Current Issue

• Characteristic of a Couple of Vortexes on the East Sideof Tibetan Plateau from Winter to Spring and TheirImpact on the Weather and Climate in China
• 2009 Vol. 28 (5): 945-954. 
• Abstract ( ) PDF (6683KB) ( )
• Affected by Tibetan Plateau terrain, the lower\|level west wind is split on the east side of Plateau and forcedto flow around it. There are two branches of the westerly, one flow to the south of the Plateau forming a positive vorticity belt, and to the south of the Plateau forming a negative belt. They converge on the east side of the Plateau. Utilizing the NCEP/NCAR reanalysis data from 1951 to 2004, we discoveredthat the two vorticity belts were the most obvious on 700 hPa, and there were a couple of vortexes on the east of the Plateau all the year round. According to the monthly position and intensity of the vortexes, a Detouring Flow Index (DFI) from winter to spring is defined as the difference between the average vorticity of the positive vortex and the negative one, quantitativelycharacterized the Function of Detouring Flow around Tibetan Plateau (FDFTP). From 1951 to 2004, the FDFTP is stronger in spring than that in winter in 2/3 years. Interdecadal variation of the DFI is dominant in winter, and the DFI is obviously enhanced in last 50 years; both interdecadal and annual changes of the DFI are not significantin spring. From winter to spring, the enhanced FDFTP is favorable to transport cold air to northern China, induced low temperature in northeast China and northern part of Xinjiang Province. In spring enhanced FDFTP is also favorable to transport warm and wet current to southern China, induced high temperaturethere. The meeting of cold and warm air near 31°Nmay cause heavy rain in the Yangtze\|Huaihe regions. From winter to spring, intensity of the westerly belt in middle latitude in Asia is one of important effect factors to the FDFTP.

• Research on Applicability of RAMS under HeterogeneousLand Surface in Jinta Oasis, Gansu
• 2009 Vol. 28 (5): 966-977. 
• Abstract ( ) PDF (6919KB) ( )
• To test the simulation performance of the RAMS model in Jinta, Gansu, a sunny day process on 2~3 July 2005 in Jinta oasis and its surroundings was chosen, then a 48 h simulation for the chosen weather process have been running with the triple\|nested in RAMS4.4 and MM5V3.6 models; again then the simulated and observed results for the near surface temperature, humidity, wind speed, surface energy at Jinta Oasis, Gobi and Desert sites on 2~3 July 2005 were compared with each other. The main conclusions are as follows: The simulation of near surface temperature on oasis, desert and Gobi is better. The daily changes of near surface relative humidity is exactly simulated. The simulated results reappear \!the old island effect\"of oasis and \!inversion humidity phenomenon\"of desert which is near to the oasis. The simulated surface latent heat fluxes are more consistent with observations than surface sensible heat fluxes on oasis. The simulated surface sensible heat fluxes are better than latentheat fluxes on Gobi and desert. The simulated net radiation is consistent with observations on three different surface. The comparison between RAMS results and MM5 results show that the net radiation and sensible flux on different surface simulated by RAMS are better than MM5. The bias between simulated wind and observation is big, because onflow is randomicity, the great mass of bias result from nonlinearbias.

• Analysis on Simulation of Characteristic of Land Surface EnergyFlux in Seasonal Frozen Soil Region of Central Tibetan Plateau
• 2009 Vol. 28 (5): 978-987. 
• Abstract ( ) PDF (5066KB) ( )
• Using the observed BJ site data from CEOP Asia\|Australia Monson Project on the Tibetan Plateau (CAMP, 2001\_2005) from 1 August 2002 to 31 August 2003, the land surface energy flux characteristics in seasonal frozen soil region of central Tibetan Plateau were simulated by the Simultaneous Heat and Water〖KG*2〗(SHAW) model. The model closely captures the pattern of the surface energy flux, including net short wave radiation, net long wave radiation, net radiation, soil heat flux, sensible heat flux, and latent heat flux. Net short wave radiation and net long wave radiation〖KG*2〗were simulated well. The simulated results of net radiation and soil heat flux during summer half year were also well, but that of them during winter half year is slightly larger than the observed. The simulated sensible heat and latent heat flux have a reasonable〖KG*2〗seasonal change. Furthermore, the Bowen ratio calculated by simulated sensible heat and latent heat can indicate energy conversion〖KG*2〗of solar radiation during different seasons.

• A Comparative Study of the Three Land Surface Modelsin Simulating the Soil Moisture Profile
• 2009 Vol. 28 (5): 988-996. 
• Abstract ( ) PDF (3984KB) ( )
• Considering different finite\|difference techniquesand different numbers of soil layers used for solving the soil moisture equation amongthe differentland surface models (LSMs), three land surface models are compared in the context of simulating the soil moisture profile under the three upper boundary conditions(BCs) (i.e., a fixed evaporation rate, a fixed infiltration rate and a fixed surface soil moisture) with a finely spaced grid with 101 layers and a coarser grid with 11 layers. Also the impact of soil textures are took into an account. The results show that if the soil along depth is homogeneous (i.e. one soil type with fixed percentages of sand, clay and loam), the main difference among the soil moisture profiles simulated with the three schemes is that the infiltration of soil water with the CLM is faster than that with the other two models, and with the decrease of soil layers from 101 to 11, the soil moisture profile especially at the last three layers is inconsistent with that simulated with the fine grid; if the soil along the depth is heterogeneous(i.e. still one soil type but with different percentages of sand, clay and loam in each of 101 layers), the difference of simulated soil moisture profiles is enlarged and only the soil moisture profile with the ECMWF LSM is continuous. With the change of LSMs and the upper BCs, the rms difference between the soil moistures simulated respectively with the fine and coarse grids is not consistent: The rms difference from the CABLE generally is the largest except with the first upper BC and the RMS with the second and third BCs is larger compared with the first BC. The results imply that the impact of the numberof soil layers should be taken into account when we intercompare the different land models or compare the simulating results with the observations.

• Effects of Axial Orientations of Rotating Spheroidal Raindropson Polarimetric Measurements of Dual\|Polarization Radar
• 2009 Vol. 28 (5): 997-1005. 
• Abstract ( ) PDF (3396KB) ( )
• Based on the theory of electromagnetic scattering by small rotating spheroid particles, studies are made of axial orientation features of small rotating spheroid raindrop groupsso as to establish the relationship between axial orientations of the raindrop groupsand wind direction, elevation of the radar antenna. Considering the propagation effects in rainfall, here has analyzed the effectof axial orientation ondual\|polarization radar measurements, such as ZDRandLDR. The results providea theoretical base for improvingthe data accuracy of dual\|polarization Doppler weather radar.

• Preliminary Analysis on Formation of Electrical Characteristics ofThunderstorm in Different Altitude Regions in Chinese Inland Plateau
• 2009 Vol. 28 (5): 1006-1017. 
• Abstract ( ) PDF (4113KB) ( )
• The electrical characteristics of thunderstorms in four regions with different altitudes, including Naqu of central Tibetan Plateau, Datong of Qinghai, Zhongchuan and Pingliang of Gansu, have been analyzed. The results show that the electrical characteristics of thunderstorms in four regions have the difference and commonness. According to the polarity of electric field underneath thunderstorm, the thunderstorm in Chinese inland plateau can be divided into two types, normal\|type and special\|type, with the former being similar to that in the lower altitude regions in summer and the later characterized by a larger\|than\|usual lower positive charge center (LPCC) at the base of thunderstorm. The ratio of special\|type thunderstorm increases with the altitude of the region. By combining the meteorology parameters, the electrical characteristics of thunderstorm in four regions are discussed in detail. It is find that some of parameters have obvious difference in study regions, especially, the temperature difference of surface and air at 2 m highs (T0~2m) and warm cloud depth (WCD) have obvious indication on the intensity of LPCC. Usually, a larger value of T0~2mand smaller value of WCD indicate a stronger LPCC of thunderstorm, while a smaller value of T0~2mand larger value of WCD induced thunderstorm with a weaker LPCC.The results of model show that the intensity of charge region for two types of thunderstorm hasobvious difference because of the density of precipitationparticles. The intensity of LPCC is likely to be directly influenced byupdraft and WCD ofthunderstorm.

• Analyses on Regular Pulses Burst in ElectromagnetismRadiation of Lightning
• 2009 Vol. 28 (5): 1018-1024. 
• Abstract ( ) PDF (2519KB) ( )
• A special lightning discharge phenomena named as Regular Pulses Bursts(RPBs) was analysed. The results show that the RPBs exist in all 69 lightning discharges during 30 minutes. The 190 RPBs in six typical lightning was detailedly analysed. The typical width of pulses was about 1 μs, and time interval varied from 4 to 8 μs. Four types, normal RPBs, back RPBs, symmetry RPBs, reversal RPBs were classified according to the time interval and pulse polarity. There was no obvious difference between RPBs in negative cloud to ground(CG) lightning and that in intracloud lightning(IC), but in positive CGs most of the RPBs′ polarity is changeful. The analysis that, the variety of RPBs may be corresponding tothe extended process of streamer among few small charge region.

• The Lightning Radiation Field Spectra of Cloud\|to\|Ground,Intra\|Cloud Flashes and Narrow Bipolar Eventsin the Intervals of 0.1 to 40 MHz
• 2009 Vol. 28 (5): 1025-1033. 
• Abstract ( ) PDF (2917KB) ( )
• The broadband radio frequency(RF) observations of cloud\|to\|ground(CG), intra\|cloud(IC) flashes and narrow bipolar events (NBE) at \!Guangzhou Field Experiment Site for Lightning Research and Testing\" during the summer of 2008 were conducted. The electromagneticradiation produced by negative CG return strokes, initial discharge of IC flashes and NBEs have been analyzed using the Fourier method to obtain amplitude spectra for frequencies from 0.1 to 40 MHz.The results indicate that the spectral amplitude of all the three kinds of lightning discharges decrease in different rates with the frequency increasing. The spectral of the negative CG return strokes has a slow decreasing rate as f-0.8between 6 MHz and 28 MHz; whilethe spectral of the initial discharge of IC flashes has a consistencedecreasing with rate of f-1.2to f-1.4 and the spectra amplitudetends to be similar to thatof the return strokes. The spectrum of the NBEs showsa higher radiation energy over the entire frequency interval, especially above 10 MHz, being 20 dB higher than that of other discharges.

• Analysis on Mesoscale Character to Ocean\|EffectSnowstorm Using Single\|Doppler Radar Data
• 2009 Vol. 28 (5): 1034-1043. 
• Abstract ( ) PDF (8651KB) ( )
• Mesoscale analysis is conducted on the ocean\|effect snowstorm which occurred in Shandong peninsula from 6 to 7 December 2005 by EVAP retrieved wind method based on single\|Doppler weather radar data, original radial velocity, reflectivity, automatic meteorological stations and upper air chart. The results are as follows: Firstly, the radar echo with a narrow belt shape moves very slowly and almost stationary. There is wind direction shear in radial velocity, and snowstorm doesn′t occur at the same time in Yantai and Weihai. These are the symbol character of ocean\|effect snowstorm. Secondly, mesoscale shear in horizontal wind is found in the retrieved wind fields show, which is corresponded with strong echo belt. The position of shear determined the area of snowstorm. Thirdly, there are three airflow, include northwest, southwest and northeast wind, and the southwest warm advection is from 850 to 700 hPa.So this snowstorm is not the pure northwest airflow. Warm advection is good for micro\|physics, seed/feed mechanism strengthens, which is not obvious in normal observational data.