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Wang C.,Shanxi Meteorological Observatory | Wang C.,PLA University of Science and Technology | Fei J.,PLA University of Science and Technology | Ding J.,PLA University of Science and Technology | And 3 more authors.
Ocean Engineering | Year: 2017

Ocean waves generally mix with wind waves and swell, of which only wind waves depend on the local wind field. Using 15 years of hourly observational wind-wave data from eight buoys off the northwest coast of the United States (US), the authors develop a new significant wave height (Hs) and dominant wave period (Tp) scheme (termed as WHP) for open oceans. This scheme relies only on the properties that a single atmospheric model can provide: Hs=0.0143U10 2+0.9626,H*=0.0628T*3/2 where U10 is the wind speed at a reference height of 10 m, H* is the dimensionless wave height, and T* is the dimensionless wave period. This relation is fitted to U10 values between 4 and 25 m s−1. Comparison results show that the WHP scheme gives an almost best performance in predicting Hs and Tp for the open oceans across different regions. In addition to wind speed, considering the influence of wind direction and stability of the air/sea boundary layer is necessary for wind-wave prediction in coastal areas. Data from the Coupled Boundary Layers and Air–Sea Transfer experiment in LOW winds (CBLAST-LOW) and coastal buoys demonstrate that the effects of the wind direction and stability on Hs and Tp are significant for shallow water; with an increase in water depth, such impacts gradually decrease. Parameterizations for coastal wind waves are also investigated in this paper in Eqs. (19)–(31). © 2017 Elsevier Ltd

Zhong L.,Chinese Academy of Meteorological Sciences | Mu R.,Chongqing Meteorological Bureau | Zhang D.,University of Maryland University College | Zhao P.,Chinese Academy of Meteorological Sciences | And 2 more authors.
Journal of Geophysical Research D: Atmospheres | Year: 2015

An observational analysis of the multiscale processes leading to the extreme rainfall event in Beijing on 21 July 2012 is performed using rain gauge records, Doppler radar, and satellite products, radiosondes, and atmospheric analysis. This rainstorm process included two heavy rainfall stages in the early afternoon [1300-1400 Beijing Standard time (BST) (0500-0600 UTC)] and the evening (1600-1900 BST), respectively. The first stage exhibited warm-sector rainfall characteristics as it occurred under low-level warm and moist southeasterly flows ahead of a synoptic-scale vortex and a cold front. When the southeasterly flows turned northeastward along a southwest-northeast oriented mountain range in western Beijing, mesoscale convergence centers formed on the windward side of the mountain range in the early afternoon, initiating moist convection. Radar echo showed a northeastward propagation as these flows extended northward. Despite the shallowness of moist convection in the warm sector, atmospheric liquid water content showed the rapid accumulation, and a large amount of supercooled water and/or ice particles was possibly accumulated above the melting level. These appeared to contribute to the occurrence of the largest rainfall rate. During the second stage, as the synoptic-scale vortex moved across Beijing, with southeastward intrusion of its northwesterly flows, the vortex-associated lifting caused the generation of strong updrafts aloft and formed deep convection. This facilitated the further accumulation of supercooled water and/or ice particles above the melting level. Radar echo propagated southeastward. Liquid water showed a decrease in the lower troposphere, and there were strong downdrafts due to evaporation of liquid water particles, which resulted in the relatively weak hourly rainfall rates. Key Points We compare differences between warm-sector and vortex rainstorms in north China High-resolution rain gauge and Doppler radar data are used in mesoscale analysis Shallow convection produces heavy rainfall in warm sector with much liquid water © 2015. The Authors.

Dong C.-Q.,Nanjing University of Information Science and Technology | Dong C.-Q.,Shanxi Meteorological Observatory | Zheng Y.-F.,Nanjing University of Information Science and Technology | Wu Y.-L.,Shanxi Meteorological Observatory | And 2 more authors.
Zhongguo Huanjing Kexue/China Environmental Science | Year: 2016

Adequate air quality modeling is reliant on accurate meteorological simulation especially in the planetary boundary layer (PBL). To further understand how the boundary layer processes affect the mixing and transmission of air pollutants, the sensitivity tests of WRF-Chem model with different PBL schemes were utilized. Surface temperature, wind field, PM2.5 concentration, dynamic and thermal PBL stratification were simulated in the typical winter stable weather condition of Shanxi province, and the results were compared with the observational data. The simulation ability of different schemes were analyzed, and the effects of PBL thermal stratification and turbulent transportation differences on PM2.5 concentration simulation were discussed. The results indicated that both of the two schemes could simulate the spatial distribution and diurnal variation characteristics of surface temperature, wind speed, and PM2.5 concentration in the winter stable weather. The relatively larger error of temperature simulated normally occurred at night, while the simulation error of surface wind speed and PM2.5 concentration mainly appeared in the afternoon. Surface temperature, wind field and PM2.5 concentration simulated by MYJ scheme showed less error, and more close to the observations. The differences of PBL thermal stratification and turbulent transportation simulated by different PBL schemes led to the differences of surface PM2.5 concentration simulation. The thicker inversion layer of MYJ scheme caused the lower surface PM2.5 concentration at night, while the lower mixing layer and weaker surface wind speed simulated by MYJ scheme resulted in a higher surface PM2.5 concentration in the afternoon. © 2016, Editorial Board of China Environmental Science. All right reserved.

Wang Y.,Chinese Academy of Meteorological Sciences | Xu X.,Chinese Academy of Meteorological Sciences | Lupo A.R.,University of Missouri | Li P.,Shanxi Meteorological Observatory | Yin Z.,Beijing Meteorological Bureau
Journal of Geophysical Research: Atmospheres | Year: 2011

By using numerical experiments and observational data, this study examined the uplifting and thermal effects of the Tibetan Plateau (TP) on downstream airflow in early summer. Our principal finding is that the uplifting effect of the TP in an Atmospheric General Climate Model (AGCM), including air made warmer than its surroundings climatologically by the huge topography, results mainly in a local response in the atmosphere, i.e., a large ridge north of the TP in the troposphere in June. There was no Rossby wave response to the uplifting effect. However, simulations and statistical analyses strongly suggested that the anomalous TP atmospheric heating associated with global climate warming tends to excite a Rossby wave originating from the TP via Lake Baikal and continuing to move through the Okhotsk Sea to downstream areas. The appearance of the Rossby wave coincides with the positive phase of the eastern part of a normal stationary wave originating in the Caspian Sea traveling via the Okhotsk Sea to the sea area east of Japan that often occurs in June. Thus the TP atmospheric heating acts as an additional wave source in relaying and enhancing the eastern part of the normal wave propagation. Its path usually lies beyond 40°N latitude, which is where the westerly jet stream takes over the role of waveguide. Copyright © 2011 by the American Geophysical Union.

Luo D.,CAS Institute of Atmospheric Physics | Xiao Y.,CAS Institute of Atmospheric Physics | Xiao Y.,Ocean University of China | Xiao Y.,Shanxi Meteorological Observatory | And 5 more authors.
Journal of Climate | Year: 2016

In Part I of this study, the impact of Ural blocking (UB) on the warm Arctic-cold Eurasian (WACE) pattern associated with the winter (DJF) arctic sea ice loss during 1979-2013 is examined by dividing the arctic sea ice reduction region into two dominant subregions: The Barents and Kara Seas (BKS) and the North American high-latitude (NAH) region (Baffin and Hudson Bay, Davis Strait, and Labrador Sea). It is found that atmospheric response to arctic sea ice loss resembles a negative Arctic response oscillation with a dominant positive height anomaly over the Eurasian subarctic region. Regression analyses of the two subregions further show that the sea ice loss over the BKS corresponds to the UB pattern together with a positive North Atlantic Oscillation (NAO+) and is followed by a WACE anomaly, while the sea ice reduction in the NAH region corresponds to a negative NAO (NAO-) pattern with a cold anomaly over northern Eurasia. Further analyses reveal that the UB pattern is more persistent during the period 2000-13 (P2) than 1979-99 (P1) because of the reduced middle-to-high-latitude mean westerly winds over Eurasia associated with the intense BKS warming. During P2 the establishment of the UB becomes a slow process because of the role of the BKS warming, while its decay is slightly rapid. In the presence of the long-lived UB that often occurs with the NAO+, the BKS-warming-induced DJF-mean anticyclonic anomaly is intensified and widened and then expands southward during P2 to amplify the WACE pattern and induce the southward displacement of its cold anomaly and the further loss of the BKS sea ice. Thus, midlatitude Eurasian cold events should be more frequent as the sea ice loss continues over the BKS. © 2016 American Meteorological Society.

Luo D.,CAS Institute of Atmospheric Physics | Xiao Y.,CAS Institute of Atmospheric Physics | Xiao Y.,Ocean University of China | Xiao Y.,Shanxi Meteorological Observatory | And 5 more authors.
Journal of Climate | Year: 2016

In Part I of this study, the Ural blocking (UB)-induced amplification role of winter warm Arctic-cold Eurasian (WACE) anomalies has been examined. It was found that the long-lived UB together with the positive North Atlantic Oscillation (NAO+) significantly contributes to the amplification of the WACE pattern. The present study examines how the UB variability affects quasi-biweekly WACE (QB-WACE) anomalies and depends on the NAO+ and North Atlantic conditions by classifying the UB based on a case study of a cold event that occurred over southern China in January 2008. A composite analysis during 1979-2013 shows that the QB-WACE anomalies associated with the UB that often occur with the NAO+ are strong and influenced by the North Atlantic jet (NAJ) and zonal wind strengths over Eurasia. For NAO+-related UB, the QB-WACE anomaly depends strongly on the location of UB, and the UB anomalies lag the NAO+ by approximately 4-7 days. The strength of the NAJ determines whether the combined NAO+ and UB anomalies exhibit a negative East Atlantic/West Russia (EA/WR-) pattern, while the region of weak zonal winds over Eurasia and the zonal extent of the NAJ dominate the location of UB. For southward-, eastward-, and westward-displaced UBs associated with a strong NAJ, the NAO+ favors the UB with a southward-displaced QB-WACE anomaly through wave train propagation like an EA/WR- pattern. Eastward- and southward-displaced UB anomalies induce similarly displaced cold anomalies with intrusion into southern China. However, for a northward-displaced UB, this happens without pronounced EA/WR- patterns because of a weak NAJ and is accompanied by a northward-displaced QB-WACE anomaly. © 2016 American Meteorological Society.

Guo J.,Chinese Academy of Meteorological Sciences | Niu T.,Chinese Academy of Meteorological Sciences | Rahimy P.,University of Twente | Wang F.,University of Electronic Science and Technology of China | And 2 more authors.
Acta Meteorologica Sinica | Year: 2013

Soil erosion is one of the most serious land degradation problems all over the world, causing irreversible land quality reduction. In this paper, we modify the Revised Universal Soil Loss Equation (RUSLE) model by replacing the factors of slope length and gradient with Sediment Transport Index (STI). The Digital Elevation Model, terrain parameters, Normalized Difference Vegetation Index (NDVI), and rainfall data are used as inputs to the model. Along with the application of remote sensing techniques and ground survey measurements, erosion susceptibility maps are produced. The revised models are then used to obtain the optimal estimate of soil erosion susceptibility at Alianello of southern Italy, which is prone to soil erosion. The soil loss estimated from the modified RUSLE model shows a large spatial variance, ranging from 10 to as much as 7000 ton ha -1 yr -1. The high erosion susceptible area constitutes about 46.8% of the total erosion area, and when classified by land cover type, 33% is "mixed bare with shrubs and grass", followed by 5.29% of "mixture of shrubs and trees", with "shrubs" having the lowest percentage of 0.06%. In terms of slope types, very steep slope accounts for a total of 40.90% and belongs to high susceptibility, whereas flat slope accounts for only 0.12%, indicating that flat topography has little effect on the erosion hazard. As far as the geomorphologic types are concerned, the type of "moderate steep-steep slopes with moderate to severe erosion" is most favorable to high soil erosion, which comprises about 9.34%. Finally, we validate the soil erosion map from the adapted RUSLE model against the visual interpretation map, and find a similarity degree of 71.9%, reflecting the efficiency of the adapted RUSLE model in mapping the soil erosion in this study area. © The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2013.

Hu L.,National Satellite Meteorological Center | Zhao H.,Shanxi Meteorological Observatory | Ma Y.,Shanxi Meteorological Observatory
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2014

For the next generation of Chinese geostationary meteorological satellites (FY-4) an optical lightning mapping sensor is planned to observe lightning on a real-time, continual basis. The measurement will detect the radiance discharged by lightning and transferred up to the cloud top at a near-infrared band. One important and urgent attention of the pre-study is how the instrument observation geometry quantitatively impact the received signals. A Monte Carlo approach is applied for simulating the transfer of lightning and the lightning radiation signatures which will be obtained by FY-4 lightning mapping sensor. The study focuses on the quantitative relationships between the observed lightning radiance and several key observation geometry parameters, such as satellite observation angle, pixel size and the horizontal location of lightning in the pixel. This will provide extremely valuable informations for the future application of lightning data observed by FY-4 satellite.

Huang S.,Ocean University of China | Huang S.,Shanxi Meteorological Observatory | Huang F.,Ocean University of China
Journal of Ocean University of China | Year: 2012

By using Season-reliant Empirical Orthogonal Function (S-EOF) analysis, three dominant modes of the spatial-temporal evolution of the drought/flood patterns in the rainy season over the east of China are revealed for the period of 1960-2004. The first two leading modes occur during the turnabout phase of El Niño-Southern Oscillation (ENSO) decaying year, but the drought/flood patterns in the rainy season over the east of China are different due to the role of the Indian Ocean (IO). The first leading mode appears closely correlated with the ENSO events. In the decaying year of El Niño, the associated western North Pacific (WNP) anticyclone located over the Philippine Sea persists from the previous winter to the next early summer, transports warm and moist air toward the southern Yangtze River in China, and leads to wet conditions over this entire region. Therefore, the precipitation anomaly in summer exhibits a 'Southern Flood and Northern Drought' pattern over East China. On the other hand, the basin-wide Indian Ocean sea surface temperature anomaly (SSTA) plays a crucial role in prolonging the impact of ENSO on the second mode during the ENSO decaying summer. The Indian Ocean basin mode (IOBM) warming persists through summer and unleashes its influence, which forces a Matsuno-Gill pattern in the upper troposphere. Over the subtropical western North Pacific, an anomalous anticyclone forms in the lower troposphere. The southerlies on the northwest flank of this anticyclone increase the moisture transport onto central China, leading to abundant rainfall over the middle and lower reaches of the Yangtze River and Huaihe River valleys. The anomalous anticyclone causes dry conditions over South China and the South China Sea (SCS). The precipitation anomaly in summer exhibits a 'Northern Flood and Southern Drought' pattern over East China. Therefore, besides the ENSO event the IOBM is an important factor to influence the drought/flood patterns in the rainy season over the east of China. The third mode is positively correlated with the tropical SSTA in the Indian Ocean from the spring of preceding year(-1) to the winter of following year(+1), but not related to the ENSO events. The positive SSTA in the South China Sea and the Philippine Sea persists from spring to autumn, leading to weak north-south and land-sea thermal contrasts, which may weaken the intensity of the East Asia summer monsoon. The weakened rainfall over the northern Indian monsoon region may link to the third spatial mode through the 'Silk Road' teleconnection or a part of circumglobal teleconnection (CGT). The physical mechanisms that reveal these linkages remain elusive and invite further investigation. © 2012 Science Press, Ocean University of China and Springer-Verlag Berlin Heidelberg.

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