Abstract:Using cloud top physical properties of geostationary satellite, ground rainfall observation, and MM5 numerical simulation，the authors analyse the evolvement and structure of typical stratiform cloud. It shows that the relationship between cloud top physical properties and rainfall intensity at single station is not simply statistic. If rainfall is large, a good positive relationship between rainfall per hour and cloud top height, effective particle radius, and a good negative relationship between rainfall per hour and cloud top temperature are found. Whereas, higher cloud top height, lower cloud top temperature, and larger effective particle radius cannot always guarantee the larger rainfall. The mechanism of this phenomenon has been explained by numerical simulation.

Abstract:The Copula theory was used to construct the joint distribution of precipitation in the flood season, the dry season，and the whole year between the water source area and the water receiving areas in the middle route of the SouthtoNorth Water Transfer Project. The effect of climate change on the synchronous-asynchronous encounter probability of rich-poor precipitation was analyzed based on the General Circulation Models (GCMs) outputs in the IPCC Fourth Assessment Report(IPCC AR4). The results show that on the flood season scale, the synchronous frequency of both rich and poor exhibits increasing tendency in the Han-Tang(Hanjiang Water Source Area-Tangbaihe Water Receiving Area) encounter and Han-Hai(Hanjiang Water Source Area-Hai River Water Receiving Area) encounter, and the values are 3.34%~16.48% and 2.56%-8.21%, respectively, under different emission scenarios; while the synchronous frequency of both rich and poor exhibits decreasing tendency in Han-Huang(Hanjiang Water Source Area-Yellow River Water Receiving Area) encounter, the value is in the range of -1.97%-9.57% under different emission scenarios. On the dry season scale, the synchronous frequency of both rich and poor in the Han-Tang encounter and Han-Hai encounter decreases about -0.21%-9.42% and 0.99%-5.54%, respectively，while that in Han-Huang encounter increases about 1.79%-13.28%. On the annual scale, the synchronous frequency of both rich and poor exhibits decreasing tendency in all the three encounters, and the values for the Han-Tang, Han-Huang, and Han-Hai encounters decrease about -2.88%-10.97%, -1.28%-5.05%, and -2.33%-7.01%, respectively.

Abstract:Using groundbased Aerosol Optical Depth (AOD) data at Tazhong, Taklimakan desert area, four sets of satellite aerosol data, from the Multiangle Imaging Spectrometer (MISR), the Moderate Resolution Imaging Spectrometer (MODIS), and the Ozone Monitoring Instrument (OMI) from 2007 to 2008 were validated. The results show that satellite aerosol retrievals are significantly correlated with the groundbased ones. The correlation coefficient for MODIS/AOD is the largest (0.91), followed by OMI/AOD (0.87), MISR/AOD (0.84), and OMI/UVAI (0.51). MISR/AOD rootmeansquare error (0.14) and the average deviation (-0.06) are the lowest in the four products. MISR/AOD and MODIS/AOD is relatively less than the groundbased AOD, however, OMI/AOD and OMI/UVAI exceeds the groundbased ones. Under the same conditions (groundbased AOD is limited to less than 2.0), the rootmeansquare error and the standard deviation of MISR is the lowest. Seasonal variation of aerosol is captured by satellite data. AOD is relatively larger in spring and summer and is relatively lower in autumn and winter. The result of ngstrm wavelength exponent shows that the spring has the minimum(0.11), followed by summer and autumn, and winter has the maximum(0.61), which shows that the aerosol particle is larger in spring and summer while it is smaller in autumn and winter. Besides, Taklimakan desert area belongs to the sand source where aerosol type is single. In summary, the annual variability tendency of AOD from 2000 to 2010 is not obvious. The result of the retrieval shows that there is the maximal aerosol content in 2003 during the decade and the annual average is up to 0.32, while there is the minimal aerosol content in 2005 and the annual average is 0.28.

Abstract:The strength and structure of broadband heating rate directly drives the global atmospheric circulations and is largely determined by cloud threedimensional (3D) structures. Heating rate profiles and fluxes of three cloud fields resolved by Cloud Resolving Models (CRM) are simulated by a broadband 3D Monte Carlo radiative transfer model, which gives a quantitative and statistical estimate about the effects of cloud 3D structures on radiation in high resolution by comparing with Independent Pixel/Column Approximation (IPA/ICA). Two parameters are defined to describe the vertical distribution and strength simultaneously. The results show that the impacts of cloud 3D structures on radiation are very significant under high resolution conditions and different kinds of cloud fields have various characteristics. A direction of the revising on current heating rate calculation scheme in existing atmospheric models due to cloud 3D structures is raised.

Abstract:Monthly data from climate change simulations based on the 15 coupled climate system models in IPCC SRES (Special Report on Emissions Scenarios) A2, A1B, and B1 are analyzed for potential future changes in summer precipitation characteristics and its associated atmospheric circulation, and the uncertainties of these results from models are also investigated. The results demonstrate that the projected summer precipitation in China shows distinctly regional characteristics. The summer precipitation in the eastern part of China and the Tibetan Plateau are projected to significantly increase in the 21st century. These increasing linear trends and the consistency of the models are also intensified with the increase of air temperature, which indicates that the projections become much more believable in these regions. However, persistent decrease of summer precipitation is projected in the southern part of Xinjiang region, and most of models show decreasing precipitation in the earlier period of the 21st century and then increasing in Southwest China. No obvious changes are projected in the other parts of China, but with larger uncertainties. The high confidence level of the multiple models ensemble results in IPCC three scenarios implies that the projected summer precipitation changes are much more believable in China, with the larger projection in A2, smaller in B1, and middle in A1B.Most of the models demonstrate that the East Asian summer monsoon will significantly intensify under global warming, which induces more water vapor transport from the South China Sea and the tropical oceans. Thus, more water vapor content will be gathered that provides a benefit background for the increasing summer precipitation in the eastern part of China. Meanwhile, the western Pacific subtropical high is also projected to significantly intensify and the impacts on the summer precipitation in the eastern part of China also obviously increase. These results from the analysis of the atmospheric circulation and the corresponding uncertainties of the models further increase the confidence level of the projected summer precipitation change in China.

Abstract:In order to develop detail survey and integrative evaluation of wind energy resource, the consistency corrections, objective homogeneity tests (such as SNHT, Potter, and CUSUM), and homogeneity adjustment of yearly mean wind speed series were carried out during 1970-2009 from four meteorological stations which represent wind areas according to their historical metadata features. During the period of nonautomatic wind recorder, how to build the 10min interval yearly maximum wind velocity series was also explored elementarily based on observed 2min interval wind data. The results show as follows: 1) The yearly mean wind speed time series were inhomogeneous，which was caused by the change of their surroundings or other uncertain factors at Burqin, Naomaohu, and Hongliuhe stations. From the values of the SNHT homogeneity adjustment and the buildings surrounding the stations, the most largely environment influence occurred at Burqin station where the time series broke off three times and the mean accumulated adjustment value reaches 09 m·s-1 or so. There are two discontinuous points at Naomaohu station, one of which concerns location moving, and that of adjustment value is 0.1－0.2 m·s-1. There exists one discontinuous point at Hongliuhe station, which also concerns location moving like Naomaohu station, and that of adjustment value is 0.1－0.2 m·s-1. 2) On transforming the yearly maximum wind velocity of 10min interval from that of observed 2min interval under the control of some critical wind speed, it is acceptable to adopt the experiential formula fitting to the northwestern part of China at Shisanjianfang station, while it is better to employ their mean portion correlation at the other three stations.

Abstract:Over the equatorial centraleastern Pacific，there is an anomalous seawater warming event that is significantly different from the typical El Nino event. In 1993, for example, an anomalous warming event occurred in March with its peak in May, then it decayed rapidly. This warming event is referred to abortion of an El Nino event. By comparing the event in 1993 with the typical El Nino event, the authors explore the feature and the cause of the abortion of this event. It is found that the event in 1993 is a local airsea coupling phenomenon in the tropical centraleastern Pacific. Due to the relatively strong El Nino event during 1991-1992, the western Pacific warm pool was anomalously cold during 1992-1993, and the thermal condition was not suitable for the occurrence of an El Nino event in 1993. In this case, the eastward extension of the equatorial westerly anomaly in spring from the western Pacific to the central Pacific satisfied the dynamical condition for the occurrence of an El Nino event, but the basin scale Bjerknestype positive feedback failed to work due to the cold warm pool. As a result, the seawater warming in the equatorial centraleastern Pacific lasted for a short period, then it decayed rapidly, causing the abortion of an El Nino event.

Abstract:Using the sizesegregated measurements of atmospheric aerosols collected in Beijing and Qingdao in China and Fukuoka in Japan during the spring of 2002, the size distributions of the mass of atmospheric aerosols with aerodynamic diameter (Dp) ≤ 11 μm (PM11) along dust transport routes are investigated. The size distribution of these aerosols in mass concentration during nondust periods exhibits a bimodal pattern, ie., a fine modes with Dp< 2.1 μm and a coarse mode between 2.1 μm and 11 μm. On the other hand, the size distribution of these aerosols in mass concentration during dust periods attempts to exhibit a unimodal pattern in the coarse particle size range. The coarse mode diameter decreases with the distance from the dust source zone to the west and east coast of the Yellow Sea during the heavy dust periods. It is not case in regular dust periods. The sizedependent dry deposition fluxes of the aerosols over the Yellow Sea in springtime are estimated using an improved Williams' model. The dry deposition fluxes increase with the increasing size in the coarse particle size range during the nondust and dust periods. It appears that no evident variations occurred in the fine mode. The estimated PM11 fluxes over the Yellow Sea during the dust and nondust periods range from 31.70 to 58.59 mg·m-2·d-1 and ranged from 8.33 to 15.94 mg·m-2·d-1, respectively. Although the dry deposition fluxes of the coarse particles increase evidently during dust periods, the relative contributions of the coarse particles to that of PM11 do not change significantly regardless of the occurrence of and absence of dust events. The authors find that coarse particles are the main contributor to the PM11 dry deposition in springtime over the Yellow Sea, the percentage reaches over 94.2%.

Abstract:A twodimensional two-layer barotropic quasi-equilibrium ocean model under the wind forcing considering Rayleigh dissipation is built, and the analytic solution is given under the situation of midlatitude largescale wind field forcing. The results show that, under the forcing of the westerly jet stream, in the upper flow field of the east to west coast of the ideal ocean, there is a stronger east flow in the westerly forcing, and there is a west branch near the βchannel wall; while near the west coast, there are streams with cyclonic curvature and anticyclonic curvature on both sides of eastward flow. The lower flow field, whose strength is approximately the same with the upper flow field, but the direction of the flow is generally opposite. The distribution form of flow anomalies forced by the ideal westerly jet anomalies is similar to the results above. Compared to the upper flow field anomalies in the North Pacific forced by the actual wind anomalies, there are similarities between the actual situation and the results of the upper ocean in the article. Finally, the solution of the ocean model runs to the forcing particular solution of wind field here.

Abstract:Based on the monthly mean reanalysis data of geopotential height at 500 hPa from the NCEP/NCAR during 1950-2007, the characteristics of the anomaly height fields at 500 hPa from December to February and from June to August in the Southern Hemisphere corresponding to the three rain patterns in China during summer were discussed. The multivariate analysis of variance was used to find the key area A of zephyr index corresponding to the rain patterns, and the relationship between zephyr index in key area A and the precipitation during summer in China had been investigated. It was also analyzed to find an affiliation which the abnormal zephyr in the Southern Hemisphere from December to February would affect the zephyr in the Northern Hemisphere in summer, thereby impacted the distribution of rain patterns in China. According to the study, the anomaly height fields corresponding to the rain patterns exhibited different distributions, and the significant discrepancy area was in (35°N-50°N, 35°E80°E). The key area A from December to February located in 22.5°W-2.5°W, and from June to August was in 10°E-55°E. The precipitation in China in summer was linked to the fluctuation of zephyr index in the key area A. The abnormality of zephyr in the Southern Hemisphere in winter could forecast the variation of zephyr in the key area in the Northern Hemisphere in summer. The significant anticorrelation area of zephyr index in the Southern Hemisphere from December to February and the height field in the Northern Hemisphere in summer distributed in Lake Baikal. The latitudinal transmit of atmospheric circulation between the Southern and the Northern Hemispheres was one of the trace of the interaction between zephyr in the Southern Hemisphere and that in the Northern Hemisphere possibly. The abnormal zephyr in the Southern Hemisphere in winter would affect the intensity of trough in Lake Baikal, with which the zephyr in the key area was abnormal in the Northern Hemisphere, thereby affecting the distribution of rain pattern in China over summer.

Abstract:The authors study the seasonal and interannual variations of sunshine duration, total cloud cover amount, and low cloud cover amount in the past 48 years for both the urban and suburban areas in Beijing by utilizing the observational data from 1961 to 2008 at 12 stations in the urban and suburban areas and by employing the methods of trend analysis and accumulation bias, and also discuss the effects of urbanization on the variations of sunshine duration and cloud cover amount.For the urban area, the results have shown a decreasing trend for the total cloud cover amount, but an increasing trend for the sunshine duration. For the suburban area, the results have shown an increasing trend for the total and low cloud cover amount, but a decreasing trend for the sunshine duration. In decadal scale for these variations, the total cloud cover amount for the urban area has decreased since the beginning of the 1980s, especially in the 1990s.After 2000, the total cloud cover amount for the urban area has reversed and increased significantly, however, the low cloud cover amount for both urban and suburban areas has shown a decreasing trend with fluctuation from the 1960s to the 1980s, but an increasing trend with fluctuation from the 1990s to the 2000s. The sunshine duration for both urban and suburban areas has shown an increasing trend from the 1960s to the 1980s, but a decreasing trend from the 1990s to the 2000s. The low cloud cover amount and the sunshine duration show a negative relationship. This is closely related to the effects of urbanization on regional climate.

Abstract:Based on the daily observation data during 1951-2008, the change of extreme weather events in Beijing are analyzed. Results show that: (1) The annual mean temperature, minimum temperature, and mist events show increasing trends of 0.39℃·(10 a) -1, 1.0 ℃·(10 a)-1, and 12.4 d·(10 a)-1 respectively. The maximum 24 h rainfall shows a decreasing trend of -10.8 mm·(10 a)-1, rain days, humidity, gale, and thunder storm decrease at different extent [-1.90 d·(10 a)-1,-1.17% (10 a)-1,-2.64 d·(10 a)-1,and -1.24 d·(10 a)-1], sand and dust events show a decreasing trend of -9.39 d·(10 a)-1. The maximum temperature, the maximum rain intensity(60 min), and rainstorm, frost, fog, high temperature events have little change. (2) Rainstorm, high temperature, the maximum temperature, and sand and dust events have no remarkable periodicity. Thunder storm, frost, the minimum temperature, the maximum 24 h rainfall, and mist events have periodical variation, their main periods are 6 a, 7 a, 16 a, 12 a, and 12 a,respectively. (3) Urbanization has an effect on the warming records in Beijing. Extreme weather events may be influenced by certain weather systems, with less correlation with city development.