Chen S.,Jiangsu Meteorological Observatory |
He J.,Key Laboratory of Meteorological Disaster of NUIST
Haiyang Xuebao | Year: 2017
Different decaying characteristics for two types of El Niño and their relationships with the summer rainfall in China were investigated by using 743 stations daily precipitation data from China Meteorological Administration, NCEP circulation reanalysis datasets and the monthly mean Met Office Hadley Center sea surface temperature (SST) analyses data. Based on the evolution of the SST anomalies (SSTA) across the equator(5°S-5°N), two types of decaying patterns are identified for EP-El Niño:(1) An evolution pattern that SSTA decaying from east to west (E-W). The positive SSTA larger than 0.5°C first disappear in offshore of South America and the disappearance extends to the west. (2) An evolution pattern that SSTA decaying from west to east (W-E). The positive SSTA larger than 0.5°C first disappear in the central Pacific and the disappearance extends to the east. The decaying evolution of CP-El Niño is classified into three patterns:(1) A symmetric (S)-decaying pattern whose SSTA grows and decays symmetrically with respect to a peak phase, (2) A prolonged(P)-decaying pattern that is followed by a EP-El Niño type, (3) An abrupt(A)-decaying pattern that is followed by a EP-La Niña type. In the following summer of EP-El Niño in two different decaying patterns, there are almost completely opposite rainfall anomalies in North China, South China, the region between and the upstream area of the Yangtze River and the Yellow River Valley (they are called the Two River for short). In the following summer for E-W pattern, suppressed rainfall appears in the region between and the upstream area of the Two River, while the rainfall in North China is abundant and rainfall of the area to the south of the Yangtze River is slightly more. However, there are significantly positive anomalies in the region between and the upstream area of the Two River with the center of positive anomalies located along the Yangtze River, but the negative rainfall anomalies in most region of South China and North China for W-E pattern. As for three decaying patterns of CP-El Niño, the positive anomalies are present in the region between the Huaihe River and the Yellow River Valley for S pattern, in the Yangtze River Valley for P pattern, while in the lower reaches of the Yellow River for A pattern. Rainfall in the Northeast China, especially in the northern of Northeast China, is below normal for S and A pattern, while above normal for P pattern. In the Southwest China, wet (dry) signal appears for S (A) pattern. And in the northern of Northwest China,there is less (more) precipitation for A pattern (S and P pattern). Different distribution of summer rainfall anomalies in the decaying phase of El Niño is closely associated with their different decaying patterns. When inspecting the impacts of the two types of El Niño on the following summer rainfall, it would be better to consider their different decaying patterns in view of the larger significant area and T-inspection value of rainfall anomalies. All these will provide important reference for the short-term climate prediction of summer rainfall. © 2017, Editorial Office of Haiyang Xuebao. All rights reserved.
Tang J.,Nanjing University |
Wang S.,Nanjing University |
Niu X.,Nanjing University |
Hui P.,Jiangsu Climate Center |
And 2 more authors.
Climate Dynamics | Year: 2017
In this study, the impact of the spectral nudging method on regional climate simulation over the Coordinated Regional Climate Downscaling Experiment East Asia (CORDEX-EA) region is investigated using the Weather Research and Forecasting model (WRF). Driven by the ERA-Interim reanalysis, five continuous simulations covering 1989–2007 are conducted by the WRF model, in which four runs adopt the interior spectral nudging with different wavenumbers, nudging variables and nudging coefficients. Model validation shows that WRF has the ability to simulate spatial distributions and temporal variations of the surface climate (air temperature and precipitation) over CORDEX-EA domain. Comparably the spectral nudging technique is effective in improving the model’s skill in the following aspects: (1), the simulated biases and root mean square errors of annual mean temperature and precipitation are obviously reduced. The SN3-UVT (spectral nudging with wavenumber 3 in both zonal and meridional directions applied to U, V and T) and SN6 (spectral nudging with wavenumber 6 in both zonal and meridional directions applied to U and V) experiments give the best simulations for temperature and precipitation respectively. The inter-annual and seasonal variances produced by the SN experiments are also closer to the ERA-Interim observation. (2), the application of spectral nudging in WRF is helpful for simulating the extreme temperature and precipitation, and the SN3-UVT simulation shows a clear advantage over the other simulations in depicting both the spatial distributions and inter-annual variances of temperature and precipitation extremes. With the spectral nudging, WRF is able to preserve the variability in the large scale climate information, and therefore adjust the temperature and precipitation variabilities toward the observation. © 2016, Springer-Verlag Berlin Heidelberg.
Liu D.,Jiangsu Meteorological Observatory |
Li Z.,Nanjing University of Information Science and Technology |
Yan W.,Jiangsu Meteorological Observatory |
Li Y.,Colorado State University
Asia-Pacific Journal of Atmospheric Sciences | Year: 2017
Fog microphysical research in China based on field experiments obtained many important results in recent 50 years. With the fast development of China’s economy, urbanization in the last 30 years, special features of fog microphysical structure also appeared, which did not appear in other countries. This article reviews the fog microphysical research around China, and introduces the effect of urbanization on fog microphysical structure and the microphysical processes as well as macroscopic conditions of radiation fog droplet spectral broadening. Urbanization led to an increase in fog droplet number concentration but decreases in fog liquid water content (LWC) and fog droplet size, as well as a decrease in visibility in large cities. Observations show that the radiation fog could be divided into wide-spectrum one, which is all extremely dense fog with the spectral width more than 40 μm, and narrow-spectrum one, most of which is dense fog with the spectral width less than 22 μm, according to droplet spectral distribution. During developing from dense fog to extremely dense fog, the widespectrum radiation fog is characterized by explosive deepening, that is, within a very short time (about 30 min), the droplet concentration increase by about one order of magnitude, droplet spectral broadening across 20 μm, generally up to 30-40 μm, or even 50 μm. As a result, water content increased obviously, visibility decreased to less than 50 m, when dense fog became extremely dense fog. © 2017, Korean Meteorological Society and Springer Science+Business Media Dordrecht.
Gao Y.,Nanjing University of Information Science and Technology |
Chen Y.,Nanjing University of Information Science and Technology |
Jiang Y.,Jiangsu Meteorological Observatory |
Peng T.,Institute of Heavy Rain
Shuikexue Jinzhan/Advances in Water Science | Year: 2015
Hydrological simulations are affected by the parameters derived from DEM, which describes the water-shed features. Xitiaoxi River basin was selected to simulate two runoff processes in Jun and Aug to Sep 2011 using the HEC-HMS model with ASTER 30 m DEM, SRTM 90 m DEM and DEM resample data as input for HEC-geoHMS to derive the basin characteristics. The results showed that, the simulated and observed flood were fitting well and the efficiency coefficients of the model were all larger than 0.82, Uni-modal flood showed a better performance in runoff simulation than multi-modal flood. The efficiency coefficients of model based on SRTM 90 m was larger than based on ASTER 30 m DEM and resampled 90 m DEM. The efficiency coefficients of model based on resampled DEM had nonlinear relationship with DEM resolution. The relative error of HEC-HMS simulations based on ASTER 30 m DEM and SRTM 90 m DEM had a difference of 3%-5%. The relative error of simulations based on the SRTM 90 m DEM and the resampled 90 m DEM had a difference of 2%-4%. The maximum difference between the relative error of HEC-HMS simulations based on the resampled 90 m DEM was 11%. ©, 2015, Science Press. All right reserved.
Liu D.Y.,Jiangsu Meteorological Observatory |
Yan W.L.,Jiangsu Meteorological Observatory |
Yang J.,Nanjing University of Information Science and Technology |
Pu M.J.,Jiangsu Meteorological Observatory |
And 2 more authors.
Boundary-Layer Meteorology | Year: 2015
A large quantity of advection fog appeared in the Yangtze River delta region between 1 and 2 December 2009. Here, we detail the fog formation and dissipation processes and the background weather conditions. The fog boundary layer and its formation and dissipation mechanisms have also been analyzed using field data recorded in a northern suburb of Nanjing. The results showed the following: (1) This advection fog was generated by interaction between advection of a north-east cold ground layer and a south-east warm upper layer. The double-inversion structure generated by this interaction between the cold and warm advections and steady south-east vapour transport was the main cause of this long-lasting fog. The double-inversion structure provided good thermal conditions for the thick fog, and the south-east vapour transport was not only conducive to maintaining the thickness of the fog but also sustained its long duration. (2) The fog-top altitude was over 600 m for most of the time, and the fog reduced visibility to less than 100 m for approximately 12 h. (3) The low-level jet near the lower inversion layer also played a role in maintaining the thick fog system by promoting heat, momentum and south-east vapour transport. © 2015 Springer Science+Business Media Dordrecht
Wei J.,Nanjing University of Information Science and Technology |
Wei J.,Jiangsu Meteorological Observatory |
Zhu W.,Nanjing University of Information Science and Technology |
Liu D.,Jiangsu Meteorological Observatory |
Han X.,Suzhou Meteorological Observatory of Jiangsu Province
Advances in Meteorology | Year: 2016
Based on the surface meteorological data of Jiangsu Province during 1980-2012, the climatic characteristics and the trends of haze were analyzed. The results indicated that during 1980-2012 haze days increased; in particular, severe and moderate haze days significantly increased. In the northern and coastal cities of Jiangsu Province China, haze days showed a significant increase. Haze often appeared in fall and winter and rarely in summer in the study area. It also occurred more often inland, and less along the coast. Haze occurred more often in June due to straw burning in the harvest time. The haze day increased during the 1990s over southern and southwestern Jiangsu Province; in central and northern Jiangsu, haze day increased after 2000. The continuous, regional, and regional continuous haze days all showed increasing trends. As the urban area expanded each year, industrial emissions, coal consumption, and car ownership increased accordingly, resulting in regional temperature increase and relative humidity decrease, which formed the urban heat island and dry island effects. Hence, haze formation and maintenance conditions became more favorable for more haze days, which led to the increase of haze days, and the significant increases of continuous, regional, and regional continuous haze days. © 2016 Jiansu Wei et al.
Wu Z.,Nanjing University of Information Science and Technology |
Chen S.,Jiangsu Meteorological Observatory |
He J.,Nanjing University of Information Science and Technology |
Chen H.,Nanjing University of Information Science and Technology
Atmosphere - Ocean | Year: 2014
The sea surface temperature (SST) or sea level pressure (SLP) has usually been used to measure the strength of El Niño-Southern Oscillation (ENSO) events. In this study, two new indices, based on the upper-ocean heat content (HC), are proposed to quantify the two "flavours" of El Niño (i.e., the Cold Tongue El Niño (CTE) and Warm Pool El Niño (WPE)). Compared with traditional SST or SLP indices, the new HC-based indices can distinguish CTE and WPE events much better and also represent the two leading modes of the interannual variability of the atmosphere-ocean coupled system in the tropical Indo-Pacific region. The two leading modes are obtained by performing multivariate Empirical Orthogonal Function analysis on two oceanic variables (SST and HC) over the tropical Pacific (30°S-30°N, 120°E-80°W) and six atmospheric variables (outgoing longwave radiation, SLP, streamfunction, and velocity potential at 850 hPa and 200 hPa) over the tropical Indo-Pacific region (30°S-30°N, 60°E-80°W) for the period 1980-2010. Because the two new HC-based indices are capable of better depicting coherent variations between the ocean and atmosphere, they can provide a supplementary tool for ENSO monitoring of and climate research into the two flavours of El Niño. © 2014 Taylor & Francis.
Hou J.,Nanjing University of Information Science and Technology |
Hou J.,Jiangsu Meteorological Observatory |
Guan Z.,Nanjing University of Information Science and Technology
Acta Meteorologica Sinica | Year: 2013
Based on daily precipitation data from 212 stations in East China and NCEP/NCAR daily global final analysis data in June and July from 2000 to 2010, the climatological characteristics of frontogenesis and related circulations have been analyzed. The results demonstrate that frontogenesis function distributes non-uniformly in East China. The different terms of the kinematic frontogenesis show different intensities and distributions of frontogenesis. The strongest frontogenesis integrated from different kinematic frontogenesis terms is observed in the Jianghuai area. Frontogenesis events are separated into four types as per the different shear and convergence types of horizontal wind along the strong frontogenesis band at 850 hPa. The four types include the warm shear type, cold shear type (with two subtypes), west wind convergence type, and east wind convergence type. The events in different frontogenesis types occur with different frequencies over the past decade. The warm shear type occurs most frequently. Different types of frontogenesis have distinctive horizontal and vertical structures. Strong frontogenesis is featured with 340-K contour of θ se parallel to the frontal zone in the vertical. Varied large-scale circulation patterns manifested in shifted location and strength of cyclone or anticyclone, wind convergence, as well as vertical circulation structure are associated with different types of frontogenesis. Moreover, a strong positive correlation between frontogenesis and precipitation is found, i.e., the stronger the frontogenesis, the more precipitation there is. Daily precipitation related to the warm shear type frontogenesis is the largest, and often occurs inside the frontal zone with the same orientation with the strong frontogenesis belt. The second largest daily precipitation occurs with the cold shear type frontogenesis, and related rainfall is usually observed to the south of the frontal zone, with the rain belt extending northeastward. Precipitation related to the west wind convergence type frontogenesis is the third largest, occurring mostly in the south of the frontal zone. © 2013 The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg.
Yan S.,Jiangsu Meteorological Observatory |
Peishu Z.,Jiangsu Meteorological Observatory
2012 IEEE 5th International Conference on Advanced Computational Intelligence, ICACI 2012 | Year: 2012
An attempt is made to find the regional precipitation characteristics during the Meiyu period in Jiangsu province. Derived from layered cluster analysis, the Jiangsu province is divided into three regions: Region 1, the northern Huaihe Area; Region 2, regions along Huaihe River and between Huaihe River and Yangtze River; Region 3, regions along Yangtze River and the southern region of Jiangsu province. The dataset used consists of records of daily precipitation from 66 meteorological stations over Jiangsu province during 49 yr (1961-2009). Using Morlet wavelet, binomial moving average method and composite analysis, we found that: 1. the precipitation anomaly shows different inter-annual and inter-decadal characteristics in the three regions during the Meiyu period. The 2 yr and 4 yr oscillation cycle exhibits after the 1980s, and the 6 yr oscillation cycle exhibits in the late 1980s and the middle 1990s over the most area to the south of Huaihe River. While in the northern Huaihe Area, the oscillation cycles were 7 yr, 4 yr, and 3yr. Although precipitation anomaly is different from the regions, there is a strong positive correlation between precipitation index I in Jiangsu province and that in the 3 regions, respectively. Besides, the Region 2 and Region 3 showed the lowest correlation among those of different regions. © 2012 IEEE.
Su T.,CAS Institute of Atmospheric Physics |
Su T.,Fujian Meteorological Observatory |
Xue F.,CAS Institute of Atmospheric Physics |
Sun H.,Jiangsu Meteorological Observatory |
Zhou G.,CAS Institute of Atmospheric Physics
Acta Oceanologica Sinica | Year: 2015
On the basis of more than 200-year control run, the performance of the climate system model of Chinese Academy of Sciences (CAS-ESM-C) in simulating the El Niño-Southern Oscillation (ENSO) cycle is evaluated, including the onset, development and decay of the ENSO. It is shown that, the model can reasonably simulate the annual cycle and interannual variability of sea surface temperature (SST) in the tropical Pacific, as well as the seasonal phase-locking of the ENSO. The model also captures two prerequisites for the El Niño onset, i.e., a westerly anomaly and a warm SST anomaly in the equatorial western Pacific. Owing to too strong forcing from an extratropical meridional wind, however, the westerly anomaly in this region is largely overestimated. Moreover, the simulated thermocline is much shallower with a weaker slope. As a result, the warm SST anomaly from the western Pacific propagates eastward more quickly, leading to a faster development of an El Niño. During the decay stage, owing to a stronger El Niño in the model, the secondary Gill-type response of the tropical atmosphere to the eastern Pacific warming is much stronger, thereby resulting in a persistent easterly anomaly in the western Pacific. Meanwhile, a cold anomaly in the warm pool appears as a result of a lifted thermocline via Ekman pumping. Finally, an El Niño decays into a La Niña through their interactions. In addition, the shorter period and larger amplitude of the ENSO in the model can be attributed to a shallower thermocline in the equatorial Pacific, which speeds up the zonal redistribution of a heat content in the upper ocean. © 2015, The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg.