozone flux decreases to only －0.26 μg?m-2?s-1. The ozone dry deposition velocity displays the same feature with mean values of 0.74 cm/s, 0.50 cm/s, 0.47 cm/s respectively for these periods.(3) Canopy resistance calculated with the resistance model indicates the mean value of 184.0 s/m for the whole observation period. During the daytime, due to the gas-phase exchanges near leaf stomata and the strong photosynthesis effects, canopy resistance (109.0 s/m) is lower than that at night (217.7 s/m) when the plant physiological activities drop off.

Abstract:By using Simple Biosphere Model 2 (SiB2), surface energy balance budget, surface effective radiative temperature, and soil moisture were modeled for the GAME/Tibet Amdo site in a Tibetan short grass prairie (Amdo station) from 15 July through 10 September 1998. During the monsoon period the mean canopy height and the leaf area index were 0.05 m and 0.5, respectively. The study site represented the prevailing conditions of the northern Tibetan Plateau. The model was initialized and driven by using in situ measurements. The forcing data consist of the short-wave solar radiation, atmospheric long-wave radiation, vapor pressure, air temperature, horizontal wind speed, and precipitation. The model outputs of radiation components, turbulent heat fluxes, surface effective radiative temperature, and soil moisture were compared against direct measurements. Results show that: (1) SiB2 overestimated sensible, latent, and soil heat fluxes by 4%, 13%, and 8% respectively when it underestimated net radiation by 0.2%; (2) surface effective radiative temperature was underestimated by 5%; and (3) soil moisture was estimated reasonably. In general, radiation components simulated by SiB2 were more closer to measurements than heat fluxes with high degree of correlation.

Abstract:Based on the three-dimensional variational data assimilation retrieval (3DVAR) and four-dimensional variational data assimilation retrieval (4DVAR) methods, experiments of wind retrieval from Doppler lidar data were performed. Both the 3DVAR and 4DVAR methods were applied to the Paralympics test events in May 2008, observed by the vehicle-borne Doppler lidar. The retrieval wind filed was analysed by comparing with the buoy data. The results demonstrated that both the 3DVAR and 4DVAR methods were able to retrieve the detailed wind field near the sea surface, which could reflect the variation of wind direction, and accorded with the buoy data basically. The wind field retrieved with the 3DVAR method was more consistent with that with the 4DVAR method under the gale weather than gentle breeze. It also showed that the wind field retrieved with the 4DVAR method was more close to wind from the buoy data than that with the 3DVAR method, because the buoy data were used as the background field in the 4DVAR method. It was found that there was a very good correlation between the retrieved and buoy's wind directions, while there would be some correlation between the retrieved and buoy's wind speeds. The difference between the retrieved and buoy's wind directions(speeds)could be shown from the mean RMS error and the mean absolution error, so the retrieved wind should be used with caution under the gentle breeze weather.

Abstract:A Meiyu heavy rainfall event during 27-28 Jun 2002 is investigated by using GMS-5 satellite infrared images. It shows two stages of mesoscale convective system (MCS) activities with intensive precipitation. In the first stage, a circular-shape MCS moving from the northwest to southeast produces heavy rainfall in Henan Province of the central China; in the second stage, the southerly moving MCS develops and forms a persistent elongated convective system (PECS) which produces torrential rain over the Yangtze River basin. In order to understand why the cloud top shape of the MCS changes from circular to elongated, and what atmospheric processes are related, the NCEP/NCAR 1°×1° reanalysis data are filtered for scale separation. Results show that the mesoscale disturbances output by the Shuman-Shapiro filtering can well correspond to the area where the cloud top temperature is less than or equal to -52℃. Both the first stage circular-shape MCS and the second stage PECS have a similar structure with convergence at lower levels and divergence at upper levels in the troposphere. But their organizations are different: the former is mainly a mesoscale cyclone, while the latter is a mesoscale convergence zone, both at lower levels. This organizing differences cause the MCS cloud top evolution from circular to elongate.

Abstract:In general there exists“double ITCZ” bias either in coupled models or in atmospheric general circulation models; so does in the new version of the LASG/IAP (State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics, Chinese Academy of Sciences) spectral atmospheric model SAMIL_R42L26: there is less rainfall near the equator while more rainfall on both the north and south sides. This bias can affect the tropical circulations and global energy balance. However, the bias can be weakened through the modified Tiedtke cumulus convective parameterization scheme. The new scheme can affect the distribution of temperature in the lower troposphere, even on the surface, and the associated wind and divergence fields are also changed, which in turn create conditions for the further development of convection, forming a positive feedback. Finally the eastward extension of precipitation bias along the SPCZ (Southern Pacific Convergence Zone) can be effectively restrained, and at the same time, the insufficient rainfall over the tropical warm pool is increased.

Abstract:In terms of the monthly NCEP/NCAR data and the 160 site temperature data from the National Climate Center (NCC), the main causes of anomalously low surface air temperature in January 2008 over China are investigated on the basis of the possible mechanism of typical episodes occurring in recent 30 years. Results show that the January surface air temperature in 2008 is lower than normal in most part of China, which is linked closely to the teleconnection circulation anomaly associated with the North Atlantic Oscillation (NAO) and the jet stream over the North Atlantic. The main circulation causes for the lower temperature is that the jet stream becomes strong and expands to the East Atlantic with positive NAO as a wave train circulation anomaly pattern appearing from the North Atlantic to East Asian area, and higher pressure occurs to the south of Baikal, indicating that the cold air is stronger than normal. The circulation anomalies in the troposphere are influenced by those from the stratosphere. The circulation anomalies in the stratosphere occurred earlier in September 2007 than those in the troposphere appearing in December 2007. And both of them became strongest in January 2008. Anomalous wave fluxes propagate from the wave source in the stratosphere over East Asia downward and westward, and in the upper troposphere over the North Atlantic there is a remarkable convergence of wave fluxes, leading to enhancing of the ridge there with stronger northward heat transportation and the related front zone shifting, and the jet stream anomalously developing and easterly expanding. Thereby anomalous disturbance energy will disperse downwards by wave-flow interaction and induce teleconnection circulation anomalies, resulting in the lower temperature episode of 2008 in China.

Abstract:Based on the monthly rainfall of 160 stations over China and the sea surface temperature data in the Niño 3 region, the instability of interannual relationship between summer rainfall in China (SRC) and pre-winter sea surface temperature (WSST) in the Niño 3 region is studied by using sliding correlation, composition etc. It shows that the long-term variation of interannual relationship between SRC and WSST in the Niño3 region has obvious regionality and is more instable in northeastern and northwestern China than in eastern China. At the same time, it has a significant stage characteristic. The period from 1951－2007 can be separated into 1962－1977, 1978－1992, 1993 to present, according to the sliding correlation coefficients. Each stage has about sixteen years in length. Every turning from one stage to another is very short and is characterized by abrupt change. There are three obvious abrupt changes in the last 50 years, such as in the early 1960s, in the late 1970s, and in the late 1980s and early 1990s. Before and after the abrupt change, the correlation sign and intensity have obvious differences in some regions. It also shows that the influences of El Niño events in different stages have different features. There are two rainbelts during 1962－1977: one was located in North China, Northeast China Plain, and eastern Inner Mongolia, and the other was located in the middle reaches of the Yangtze River; there was less rainfall in the Qingling-Daba Mountains and the Yangtze River and Huaihe River valley. During 1978－1992, there was only one rainbelt located in the Qinling-Daba Mountains area and the middle and lower reaches of the Yangtze River; there was less rainfall in the Yellow River and Huaihe River valley, and North China to the south of Northeast China. And in the present stage (1993 to present), the spatial distribution of rainbelts is similar to that during 1962－1977, there are also two rainbelts located in southern China and northern China respectively. But the north rainbelt moves southward to the Sichuan Province, Chongqing, the Yellow River and Huaihe River valley, the lower reaches of the Yellow River, and Northeast China Plain; there is less rainfall in northern Hubei Province and the lower reaches of the Yangtze River; the feature of rainfall distribution is that there is more rainfall in northern China while less rainfall in southern China. So, not only the mean interannual relations between SRC and SST in the Niño 3 region but also their instabilities must be considered in the forecasting of flood season precipitation by using ENSO events.

Abstract:A hybrid four-dimensional variational（H4DVAR）data assimilation approach is proposed by combining the Ensemble Square Root Filter（EnSRF）with the Four-Dimensional Variational（4DVAR）data assimilation method， which is composed of two time windows with the first using EnSRF and the second using 4DVAR， and this combination can make good use of both EnSRF and 4DVAR. An Observing System Simulation Experiment（OSSE）is set up to investigate the ability to retrieve the true soil moisture profile with the new method by only assimilating the near-surface soil moisture observations into a land surface model. After comparing the performance of the three data assimilation schemes（i.e.，EnSRF，4DVAR，and H4DVAR），it is shown that the H4DVAR is superior to the rest two methods because it can quickly retrieve the soil moisture profile with less error. However， when small ensembles are used to calculate the background error covariance， the spurious long-range vertical error correlation between an observation and a state variable will have a bad influence on the estimation of soil moisture. Therefore the authors propose a method to tackle this issue by adding a correlation matrix with the elements defined by the Gaussian function into the original background error covariance. By this way， the rms error of the estimated soil moisture reduces from 0.036 cm3/cm3 to 0.016 cm3/cm3 with a relative reduction of 55.6%，and the most important is the large reduction of the errors in some soil moisture estimates， for example，the error at the depth of 90 cm reducing from 0.085 cm3/cm3 to 0.024 cm3/cm3 with a relative reduction of 71.8%.

Abstract:The factors of atmospheric circulations in the prediction model, which is built by the downscaling techniques and the partial least square regression for summer precipitation in eastern China, are studied by using the monthly data of the 74 characteristic quantities of the northern hemispheric circulations, and the precipitation at 160 stations over eastern China. The study is based on the occurrence frequency of the characteristic quantity in the best prediction model. The results show that the factors with higher occurrence frequency are the subtropical high systems in the Northern Hemisphere and the Eastern Hemisphere. Next, the subtropical high systems in East Asia also play very important roles, especially the strength and area index of the subtropical high in the western Pacific.

Abstract:Utilizing Version 3 NSIDC weekly snow cover data for the period of 1966－2005, the relationships between the increased snow cover in winter over Northern Eurasia (TFSE, Total Fresh Snow Extent) and the climate anomalies in summer (June－August) over China are investigated, which show not only the remarkable negative (positive) correlations with precipitation (temperature) in the south of the Yangtze River (SYR), but also the opposite correlations in the northeast of China. The detailed analysis reveals that: following heavy winter TFSE, there are statistically in summer an intensified anomalous low almost in the entire troposphere in the east of Baikal, an enhanced westerly jet in East Asia (EAWJ), and a strengthened subtropical high in the western Pacific (WPSH) which expands westward and northward to the SYR overhead, as well as weakened convection and vapor flux in the SYR. Under these situations, the SYR region tends to be droughty and hot, and the northeast of China tends to be cold, vice versa. The analysis also shows that the correlations between winter TFSE and summer climate anomalies in China are almost independent of ENSO and stable relatively in recent 40 years. But both the winter TFSE and rainfall in the SYR exhibit a remarkable decadal climate shift at the beginning of the 1990s, in which the winter TFSE (summer SYR rainfall) decreases (increases) obviously later than the early 1990s, and simultaneously, the correlation between winter TFSE and summer rainfall in the Huaihe River valley, just north of the Yangtze River, in China is also enhanced. Further analysis explains that winter TFSE could lead to the summer climate anomalies in China by affecting EAWJ.