Plateau Meteorology

Current Issue

28 June 2015, Volume 34 Issue 3   
  • Reanalyses of Precipitation Circulation and Vapor Transportation of Severe Dry and Wet Events in Summer in Arid Region of Northwest China
  • CAI Ying;SONG Minhong;QIAN Zhenag'an;WU Tongwen;LUAN Chen
  • 2015 Vol. 34 (3): 597-610.  DOI:10.7522/j.issn.1000-0534.2015.00049
  • Abstract ( ) PDF (8172KB) ( )
  • In order to further analyze main water vapor origin area and its transportation path for precipitation in summer in inland arid region of Northwest China(NWC), first, the advancements and problems of the water vapor transportation in inland arid region of NWC in past 5 decades were summed up and reviewed, then the many strong, dry and wet month(or day) events in summer in NWC were again selected and the further comparison analyses of their circulation and water vapor transportation were in detail done by using the observed precipitation data etc in past 50 years from National Information Center of China Meteorological Administration and the US NCEP/NCAR reanalysis ones. The main results are shown as follows. (1)There are many common views and progresses about the dry and wet circulation patterns in the arid regions of NWC summer, but it not trure about their water vapor sources and transportation paths. (2)The water vapor transportation analyses done in the past decades did not link closely with the dominate precipitation patterns, did not take fully the precipitation features of inland arid area into consideration, and also did not use the test stool of the model simulation. (3)Based on the diagnostic analyses in the paper and our earlier numerical simulation of water vapor, we point out that the main water vapor origin in the inland arid areas, NWC summer is off the southeast China(SEC) coast, With the aid of both the weather systems: typhoon going westward, West Pacific Subtropical High(WPSH) moving westward and Qidam Basin lows and the flows: southeaster jet on the SW side of WPSH, souther one on the west side of WPSH and the easter in Gansu Corridor, first, the water vapor off the SE coast are transport by the SE jet to Sichuan Basin; then, by the souther jet, to the east part of NWC; again then, by the Easter in Gansu Corridor, to Gansu Corridor and the east part of south Xinjiang. So called as 'three baton relay water vapor transport model with three flows plus two transfer stations'.
  • Different Physical Properties of Summer Precipitation Clouds over Qinghai-Xizang Plateau and Sichuan Basin
  • CHEN Ling;ZHOU Yunjun
  • 2015 Vol. 34 (3): 621-632.  DOI:10.7522/j.issn.1000-0534.2014.00036
  • Abstract ( ) PDF (7383KB) ( )
  • The statistical discrepancy of physical properties of summer precipitation clouds over the Qinghai-Xizang Plateau, Sichuan Basin and their transition region were analyzed, based on July and August CloudSat products from 2008 to 2010.At the same time, four examples from CloudSat, FY-2D TBB data and surface precipitation products were also analyzed to discuss how the different physical properties lead to the different precipitation of summer precipitation clouds over studying regions.The results showed that: (1) As to the macrophysical properties of clouds, the main precipitation clouds of the Qinghai-Xizang Plateau were Cu and Ci, low level clouds accounted for the largest proportion, it were Ns and Ci in Sichuan Basin and transition region.Compared with Basin, the clouds base was higher and top was lower in Plateau, it could rain while convection will not deep enough.In three regions, single layer cloud was easier to rain than multilayer one. (2) As for the microphysical properties of clouds, the main precipitation clouds of the Qinghai-Xizang Plateau was ice cloud, mixed cloud was second, the least was liquid water cloud, mixed cloud accounted for the largest proportion in Sichuan Basin.The clouds were mostly at the beginning of lifetimes in statistics, although the differences were not obvious, the effective radius and distribution width parameter of cloud ice particles over the Qinghai-Xizang Plateau were bigger and wider than those in the other two regions.Their number concentration were similarly, that could quicken the cold cloud processes.It was slower to developed ice cloud processes in Sichuan Basin than that in the Qinghai-Xizang Plateau.
  • Simulation of Impact of Roots on Soil Moisture and Surface Fluxes over Central Qinghai-Xizang Plateau
  • LI Kai;GAO Yanhong;CHEN Fei;XU Jianwei;JIANG Yingsha;XIAO Linhong;LI Ruiqing;PAN Yongjie
  • 2015 Vol. 34 (3): 642-652.  DOI:10.7522/j.issn.1000-0534.2015.00035
  • Abstract ( ) PDF (4794KB) ( )
  • The central Qinghai-Xizang Plateau is characterized by dense roots and high soil organic carbon (SOC) in the top soil, which has significant effects on the soil hydraulic and thermal dynamics. These effects are investigated by using the Noah land surface model with multi-parameterization options (Noah-MP) which is forced by the intensive observation data at Amdo site from May to September 1998. The physical processes in Noah-MP with notable impact on soil temperature simulations are primarily assessed. Further, by investigating the different influence of stratifying soil properties, SOC and roots on soil hydraulic and thermal dynamics, surface energy simulations, results are obtained following. There are six physical processes, such as surface heat exchange and radiation transfer, have larger influence on soil temperature simulation. SOC effect optimize soil liquid water simulation slightly, yet it still possess large dry bias in the topsoil. This bias is significantly reduced from -0.094 m3·m-3 to -0.016 m3·m-3 after considering roots effect. The simulated soil temperature in topsoil is lower than observation, but it has better performance in deep soil layers. At the same time, the bias of sensible heat flux and latent heat flux is reduced from 24.3 W·m-2, -22.5 W·m-2 to 6.0 W·m-2, 1.2 W·m-2, respectively.
  • Applicability of Soil Temperature and Moisture in Several Datasets over Qinghai-Xizang Plateau
  • LIU Chuan;YU Ye;XIE Jing;ZHOU Xin;LI Jianglin;GE Jun
  • 2015 Vol. 34 (3): 653-665.  DOI:10.7522/j.issn.1000-0534.2015.00034
  • Abstract ( ) PDF (7047KB) ( )
  • In situ soil temperature and moisture observations at 7 stations and one region (Naqu) over the Qinghai-Xizang Plateau are used to validate two reanalysis products (i.e. ERA Interim and CFSR) and six land surface model products (i.e. ERA/land, MERRA/land, GLDAS-NOAH, GLDAS-CLM, GLDAS-MOSAIC and GLDAS-VIC). Four statistical quantities, i.e. mean bias (BIAS), standard deviation of differences (σd), correlation coefficient (R) and ratio of standard deviations (σr/σobs), are calculated at each site, and the Brunke ranking method is applied to quantify the relative performance of the eight datasets for each variable and statistical quantity. The results show that for daily soil temperature CFSR has the best overall performance, followed by MERRA/land and GLDAS-CLM, while ERA Interim and ERA/land perform the worst. GLDAS-CLM tends to overestimate daily soil temperatures, while other datasets tend to underestimate soil temperatures at most observation sites, with ERA Interim and ERA/land having large cold bias exceeding -20℃. For soil moisture during unfreezing period (May to October), GLDAS-CLM shows the best overall performance, followed by GLDAS-NOAH and ERA Interim. CFSR, ERA Interim, and ERA/land have wet biases, with most of the biases between 0.05 and 0.20 m3·m-3, while GLDAS-NOAH, GLDAS-CLM and GLDAS-MOSAIC tend to be drier than observations.
  • Application of ERA Product of Land Surface Temperature in Permafrost Regions of Qinghai-Xizang Plateau
  • QIN Yanhui;WU Tonghua;LI Ren;XIE Changwei;QIAO Yongping;CHEN Hao;ZOU Defu;ZHANG Lele
  • 2015 Vol. 34 (3): 666-675.  DOI:10.7522/j.issn.1000-0534.2014.00151
  • Abstract ( ) PDF (2994KB) ( )
  • The land surface temperature(LST) is an important variable between atmosphere and ground surface. The LST can impact permafrost distribution and is also a significant parameter for mapping the permafrost distribution. In order to validate the ERA product of land surface temperature over the Qinghai-Xizang Plateau, the ERA product of LST with the observations at three metrological stations from 1 January 2011 to 31 December 2012 have been compared. And the biases, mean square errors, correlation coefficients, fractional error and index of agreement have been analyzed. The results showed that the ERA product of LST can reflect general characteristics of the three metrological stations in the permafrost region. But LST of the ERA product is a little lower than that of the observations, which Xidatan was 1.7℃ lower, Wudaoliang 1.0℃ lower and Tanggula 0.9℃ lower. The correlation coefficients and explained variances are extremely high, while the mean square errors of the reanalysis data were respectively -1.7℃, -1.5℃ and -0.9℃. The RMSE were 2.5℃, 2.6℃ and 1.7℃ at the three sites respectively. Though the LST of ERA product has some limitations applying in the permafrost regions of the Qinghai-Xizang Plateau, to some extent, it is convincible especially on the uneven distribution and low density of metrological stations in the Qinghai-Xizang Plateau. It is still regarded as an effective proxy data of the land surface temperature in the permafrost region of the Qinghai-Xizang Plateau.
  • Analysis of Relationship Between Sea Surface Temperature in Tropical Indian Ocean and Precipitation in East of Northwest China
  • YANG Jianling;LI Yanchun;MU Jianhua;WANG Suyan;WANG Min;TIAN Lei
  • 2015 Vol. 34 (3): 690-699.  DOI:10.7522/j.issn.1000-0534.2014.00010
  • Abstract ( ) PDF (6083KB) ( )
  • Most previous researches of Sea Surface Temperature Anomaly (SSTA) in the tropical Indian ocean influencing precipitation mainly focused on the eastern region of China. In recent years, the latest studies have found important climatic effects of the inter-annual first mode of the tropical Indian Ocean Basin Mode (IOBM). So it is necessary to study the influence of SSTA in the tropical Indian Ocean on precipitation anomaly of East of Northwest of China (ENC). Based on 99 meteorological stations monthly precipitation data in ENC, and monthly SST data of HadISST data set from Hardley center during 1961-2009, adopting MCA, correlation, regression and other statistical methods, the inter-annual and inter-decadal relationship between the precipitation in ENC and the tropical Indian ocean SST is analyzed in this article. It is found that the persisting anomaly of the IOBM in previous winter and spring is significantly corrected with precipitation anomaly main mode in ENC in subsequent May. In further the relationship is difference before and after mid 1970s, which being the climate shift year of north hemisphere. The relationship is not significant before mid 1970s, while after mid 1970s the relationship is strengthened and significant, with passing 95% significant test. Usually the warm (cold) Basin mode in previous winter and spring is corresponding to more (less) precipitation in subsequent May in ENC. The preliminary analysis is that the impact of the tropical Indian ocean basin mode on precipitation anomaly in ENC is a concrete manifestation of IOBM ‘Capacitor’ effect.
  • Analyses of Atmospheric Circulation of Tropical Indian Ocean Basin Mode Influencing Precipitation in East of Northwest China
  • YANG Jianling;ZHENG Guangfen;WANG Suyan;MU Jianhua;WANG Min;TIAN Lei
  • 2015 Vol. 34 (3): 700-705.  DOI:10.7522/j.issn.1000-0534.2014.00011
  • Abstract ( ) PDF (4100KB) ( )
  • Our previous study shows that since mid 1970s the persisting anomaly of the tropical India Ocean Sea Basin Mode (IOBM) in previous winter and spring is significantly corrected with precipitation anomaly main mode in the East of Northwest China (ENC) in subsequent May. In this study, using regression method, the atmospheric circulation anomaly and possible mechanism of the IOBM influencing on precipitation in ENC are studied. It is found that the warming IOBM can induce the responding of 'Matsuno-Gill Pattern' in the atmosphere and form the wave train over area from the tropical Indian Ocean to Europe to Asia at middle to upper troposphere level. The anomalous values of wave train increase with height increasing. ENC is just located between the negative center of Xinjiang to Balkhash Lake and positive center of East Asia, and just controlled by the pattern of ‘West Low and East High’, which is the typical circulation pattern of more precipitation in ENC. Corresponding to the wave train of height anomaly, there are three significant cyclone and anticyclone anomaly centers over Europe-Asia area. At upper level of 200 hPa, it is the large scale wind divergence anomaly over area from North China to ENC, and at lower level of 850 hPa it is the convergence over there. Concerned with the divergence at upper level and convergence at lower level, it induces the vertical ascending, which is advantage of more precipitation. The vertical ascending motion center is over area from North China to ENC. So it is said that the IOBM can influence the precipitation anomaly over ENC by inducing the wave train over Europe to Asia area at middle-upper troposphere, and informing anomaly circulation pattern of 'West Low and East High' over ENC. For the cold case of IOBM, it is vise verse.
  • Projection of the Future Drought over Yunnan and Its Surrounding Areas by RegCM4
  • WANG Meili;GAO Xuejie;SHI Ying;GIORGI Filippo
  • 2015 Vol. 34 (3): 706-713.  DOI:10.7522/j.issn.1000-0534.2014.00013
  • Abstract ( ) PDF (4852KB) ( )
  • Driven by the global climate model of BCC_CSM1.1, climate change over East Asia in the 21st century is simulated by a regional climate model, RegCM4.0, under the new emission scenarios of RCP (Representative Concentration Pathway). In the present study, the analysis is focused on Yunnan Province and its surrounding areas located in southwestern China. Simulations of present day climate (1986-2005) by RegCM4 are compared against observations to validate the model performance. The results show that RegCM4 can reproduce the observed annual cycle of the regional mean temperature and precipitation well, although a cold bias over the region and an overestimation of precipitation in the dry (cold) season can be found in the simulations. Significant warming and a general decrease of precipitation in both the dry (November to next April) and wet (May to October) seasons in the 21st century are projected by the model under RCP8.5 scenario. The changes show differences in spatial distribution in the two seasons. The drought events are measured by the indices of the maximum number of consecutive dry days (CDD), differences between precipitation and evaporation (P-E), and root zone soil water content (RSW). Analysis of their future changes indicates that the drought will continue and aggravate under the global warming. This is more profound in the dry season compared with the wet season.
  • Impact of Vegetation Fraction Algorithms on WRF Simulation over China
  • YU Lijuan;YIN Chengmei;HE Jianjun;YU Ye
  • 2015 Vol. 34 (3): 714-721.  DOI:10.7522/j.issn.1000-0534.2014.00041
  • Abstract ( ) PDF (6028KB) ( )
  • Based on MODIS NDVI, linear and nonlinear algorithms (hereafter referred as GI and CR algorithms respectively) are used to calculate vegetation fraction over China, and these data are used in Weather Research and Forecasting Model (WRF). The effect of different vegetation fraction data derived from GI and CR algorithms on WRF's simulation in July 2006 over China is investigated. The results show that large deviation of vegetation fraction calculated by GI and CR appears in semi-arid regions, and corresponding, WRF simulation has significant difference in these regions. In arid and humid regions, small deviation is found relatively, and not significant difference for WRF simulation. Utilizing vegetation fraction derived from GI algorithm, WRF have less biases in near surface average and maximum temperature compared with observations, while less biases in minimum temperature and good performance of hot weather for CR. Using vegetation fraction data derived from CR algorithm, WRF can better describe average, daily variation and spatial pattern of precipitation. There are some differences of WRF's performance in different regions between two vegetation fraction algorithms. Overall, the use of CR produces better performance on temperature and precipitation.
  • Relationship between Heavy Rainfall Process and Intramonthly Low-Frequency Rainfall in Flood Period and Their Possible Mechanism
  • WEI Xiaowen;LIANG Ping;HE Jinhai;MU Haizhen
  • 2015 Vol. 34 (3): 722-731.  DOI:10.7522/j.issn.1000-0534.2013.00184
  • Abstract ( ) PDF (6753KB) ( )
  • Using daily observed precipitation data from 753 stations of China from 1981 to 2010, NCEP/NCAR daily reanalysis data and real-time weather map, selecting 32 large-scale persistent heavy rainfall processes in the middle-lower Reaches of the Yangtze River, the relationship between the processes and intra-monthly (10~30 d) low-frequency rainfall and possible forming mechanism of the process are analyzed. The results suggest that: (1) Rainfall in the middle-lower Reaches of the Yangtze River has significant intra-monthly low-frequency oscillation (LFO). Most large-scale persistent heavy rainfall processes are in its peak stage. (2) Before the peak phase of LFO rainfall for Meiyu flood period, the west Pacific subtropical high extends northwestward, upper and lower jet streams strengthen. At peak phase of LFO rainfall, upper, middle and lower circulation coordinate with each other very well. While before the peak phase of LFO rainfall for typhoon flood period, with the southeastward retreating of subtropical high, lower jet streams extend southward, cooperating with the upper jet streams, which provide favorable conditions for the heavy rainfall. (3) At Meiyu flood period, LFO wave train in north Pacific propagates westly and LFO vortex in the northeast Asia propagates southward. They converge at the middle-lower Reaches of the Yangtze River. At the same time, with the northward propagating of high value system of LFO geopotential height in South China Sea, the corresponding distribution of "south high north low" in LFO geopotential height field contributes to the heavy rainfall process. For typhoon flood period, with the northwestward propagation of the LFO wave train from the tropical west Pacific to the Japan Sea, LFO cyclone at northeast of Philippines with LFO anticyclone on its north moves to the middle-lower reaches of the Yangtze River and Northeast Asia at peak phase of LFO rainfall, which contributes to the severe convergence and results in the heavy rainfall process. (4) Positive anomalous convection over east of Philippines can be used as previous tropical signals of the heavy rainfall process at Meiyu and typhoon flood period,which is in advance of rainfall peak phase about 10 days.
  • Diagnostic Analysis in the Difference between Two Stages of a Torrential Rain Process
  • CHEN Peng;LIU Yi;LIU De;HE Jun;CHEN Guichuan;LIAO Zhiyi
  • 2015 Vol. 34 (3): 732-740.  DOI:10.7522/j.issn.1000-0534.2014.00046
  • Abstract ( ) PDF (9114KB) ( )
  • With NCEP reanalysis data、 WRF model simulated high resolution output data、 automatic station precipitation data and radar data、 radar data, a diagnosing analysis and numerical simulation is made of a heavy rain in Chongqing from 14 to 16 August 2010. The result indicate that the heavy rain processes which divided two stages, has two precipitation system: the first stage of the main precipitation system is the low level shear line; The second stage of precipitation system are the low level shear line and 850 hpa of southwest vortex, and the second stage of the rainfall is larger and has longer duration. The vertical wind profile of time evolution shows that the heavy rain in the process of development, strong low-level southwest wind speed downlinking and the existence of the low-level shear convergence has a very important role for enhancement of the mesoscale convective system. The numerical simulation analysis shows that in the first phase of the heavy rain process, weak cold advection influence the rain area, under the impact of low-level shear line, cause air mass convergence in horizontal direction and trigger the mesoscale convective system development; in the second stage, the high-level strong cold air poured in precipitation area, the vertical ascending motion near the low vortex coupling interaction the upward movemen near 700 hpa shear lineafter the 850 hpa vortex eastward to Chongqing northeast area,which forces the low-level warm moist air to lifting and triggers the mesoscale convective system again.
  • Characteristics of Rainstorm Processes under the Blocking Pattern in Inner Mongolia
  • CHANG Yu;HAN Jingwei
  • 2015 Vol. 34 (3): 741-752.  DOI:10.7522/j.issn.1000-0534.2014.00033
  • Abstract ( ) PDF (13585KB) ( )
  • By using conventional observation data, 1°×1° NCEP reanalysis data, TBB (Temperature of Black Body) data of FY-2E and 1-hour precipitation amount, the diagnostic analyses of the rainstorm processes in the whole Inner Mongolia from 24 to 31 on July 2012 are done. The results show that: (1) The eastward extension of South Asia high, block high pressure system near Lake Baikal and the northward position of the west Pacific subtropical high is the stable maintenance of the large-scale circulation which is very favorite for rainstorm occurring. (2) The surface convergence, shear line and the vortex on 700 hPa are the direct raining system. Short-time strong precipitation is directly made by mesoscale convective system(MCS). The areas of the mesoscale rainy clusters emerge mainly in the maximum gradient of TBB on the edge of MCS where the cold air flows into. (3) The frequent action of the South China Sea monsoon supplies abundant moisture vapor for rainstorm. Before rainstorm occurs there are lots of convective instability energy in the low troposphere. The lifting mechanism caused by the terrain and the couple between the right of upper level jet entrance and the left of low level jet export triggers rainstorm. (4) Supplying poor moisture vapor is the main reason that this area occurs less rainstorm in the western region of Inner Mongolia.
  • Characteristics of Air Temperature in the Southern and Northern Slopes of Tianshan Mountains
  • PU Hongzheng;HAN Ti;ing;CHENG Peng;LI Xiangying
  • 2015 Vol. 34 (3): 753-761.  DOI:10.7522/j.issn.1000-0534.2015.00050
  • Abstract ( ) PDF (3670KB) ( )
  • Based on the observation of air temperature data in the Southern and Northern Slopes of Tianshan Mountains in recent 50 years, the change tend of annual mean temperature, different time of beginning spring and summer, the characteristics of annual maximum temperature and minimum temperature and annual temperature range are analyzed. The results show that air temperature increased in 1997 in the southern and northern slopes of Tianshan Mountains and that the change tend of the temperature is maximum, 0.402℃·(10a)-1, in the northern slope of the Urumqi station. It suggests the beginning dates of spring and summer in the southern slope of the Kuerl station are earlier than that in the northern slope of the Urumqi Station. It enters the spring in April in the northern slope of the Urumqi Station and in March in the southern slope of the Kuerl station. The temperature of beginning spring in the northern slope of the Urumqi station is one degree higher than that in the southern slope of the Kuerl station. It begins the summer in June and May in the northern slope of the Urumqi station and in May in the southern slope of the Kuerl station. The temperature of beginning summer in North-South slope of the Tianshan Mountains is relatively close. In addition, a statistical analysis shows that annual maximum temperatures decrease with increasing elevation and that variation of annual minimum temperatures is different in the southern and northern slopes of Tianshan Mountains. Annual temperature range decreases with increasing elevation in the southern and northern slopes of Tianshan Mountains. The inversion in the northern slope is significantly higher than that in the southern slope in January. The linear trend of air temperature difference between Xiaoquzi and Caijiahu in the northern slope is -0.208℃·(10a)-1. But the linear trend of air temperature difference between Baluntai and Hejing in southern slope is 0.236℃·(10a)-1.
  • Improvements of Building Energy Model and Anthropogenic Heat Release from Cooling System
  • ZHENG Yulan;MIAO Shiguang;ZHANG Qi;BAO Yunxuan
  • 2015 Vol. 34 (3): 786-796.  DOI:10.7522/j.issn.1000-0534.2014.00035
  • Abstract ( ) PDF (3211KB) ( )
  • Since the urbanlization in China is accelerating, the effect of heat-release of building cooling system on urban climate is bigger and bigger. Aimed at this situation, taking the case of 6-7 August 2010, (typical sunny day case in the Beijing area in summer), to carry out the research about the building energy model and the anthropogenic heat release of cooling system. It's found that the electrical energy consumption of different uses of the buildings has different diurnal variations, and it's also mostly related to meteorological factors. Based on these foundations, the simulation to energy consumption and heat-rejection of cooling system (air-condition) is performed with the modified Build Energy Model(BEM). Firstly, according to the features of the diurnal variations of electrical energy consumption, simulate the heat rejection of disparate uses of buildings. Analysis shows that among the thermal load, the percent of heat conducted by walls and windows is more than 60%, the rate of heat produced by humans and equipment is about 30% and received through the ventilation is 5%~6%. Secondly, a sensitivity analysis of a few parameters vastly affecting the result is carried out. The most important factor of building parameters is building height, when it varies from 18.3 m to 12 m and 6 m, the building heat-release will decrease 24.3% and 49.6% respectively. The second important parameters following building height are wall-conduction and ventilation coefficient.The heat-release can rapidly raise 94.4% while the target temperature falling from 25℃ to 24℃. Finally, the result of distribution of sensible heat and latent heat is calculated with the rate of the diverse air-condition in China, the value is 12.69 W·m-2 and 45.87 W·m-2 (about 22% of the peak value is sensible heat and the remaining part is latent heat in a single day). These results will laid the foundation for building thermal effect on urban climate research.
  • Study on Application of AOD Information in Forest Fire Detection
  • ZHANG Jie;ZHANG Wenyu;WANG Yanfeng;FAN Guangzhou;HAN Tingting;LIU Haiwen
  • 2015 Vol. 34 (3): 797-803.  DOI:10.7522/j.issn.1000-0534.2014.00023
  • Abstract ( ) PDF (2252KB) ( )
  • The limitation of existing MODIS fire detection algorithm appears when it is applied to monitor forest fires in different season or in different regions. In response to these problems, the smoke plume identification in forest fires over complex surface types is studied to improve detection ability of open flame fire spots and cool smouldering fire spots. According to the effect of smoke plume diffusion on atmospheric aerosol distribution, a detection method for the smoke plume is offered as potentiating tools to identify fire pixels by extracting atmospheric Aerosol Optical Depth (AOD) information from fire areas. Based on the 6S (Second Simulation of a Satellite Signal in the Solar Spectrum) radioactive transfer model, the Dark Target (DT) method is used to retrieve AOD form MODIS data in many fire spots and background areas. In addition, the sensitivity of AOD cumulative effect to the smoke plume diffusion in different azimuth directions and different diffusion ranges is discussed. The results show that AOD retrieved by DT method could stand for the distribution characters of smoke volume, as well as indicate the direction and the rough range of smoke spread. The values of AOD in 32 azimuth directions are accumulated when the distance from the centre is 10 km, if the true fire spots are thought as the centre of a circle. The most remarkable difference of AOD cumulative value is found by comparing the leeward side to the windward side. The ratio of the two is more than ten to one. So it will provide an effective auxiliary criterion for MODIS fire detection algorithm to avoid missing disperse fire spots, especially cool fire spots.
  • Comparative Case Study on the Observations between the Space-borne Radar and Ground-based Radar
  • WANG Zhenhui;LI Shengyin;DAI Jianhua;LI Nan
  • 2015 Vol. 34 (3): 804-814.  DOI:10.7522/j.issn.1000-0534.2014.00031
  • Abstract ( ) PDF (5923KB) ( )
  • This paper obtained three cases of precipitation in Shanghai in the second half year of 2007 after applying the Geometry-matching method to do the Temporal-Spatial Matching of radar data derived from the precipitation radar (PR) on the TRMM (Tropical Rainfall Measuring Mission satellite) and from Shanghai Ground-based Radar (GR) in their effective sampling volume. To compare the difference between the volume-matched PR and GR radar reflectivity factor in consideration of the different frequencies of PR and GR, we adjust the echo intensity detected by Ground-based Radar (GR) which is in S-band to that value which is detected by Ku-band Radar (Ku-adjusted), and analyze the PR-GR deviation from different altitude layers and various precipitation types. The results show that: (1) The distribution and structure of PR are in accordance with GR echoes as a whole, whereas the PR echoes are more intense than the GR echoes generally. (2) Within and below the Bright-band, there is a high degree of correlation between PR and GR reflectivity data. (3) Due to the impact of beam filling and the attenuation of echoes, the mean deviation of PR-GR is larger in high altitude layer than in low altitude layer. (4) The variation characteristic of PR and GR echoes intensity has a higher degree of consistency from stratiform precipitation samples than convective precipitation samples. (5) In general, the GR data is closer to PR data after the Ku-adjusted.
  • Application in Classification of Precipitation Clouds Using Vertical Sounding Radar in Beijing
  • HUANG Yu;RUAN Zheng;LUO Xiuming;JI Lei
  • 2015 Vol. 34 (3): 815-824.  DOI:10.7522/j.issn.1000-0534.2014.00014
  • Abstract ( ) PDF (12052KB) ( )
  • Wind profile radar using coherent accumulation technology to improve radar sounding sensitivity, have being applied in precipitation cloud body vertical measurement, which can obtain high resolution entire spectrum information of cloud body return signal. On the basis of precipitation weather statistics for many years, aiming at characteristics of rainfall in Beijing Yanqing, a precipitation cloud classification scheme based on spectral parameter (echo intensity, velocity, spectral width) of wind profile radar have been put forward in this paper. Classification scheme divided precipitation data into shallow convection, shallow stratiform, deep convection, deep stratiform, transition-exclusive and transition-inclusive six types of precipitation. According to this classification scheme, by means of combining the wind profile radar data with dual polarization radar data and simultaneous rain gauge data, the paper analyzed two precipitation processes on September 1, 2012 and June 27, 2013 in Yanqing. The results show that, the vertical profiles of wind profile radar spectral parameter can describes the vertical structure of precipitation clouds accurately, the development trend of echo intensity and the trend of surface precipitation matched very well. When precipitation appears convection, the surface precipitation rate increased obviously, along with high speed region and high spectral width in upper air region. Using the wind profile radar-based classification scheme to distinguishing the type of clouds can reduce the probability of precipitation type misjudgment.
  • Characteristics of Lightning Activity and Radar Reflectivity during Typhoon ‘Morakot’ Landfall
  • WEN Ying;ZHAO Yang;ZHAO Guo;KONG Xiangzhen
  • 2015 Vol. 34 (3): 832-841.  DOI:10.7522/j.issn.1000-0534.2015.0036
  • Abstract ( ) PDF (9761KB) ( )
  • Using the lightning data from World Wide Lightning Location Network (WWLLN), typhoon track and intensity data from the Best Track Data Sets (CMA), radar reflectivity of the weather radar from Fujian Meteorological Administration and the NCEP/NCAR Global Reanalysis Data, to analyze the characteristics of lightning activity and radar reflectivity in typhoon ‘Morakot’ (0908) during the two processes of landfall in Taiwan and Fujian. The analysis showed that more lightning occurred in the outer rainband and less lightning occurred in the central area and inner rainband. The first landfall in Taiwan caused more lightning than the second landfall in Fujian. At 6 km height, lightning was prone to occur in the rear or round of the central area where the reflectivity value was high and the area was large. The lightning number was low at the beginning of echo formation, and increased when the convective systems developed stably. During the period of typhoon entered into Taiwan Strait and made landfall in Fujian, the maximum echo height and lightning number had a positive correlation.The lightning activity was affected by both the vertical movement and topography. Lightning concentrated on the land at the rear side area of cyclonic horizontal wind flowed into the vertical upflow central areas on 500 hPa. The position and intensity of the vertical upflow central areas influenced the position and number of lightning activity.
  • Some Properties of Negative Cloud-to-Ground Flashes over North Anhui Based on Continuous Electromagnetic Field Observations
  • XU Weiwei;LI Zaiguang;ZHU Baoyou;MA Ming
  • 2015 Vol. 34 (3): 850-862.  DOI:10.7522/j.issn.1000-0534.2013.00198
  • Abstract ( ) PDF (4221KB) ( )
  • By analyzing wideband electromagnetic field waveform records obtained by the system capable of recording electric and magnetic field of distant lightning discharges in a continuous manner, overall 3141 negative cloud-to-ground flashes were identified through manual selection for a thunderstorm occurred in Anhui, Huaibei Area on 9 July 2012, among which 15.5% contained only single stroke. The maximum number of strokes per flash was 18 and the average number of strokes per flash was 4.2. The percentage of single-stroke flash and the mean number of strokes per flash showed significant variations during the storm life cycle. The average duration of the negative flashes was 363.7 ms. 10031 inter-stroke intervals gave a geometric mean value of 75.3 ms. It seemed that CG flashes during active stage had slightly shorter intervals than other stages. The amplitude ratio of subsequent stroke to the first stroke presented a geometric mean of 0.49 for 10031 subsequent strokes, confirming that subsequent strokes were generally much weaker than first return stroke. However, the cases of amplitude of subsequent strokes greater than which of first return strokes is not rare. Our data indicated that about 34.8% of multiple-stroke flashes contained at least one subsequent stroke whose amplitude is greater than that of the first stroke and 19.7% of all subsequent strokes whose amplitude is greater than first return strokes. Both the relative amplitude and the preceding time interval of subsequent strokes showed a significant dependence on the stroke order. About 38.6% of negative cloud-to-ground flashes were observed to associate with discernible bipolar pulse activities of preliminary breakdown, with a geometric mean value of 2.3 ms preceding the first strokes.
  • Quantitative Evaluation on Requirement of Obstacle Distance for Wind Observation
  • TIAN Dongxia;GUO Jianxia;GUAN Yanhua;CHEN Ting;XUE Zhengzheng
  • 2015 Vol. 34 (3): 870-880.  DOI:10.7522/j.issn.1000-0534.2014.00052
  • Abstract ( ) PDF (7058KB) ( )
  • In order to evaluate the requirements of the obstacle distance from the anemometer, a set of numerical simulations and sensitivity experiments on an isolated building by Computational Fluid Dynamics (CFD) model were carried out with verifying by the field experiment at Guyuan, Hebei Province. The results indicate that: (1) The range of 90% inflow speed is 3 times the height of the building in windward side, and 28.5 times of it in leeward side. Meanwhile, the range of 10 deviation to inflow wind direction is 1.4 times the height of the building in windward side, 6.8 times of it in leeward side, 2.8 times of it in lateral side and 4 times of it in vertical height. (2)By the sensitivity analysis of inflow speeds, building thickness, building height, building angular width and inflow directions, the requirements for the ratios of the distance to the height of building increase with the increment of the inflow speeds, while that will be decreased with the increase of the thickness of the building. If the height of the obstacle below than 6 m, it seems not significantly to disturb the wind speed and direction at 10 m. If the height of the obstacles more than 6 m, the requirements of the ratios of the observed point distance to the height of the building will be reduced with the increase of the height of the building, and be enlarged with the increase of the building angular width. When the inflow cross over the building by 45°, the influenced scope of wind speed will be enlarged, as well as the horizontal affected area of wind direction, but the scope of lateral side for wind direction will be reduced.

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