Precipitation In Eastern China Research Articles

A decision‐tree approach to seasonal prediction of extreme precipitation in eastern China

AbstractSeasonal prediction of extreme precipitation has long been a challenge especially for the East Asian Summer Monsoon region, where extreme rains are often disastrous for the human society and economy. This paper introduces a decision‐tree (DT) method for predicting extreme precipitation in the rainy season over South China in April–June (SC‐AMJ) and the North China Plain in July–August (NCP‐JA). A number of preceding climate indices are adopted as predictors. In both cases, the DT models involving ENSO and NAO indices exhibit the best performance with significant skills among those with other combinations of predictors and are superior to their linear counterpart, the binary logistic regression model. The physical mechanisms for the DT results are demonstrated by composite analyses of the same DT path samples. For SC‐AMJ, an extreme season can be determined mainly via two paths: the first follows a persistent negative NAO phase in February–March; the second goes with decaying El Niño. For NCP‐JA, an extreme season can also be traced via two paths: the first is featured by “non El Niño” and an extremely negative NAO phase in the preceding winter; the second follows a shift from El Niño in the preceding winter to La Niña in the early summer. Most of the mechanisms underlying the decision rules have been documented in previous studies, while some need further studies. The present results suggest that the decision‐tree approach takes advantage of discovering and incorporating various nonlinear relationships in the climate system, hence is of great potential for improving the prediction of seasonal extreme precipitation for given regions with increasing sample observations.

Seasonal persistence of soil moisture anomalies related to freeze\u2013thaw over the Tibetan Plateau and prediction signal of summer precipitation in eastern China

Soil moisture can be an effective climate prediction signal due to its long memory. This study investigated seasonal persistence of soil moisture anomalies from the preceding autumn to spring dominated by the soil freeze–thaw (FT) process over the Tibetan Plateau (TP), and their relationship with summer precipitation in eastern China. Results demonstrated that soil moisture anomalies from the preceding autumn can persist until spring by water storage effect of the soil FT process. Soil moisture in the TP during the preceding autumn and winter had similar climatic effects as spring soil moisture. Positive soil moisture anomalies in the eastern TP during the spring led to less summer precipitation in south China and the Yellow River basin, and more summer precipitation in the Yangtze River basin and northeast China. A possible mechanism for this was that wetter soil moisture anomalies from the preceding autumn were stored in the soil by soil freezing, and were released with soil thawing in the spring, inducing surface diabatic heating anomalies over the TP. These anomalies then persisted into summer and enhanced the TP’s thermal forcing to the subtropical westerlies and affected stationary Rossby wave train propagation in middle latitudes, particularly on the northwest and northeast sides of the TP. This study suggests that most of spring soil moisture anomalies signal contains the preceding two seasons’ soil moisture anomalies information; therefore, summer precipitation predicting signals can be obtained from soil moisture anomalies from the preceding autumn, which could lengthen the seasonal climate prediction period.

Sensitivity of summer precipitation in regional spectral model simulations over eastern China to physical schemes: Daily, extreme and diurnal cycle

In this study, the capability of the National Centers for Environmental Prediction (NCEP) Regional Spectral Model (RSM) in reproducing the precipitation in eastern China is evaluated with the simulation of 25‐year (1983–2007) summertime climate driven by the NCEP‐Department of Energy reanalysis. The impacts of different physical schemes on daily precipitation, diurnal cycle and precipitation extremes are studied through detailed analyses. The results show that the RSM model can reproduce the precipitation characteristics over eastern China, and the results are sensitive to the internal model physics and spectral nudging method. The cloud water prediction scheme of CLD3 (CLDn, the cloud schemes, classified according to the complexity microphysical processes) and the modified version of the Kain‐Fritsch scheme (KF2) tend to overestimate the summer precipitation by reproducing higher humidity, while the CLD1 and the Relaxed Arakawa Schubert scheme (RAS) always underestimate it. It is also demonstrated that RSM has the capability to reproduce the spatial distributions of the extreme precipitation intensity and duration. The physical schemes have great impact on the simulations of extreme precipitation over eastern China, especially on regional scales. For the diurnal cycle of precipitation, the responses of the simulated amplitude to the physical schemes differ with regions. The RAS scheme underestimates the amplitudes over southeastern China, while the KF2 generates positive biases. The involving of the scale selective bias correction (SSBC) method can properly improve the simulated mean precipitation and diurnal cycle of summer precipitation. However, it shows lower skill in improving extreme precipitation indices over eastern China, especially in the experiments with CLD3 scheme. In summary, the selection of CLD1 and KF2 scheme, involving SSBC method performs better than the other experiments.

Influence of the strongest central Pacific El Niño–Southern Oscillation events on the precipitation in eastern China

The impact of the strongest central Pacific (CP) El Niño event 2009/2010 and CP La Niña event 1998/1999 from 1979 to 2010 on the precipitation in eastern China has been analysed. During the 2009/2010 CP El Niño event, it is rainy in northern China during maturing winter and decaying spring, but dry during decaying summer. The rainfall centre is located in south China during maturing period and gradually moves northwards, remaining over the Yellow‐Huai River valley during decaying summer. When the 1998/1999 CP La Niña event occurs, northern China is in a state of drought throughout. In south China, dry periods gradually evolve into rainy ones from maturing winter to decaying summer. The two strongest events also have notable impact on the extreme rainfall, and they mainly affect the total rainfall by influencing the extreme precipitation in eastern China. When the 2009/2010 CP El Niño event occurs, the Western Pacific Subtropical High (WPSH) is stronger with a northwards shift, and there is an obvious anticyclonic circulation near the South China Sea and Philippines. Furthermore, during decaying summer, the Pacific–Japan (PJ) wave train shows an eastwards shift comparing to the typical PJ wave train locating from low latitudes to high latitudes, associating with clearly northwardly spreading wave activity fluxes (WAFs) from the equator. When the 1998/1999 CP La Niña event occurs, the WPSH is weaker and retreats eastwards, and there is a noticeable cyclonic circulation around the South China Sea. In decaying spring, the convective activity in the South China Sea is strong, and there are correspondingly significant WAFs spreading from southeastern Asia to north. In decaying summer, northern (southern) China is controlled by anomalous anticyclones (cyclones) with weak (strong) convection, and the WAFs extend northwards to the Yangtze and Huai River valleys.

Effect of Tibetan Plateau heating on summer extreme precipitation in eastern China

The relationship between the Tibetan Plateau (TP) heating and summer extreme precipitation in eastern China is still unclear. This study shows that when the TP heating is stronger (weaker) than normal, summer extreme precipitation tends to be more (less) over the middle and lower reaches of the Yangtze River valley. The possible mechanisms responsible for the relationship between the TP heating and summer extreme precipitation in eastern China are revealed by investigating the effects of the upper-level South Asian High (SAH). It is found that positive and negative vorticity anomalies accompanied by an ascending motion anomaly occur over the TP regions in the lower and upper troposphere, respectively, when the TP heating is stronger, resulting in the strengthening and eastward extension of the SAH. As a result, an anomalous high-level convergence and downward movement occur over the southeastern portion of the SAH, which then diverge in the mid-lower troposphere, resulting in the formation of an anomalous negative vorticity from South China to the northern part of the South China Sea. Subsequently, the western Pacific subtropical high (WPSH) intensifies and stretches westward. Consequently, the southwestern moisture transport and moisture convergence increase over the middle and lower reaches of the Yangtze River valley, resulting in more extreme precipitation. The eastward extension of the SAH and westward stretching of the WPSH are maintained by the vertically inhomogeneous distribution of precipitation heating.

Simulated Interannual Teleconnection Between the Summer North Atlantic Oscillation and Summer Precipitation in Eastern China During the Last Millennium

AbstractThe interannual teleconnections between the summer North Atlantic Oscillation and summer precipitation in eastern China over the last millennium are investigated in a 1,000‐year simulation by the global climate model Community Climate System Model version 2.0.1. The model was able to roughly produce the general features of the teleconnection influences in eastern China, with negative (positive) precipitation anomalies north of 30°N and positive (negative) precipitation anomalies south of 30°N, associated with the positive (negative) phase of the North Atlantic Oscillation. The composite analysis reveals that the influence of the North Atlantic Oscillation on precipitation in summer in eastern China is chiefly via the “North Atlantic‐Eurasian teleconnection pattern,” which extends from the subtropical North Atlantic to East Asia.

Comparison of the Pacific Decadal Oscillation in climate model simulations and observations

ABSTRACTThe ability of climate models to simulate the Pacific Decadal Oscillation (PDO) and its global teleconnections is examined using the outputs of 20 Coupled Model Intercomparison Project (CMIP5) models from historical experiments. It is shown that the global warming trend is reproduced by the models, but there is a considerable difference between the models in the PDO region. The standard deviation of detrended sea surface temperature anomalies (SSTAs) in the models is similar to that of the observations, especially in the central and eastern equatorial Pacific and the North Pacific, which are the regions closely associated with the PDO and El Nino‐Southern Oscillation. The globally averaged SSTA during 1900–1940 in the CMIP5 models and observations showed large divergence, which is mainly due to the SSTA in the PDO region. The most significant cycle of the PDO indexes in most of the models had a 60–80 years period, which is different from the observed PDO period (40–60 years). However, the models perform better for the spatial pattern of the PDO, and 90% of the spatial correlations between the models and observations of the spatial pattern of the PDO are above 0.8. In addition, the models can simulate the basic correlation between the PDO and Pacific SSTA variability, but most of them overestimate the relationship in the Indian and Atlantic Oceans. The CMIP5 models are better at simulating the impact of the PDO on winter precipitation in southern North America but are less accurate in simulating summer precipitation in eastern China. This is probably because most of the models are not accurate in simulating the impacts of the PDO on the western Pacific subtropical high and the East Asian summer monsoon.

Effect of Spring Precipitation on Summer Precipitation in Eastern China: Role of Soil Moisture

The relation of spring (March–May) to summer (July–August) precipitation in eastern China is examined using observed data. It is found that when spring precipitation from the lower and middle reaches of the Yangtze River valley to northern China (the YRNC region) is higher (lower), more (less) summer precipitation occurs in northeastern China and the lower and middle reaches of the Yangtze River valley, and less (more) in southeastern China. The analysis of physical mechanism showed that higher (lower) spring precipitation in the YRNC region is closely related to wet (dry) spring soil moisture, which decreases (increases) the surface temperature and sensible heat flux in late spring. Because the memory of spring soil moisture in the YRNC region reaches about 2.4 months, the surface thermal anomaly lasts into the subsequent summer, resulting in a weak (strong) East Asian summer monsoon. A weak East Asian summer monsoon corresponds to an anomalous anticyclone and a cyclone over southeastern and northeastern China, respectively, in the lower troposphere. The anomalous anticyclone depresses the summer precipitation in southeastern China, and the anomalous cyclone promotes precipitation over northeastern China. The abnormal northerly and southerly winds associated with the anomalous cyclone and anticyclone, respectively, converge in the lower and middle reaches of the Yangtze River valley, inducing more summer precipitation there.

The three-dimension intensity index for western Pacific subtropical high and its link to the anomaly of rain belt in eastern China

Western Pacific subtropical high (WPSH) is a deep circulation system located at middle-lower troposphere over the East Asia. The anomalies of its position and intensity determine the shift of climates in eastern China, especially the summer rainfall belt. However, previous definitions of WPSH intensity index were limited mainly by a single threshold of 5880-gpm geopotential height contour at 500-hPa, which cannot denote the rain pattern in eastern China reasonably, in particular the floods and droughts along the Yangtze River valley. In this paper, the link between the intensity of East Asian summer monsoon (EASM) and the geopotential heights at each level were analyzed by correlation analyses. The results indicate that the significant negative correlations spread obviously from the upper to lower levels with longitude changed from west to east. At the upper levels over the Asian continent, the most significant negative correlation was found at the central region of the South Asia High (SAH). This implies that the EASM would be weaker if the SAH was stronger, and vice versa. Over the western Pacific warm pool, the most significant negative correlation was found in the middle-lower troposphere. The correlation coefficients at 500-hPa were much weaker than those at 700-hPa and 850-hPa, indicating that the EASM was easier influenced by the subtropical high at lower levels. Similar, the relationship between the WPSH and the precipitation along the Yangtze River valley was more significant at lower levels indicated by the correlation coefficient. In this study, the representativeness of the threshold of 5880 gpm at 500-hPa level over the western Pacific subtropical regions was analyzed at different grids and seasons, and the limitations of previous definitions were also discussed. Considering the three-dimension (3D) structures of the subtropical high, a new WPSH intensity index was defined by integrated the standardized geopotential heights from 500-hPa to 1000-hPa levels over the region (10°–30°N, 110°–150°E). Compared with the two traditional WPSH indices, the new 3D WPSH intensity index can better represent the subtropical summer monsoon and the precipitation along the middle and lower reaches of the Yangtze River. Although all the three indices could reflect the primary correlation patterns between WPSH and the precipitation in eastern China, only the correlation coefficient between the 3D intensity index and precipitation is significant at the 95% confidence level to pass the student t -test. Compared to the other two indices, the 3D WPSH index can better reflect the anomalous of both meridional and zonal water vapor transportation between the tropical and subtropical regions of East Asia. During the transition seasons of boreal spring and autumn, the mechanisms of anomalous precipitation are more complicated, which are obviously different from EASM. Preliminary analysis shows that even in these two transition seasons, the 3D WPSH index defined in this paper also has better link with the precipitation anomalies in eastern China. As mentioned before, the WPSH is a deep circulation system over the western Pacific. Besides its intensity, the position also impacts on the climates over East Asia, especially its west boundary and meridional axis. In the future study, the definitions of other parameters of WPSH need to be studied from its 3D structure.

Summer extreme precipitation in eastern China: Mechanisms and impacts

AbstractWith the highest population density in China, eastern China has an unshakable position in Chinese socioeconomic development. To understand the precipitation changes and the related mechanisms is of great significance for regional management of water resources and agricultural irrigation. In this study, the impacts of western North Pacific subtropical high (WNPSH) on precipitation changes in eastern China and the underlying processes are investigated. The results indicate that the strength and location of WNPSH are in close relations with the changes of summer precipitation in eastern China, and their influences vary across both space and time. In particular, WNPSH exerts remarkable impacts on precipitation in June and July in Jiang‐Huai region and precipitation in June in South China such as the Pearl River basin. The interannual variations of WNPSH exhibit significant correlations with water vapor flux in East Asia, and the variations of the location and direction of the west flank of the WNPSH are well corroborated with the influences of the East Asian summer monsoon (EASM) on precipitation in eastern China. The westward extension of WNPSH tends to favor the strong moisture transport to East Asia, intensify the EASM, and thus increase water vapor flux in East Asia, which greatly benefits the occurrence of Meiyu regimes in Jiang‐Huai region. Besides, analysis results also show that the westward extension of WNPSH drives tropical cyclones southward so as to increase the occurrence of extreme precipitation in South China. This study helps to bridge the knowledge gap in the relationship between WNPSH, tropical cyclones, and summer precipitation events in eastern China.

Impacts of Spatiotemporal Anomalies of Tibetan Plateau Snow Cover on Summer Precipitation in Eastern China

Abstract Tibetan Plateau (TP) snow cover undergoes significant temporal and spatial variations during the winter and spring months. This study investigates the relationship between the spatiotemporal distribution of winter–spring snow cover (SC) over the TP and summer precipitation in eastern China (EC) using the singular value decomposition (SVD) method. Four simulation experiments are designed to validate the results of SVD analysis. Both observations and simulations show that heavier snow cover in the southern TP leads to more rainfall in the Yangtze River basin and northeastern China, and less precipitation in southern China, whereas heavier snow cover in the northern TP results in enhanced rainfall in southeastern and northern China and weakened precipitation in the Yangtze River basin. The linkage is attributed to anomalous westerly winds in the upper troposphere at around 200 hPa and to changes of the southern branch of westerlies at 500 hPa on the south side of the TP, which are caused by lasting diabatic heat anomalies over the TP. The shifts in position of the westerly jet at the exit region and negative anomalies of geopotential height at 500 hPa further result in anomalous anticyclone over the East China Sea and the corresponding 850-hPa water vapor convergence and influence the anomalous summer precipitation belt in EC.

Application of the Doppler weather radar in real-time quality control of hourly gauge precipitation in eastern China

The current real-time operational quality control method for hourly rain gauge records at meteorological stations of China is primarily based on a comparison with historical extreme records, and the spatial and temporal consistencies of rain records. However, this method might make erroneous judgments for heavy precipitation because of its remarkable inhomogeneous features. In this study, we develop a Radar Supported Operational Real-time Quality Control (RS_ORQC) method to improve hourly gauge precipitation records in eastern China by using Doppler weather radar data and national automatic rain-gauge network in JJA (i.e., June, July and August) between 2010 and 2011. According to the probability density function (PDF) and cumulative probability density function (CDF), we establish the statistic relationships between NSN precipitation records under 7 radar coverage and radar quantitative precipitation estimation (QPE). The other NSN records under 5 radar coverage are used for the verification. The results show that the correct rate of this radar-supported new method in judging gauge precipitation is close to 99.95% when the hourly rainfall rate is below 10mmh−1 and is 96.21% when the rainfall intensity is above 10mmh−1. Moreover, the improved quality control method is also applied to evaluate the quality of provincial station network (PSN) precipitation records over eastern China. The correct rate of PSN precipitation records is 99.92% when the hourly rainfall rate is below 10mmh−1, and it is 93.33% when the hourly rainfall rate is above 10mmh−1. Case studies also exhibit that the radar-supported method can make correct judgments for extreme heavy rainfall.

Multimodel ensemble projection of precipitation in eastern China under A1B emission scenario

AbstractAs part of the Regional Climate Model Intercomparison Project for Asia, future precipitation projection in China is constructed using five regional climate models (RCMs) driven by the same global climate model (GCM) of European Centre/Hamburg version 5. The simulations cover both the control climate (1978–2000) and future projection (2041–2070) under the Intergovernmental Panel on Climate Change emission scenario A1B. For the control climate, the RCMs have an advantage over the driving GCM in reproducing the summer mean precipitation distribution and the annual cycle. The biases in simulating summer precipitation mainly are caused by the deficiencies in reproducing the low‐level circulation, such as the western Pacific subtropical high. In addition, large inter‐RCM differences exist in the summer precipitation simulations. For the future climate, consistent and inconsistent changes in precipitation between the driving GCM and the nested RCMs are observed. Similar changes in summer precipitation are projected by RCMs over western China, but model behaviors are quite different over eastern China, which is dominated by the Asian monsoon system. The inter‐RCM difference of rainfall changes is more pronounced in spring over eastern China. North China and the southern part of South China are very likely to experience less summer rainfall in multi‐RCM mean (MRM) projection, while limited credibility in increased summer rainfall MRM projection over the lower reaches of the Yangtze River Basin. The inter‐RCM variability is the main contributor to the total uncertainty for the lower reaches of the Yangtze River Basin and South China during 2041–2060, while lowest for Northeast China, being less than 40%.

Changing characteristics of precipitation in China during 1960–2012

ABSTRACTIn this study, we investigated changes in the precipitation characteristics for China from 1960 to 2012 based on a recent daily precipitation dataset of 666 climate stations and robust non‐parametric trend detection techniques. We divided all precipitation events into four non‐overlapping categories: light, moderate, heavy and very heavy based on percentile thresholds. We then established the trends for annual total and precipitation of different intensity categories, and examined their regional and seasonal variations. The results show that there was little change in annual total precipitation for entire China, but distinctive regional patterns existed. In general, precipitation increased in the west and decreased in east. Precipitation of different intensities, in general, changed in the same direction as the mean, but heavy and very heavy precipitation events had higher rates of change than mean precipitation. The exception was the southeast region, where despite the slight decrease in mean precipitation, heavy and very heavy precipitation still increased significantly. In addition, we used multiple regression models to explore the contribution of changes of frequency and intensity to total precipitation change, and the contributions of changes of precipitation at different intensities to total precipitation change. For western China, total precipitation change was associated more with frequency change, whereas in eastern China intensity contributed more. For precipitation amount, moderate, heavy and very heavy precipitations contributed to the total change, with little contribution from light precipitation change. For frequency, changes in light and moderate precipitation frequencies dominated the total change, with very little contributions from heavy and very heavy precipitation frequency changes. In addition, we examined the linkage between summer precipitation in eastern China and the East‐Asian Summer Monsoon (EASM), found that the northern decrease and southern increase in summer precipitation was likely caused by the weakening of EASM over the study period.

Air pollution or global warming: Attribution of extreme precipitation changes in eastern China—Comments on “Trends of extreme precipitation in Eastern China and their possible causes”

The recent study “Trends of Extreme Precipitation in Eastern China and Their Possible Causes” attributed the observed decrease/increase of light/heavy precipitation in eastern China to global warming rather than the regional aerosol effects. However, there exist compelling evidence from previous long-term observations and numerical modeling studies, suggesting that anthropogenic pollution is closely linked to the recent changes in precipitation intensity because of considerably modulated cloud physical properties by aerosols in eastern China. Clearly, a quantitative assessment of the aerosol and greenhouse effects on the regional scale is required to identify the primary cause for the extreme precipitation changes.

Response to comments by Yuan Wang on “Trends of extreme precipitation in Eastern China and their possible causes”

In his comments, Wang cites a number of works to dispute the conclusion in our previous work, which attributes the observed decreases/increases in light/heavy precipitation in eastern China primarily to global warming rather than the regional aerosol effect. However, most of the cited works (admittedly, including our previous work), employ correlation analysis, which has little bearing on the cause–effect relationship. Theoretical analyses and/or modeling studies are needed to ascertain the cause–effect relationship. We argue that theoretical analyses and modeling results show that global warming is the primary cause of the widely observed phenomena of suppression of light precipitation and enhancement of heavy precipitation across the globe, including in eastern China.

Trends of extreme precipitation in eastern China and their possible causes

Significant increases of heavy precipitation and decreases of light precipitation have been reported over widespread regions of the globe. Global warming and effects of anthropogenic aerosols have both been proposed as possible causes of these changes. We examine data from urban and rural meteorological stations in eastern China (1955–2011) and compare them with Global Precipitation Climatology Project (GPCP) data (1979–2007) and reanalysis data in various latitude zones to study changes in precipitation extremes. Significant decreases in light precipitation and increases in heavy precipitation are found at both rural and urban stations, as well as low latitudes over the ocean, while total precipitation shows little change. Characteristics of these changes and changes in the equatorial zone and other latitudes suggest that global warming rather than aerosol effects is the primary cause of the changes. In eastern China, increases of annual total dry days (28 days) and ≥10 consecutive dry days (36%) are due to the decrease in light precipitation days, thereby establishing a causal link among global warming, changes in precipitation extremes, and higher meteorological risk of floods and droughts. Further, results derived from the GPCP data and reanalysis data suggest that the causal link exists over widespread regions of the globe.

RegCM4.0对一个全球模式20世纪气候变化试验的中国区域降尺度:温室气体和自然变率的贡献

China has experienced warming and a pattern of southern flood and northern drought in precipitation in recent decades. Attributable contributions of greenhouse gas emissions and natural climate variability to these phenomena are discussed for China and the main hydrological basins, based on a comparison of historical and attribution simulation tests using a regional climate model (RegCM4.0). Two tests are performed at a resolution of 50 km, driven by the results of BCC_CSM1.1 historical and attribution simulation tests of CMIP5 in 1961-2005, respectively. The forcing of greenhouse gas emissions and natural climate variability are included in the historical test, and greenhouse gas emission is excluded in the attribution test. Results show that the simulated trends of temperature and precipitation from RegCM4.0 are more reasonable than from BCC_CSM1.1 for 1961-2005, and the warming during this period was mainly caused by the emission of greenhouse gases, although natural climate variability also led to regional warming in most areas except the Tibetan Plateau. The warming magnitude from greenhouse gas emissions was much larger than from natural climate variability over most basins and China as a whole, with 80% of the warming attributable to forcing by greenhouse gases. The southern flood and northern drought pattern of precipitation in Eastern China may be largely due to natural climate variability, and greenhouse gas emission to some extent weakens the strength of this change; increased precipitation in Northwest China is mainly induced by increased greenhouse gas emission, while natural climate variability, in contrast, leads to reduced precipitation. The assessments of temperature are more reliable than those of precipitation, because model limitations and the complex relationship between precipitation and external factors result in large remaining uncertainties in precipitation assessments. It should be pointed out that attribution studies of climate change on the regional scale are very complex, and only preliminary modeling results of aerosol and land use forcing in the absence are shown in this study. An ensemble of multiple models and samples with statistical significance and confidence is needed for comprehensive detection and attribution studies, and the limitations associated with all these factors lead to large uncertainties in the conclusions. The aim of this study is to provide a detection and attribution method for studying regional climate change. A more comprehensive and accurate understanding of the causes of climate change in China would require further regional climate simulations and analyses.

Interannual variability of autumn to spring seasonal precipitation in eastern China

The interannual variability of seasonal precipitation in eastern China from fall to following spring is examined for the period of 1951–2004 based on observations at 106 stations. The temporal variability of seasonal mean values is decomposed into intraseasonal (fast) and slow (potentially predictable) components. EOF analysis is then applied to both the fast and predictable components. We find that (1) the most predictable signal migrates in a north–south direction along with the annual cycle of the monsoon in east China, while spatial patterns of the leading fast modes does not change much; (2) the predictable signal of precipitation in eastern China is associated with anomalous atmospheric circulation patterns having more zonally symmetric structures while the fast time-varying precipitation components are accompanied by wavy anomalous atmospheric circulation patterns; (3) the most predictable signal has an apparent 1-season lagged correlation with the interannual variation of sea surface temperature associated with El Nino/Southern Oscillation; (4) The fast rainfall component is largely attributed to the intraseasonal variabilities of the Siberian High over the Eurasian continent and the subtropical high associated with the Western-Pacific-Oscillation-like variabilities over the North Pacific; and (5) The ENSO signal in the fall seasonal precipitation persisted throughout the entire 54-year period while the signal in winter intensified significantly after the mid-1970s. This is attributed to the weaker/stronger intensification of ENSO anomalies in the tropical Pacific during the fall/winter.

The possible influence of tropical Pacific subsurface temperature anomalies on summer precipitation in eastern China

Using NCEP (National Centers for Environmental Prediction) GODAS (Global Ocean Data Assimilation System) monthly subsurface temperature (SsT) from 1980 to 2009, a 3-D four-step model was established to categorize the SsT interannual variations in the tropical Pacific. In combination with NCEP/National Center for Atmospheric Research (NCAR) reanalysis 850-hPa wind field and 160 stations' precipitation data in China, an intimate connection between the tropical Pacific SsT and eastern China summer precipitation anomalies is discovered by examining the time-lagged and simultaneous correlations among the interannual anomalies of SsT in the tropical Pacific, the 850-hPa wind pattern and summer rainfall in China. In previous winter, if the SsT in the tropical Pacific indicates an El Niño-type anomaly, an anticyclonic circulation anomaly over the East Asian coast, South China Sea and east of Taiwan along with a cyclonic circulation anomaly over the Japanese archipelago emerges in following summer. At the same time, a cyclonic circulation and an anticyclonic circulation prevail over the Lake Baikal and Kuril Islands in the high latitude. These combined circulation patterns facilitate the southward transport of cold air from high latitude and northward transport of warm and moist air through the western edge of the subtropical high. The meet between two air masses results in significantly abundant anomalous precipitation in the Sichuan Basin, Dongting and Poyang Lake Basin, and possibly deficit precipitation occurs over the Hetao region and lower Yellow River Basin, northern Zhejiang, as well as the coastal region of southern China and southern Yunnan. These findings offer a very useful predictive power for eastern China summer precipitation based on tropical Pacific SsT status in previous winter and subsequent developments of SsT and East Asian large-scale circulations.