Based on data of meteorological elements in the meteorological station in North Yandang Mountains during 1960- 2013,temporal variations in days of sea of clouds over Yandang Mountains in nearly 50 years and their rela...Based on data of meteorological elements in the meteorological station in North Yandang Mountains during 1960- 2013,temporal variations in days of sea of clouds over Yandang Mountains in nearly 50 years and their relation with air temperature,precipitation,relative humidity and wind speed were analyzed. The results showed that annual average days of sea of clouds over Yandang Mountains were 164. 92 d,and the maximum and minimum were 215 and 58 d,so there was a big difference between various years. The days of sea of clouds were the most in spring,and average days of sea of clouds（ average days of sea of clouds with low cloud cover ≥80%） were 50. 89 d（ 32. 77 d）,while they were the least in autumn. There was an obvious positive correlation between the days of sea of clouds and relative humidity. Precipitation occurred the day before or on the day when sea of clouds with low cloud cover ≥80% formed. On the day when sea of clouds with low cloud cover ≥80% appeared,average relative humidity was ≥80%,and average wind speed was ≤4. 5 m/s.展开更多
Based on data from satellite and surface observations,the horizontal and vertical distributions of clouds over eastern China and the East China Sea are examined.Three maximum centers of cloud cover are clearly visible...Based on data from satellite and surface observations,the horizontal and vertical distributions of clouds over eastern China and the East China Sea are examined.Three maximum centers of cloud cover are clearly visible in the horizontal distribution of total cloud cover.Two of these maxima occur over land.As the clouds mainly originate from the climbing airflows in the southern and eastern slopes of the Tibetan Plateau,they can be classified as dynamic clouds.The third center of cloud cover is over the sea.As the clouds mainly form from the evaporation of the warm Kuroshio Current,they can be categorized as thermodynamic clouds.Although the movement of the cloud centers reflect the seasonal variation of the Asian summer monsoon,cloud fractions of six cloud types that are distinct from the total cloud cover show individual horizontal patterns and seasonal variations.In their vertical distribution,cloud cover over the land and sea exhibits different patterns in winter but similar patterns in summer.In cold seasons,limited by divergent westerlies in the middle troposphere,mid-level clouds prevail over the leeside of the Tibetan Plateau.At the same time,suppressed by strong downdraft of the western Pacific subtropical high,low clouds dominate over the ocean.In warm seasons both continental and marine clouds can penetrate upward into the upper troposphere because they are subject to similar unstable stratification conditions.展开更多
Cloud structure and evolution of Mesoscale Convective Systems （MCSs） retrieved from the Tropical Rainfall Measuring Mission Microwave Imager （TRMM TMI） and Precipitation Radar （PR） were investigated and compared...Cloud structure and evolution of Mesoscale Convective Systems （MCSs） retrieved from the Tropical Rainfall Measuring Mission Microwave Imager （TRMM TMI） and Precipitation Radar （PR） were investigated and compared with some pioneer studies based on soundings and models over the northern South China Sea （SCS）. The impacts of Convective Available Potential Energy （CAPE） and environmental vertical wind shear on MCSs were also explored. The main features of MCSs over the SCS were captured well by both TRMM PR and TMI. However, the PR-retrieved surface rainfall in May was less than that in June, and the reverse for TMI. TRMM-retrieved rainfall amounts were generally consistent with those estimated from sounding and models. However, rainfall amounts from sounding-based and PR-based estimates were relatively higher than those retrieved from TRMM-TMI data. The Weather Research and Forecasting （WRF） modeling simulation underestimated the maximum rain rate by 22% compared to that derived from TRMM-PR, and underestimated mean rainfall by 10.4% compared to the TRMM-TMI estimate, and by 12.5% compared to the sounding-based estimate. The warm microphysical processes modeled from both the WRF and the Goddard Cumulus Ensemble （GCE） models were quite close to those based on TMI, but the ice water contents in the models were relatively less compared to that derived from TMI. The CAPE and wind shear induced by the monsoon circulation were found to play critical roles in maintaining and developing the intense convective clouds over SCS. The latent heating rate increased more than twofold during the monsoon period and provided favorable conditions for the upward transportation of energy from the ocean, giving rise to the possibility of inducing large-scale interactions.展开更多
The effects of clouds, sea surface temperature, and its diurnal variation on precipitation efficiency are investigated us ing grid-scale data from nine equilibrium sensitivity cloud-resolving model experiments driven ...The effects of clouds, sea surface temperature, and its diurnal variation on precipitation efficiency are investigated us ing grid-scale data from nine equilibrium sensitivity cloud-resolving model experiments driven without large-scale vertical velocity. The precipitation efficiencies are respectively defined in surface rainfall, cloud, and rain microphysical budgets. We mathematically and physically demonstrate the relationship between these precipitation efficiencies. The 2 ℃ increases in spatiotemporal invariant sea surface temperature （SST） from 27 ℃ to 29 ℃ and from 29 ℃ to 31 ℃, and the inclusion of diurnal SST difference 1 ℃ and the 1℃ increase in diurnal SST difference generate opposite changes in the precipitation efficiency by changing ice cloud-radiation interactions. The radiative and microphysical processes of ice clouds have opposite effects on the precipitation efficiency because of the rainfall increase associated with the reduction in the saturation mixing ratio caused by the exclusion of radiative effects and the decrease in rainfall related to the reduction in net condensation caused by the exclusion of deposition processes. The radiative effects of water clouds on the precipitation efficiency are statistically insensitive to the radiative effects of ice clouds.展开更多
This study of the general features of occurrence frequencies, spatial distribution of locations, life time and cloud patterns of polar lows over the Japan Sea and the neighboring Northwestern Pacific in winter of 1995...This study of the general features of occurrence frequencies, spatial distribution of locations, life time and cloud patterns of polar lows over the Japan Sea and the neighboring Northwestern Pacific in winter of 1995/1996 based on observation and satellite data showed that polar lows develop most frequently in mid winter over the Japan Sea (35-45°N ) and the Northwestern Pacific (30-50°N). They rarely form over the Eurasian Continent. Polar lows over the Northwestern Pacific are usually long lived (2-3 days). But polar lows over the Japan Sea are relatively short lived (1-2 days), because the east west width of the Japan Sea is relatively narrow and polar lows tend to decay after their passing over the Japan Islands. Generally speaking, polar lows over the Japan Sea are characterized by tight, spiral (or comma) cloud patterns on satellite images. It was observed that polar lows over the Japan Sea have a typically spiral cloud band with clear “eye” at their mature stage. In winter, because of the effect of the warm Tsushima Current, the annual mean SST of the Japan Sea is 5-9℃ higher than that of the same latitude oceans. The large sea air temperature difference sustained over the Japan Sea provides favorable condition for polar low formation. The general features of polar lows over the Japan Sea are compared with those of other areas where polar lows often occur.展开更多
The main objective of this study is to examine the NARR (North American Regional Reanalysis Model) high-resolution dataset to understand the last two decades dramatic climate changes in Hudson Bay associated with the ...The main objective of this study is to examine the NARR (North American Regional Reanalysis Model) high-resolution dataset to understand the last two decades dramatic climate changes in Hudson Bay associated with the atmospheric keys by synoptically analysis. The anomalies of the near-surface meteorological parameters such as air temperature, humidity, mean sea level pressure, wind vectors along with cloudiness, precipitation, surface albedo and downward longwave radiation at surface in seasonally based changes have been analysed. The increase in low-level thermal structure leads to changing the near-surface humidity, evaporation, cloudiness, precipitation and downward longwave radiation at the surface. Also, winds have been accelerated associated with anticyclonic curvature development. The results show significant atmospheric changes during the last two decades in Hudson Bay with the highest values mostly during winter and fall seasons in the north, east boundaries and James Bay area. Using the statistical analysis for mean low-level temperature, surface albedo, low-level clouds and evaporation at the surface during nearly recent 2 decades (1998-2018) rather than the normal climatology mean (1981-2010) have revealed the meaningful significant difference for mentioned parameters. The statistical analysis results show that during spring there is a significant positive correlation between low clouds anomaly and 2 m air temperature anomaly rather than other seasons. So, the recent atmospheric changes in the study area as a region located in the Arctic and sub-Arctic can contribute to extra-local and global warming.展开更多
Raindrop size distribution (RSD) characteristics over the South China Sea (SCS) are examined with onboard Parsivel disdrometer measurements collected during marine surveys from 2012 to 2016. The observed rainfall is d...Raindrop size distribution (RSD) characteristics over the South China Sea (SCS) are examined with onboard Parsivel disdrometer measurements collected during marine surveys from 2012 to 2016. The observed rainfall is divided into premonsoon, monsoon, and post-monsoon periods based on the different large-scale circumstances. In addition to disdrometer data, sounding observation, FY-2E satellite, SPRINTARS (Spectral Radiation-Transport Model for Aerosol Species), and NCEP reanalysis datasets are used to illustrate the dynamical and microphysical characteristics associated with the rainfall in different periods. Significant variations have been observed in respect of raindrops among the three periods. Intercomparison reveals that small drops (D < 1 mm) are prevalent during pre-monsoon precipitation, whereas medium drops (1?3 mm) are predominant in monsoon precipitation. Overall, the post-monsoon precipitation is characterized by the least concentration of raindrops among the three periods. But, several large raindrops could also occur due to severe convective precipitation events in this period. Classification of the precipitation into stratiform and convective regimes shows that the lg(Nw) value of convective rainfall is the largest (smallest) in the pre-monsoon (post-monsoon) period, whereas the Dm value is the smallest (largest) in the pre-monsoon (post-monsoon) period. An inversion relationship between the coefficient A and the exponential b of the Z?R relationships for precipitation during the three periods is found. Empirical relations between Dm and the radar reflectivity factors at Ku and Ka bands are also derived to improve the rainfall retrieval algorithms over the SCS. Furthermore, the possible causative mechanisms for the significant RSD variability in different periods are also discussed with respect to warm and cold rain processes, raindrop evaporation, convective activities, and other meteorological factors.展开更多
Reviews on the current studies on the sea to air flux of dimethyl sulfide (DMS) have been made at home and abroad, pointing out that the flux of DMS is influenced by many factors. There is great difference between the...Reviews on the current studies on the sea to air flux of dimethyl sulfide (DMS) have been made at home and abroad, pointing out that the flux of DMS is influenced by many factors. There is great difference between the results coming from different models. Besides, this paper focuses on the oxidation mechanisms of DMS by OH and NO3 radicals after it enters the atmosphere, the oxidation products’ contribution to acid rain and fog and the relationships among the DMS, CCN and climate system.展开更多
The sensitivity of precipitation to sea surface temperature(SST) and its diurnal variation is investigated through a rainfall partitioning analysis of two-dimensional cloud-resolving model experiments based on surface...The sensitivity of precipitation to sea surface temperature(SST) and its diurnal variation is investigated through a rainfall partitioning analysis of two-dimensional cloud-resolving model experiments based on surface rainfall budget.For all experiments,the model is set up using zero vertical velocity and a constant zonal wind and is integrated over 40 days to reach quasi-equilibrium states.The 10-day equilibrium grid-scale simulation data and a time-invariant SST of 29°C are used in the control experiment.In the sensitivity experiments,time-invariant SSTs are 27°C and 31°C with an average value of 29°C when the minimum and maximum values of diurnal SST differences are 1°C and 2°C,respectively.The results show that the largest contribution to total rainfall is from the rainfall with water vapor convergence and local atmospheric drying and hydrometeor gain/divergence(~30%) in all experiments.When SST increases from 27°C to 29°C,the contribution from water vapor convergence decreases.The increase of SST reduces the contribution of the rainfall with water vapor convergence primarily through the decreased contribution of the rainfall with local atmospheric drying and hydrometeor gain/divergence and the rainfall with local atmospheric moistening and hydrometeor loss/convergence.The inclusion of diurnal variation of SST with the diurnal difference of 1°C decreases the rainfall contribution from water vapor convergence primarily through the decreased contribution of the rainfall with local atmospheric moistening and hydrometeor loss/convergence.The contribution of the rainfall from water vapor convergence is barely changed as the diurnal difference of SST increases from 1°C to 2°C.展开更多
基金Supported by the Key Project of Zhejiang Meteorological Bureau(2013ZD08)
文摘Based on data of meteorological elements in the meteorological station in North Yandang Mountains during 1960- 2013,temporal variations in days of sea of clouds over Yandang Mountains in nearly 50 years and their relation with air temperature,precipitation,relative humidity and wind speed were analyzed. The results showed that annual average days of sea of clouds over Yandang Mountains were 164. 92 d,and the maximum and minimum were 215 and 58 d,so there was a big difference between various years. The days of sea of clouds were the most in spring,and average days of sea of clouds（ average days of sea of clouds with low cloud cover ≥80%） were 50. 89 d（ 32. 77 d）,while they were the least in autumn. There was an obvious positive correlation between the days of sea of clouds and relative humidity. Precipitation occurred the day before or on the day when sea of clouds with low cloud cover ≥80% formed. On the day when sea of clouds with low cloud cover ≥80% appeared,average relative humidity was ≥80%,and average wind speed was ≤4. 5 m/s.
基金National Basic Research Program of China (973 Program) (2010CB951904)National Natural Science Foundation of China (41075034)
文摘Based on data from satellite and surface observations,the horizontal and vertical distributions of clouds over eastern China and the East China Sea are examined.Three maximum centers of cloud cover are clearly visible in the horizontal distribution of total cloud cover.Two of these maxima occur over land.As the clouds mainly originate from the climbing airflows in the southern and eastern slopes of the Tibetan Plateau,they can be classified as dynamic clouds.The third center of cloud cover is over the sea.As the clouds mainly form from the evaporation of the warm Kuroshio Current,they can be categorized as thermodynamic clouds.Although the movement of the cloud centers reflect the seasonal variation of the Asian summer monsoon,cloud fractions of six cloud types that are distinct from the total cloud cover show individual horizontal patterns and seasonal variations.In their vertical distribution,cloud cover over the land and sea exhibits different patterns in winter but similar patterns in summer.In cold seasons,limited by divergent westerlies in the middle troposphere,mid-level clouds prevail over the leeside of the Tibetan Plateau.At the same time,suppressed by strong downdraft of the western Pacific subtropical high,low clouds dominate over the ocean.In warm seasons both continental and marine clouds can penetrate upward into the upper troposphere because they are subject to similar unstable stratification conditions.
基金sponsored by the Chinese Natural Science Foundation (Grant Nos. 40575003 and 40333033)the special foundation of the Chinese Academy of Meteorological Sciences (2011Z005)
文摘Cloud structure and evolution of Mesoscale Convective Systems （MCSs） retrieved from the Tropical Rainfall Measuring Mission Microwave Imager （TRMM TMI） and Precipitation Radar （PR） were investigated and compared with some pioneer studies based on soundings and models over the northern South China Sea （SCS）. The impacts of Convective Available Potential Energy （CAPE） and environmental vertical wind shear on MCSs were also explored. The main features of MCSs over the SCS were captured well by both TRMM PR and TMI. However, the PR-retrieved surface rainfall in May was less than that in June, and the reverse for TMI. TRMM-retrieved rainfall amounts were generally consistent with those estimated from sounding and models. However, rainfall amounts from sounding-based and PR-based estimates were relatively higher than those retrieved from TRMM-TMI data. The Weather Research and Forecasting （WRF） modeling simulation underestimated the maximum rain rate by 22% compared to that derived from TRMM-PR, and underestimated mean rainfall by 10.4% compared to the TRMM-TMI estimate, and by 12.5% compared to the sounding-based estimate. The warm microphysical processes modeled from both the WRF and the Goddard Cumulus Ensemble （GCE） models were quite close to those based on TMI, but the ice water contents in the models were relatively less compared to that derived from TMI. The CAPE and wind shear induced by the monsoon circulation were found to play critical roles in maintaining and developing the intense convective clouds over SCS. The latent heating rate increased more than twofold during the monsoon period and provided favorable conditions for the upward transportation of energy from the ocean, giving rise to the possibility of inducing large-scale interactions.
基金supported by the National Basic Research Program of China (Grant Nos. 2013CB430103 and 2011CB403405)the National Natural Science Foundation of China (Grant Nos. 41075039 and 41175065)the Priority Academic Program Development of Jiangsu Higher Education Institutions, China (Grant No. PAPD2011)
文摘The effects of clouds, sea surface temperature, and its diurnal variation on precipitation efficiency are investigated us ing grid-scale data from nine equilibrium sensitivity cloud-resolving model experiments driven without large-scale vertical velocity. The precipitation efficiencies are respectively defined in surface rainfall, cloud, and rain microphysical budgets. We mathematically and physically demonstrate the relationship between these precipitation efficiencies. The 2 ℃ increases in spatiotemporal invariant sea surface temperature （SST） from 27 ℃ to 29 ℃ and from 29 ℃ to 31 ℃, and the inclusion of diurnal SST difference 1 ℃ and the 1℃ increase in diurnal SST difference generate opposite changes in the precipitation efficiency by changing ice cloud-radiation interactions. The radiative and microphysical processes of ice clouds have opposite effects on the precipitation efficiency because of the rainfall increase associated with the reduction in the saturation mixing ratio caused by the exclusion of radiative effects and the decrease in rainfall related to the reduction in net condensation caused by the exclusion of deposition processes. The radiative effects of water clouds on the precipitation efficiency are statistically insensitive to the radiative effects of ice clouds.
文摘This study of the general features of occurrence frequencies, spatial distribution of locations, life time and cloud patterns of polar lows over the Japan Sea and the neighboring Northwestern Pacific in winter of 1995/1996 based on observation and satellite data showed that polar lows develop most frequently in mid winter over the Japan Sea (35-45°N ) and the Northwestern Pacific (30-50°N). They rarely form over the Eurasian Continent. Polar lows over the Northwestern Pacific are usually long lived (2-3 days). But polar lows over the Japan Sea are relatively short lived (1-2 days), because the east west width of the Japan Sea is relatively narrow and polar lows tend to decay after their passing over the Japan Islands. Generally speaking, polar lows over the Japan Sea are characterized by tight, spiral (or comma) cloud patterns on satellite images. It was observed that polar lows over the Japan Sea have a typically spiral cloud band with clear “eye” at their mature stage. In winter, because of the effect of the warm Tsushima Current, the annual mean SST of the Japan Sea is 5-9℃ higher than that of the same latitude oceans. The large sea air temperature difference sustained over the Japan Sea provides favorable condition for polar low formation. The general features of polar lows over the Japan Sea are compared with those of other areas where polar lows often occur.
文摘The main objective of this study is to examine the NARR (North American Regional Reanalysis Model) high-resolution dataset to understand the last two decades dramatic climate changes in Hudson Bay associated with the atmospheric keys by synoptically analysis. The anomalies of the near-surface meteorological parameters such as air temperature, humidity, mean sea level pressure, wind vectors along with cloudiness, precipitation, surface albedo and downward longwave radiation at surface in seasonally based changes have been analysed. The increase in low-level thermal structure leads to changing the near-surface humidity, evaporation, cloudiness, precipitation and downward longwave radiation at the surface. Also, winds have been accelerated associated with anticyclonic curvature development. The results show significant atmospheric changes during the last two decades in Hudson Bay with the highest values mostly during winter and fall seasons in the north, east boundaries and James Bay area. Using the statistical analysis for mean low-level temperature, surface albedo, low-level clouds and evaporation at the surface during nearly recent 2 decades (1998-2018) rather than the normal climatology mean (1981-2010) have revealed the meaningful significant difference for mentioned parameters. The statistical analysis results show that during spring there is a significant positive correlation between low clouds anomaly and 2 m air temperature anomaly rather than other seasons. So, the recent atmospheric changes in the study area as a region located in the Arctic and sub-Arctic can contribute to extra-local and global warming.
基金primarily supported by the Chinese Beijige Open Research Fund for the Nanjing Joint Center of Atmospheric Research (Grant No. NJCAR 2018ZD03)the National Key Research and Development Program of China (2018YFC1507304)the National Natural Science Foundation of China (Grant Nos. 41575024 and 41865009)
文摘Raindrop size distribution (RSD) characteristics over the South China Sea (SCS) are examined with onboard Parsivel disdrometer measurements collected during marine surveys from 2012 to 2016. The observed rainfall is divided into premonsoon, monsoon, and post-monsoon periods based on the different large-scale circumstances. In addition to disdrometer data, sounding observation, FY-2E satellite, SPRINTARS (Spectral Radiation-Transport Model for Aerosol Species), and NCEP reanalysis datasets are used to illustrate the dynamical and microphysical characteristics associated with the rainfall in different periods. Significant variations have been observed in respect of raindrops among the three periods. Intercomparison reveals that small drops (D < 1 mm) are prevalent during pre-monsoon precipitation, whereas medium drops (1?3 mm) are predominant in monsoon precipitation. Overall, the post-monsoon precipitation is characterized by the least concentration of raindrops among the three periods. But, several large raindrops could also occur due to severe convective precipitation events in this period. Classification of the precipitation into stratiform and convective regimes shows that the lg(Nw) value of convective rainfall is the largest (smallest) in the pre-monsoon (post-monsoon) period, whereas the Dm value is the smallest (largest) in the pre-monsoon (post-monsoon) period. An inversion relationship between the coefficient A and the exponential b of the Z?R relationships for precipitation during the three periods is found. Empirical relations between Dm and the radar reflectivity factors at Ku and Ka bands are also derived to improve the rainfall retrieval algorithms over the SCS. Furthermore, the possible causative mechanisms for the significant RSD variability in different periods are also discussed with respect to warm and cold rain processes, raindrop evaporation, convective activities, and other meteorological factors.
文摘Reviews on the current studies on the sea to air flux of dimethyl sulfide (DMS) have been made at home and abroad, pointing out that the flux of DMS is influenced by many factors. There is great difference between the results coming from different models. Besides, this paper focuses on the oxidation mechanisms of DMS by OH and NO3 radicals after it enters the atmosphere, the oxidation products’ contribution to acid rain and fog and the relationships among the DMS, CCN and climate system.
基金State Key Development Program for Basic Research of China (2009CB421505)Projects of the Natural Science Foundation of China (4107504441075079)
文摘The sensitivity of precipitation to sea surface temperature(SST) and its diurnal variation is investigated through a rainfall partitioning analysis of two-dimensional cloud-resolving model experiments based on surface rainfall budget.For all experiments,the model is set up using zero vertical velocity and a constant zonal wind and is integrated over 40 days to reach quasi-equilibrium states.The 10-day equilibrium grid-scale simulation data and a time-invariant SST of 29°C are used in the control experiment.In the sensitivity experiments,time-invariant SSTs are 27°C and 31°C with an average value of 29°C when the minimum and maximum values of diurnal SST differences are 1°C and 2°C,respectively.The results show that the largest contribution to total rainfall is from the rainfall with water vapor convergence and local atmospheric drying and hydrometeor gain/divergence(~30%) in all experiments.When SST increases from 27°C to 29°C,the contribution from water vapor convergence decreases.The increase of SST reduces the contribution of the rainfall with water vapor convergence primarily through the decreased contribution of the rainfall with local atmospheric drying and hydrometeor gain/divergence and the rainfall with local atmospheric moistening and hydrometeor loss/convergence.The inclusion of diurnal variation of SST with the diurnal difference of 1°C decreases the rainfall contribution from water vapor convergence primarily through the decreased contribution of the rainfall with local atmospheric moistening and hydrometeor loss/convergence.The contribution of the rainfall from water vapor convergence is barely changed as the diurnal difference of SST increases from 1°C to 2°C.
