Abstract:The LPJDGVM (LundPotsdamJena Dynamic Global Vegetation Model), which is a processbased model, is used to simulate the vegetation distribution and estimate the interannual variation of net primary production (NPP), heterotrophic respiration (Rh) and net ecosystem production (NEP)in China from 1981 to 1998. It is shown that there are six main plant functional types (PFTs) besides the desert,that is tropical broadleaved evergreen tree, temperate broadleaved evergreen tree, temperate broadleaved summergreen tree, boreal needleleaved evergreen tree, boreal needleleaved summergreen tree and C3 perennial grass. In China, the total NPP varies between 2.91 Gt·a-1(C) (1982) and 3.37 Gt·a-1(C) (1990), increases by 0.025 Gt (C) average per year and has an increasing trend of 0.96%. The total Rh varies between 2.59 Gt·a-1(C) (1986) and 319 Gt·a-1(C)(1998), grows by 1.05% per year and by 0.025 Gt(C) per year. The linear trend of NPP and Rh for C3 perennial grass is more remarkable than those for other PFTs. The simulation of NEP is reasonable when the fire is brought in the model. Annual total NEP varies between -0.06 Gt·a-1(C)(1998)and 0.34 Gt·a-1(C)(1992). It is demonstrated that the terrestrial ecosystem is carbon sink in China. The above results are similar to those simulated by other models.
Abstract:With the global climate change and the aridification in northern China, more and more studies have focused on the landatmosphere interactions in arid/semiarid areas. The goal of this presentation is to evaluate land surface models BATS, LSM, and CoLM in semiarid areas using the Coordinated Enhanced Observing Period (CEOP) data, with an emphasis on comparison of the performance of the three models in semiarid regions. The results show that all of the three models can simulate the diurnal and seasonal cycle of the fluxes between land surface and atmosphere in this region, but the performance varies largely among them. For the simulations of the ground surface temperature and ground emitted longwave radiation, BATS is better than LSM and CoLM. As to sensible and latent heat flux, CoLM and LSM are better, and CoLM is the best. The performance of the three models varies with seasons, with summer better than winter. It is significant that all three models can not simulate the latent heat flux well in winter, which indicates that the current LSMs should pay more attention to improve the simulating performance in semiarid areas in winter.
Abstract:Spatial distributions of vertical eddy diffusivity (Kz)，dry deposition velocity(V), and concentrations of O3and NOxover East Asia are simulated using the surfacelayer similarity and the whole PBL similarity in the turbulence parameterization, after coupling the widely applied LLA (Lurmann Lloyd Atkinson) chemical mechanism in East Asia into the Regional Air Quality Eulerian Model (RAQM) and considering the temporal heterogeneity in rainwater in longterm modeling studies of air pollutants over a large domain. Simulations indicate that Kzvalues are significantly underestimated by the whole PBL similarity, with above 20% at 50 m and around 70% at 750 m high above the ground, respectively. Dry deposition velocities of O3 and NOx are underestimated at least 10% in the sea area on the east and south of Japan, while in the sea area on the east and west of Korea Peninsula the values are generally higher. Large deviations in Kzand dry deposition velocity between the two schemes lead to different results of O3 and NOx. Underestimation oKz values leads to large changes in NOx concentrations, with a maximum increase of 30% at 50 m high above the ground and approximately 5%-20% increases in mean NOxlevels in the whole PBL except the sea area on the northeast of Taiwan. However, the concentrations of O3 are dependent significantly on the dry deposition process. The surfacelayer similarity and the whole PBL similarity well depict the timing of O3and NOx peaks while the surfacelayer similarity follows observations in amplitude better than the whole PBL similarity. The surfacelayer similarity is a better choice than the whole PBL similarity and the first vertical model layer should be set within the surface constant flux layer even in longterm regional simulations of air pollutants.
Abstract:The authors proposed a quasidynamic chamber method for measurement of NH3 emission from a soilplant system. This method showed that the recovery rate is 89.0％± 4.9% for measurement of NH3 volatilization, which is in agreement with the recovery rate of a windtunnel method. It can also yield results consistent with those measured by a limitedly ventilated close chamber method. There is a significant exponential correlation between diurnal NH3 emissions and temperature (r<0.05). The optimum time for an intermittent measurement using the quasidynamic chamber method was proposed at around 0900LST or 1600LST. The NH3emission caused by an N fertilization event could be best captured after 1－2 weeks using the quasidynamic chamber method. Using the quasidynamic chamber method, the NH3N losses from the applied urea into a wheat field in Shanxi Province during the wheat jointing stage were observed at 3％－5%.
Abstract:Data assimilation has been successfully applied in atmospheric, oceanic, and land surface models. However, the fourdimensional variational (4DVar) assimilation system demands great computational costs. The authors introduced a new HistoricalSampleProjection data assimilation scheme(HSP4DVar), and accomplished the HSP4DVar land surface data assimilation system based on the Common Land Model(CoLM). As a scheme which requires no adjoint models, HSP4DVar can be directly solved and easily realized, therefore avoids high computational costs. The land surface data assimilation system was used to assimilate the soil moisture data for 56 months. After assimilation, the overall rootmeansquare error was significantly reduced with improved simulations, especially the simulation for the top 1000 mm layer.
Abstract:A radiation fog on 20 November 2006 in Beijing area is simulated and diagnosed with MM5 nonhydrostatic model. By contrasting the image of the NOAA satellite with the observation data of radiometer, the results showed that the MM5 could well simulate this fog event, especially in simulating the fog area, the height and the duration of the fog. Furthermore, aiming at explicit moisture scheme, longwave radiation, shortwave radiation, and vertical resolution, four sensitivity experiments were performed. The results show that longwave radiative cooling is an important factor of the formation of the fog, while the shortwave radiative warming is an important factor of the fog dispersal. In addition, the results were obviously improved by increasing the vertical resolution or using more complicated explicit cloud scheme.
Abstract:Aerosol samples were collected continuously by a step sampler with a 2hour time step during 30 September－6 October 2001 at meteorological tower at the height of 8 m in Beijing. Chemical composition of aerosol samples was analyzed by using PIXE method. The results showed that the diurnal variations of element concentrations were remarkable, and higher pollutant concentrations often occurred in the morning and midnight. Enrichment factors of S, Pb, Cl, Zn in atmospheric aerosol in Beijing which had a close relationship with the human activities were very high. Factor analysis for element concentrations further indicated that main sources affecting atmospheric aerosol concentrations in Beijing were soil matters, coal combustion, industry dust and vehicle emission.
Abstract:Using the datasets from 30 observational stations over mainland China, the authors studied the changes in annual and seasonal amounts of surface solar radiation from 1961 to 2003 and the spatial characteristics. Cause of the changes was discussed. The results indicated that surface solar radiation in mainland China decreased by approximately 11% from the early 1960s to the late 1980s in general, but increased slightly during 1990-2003. Nevertheless, the mean value of surface solar radiation over 1990-2003 was 8.2% lower than that over 1961-1965. Significant decrease occurred in the period from March to August, accounting for 55%-85% of the annual reduction. Analysis of the datasets for each station suggested that the trend in changes of surface solar radiation with time could be roughly identified as four groups with the characteristics of decreasing continuously (6 out of 30 stations) or leveling off (7 out of 30 stations) over the period from 1961 to 2003, and decreasing significantly from the early 1960s to the mid 1980s and leveling off thereafter (12 out of 30 stations) or increasing gradually thereafter (5 out of 30 stations). The four groups have no significant regional feature in spatial distribution. A main cause of the reduction in solar radiation is the decreasing sunshine duration. Approximately 72% of the variability in the solar radiation can be expressed by the sunshine duration which is positively correlated with wind speed.
Abstract:A data set of precipitation, mean temperature and other climate variables at 94 stations of Xinjiang Uygur Autonomous Region is firstly used to analyze climate changes in Xinjiang Uygur Autonomous Region. The widely accepted procedures for creating regional averaged climatic time series and calculating linear trend and cumulative anomaly have been used. Analyses and discussion have been made for annual precipitation, mean temperature, wind speed, low cloud cover, total cloud cover, specific humidity, pan evaporation, and diurnal temperature range, and the seasonal analysis only includes precipitation and mean temperature. Solar radiation from a limited number of stations was available to evaluate the relationship between solar radiation and sunshine duration, total cloud cover, low cloud cover, and pan evaporation. The analyses show that the increasing rate of annual precipitation in Xinjiang as a whole was about 8.5 mm·(10 a)-1, and time series of annual precipitation turned from dry to wet in 1987. It is consistent with some earlier studies. Furthermore, the seasonal analyses demonstrate that precipitation began to transfer in the winter of 1986 actually. Except the Turpan basin, precipitation is increasing all over Xinjiang. Mean temperature is warming throughout Xinjiang. The regional mean temperature has a significant increasing trend, and the rate of warming in winter is larger than that in the other seasons. The authors also find that pan evaporation decreased in Xinjiang from 1960 to 2005, and the decrease is statistically significant. The changing rate is -26.5 mm·(10 a)-1, which is smaller than the average values in the whole China. There were not significant longterm changes of annual sunshine duration, total cloud cover. Longterm changes in regional averaged specific humidity and low cloud cover have a significant increasing trend, and they also have the similar pattern to decadal or annual change of precipitation. The increasing changes of them perhaps lead to the increasing of precipitation. It is worth to study further. The authors also tentatively analyzed the possible causes for the observed change. However, it may be premature to give a definite conclusion at this moment.
Abstract:Xiaoyangshan Isle, approximately 30 km southeast coast of Shanghai, is surrounded by East China sea. The study of atmospheric aerosol optical characteristics over this region is important for understanding the effect on environment and climate in East Coast of China and its offing. The observation and analysis of the aerosol optical depth (AOD) data for isle near the coast are few in China untill now. The authors used the observed data from 2006 to 2007 to analyze the characteristics of AOD, such as its seasonal variation, the correlation of AOD with surface winds, relative humidity and visibility, etc, and the spectral distributions of AOD are given. The results show that the AOD over Xiaoyangshan isle is the largest in spring, less in winter, and the smallest in autumn. The aerosol is composed of larger particles in low visibility and more larger particles appear in west wind. The AOD and relative humidity have a positive correlation.
Abstract:The impact of urban growth on the temperature jump and the heat island in Xian region, China, has been investigated using temperature data measured at 14 observation stations from 1966 to 2005. The urban impact was stood for by the difference of average temperature between urban and suburban areas. The conclusions can be drawn as follows: 1) In summer and winter, the temperature temporal variation characteristics over suburbs,plain area,hill,are conformance with the regional average temperature,and represents the large scale climate characteristics,but small scale cimate variation characteristics are represented in urban region which is different with the areas mentioned above. But, there are different phases in the longterm change of the urban and regional average temperature, which has smallscale climate feature. 2) Xian region had a temperature increasing jump mainly with natural increase in the winter of 1977, somewhat earlier than the whole China, seven years earlier than Northwest China.The first summer temperature increasing jump appeared in 1988, five years earlier than Northwest China. 3) The effect of urban heat island was stronger in winter (0.65 ℃) than in summer (0.46 ℃). 4) In winter the average temperature increased 1.3 ℃ after the temperature jump in 1989, and the urban impact accounts for 0.35 ℃; In summer, the average temperature increased 0.4 ℃ after the temperature jump in 1987, and the urban impact accounts for 0.39 ℃. It indicates that the urban impact plays an important role in the temperature increase in summer. 5)The urbanization index, such as building proportion，the population of urban area and the quantity of the buses, and the variation of temperature are closely correlated. It can be concluded that the urbanization is the main reason for the temperature increase during the winters from 1989 to 1995, and the summers from 1987 to 1995.
Abstract:To analyze the influence of the changes in city underlying surface on human comfort, air temperature, relative humidity and wind velocity are observed in Nanjing University of Information Science and Technology with different kinds of underlying surface as woods, lawn, and bare land in April and May 2006. The data of air temperature, relative humidity, and wind velocity are used to evaluate the influences of climate environment on human comfort. Based on fuzzy mathematics, the comprehensive evaluation of human comfort for different kinds of underlying surfaces is made. The results show that from April to May it is the most comfortable on the lawn,while the least comfortable in the woods, and the that of woods is lower than that of lawn and bare land.
Abstract:Consulting the standards of atmospheric environment, the atmospheric environment quality of Huaian was evaluated by using the method of fuzzy mathematics, selecting SO2 , NO2 , PM10 as evaluation factors to caculate the weight of distribution coefficients and grade attachment of atmospheric pollution factors. The results of comprehensive evaluation indicated that the atmospheric environment of Huaian was moderately polluted, and it was deteriorated year after year. The results of comprehensive evaluation using the method of fuzzy mathematics were more objective than any other normal evaluation methods.