Abstract:A new parameterization for heterogeneous ice formation was used in a cloud model with bin-resolved microphysics to investigate the effect of aerosols,which act as cloud condensation nuclei and ice nuclei,on mixed phase convective cloud microphysics and precipitation.The results showed that, for the theoretically ideal simulated mixed phase convective cloud,the drop concentration increased significantly when aerosol particles transported in the boundary layer with decreased effective radius and graupel mass concentration due to suppressed graupel growth;whereas the number of ice crystals and graupel particles increased substantially when aerosols transported at mid-troposphere with altitude of 4—6 km,leading to more rapid Bergeron process and reinforced graupel mass concentration.The aerosols lofted at altitude of 2—4 km exerts relatively weaker effect on ice formation with slightly increased number concentration and decreased mass concentration of graupel due to smaller effective radius.Aerosol layers transported at both boundary layer and mid-troposphere resulted in diminished maximum liquid and ice phase rainfall rate with 28%—64%,4%—44% and 3%—46% reduction in accumulated rainfall when aerosols transported at altitudes of 0—2 km,2—4 km and 4—6 km,respectively.And under different pollutant conditions,the suppression effect of aerosol layers on precipitation and the difference in rainfall rates induced by aerosol layer transported at different altitudes were lessened with higher background aerosol concentration.

Abstract:This paper uses the mesoscale model(The Fifth-Generation NCAR/Penn State Mesoscale Model) to simulate three typical fog cases that occurred in 2009 in Shanxi Province,discusses the influence of the physical parameterization schemes on simulating the fog process and generates some recognition rules about fog prediction based on simulation data.This study will provide a theoretical basis for a fog numerical forecast system.Some results were drawn:1)The HIR scheme and Cloud scheme were the optimal boundary layer scheme and radiance scheme,respectively,in order to consider the overall effects of various parameterization schemes in the simulation of land surface temperature,atmospheric temperature,atmospheric relative moisture at 2 m level,wind speed at 10 m level,fog distribution,fog procedure and the fog top height;2)According to the results from the analysis of the three simulation experiments,the indices for fog prediction from the simulation data were that the liquid water content at 20 m height was more than 0.13 g/kg and less than 0.6 g/kg,there existed temperature inversion layers in the atmospheric layer at 20—1 500 m and that wind speed near earth surface was less than 4 m/s.

Abstract:The cloud microphysical properties of a stratiform cloud in Shanxi on 27 May 2010 were analyzed based on the airbrone DMT probes and Parsivel laser precipitation particle spectrometer.The results showed that the vertical and horizontal structure of clouds was uneven.The maximum concentration values sampled by CDP and CIP were 165.20 cm^-3 and 1.08 cm^-3 respectively.Average value of microphysical features of surface raindrops indicated that it was a typical stratiform cloud precipitation.Rainfall intensity is mostly decided by raindrop concentration.Temporal distribution of raindrop microphysical parameters was not even.The correlations between the rainfall intensity(I) and the radar reflectivity(Z),the rainwater content(W),the raindrop concentration(N),parameter N₀ and parameter λ were established.There was a very good correlation between I and Z and W,but N、parameter N₀ and parameter λ were poorly correlated to I.The surface raindrop size distributions were narrower and steeper than the upper raindrop size distributions.The precipitation was the coexistence of cold cloud and warm cloud precipitation.

Abstract:Based on the observations of road and bridge surface temperature and conventional meteorological data from Fenghuangguan reservoir automatic weather station along Wuying expressway from October 2009 to March 2010,the hourly variations of air temperature and bridge and road surface temperature were studied under different weather conditions including clear,overcast,foggy,rainy and snowy.The results showed that the bridge surface temperature was close to the air temperature and was usually 2 ℃ lower than the road surface temperature at night in winter.Moreover,surface freezing hours over the bridge is almost twice as long as that on the road.By using the validated underlying surface energy balance model,we calculated the energy budget elements of bridge surface at night under clear and overcast weather conditions respectively in winter,analyzed the difference in temperature changes between road and bridge surface and tried giving explanations for the phenomenon that bridge surface is apt to freeze compared with road surface.

Abstract:Cloud variables are important factors influencing atmospheric radiation process and precipitation,but it is still difficult to detect cloud variables by means of remote sensing.This paper detects and retrieves cloud variables by using a 35 GHz cloud radar.Variables of six types of cloud as cloud liquid-water content,ice-water content and equivalent diameter profiles are retrieved and analyzed.Result shows that:1)Different type of cloud has different variable distribution;2)The retrieved variables are acceptable for cases of non-precipitation cloud with echo intensity below -15 dBz;3)Linear depolarization ratio is a good index for discriminating super-cooled water droplets and ice crystals,and is hence helpful to understand macro- and micro-feathers of cloud.

Abstract:Biweight estimation was used for observation incremental(difference between observation and background simulated by RRTOV9 based on the NCEP Final Analysis data) during the quality control procedure.The quality control scheme was divided into two steps:A range check and identification of outliers.The purpose was to remove the outliers influenced by emissivity of surface and cloud.The preliminary analysis result showed that the deviation got close to unbiased normal distribution;the standard deviation of observation incremental significantly reduced after the quality control procedure.The quality of FY-3 satellite microwave emissivity temperature detector data improved obviously,which laid a solid foundation for the application of MWTS bright temperature data in the numerical prediction data assimilation system.

Abstract:Effects of transient waves' dynamic forcing on the northward jump of jet and the westward movement of jet center from early summer to midsummer are studied by using NCEP/NCAR daily reanalysis data.The result shows that the transient waves' dynamic forcing is favorable to the northward jump of the jet,but not favorable to the westward movement of the jet center.Then the relationship between the occurrence time of East Asian Subtropical Westerly Jet variations from early summer to midsummer and anomalies of transient waves is further studied.The analysis revealed that the dynamic forcing of the transient anomalies has a positive feedback effect on the occurrence time of the jet's northward jump and a negative feedback effect on the occurrence time of the jet center's westward movement.So the transient waves' dynamic forcing has important influence on the variations and occurrence time of the East Asian Subtropical Westerly Jet from early summer to midsummer but exerts significantly different effects on the Jet's northward jump and its center's westward movement.

Abstract:The NCEP/NCAR reanalysis data are mostly used to investigate the variability of South Asian high(SAH) and its relation to sea surface temperature(SST) in previous studies,but the results from these studies have one-sidedness.Thus,this paper compares the summer SAH intensity variation and its relation to SSTs using five reanalysis data (ERA-40,ERA-Interim,NCEP/NCAR,NCEP-DOE and JRA-25) and three simulation results from which the atmospheric general circulation model NCAR CAM5.1 is driven by the observed monthly global,tropical Indian Ocean and tropical Atlantic Ocean SSTs during 1978—2008,respectively.Comparisons in SAH intensity among these reanalyses show that there is a very distinct difference in SAH intensity variation between the two reanalyses(NCEP/NCAR and NCEP-DOE) and the other three reanalyses(ERA-40,ERA-Interim and JRA-25) during the period of the late 1970s to the early 1990s,indicating that the abrupt increase of SAH intensity in NCEP/NCAR and NCEP-DOE reanalyses maybe not true during this period.The possible false data lead to a distinct difference in relation of SAH intensity to SST anomaly between the former two reanalyses and the latter three.Results from the three reanalyses(ERA-40,ERA-Interim and JRA-25) and three experiments show that summer SAH intensity anomaly is closely associated with the tropical Indian Ocean SST anomaly in previous winter,previous spring and contemporaneous summer after 1970s,indicating that the tropical Indian Ocean is a key area to affect the summer SAH intensity.When the tropical Indian Ocean is warmer than the normal,the tropospheric temperature will be warmer in tropics,in such a way that SAH intensity will be enhanced,SAH area enlarged,and SAH location extended southward,eastward and westward,and vice visa.

Abstract:North Pacific subtropical high(H_P) in monthly and seasonal mean sea level pressure fields is a permanent atmosphere activity center in the Northern Hemisphere,which is closely related to the atmospheric circulation and regional climate anomalies.The traits of H_P are briefly described by the area and intensity indices of a closed pressure system,and the indices are used to analyze the climate and abnormal characteristics of H_P,as well as the relationship between H_P and sea surface temperature anomalies in the eastern tropical Pacific.Because H_P significantly weakens in winter,when calculating S and P indices of H_P,it is difficult to find a typical isobar,which can clearly describe the circulation features throughout the analysis period.To solve this problem,a calculation scheme is proposed.Firstly,a higher f₀ is choosed and used to calculate the circulation indices (S and P) in most years.Then a lower f₀ is selected to calculate the circulation indices (Ŝ and P) in a few extreme weak years of H_P.Finally,a simple linear regression equation is used to correct the results from Ŝ and P indices to S and P indices and the complete sequences of the S and P indices are obtained.The application results show that the obtained complete sequence of H_P is appropriate.

Abstract:Based on NCEP/NCAR reanalysis data and rainfall data from 753 weather stations in China,the causes for droughts in the eastern region of the southwest part of China(ESWC) are discussed in this paper.The results indicate that both interdecadal and interannual changes are obvious in the precipitation in ESWC.The main characteristic of interdecadal change was that a sudden shift from wetness to dryness appeared around the late 1980s in ESWC;the interannual variations of precipitation are highly related to the SSTA over the regions from the eastern Indian Ocean(around Sumatra) and western Pacific(EIWP) to eastern Pacific(EP).By inducing abnormal atmospheric heating,the positive and negative abnormal patterns in SST over the EIWP and EP induces cyclonic circulations around South China Sea and Bay of Bengal,together with enhanced Hardly Cell.In this case,the studied area is then controlled by both northerly wind and enhanced downward vertical motion while the water vapor transport from the Bay of Bengal is reduced.All the above reasons lead to droughts in the studied region.The above observational results are further confirmed by a series of numerical model simulations using NCAR CAM3.0(Community Atmosphere Model 3.0).

Abstract:Based on ERAinterim and NCEP-DOE reanalysis data,this paper studies the spatial-temporal relationship between the boreal wintertime Arctic Oscillation(AO) and the surface air temperature(SAT) over the south Yangtze River regions.Results show that:1)The simultaneous correlation coefficient is the largest between AO index at 30 hPa and SAT over the south Yangtze River regions in February,in association with the fact that the standard deviations of both the AO index at 30 hPa and the SAT over the south Yangtze River regions achieve their maximum in February.2)When the positive AO event is strengthened at 30 hPa,there are obvious positive geopotential height anomalies in troposphere over the Baikal region,which is favorable for the anomalous southward and downward wind over East Asia.Accordingly,Siberian high tends to extend southward,which contributes to the occurrence of negative SAT anomalies over the south Yangtze River regions through the southward intrusion of north cold air,and vice versa.

Abstract:Based on the ERA40 reanalysis data,this paper explores the basic features of the multi-spatial-modes reflecting anomalous East Asian summer monsoon(EASM) activity and their relevant atmospheric general circulation anomalies by using statistical methods,such as the correlation,composite and EOF analysis.Results suggest that:1)There are three typical spatial modes of EASM with significant differences among them.The first mode represents an out-of-phase variation of summer wind between the coastal area in eastern China as well as its adjacent ocean and the region to the west of the coastal area,which reflects the westward/eastward movement of EASM.And the second mode shows consistent variation of summer wind over the extensive areas,originating from South China,across the mid-lower reaches of the Yangtze River,Shangdong Peninsula,the Bay of Bohai Sea,to northeast China and the Korean Peninsula,which represents the overall variation of EASM intensity.However,the third mode suggests an out-of-phase variation of summer wind between south China and the coastal area in East China,the Korean Peninsula,and northeast Asia,reflecting the northward/southward movement of EASM.2)The atmospheric general circulation anomalies related to the three spatial modes of EASM exhibit significant differences.The first mode bears negative correlations with SLP over South Asia and the Sea of Okhotsk,and positive correlations with SLP near the Arctic,Lake Baikal and the ocean east to Japan.The correlation between the first mode and summer 500 hPa geopotential height is featured by a "+-+" wave-train-like pattern from the polar region,across the Sea of Okhotsk,to the ocean east to Japan.The second mode shows very similar correlation patterns with both SLP and 500 hPa geopotential height,which represent an out-of-phase variation of SLP and 500 hPa geopotential height between northeast China,the Korean Peninsula,the Sea of Japan and the Philippines as well as the Sea of Okhotsk,forming a "+-+" wave-train from the low latitudes to the high latitudes.The correlation patterns of the third mode with SLP and 500 hPa geopotential height are both alternated with positive and negative over the ocean around the Philippine,Japan as well as the ocean east to Japan,the Lake of Baikal,and northern Asia.

Abstract:Based on the UK reanalysis data,this paper studies and compares the large-scale environmental characteristics of Rapid Intensifying TC (RITC) and Rapid Filling TC (RITC) at 24 h before landing in South China by using the composite analysis method.Results show that the low level inflow and upper level outflow of RITC are significantly stronger than those of RFTC,the intensity difference in high level outflow between RITC and RFTC is more significant than that in low level inflow,and the secondary circulation radial range of RITC is larger than that of RFTC.In terms of the vertical stretching height of outflow,the average outflow of RITC is concentrated on levels above 500 hPa,while the average outflow of RFTC is dispersedly spread down to 850 hPa.The analysis of high level flow field indicates that RITC has stronger high level outflow except in the northwest quadrant,while RFTC only has stronger high level outflow in the northeast quadrant.Correspondingly,there are obvious differences in the range and intensity of upper level divergence between RITC and RFTC,in which the upper level divergence of RITC is stronger than that of RFTC.The abundant southwest monsoon water vapor transportation can promote TC intensifying rapidly before landing in South China,and the convective activity of RITC is obviously stronger than that of RFTC.The tropospheric vertical wind shear of RITC is weaker than that of RFTC,which is beneficial to the intensifying of RITC.

Abstract:Based on the NCEP/NCAR TRMM,FNL and reanalysis data,the mesoscale numerical model WRFV3.2 is used to simulate the Meiyu front rainstorm over the Huaihe River basin during 23—24 June 2011.A series of sensitive experiments are carried out to research the effect of the terrain of Dabie mountains on the rainstorm.Results show as follows:1)The terrain of Dabie mountains can force the southwest warm-wet flow to uplift and flow around the mountains,which produces perturbation and is conducive to release unstable energy,condense water vapor,and form rain band.2)Due to the terrain of Dabie mountains,the warm-wet flow meets the north air stream,the troughs exhibit zonal distribution,and the rain band is consistent with the flow convergence band.3)If the terrain of Dabie mountains increases,the convection would be more severe.If the terrain of Dabie mountains decreases or disappeares,the rainfall center at Huaihe River basin would shift eastward apparently.Therefore,the terrain of Dabie mountains can weaken the eastward movement of synoptic system,and concentrate the heavy rainfall.

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