This article discussed about snow temperature variations and their impact on snow cover parameters. Automatic temperature recorders were used to sample at lo-minute intervals at the Tianshan Station for Snow-cover and...This article discussed about snow temperature variations and their impact on snow cover parameters. Automatic temperature recorders were used to sample at lo-minute intervals at the Tianshan Station for Snow-cover and Avalanche Research, Chinese snow temperature Academy of Sciences. lo-layer and the snow cover parameters were measured by the snow property analyzer （Snow Fork） in its Stable period, Interim period and Snow melting period. Results indicate that the amplitude of the diurnal fluctuation in the temperature during Snow melting period is 1.62 times greater than that during Stable period. Time up to the peak temperature at the snow surface lags behind the peak solar radiation by more than 2.5 hours, and lags behind the peak atmospheric temperature by more than 0.2 hours during all three periods. The optimal fitted function of snow temperature profile becomes more complicated from Stable period to Snow melting period. 22 h temperature profiles in Stable period are the optimal fitted by cubic polynomial equation. In Interim period and Snow melting period, temperature profiles are optimal fitted by exponential equation between sunset and sunrise, and by Fourier function when solar radiation is strong. The vertical gradient in the snow temperature reaches its maximum value at the snow surface for three periods. The peak of this maximum value occurs during Stableperiod, and is 4.46 times greater than during Interim period. The absolute value of temperature gradient is lower than 0.1℃ cm-1 for 30 cm beneath snow surface. Snow temperature and temperature gradient in Stable period-Interim period indirectly cause increase （decrease） of snow density mainly by increasing （decreasing） permittivity. While it dramatically increases its water content to change its permittivity and snow density in Snow melting period.展开更多
A two-moment bulk stratiform microphysics scheme, including recently developed physically-based droplet activation/ice nucleation parameterizations has been implemented into the Grid-point Atmospheric Model of IAP LA...A two-moment bulk stratiform microphysics scheme, including recently developed physically-based droplet activation/ice nucleation parameterizations has been implemented into the Grid-point Atmospheric Model of IAP LASG （GAMIL） as an effort to enhance the model＇s capability to simulate aerosol indirect effects. Unlike the previous one-moment cloud microphysics scheme, the new scheme produces a reasonable rep- resentation of cloud particle size and number concentration. This scheme captures the observed spatial variations in cloud droplet number concentrations. Simulated ice crystal number concentrations in cirrus clouds qualitatively agree with in situ observations. The longwave and shortwave cloud forcings are in better agreement with observations. Sensitivity tests show that the column cloud droplet number concentrations calculated from two different droplet activation parameterizations are similar. However, ice crystal number concentration in mixed-phased clouds is sensitive to different heterogeneous ice nucleation formulations. The simulation with high ice crystal number concentration in mixed-phase clouds has less liquid water path and weaker cloud forcing. ~rthermore, ice crystal number concentration in cirrus clouds is sensitive to different ice nucleation parameterizations. Sensitivity tests also suggest that the impact of pre-existing ice crystals on homogeneous freezing in old clouds should be taken into account.展开更多
Hourly summer precipitation data recorded at 21 stations during 1961-2004 in the Haihe River Basin in North China were an alyzed. The results show that the precipitation frequency and amount and the morning peak mainl...Hourly summer precipitation data recorded at 21 stations during 1961-2004 in the Haihe River Basin in North China were an alyzed. The results show that the precipitation frequency and amount and the morning peak mainly relating to longduratiol rainfall events decreased during this period, whereas the normalized afternoon peak mainly relating to short-duration event： increased, which may suggest that the proportion of short-duration rainfall has increased as the total summer rainfall has de creased. For short-duration events, the mean intensity and peak intensity increased at most stations and the time to peak inten sity decreased, which may be attributable to the higher thermal contrast between the warmer lower surface and cooler uppe level. In the case of long-duration events, the total amount was significantly correlated with the East Asian summer monsool index for the period 1961-2001 （correlation coefficient of 0.63）. Although the total amount of rainfall in long-duration event： decreased in the basin, the mean intensity and peak intensity, as well as the extreme hourly precipitation, increased in the western basin and decreased in the eastern basin.展开更多
One recent study by using instrumental records suggested the correlation between East Asian surface air temperatures(EATs)and the Atlantic Multidecadal Oscillation(AMO)reaches the maximum when the former leads the lat...One recent study by using instrumental records suggested the correlation between East Asian surface air temperatures(EATs)and the Atlantic Multidecadal Oscillation(AMO)reaches the maximum when the former leads the latter by 5–7 years.This seems to disagree with a previous well-realized point that the AMO modulates the decadal variation of EATs,since the atmosphere responds swiftly to sea surface temperature anomalies(SSTA)if therein.It implies that the AMO-EATs correlation should reach the maximum when they are simultaneous or the AMO leads EATs slightly,rather than that the EATs lead the AMO.Thus,this poses an issue about the reality of the newly found lead-lag correlation.Because the instrumental record in the natural climate system may be contaminated by human activities,the EATs-AMO lead-lag correlation derived from the instrumental records may not be a realistic connection of the natural climate system.Thus,whether the connection also exists in the proxies prior to the industrial is essential to answer the issue.In this study the EATs-AMO lead-lag connection is analyzed by using the reconstructed data in the last 500 years,together with the control experimental data with the prescribed pre-industrial forcing in a multiple of coupled climate system models,which attend the international CMIP5 program.The results suggest that the connection,the EATs lead the AMO,also exists in the period from the Little Ice Age(LIA)to the industrial,1500–1860AD.Therefore,the connection may be realistic in the natural climate system.The mechanisms for the connection are then discussed briefly.The results from this paper provide some insights into the connection of the AMO with East Asian climate.展开更多
基金supported by social welfare of Ministry Science and Technology Development of China (Grant No.GYHY200706008)the "Western Light" Project (RCPY200902) of the Chinese Academy of Sciencesthe Oasis Scholar "Doctor" Talent Training Program (0771021) of Xinjiang Institute of Ecology
文摘This article discussed about snow temperature variations and their impact on snow cover parameters. Automatic temperature recorders were used to sample at lo-minute intervals at the Tianshan Station for Snow-cover and Avalanche Research, Chinese snow temperature Academy of Sciences. lo-layer and the snow cover parameters were measured by the snow property analyzer （Snow Fork） in its Stable period, Interim period and Snow melting period. Results indicate that the amplitude of the diurnal fluctuation in the temperature during Snow melting period is 1.62 times greater than that during Stable period. Time up to the peak temperature at the snow surface lags behind the peak solar radiation by more than 2.5 hours, and lags behind the peak atmospheric temperature by more than 0.2 hours during all three periods. The optimal fitted function of snow temperature profile becomes more complicated from Stable period to Snow melting period. 22 h temperature profiles in Stable period are the optimal fitted by cubic polynomial equation. In Interim period and Snow melting period, temperature profiles are optimal fitted by exponential equation between sunset and sunrise, and by Fourier function when solar radiation is strong. The vertical gradient in the snow temperature reaches its maximum value at the snow surface for three periods. The peak of this maximum value occurs during Stableperiod, and is 4.46 times greater than during Interim period. The absolute value of temperature gradient is lower than 0.1℃ cm-1 for 30 cm beneath snow surface. Snow temperature and temperature gradient in Stable period-Interim period indirectly cause increase （decrease） of snow density mainly by increasing （decreasing） permittivity. While it dramatically increases its water content to change its permittivity and snow density in Snow melting period.
基金supported by the National Natural Science Funds of China(Grant No.41205071)the Ministry of Science and Technology of China for the National Basic Research Program of China(973 Program:Grant No.2011CB309704)the funding support from the U.S.Department of Energy(DOE),Office of Science,Earth System Modeling Program
文摘A two-moment bulk stratiform microphysics scheme, including recently developed physically-based droplet activation/ice nucleation parameterizations has been implemented into the Grid-point Atmospheric Model of IAP LASG （GAMIL） as an effort to enhance the model＇s capability to simulate aerosol indirect effects. Unlike the previous one-moment cloud microphysics scheme, the new scheme produces a reasonable rep- resentation of cloud particle size and number concentration. This scheme captures the observed spatial variations in cloud droplet number concentrations. Simulated ice crystal number concentrations in cirrus clouds qualitatively agree with in situ observations. The longwave and shortwave cloud forcings are in better agreement with observations. Sensitivity tests show that the column cloud droplet number concentrations calculated from two different droplet activation parameterizations are similar. However, ice crystal number concentration in mixed-phased clouds is sensitive to different heterogeneous ice nucleation formulations. The simulation with high ice crystal number concentration in mixed-phase clouds has less liquid water path and weaker cloud forcing. ~rthermore, ice crystal number concentration in cirrus clouds is sensitive to different ice nucleation parameterizations. Sensitivity tests also suggest that the impact of pre-existing ice crystals on homogeneous freezing in old clouds should be taken into account.
基金supported by the National Basic Research Program of China (Grant No. 2006CB403404)the National Key Technology R&D Program of China (Grant No. 2007 BAC29B04)the National Science Foundation Program for Post-doctoral Scientists of China (Grant No. 20080440343)
文摘Hourly summer precipitation data recorded at 21 stations during 1961-2004 in the Haihe River Basin in North China were an alyzed. The results show that the precipitation frequency and amount and the morning peak mainly relating to longduratiol rainfall events decreased during this period, whereas the normalized afternoon peak mainly relating to short-duration event： increased, which may suggest that the proportion of short-duration rainfall has increased as the total summer rainfall has de creased. For short-duration events, the mean intensity and peak intensity increased at most stations and the time to peak inten sity decreased, which may be attributable to the higher thermal contrast between the warmer lower surface and cooler uppe level. In the case of long-duration events, the total amount was significantly correlated with the East Asian summer monsool index for the period 1961-2001 （correlation coefficient of 0.63）. Although the total amount of rainfall in long-duration event： decreased in the basin, the mean intensity and peak intensity, as well as the extreme hourly precipitation, increased in the western basin and decreased in the eastern basin.
基金jointly supported by the National Natural Science Foundation of China(Grant Nos.41375085,41421004)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA05090406)
文摘One recent study by using instrumental records suggested the correlation between East Asian surface air temperatures(EATs)and the Atlantic Multidecadal Oscillation(AMO)reaches the maximum when the former leads the latter by 5–7 years.This seems to disagree with a previous well-realized point that the AMO modulates the decadal variation of EATs,since the atmosphere responds swiftly to sea surface temperature anomalies(SSTA)if therein.It implies that the AMO-EATs correlation should reach the maximum when they are simultaneous or the AMO leads EATs slightly,rather than that the EATs lead the AMO.Thus,this poses an issue about the reality of the newly found lead-lag correlation.Because the instrumental record in the natural climate system may be contaminated by human activities,the EATs-AMO lead-lag correlation derived from the instrumental records may not be a realistic connection of the natural climate system.Thus,whether the connection also exists in the proxies prior to the industrial is essential to answer the issue.In this study the EATs-AMO lead-lag connection is analyzed by using the reconstructed data in the last 500 years,together with the control experimental data with the prescribed pre-industrial forcing in a multiple of coupled climate system models,which attend the international CMIP5 program.The results suggest that the connection,the EATs lead the AMO,also exists in the period from the Little Ice Age(LIA)to the industrial,1500–1860AD.Therefore,the connection may be realistic in the natural climate system.The mechanisms for the connection are then discussed briefly.The results from this paper provide some insights into the connection of the AMO with East Asian climate.
