2015 Vol. 21, No. S1
2015, 21(S1): 1-10.
doi: 10.16555/j.1006-8775.2015.S1.001
Abstract:
Sensitivity experiments with atmospheric general circulation model CAM3 have been performed to investigate the atmospheric response to warm wintertime sea surface temperature anomalies in the Kuroshio Extension (KE). Mechanism for the sustaining abnormal atmospheric response to sea surface temperature anomaly (SSTA) is revealed. It is found that the warm wintertime SSTA in KE leads to soil moisture changes across the Asia continent. The abnormal soil moisture may possibly be one of the reasons for the sustaining of abnormal atmospheric response intrigued by SSTA. Oscillations of perturbations intrigued by warm wintertime SSTA in KE, which have similar frequencies with that of intrinsic atmospheric oscillations, are superposed on the atmospheric oscillations and propagate with primary periodic oscillation of the atmosphere. These SSTA-intrigued oscillations are coupled with natural atmospheric oscillation and finally become parts of it. This is probably another reason for the sustaining of abnormal atmospheric response to SSTA in KE.
Sensitivity experiments with atmospheric general circulation model CAM3 have been performed to investigate the atmospheric response to warm wintertime sea surface temperature anomalies in the Kuroshio Extension (KE). Mechanism for the sustaining abnormal atmospheric response to sea surface temperature anomaly (SSTA) is revealed. It is found that the warm wintertime SSTA in KE leads to soil moisture changes across the Asia continent. The abnormal soil moisture may possibly be one of the reasons for the sustaining of abnormal atmospheric response intrigued by SSTA. Oscillations of perturbations intrigued by warm wintertime SSTA in KE, which have similar frequencies with that of intrinsic atmospheric oscillations, are superposed on the atmospheric oscillations and propagate with primary periodic oscillation of the atmosphere. These SSTA-intrigued oscillations are coupled with natural atmospheric oscillation and finally become parts of it. This is probably another reason for the sustaining of abnormal atmospheric response to SSTA in KE.
2015, 21(S1): 11-22.
doi: 10.16555/j.1006-8775.2015.S1.002
Abstract:
A large area of unrealized precipitation is produced with the standard convective parameterization scheme in a high-resolution model, while subgrid-scale convection that cannot be explicitly resolved is omitted without convective parameterization. A modified version of the convection scheme with limited mass flux at cloud base is introduced into a south-China regional high-resolution model to alleviate these problems. A strong convection case and a weak convection case are selected to analyze the influence of limited cloud-base mass flux on precipitation forecast. The sensitivity of different limitation on mass flux at cloud base is also discussed. It is found that using instability energy closure for Simplified Arakawa- Schubert Scheme will produce better precipitation forecast than the primary closure based on quasi-equilibrium assumption. The influence of the convection scheme is dependent on the upper limit of mass flux at cloud base. The total rain amount is not so sensitive to the limitation of mass flux in the strong convection case as in the weak one. From the comparison of two different methods for limiting the cloud-base mass flux, it is found that shutting down the cumulus parameterization scheme completely when the cloud-base mass flux exceeds a given limitation is more suitable for the forecast of precipitation.
A large area of unrealized precipitation is produced with the standard convective parameterization scheme in a high-resolution model, while subgrid-scale convection that cannot be explicitly resolved is omitted without convective parameterization. A modified version of the convection scheme with limited mass flux at cloud base is introduced into a south-China regional high-resolution model to alleviate these problems. A strong convection case and a weak convection case are selected to analyze the influence of limited cloud-base mass flux on precipitation forecast. The sensitivity of different limitation on mass flux at cloud base is also discussed. It is found that using instability energy closure for Simplified Arakawa- Schubert Scheme will produce better precipitation forecast than the primary closure based on quasi-equilibrium assumption. The influence of the convection scheme is dependent on the upper limit of mass flux at cloud base. The total rain amount is not so sensitive to the limitation of mass flux in the strong convection case as in the weak one. From the comparison of two different methods for limiting the cloud-base mass flux, it is found that shutting down the cumulus parameterization scheme completely when the cloud-base mass flux exceeds a given limitation is more suitable for the forecast of precipitation.
2015, 21(S1): 23-33.
doi: 10.16555/j.1006-8775.2015.S1.003
Abstract:
The different impacts of El Niño during peak phases with and without a positive Indian Ocean Dipole (P-IOD) on the Northwest Pacific circulation were studied. The authors focused on the Northwest Pacific circulation features in the mature phase of El Niño from September to February of the next year. Composite maps and simulations demonstrate that the atmospheric circulation under the impact of El Niño with and without P-IOD exhibits large differences in temporal evolution and intensity. In single El Niño (SE) years without a P-IOD, an anomalous low-level anticyclonic circulation around the Philippines (PSAC) is instigated by the single El Niño-induced Indonesian subsidence. However, during the years when El Niño and a P-IOD matured simultaneously, a much greater anomalous subsidence over the western Pacific and the Maritime Continent occurred. The PSAC tends to occur earlier, is much stronger and has a longer lifetime than that during SE. More importantly, the PSAC shows a characteristic of an eastward movement from the southern South China Sea (SCS) to the Philippine Sea. This characteristic does not appear during SE. These patterns imply that a positive IOD event tends to exert a prominent influence on the PSAC during El Niño events and there is a combined impact of El Niño and P-IOD on the development of the PSAC.
The different impacts of El Niño during peak phases with and without a positive Indian Ocean Dipole (P-IOD) on the Northwest Pacific circulation were studied. The authors focused on the Northwest Pacific circulation features in the mature phase of El Niño from September to February of the next year. Composite maps and simulations demonstrate that the atmospheric circulation under the impact of El Niño with and without P-IOD exhibits large differences in temporal evolution and intensity. In single El Niño (SE) years without a P-IOD, an anomalous low-level anticyclonic circulation around the Philippines (PSAC) is instigated by the single El Niño-induced Indonesian subsidence. However, during the years when El Niño and a P-IOD matured simultaneously, a much greater anomalous subsidence over the western Pacific and the Maritime Continent occurred. The PSAC tends to occur earlier, is much stronger and has a longer lifetime than that during SE. More importantly, the PSAC shows a characteristic of an eastward movement from the southern South China Sea (SCS) to the Philippine Sea. This characteristic does not appear during SE. These patterns imply that a positive IOD event tends to exert a prominent influence on the PSAC during El Niño events and there is a combined impact of El Niño and P-IOD on the development of the PSAC.
2015, 21(S1): 34-45.
doi: 10.16555/j.1006-8775.2015.S1.004
Abstract:
Based on the adaptive network fuzzy inference system (ANFIS), methods to filter out the noise of impact factors from the main signal are discussed. Focusing on the abnormal weather conditions in 2010, we use the delay-relevant method to analyze the five members of the summer monsoon system that had the largest effect on the subtropical high anomalies from the observational data. ANFIS is suitable for research and simulation of subtropical highs that are difficult to describe accurately with dynamics, allowing the effect of five factors on the subtropical high anomalies to be examined. Our results show that the Mascarene cold high, the Indian monsoon latent heat flux, and the South China Sea monsoon trough had the largest effect on the subtropical high anomalies. Diagnostic analysis, with genetic algorithms (GA) and dynamical reconstruction theory, reconstructed the nonlinear dynamical model of the subtropical high and its main factors objectively and accurately from the sequence of observations in 2010. Furthermore, a dynamically extended forecast experiment is performed. The forecasts for the subtropical high area index, the Mascarene cold high index, the Indian monsoon latent heat flux, and the South China Sea monsoon trough index all show a strong short-term effect over less than 25 days. The forecasting trend is accurate, and the error rate is no more than 7%. Our results provide new insight and methods for research on the association between the western Pacific subtropical high and the East Asian summer monsoon system, and for the prediction of the western Pacific subtropical high index.
Based on the adaptive network fuzzy inference system (ANFIS), methods to filter out the noise of impact factors from the main signal are discussed. Focusing on the abnormal weather conditions in 2010, we use the delay-relevant method to analyze the five members of the summer monsoon system that had the largest effect on the subtropical high anomalies from the observational data. ANFIS is suitable for research and simulation of subtropical highs that are difficult to describe accurately with dynamics, allowing the effect of five factors on the subtropical high anomalies to be examined. Our results show that the Mascarene cold high, the Indian monsoon latent heat flux, and the South China Sea monsoon trough had the largest effect on the subtropical high anomalies. Diagnostic analysis, with genetic algorithms (GA) and dynamical reconstruction theory, reconstructed the nonlinear dynamical model of the subtropical high and its main factors objectively and accurately from the sequence of observations in 2010. Furthermore, a dynamically extended forecast experiment is performed. The forecasts for the subtropical high area index, the Mascarene cold high index, the Indian monsoon latent heat flux, and the South China Sea monsoon trough index all show a strong short-term effect over less than 25 days. The forecasting trend is accurate, and the error rate is no more than 7%. Our results provide new insight and methods for research on the association between the western Pacific subtropical high and the East Asian summer monsoon system, and for the prediction of the western Pacific subtropical high index.
2015, 21(S1): 46-56.
doi: 10.16555/j.1006-8775.2015.S1.005
Abstract:
In this paper, we evaluate the characteristics of the surface air temperature and the precipitation of summer monsoon, using the National Centers for Environmental Prediction (NCEP) Regional Spectral Model (RSM) for 20 years (1984-2003). The RSM model was designated over the eastern China with a horizontal grid spacing of approximately 30 km. The model is driven by the NCEP/NCAR reanalysis data and runs from May 21 to September 1 for each of the 20 years. The distribution and variation patterns of the 20-year summer mean surface air temperature and precipitation are reproduced by the RSM and the differences between the simulation and observation are small. However, the model overestimates the interannual variability of summer precipitation in eastern China. The correlation coefficients of the 20-year averaging summer precipitation over the whole region and the sub-domains are above 0.8. The simulated probability distributions of daily maximum and minimum temperatures are similar to the observations. Days of different precipitation intensities in the simulations are generally consistent with the observations: the simulated days of light rain, moderate rain, heavy rain and torrential rain closely resemble the observations, but the simulated maximum centers of the distribution are north of the observed ones.
In this paper, we evaluate the characteristics of the surface air temperature and the precipitation of summer monsoon, using the National Centers for Environmental Prediction (NCEP) Regional Spectral Model (RSM) for 20 years (1984-2003). The RSM model was designated over the eastern China with a horizontal grid spacing of approximately 30 km. The model is driven by the NCEP/NCAR reanalysis data and runs from May 21 to September 1 for each of the 20 years. The distribution and variation patterns of the 20-year summer mean surface air temperature and precipitation are reproduced by the RSM and the differences between the simulation and observation are small. However, the model overestimates the interannual variability of summer precipitation in eastern China. The correlation coefficients of the 20-year averaging summer precipitation over the whole region and the sub-domains are above 0.8. The simulated probability distributions of daily maximum and minimum temperatures are similar to the observations. Days of different precipitation intensities in the simulations are generally consistent with the observations: the simulated days of light rain, moderate rain, heavy rain and torrential rain closely resemble the observations, but the simulated maximum centers of the distribution are north of the observed ones.
2015, 21(S1): 57-65.
doi: 10.16555/j.1006-8775.2015.S1.006
Abstract:
Using the 2006 Global Emissions Data and 2011 NCEP Final Analysis data as the initial and boundary condition, we simulated the three-dimensional distribution of atmospheric chemical pollutants (such as sea salt, PM10, COx, SO2, NOx, O3, etc) during the onset stage of South China Sea (SCS) summer monsoon from 25 April to 25 May in 2011 over the monsoon area of 70°–C160°E, 0°–C40°N. Simulation results shows that, many changes have taken place in the distribution of atmospheric chemical pollutants near 950 hPa and 400 hPa due to the enhancement of the westerlies and southerlies over the SCS as a result of the monsoon outbreak. Especially, the concentration of pollutants over the SCS is much higher than that over other places because of the strong wind convergence near the surface in situ. Moreover, the vertical distribution of pollutants is also greatly affected by the westerlies and southerlies in the onset process of SCS summer monsoon. Meanwhile, the concentration over land is much greater than that at sea in pre-monsoon period, while the difference between land and sea in the concentration of most pollutants decreases greatly with the onset of SCS summer monsoon.
Using the 2006 Global Emissions Data and 2011 NCEP Final Analysis data as the initial and boundary condition, we simulated the three-dimensional distribution of atmospheric chemical pollutants (such as sea salt, PM10, COx, SO2, NOx, O3, etc) during the onset stage of South China Sea (SCS) summer monsoon from 25 April to 25 May in 2011 over the monsoon area of 70°–C160°E, 0°–C40°N. Simulation results shows that, many changes have taken place in the distribution of atmospheric chemical pollutants near 950 hPa and 400 hPa due to the enhancement of the westerlies and southerlies over the SCS as a result of the monsoon outbreak. Especially, the concentration of pollutants over the SCS is much higher than that over other places because of the strong wind convergence near the surface in situ. Moreover, the vertical distribution of pollutants is also greatly affected by the westerlies and southerlies in the onset process of SCS summer monsoon. Meanwhile, the concentration over land is much greater than that at sea in pre-monsoon period, while the difference between land and sea in the concentration of most pollutants decreases greatly with the onset of SCS summer monsoon.
2015, 21(S1): 66-72.
doi: 10.16555/j.1006-8775.2015.S1.007
Abstract:
In this study, the relationship between scale and vertical velocity in a low-pressure system is explored using the wave characteristics of atmospheric disturbances and the structural characteristics of low-pressure systems. The ω differential equation, as determined by the transient geopotential height field Φ, is solved to obtain an analytical solution composed only of wavelength, horizontal speed, and atmospheric stability, i.e., the ω diagnostic equation of a low-pressure system. This equation also shows that vertical velocity in the low-pressure system is very sensitive to the horizontal scale, i.e., a smaller horizontal scale means a larger vertical velocity.
In this study, the relationship between scale and vertical velocity in a low-pressure system is explored using the wave characteristics of atmospheric disturbances and the structural characteristics of low-pressure systems. The ω differential equation, as determined by the transient geopotential height field Φ, is solved to obtain an analytical solution composed only of wavelength, horizontal speed, and atmospheric stability, i.e., the ω diagnostic equation of a low-pressure system. This equation also shows that vertical velocity in the low-pressure system is very sensitive to the horizontal scale, i.e., a smaller horizontal scale means a larger vertical velocity.
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