Abstract:According to the requirement for major field-crops' growth and development on weather and climate conditions in Canada,principles of agricultural meteorology and climatology,as well as impacts and trends of global climate change on the crop production,six key agrometeorological factors(extreme air temperature,heavy precipitation,strong wind,freezing,extreme soil moisture and effective heat-energy conditions for crop production) were selected for development and evaluation of twelve critical agrometeorological indicators(cool spell and heat wave days,maximal daily and ten-day precipitations,maximal daily wind speed,strong wind days,frost-free and freezing days,standardized precipitation index,seasonal water deficit,effective growing degree days and crop cumulative heat units).They can be used for scientific regionalization and rational development of different types of field crops,including warm season crops and cool season crops of annual herbaceous species,and over-wintering crops of biennial and perennial herbaceous and woody species in various agricultural regions across the country.This study is also based on plant growth and development requirements for cardinal temperatures and water conditions for three types of major field crops and actual weather and climate characteristics during crop growing and overwintering seasons in any agricultural years to determine growing season starting and ending days of various field crops in Canada.The results can be used for rational arrangement,optimal selection and proper plantation of suitable field crops in various agricultural regions of the country,efficient farm operation and management,science advice,policy development and decision-making,as well as similar scientific researches in other countries and regions in the future.

Abstract:Floods occured frequently in southern part of the south of Yangtze River valley during early summer from middle May to middle July.Based on the daily precipitation data from 200 stations in the south of Yangtze River valley during 1961—2010,this paper studies the temporal-spatial distributions and evolution characteristics of the early summer precipitation.Results show that,as the transition for the Early Rainy Season in South China to the Meiyu period in the Yangtze-Huaihe River Basin,the East Asia summer monsoon rain belt takes a stay over southern part of the south of Yangtze River valley,which brings about the distinct precipitation concentration period and concentrated region during the early summer.The concentrated region lies between 27.5—29.5°N,around the boundary of Zhejiang,Jiangxi,Fujian and Anhui provinces about.The precipitation concentration period occurs from 10 to 30 June.The early summer precipitation and rainstorm days have not conspicuous increase or decrease trend but the longest continuous rain days are reduced slightly in this region in recent 50 years.The early summer precipitation has significant 2—3 and 5—6 years periodical oscillations,and there are three abrupts occured in 1979,1987 and 2001.

Abstract:Based on the monthly precipitation data of 160 stations and daily rainfall data of 753 stations provided by the National Climate Center of china,the daily global OLR(outgoing long-wave radiation) data from National Oceanic and Atmospheric Administration,and the NCEP/NCAR reanalysis data,this paper studies the characteristics of low frequency oscillation of summer precipitation and convection over the Yangtze-Huaihe basin during the drought/flood and drought-flood-coexistence(DFC) years.Results show that summer rainfall over the Yangtze-Huaihe basin has multi-scale periods,which are remarkably different in drought/flood and DFC years.The 8—16 d quasi-biweekly oscillation(QBWO) plays an important role in drought years,while the 16—32 d period and QBWO are found to coexist in flood years.The 16—32 d oscillation also occurs in DFC and common years,accompanied with comparatively weak QBWO,which seems more significant in DFC.Thus,QBWO may be regarded as a vital factor for summer rainfall variation.On the other hand,the oscillation period of OLR is highly correlated with that of summer rainfall.As regard to the propagation of low frequency convection,it is found that the 8—16 d(16—32 d) low frequency convection mostly propagates in the southward(westward) direction in the typical drought(flood) years.

Abstract:Based on the hourly observations of 14 automatic weather stations in Tianjin,the Beijing radiosounding data,and the 6-hourly surface conventional observation data in Tianjin during summer 2008,this paper studies the relationship between the sea-land breeze and the diurnal characteristics of urban heat island in Tianjin.Results show that,under the atmospheric stable stratification condition,the diurnal variation of urban heat island intensity in Tianjin increases on the sea-land breeze days compared to the non sea-land breeze days.The sea breeze can cool the city,reduce the urban heat island intensity,and delay the appearance of the urban heat island in the nighttime,while the land breeze can significantly enhance the urban heat island intensity at night.We also find that the urban heat island intensity is closely related to the distance of sea breeze propagating.On the sea breeze days,when the synoptic scale geostrophic winds are in the same direction with the offshore wind,the sea breeze can only spread short distance;when the synoptic scale geostrophic winds are in the same direction with the onshore wind,the sea breeze can propagate farther;when the sea breeze can only reach Jinnan,Dongli or Ninghe stations,the urban heat island intensity in Tianjin has the maximum increase;with the increasing of sea breeze propagating distance,the overall increase rate of urban heat island intensity decreases.

Abstract:Based on the daily precipitation data of 88 stations in East China during 1961—2010 the temporal and spatial variation characteristics of yearly,seasonal,and monthly rainfall and rainy days in East China are investigated by using statistical diagnostic methods such as trend analysis and abrupt change detection.Results show that the secular trend variation of yearly rainy days is contrary to that of yearly rainfall in East China.The yearly rainy days decrease(regional averaged climate trend rate is -2.3 d/(10 a)),while yearly rainfall increases in East China except in Shandong Province,showing that the intensity of yearly mean daily precipitation increases.The trend variation of seasonal rainy days is comparatively consistent with that of seasonal rainfall,especially in autumn.The negative trend variations of rainfall and rainy days in spring and autumn cover most of East China,but the negative trend variation of rainy days cover larger areas with greater intensity compared with rainfall.The trend variations of rainfall in East China except in Shandong Province in summer and winter are positive,especially in the Yangtze River Delta Region in summer and in Yangtze-Huaihe Rivers in winter.The trend variations of rainy days in East China in summer and winter are positive,except in Shandong and Fujian provinces.The largest reduction of yearly rainy days covers the middle and eastern Shandong province and the northern Fujian province,and the trend of rainy days in the two areas reduces with 3—5 d/(10 a).The abrupt change of yearly rainy days in Shandong Peninsula appears in the late 1970s.After that time,the yearly rainy days reduce clearly.

Abstract:Based on the global 1°×1° and 3-hr atmospheric forcing data from 1948 to 2006 developed at Princeton University,the global land surface conditions in recent 50 years are produced by offline simulation with three different versions of NCAR Community Land Model(i.e.,CLM3.0,CLM3.5 and CLM4.0).Through comparing the simulation results,the differences in simulated soil temperature,soil moisture,latent heat,sensible heat and surface runoff among the three models and the main features are discussed.Results show:1)Differences in the simulated soil temperature and soil moisture are detected among three versions of CLM.Compared to CLM4.0,both CLM3.0 and CLM3.5 show warm bias in the simulated January and July soil temperatures at both shallow and deep layers in the mid-high latitudes of the Northern Hemisphere.The soil moisture simulated by CLM3.0 is too wet in the high latitudes of the Northern Hemisphere,but too dry in the mid-latitudes and the tropics.In contrast,no evident difference is found between CLM3.5 and CLM4.0 except that the soil moisture at shallow layer simulated by CLM3.5 is wetter than that of CLM4.0 in the high latitudes of the Northern Hemisphere.2)Evident differences in the simulated surface energy fluxes and hydrological variables are found among three versions of CLM.Compared to CLM4.0,the differences in the latent heat and sensible heat fluxes simulated by other two models mainly appear in the Tropics.CLM3.0 underestimates(overestimates) the latent heat(sensible heat) fluxes to some extent,while CLM3.5 basically gives larger latent heat flux(smaller sensible heat flux).In addition,the surface runoff simulated by CLM3.0 is evidently overestimated in the tropics,where it is improved but somewhat underestimated by CLM3.5.3)Differences among the model results vary with not only the season but also the selected region.On the whole,CLM3.0 produces larger bias in the simulation of the seasonal cycles of the soil moisture and canopy transpiration over the selected regions,and underestimates the soil moisture and the contribution of canopy transpiration to canopy evapo-transpiration seriously.Such results have been improved in both CLM3.5 and CLM4.0.In case of other land surface variables,CLM3.0 also exhibits some deficiencies,but CLM3.5 and CLM4.0 show better performance.

Abstract:The GCE(Goddard Cumulus Ensemble) model shows the interactions of clouds with each other,with their surroundings,with long wave radiative transfer processes,and with trace gas distributions.On one hand,the model can explain the growth,mature and decay processes(life cycle) of clouds by the cloud microphysical quantities,such as the hydrometeor change,etc.;on the other hand,based on the cloud microphysical processes,it can also be used to analyze rainfall process by introducing surface rainfall equation.Therefore,the precipitation processes actually reflect of cloud development processes.The cloud-resolving model discussed in this paper is the two-dimensional version of the Goddard Cumulus Ensemble Model.Based on the model,a heavy rainfall event in South China from 10 to 15 June 2008 is simulated.The characteristics of water vapor budgets and heat budgets are analyzed in the different phases of major surface rainfall period.Results show that the rainfall process is mainly repressed by local atmospheric moistening and water vapor convergence decreasing during the onset phase,while the local water vapor change,water vapor convergence,surface evaporation,and local hydrometeor change make positive contributions to the rainfall process during the mature phase,which leads to a maximum rain rate.In the decay phase,the major reason for the small rain rate is that the water vapor convergence is reduced significantly.In raining stratiform regions,the main water vapor source is water vapor convergence,while the main water vapor sink is local water vapor increasing.In convective regions,the main water vapor source is water vapor convergence and local atmospheric drying,while the main water vapor sink is local hydrometeor gain and transportation of hydrometeor from convective regions to raining stratiform regions.The local atmosphere heat change is small during the onset and decay phases,but during the mature phase,the local atmosphere cooling reaches the maximum.Time and domain means of the heat divergence and the latent heat release are the main reasons to cause the local atmospheric cooling.

Abstract:Based on the surface temperature observed by meteorological stations,this paper compares and analyzes the applicability of surface temperature from the ERA-Interim,NCEP/NCAR and NCEP/DOE reanalysis data over the Tibetan Plateau.Results show that the three reanalysis products reveal the basic characteristics,the seasonal and interannual variations of surface temperature over the Tibetan Plateau,but they are all much colder than the observations and underestimate the long-term trend of surface temperature.Comparatively,the applicability of surface temperature from the ERA-Interim is the best,the correlation in surface temperature between the ERA-Interim and the observations is the most remarkable,and the surface temperature from ERA-Interim can better represent the abnormal variation of surface temperature,which can be used as the substitution data in studying interannual variation of surface temperature over the Tibetan Plateau.But the applicability of surface temperature from NCEP/NCAR and NCEP/DOE reanalysis data are both low,and the applicable period and area should be investigated further.

Abstract:The advanced singular value decomposition(ASVD) method is the singular value decomposition(SVD) method of homogeneity adjustment for the grid and station network data.Based on the relationship between SVD and EOF(empirical orthogonal function),it gives a homogeneity adjustment method of the grid and station network data in SVD method,in such a way that the advanced singular value decomposition(ASVD) method is achieved.Using the ASVD and SVD methods,this paper analyzes the correlation coefficient matrix C. between temperature and precipitation of 160 stations over China in winter during 1951—2010.Results show that both the squarefitting rate and the accumulated squarefitting rate of the preceding four principal modes by ASVD method are obviously higher than those by SVD method.Comparing with SVD method,the relationship between the high value area in C squarefitting figure and the high absolute value area in the preceding two typical singular vector fields by using the ASVD method is more reasonable.It is verified that the homogeneity adjustment is necessary by using the SVD method,and there is more reasonable effect in practical analysis by using the ASVD method.

Abstract:Based on VDRAS velocity dealiasing technique,a Doppler velocity dealiasing algorithm is developed for the quality control of CINRAD Doppler radar velocity.The advantage of the algorithm is that it dealiases Doppler velocity at each grid point independently by using reference wind obtained from GRAPES RUC analysis,so it reduces the risk of producing incorrectly dealiased velocity in large areas.The algorithm consists of three steps:horizontal shear preserving,global dealiasing,and local dealiasing.Then,the algorithm was tested with radar data obtained from CINRAD during June 2009.The results showed that the algorithm was effective in dealiasing aliased velocities,removing noises and improving the quality of radar observations.It can serve as an operational algorithm for CINRAD Doppler velocity quality control.

Abstract:Using the Parsivel laser precipitation particle spectrometer,3 617 samples of raindrop size distribution of Meiyu front rainstorm were observed in Huainan and Nanjing during summer of 2009—2010.Gamma raindrop size distribution function is fitted by moment method,and the micro-structure of Meiyu front rainstorm is analyzed.Results show that the sizes of precipitation drops in rain belt are larger than those on the edge of rain belt.Contributions to total number concentration of raindrops with diameter of 0.25—1.0 mm are the maximum,but those to total rainfall intensity of raindrops with diameter of 1.0—2.0 mm are the maximum.The raindrop size distributions of Meiyu front rainstorm mostly show double peak type,without non-peak type.The peak diameter of raindrop size distribution of Meiyu front rainstorm first increases and then decreases with the rainfall intensity.However,the parameters of Gamma distribution,N₀,μ and λ always decrease with the rainfall intensity,and there is a good binomial function relationship between μ and λ.In addition,the Z-R relationship of Meiyu front rainstorm is Z=212R^1.38.

Abstract:Aerosol PM₁₀ of different sizes was collected the whole day in the northern suburb of Nanjing in winter 2009.This paper analyzes the distribution characteristics of water-soluble anions in PM₁₀ by using the ion chromatograph.Results show that the average total mass concentration of anions in PM₁₀ (PM_2.1) are 658.21 and 622.84 μg/m³ (337.86 and 319.97 μg/m³) in daytime and nighttime,respectively,and anions dominate in the fine particles.SO₄^2- are mainly water-soluble anions,and sea salt has little effect on the mass concentration of SO₄^2- in PM₁₀ and PM_2.1 in the northern suburb of Nanjing.The size distributions of SO₄^2-,Cl^- and F^- show bimodal nature,while those of NO₃^- and NO₂^- show single mode.Correlation coefficients between SO₄^2- and NO₃^-,F^- and NO₃^-,SO₄^2- and Cl^- are all greater than 0.8,which are significant,indicating that these anions are homologous.The average NO₃^-/SO₄^2- in daytime and nighttime are 0.0582 and 0.0484,respectively,indicating that the air pollution in northern suburb of Nanjing mainly comes from the stationary sources.Analysis of transformation of NO₃^- and SO₄^2- precursors shows that the average SOR and NOR during the sampling period are more than 10%.It is show that SO₄^2- in PM₁₀ is partially come from the second photochemical transformation of SO₂,rather than a single source of primary pollutants.

Abstract:The recombination rate coefficients of molecular ion with electron are several orders greater than those of the dominant atomic oxygen ion in ionosphere F region,so the plasma densities in ionosphere can be greatly depleted by modest amounts of H₂ gas released at ionospheric altitudes.Based on a 2-D dynamics model including the neutral gas diffusion equation and the ion chemical reaction equation,this paper simulates the processes of H₂ released at ionospheric altitudes and analyzes the changes of ionospheric electron and foF₂(critical frequency of F₂ layer) at different temporal and spatial release conditions.Results show that:1)500 mol H₂ gas released at the ionospheric altitude diffuses swiftly,where the electron density decreases nearly 4% after 30 s and the foF₂(critical frequency of F₂ layer) decreases about 1%;2)When the same amount of H₂ is released at different altitudes,the maximum relative change rate of electron density will not appear when H₂ is released nearby the peak altitude of F₂ layer(hmF₂);3)The more amount of H₂ is released,the larger disturbance of electron density is caused,but there is not a linear relation between them;4)The disturbance amplitude of electron density in daytime is larger than that in nighttime when the same amount of H₂ released at hmF₂.

Abstract:This paper summarizes the achievements of recent researches on seasonal,interannual and interdecadal variations of tropical cyclone activity over western North Pacific.It includes the effects of Madden-Julian Oscillation,ENSO(El Niño-Southern oscillation),the Indian Ocean warming or QBO(quasi-biennial oscillation) on the activity of tropical cyclone as well as the interdecadal variations of the relationship between the frequency of intense TCs and ENSO.Some prospects in this field and some further considerations are also proposed.