This study shows that the heretofore assumed condition for no temperature-profile (TP)/lapse-rate feedback, for all altitudes z, or , in fact yields a negative feedback. The correct condition for no TP feedback is for...This study shows that the heretofore assumed condition for no temperature-profile (TP)/lapse-rate feedback, for all altitudes z, or , in fact yields a negative feedback. The correct condition for no TP feedback is for all z, where Ts is the surface temperature. This condition translates into a uniform increase (decrease) in lapse rate with altitude for an increase (decrease) in Ts. The temperature changes caused by a change in solar irradiance and/or planetary albedo satisfy the condition for no TP feedback. The temperature changes caused by a change in greenhouse gas concentration do not satisfy the condition for no TP feedback and, instead, yield a positive feedback.展开更多
Although the residual layer has already been noted in the classical diurnal cycle of the atmospheric boundary layer, its effect on the development of the convective boundary layer has not been well studied. In this st...Although the residual layer has already been noted in the classical diurnal cycle of the atmospheric boundary layer, its effect on the development of the convective boundary layer has not been well studied. In this study, based on 3-hourly 20th century reanalysis data, the residual layer is considered as a common layer capping the convective boundary layer. It is identified dally by investigating the development of the convective boundary layer. The region of interest is bounded by （30^-60~N, 80^-120~E）, where a residual layer deeper than 2000 m has been reported using radiosondes. The lapse rate and wind shear within the residual layer are compared with the surface sensible heat flux by investigating their climatological means, interannual variations and daily variations. The lapse rate of the residual layer and the convective boundary layer depth correspond well in their seasonal variations and climatological mean patterns. On the interannual scale, the correlation coefficient between their regional averaged （40°-50°N, 90°-110°E） variations is higher than that between the surface sensible heat flux and convective boundary layer depth. On the daily scale, the correlation between the lapse rate and the convective boundary layer depth in most months is still statistically significant during 1970-2012. Therefore, we suggest that the existence of a deep neutral residual layer is crucial to the formation of a deep convective boundary layer near the Mongolian regions.展开更多
All numerical weather prediction（NWP） models inherently have substantial biases, especially in the forecast of near-surface weather variables. Statistical methods can be used to remove the systematic error based on ...All numerical weather prediction（NWP） models inherently have substantial biases, especially in the forecast of near-surface weather variables. Statistical methods can be used to remove the systematic error based on historical bias data at observation stations. However, many end users of weather forecasts need bias corrected forecasts at locations that scarcely have any historical bias data. To circumvent this limitation, the bias of surface temperature forecasts on a regular grid covering Iran is removed, by using the information available at observation stations in the vicinity of any given grid point. To this end, the running mean error method is first used to correct the forecasts at observation stations, then four interpolation methods including inverse distance squared weighting with constant lapse rate（IDSW-CLR）, Kriging with constant lapse rate（Kriging-CLR）, gradient inverse distance squared with linear lapse rate（GIDS-LR）, and gradient inverse distance squared with lapse rate determined by classification and regression tree（GIDS-CART）, are employed to interpolate the bias corrected forecasts at neighboring observation stations to any given location. The results show that all four interpolation methods used do reduce the model error significantly,but Kriging-CLR has better performance than the other methods. For Kriging-CLR, root mean square error（RMSE）and mean absolute error（MAE） were decreased by 26% and 29%, respectively, as compared to the raw forecasts. It is found also, that after applying any of the proposed methods, unlike the raw forecasts, the bias corrected forecasts do not show spatial or temporal dependency.展开更多
In this study the results from a boundary layer experiment,conducted in autumn 1991 over a flat,build-up urban area in Southeast Sofia,together with some models for mixed layer growth rates are used to investigate the...In this study the results from a boundary layer experiment,conducted in autumn 1991 over a flat,build-up urban area in Southeast Sofia,together with some models for mixed layer growth rates are used to investigate the layered struc- ture of the vertical atmospheric stability distribution in the Sofia Valley.Lidar measurements of aerosol layer heights and morning boundary layer development are combined with surface eddy correlation measurements of kinematic heat and moisture fluxes,profiles of temperature and humidity,wind speed and wind direction.A diagnostic method is pres- ented for determining vertical lapse rates using surface meteorological measurements and lidar returns observed during the transition from nighttime stable stratification to daytime convective boundary layer after the sunrise.展开更多
文摘This study shows that the heretofore assumed condition for no temperature-profile (TP)/lapse-rate feedback, for all altitudes z, or , in fact yields a negative feedback. The correct condition for no TP feedback is for all z, where Ts is the surface temperature. This condition translates into a uniform increase (decrease) in lapse rate with altitude for an increase (decrease) in Ts. The temperature changes caused by a change in solar irradiance and/or planetary albedo satisfy the condition for no TP feedback. The temperature changes caused by a change in greenhouse gas concentration do not satisfy the condition for no TP feedback and, instead, yield a positive feedback.
基金funded by the National Natural Science Foundation of China (Grant No. 41205005)the National Basic Research Program of China (Grant No.2010CB950503)+3 种基金the West Light Foundation of the Chinese Academy of Sciences to HAN Bo.The Twentieth Century Reanalysis Project dataset is provided by the U.S. Department of Energy, Office of Science Innovative and Novel Computational Impact on Theory and Experiment (DOE INCITE) programOffice of Biological and Environmental Research (BER)by the National Oceanic and Atmospheric Administration Climate Program Office
文摘Although the residual layer has already been noted in the classical diurnal cycle of the atmospheric boundary layer, its effect on the development of the convective boundary layer has not been well studied. In this study, based on 3-hourly 20th century reanalysis data, the residual layer is considered as a common layer capping the convective boundary layer. It is identified dally by investigating the development of the convective boundary layer. The region of interest is bounded by （30^-60~N, 80^-120~E）, where a residual layer deeper than 2000 m has been reported using radiosondes. The lapse rate and wind shear within the residual layer are compared with the surface sensible heat flux by investigating their climatological means, interannual variations and daily variations. The lapse rate of the residual layer and the convective boundary layer depth correspond well in their seasonal variations and climatological mean patterns. On the interannual scale, the correlation coefficient between their regional averaged （40°-50°N, 90°-110°E） variations is higher than that between the surface sensible heat flux and convective boundary layer depth. On the daily scale, the correlation between the lapse rate and the convective boundary layer depth in most months is still statistically significant during 1970-2012. Therefore, we suggest that the existence of a deep neutral residual layer is crucial to the formation of a deep convective boundary layer near the Mongolian regions.
文摘All numerical weather prediction（NWP） models inherently have substantial biases, especially in the forecast of near-surface weather variables. Statistical methods can be used to remove the systematic error based on historical bias data at observation stations. However, many end users of weather forecasts need bias corrected forecasts at locations that scarcely have any historical bias data. To circumvent this limitation, the bias of surface temperature forecasts on a regular grid covering Iran is removed, by using the information available at observation stations in the vicinity of any given grid point. To this end, the running mean error method is first used to correct the forecasts at observation stations, then four interpolation methods including inverse distance squared weighting with constant lapse rate（IDSW-CLR）, Kriging with constant lapse rate（Kriging-CLR）, gradient inverse distance squared with linear lapse rate（GIDS-LR）, and gradient inverse distance squared with lapse rate determined by classification and regression tree（GIDS-CART）, are employed to interpolate the bias corrected forecasts at neighboring observation stations to any given location. The results show that all four interpolation methods used do reduce the model error significantly,but Kriging-CLR has better performance than the other methods. For Kriging-CLR, root mean square error（RMSE）and mean absolute error（MAE） were decreased by 26% and 29%, respectively, as compared to the raw forecasts. It is found also, that after applying any of the proposed methods, unlike the raw forecasts, the bias corrected forecasts do not show spatial or temporal dependency.
基金The research was supported by Bulgarian National Foundation"Science"USDA Forest Service,Rocky Mountain Forest and Range Experiment Station,Fort Collins,Colorado,USA.
文摘In this study the results from a boundary layer experiment,conducted in autumn 1991 over a flat,build-up urban area in Southeast Sofia,together with some models for mixed layer growth rates are used to investigate the layered struc- ture of the vertical atmospheric stability distribution in the Sofia Valley.Lidar measurements of aerosol layer heights and morning boundary layer development are combined with surface eddy correlation measurements of kinematic heat and moisture fluxes,profiles of temperature and humidity,wind speed and wind direction.A diagnostic method is pres- ented for determining vertical lapse rates using surface meteorological measurements and lidar returns observed during the transition from nighttime stable stratification to daytime convective boundary layer after the sunrise.
