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Gao S.,Nanjing University of Information Science and Technology | Chen B.,Nanjing University of Information Science and Technology | Li T.,Nanjing University of Information Science and Technology | Li T.,University of Hawaii at Manoa | And 2 more authors.
Dynamics of Atmospheres and Oceans | Year: 2017

Atmospheric Infrared Sounder (AIRS) temperature profiles during the period 2003–2013 are used to examine the warm core structures and evolution characteristics associated with the formation and development of western North Pacific (WNP) tropical cyclones (TCs). The warm core with a steady 1.5-K warming in the layer of 500–300 hPa occurs 24 h prior to tropical storm formation. Apparent eye warming extends upward to upper troposphere and downward to near surface after tropical storm formation. TC intensity shows a robust positive correlation with the warm core strength and has a weaker but still significant positive correlation with the warm core height (the weaker correlation is primarily attributed to the scattered warm core heights of weak TCs). Future 24-h intensity change of TCs has little correlation with the warm core height while it has a significant negative correlation with the warm core strength. Weak to moderate warm core at 500–200 hPa may be a necessary but not sufficient initial condition for TC rapid intensification. AIRS-observed warm core structures, in combination with other environmental factors, have the potential to improve the prediction of tropical storm formation and rapid intensification of WNP TCs. © 2017 Elsevier B.V.

Xu S.,Sun Yat Sen University | Xu S.,Guangzhou Central Meteorological Observatory | Lin W.,Sun Yat Sen University | Sui C.-H.,National Taiwan University
Atmospheric Research | Year: 2013

Following a numerical simulation study, we analyze the effect of the parameter of the cloud condensation nuclei concentration (CNP) on Typhoon Chanchu in convective, stratiform, and mixed precipitation areas based on the following three experiments: (1) a control (CTL) experiment using a mesoscale model and the Reisner-2 cloud scheme with the CNP value specified as 100cm-3; (2) a very clean marine (VCM) CNP experiment (CNP=25cm-3); (3) and a severe contamination (SC) CNP experiment (CNP=1000cm-3). We compare and analyze the simulated cloud structure and microphysical processes of the three experiments within the convective, stratiform, and mixed areas. The three precipitating areas are classified based on the ratio of cloud ice content to cloud water content at all precipitating grids proposed by Sui et al. (2007). The results show that the intensities of most microphysical processes are the largest in the convective area and the smallest in the stratiform area. Ice is dominant in the stratiform region and the water hydrometeor is dominant in the convective region. Furthermore, cloud water develops more quickly than cloud ice do in the mixed area. The response of the convective area to a varying CNP is greater than that of the stratiform area, and the mixed area is only slightly sensitive to the CNP. The dominance of cloud microphysical processes related to the growth of water hydrometeors weakens as the CNP increases. © 2012 Elsevier B.V.

Li W.,Sun Yat Sen University | Chen S.,Sun Yat Sen University | Chen G.,Tohoku University | Sha W.,Tohoku University | And 4 more authors.
Environmental Research Letters | Year: 2011

We assess the issues of urban effects on the precipitation over the Pearl River Delta (PRD) metropolitan regions of China. The spatial and temporal variations of strong versus weak precipitation over the PRD and surrounding nonurban areas are investigated. The results show that the urbanization signatures in strong precipitation are significantly different from those in weak precipitation over the urban areas. The PRD experiences more strong precipitation but less weak precipitation compared to surrounding nonurban regions. In addition, the strong precipitation over the PRD displays a pronounced seasonal variation. The seasonality of weak precipitation, however, is much weaker over the PRD compared to the surrounding nonurban regions. Moreover, a strengthening in the precipitation intensity, a reduction in the rainfall frequency and an increase in the convective precipitation as well as the afternoon precipitation are found over the urban areas, which are probably associated with the abundance in strong precipitation and the deficit in weak precipitation over the PRD. © 2011 IOP Publishing Ltd.

Wen Z.,Sun Yat Sen University | Wu N.,Sun Yat Sen University | Wu N.,Guangzhou Institute of Tropical and Marine Meteorology | Wu N.,Guangzhou Central Meteorological Observatory | Chen G.,Sun Yat Sen University
Chinese Journal of Atmospheric Sciences | Year: 2016

The onset of the South China Sea summer monsoon is strongly associated with the variations of meridional circulation over East Asia, particularly during 1-15 May. Using a linear diagnostic model, numerical experiments are performed that successfully capture the local meridional circulation and its anomaly relating to early and delayed onsets of the summer monsoon. It is shown that, in years with an early monsoon onset, anomalous ascending (descending) motion tends to occur over the South China Sea (central China), in clear contrast to the pattern in years with a delayed monsoon onset. Such a difference of meridional circulation is found to result from the meridional gradient of latent heat release, thermal and momentum advection, and the forcing effect of the southern boundary. An analysis of the related synoptic patterns suggests that the southward-shifted subtropical upper-level jets, westerly disturbances, frontal activities, and the retreat of the subtropical high from the South China Sea can trigger a direct circulation between low and middle latitudes through an effective transport of heat and momentum. The anomalous northerly wind from middle latitudes and the westerly wind from tropical regions work together to strengthen the low-level moisture convergence and convection over the South China Sea, driving strong upward motion. The results highlight that a strong interaction between midlatitude and tropical weather systems may play an important role in regulating the timing of the onset of the summer monsoon. Copyright © Chinese Journal of Atmospheric Sciences.

Fan Q.,Sun Yat Sen University | Yu W.,Sun Yat Sen University | Fan S.,Sun Yat Sen University | Wang X.,Sun Yat Sen University | And 4 more authors.
Journal of the Air and Waste Management Association | Year: 2014

This study focuses on the influences of a warm high-pressure meteorological system on aerosol pollutants, employing the simulations by the Models-3/CMAQ system and the observations collected during October 10-12, 2004, over the Pearl River Delta (PRD) region. The results show that the spatial distributions of air pollutants are generally circular near Guangzhou and Foshan, which are cities with high emissions rates. The primary pollutant is particulate matter (PM) over the PRD. MM5 shows reasonable performance for major meteorological variables (i.e., temperature, relative humidity, wind direction) with normalized mean biases (NMB) of 4.5-38.8% and for their time series. CMAQ can capture one peak of all air pollutant concentrations on October 11, but misses other peaks. The CMAQ model systematically underpredicts the mass concentrations of all air pollutants. Compared with chemical observations, SO2 and O3 are predicted well with a correlation coefficient of 0.70 and 0.65. PM2.5 and NO are significantly underpredicted with an NMB of 43% and 90%, respectively. The process analysis results show that the emission, dry deposition, horizontal transport, and vertical transport are four main processes affecting air pollutants. The contributions of each physical process are different for the various pollutants. The most important process for PM10 is dry deposition, and for NOx it is transport. The contributions of horizontal and vertical transport processes vary during the period, but these two processes mostly contribute to the removal of air pollutants at Guangzhou city, whose emissions are high. For this high-pressure case, the contributions of the various processes show high correlations in cities with the similar geographical attributes. According to the statistical results, cities in the PRD region are divided into four groups with different features. The contributions from local and nonlocal emission sources are discussed in different groups. The characteristics of aerosol pollution episodes are intensively studied in this work using the high-resolution modeling system MM5/SMOKE/CMAQ, with special efforts on examining the contributions of different physical and chemical processes to air concentrations for each city over the PRD region by a process analysis method, so as to provide a scientific basis for understanding the formation mechanism of regional aerosol pollution under the high-pressure system over PRD. © 2014 Copyright © 2014 A&WMA.

Wang L.,Fudan University | Du H.,Fudan University | Chen J.,Fudan University | Zhang M.,Fudan University | And 4 more authors.
Atmospheric Research | Year: 2013

The physical and chemical properties of aerosol particles were investigated during two dust storm events that occurred in March 20-21, 2010 (DS1) and April 26-27, 2010 (DS2), respectively, at Shanghai, China. Highest hourly mass concentrations of particulate matters with less than 2.5μm (PM2.5) and 10μm (PM10) in aerodynamic diameter reached 469 and 1700μgm-3, respectively, in DS1, whereas the corresponding highest values for PM2.5 and PM10 were 94 and 236μgm-3, respectively, in DS2. Profiles of hourly concentrations of water soluble ions show that anthropogenic air masses preceded dust plume by an interval of 10h during the two dust storm events. Anthropogenic air masses were characterized with high concentrations of SO4 2-, NO3 -, and NH4 +, whereas dust plume was dominated by Ca2+ in water soluble components. Together with back trajectories of air parcels arriving at Shanghai, analysis of surface weather chart shows that DS1 was characterized with the arrival of a cold front at Shanghai. In contrast, a chief feature of the cold front stimulated DS2 was that the cold-front did not extend to Shanghai, and dust particles traveled following the front and were transported to Shanghai by strong southeastward airstream although the front did not extend to Shanghai. Our results suggest that Asian dust particles are not homogeneously mixed with anthropogenic pollutants and consecutive transport of anthropogenic air masses and dust plumes occurs. •Asian dust particles were not homogeneously mixed with anthropogenic pollutants.•Consecutive transport of anthropogenic and dust plumes occurred by an interval of 10hours.•Dust particles can be transported to Shanghai by strong airstreams between a high and a low. © 2013 Elsevier B.V.

Gu D.,Guangzhou Institute of Tropical and Marine Meteorology | Li T.,University of Hawaii at Manoa | Ji Z.,Guangzhou Central Meteorological Observatory | Zheng B.,Guangzhou Institute of Tropical and Marine Meteorology
Journal of Climate | Year: 2010

The phase relationships of the western North Pacific (WNP) summer monsoon (WNPM) with the Australian monsoon (AM) and Indian monsoon (IM) are investigated using observational rainfall, SST, and NCEP reanalysis data for the period of 1979-2005. It is found that a strongWNPMoften follows a strongAM but leads a weak AM, and a significant simultaneous negative correlation appears between WNPM and IM. The in-phase relationship from AM to the succeeding WNPM occurs often during the El Niño decaying phase when the warm eastern Pacific SST anomaly (SSTA) weakens AM through anomalous Walker circulation and the persistence of an anomalous WNP anticyclone from the boreal winter to summer leads to a weak WNPM. The out-of-phase relation from WNPM to the succeeding AM occurs either during the El Niño early onset year when the warm SSTA in June-August (JJA) is strong enough to force a low-level cyclonic flow anomaly in WNP and in December-February (DJF) the same warm SSTA forces a weak AM, or during the El Niño decaying phase when the persistence of theWNP anomalous anticyclone causes a weak WNPMand the transition of a warmto a cold episode causes a strongAMin DJF. The simultaneous negative correlation betweenWNPMand IM often appears either during the El Niño early onset years when the warm eastern Pacific SSTA induces the cyclonic wind shear that strengthens WNPM but suppresses convection over India, or during the El Niño decaying summer when a weakWNPM results from the persistence of the local anomalous anticyclone and a strong IM results from the El Niño-to-La Niña transition or a basin-wide Indian Ocean warming. © 2010 American Meteorological Society.

Lin A.-L.,Guangzhou Institute of Tropical and Marine Meteorology | Gu D.-J.,Guangzhou Institute of Tropical and Marine Meteorology | Zheng B.,Guangzhou Institute of Tropical and Marine Meteorology | Li C.-H.,Guangzhou Institute of Tropical and Marine Meteorology | Ji Z.-P.,Guangzhou Central Meteorological Observatory
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2013

The interannual and interdecadal variability of South China Sea summer monsoon onset date is analyzed, and the relationship between the date and the Southern Ocean sea surface temperature is studied using the 31a (1979-2009) daily mean NCEP-DOE Reanalysis 2 and monthly extended reconstructed sea surface temperatures (ERSST.v2). It is shown that there is significant interannual and interdecadal variability in the monsoon onset date. The mean onset date shows a significant shift from 1979-1993 to 1994-2009. The onset date is positively correlated to Indian Ocean-Southern Ocean (0-80°E, 75°S-50°S) SST in preceding winter (Dec.-Jan.) and Pacific-Southern Ocean (170°E-80°W, 75°S-50°S) SST in preceding spring (Feb.-Mar.). The monsoon onset is earlier (later) when SST over Southern Ocean in preceding winter and spring is anomalously low (high). Thus the SST signal over Southern Ocean may be regarded as a predictor for the South China Sea summer monsoon onset. The SST anomaly over Southern Ocean may impact the South China Sea summer monsoon onset through air-sea interaction and atmospheric teleconnection. A strong (weak) ant-arctic oscillation (AAO) during a negative (positive) SST anomaly over Southern Ocean in boreal winter may remotely cause a negative (positive) geopotential height anomaly and a positive (negative) zonal wind anomaly in tropical Indian Ocean-western Pacific. The tropical circulation anomaly is maintained from the winter to April and May, and as a result the cross-equatorial low-level Somali jet from southern hemisphere to northern hemisphere is enhanced (weakened). These provide a favorable circulation condition for the early (late) onset of the South China Sea summer monsoon. The inter-hemispheric oscillation (IHO) resulted from the air mass redistribution contributes to the teleconnection between air-sea interaction over Southern Ocean and tropical monsoon circulation.

Chen L.S.,Chinese Academy of Meteorological Sciences | Li Y.,Chinese Academy of Meteorological Sciences | Cheng Z.Q.,Guangzhou Central Meteorological Observatory
Advances in Atmospheric Sciences | Year: 2010

The ability to forecast heavy rainfall associated with landfalling tropical cyclones (LTCs) can be improved with a better understanding of the mechanism of rainfall rates and distributions of LTCs. Research in the area of LTCs has shown that associated heavy rainfall is related closely to mechanisms such as moisture transport, extratropical transition (ET), interaction with monsoon surge, land surface processes or topographic effects, mesoscale convective system activities within the LTC, and boundary layer energy transfer etc.. LTCs interacting with environmental weather systems, especially the westerly trough and mei-yu front, could change the rainfall rate and distribution associated with these mid-latitude weather systems. Recently improved technologies have contributed to advancements within the areas of quantitative precipitation estimation (QPE) and quantitative precipitation forecasting (QPF). More specifically, progress has been due primarily to remote sensing observations and mesoscale numerical models which incorporate advanced assimilation techniques. Such progress may provide the tools necessary to improve rainfall forecasting techniques associated with LTCs in the future. © 2010 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg.

Lu S.,Guangzhou Central Meteorological Observatory | Wu N.-G.,Guangzhou Central Meteorological Observatory
Journal of Tropical Meteorology | Year: 2011

The conventional observations data, NCAR/NCEP-2 reanalysis data, and NOAA outgoing longwave radiation data are used to investigate different characteristics of Leo and Neoguri, two April typhoons that ever made landfall on the continent of China over the past 60 years. The results showed that both Leo and Neoguri occurred during the La Nina events. Strong convective activity, weak vertical wind shear and upper-level divergence were in favor of the formation of these April typhoons. Leo originated from a monsoon depression and Neoguri evolved from an easterly wave. The meandering moving track of Leo attributed to strong northeast monsoon and a weak and changeable subtropical high; the steady moving track of Neoguri was governed by a strong and stable subtropical high. Leo and Neoguri had similar terrain conditions and intensities during landfall but were different in precipitation as water vapor transport and duration of kinetic uplifting resulted in apparent discrepancies between them.

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