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31 August 2013, Volume 29 Issue 4 Previous Issue    Next Issue

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Diagnostic analysis of two heavy rainfall time periods in a torrential rain process and its numerical simulation in Hubei province GAO Qi,XU Ming,GOU A-ning 2013, 29 (4):  1-10.  Abstract ( 602 )   PDF (6068KB) ( 486 )   Save Based on the daily NCEP/NCAR reanalysis data, the conventional and intensive observational data, the brightness temperature (TBB) from FY2C, the large-scale circulation background and mesoscale convective system of two heavy rainfall time periods in a torrential rain process on August 28-30, 2008 in Hubei province were diagnosed, and other physical quantities fields influencing this process were also analyzed by WRF model. The results indicate that there are two significantly precipitation enhancement time periods in this process, and both durations from the beginning to the end are same. Precipitation intensity is stronger in the second period than in the first one. The first heavy rainfall time period is formed by low vortex shear and surface warm moist airflow, while the second one is caused by low vortex shear, the middle and low level short wave trough and cold surface air. The hourly rainfall and cloud mass characteristics during the two periods suggest that motions of the rain mass and cloud mass are same, and enhancements of precipitation intensity appear at the night and early morning. It also suggests that the β mesoscale convective cloud cluster has a close relationship with the torrential rain process. The movement of warm shear line from south to north affects the rainfall enhancement in the first period, while that of cold shear line of southwest vortex from west to east affects the rainfall enhancement in the second. According to the model results, the increasing amplitude of rainfall in the second time is more significant. There is strong energy for two heavy rainfall periods over the study area. There exists the strong water vapor convergence in the whole process. The rainfall center at the surface has a good correlation with a large value center of the moist potential vorticity at upper level. Related Articles | Metrics

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Diagnosis analysis of regional rainstorm in Meiyu rain period using Q vector and moist potential vorticity LIU Xue-hua,ZHU Xiao-feng,LIANG Liang 2013, 29 (4):  11-17.  Abstract ( 359 )   PDF (2897KB) ( 398 )   Save Based on the conventional surface observation data, the precipitation data from automatic weather stations and the NCEP reanalysis data, a rainstorm process on June 19-21, 2010 in the middle and lower reaches of the Yangtze River was diagnosed by Q vector and moist potential vorticity theory. The results indicate that the lower level shear moves slowly southeastwards which causes the rainstorm. The region that has big absolute values of the Q vector and Q vector frontogenesis function is corresponding to the strong rain band and their values change with rainfall, while the big value center of Q vector frontogenesis function and the rainfall center are sometimes not consistent. The change of Q vector divergence coincides with that of rain band center. The strong rainfall band is situated on the dense contour area with transition between positive and negative value of , and increasing gradient of  is corresponding to rainfall enhancement, and vice versa. Related Articles | Metrics

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Numerical simulation on a heavy rainstorm process in Beijing JIANG Li-hui,ZHANG Xiao-yu,ZHUANG Zi-bo 2013, 29 (4):  18-25.  Abstract ( 611 )   PDF (3121KB) ( 555 )   Save Based on the NCEP reanalysis data with the spatial resolution of 1°× 1° grid, a heavy rainstorm process on July 24, 2011 in Beijing was simulated by WRF3.3 (Weather Research and Forecasting Model for version 3.3) model, and this process was diagnosed in terms of high resolution data from the model. The results indicate that this process can be well simulated using the WRF model. The heavy precipitation is affected not only by an uplift power generated by the interaction of long-wave trough and the surface convergence in the middle and low level of troposphere, but also by the force of the divergence at  the upper level of troposphere. Under these configurations, the large-scale dynamic uplift in the middle and low levels and strong divergence at the upper level are in a state of vertical coupling, which is favorable to the development of the vertical circulation and convection over the heavy rainfall region. At the same time, the value of relative humidity is greater than 70% below the 500 hPa over Beijing which forms a deep and humid environment for the generation of heavy rain, and provides abundant water vapor for generating, strengthening, and maintaining precipitation. On the basis of atmospheric stability, the K index is high in the whole Beijing, and the peak value is 42.5 ℃. It means that atmospheric stratification is unstable. The analysis of dynamical variables show that the flow field features of upper divergence and lower convergence accelerate the generation of precipitation. The coupling of negative helicity in upper level and positive value in lower level is the dynamical mechanism to trigger and maintain precipitation. Related Articles | Metrics

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Diagnostic analysis of freezing rain weather event in February of 2010 in Liaoning region GUAN Chun-ling,WANG Tian-kui 2013, 29 (4):  26-30.  Abstract ( 441 )   PDF (1263KB) ( 308 )   Save Based on the conventionally observational data, a freezing rain snow disaster on the last ten days of February in 2010 in Liaoning region was diagnosed by weather and climatic conditions as well as atmospheric physical variable field, including forming reasons of generation and development, main features and key reason leading to serious disaster. The results show that a small trough splitting from low vorticity at 500 hPa moves eastwards, which is the circulation background of freezing rain weather. The unending water vapor transport and low level convergence at 700 hPa are the basic conditions of precipitation generation. The strong surface cold air is atrigger mechanism of freezing rain weather. Cold ice crystal layer in the upper level, warm melt layer in the middle and low levels that temperature is above 0 ℃, cold layer near the ground from the ground to 1-2 km upper level that temperature is below 0 ℃ and the ground temperature is also below 0 ℃, these complex inversion temperature layers are  the weather conditions of freezing rain generation. Upper warm advection is one of the key conditions for retaining warm layer structure in the middle level, which is important to warm layer. If this warm layer disappears, the freezing rain process would end. The intensity of freezing rain has a close relation with water vapor saturation in the middle and low levels, surface temperature, ascending and descending movement in the middle and low levels. Related Articles | Metrics

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Application of precipitable water vapor from ground based GPS data to analysis of precipitation weather process HUANG Zhen,LI Wan-biao,LIANG Jun 2013, 29 (4):  31-36.  Abstract ( 758 )   PDF (838KB) ( 20441 )   Save Based on the perceptible water vapor (PWV) data from the ground based GPS, the water vapor characteristics of precipitation weather processes in Dalian in 2010 were analyzed. The results show that the PWV data could reflect the temporal and spatial variation of water vapor and its variation characteristics has a significant corresponding relationship with precipitation. If the precipitation process differs, the PWV characteristics are also distinctly different. The PWV variation is gentle for a stable precipitation type and it has a single peak value; water vapor changes violently for a convective precipitation type and it is in a fluctuating trend; it is of the common characteristics of the above two precipitation types for a mixed precipitation type. The thresholds of the PWV related to rain are also given in the text, which indicates that the PWV data are useful to forecast precipitation to some extent. Related Articles | Metrics

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Simulation and projection of the surface temperature based on five global climate models over the northeast China CUI Yan,LI Qian,ZHOU Xiao-yu,ZHANG Xiao-yue,ZHAO Chun-yu 2013, 29 (4):  37-46.  Abstract ( 656 )   PDF (1261KB) ( 436 )   Save Based on the observed temperature data at 162 weather stations in the northeast China and five IPCC AR4 coupled climate models, the simulation abilities of global climatic model and multi model ensemble average for surface temperature were evaluated, and the variation of temperature in the future was projected under SRES B1, A1B and A2 three emission scenarios. The results show that the annual variation and spatial distribution of the surface temperature over the northeast China could be simulated accurately by the global climate models.  However, the simulated values are systematically lower than the observed values in the study area. The simulated value in summer is 1.16 ℃ lower than the observed value, while it is better than that in winter. The multi-model ensemble (MME) suggests that climate over the northeast China will has a warming trend in the middle and last period of 21st century under the three emission scenarios. The increasing amplitude of temperature is larger in the last period than in the middle period, so is in winter than in other seasons. Among the three scenarios, it is the largest under SRES A2 scenario and smallest under B1 scenario, respectively. The increasing amplitude of temperature increases from south to north, and the most obvious warming area is located in Xiaoxing'anling mountain of Heilongjiang province. The mean annual surface temperature in the northeast China would increase 2.39 ℃ under SRES B1 scenario, 3.62 ℃ under SRES A1B scenario and 4.43 ℃ under SRES A2 scenario in the last of 21st century, respectively. Related Articles | Metrics

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Visibility forecast of fog weather in Taiyuan GUAN Qin,LI Qing-ping,HUANG Ling-guang, LI Jie 2013, 29 (4):  47-53.  Abstract ( 919 )   PDF (1117KB) ( 483 )   Save Typical fog cases were simulated by the MM5 model in 2009 in Shanxi province. The results indicate that the simulated temperature at 2 m height is about 2 ℃ lower than the observed one; the simulated relative humidity is about 15% higher than the observed one; the simulated wind speed at 10 m height is about 0-2 m·s-1 greater than the observed one. The forecast indexes of fog include three conditions in Shanxi province, namely, the liquid water content at 20 m height is from 0.13 g·kg-1 to 0.60 g·kg-1; there exists a temperature inversion layer between 20 m and 1500 m heights; the surface wind speed at 10 m height is less than 4 m·s-1. A visibility forecast model is established by the daily mean visibility, relative humidity and air pollution index in Taiyuan. The forecast results of visibility by the MM5 and CAPPS are corrected using the observed data, and the revised forecast equation is developed. Two fog cases are forecasted using the revised equation, and it suggests that the model could be applied in Shanxi province. Related Articles | Metrics

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Temporal and spatial distribution of cold wave and its variation around the Bohai Sea region from 1961 to 2010 DUAN Li-yao,LIU Ai-xia,YU Li-li 2013, 29 (4):  54-58.  Abstract ( 548 )   PDF (935KB) ( 582 )   Save Based on the daily mean and minimum temperatures at 58 weather stations around the Bohai Sea region from 1961 to 2010, the frequency and intensity of cold wave were analyzed in terms of the national standard on cold wave, and the climatic characteristics of cold wave in a single station and in the whole study area were discussed. The results indicate that the regional differences of cold wave frequencies in a single station are significant. In general, the cold wave is in a decreasing trend from north to south around the Bohai Sea region, and the number of annual mean cold wave is 21 in Zhangbei station and it is the highest among all stations, while the number  is less than 2  in the stations of Beijing and Tianjin region. There are 233 regional cold waves in the recent 50 years and it appears mainly from September to April, especially in November, and it is in a significant decreasing trend. The frequencies of regional cold wave is the highest from 1960s to 1970s, while it decreases since 1980s and an abrupt change appears in 1983. The extreme strong regional cold wave is rare, and it is only twice in 1960s and once per ten years since 1970s. The regional cold wave decreases significantly under the global warming background around the Bohai Sea region, while the extreme strong cold wave events do not decrease. Related Articles | Metrics

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Lightning characteristics in a heavy rainfall process caused by southwest vortex GOU A-ning,ZHAO Yu-chun,HUANG Yan-gang,WANG Yu-juan 2013, 29 (4):  59-63.  Abstract ( 449 )   PDF (1325KB) ( 458 )   Save Based on the Doppler weather radar echo data and the observational data from the lightning location detection equipment and the meteorological data from regional automatic stations, the lightning characteristics in a heavy rainfall process caused by the southwest vortex on June 9, 2011 in Hubei province were analyzed. The results indicate that the location of ground lightning differs in the different stages of mecoscale convective systems (MCS). The frequencies of positive and negative lightning reach the peak values synchronously, which is one of the symbols of MCS mature. The intensive region of ground lightning and the rapid moving strong echo location of MCS are coincident. The positive ground lightning appears in strong echo region of MCS; they have a good relationship with radar echo between 45-55 dBz; the strong precipitation occurs in the disappearing stage of MCS. Related Articles | Metrics

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Analysis of quality control procedures for hourly air temperature data from automatic weather stations in China ZHANG Zhi-fu,REN Zhi-hua,ZHANG Qiang,ZOU Feng-ling,YANG Yan-ru 2013, 29 (4):  64-70.  Abstract ( 466 )   PDF (1971KB) ( 731 )   Save The hourly meteorological data from the automatic weather stations (AWS) is very vital to meteorological disaster warning, decision-making service and forecast and so on. Based on the hourly temperature data from the AWS, the daily maximum/minimum air temperature in four times (02:00, 08:00, 14:00, 20:00 Beijing time) from the national weather stations, the questionable and wrong hourly air temperature data were analyzed, and a quality control procedure of hourly air temperature data was developed for the temperature of AWS in China. The quality control procedure could be used for the regional and national AWS. It had been evaluated by the hourly air temperature data about 27000 weather stations from 2006 to 2010 in China. The results show that the accurate rates, questionable rates and wrong rates of hourly air temperature in the regional AWS are 99.431%, 2.24‰ and 3.45‰, and the corresponding rates in the national AWS are 99.82 %, 1.27 ‰ and 0.49 ‰, respectively. Both questionable rates are similar, while there is a magnitude difference for both wrong rates. According to the analysis of quality control of long time series air temperature data, it suggests that the design of the procedure is reasonable, and it could check the questionable data and wrong data. Thus, it could be used in the meteorological operation. Related Articles | Metrics

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Changes of temporal-spatial pattern and services evaluation of the ecosystem in the Liaohe river basin HOU Wei,WANG Yi,MA Xi-ping,WU Dan,XU Cheng-bin,HU Cheng,LI Qian 2013, 29 (4):  71-76.  Abstract ( 348 )   PDF (988KB) ( 473 )   Save The ecosystem was divided into 7 types in the Liaohe rive basin of Liaoning province. The temporal and spatial changes of the ecosystem structure were analyzed on three scales, i.e. the whole basin, 15 watersheds and riparian zone. Combining an ecosystem services evaluation method, the ecosystem services and its variation were evaluated on three scales. The results show that farmland and forest ecosystems are dominant in the whole basin. There is a significant difference for the ecosystems structure and its temporal and spatial variations among 15 watersheds. The structures of ecosystem between riparian zone and the whole basin differ significantly. Compared with the ecosystem structure in the whole basin, the proportion of forest ecosystem in the riparian zone reduces distinctly, while that of water and wetland ecosystem increases significantly. The ecosystem service value in the whole basin decreases gradually. Among all ecosystem types, the service value of forest ecosystem is the highest both in the whole basin and in the watersheds. However, the ecosystem service value of water and wetland is the highest in the riparian zone. Related Articles | Metrics

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The relationship between MJO and snow disaster in the south of China in January of 2008 ZHU Hong-rui,LIU He-nan,ZHANG Hong-ling,WANG Chun-hua 2013, 29 (4):  77-83.  Abstract ( 408 )   PDF (1921KB) ( 437 )   Save Based on the Madden–Julian oscillation index, the outgoing long wave radiation (OLR) data, the daily NCEP/NCAR reanalysis data and precipitation data in the south of China, the relationship between Madden–Julian oscillation (MJO) and the snow disaster in 2008 in the south of China and the forming reason of snow disaster were discussed by a synthetic analysis method. The results show that the MJO has an obviously eastward phenomenon in the snow disaster process, namely, it spreads from the Western Pacific to the India Ocean. Accompanying with the eastward MJO, the precipitation intensity and its concentrating region also change. The MJO could modulate the snow disaster process to some extent. The analysis of OLR also suggests that four abnormal rainfall (snow) processes in the early of 2008 in the south of China are influenced by the two eastward MJO. The first eastward MJO leads to the strength of the western Pacific subtropical high continually, while the second one makes the south brand trough active. The southward wind in the west side of subtropical high and the active of the south trough make the warm wet airflow transporting continually to China, which provides water vapor condition for strong precipitation in the south of China. Related Articles | Metrics

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A forecast method of road icing effect index classification in Zhenjiang, Jiangsu province SUN Cui-mei,MA Jun-feng,KONG Qi-liang,WU Li-jun,WANG Yan 2013, 29 (4):  84-88.  Abstract ( 426 )   PDF (500KB) ( 469 )   Save Based on the air temperature data on the two different underlying surface types that one is the cement pavement and the other is the asphalt pavement from March of 2010 to December of 2003 in Zhenjiang, the climatic characteristics of icy roads were analyzed. Combining precipitation property, with or without snow cover, the daily minimum and mean air temperature, a road icing effect index was defined and the accurate rate of forecast for the different grades was checked. The results show that there is a monthly and seasonal variation for icy roads. It appears mainly in winter and seldom in November and March. Its variation trend is a contrary phase with that of mean air temperature from November to March in Zhenjiang. If it snows or has snow cover in the current day or in the previous day, the ground temperature on the cement and asphalt roads is below or equals to 0 ℃ and lasts more than 16 hours, there will be icy roads influencing the traffic seriously. It appears mainly in the nighttime for icy roads. If it is in the daytime, it has serious icy roads in other times. Meanwhile, the effect of icy roads on the traffic in the daytime is more significant than that only in the nighttime. The road icing effect index could also forecast for continually icy roads, while the false alarm rate is relatively high. Related Articles | Metrics

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Analysis and assessment of solar energy resource in Heilongjiang province LIU He-nan,ZHANG Hong-ling,ZHU Hong-rui 2013, 29 (4):  89-93.  Abstract ( 403 )   PDF (1069KB) ( 518 )   Save Based on the observational data from 5 global solar radiation stations and 32 weather stations in Heilongjiang province from 1961 to 2010, the characteristics of the spatial-temporal distributions of solar energy resource were analyzed. The abundance and stability of solar energy resource were assessed. The results indicate that the average annual global solar radiation decreases, especially in January and December. The global solar radiation is the strongest in 1970s and weakest in 1980s. The distributions of the global solar radiation and sunshine duration are consistent, and both are more abundant in the west than in the east. The stability of solar energy resource is good in Heilongjiang province, especially in the west of the Songnen plain. It is suitable to build the solar energy power station because of the abundant and stable solar energy resource in the west of the Songnen plain. Related Articles | Metrics

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Geometry correction of MODIS data based on vector feature SUI Ming,LI Guo-chun,LI Gang,CAI Bing 2013, 29 (4):  94-99.  Abstract ( 396 )   PDF (1448KB) ( 507 )   Save The large scanning angle and multiple probe of MODIS detector make the scan image distorted. Based on the SWATH data processing strategy, the relationships of space location of the MODIS 1B data with different resolutions, the corresponding status between image data and longitude and latitude information were analyzed. In order to match the image data, the image was combined by the geographical locations considering the scan method of the MODIS detector, the ascending and descending orbit of the satellite, and the earth curvature and so on. The raster feature of data was replaced by vector feature in this method. The image pixel can be located more exactly through this method. The results indicate that the geometry correction can be done more accurately for MODIS data, so is for that of the sub pixel. This method could avoid information losing when the pixel is relocated, and it never generates BowTie effect. Related Articles | Metrics

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Assessment of the heating effect of electric warm-air machine in solar greenhouse and its economic investment LI Ning,LI Zhen-fa,SHEN Shuang-he,LI Chun,LIU Shu-mei,YU Hong 2013, 29 (4):  100-105.  Abstract ( 569 )   PDF (619KB) ( 483 )   Save The greenhouse heating was one of the main methods to enhance the growth environment of crop in winter. The energy-saving solar greenhouse was selected. The temporal and spatial variations of temperature in the solar greenhouse and the heating effects under the extreme weather condition and different outdoor temperatures were discussed by a heating experiment with an electric warm-air machine. The economic investment was also analyzed. The results show that the temperature in the greenhouse rises significantly and is distributed uniformly in the whole greenhouse after the heating by the electric warm-air machine. The average temperature in the heating greenhouse is 4.23 ℃ higher than in the control greenhouse, and the average minimum temperature in the heating greenhouse increases significantly. The average temperate  in the heating greenhouse is 4.24 ℃ higher than in the control greenhouse under the low temperature weather condition, while it is 4.48 ℃ higher  under the spare sunlight weather condition. The heating effect by the electric warm-air machine for the greenhouse is best when the outdoor temperature is -12 ~-4 ℃. The analysis of economic investment with the different heating methods suggests that the warm-air machine is an economic heating measure for its small investment, low energy consumption and high economic benefit. Related Articles | Metrics

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Effect of freezing-thawing on soil dissolved inorganic nitrogen and soil microbial biomass nitrogen in riparian zone FAN Zhi-ping, LI Sheng-nan,LI Fa-yun,GAO Hong-cui,YAN Jia-Liang 2013, 29 (4):  106-112.  Abstract ( 482 )   PDF (650KB) ( 426 )   Save Global climate change makes snow pattern of terrestrial ecosystems change in the middle and high latitude areas, which is critical to soil nitrogen cycling, and it can lead to changes of intensity and frequency of soil freezing-thawing cycles. The freezing-thawing cycles could affect soil nitrogen cycles through microbial biomass and community. The study was carried out in Dahuofang experimental forest watershed. The effect mechanism of freezing-thawing cycles on inorganic nitrogen content of soil was revealed, which could provide the references for assessing the risk of N loss in the riparian ecosystem. The results show that soil inorganic nitrogen content is in an increasing trend with the increasing times of freezing-thawing cycles. Different freezing temperature has the significant effect on inorganic nitrogen. The inorganic nitrogen contents are 34.9±0.9 mg/kg and 37.2±0.8 mg/kg after 10 freezing-thawing cycles with the -5℃/+5℃ and -20℃/+5℃ treatments, which are 1.21 and 1.41 times of initial inorganic nitrogen content of soil samples, respectively. Furthermore, freezing-thawing cycles and its temperature difference have the significant effect on soil NH4 +-N content (P<0.01). After 10 freezing-thawing cycles, soil NH4 +-N content is 4-10 times of soil samples for +5 ℃ treatment. Freezing-thawing cycles have the significant influences on soil NO3- -N content (P< 0.05), while its temperature difference has not the significant influences on NO3-N content (P>0.05). The response of soil microbial biomass nitrogen content to freezing-thawing cycles is significant (P<0.01). Thus, freezing-thawing changes increase the inorganic nitrogen content of soil. Because of less absorption of inorganic nitrogen by vegetation in early spring, the risk of soil nitrogen loss may increase with snow melting in study area. Related Articles | Metrics