2024 Vol. 41, No. 1
Display Method:
2024, 41(1): 1-7.
doi: 10.1007/s00376-023-3107-5
Abstract:
In this study, we introduce our newly developed measurement-fed-perception self-adaption Low-cost UAV Coordinated Carbon Observation Network (LUCCN) prototype. The LUCCN primarily consists of two categories of instruments, including ground-based and UAV-based in-situ measurement. We use the GMP343, a low-cost non-dispersive infrared sensor, in both ground-based and UAV-based instruments. The first integrated measurement campaign took place in Shenzhen, China, 4 May 2023. During the campaign, we found that LUCCN’s UAV component presented significant data-collecting advantages over its ground-based counterpart owing to the relatively high altitudes of the point emission sources, which was especially obvious at a gas power plant in Shenzhen. The emission flux was calculated by a cross-sectional flux (CSF) method, the results of which differed from the Open-Data Inventory for Anthropogenic Carbon dioxide (ODIAC). The CSF result was slightly larger than others because of the low sampling rate of the whole emission cross section. The LUCCN system will be applied in future carbon monitoring campaigns to increase the spatiotemporal coverage of carbon emission information, especially in scenarios involving the detection of smaller-scale, rapidly varying sources and sinks.
In this study, we introduce our newly developed measurement-fed-perception self-adaption Low-cost UAV Coordinated Carbon Observation Network (LUCCN) prototype. The LUCCN primarily consists of two categories of instruments, including ground-based and UAV-based in-situ measurement. We use the GMP343, a low-cost non-dispersive infrared sensor, in both ground-based and UAV-based instruments. The first integrated measurement campaign took place in Shenzhen, China, 4 May 2023. During the campaign, we found that LUCCN’s UAV component presented significant data-collecting advantages over its ground-based counterpart owing to the relatively high altitudes of the point emission sources, which was especially obvious at a gas power plant in Shenzhen. The emission flux was calculated by a cross-sectional flux (CSF) method, the results of which differed from the Open-Data Inventory for Anthropogenic Carbon dioxide (ODIAC). The CSF result was slightly larger than others because of the low sampling rate of the whole emission cross section. The LUCCN system will be applied in future carbon monitoring campaigns to increase the spatiotemporal coverage of carbon emission information, especially in scenarios involving the detection of smaller-scale, rapidly varying sources and sinks.
2024, 41(1): 8-18.
doi: 10.1007/s00376-023-2386-1
Abstract:
In this study, we put forward a radiative-convective-transportive energy balance model of a gray atmosphere to examine individual roles of the greenhouse effect of water vapor, vertical convection, and atmospheric poleward energy transport as well as their combined effects for a quasi-linear relationship between the outgoing longwave radiation (OLR) and surface temperature (TS). The greenhouse effect of water vapor enhances the meridional gradient of surface temperature, thereby directly contributing to a quasi-linear OLR-TS relationship. The atmospheric poleward energy transport decreases the meridional gradient of surface temperature. As a result of the poleward energy transport, tropical (high-latitude) atmosphere-surface columns emit less (more) OLR than the solar energy input at their respective locations, causing a substantial reduction of the meridional gradient of the OLR. The combined effect of reducing the meridional gradients of both OLR and surface temperature by the poleward energy transport also contributes to the quasi-linear OLR-TS relationship. Vertical convective energy transport reduces the meridional gradient of surface temperature without affecting the meridional gradient of OLR, thereby suppressing part of the reduction to the increasing rate of OLR with surface temperature by the greenhouse effect of water vapor and poleward energy transport. Because of the nature of the energy balance in the climate system, such a quasi-linear relationship is also a good approximation for the relationship between the annual-mean net downward solar energy flux at the top of the atmosphere and surface temperature.
In this study, we put forward a radiative-convective-transportive energy balance model of a gray atmosphere to examine individual roles of the greenhouse effect of water vapor, vertical convection, and atmospheric poleward energy transport as well as their combined effects for a quasi-linear relationship between the outgoing longwave radiation (OLR) and surface temperature (TS). The greenhouse effect of water vapor enhances the meridional gradient of surface temperature, thereby directly contributing to a quasi-linear OLR-TS relationship. The atmospheric poleward energy transport decreases the meridional gradient of surface temperature. As a result of the poleward energy transport, tropical (high-latitude) atmosphere-surface columns emit less (more) OLR than the solar energy input at their respective locations, causing a substantial reduction of the meridional gradient of the OLR. The combined effect of reducing the meridional gradients of both OLR and surface temperature by the poleward energy transport also contributes to the quasi-linear OLR-TS relationship. Vertical convective energy transport reduces the meridional gradient of surface temperature without affecting the meridional gradient of OLR, thereby suppressing part of the reduction to the increasing rate of OLR with surface temperature by the greenhouse effect of water vapor and poleward energy transport. Because of the nature of the energy balance in the climate system, such a quasi-linear relationship is also a good approximation for the relationship between the annual-mean net downward solar energy flux at the top of the atmosphere and surface temperature.
2024, 41(1): 19-38.
doi: 10.1007/s00376-023-2332-2
Abstract:
High spatiotemporal resolution radiances from the advanced imagers onboard the new generation of geostationary weather satellites provide a unique opportunity to evaluate the abilities of various reanalysis datasets to depict multilayer tropospheric water vapor (WV), thereby enhancing our understanding of the deficiencies of WV in reanalysis datasets. Based on daily measurements from the Advanced Himawari Imager (AHI) onboard the Himawari-8 satellite in 2016, the bias features of multilayer WV from six reanalysis datasets over East Asia are thoroughly evaluated. The assessments show that wet biases exist in the upper troposphere in all six reanalysis datasets; in particular, these biases are much larger in summer. Overall, we find better depictions of WV in the middle troposphere than in the upper troposphere. The accuracy of WV in the ERA5 dataset is the highest, in terms of the bias magnitude, dispersion, and pattern similarity. The characteristics of the WV bias over the Tibetan Plateau are significantly different from those over other parts of East Asia. In addition, the reanalysis datasets all capture the shift of the subtropical high very well, with ERA5 performing better overall.
High spatiotemporal resolution radiances from the advanced imagers onboard the new generation of geostationary weather satellites provide a unique opportunity to evaluate the abilities of various reanalysis datasets to depict multilayer tropospheric water vapor (WV), thereby enhancing our understanding of the deficiencies of WV in reanalysis datasets. Based on daily measurements from the Advanced Himawari Imager (AHI) onboard the Himawari-8 satellite in 2016, the bias features of multilayer WV from six reanalysis datasets over East Asia are thoroughly evaluated. The assessments show that wet biases exist in the upper troposphere in all six reanalysis datasets; in particular, these biases are much larger in summer. Overall, we find better depictions of WV in the middle troposphere than in the upper troposphere. The accuracy of WV in the ERA5 dataset is the highest, in terms of the bias magnitude, dispersion, and pattern similarity. The characteristics of the WV bias over the Tibetan Plateau are significantly different from those over other parts of East Asia. In addition, the reanalysis datasets all capture the shift of the subtropical high very well, with ERA5 performing better overall.
2024, 41(1): 39-52.
doi: 10.1007/s00376-023-2388-z
Abstract:
The three-orbit constellation can comprehensively increase the spatial coverage of polar-orbiting satellites, but the polar-orbiting satellites currently in operation are only mid-morning-orbit and afternoon-orbit satellites. Fengyun-3E (FY-3E) was launched successfully on 5 July 2021 in China. As an early-morning-orbit satellite, FY-3E can help form a complete three-orbit observation system together with the mid-morning and afternoon satellites in the current mainstream operational system. In this study, we investigate the added benefit of FY-3E microwave sounding observations to the mid-morning-orbit Meteorological Operational satellite-B (MetOp-B) and afternoon-orbit Fengyun-3D (FY-3D) microwave observations in the Chinese Meteorological Administration global forecast system (CMA-GFS). The results show that the additional FY-3E microwave temperature sounder-3 (MWTS-3) and microwave humidity sounder-2 (MWHS-2) data can increase the global coverage of microwave temperature and humidity sounding data by 14.8% and 10.6%, respectively. It enables the CMA-GFS to achieve nearly 100% global coverage of microwave-sounding observations at each analysis time. Furthermore, after effective quality control and bias correction, the global biases and standard deviations of the differences between observations and model simulations are also reduced. Based on the Advanced Microwave Sounding Unit A and the Microwave Humidity Sounder onboard MetOp-B, and the MWTS-2 and MWHS-2 onboard FY-3D, adding the microwave sounding data of FY-3E can further reduce the errors of analysis results and improve the global prediction skills of CMA-GFS, especially for the southern-hemisphere forecasts within 96 hours, all of which are significant at the 95% confidence level.
The three-orbit constellation can comprehensively increase the spatial coverage of polar-orbiting satellites, but the polar-orbiting satellites currently in operation are only mid-morning-orbit and afternoon-orbit satellites. Fengyun-3E (FY-3E) was launched successfully on 5 July 2021 in China. As an early-morning-orbit satellite, FY-3E can help form a complete three-orbit observation system together with the mid-morning and afternoon satellites in the current mainstream operational system. In this study, we investigate the added benefit of FY-3E microwave sounding observations to the mid-morning-orbit Meteorological Operational satellite-B (MetOp-B) and afternoon-orbit Fengyun-3D (FY-3D) microwave observations in the Chinese Meteorological Administration global forecast system (CMA-GFS). The results show that the additional FY-3E microwave temperature sounder-3 (MWTS-3) and microwave humidity sounder-2 (MWHS-2) data can increase the global coverage of microwave temperature and humidity sounding data by 14.8% and 10.6%, respectively. It enables the CMA-GFS to achieve nearly 100% global coverage of microwave-sounding observations at each analysis time. Furthermore, after effective quality control and bias correction, the global biases and standard deviations of the differences between observations and model simulations are also reduced. Based on the Advanced Microwave Sounding Unit A and the Microwave Humidity Sounder onboard MetOp-B, and the MWTS-2 and MWHS-2 onboard FY-3D, adding the microwave sounding data of FY-3E can further reduce the errors of analysis results and improve the global prediction skills of CMA-GFS, especially for the southern-hemisphere forecasts within 96 hours, all of which are significant at the 95% confidence level.
2024, 41(1): 53-72.
doi: 10.1007/s00376-023-3011-z
Abstract:
By using the multi-taper method (MTM) of singular value decomposition (SVD), this study investigates the interdecadal evolution (10- to 30-year cycle) of precipitation over eastern China from 1951 to 2015 and its relationship with the North Pacific sea surface temperature (SST). Two significant interdecadal signals, one with an 11-year cycle and the other with a 23-year cycle, are identified in both the precipitation and SST fields. Results show that the North Pacific SST forcing modulates the precipitation distribution over China through the effects of the Pacific Decadal Oscillation (PDO)-related anomalous Aleutian low on the western Pacific subtropical high (WPSH) and Mongolia high (MH). During the development stage of the PDO cold phase associated with the 11-year cycle, a weakened WPSH and MH increased the precipitation over the Yangtze River Basin, whereas an intensified WPSH and MH caused the enhanced rain band to move northward to North China during the decay stage. During the development stage of the PDO cold phase associated with the 23-year cycle, a weakened WPSH and MH increased the precipitation over North China, whereas an intensified WPSH and the weakened MH increased the precipitation over South China during the decay stage. The 11-year and 23-year variabilities contribute differently to the precipitation variations in the different regions of China, as seen in the 1998 flooding case. The 11-year cycle mainly accounts for precipitation increases over the Yangtze River Basin, while the 23-year cycle is responsible for the precipitation increase over Northeast China. These results have important implications for understanding how the PDO modulates the precipitation distribution over China, helping to improve interdecadal climate prediction.
By using the multi-taper method (MTM) of singular value decomposition (SVD), this study investigates the interdecadal evolution (10- to 30-year cycle) of precipitation over eastern China from 1951 to 2015 and its relationship with the North Pacific sea surface temperature (SST). Two significant interdecadal signals, one with an 11-year cycle and the other with a 23-year cycle, are identified in both the precipitation and SST fields. Results show that the North Pacific SST forcing modulates the precipitation distribution over China through the effects of the Pacific Decadal Oscillation (PDO)-related anomalous Aleutian low on the western Pacific subtropical high (WPSH) and Mongolia high (MH). During the development stage of the PDO cold phase associated with the 11-year cycle, a weakened WPSH and MH increased the precipitation over the Yangtze River Basin, whereas an intensified WPSH and MH caused the enhanced rain band to move northward to North China during the decay stage. During the development stage of the PDO cold phase associated with the 23-year cycle, a weakened WPSH and MH increased the precipitation over North China, whereas an intensified WPSH and the weakened MH increased the precipitation over South China during the decay stage. The 11-year and 23-year variabilities contribute differently to the precipitation variations in the different regions of China, as seen in the 1998 flooding case. The 11-year cycle mainly accounts for precipitation increases over the Yangtze River Basin, while the 23-year cycle is responsible for the precipitation increase over Northeast China. These results have important implications for understanding how the PDO modulates the precipitation distribution over China, helping to improve interdecadal climate prediction.
2024, 41(1): 73-83.
doi: 10.1007/s00376-023-3025-6
Abstract:
An extreme torrential rain (ETR) event occurred in Henan Province, China, during 18-21 July 2021. Based on hourly rain-gauge observations and ERA5 reanalysis data, the ETR was studied from the perspective of kinetic energy (K), which can be divided into rotational wind ( V R) kinetic energy (KR), divergent wind kinetic energy (KD), and the kinetic energy of the interaction between the divergent and rotational winds (KRD). According to the hourly precipitation intensity variability, the ETR process was divided into an initial stage, a rapid increase stage, and maintenance stage. Results showed that the intensification and maintenance of ETR were closely related to the upper-level K, and most closely related to the upper-level KR, with a correlation coefficient of up to 0.9. In particular, the peak value of hourly rainfall intensity lagged behind the KR by 8 h. Furthermore, diagnosis showed that K transformation from unresolvable to resolvable scales made the ETR increase slowly. The meridional rotational wind (uR) and meridional gradient of the geopotential (φ) jointly determined the conversion of available potential energy (APE) to KR through the barotropic process, which dominated the rapid enhancement of KR and then caused the rapid increase in ETR. The transportation of K by rotational wind consumed KR, and basically offset the KR produced by the barotropic process, which basically kept KR stable at a high value, thus maintaining the ETR.
An extreme torrential rain (ETR) event occurred in Henan Province, China, during 18-21 July 2021. Based on hourly rain-gauge observations and ERA5 reanalysis data, the ETR was studied from the perspective of kinetic energy (K), which can be divided into rotational wind ( V R) kinetic energy (KR), divergent wind kinetic energy (KD), and the kinetic energy of the interaction between the divergent and rotational winds (KRD). According to the hourly precipitation intensity variability, the ETR process was divided into an initial stage, a rapid increase stage, and maintenance stage. Results showed that the intensification and maintenance of ETR were closely related to the upper-level K, and most closely related to the upper-level KR, with a correlation coefficient of up to 0.9. In particular, the peak value of hourly rainfall intensity lagged behind the KR by 8 h. Furthermore, diagnosis showed that K transformation from unresolvable to resolvable scales made the ETR increase slowly. The meridional rotational wind (uR) and meridional gradient of the geopotential (φ) jointly determined the conversion of available potential energy (APE) to KR through the barotropic process, which dominated the rapid enhancement of KR and then caused the rapid increase in ETR. The transportation of K by rotational wind consumed KR, and basically offset the KR produced by the barotropic process, which basically kept KR stable at a high value, thus maintaining the ETR.
2024, 41(1): 84-96.
doi: 10.1007/s00376-023-2329-x
Abstract:
The pan-Arctic is confronted with air pollution transported from lower latitudes. Observations have shown that aerosols help increase plant photosynthesis through the diffuse radiation fertilization effects (DRFEs). While such DRFEs have been explored at low to middle latitudes, the aerosol impacts on pan-Arctic ecosystems and the contributions by anthropogenic and natural emission sources remain less quantified. Here, we perform regional simulations at 0.2º×0.2º using a well-validated vegetation model (Yale Interactive terrestrial Biosphere, YIBs) in combination with multi-source of observations to quantify the impacts of aerosol DRFEs on the net primary productivity (NPP) in the pan-Arctic during 2001–19. Results show that aerosol DRFEs increase pan-Arctic NPP by 2.19 Pg C (12.8%) yr−1 under clear-sky conditions, in which natural and anthropogenic sources contribute to 8.9% and 3.9%, respectively. Under all-sky conditions, such DRFEs are largely dampened by cloud to only 0.26 Pg C (1.24%) yr−1, with contributions of 0.65% by natural and 0.59% by anthropogenic species. Natural aerosols cause a positive NPP trend of 0.022% yr−1 following the increased fire activities in the pan-Arctic. In contrast, anthropogenic aerosols induce a negative trend of −0.01% yr−1 due to reduced emissions from the middle latitudes. Such trends in aerosol DRFEs show a turning point in the year of 2007 with more positive NPP trends by natural aerosols but negative NPP trends by anthropogenic aerosols thereafter. Though affected by modeling uncertainties, this study suggests a likely increasing impact of aerosols on terrestrial ecosystems in the pan-Arctic under global warming.
The pan-Arctic is confronted with air pollution transported from lower latitudes. Observations have shown that aerosols help increase plant photosynthesis through the diffuse radiation fertilization effects (DRFEs). While such DRFEs have been explored at low to middle latitudes, the aerosol impacts on pan-Arctic ecosystems and the contributions by anthropogenic and natural emission sources remain less quantified. Here, we perform regional simulations at 0.2º×0.2º using a well-validated vegetation model (Yale Interactive terrestrial Biosphere, YIBs) in combination with multi-source of observations to quantify the impacts of aerosol DRFEs on the net primary productivity (NPP) in the pan-Arctic during 2001–19. Results show that aerosol DRFEs increase pan-Arctic NPP by 2.19 Pg C (12.8%) yr−1 under clear-sky conditions, in which natural and anthropogenic sources contribute to 8.9% and 3.9%, respectively. Under all-sky conditions, such DRFEs are largely dampened by cloud to only 0.26 Pg C (1.24%) yr−1, with contributions of 0.65% by natural and 0.59% by anthropogenic species. Natural aerosols cause a positive NPP trend of 0.022% yr−1 following the increased fire activities in the pan-Arctic. In contrast, anthropogenic aerosols induce a negative trend of −0.01% yr−1 due to reduced emissions from the middle latitudes. Such trends in aerosol DRFEs show a turning point in the year of 2007 with more positive NPP trends by natural aerosols but negative NPP trends by anthropogenic aerosols thereafter. Though affected by modeling uncertainties, this study suggests a likely increasing impact of aerosols on terrestrial ecosystems in the pan-Arctic under global warming.
2024, 41(1): 97-114.
doi: 10.1007/s00376-023-2303-7
Abstract:
Three cases of microphysical characteristics and kinematic structures in the negative temperature region of summer mesoscale cloud systems over the eastern Tibetan Plateau (TP) were investigated using X-band dual-polarization radar. The time–height series of radar physical variables and mesoscale horizontal divergence\begin{document}$ \bar{\delta } $\end{document} ![]()
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Three cases of microphysical characteristics and kinematic structures in the negative temperature region of summer mesoscale cloud systems over the eastern Tibetan Plateau (TP) were investigated using X-band dual-polarization radar. The time–height series of radar physical variables and mesoscale horizontal divergence
Uncertainties of ENSO-related Regional Hadley Circulation Anomalies within Eight Reanalysis Datasets
2024, 41(1): 115-140.
doi: 10.1007/s00376-023-3047-0
Abstract:
El Niño–Southern Oscillation (ENSO), the leading mode of global interannual variability, usually intensifies the Hadley Circulation (HC), and meanwhile constrains its meridional extension, leading to an equatorward movement of the jet system. Previous studies have investigated the response of HC to ENSO events using different reanalysis datasets and evaluated their capability in capturing the main features of ENSO-associated HC anomalies. However, these studies mainly focused on the global HC, represented by a zonal-mean mass stream function (MSF). Comparatively fewer studies have evaluated HC responses from a regional perspective, partly due to the prerequisite of the Stokes MSF, which prevents us from integrating a regional HC. In this study, we adopt a recently developed technique to construct the three-dimensional structure of HC and evaluate the capability of eight state-of-the-art reanalyses in reproducing the regional HC response to ENSO events. Results show that all eight reanalyses reproduce the spatial structure of HC responses well, with an intensified HC around the central-eastern Pacific but weakened circulations around the Indo-Pacific warm pool and tropical Atlantic. The spatial correlation coefficient of the three-dimensional HC anomalies among the different datasets is always larger than 0.93. However, these datasets may not capture the amplitudes of the HC responses well. This uncertainty is especially large for ENSO-associated equatorially asymmetric HC anomalies, with the maximum amplitude in Climate Forecast System Reanalysis (CFSR) being about 2.7 times the minimum value in the Twentieth Century Reanalysis (20CR). One should be careful when using reanalysis data to evaluate the intensity of ENSO-associated HC anomalies.
El Niño–Southern Oscillation (ENSO), the leading mode of global interannual variability, usually intensifies the Hadley Circulation (HC), and meanwhile constrains its meridional extension, leading to an equatorward movement of the jet system. Previous studies have investigated the response of HC to ENSO events using different reanalysis datasets and evaluated their capability in capturing the main features of ENSO-associated HC anomalies. However, these studies mainly focused on the global HC, represented by a zonal-mean mass stream function (MSF). Comparatively fewer studies have evaluated HC responses from a regional perspective, partly due to the prerequisite of the Stokes MSF, which prevents us from integrating a regional HC. In this study, we adopt a recently developed technique to construct the three-dimensional structure of HC and evaluate the capability of eight state-of-the-art reanalyses in reproducing the regional HC response to ENSO events. Results show that all eight reanalyses reproduce the spatial structure of HC responses well, with an intensified HC around the central-eastern Pacific but weakened circulations around the Indo-Pacific warm pool and tropical Atlantic. The spatial correlation coefficient of the three-dimensional HC anomalies among the different datasets is always larger than 0.93. However, these datasets may not capture the amplitudes of the HC responses well. This uncertainty is especially large for ENSO-associated equatorially asymmetric HC anomalies, with the maximum amplitude in Climate Forecast System Reanalysis (CFSR) being about 2.7 times the minimum value in the Twentieth Century Reanalysis (20CR). One should be careful when using reanalysis data to evaluate the intensity of ENSO-associated HC anomalies.
2024, 41(1): 141-154.
doi: 10.1007/s00376-023-3001-1
Abstract:
The application of deep learning is fast developing in climate prediction, in which El Niño–Southern Oscillation (ENSO), as the most dominant disaster-causing climate event, is a key target. Previous studies have shown that deep learning methods possess a certain level of superiority in predicting ENSO indices. The present study develops a deep learning model for predicting the spatial pattern of sea surface temperature anomalies (SSTAs) in the equatorial Pacific by training a convolutional neural network (CNN) model with historical simulations from CMIP6 models. Compared with dynamical models, the CNN model has higher skill in predicting the SSTAs in the equatorial western-central Pacific, but not in the eastern Pacific. The CNN model can successfully capture the small-scale precursors in the initial SSTAs for the development of central Pacific ENSO to distinguish the spatial mode up to a lead time of seven months. A fusion model combining the predictions of the CNN model and the dynamical models achieves higher skill than each of them for both central and eastern Pacific ENSO.
The application of deep learning is fast developing in climate prediction, in which El Niño–Southern Oscillation (ENSO), as the most dominant disaster-causing climate event, is a key target. Previous studies have shown that deep learning methods possess a certain level of superiority in predicting ENSO indices. The present study develops a deep learning model for predicting the spatial pattern of sea surface temperature anomalies (SSTAs) in the equatorial Pacific by training a convolutional neural network (CNN) model with historical simulations from CMIP6 models. Compared with dynamical models, the CNN model has higher skill in predicting the SSTAs in the equatorial western-central Pacific, but not in the eastern Pacific. The CNN model can successfully capture the small-scale precursors in the initial SSTAs for the development of central Pacific ENSO to distinguish the spatial mode up to a lead time of seven months. A fusion model combining the predictions of the CNN model and the dynamical models achieves higher skill than each of them for both central and eastern Pacific ENSO.
2024, 41(1): 155-172.
doi: 10.1007/s00376-023-2275-7
Abstract:
Existing studies contend that latent heating (LH) will replace sensible heating (SH) to become the dominant factor affecting the development of the Tibetan Plateau vortex (TPV) after it moves off the Tibetan Plateau (TP). However, in the process of the TPV moving off the TP requires that the airmass traverse the eastern slope of the Tibetan Plateau (ESTP) where the topography and diabatic heating (DH) conditions rapidly change. How LH gradually replaces SH to become the dominant factor in the development of the TPV over the ESTP is still not very clear. In this paper, an analysis of a typical case of a TPV with a long life history over the ESTP is performed by using multi-sourced meteorological data and model simulations. The results show that SH from the TP surface can change the TPV-associated precipitation distribution by temperature advection after the TPV moves off the TP. The LH can then directly promote the development of the TPV and has a certain guiding effect on the track of the TPV. The SH can control the active area of LH by changing the falling area of the TPV-associated precipitation, so it still plays a key role in the development and tracking of the TPV even though it has moved out of the main body of the TP.
Existing studies contend that latent heating (LH) will replace sensible heating (SH) to become the dominant factor affecting the development of the Tibetan Plateau vortex (TPV) after it moves off the Tibetan Plateau (TP). However, in the process of the TPV moving off the TP requires that the airmass traverse the eastern slope of the Tibetan Plateau (ESTP) where the topography and diabatic heating (DH) conditions rapidly change. How LH gradually replaces SH to become the dominant factor in the development of the TPV over the ESTP is still not very clear. In this paper, an analysis of a typical case of a TPV with a long life history over the ESTP is performed by using multi-sourced meteorological data and model simulations. The results show that SH from the TP surface can change the TPV-associated precipitation distribution by temperature advection after the TPV moves off the TP. The LH can then directly promote the development of the TPV and has a certain guiding effect on the track of the TPV. The SH can control the active area of LH by changing the falling area of the TPV-associated precipitation, so it still plays a key role in the development and tracking of the TPV even though it has moved out of the main body of the TP.
2024, 41(1): 173-187.
doi: 10.1007/s00376-023-2357-6
Abstract:
The process of entrainment-mixing between cumulus clouds and the ambient air is important for the development of cumulus clouds. Accurately obtaining the entrainment rate (λ) is particularly important for its parameterization within the overall cumulus parameterization scheme. In this study, an improved bulk-plume method is proposed by solving the equations of two conserved variables simultaneously to calculate λ of cumulus clouds in a large-eddy simulation. The results demonstrate that the improved bulk-plume method is more reliable than the traditional bulk-plume method, because λ, as calculated from the improved method, falls within the range of λ values obtained from the traditional method using different conserved variables. The probability density functions of λ for all data, different times, and different heights can be well-fitted by a log-normal distribution, which supports the assumed stochastic entrainment process in previous studies. Further analysis demonstrate that the relationship between λ and the vertical velocity is better than other thermodynamic/dynamical properties; thus, the vertical velocity is recommended as the primary influencing factor for the parameterization of λ in the future. The results of this study enhance the theoretical understanding of λ and its influencing factors and shed new light on the development of λ parameterization.
The process of entrainment-mixing between cumulus clouds and the ambient air is important for the development of cumulus clouds. Accurately obtaining the entrainment rate (λ) is particularly important for its parameterization within the overall cumulus parameterization scheme. In this study, an improved bulk-plume method is proposed by solving the equations of two conserved variables simultaneously to calculate λ of cumulus clouds in a large-eddy simulation. The results demonstrate that the improved bulk-plume method is more reliable than the traditional bulk-plume method, because λ, as calculated from the improved method, falls within the range of λ values obtained from the traditional method using different conserved variables. The probability density functions of λ for all data, different times, and different heights can be well-fitted by a log-normal distribution, which supports the assumed stochastic entrainment process in previous studies. Further analysis demonstrate that the relationship between λ and the vertical velocity is better than other thermodynamic/dynamical properties; thus, the vertical velocity is recommended as the primary influencing factor for the parameterization of λ in the future. The results of this study enhance the theoretical understanding of λ and its influencing factors and shed new light on the development of λ parameterization.
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