2012 Vol. 18, No. 1
2012, 18(1): 1-10.
Abstract:
This paper presents a study on the temporal and spatial variations of the precipitation over the area of the South China Sea (SCS) during the monsoon onset period. The data used are from the Tropical Rainfall Measuring Mission (TRMM) observations between April and June over the nine years from 1998 to 2006. This study focuses on the central and northern part of South China Sea (110-120°E, 10-20°N). Based on the observations, the 27th pentad is selected as the occurrence time of the SCS monsoon onset. The conclusions are as follows. (1) After the monsoon onset, the specific area, defined as the ratio of the number of pixels with certain type of precipitation to the number of total pixels, extends significantly for both convective and stratiform rain, with the latter having a larger magnitude. The specific rainfall, defined as the ratio of the amount of certain type of precipitation to the total amount of precipitation, decreases for convective rain and increases for stratiform rain. (2) Results also show significant increase in heavy rain and decrease in light rain after the monsoon onset. (3) Changes are also observed in the rainfall horizontal distributions over the SCS before and after the monsoon onset, manifested by the relocation of precipitation minima for both convective and stratiform rain. (4) After the monsoon onset, the variability in characteristics of precipitation vertical structure increases significantly, leading to more latent heat release and consequently deeper convection. Meanwhile, the bright-band altitude of stratiform precipitation is also elevated.
This paper presents a study on the temporal and spatial variations of the precipitation over the area of the South China Sea (SCS) during the monsoon onset period. The data used are from the Tropical Rainfall Measuring Mission (TRMM) observations between April and June over the nine years from 1998 to 2006. This study focuses on the central and northern part of South China Sea (110-120°E, 10-20°N). Based on the observations, the 27th pentad is selected as the occurrence time of the SCS monsoon onset. The conclusions are as follows. (1) After the monsoon onset, the specific area, defined as the ratio of the number of pixels with certain type of precipitation to the number of total pixels, extends significantly for both convective and stratiform rain, with the latter having a larger magnitude. The specific rainfall, defined as the ratio of the amount of certain type of precipitation to the total amount of precipitation, decreases for convective rain and increases for stratiform rain. (2) Results also show significant increase in heavy rain and decrease in light rain after the monsoon onset. (3) Changes are also observed in the rainfall horizontal distributions over the SCS before and after the monsoon onset, manifested by the relocation of precipitation minima for both convective and stratiform rain. (4) After the monsoon onset, the variability in characteristics of precipitation vertical structure increases significantly, leading to more latent heat release and consequently deeper convection. Meanwhile, the bright-band altitude of stratiform precipitation is also elevated.
2012, 18(1): 11-20.
Abstract:
The influence of intraseasonal oscillation (ISO) on TC genesis over the northwestern Pacific is studied through comparing analyses of the more and less TC years from 1979 to 2006. It is indicated that the ISO strongly affects the TC genesis. In the years for more TC genesis, the ISO is weak and propagates insignificantly in the area to the west of the Philippines, but the ISO is strong in the area to the east of the Philippines and propagates significantly northwestward. In this situation, the Walker cell shifts gradually westward from the tropical western Pacific to the tropical eastern Indian Ocean. Convergent winds appear in the lower atmosphere while divergent winds in the upper atmosphere, suggesting the presence of enhanced ascending flow over the 140-160°E region and a favorable condition for TC genesis. Moreover, in the years for less TC genesis, the ISO gradually becomes stronger in the area to the west of the Philippines and significant eastward propagation prevails from the eastern Indian Ocean to the area around 120°E; the ISO is weak in the area to the east of the Philippines. During these years, the Walker circulation gradually moved eastward, with convergent winds in the upper troposphere and divergent winds in the lower troposphere. Sinking motion was significant, unfavorable for the TC genesis over the Northwestern Pacific.
The influence of intraseasonal oscillation (ISO) on TC genesis over the northwestern Pacific is studied through comparing analyses of the more and less TC years from 1979 to 2006. It is indicated that the ISO strongly affects the TC genesis. In the years for more TC genesis, the ISO is weak and propagates insignificantly in the area to the west of the Philippines, but the ISO is strong in the area to the east of the Philippines and propagates significantly northwestward. In this situation, the Walker cell shifts gradually westward from the tropical western Pacific to the tropical eastern Indian Ocean. Convergent winds appear in the lower atmosphere while divergent winds in the upper atmosphere, suggesting the presence of enhanced ascending flow over the 140-160°E region and a favorable condition for TC genesis. Moreover, in the years for less TC genesis, the ISO gradually becomes stronger in the area to the west of the Philippines and significant eastward propagation prevails from the eastern Indian Ocean to the area around 120°E; the ISO is weak in the area to the east of the Philippines. During these years, the Walker circulation gradually moved eastward, with convergent winds in the upper troposphere and divergent winds in the lower troposphere. Sinking motion was significant, unfavorable for the TC genesis over the Northwestern Pacific.
2012, 18(1): 21-31.
Abstract:
The multiple time scale climate changes are studied and calculated with statistical analysis and wavelet transformation on the basis of daily series of observed data over the period 1901-2007 in Macau. The result shows that statistically significant oscillations with 2 to 5 years of period generally exist in the series of climate variables (e.g. annual mean surface air temperature and precipitation as well as evaporation etc.), but with obvious locality in time domain. The variation of annual mean surface air temperature has a quasi 60-year period. The phases of the 60-year variation approximately and consistently match that of Atlantic Multidecadal Oscillation (AMO). The oscillations of seasonal mean surface air temperature in summer and winter have the periods of quasi 30-year and quasi 60-year, respectively. These two periods of oscillations have statistically significant correlation with Pacific decadal oscillation (PDO) and AMO, individually. The multidecadal variations of the precipitation of the annually first flood period and annual evaporation are dominated by periods of quasi 30-year and quasi 50-year, respectively.
The multiple time scale climate changes are studied and calculated with statistical analysis and wavelet transformation on the basis of daily series of observed data over the period 1901-2007 in Macau. The result shows that statistically significant oscillations with 2 to 5 years of period generally exist in the series of climate variables (e.g. annual mean surface air temperature and precipitation as well as evaporation etc.), but with obvious locality in time domain. The variation of annual mean surface air temperature has a quasi 60-year period. The phases of the 60-year variation approximately and consistently match that of Atlantic Multidecadal Oscillation (AMO). The oscillations of seasonal mean surface air temperature in summer and winter have the periods of quasi 30-year and quasi 60-year, respectively. These two periods of oscillations have statistically significant correlation with Pacific decadal oscillation (PDO) and AMO, individually. The multidecadal variations of the precipitation of the annually first flood period and annual evaporation are dominated by periods of quasi 30-year and quasi 50-year, respectively.
2012, 18(1): 32-44.
Abstract:
The first two series (RMM1 and RMM2) of RMM Index (all-Season Real-time Multivariate MJO Index) are computed to obtain the interannual variation of the preceding winter (preceding December to current February) MJO strength, according to which active (or inactive) years of preceding winter MJO are divided. By utilizing the data provided by NCEP/NCAR, CMAP and China's 160 stations from 1979 to 2008, we studied the preceding winter MJO strength and discovered that the summer precipitation in the basin are of significantly negative correlation, i.e. when the preceding winter MJO is relatively active, the summer precipitation in the basin decreases, and vise verse. We also analyzed the causes. When the preceding winter MJO is relatively active, its release of potential heat facilities Inter-Tropical Convergence Zone (ITCZ) to strengthen and locate northward in winter and propagate northeastward. This abnormal situation lasts from winter to summer. In mid-May, ITCZ jumps northward to the South China Sea, the western Pacific subtropical high withdraws eastward, and the South China Sea summer monsoon sets off and strengthens. In summer, ITCZ propagates to South China Sea-subtropical western Pacific, the zonal circulation of subtropical Pacific strengthens, and a local meridional circulation of the South China Sea to the basin area forms, giving rise to the East Asia Pacific teleconnection wave-train. An East Asian monsoon trough and the Meiyu front show opposite features from south to north, the East Asian summer monsoon strengthens and advances northward. As a result, the summer monsoon is weakened as the basin is controlled by the subtropical high continually, with less rain in summer. On the contrary, when the preceding winter MJO is inactive, ITCZ weakens and is located southward, the subtropical high is located southward in summer, and the basin is in a region of ascending airflow with prevailing southwest wind. The East Asian monsoon trough and EASM weaken so that summer monsoon is reduced in the basin where precipitation increases.
The first two series (RMM1 and RMM2) of RMM Index (all-Season Real-time Multivariate MJO Index) are computed to obtain the interannual variation of the preceding winter (preceding December to current February) MJO strength, according to which active (or inactive) years of preceding winter MJO are divided. By utilizing the data provided by NCEP/NCAR, CMAP and China's 160 stations from 1979 to 2008, we studied the preceding winter MJO strength and discovered that the summer precipitation in the basin are of significantly negative correlation, i.e. when the preceding winter MJO is relatively active, the summer precipitation in the basin decreases, and vise verse. We also analyzed the causes. When the preceding winter MJO is relatively active, its release of potential heat facilities Inter-Tropical Convergence Zone (ITCZ) to strengthen and locate northward in winter and propagate northeastward. This abnormal situation lasts from winter to summer. In mid-May, ITCZ jumps northward to the South China Sea, the western Pacific subtropical high withdraws eastward, and the South China Sea summer monsoon sets off and strengthens. In summer, ITCZ propagates to South China Sea-subtropical western Pacific, the zonal circulation of subtropical Pacific strengthens, and a local meridional circulation of the South China Sea to the basin area forms, giving rise to the East Asia Pacific teleconnection wave-train. An East Asian monsoon trough and the Meiyu front show opposite features from south to north, the East Asian summer monsoon strengthens and advances northward. As a result, the summer monsoon is weakened as the basin is controlled by the subtropical high continually, with less rain in summer. On the contrary, when the preceding winter MJO is inactive, ITCZ weakens and is located southward, the subtropical high is located southward in summer, and the basin is in a region of ascending airflow with prevailing southwest wind. The East Asian monsoon trough and EASM weaken so that summer monsoon is reduced in the basin where precipitation increases.
2012, 18(1): 45-53.
Abstract:
An inconsecutive high frequency distribution with a“sandwich structure”pattern for high temperature warm water warmer than 29℃ in the western Pacific warm pool (WPWP) was found using Tropical Rainfall Measuring Mission (TRMM) sea surface temperature (SST) data, a relatively high resolution data for space. This phenomenon only shows up in boreal summer (June to September), and becomes obvious when WPWP SST is higher than 29℃. As observed, East Asian summer monsoon (EASM) impinges on Philippine Islands in July, which has an important impact on the formation and maintenance of the “sandwich structure”. Winds affect the distribution of SST in two ways: one by increasing the local latent heat flux and the other by transporting cold water towards the southeast of Philippine Islands.
An inconsecutive high frequency distribution with a“sandwich structure”pattern for high temperature warm water warmer than 29℃ in the western Pacific warm pool (WPWP) was found using Tropical Rainfall Measuring Mission (TRMM) sea surface temperature (SST) data, a relatively high resolution data for space. This phenomenon only shows up in boreal summer (June to September), and becomes obvious when WPWP SST is higher than 29℃. As observed, East Asian summer monsoon (EASM) impinges on Philippine Islands in July, which has an important impact on the formation and maintenance of the “sandwich structure”. Winds affect the distribution of SST in two ways: one by increasing the local latent heat flux and the other by transporting cold water towards the southeast of Philippine Islands.
2012, 18(1): 54-64.
Abstract:
Variation characteristics of persistent drought events in Guangdong province are analyzed using 45-year (1961-2005) and 86-station observational precipitation data of Guangdong, and the causes of drought events are discussed from different angles (e.g., atmospheric circulation, sea surface temperature) on the basis of global coverage datasets of sea surface temperature and atmospheric elements. It is found that the occurrence frequency of persistent drought events in Guangdong province is once every 26 months on average, and autumn-winter or winter-spring persistent drought events take up the majority. The persistent drought events possess large scale spatial characteristics. While the 1960s is the most frequent and strongest decade of drought events in the latter half of the 20th century, the occurrence is more frequent and the intensity is stronger in the first five years of the 21st century (2001-2005). This reflects the response of regional extreme climatic events in Guangdong to global climatic change. The atmospheric circulation, sea surface temperature, etc, appear to have different abnormal characteristics when drought events happen in different seasons. The results of this paper provide some good reference information for the drought forecast, especially for the dynamic interpretation of climatic model products.
Variation characteristics of persistent drought events in Guangdong province are analyzed using 45-year (1961-2005) and 86-station observational precipitation data of Guangdong, and the causes of drought events are discussed from different angles (e.g., atmospheric circulation, sea surface temperature) on the basis of global coverage datasets of sea surface temperature and atmospheric elements. It is found that the occurrence frequency of persistent drought events in Guangdong province is once every 26 months on average, and autumn-winter or winter-spring persistent drought events take up the majority. The persistent drought events possess large scale spatial characteristics. While the 1960s is the most frequent and strongest decade of drought events in the latter half of the 20th century, the occurrence is more frequent and the intensity is stronger in the first five years of the 21st century (2001-2005). This reflects the response of regional extreme climatic events in Guangdong to global climatic change. The atmospheric circulation, sea surface temperature, etc, appear to have different abnormal characteristics when drought events happen in different seasons. The results of this paper provide some good reference information for the drought forecast, especially for the dynamic interpretation of climatic model products.
2012, 18(1): 65-71.
Abstract:
The interdecadal variations of tropical cyclones (TCs) and their precipitation over Guangdong Province are investigated using the observational data of TCs and precipitation from 26 observational stations in the province from 1951 to 2005. The results show that the TCs precipitation shows an oscillation with a peak value of about 25 years, with both the numbers of the Guangdong-influencing TCs and TCs formed in the western North Pacific oscillating with a peak value of about 23 years. The correlations are highly positive between the interdecadal variation of TC precipitation over the province and these numbers. The interdecadal variation of TC precipitation in the province shows significant negative correlations with the interdecadal variation of annual mean SST in some parts of the western North Pacific and the interdecadal variation of annual mean 500 hPa geopotential heights in some parts of the middle and high latitudes over the North Pacific. In general, there are high mean SSTs on the equator from central to eastern Pacific, low mean SSTs in the middle and high latitudes over the North Pacific and a main strong East Asian trough over the North Pacific in the period of less TC precipitation as compared with the period of more TC precipitation over the province.
The interdecadal variations of tropical cyclones (TCs) and their precipitation over Guangdong Province are investigated using the observational data of TCs and precipitation from 26 observational stations in the province from 1951 to 2005. The results show that the TCs precipitation shows an oscillation with a peak value of about 25 years, with both the numbers of the Guangdong-influencing TCs and TCs formed in the western North Pacific oscillating with a peak value of about 23 years. The correlations are highly positive between the interdecadal variation of TC precipitation over the province and these numbers. The interdecadal variation of TC precipitation in the province shows significant negative correlations with the interdecadal variation of annual mean SST in some parts of the western North Pacific and the interdecadal variation of annual mean 500 hPa geopotential heights in some parts of the middle and high latitudes over the North Pacific. In general, there are high mean SSTs on the equator from central to eastern Pacific, low mean SSTs in the middle and high latitudes over the North Pacific and a main strong East Asian trough over the North Pacific in the period of less TC precipitation as compared with the period of more TC precipitation over the province.
2012, 18(1): 72-80.
Abstract:
Summer precipitation patterns of Shandong Province are relatively independent with regard to the whole eastern China region. To study the rules and causes of precipitation variations, three main climate modes―on the annual, seasonal, and climatic intra-seasonal oscillation (CISO) scales―are extracted using a harmonic analysis method based on daily precipitation of Shandong during 1965-2009 and multi-year averaged pentad precipitation at 722 stations in China during 1971-2000. Among the three precipitation climate modes, the annual mode is closely related to the annual cycle of Earth-Atmosphere thermal system, which is characterized by the periodic dry and wet seasons. The seasonal mode reflects the monsoon effect on precipitation and the main flood season's contribution to annual precipitation variations. As an important climatic signal, the CISO mode is more evident during summer monsoon. The gradual modulations of the CISO mode, seasonal mode, and annual mode control the annual variation of precipitation. To study the relationship between precipitation climate modes and atmospheric circulations, an East Asian Westerly Jet Index (EAWJI) is defined in this paper. It is revealed that precipitation of Shandong is closely related to EAWJI in all climate modes. A wet or dry phase of each climate mode corresponds to a specific atmospheric circulation pattern. The phase of the annual mode is reverse to that of EAWJI. During the wet phase of the seasonal mode (weak phase of EAWJI), the atmospheric circulation in and around Shandong is characterized by upper-level divergence and low-level convergence. A reversed atmospheric circulation exists for the dry phase (strong phase for EAWJI). In the summer wet phase of CISO mode (strong phase of EAWJI), Shandong is controlled by upper-level divergence and low-level convergence. Again, the dry phase is corresponding to a reversed circulation structure. The methodology employed in this research, i.e. studying the precipitation climatic variations in terms of independent components of different temporal scales, provides a new approach for annual and seasonal precipitation prediction.
Summer precipitation patterns of Shandong Province are relatively independent with regard to the whole eastern China region. To study the rules and causes of precipitation variations, three main climate modes―on the annual, seasonal, and climatic intra-seasonal oscillation (CISO) scales―are extracted using a harmonic analysis method based on daily precipitation of Shandong during 1965-2009 and multi-year averaged pentad precipitation at 722 stations in China during 1971-2000. Among the three precipitation climate modes, the annual mode is closely related to the annual cycle of Earth-Atmosphere thermal system, which is characterized by the periodic dry and wet seasons. The seasonal mode reflects the monsoon effect on precipitation and the main flood season's contribution to annual precipitation variations. As an important climatic signal, the CISO mode is more evident during summer monsoon. The gradual modulations of the CISO mode, seasonal mode, and annual mode control the annual variation of precipitation. To study the relationship between precipitation climate modes and atmospheric circulations, an East Asian Westerly Jet Index (EAWJI) is defined in this paper. It is revealed that precipitation of Shandong is closely related to EAWJI in all climate modes. A wet or dry phase of each climate mode corresponds to a specific atmospheric circulation pattern. The phase of the annual mode is reverse to that of EAWJI. During the wet phase of the seasonal mode (weak phase of EAWJI), the atmospheric circulation in and around Shandong is characterized by upper-level divergence and low-level convergence. A reversed atmospheric circulation exists for the dry phase (strong phase for EAWJI). In the summer wet phase of CISO mode (strong phase of EAWJI), Shandong is controlled by upper-level divergence and low-level convergence. Again, the dry phase is corresponding to a reversed circulation structure. The methodology employed in this research, i.e. studying the precipitation climatic variations in terms of independent components of different temporal scales, provides a new approach for annual and seasonal precipitation prediction.
2012, 18(1): 81-88.
Abstract:
Using data available from the Retrieval System Based on Yearbooks of Tropical Cyclones over the Western North Pacific, NCEP/NCAR reanalysis daily data and observed precipitation data for 1959 to 2007 in Yunnan, a province located in a low-latitude plateau, this work analyzes the climatic characteristics and the corresponding large-scale circulation patterns related to the western North Pacific westward moving TCs (WMTCs). Its impacts on the rainfall in the Yunnan Plateau are studied. Results show that WMTCs happen almost every year, mainly from July to September. It shows a downward trend in decadal variation. Nearly the entire Yunnan area is affected by them but the eastern part experiences the most severe influences. Most of the WMTCs migrate from the South China Sea, primarily make landfall in Hainan and Guangdong and enter the Northern Bay. The tracks of these typhoons can be classified into five categories, in which the most significant impact results from those making landfall in Guangdong. All categories of the tropical cyclones can induce province-wide heavy rainfall in Yunnan. Super typhoons bring about the heaviest and most extensive rainfall over the low-latitude plateau while the associated circulation pattern is marked with a dominant 500 hPa meridional circulation at middle latitudes, an active monsoon depression and Intertropical Convection Zone (ITCZ) at low latitudes and a westward-located South Asia High at 100 hPa, which is favorable for tropical cyclones to travel westward. WMTCs tend to go westward into the interior part of China if the subtropical high extends its westernmost ridge point to the northeast of Yunnan, or expands its periphery anti-cyclonic circulation to the Tibetan Plateau, or merges with the Qinghai-Tibetan high.
Using data available from the Retrieval System Based on Yearbooks of Tropical Cyclones over the Western North Pacific, NCEP/NCAR reanalysis daily data and observed precipitation data for 1959 to 2007 in Yunnan, a province located in a low-latitude plateau, this work analyzes the climatic characteristics and the corresponding large-scale circulation patterns related to the western North Pacific westward moving TCs (WMTCs). Its impacts on the rainfall in the Yunnan Plateau are studied. Results show that WMTCs happen almost every year, mainly from July to September. It shows a downward trend in decadal variation. Nearly the entire Yunnan area is affected by them but the eastern part experiences the most severe influences. Most of the WMTCs migrate from the South China Sea, primarily make landfall in Hainan and Guangdong and enter the Northern Bay. The tracks of these typhoons can be classified into five categories, in which the most significant impact results from those making landfall in Guangdong. All categories of the tropical cyclones can induce province-wide heavy rainfall in Yunnan. Super typhoons bring about the heaviest and most extensive rainfall over the low-latitude plateau while the associated circulation pattern is marked with a dominant 500 hPa meridional circulation at middle latitudes, an active monsoon depression and Intertropical Convection Zone (ITCZ) at low latitudes and a westward-located South Asia High at 100 hPa, which is favorable for tropical cyclones to travel westward. WMTCs tend to go westward into the interior part of China if the subtropical high extends its westernmost ridge point to the northeast of Yunnan, or expands its periphery anti-cyclonic circulation to the Tibetan Plateau, or merges with the Qinghai-Tibetan high.
2012, 18(1): 89-97.
Abstract:
The effects of sea surface temperature (SST) and its diurnal variation on diurnal variation of rainfall are examined in this study by analyzing a series of equilibrium cloud-resolving model experiments which are imposed with zero large-scale vertical velocity. The grid rainfall simulation data are categorized into eight rainfall types based on rainfall processes including water vapor convergence/divergence, local atmospheric drying/moistening, and hydrometeor loss/convergence or gain/divergence. The rainfall contributions of the rainfall types with water vapor convergence are insensitive to the increase in SST from 27℃ to 29℃ during the nighttime, whereas they are decreased during the daytime. The rainfall contributions of the rainfall types with water vapor convergence are decreased as the SST increases from 29℃ to 31℃ but the decreases are larger during the nighttime than during the daytime. The rainfall contributions of the rainfall types with water vapor convergence are decreased by the inclusion of diurnal variation of SST with diurnal difference of 1℃ during the nighttime, but the decreases are significantly slowed down as the diurnal difference of SST increases from 1℃ to 2℃. The rainfall contributions of the rainfall types with water vapor convergence are insensitive to the inclusion of diurnal variation of SST during the daytime.
The effects of sea surface temperature (SST) and its diurnal variation on diurnal variation of rainfall are examined in this study by analyzing a series of equilibrium cloud-resolving model experiments which are imposed with zero large-scale vertical velocity. The grid rainfall simulation data are categorized into eight rainfall types based on rainfall processes including water vapor convergence/divergence, local atmospheric drying/moistening, and hydrometeor loss/convergence or gain/divergence. The rainfall contributions of the rainfall types with water vapor convergence are insensitive to the increase in SST from 27℃ to 29℃ during the nighttime, whereas they are decreased during the daytime. The rainfall contributions of the rainfall types with water vapor convergence are decreased as the SST increases from 29℃ to 31℃ but the decreases are larger during the nighttime than during the daytime. The rainfall contributions of the rainfall types with water vapor convergence are decreased by the inclusion of diurnal variation of SST with diurnal difference of 1℃ during the nighttime, but the decreases are significantly slowed down as the diurnal difference of SST increases from 1℃ to 2℃. The rainfall contributions of the rainfall types with water vapor convergence are insensitive to the inclusion of diurnal variation of SST during the daytime.
2012, 18(1): 98-107.
Abstract:
In this study, two convective-stratiform rainfall partitioning schemes are evaluated using precipitation and cloud statistics for different rainfall types categorized by applying surface rainfall equation on grid-scale data from a two-dimensional cloud-resolving model simulation. One scheme is based on surface rainfall intensity whereas the other is based on cloud content information. The model is largely forced by the large-scale vertical velocity derived from the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). The results reveal that over 40% of convective rainfall is associated with water vapor divergence, which primarily comes from the rainfall type with local atmospheric drying and water hydrometeor loss/convergence, caused by precipitation and evaporation of rain. More than 40% of stratiform rainfall is related to water vapor convergence, which largely comes from the rainfall type with local atmospheric moistening and hydrometeor loss/convergence attributable to water clouds through precipitation and the evaporation of rain and ice clouds through the conversion from ice hydrometeor to water hydrometeor. This implies that the separation methods based on surface rainfall and cloud content may not clearly separate convective and stratiform rainfall.
In this study, two convective-stratiform rainfall partitioning schemes are evaluated using precipitation and cloud statistics for different rainfall types categorized by applying surface rainfall equation on grid-scale data from a two-dimensional cloud-resolving model simulation. One scheme is based on surface rainfall intensity whereas the other is based on cloud content information. The model is largely forced by the large-scale vertical velocity derived from the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). The results reveal that over 40% of convective rainfall is associated with water vapor divergence, which primarily comes from the rainfall type with local atmospheric drying and water hydrometeor loss/convergence, caused by precipitation and evaporation of rain. More than 40% of stratiform rainfall is related to water vapor convergence, which largely comes from the rainfall type with local atmospheric moistening and hydrometeor loss/convergence attributable to water clouds through precipitation and the evaporation of rain and ice clouds through the conversion from ice hydrometeor to water hydrometeor. This implies that the separation methods based on surface rainfall and cloud content may not clearly separate convective and stratiform rainfall.
2012, 18(1): 108-112.
Abstract:
Based on NCEP/NCAR reanalysis data and Yearbook of China landfalling tropical cyclones (hereafter CLTC) from 1949 to 2008, correlation between CLTC frequency/intensity and 500 hPa height field and sea surface temperature (SST) fields are investigated and employed for TC statistical prediction. A prediction model for yearly and monthly intensity and frequency of CLTC is established with binomial curve fitting by choosing the gridpoints with high correlation coefficients as composite factors. Good performance of the model in experiments shows that the model could be used in routine forecast.
Based on NCEP/NCAR reanalysis data and Yearbook of China landfalling tropical cyclones (hereafter CLTC) from 1949 to 2008, correlation between CLTC frequency/intensity and 500 hPa height field and sea surface temperature (SST) fields are investigated and employed for TC statistical prediction. A prediction model for yearly and monthly intensity and frequency of CLTC is established with binomial curve fitting by choosing the gridpoints with high correlation coefficients as composite factors. Good performance of the model in experiments shows that the model could be used in routine forecast.
粤公网安备 4401069904700002号