ON THE STUDY OF THE RELATIONSHIPS BETWEEN GUANGZHOU ATMOSPHERIC ENVIRONMENT FACTORS AND THE SARS EPIDEMIC

Based on SARS epidemic data and the corresponding atmospheric data, we used the timescale-partitioning technique, spectrum analysis and correlation analysis to investigate the impacts of the atmospheric environmental factors on the SARS epidemic. Results showed that there were close relations between environmental factors and SARS: The daily probable cases of SARS varied in 3-5 day cycles, much the same as the atmospheric elements did. The variations of the epidemics correlated remarkably with atmospheric elements. So conclusions can be drawn that weather changes have influences on the variations of daily SARS cases. In addition, statistical results showed that cold air activities aggravated the SARS epidemic.

ANALYSIS OF MID-SUMMER HIGH TEMPERATURE FREQUENCY ANOMALY IN GUANGZHOU

Using EOF, correlation analysis, the climatic characteristics are analyzed of the yearly high temperature frequency (HTF) in Guangzhou from 1951-2004, and the relationship between the mid-summer (July and August) HTF anomaly and the synchronous 500hPa heights of the region(65 - 150°E, 10 - 70°N) is also discussed. The results show that: (1) the average of HTF is 8.7 days per year in the recent 54 years in Guangzhou; high temperature occurs from May to September, and July and August have the highest frequency of occurrence; (2) there are distinct interannual and interdecadal changes in Guangzhou HTF, with an obvious increase since the 1980s; (3) the anomalous increase of mid-summer HTF in Guangzhou since the 1980s has a close relationship with the weakened westerlies in Northwest China, Mongolia, Lake Baikal and their vicinity and the intensified subtropical high in the mid-low latitude areas.

An Overview of Research and Forecasting on Rainfall Associated with Landfalling Tropical Cyclones

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.

Turbulent Variance Characteristics of Temperature and Humidity over a Non-uniform Land Surface for an Agricultural Ecosystem in China

This paper describes the application of the variance method for flux estimation over a mixed agricultural region in China. Eddy covariance and flux variance measurements were conducted in a near-surface layer over a non-uniform land surface in the central plain of China from 7 June to 20 July 2002. During this period, the mean canopy height was about 0.50 m. The study site consisted of grass （10% of area）, beans （15%）, corn （15%） and rice （60%）. Under unstable conditions, the standard deviations of temperature and water vapor density （normalized by appropriate scaling parameters）, observed by a single instrument, followed the Monin-Obukhov similarity theory. The similarity constants for heat （CT） and water vapor （Cq） were 1.09 and 1.49, respectively. In comparison with direct measurements using eddy covariance techniques, the flux variance method, on average, underestimated sensible heat flux by 21% and latent heat flux by 24%, which may be attributed to the fact that the observed slight deviations （20% or 30% at most） of the similarity ＂constants＂ may be within the expected range of variation of a single instrument from the generally-valid relations.

CONNECTION OF THE SOUTH CHINA SEA SUMMER MONSOON TO MARITIME CONTINENT CONVECTION AND ENSO

The relationship between the intensity of the South China Sea summer monsoon （SCSSM） and the Nino3.4 index and anomalous atmospheric circulation patterns associated with a strong and weak SCSSM are investigated using the NCEP/NCAR reanalysis data, Extended Reconstructed Sea Surface Temperature （ERSST） data and Climate Prediction Center Merged Analysis of Precipitation （CMAP） data. The SCSSM is significantly positively correlated with the Nino3.4 index in the succeeding northern autumn and winter. In the strong minus weak SCSSM composite, a positive East Asia-Pacific teleconnection （EAP） pattern and a negative Europe-Asian-Pacific teleconnection （EUP） pattern appear in the 500 hPa height difference field; low-level cross-equatorial flows are strengthened over the Maritime Continent （MC） region; positive （negative） precipitation anomalies occur in the South China Sea and western north Pacific （MC）. A possible mechanism through which SCSSM affects ENSO is proposed. A strong （weak） SCSSM strengthens （weakens） cross-equatorial flows over the MC. The anomalous cross-equatorial flows cool （warm） the SST around the MC through enhanced （reduced） surface latent heat fluxes. The cooling （warming） further leads to suppressed （enhanced） convection over the MC, and causes the anomalous westerly （easterly） in the equatorial western Pacific, which favors the onset of E1 Nino （La Nina） through modulating the positive air-sea feedback process.

SINGULAR SPECTRUM ANALYSIS FOR TROPICAL CYCLONE LANDING IN GUANGDONG

Using the method of Singular Spectrum Analysis (SSA), the evolution regularity of tropical cyclo- nes landing in Guangdong are analyzed. The main periods of yearly topical cyclones landing in Guangdong are found at 8 and quasi-3 years, and in the west of Pearl River Mouth are 12 and quasi-2 years to the west of Pearl River Mouth. The northwest Pacific that topical cyclones are generated is divided into 8 areas, and the SeaSur- face Temperature (SST) in each area is analyzed using SSA. The main periods of NINO-west are 8 and 3 years, and those of the warm pool are 12 and 2 years, respectively. This may be the physical reason for the generation tropical cyclones landing in Guangdong. By combining the Maximum Entropy Method (MEM) with SSA (SSA- MEM), the yearly variation trend of tropical cyclones landing in Guangdong and the Pearl River Mouth are force- ast, and the results are good. The method can be used in operational short-range climate forecast.

VARIATION OF PRECIPITATION DURING WINTER AS A CAUSE OF SUSTAINED DROUGHT IN GUANGDONG DURING THE PAST 50 YEARS

The variation characteristics of precipitation during the winter （between October and the following March, to be referred to as just ＂the winter＂ hereafter） in Guangdong province during the past 50 years （from 1957 to 2006） and the relationship with Pacific SST are studied using the methods of Empirical Orthogonal Function （EOF） analysis, wavelet analysis, and correlation analysis. The results show that The Guangdong precipitation during the winter exhibits quasi-periodic significant oscillations of 40 years and 2 years; rainfall is less from the end of the 1950s to the start of the 1970s and from the end of the 1990s to the present than from the mid 1970s to the mid 1990s. The frequency of sustained drought is more than sustained flooding during the winter. The Guangdong precipitation during this time period is in significantly positive correlation to the equatorial central and eastern Pacific SST, but in a significantly negative correlation with the western and northern Pacific SST east of the Philippine Sea. 61.5% of the sustained drought occurred in the phase of negative anomalies of the Nifio3.4 index and 38.5% in the phase of positive ones. A composite analysis of atmospheric circulation is performed for the positive and negative phases of the Nifio3.4 region associated with the sustained drought. The results showed that a weak polar vortex, a strong trough in Europe and a ridge near Balkhash Lake, active cold air and consistent northerly wind anomalies controlling Guangdong at low levels, an inactive westerly low disturbance in the low-mid latitude of the Asian continent, and a weak southern branch westerly trough, are all mutual causes for the sustained drought.

CONTRAST ANALYSIS OF APRIL TYPHOONS LEO AND NEOGURI

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.

THE RELATIONSHIP BETWEEN SOUTH CHINA SEA SOUTHWEST MONSOON ANOMALIES AND IMPORTANT WEATHER IN GUANGDONG PROVINCE DURING THE RAINING SEASONS

The activity of South China Sea southwest monsoon (SCSSM) has direct impacts on the anomalies of important weather in Guangdong province during the raining seasons. So it is necessary to explore thoroughly the activity pattern of SCSSM and its relationship with important weather anomalies in the province. In this paper, the methods of composite analysis and correlation statistics are used to study the relationship between the onset date and intensity of SCSSM and the important weather, such as precipitation trends in Guangdong province during the annually first and second raining seasons, the timing of the annually first and last typhoon and the number of typhoons landing in Guangdong province. The results show that the rainfall is less than normal during the first raining season, but more than normal during the second one and there are more tropical cyclones landing in Guangdong province in the years of early SCSSM onset. The rainfall is more than normal during the second raining season and there are more tropical cyclones landing in Guangdong province in the years of strong SCSSM. The relationship between the SST of April - June, July - September and previous winter (December - February) and 500 hPa geopotential height and the onset date and intensity of SCSSM is analyzed. Some mechanisms between the onset dates and intensity of SCSSM and the important weather anomalies in Guangdong province are preliminarily explored. The results can be used for reference in short-term climate forecast.

THE VARIABILITY CHARACTERISTICS AND PREDICTION OF GUANGDONG POWER LOAD DURING 2002 – 2004

The variability characteristics of Guangdong daily power load from 2002 to 2004 and its connection to meteorological variables are analyzed with wavelet analysis and correlation analysis. Prediction equations are established using optimization subset regression. The results show that a linear increasing trend is very significant and seasonal change is obvious. The power load exhibits significant quasi-weekly (5 – 7 days) oscillation, quasi-by-weekly (10 – 20 days) oscillation and intraseasonal (30 – 60 days) oscillation. These oscillations are caused by atmospheric low frequency oscillation and public holidays. The variation of Guangdong daily power load is obviously in decrease on Sundays, shaping like a funnel during Chinese New Year in particular. The minimum is found at the first and second day and the power load gradually increases to normal level after the third day during the long vacation of Labor Day and National Day. Guangdong power load is the most sensitive to temperature, which is the main affecting factor, as in other areas in China. The power load also has relationship with other meteorological elements to some extent during different seasons. The maximum of power load in summer, minimum during Chinese New Year and variation during Labor Day and National Day are well fitted and predicted using the equation established by optimization subset regression and accounting for the effect of workdays and holidays.

A STATISTICAL MODEL FOR PREDICTION OF INTENSITY AND FREQUENCY OF TROPICAL CYCLONES MAKING LANDFALL ON CHINA

Based on NCEP/NCAR reanalysis data and Yearbook of China landfalling tropical cyclones(hereafter CLTC) from 1949 to 2008,correlation between CLTC frequency/intensity and 500 hPa height field and sea surface temperature(SST) fields are investigated and employed for TC statistical prediction.A prediction model for yearly and monthly intensity and frequency of CLTC is established with binomial curve fitting by choosing the gridpoints with high correlation coefficients as composite factors.Good performance of the model in experiments shows that the model could be used in routine forecast.

COMPARISONS BETWEEN DOPPLER AND SIMULATED FEATURES OF A SUPERCELL

Firstly, typical features of a supercell, which occurred in Guangzhou on August 11, 2004, are discussed by using the new generation weather radar data. V-notch, finger-echo, weak echo region, overfiang and echo-wall are observed from reflectivity products. A vertical cross section of the radial velocity is made along the direction of the low-level inflow and across the maximum reflectivity core, which displays a part of strong updraft and downdraft. Secondly, a 3-D convective storm model is used to simulate the supercell. The maximum reflectivity and the core thickness of the simulated radar echo are 75 dBz and 14km, respectively. These values are more than the counterparts that are detected by radar. The reason is that attenuation is not calculated in the model. The wind field structure is also given when the storm is the strongest. Divergence, caused by thunderstorm outflow, is in the low level. In the middle and high level, convergence is dominant, but the plume is not simulated at the top. Finally, the evolution of the simulated vertical motion is documented. The interaction between the environmental wind and the updraft, which is formed by the convergence on the ground at the beginning, makes the storm stronger. Then, downdraft occurs and grows. When it becomes dominant, the supercell collapses.

SPATIAL AND TEMPORAL VARIATIONS OF EVAPORATION OVER SOUTH CHINA IN AUTUMN

The spatial and temporal variations of the instrument-based evaporation and actual evaporation in autumn during a 45-year period from 1960 to 2004 are studied using the observation data from 66 stations over South China. The results reveal that there are two main anomalous centers of the instrument-based evaporation in autumn in the central and northwestern parts of South China respectively. The instrument-based evaporation over the central part of South China in autumn experiences not only a decreasing trend but also a main interdecadal variation. The solar radiation is best correlated with the instrument-based evaporation among all affecting factors. For the actual evaporation, two main anomalous centers are located at the central and western parts of the South China respectively. The actual evaporation over the two regions illustrates an interannual variation. Among the affecting factors, precipitation is the most remarkable. The actual evaporation is usually 40 percent of the instrument-based one, and the overall rate has a slightly increasing trend from the southern part to the northern part of the South China in autumn.

Hazard Analysis of Severe Convective Weather in Guangdong Province, China

In the present study,a hazard model of severe convective weather was constructed on the basis of meteorological observational data obtained in Guangdong Province between 2003 and 2015.In the analysis,quality control was first conducted on the severe convective weather data,and the kriging method was then used to interpolate each hazard-formative factor.The weights of which were determined by applying the coefficient of variation method.The results were used to establish the hazard-formative factor model of severe convective weather.The cities showing the greatest hazards for severe convective weather in Guangdong Province include Yangjiang,Dongguan,Foshan,Huizhou,Jiangmen,and Qingyuan.

The coral grayness in northern South China Sea and its description of interdecadal variation of precipitation in south China

The interdecadal variation of coral grayness in northern South China Sea (SCS) is studied using the annual mean coral grayness in northern SCS from 1789 to 1992 and annual precipitation at Guangzhou from 1908 to 1992 by Singular Spectrum Analysis (SSA), correlation analysis, Mann-Kendall’s abrupt change analysis and composite analysis. The interdecadal variation of south China precipitation as reflected by the series of Guangzhou precipitation rebuilt with the coral grayness is discussed. The results show that the variation of coral grayness in SCS has significant terms of tendency, much-weighted interdecadal variation and weak interannual variation. There was a century-scale abrupt change of coral grayness at the end of the 1880s that changed from positive anomalies to negative anomalies. The global field of SST difference corresponding to the point of abrupt change was negative anomalies over the SCS and neighboring northern Indian Ocean, most of central and western Pacific Ocean and coastal areas of the northern Atlantic Ocean. The large-scale distribution of SST anomalies is concomitant with the century-scale abrupt change of coral grayness in SCS. Negative correlation exists between the coralgrayness in SCS and precipitation in Guangzhou on the interdecadal scale and the interdecadal precipitation in Guangzhou as reflected by the interdecadaldata of SCS coral grayness shows that the interdecadal variation of south China precipitation changes significantly from phase to phase. The current study aims at contributing in the effort of identifying alternative indexes for climate change in south China on the interdecadal scale and beyond.

THE INTERANNUAL OSCILLATION OF RAINFALL OVER CHINA AND ITS RELATION TO THE INTERANNUAL OSCILLATION OF THE AIR-SEA SYSTEM

The quasi-biennial oscillation (QBO) and 3.5 years quasi-periodic oscillation (named TO hereafter) are exhibited in most of 48 weather stations of China by applying power spectrum analysis to the monthly rainfall data for the period from Jan. 1933 to Dec. 1987. In order to reveal the features of QBO and TO components, another rainfall data set in 160 stations over China for the period from Jan. 1951 to Dec. 1987 was analysed by means of a new method named complex empirical orthogonal function (CEOF). The results show that both QBO and TO modes exhibit two propaga- tion ways: one originates in Northeast China, extends southward, passes through North China and reaches the eastern part of Northwest China and the northern part of Southwest China; the other appears over Guangdong and Fujian, then moves northward and westward respectively to the Huanghe-Huaihe Basin and Southwest China. These two paths of oscillation meet over North China and the area between the Changjiang River and the Huanghe River. A significant correlation exists between the interannual oscillation of the rainfall over China and that of the sea surface temperature (SST) at the equator. Although the correlation between the rainfall over China and the SST over the equatorial eastern Pacific is rather weak, the correlation between their oscillation component is pronounced.

Topographic Effect on the Energetics of Geostrophic Adjustment

In this work, the impact of topography on the geostrophic adjustment processis discussed with a simple two-layer shallow water model, in which the lower-layer fluid isinitially stationary while the upper-layer is perturbed by the impulsive injection of momentum.During the geostrophic adjustment process of this ideal model, the initial kinetic energy isreleased and a fraction of it is converted into potential energy of the final geostrophicallyadjusted state. Thus, after the geostrophic adjustment, the kinetic energy of the system is reducedwhile the potential energy is enhanced. As the topographic effect is considered, it is found thatthe decrease of the kinetic energy (ΔKE) and the increase of the potential energy (ΔPE) of thesystem are weakened as compared to the case that the lower boundary is flat. Furthermore, thetopographic effect on APE is less pronounced than that on ΔKE, which implicates that the topographytends to inhibit the energy dispersion of the inertio-gravity wave. The numerical simulation of thegeostrophic adjustment process shows that, due to the impact of topography, the convergence anddivergence in the low layer are reduced and the undulation of the interface between the lower-layerand upper-layer is weakened. This means that the amplitude of the inertio-gravity wave is decreased,and thus, the energy radiated by the inertio-gravity wave is lessened.

Automatic Identification of Storm Cells Using Doppler Radars

Three storm automatic identification algorithms for Doppler radar are discussed. The WSR-88D Build 7.0 （B7SI） tests the intensity and continuity of the objective echoes by multiple-prescribed thresholds to build 3D storms, and when storms are merging, splitting, or clustered closely, the detection errors become larger. The B9SI algorithm is part of the Build 9.0 Radar Products Generator of the WSR-88D system. It uses multiple thresholds of reflectivity, newly designs the techniques of cell nucleus extraction and closestorms processing, and therefore is capable of identifying embedded cells in multi-cellular storms. The strong area components at a long distance are saved as 2D storms. However, the B9SI cannot give information on the convection strength of storm, because texture and gradient of reflectivity are not calculated and radial velocity data are not used. To overcome this limitation, the CSI （Convective Storm Identification） algorithm is designed in this paper. By using the fuzzy logic technique, and under the condition that the levels of the seven reflectivity thresholds of B9SI are lowered, the CSI processes the radar base data and the output of B9SI to obtain the convection index of storm. Finally, the CSI is verified with the case of a supercell occurring in Guangzhou on 11 August 2004. The computational and analysis results show that the two rises of convection index matched well with a merging growth and strong convergent growth of the supercell, and the index was 0.744 when the supercell was the strongest, and then decreased. Correspondingly, the height of the maximum reflectivity, detected by the radar also reduced, and heavy rain also occurred in a large-scale area.

Analysis on Anomalous Precipitation in Southern China During Winter Monsoons

The winters of 1997/1998 and 1998/1999, corresponding to E1 Nifio and La Nina episodes, respectively, were two typical rain-abundant and -scarce seasons for the southern China. In order to understand the cause of the anomalous precipitation during the two winters, a comparative analysis technique has been employed to investigate the differences in general circulation and moisture transportation between the two seasons. The results show that the abundant rainfall during the winter of 1997/1998 was associated with the ENSO warm episode event, eastward shifted weak westerly trough/ridge, weakened East Asian winter monsoon （EAWM）, strengthened subtropical high, and presented two anti-cyclonic circulations over Hokkaido and the Philippine Sea, respectively, as well as one cyclonic circulation over the Yangtze River Basin in the anomalous wind fields of the lower troposphere. During the rain-scarce winter, however, the patterns of equatorial sea surface temperature anomalies and the circulation systems both in upper and lower levels were nearly the opposite of those during the rain-abundant winter. It has also been discovered that the water vapor over southern China during the winters came mainly from the southwesterly flow ahead of troughs in the southern branch of westerlies and the turning flow over the South China Sea-Indo-China Peninsula area; and the moisture transportation channels varied significantly with regard to height. The intensified flow in the southern branch of westerlies and the anti-cyclonic circulation anomaly over the Philippine Sea during the winter of 1997/1998 were favorable for moisture transportation to China's Mainland, however the two moisture transportation streams were dramatically weakened during the winter of 1998/1999 due to weak westerly flow and the dominance of a cold high system in the lower level over the southeast coast of China. Such a significant inter-annual change of moisture transportation is a key factor resulting in the obvious difference in precipitation between the two winters.