Daily precipitation anomalies in the western North Pacific(WNP)and East Asia(EA)exhibit significant intraseasonal variability,peaking at 10-30-day time scales.It has been suggested that boreal summer intraseasonal osc...Daily precipitation anomalies in the western North Pacific(WNP)and East Asia(EA)exhibit significant intraseasonal variability,peaking at 10-30-day time scales.It has been suggested that boreal summer intraseasonal oscillation(BSISO)on 30-60-day time scales is strongly modulated by El Niño-Southern Oscillation(ENSO)with stronger intensity and propagation during La Niña compared to El Niño summers,but the dependency of 10-30-day BSISO on ENSO has not been well understood.Here,we show that the intensity and northward propagation of the 10-30-day BSISO convection over the WNP-EA region are stronger and more organized during El Niño developing summers than other summers,including neutral summers.During El Niño developing summers,the BSISO-induced precipitation and low-level circulation tend to exhibit a stronger meridional tripolar pattern than those during neutral summers.We highlight that the strengthening of 10-30-day BSISO northward propagation and associated rainfall anomalies over EA in El Niño developing summers is contributed by not only the previously proposed stronger air-sea interaction with a larger meridional gradient of sea surface temperature,but also an enhanced dynamic process with stronger relative vorticity and moisture convergence.展开更多
The performances of various dynamical models from the Asia-Pacific Economic Cooperation（APEC） Climate Center（APCC） multi-model ensemble（MME） in predicting station-scale rainfall in South China（SC） in June were...The performances of various dynamical models from the Asia-Pacific Economic Cooperation（APEC） Climate Center（APCC） multi-model ensemble（MME） in predicting station-scale rainfall in South China（SC） in June were evaluated.It was found that the MME mean of model hindcasts can skillfully predict the June rainfall anomaly averaged over the SC domain.This could be related to the MME＇s ability in capturing the observed linkages between SC rainfall and atmospheric large-scale circulation anomalies in the Indo-Pacific region.Further assessment of station-scale June rainfall prediction based on direct model output（DMO） over 97 stations in SC revealed that the MME mean outperforms each individual model.However,poor prediction abilities in some in-land and southeastern SC stations are apparent in the MME mean and in a number of models.In order to improve the performance at those stations with poor DMO prediction skill,a station-based statistical downscaling scheme was constructed and applied to the individual and MME mean hindcast runs.For several models,this scheme can outperform DMO at more than 30 stations,because it can tap into the abilities of the models in capturing the anomalous Indo-Paciric circulation to which SC rainfall is considerably sensitive.Therefore,enhanced rainfall prediction abilities in these models should make them more useful for disaster preparedness and mitigation purposes.展开更多
In this paper,we introduced parameterizations of the salinity effects(on heat capacity,thermal conductivity,freezing point and saturated vapor pressure) in a lake scheme integrated in the Weather Research and Forecast...In this paper,we introduced parameterizations of the salinity effects(on heat capacity,thermal conductivity,freezing point and saturated vapor pressure) in a lake scheme integrated in the Weather Research and Forecasting model coupled with the Community Land Model(WRF-CLM). This was done to improve temperature simulation over and in a saline lake and to test the contributions of salinity effects on various water properties via sensitivity experiments. The modified lake scheme consists of the lake module in the CLM model,which is the land component of the WRF-CLM model. The Great Salt Lake(GSL) in the USA was selected as the study area. The simulation was performed from September 3,2001 to September 30,2002. Our results show that the modif ied WRF-CLM model that includes the lake scheme considering salinity effects can reasonably simulate temperature over and in the GSL. This model had much greater accuracy than neglecting salinity effects,particularly in a very cold event when that effect alters the freezing point. The salinity effect on saturated vapor pressure can reduce latent heat flux over the lake and make it slightly warmer. The salinity effect on heat capacity can also make lake temperature prone to changes. However,the salinity effect on thermal conductivity was found insignificant in our simulations.展开更多
Using 32 CMIP5（Coupled Model Intercomparison Project Phase 5） models, this study examines the veracity in the simulation of cloud amount and their radiative effects（CREs） in the historical run driven by observed e...Using 32 CMIP5（Coupled Model Intercomparison Project Phase 5） models, this study examines the veracity in the simulation of cloud amount and their radiative effects（CREs） in the historical run driven by observed external radiative forcing for 1850-2005, and their future changes in the RCP（Representative Concentration Pathway） 4.5 scenario runs for2006-2100. Validation metrics for the historical run are designed to examine the accuracy in the representation of spatial patterns for climatological mean, and annual and interannual variations of clouds and CREs. The models show large spread in the simulation of cloud amounts, specifically in the low cloud amount. The observed relationship between cloud amount and the controlling large-scale environment are also reproduced diversely by various models. Based on the validation metrics,four models-ACCESS1.0, ACCESS1.3, Had GEM2-CC, and Had GEM2-ES-are selected as best models, and the average of the four models performs more skillfully than the multimodel ensemble average.All models project global-mean SST warming at the increase of the greenhouse gases, but the magnitude varies across the simulations between 1 and 2 K, which is largely attributable to the difference in the change of cloud amount and distribution. The models that simulate more SST warming show a greater increase in the net CRE due to reduced low cloud and increased incoming shortwave radiation, particularly over the regions of marine boundary layer in the subtropics. Selected best-performing models project a significant reduction in global-mean cloud amount of about-0.99% K^-1and net radiative warming of 0.46 W m^-2K^-1, suggesting a role of positive feedback to global warming.展开更多
基金funded by the National Research Foundation of Korea(Grant Nos.NRF-2022R1A2C1013296,NRF-2022M3K3A1097082,and RS-2024-00416848)the National Natural Science Foundation of China(Grant No.NSFC042088101).
文摘Daily precipitation anomalies in the western North Pacific(WNP)and East Asia(EA)exhibit significant intraseasonal variability,peaking at 10-30-day time scales.It has been suggested that boreal summer intraseasonal oscillation(BSISO)on 30-60-day time scales is strongly modulated by El Niño-Southern Oscillation(ENSO)with stronger intensity and propagation during La Niña compared to El Niño summers,but the dependency of 10-30-day BSISO on ENSO has not been well understood.Here,we show that the intensity and northward propagation of the 10-30-day BSISO convection over the WNP-EA region are stronger and more organized during El Niño developing summers than other summers,including neutral summers.During El Niño developing summers,the BSISO-induced precipitation and low-level circulation tend to exhibit a stronger meridional tripolar pattern than those during neutral summers.We highlight that the strengthening of 10-30-day BSISO northward propagation and associated rainfall anomalies over EA in El Niño developing summers is contributed by not only the previously proposed stronger air-sea interaction with a larger meridional gradient of sea surface temperature,but also an enhanced dynamic process with stronger relative vorticity and moisture convergence.
基金supported by the City University of Hong Kong(Grant No.9360126)
文摘The performances of various dynamical models from the Asia-Pacific Economic Cooperation（APEC） Climate Center（APCC） multi-model ensemble（MME） in predicting station-scale rainfall in South China（SC） in June were evaluated.It was found that the MME mean of model hindcasts can skillfully predict the June rainfall anomaly averaged over the SC domain.This could be related to the MME＇s ability in capturing the observed linkages between SC rainfall and atmospheric large-scale circulation anomalies in the Indo-Pacific region.Further assessment of station-scale June rainfall prediction based on direct model output（DMO） over 97 stations in SC revealed that the MME mean outperforms each individual model.However,poor prediction abilities in some in-land and southeastern SC stations are apparent in the MME mean and in a number of models.In order to improve the performance at those stations with poor DMO prediction skill,a station-based statistical downscaling scheme was constructed and applied to the individual and MME mean hindcast runs.For several models,this scheme can outperform DMO at more than 30 stations,because it can tap into the abilities of the models in capturing the anomalous Indo-Paciric circulation to which SC rainfall is considerably sensitive.Therefore,enhanced rainfall prediction abilities in these models should make them more useful for disaster preparedness and mitigation purposes.
基金Supported by the National Natural Science Foundation of China(No.41130961)the Strategic Priority Research Program(B)of Chinese Academy of Sciences(No.XDB03030300)+1 种基金the National Natural Science Foundation of China(Nos.41475011,41275014)Visiting Scholars Program of the Public School Study Abroad Project of Chinese Academy of Sciences(No.2008-No.136)
文摘In this paper,we introduced parameterizations of the salinity effects(on heat capacity,thermal conductivity,freezing point and saturated vapor pressure) in a lake scheme integrated in the Weather Research and Forecasting model coupled with the Community Land Model(WRF-CLM). This was done to improve temperature simulation over and in a saline lake and to test the contributions of salinity effects on various water properties via sensitivity experiments. The modified lake scheme consists of the lake module in the CLM model,which is the land component of the WRF-CLM model. The Great Salt Lake(GSL) in the USA was selected as the study area. The simulation was performed from September 3,2001 to September 30,2002. Our results show that the modif ied WRF-CLM model that includes the lake scheme considering salinity effects can reasonably simulate temperature over and in the GSL. This model had much greater accuracy than neglecting salinity effects,particularly in a very cold event when that effect alters the freezing point. The salinity effect on saturated vapor pressure can reduce latent heat flux over the lake and make it slightly warmer. The salinity effect on heat capacity can also make lake temperature prone to changes. However,the salinity effect on thermal conductivity was found insignificant in our simulations.
基金supported by the APEC Climate Centersupported by the UNIST research fund (Grant No. 1.09006.01)provided by a grant (Grant No. 14AWMP-B082564-01) from the Advanced Water Management Research Program funded by the Ministry of Land, Infrastructure and Transport of the Korean government
文摘Using 32 CMIP5（Coupled Model Intercomparison Project Phase 5） models, this study examines the veracity in the simulation of cloud amount and their radiative effects（CREs） in the historical run driven by observed external radiative forcing for 1850-2005, and their future changes in the RCP（Representative Concentration Pathway） 4.5 scenario runs for2006-2100. Validation metrics for the historical run are designed to examine the accuracy in the representation of spatial patterns for climatological mean, and annual and interannual variations of clouds and CREs. The models show large spread in the simulation of cloud amounts, specifically in the low cloud amount. The observed relationship between cloud amount and the controlling large-scale environment are also reproduced diversely by various models. Based on the validation metrics,four models-ACCESS1.0, ACCESS1.3, Had GEM2-CC, and Had GEM2-ES-are selected as best models, and the average of the four models performs more skillfully than the multimodel ensemble average.All models project global-mean SST warming at the increase of the greenhouse gases, but the magnitude varies across the simulations between 1 and 2 K, which is largely attributable to the difference in the change of cloud amount and distribution. The models that simulate more SST warming show a greater increase in the net CRE due to reduced low cloud and increased incoming shortwave radiation, particularly over the regions of marine boundary layer in the subtropics. Selected best-performing models project a significant reduction in global-mean cloud amount of about-0.99% K^-1and net radiative warming of 0.46 W m^-2K^-1, suggesting a role of positive feedback to global warming.
