The Grid-point Atmospheric Model of IAP LASG version 1.0（GAMIL1.0） is used to investigate the impacts of different convective schemes on the radiative energy budget.The two convective schemes are Zhang and McFarlanc...The Grid-point Atmospheric Model of IAP LASG version 1.0（GAMIL1.0） is used to investigate the impacts of different convective schemes on the radiative energy budget.The two convective schemes are Zhang and McFarlance（1995）/Hack（1994）（ZM） and Tiedtke（1989）/Nordeng（1994）（TN）.Two simulations are performed：one with the ZM scheme（EX_ZM） and the other with the TN scheme（EX_TN）.The results indicate that during the convective process,more water vapor consumption and temperature increment are found in the EX_ZM,especially in the lower model layer,its environment is therefore very dry.In contrast, there is a moister atmosphere in the EX_TN,which favors low cloud formation and large-scale condensation, and hence more low cloud fraction,higher cloud water mixing ratio,and deeper cloud extinction optical depth are simulated,reflecting more solar radiative flux in the EX_TN.This explains why the TN scheme underestimates the net shortwave radiative flux at the top of the atmosphere and at surface.In addition, convection influences longwave radiation,surface sensible and latent heat fluxes through changes in cloud emissivity and precipitation.展开更多
This study investigates the interaction between convection, clouds, and the large-scale circulation. By examining the sensitivity of the large-scale fields to a modification of the convective parameterization scheme i...This study investigates the interaction between convection, clouds, and the large-scale circulation. By examining the sensitivity of the large-scale fields to a modification of the convective parameterization scheme in the NCAR CCM3, we show that the convective parameterization has a strong impact on the temporal characteristics of the large-scale circulation and clouds. When Convective Available Potential Energy (CAPE) in the atmosphere is used to close the convective parameterization, the simulated convection is continuous, and lacks the observed intermittence. When the CAPE change due to the large-scale forcing in the free troposphere is used, the simulated temporal behavior of convection is in much better agreement with the observations. We attribute this improvement to the enhanced coupling between convection and the large-scale forcing in the convective parameterization.展开更多
This paper describes explicit and parameterized simulations of midsummer precipitation over the continental United States for two distinct episodes： moderate large-scale forcing and weak forcing. The objective is to ...This paper describes explicit and parameterized simulations of midsummer precipitation over the continental United States for two distinct episodes： moderate large-scale forcing and weak forcing. The objective is to demonstrate the capability of explicit convection at currently affordable grid-resolution and compare it with parameterized realizations. Under moderate forcing, 3-kin grid-resolution explicit simulations represent rainfall coherence remarkably well. The observed daily convective generation near the Continental Divide and the subsequent organization and propagation are reproduced qualitatively. The propagation speed, zonal extent and duration of the rainfall streaks compare favorably with their observed counterparts, although the streak frequency is underestimated. The simulations at -10-km grid-resolution applying conventional convective parameterization schemes also replicate reasonably well the diurnal convective regeneration in moderate forcing. The performance of the 3-km grid-resolution model demonstrates the potential of -1-km-resolution explicit cloud-resolving models for the prediction of warm season precipitation for moderately forced environments. In weak forcing conditions, however, predictions of precipitation coherence and diurnal variability are much poorer. This suggests that an even finer resolution explicit model is required to adequately treat convective initiation and upscale organization typical of the warm season over the continental U.S.展开更多
In this study, the accuracy of a Pennsylvania State University–National Center for Atmospheric Research mesoscale model （PSU/NCAR MM5） for predicting heavy summer precipitation over the Korean Peninsula was investi...In this study, the accuracy of a Pennsylvania State University–National Center for Atmospheric Research mesoscale model （PSU/NCAR MM5） for predicting heavy summer precipitation over the Korean Peninsula was investigated. A total of 1800 simulations were performed using this model for 30 heavy rainfall events employing four cumulus parameterization schemes （CPS）, two grid-scale resolvable precipitation schemes （GRS）, and two planetary boundary layer （PBL） schemes in three model resolutions （90 km, 30 km, and 10 km）. The heavy rainfall events were mesoscale convective systems developed under the influence of mid-latitude baroclinic systems with low-level moisture transport from the ocean. The predictive accuracy for maximum rainfall was approximately 80% for 10-km resolution and was 60% for 30-km resolution. The predictive accuracy for rainfall position extended to ～150 km from the observed position for both resolutions. Simulated rainfall was most sensitive to CPS, then to PBL schemes, and then to GRS. In general, the Grell （GR） scheme and the Anthes and Kuo （AK） scheme showed a better prediction capability for heavy rainfall than did the Betts-Miller （BM） scheme and the Kain-Fritsch （KF） scheme. The GR scheme also performed well in the 24-h and 12-h precipitation predictions： the parameterized convective rainfall in GR is directly related to synoptic-scale forcing. The models without CPS performed better for rainfall amounts but worse for rainfall position than those with CPS. The MM5 model demonstrated substantial predictive capacity using synoptic-scale initial conditions and lateral boundary data because heavy summer rainfall in Korea occurs in a strong synoptic-scale environment.展开更多
基金Supported by the Knowledge Innovation Program of the Chinese Academy of Sciences under Grant No.KZCX2-YW-Q11-04the China Meteorological Administration R & D Special Fund for Public Welfare(meteorology)(Grant Nos.GYHY200806007, GYHY200806006,and GYHY200906020)+1 种基金Informalization Construction Project of Chinese Academy of Sciences during the 11th Five-Year Plan Period(No.INFO-115-B01)LASG State Key Laboratory Special Fund and LASG Free Exploration Fund
文摘The Grid-point Atmospheric Model of IAP LASG version 1.0（GAMIL1.0） is used to investigate the impacts of different convective schemes on the radiative energy budget.The two convective schemes are Zhang and McFarlance（1995）/Hack（1994）（ZM） and Tiedtke（1989）/Nordeng（1994）（TN）.Two simulations are performed：one with the ZM scheme（EX_ZM） and the other with the TN scheme（EX_TN）.The results indicate that during the convective process,more water vapor consumption and temperature increment are found in the EX_ZM,especially in the lower model layer,its environment is therefore very dry.In contrast, there is a moister atmosphere in the EX_TN,which favors low cloud formation and large-scale condensation, and hence more low cloud fraction,higher cloud water mixing ratio,and deeper cloud extinction optical depth are simulated,reflecting more solar radiative flux in the EX_TN.This explains why the TN scheme underestimates the net shortwave radiative flux at the top of the atmosphere and at surface.In addition, convection influences longwave radiation,surface sensible and latent heat fluxes through changes in cloud emissivity and precipitation.
基金This research was supported by the Institute of Geophysics and Planetary Physics of University ofCalifornia and the Los Alamos
文摘This study investigates the interaction between convection, clouds, and the large-scale circulation. By examining the sensitivity of the large-scale fields to a modification of the convective parameterization scheme in the NCAR CCM3, we show that the convective parameterization has a strong impact on the temporal characteristics of the large-scale circulation and clouds. When Convective Available Potential Energy (CAPE) in the atmosphere is used to close the convective parameterization, the simulated convection is continuous, and lacks the observed intermittence. When the CAPE change due to the large-scale forcing in the free troposphere is used, the simulated temporal behavior of convection is in much better agreement with the observations. We attribute this improvement to the enhanced coupling between convection and the large-scale forcing in the convective parameterization.
基金The National Center for Atmospheric Research is sponsored by the National Science Foundation.
文摘This paper describes explicit and parameterized simulations of midsummer precipitation over the continental United States for two distinct episodes： moderate large-scale forcing and weak forcing. The objective is to demonstrate the capability of explicit convection at currently affordable grid-resolution and compare it with parameterized realizations. Under moderate forcing, 3-kin grid-resolution explicit simulations represent rainfall coherence remarkably well. The observed daily convective generation near the Continental Divide and the subsequent organization and propagation are reproduced qualitatively. The propagation speed, zonal extent and duration of the rainfall streaks compare favorably with their observed counterparts, although the streak frequency is underestimated. The simulations at -10-km grid-resolution applying conventional convective parameterization schemes also replicate reasonably well the diurnal convective regeneration in moderate forcing. The performance of the 3-km grid-resolution model demonstrates the potential of -1-km-resolution explicit cloud-resolving models for the prediction of warm season precipitation for moderately forced environments. In weak forcing conditions, however, predictions of precipitation coherence and diurnal variability are much poorer. This suggests that an even finer resolution explicit model is required to adequately treat convective initiation and upscale organization typical of the warm season over the continental U.S.
基金funded by the Korea Meteorological Administration Research and Development Program under GrantRACS 2010-2016
文摘In this study, the accuracy of a Pennsylvania State University–National Center for Atmospheric Research mesoscale model （PSU/NCAR MM5） for predicting heavy summer precipitation over the Korean Peninsula was investigated. A total of 1800 simulations were performed using this model for 30 heavy rainfall events employing four cumulus parameterization schemes （CPS）, two grid-scale resolvable precipitation schemes （GRS）, and two planetary boundary layer （PBL） schemes in three model resolutions （90 km, 30 km, and 10 km）. The heavy rainfall events were mesoscale convective systems developed under the influence of mid-latitude baroclinic systems with low-level moisture transport from the ocean. The predictive accuracy for maximum rainfall was approximately 80% for 10-km resolution and was 60% for 30-km resolution. The predictive accuracy for rainfall position extended to ～150 km from the observed position for both resolutions. Simulated rainfall was most sensitive to CPS, then to PBL schemes, and then to GRS. In general, the Grell （GR） scheme and the Anthes and Kuo （AK） scheme showed a better prediction capability for heavy rainfall than did the Betts-Miller （BM） scheme and the Kain-Fritsch （KF） scheme. The GR scheme also performed well in the 24-h and 12-h precipitation predictions： the parameterized convective rainfall in GR is directly related to synoptic-scale forcing. The models without CPS performed better for rainfall amounts but worse for rainfall position than those with CPS. The MM5 model demonstrated substantial predictive capacity using synoptic-scale initial conditions and lateral boundary data because heavy summer rainfall in Korea occurs in a strong synoptic-scale environment.
