2001 Vol. 7, No. 2
2001, 7(2): 113-121.
Abstract:
On the basis of comparison of 1982/1983 strong ENSO processes, key characteristics such as rapid development, immense intensity and abrupt retreat are revealed with regard to the warm episode in 1997/1998, features governing the intraseasonal oscillation for the tropical Indian Ocean and the western Pacific during its onset and evolution of the ocean and atmosphere for the process are diagnostically studied in detail.
On the basis of comparison of 1982/1983 strong ENSO processes, key characteristics such as rapid development, immense intensity and abrupt retreat are revealed with regard to the warm episode in 1997/1998, features governing the intraseasonal oscillation for the tropical Indian Ocean and the western Pacific during its onset and evolution of the ocean and atmosphere for the process are diagnostically studied in detail.
2001, 7(2): 122-130.
Abstract:
The teleconnection distribution characteristics of sea surface temperature (SST) over the India Ocean and the precipitation during rainy season in China were studied by using the methods of EOF and CCA. The results indicate that the change of SST field will affect the change of rain belt during rainy seasons in China, and greatly affect the precipitation in northwest and southwest China, the Yangzi and Yellow River downstream basins. Strong signal phenomena of SSTA over India Ocean were revealed that showed the anomalous distribution of drought and flood in China. It shows that the precipitation during rainy seasons in China may be forecast by analyzing SST distribution characteristics over the India Ocean.
The teleconnection distribution characteristics of sea surface temperature (SST) over the India Ocean and the precipitation during rainy season in China were studied by using the methods of EOF and CCA. The results indicate that the change of SST field will affect the change of rain belt during rainy seasons in China, and greatly affect the precipitation in northwest and southwest China, the Yangzi and Yellow River downstream basins. Strong signal phenomena of SSTA over India Ocean were revealed that showed the anomalous distribution of drought and flood in China. It shows that the precipitation during rainy seasons in China may be forecast by analyzing SST distribution characteristics over the India Ocean.
2001, 7(2): 131-143.
Abstract:
In this work, the SCSMEX data are used to diagnose and compare the local land-sea thermal conditions, with the focus of discussion on possible influences of thermal forcing of the western Pacific and the Tibetan Plateau on the onset and development of summer monsoon in 1998. Results show a close relationship between the distribution of the heat sources and the land-sea contrast. Due to the blocking effect of terrain, main maximum zones of the heat sources in areas with more evident north-south land-sea contrast are more obviously southward located than those exclusively with oceans. The surface heating is characterized with apparent seasonal variation and difference between land and sea. The relationship between the western Pacific and the onset of summer monsoon is reflected in the variations of the sea surface temperature (SST) and the latent heat. The influence mechanism of the Tibetan Plateau during the summer monsoon is different: it is dominated by sensible heating during the South China Sea monsoon and by condensed latent heating during the Indian monsoon.
In this work, the SCSMEX data are used to diagnose and compare the local land-sea thermal conditions, with the focus of discussion on possible influences of thermal forcing of the western Pacific and the Tibetan Plateau on the onset and development of summer monsoon in 1998. Results show a close relationship between the distribution of the heat sources and the land-sea contrast. Due to the blocking effect of terrain, main maximum zones of the heat sources in areas with more evident north-south land-sea contrast are more obviously southward located than those exclusively with oceans. The surface heating is characterized with apparent seasonal variation and difference between land and sea. The relationship between the western Pacific and the onset of summer monsoon is reflected in the variations of the sea surface temperature (SST) and the latent heat. The influence mechanism of the Tibetan Plateau during the summer monsoon is different: it is dominated by sensible heating during the South China Sea monsoon and by condensed latent heating during the Indian monsoon.
2001, 7(2): 144-153.
Abstract:
By comparing with ENSO events that ever happened in the history, the basic features and probable causes of the anomalous sea surface temperature of the tropical Pacific Ocean during 1997 and 1998 have been analyzed diagnostically. It is found that the 1997/1998 El Nino had significant abnormalities and peculiarities. It differs from the previous El Niño events falling into the simple “eastern pattern” or “western pattern”. The predictions of 1997/1998 El Niño event have also been tested with an intermediate ocean-atmosphere coupled dynamic model. The results show that the skills of the 0～24 lead month forecasts for the warm event are all above 0.5. The predictions of the mature phase and the later stages of the warm event are better than those of the beginning phase.
By comparing with ENSO events that ever happened in the history, the basic features and probable causes of the anomalous sea surface temperature of the tropical Pacific Ocean during 1997 and 1998 have been analyzed diagnostically. It is found that the 1997/1998 El Nino had significant abnormalities and peculiarities. It differs from the previous El Niño events falling into the simple “eastern pattern” or “western pattern”. The predictions of 1997/1998 El Niño event have also been tested with an intermediate ocean-atmosphere coupled dynamic model. The results show that the skills of the 0～24 lead month forecasts for the warm event are all above 0.5. The predictions of the mature phase and the later stages of the warm event are better than those of the beginning phase.
2001, 7(2): 154-162.
Abstract:
The paper gives the distributions of the daily mean temperature of black body of satellite infrared images from June 7 to 10, 1998 during HUAMEX and examines 14 meso-α-scale convective systems and a number of meso-b-scale convective systems using the satellite infrared images at 1-h intervals. The mesoscale convective systems on June 7 and 9, which resulted in severe rainstorm over the middle of Taiwan and the estuary region of the Pearl River (Zhujiang R.), are emphatically analyzed. The serial development of mesoscale convective systems is revealed by the distributions of the black body temperature of satellite infrared images. The environmental conditions in which many mesoscale convective systems continuously occurred are diagnosed. The visualizing tool, LiveView, displays the link between the upper and lower horizontal wind fields and the vertical circulations and 3-dimensional trajectories of moist air motions, based on the data of objective analyses.
The paper gives the distributions of the daily mean temperature of black body of satellite infrared images from June 7 to 10, 1998 during HUAMEX and examines 14 meso-α-scale convective systems and a number of meso-b-scale convective systems using the satellite infrared images at 1-h intervals. The mesoscale convective systems on June 7 and 9, which resulted in severe rainstorm over the middle of Taiwan and the estuary region of the Pearl River (Zhujiang R.), are emphatically analyzed. The serial development of mesoscale convective systems is revealed by the distributions of the black body temperature of satellite infrared images. The environmental conditions in which many mesoscale convective systems continuously occurred are diagnosed. The visualizing tool, LiveView, displays the link between the upper and lower horizontal wind fields and the vertical circulations and 3-dimensional trajectories of moist air motions, based on the data of objective analyses.
2001, 7(2): 163-174.
Abstract:
Based on the El Nino event data sequence from 1854 to 1993, the nature of sequences was determined by using statistical normal and independent tests, etc. With the Markov random process and first order auto-regression predictive model, we set up the prognostication mode and give the time limit of the occurrence of next El Nino event, which probably occurs around 2002.The occurring probability for 2001 is 44 %, and it is 61 % for 2002.
Based on the El Nino event data sequence from 1854 to 1993, the nature of sequences was determined by using statistical normal and independent tests, etc. With the Markov random process and first order auto-regression predictive model, we set up the prognostication mode and give the time limit of the occurrence of next El Nino event, which probably occurs around 2002.The occurring probability for 2001 is 44 %, and it is 61 % for 2002.
2001, 7(2): 175-186.
Abstract:
Seven key areas of air-sea interaction in the global oceans are determined by comprehensive analysis of the global data of monthly mean sea surface temperature (SST), surface wind, temperature, humidity, sea surface sensible heat and latent heat fluxes. The time-lag correlation between SST and each atmospheric element in each key area are focally analyzed to expose the same and the different features of air-sea interaction in different key areas. The results show that the air-sea thermal interaction is strong in each area, SST, temperature and humidity can be fairly replaced with one another, particularly in the central eastern Pacific and the south India Ocean. The dynamic effect on SST is different in different areas and in the central western Pacific such effect is more important. The correlation between sensible heat, latent heat and SST is more significant in the eastern Pacific, the western Pacific and the two major monsoon areas ― the northwestern Pacific and the south India Ocean. By analyzing the sustainable correlation probability of SST and every atmospheric element in each key area, we further know that the anomalies of which element, in which area and in which period are well sustained or easily destroyed. This is beneficial not only to prediction, but also to discussion of the physical mechanism of air-sea interaction.
Seven key areas of air-sea interaction in the global oceans are determined by comprehensive analysis of the global data of monthly mean sea surface temperature (SST), surface wind, temperature, humidity, sea surface sensible heat and latent heat fluxes. The time-lag correlation between SST and each atmospheric element in each key area are focally analyzed to expose the same and the different features of air-sea interaction in different key areas. The results show that the air-sea thermal interaction is strong in each area, SST, temperature and humidity can be fairly replaced with one another, particularly in the central eastern Pacific and the south India Ocean. The dynamic effect on SST is different in different areas and in the central western Pacific such effect is more important. The correlation between sensible heat, latent heat and SST is more significant in the eastern Pacific, the western Pacific and the two major monsoon areas ― the northwestern Pacific and the south India Ocean. By analyzing the sustainable correlation probability of SST and every atmospheric element in each key area, we further know that the anomalies of which element, in which area and in which period are well sustained or easily destroyed. This is beneficial not only to prediction, but also to discussion of the physical mechanism of air-sea interaction.
2001, 7(2): 187-198.
Abstract:
In this paper, statistics were analyzed concerning correlation between the storm rainfall far from typhoon and non-zonal upper-level jet stream. The results show that the jet stream at 200 hPa is constantly SW (90.2 %) during the period in which storm rainfall occurs. Rainfall area lies in the right rear regions of the jet axes. While the storm intensifies, the jet tends to be stronger and turn non-zonal. With the MM4 model, numerical simulation and diagnosis were carried out for Typhoon No.9711 (Winnie) on August 19 to 20, 1997. The distant storm rainfall is tightly correlative to the jet and low-level typhoon trough. The divergence field of jet is related to the v component. The upper level can cause the allobaric wind convergence at low level. This is the result of the form of low-level typhoon trough and the strength of the storm. By scale analysis, it is found that there is a branch of middle scale transverse inverse circulation in the right entrance regions behind the jet below the 300-hPa level, which is very important to the maintenance and strengthening of storm rainfall. This branch of inverse circulation is relative to the reinforcement of jet's non-zonal characteristics. From the field of mesoscale divergence field and non-zonal wind field, we know that the stronger symmetry caused by transverse circulation in the two sides of the jet, rainfall’s feedback and reinforcement of jet’s non-zonal characteristics had lead to positive feedback mechanism that was favorable of storm rainfall’s strengthening.
In this paper, statistics were analyzed concerning correlation between the storm rainfall far from typhoon and non-zonal upper-level jet stream. The results show that the jet stream at 200 hPa is constantly SW (90.2 %) during the period in which storm rainfall occurs. Rainfall area lies in the right rear regions of the jet axes. While the storm intensifies, the jet tends to be stronger and turn non-zonal. With the MM4 model, numerical simulation and diagnosis were carried out for Typhoon No.9711 (Winnie) on August 19 to 20, 1997. The distant storm rainfall is tightly correlative to the jet and low-level typhoon trough. The divergence field of jet is related to the v component. The upper level can cause the allobaric wind convergence at low level. This is the result of the form of low-level typhoon trough and the strength of the storm. By scale analysis, it is found that there is a branch of middle scale transverse inverse circulation in the right entrance regions behind the jet below the 300-hPa level, which is very important to the maintenance and strengthening of storm rainfall. This branch of inverse circulation is relative to the reinforcement of jet's non-zonal characteristics. From the field of mesoscale divergence field and non-zonal wind field, we know that the stronger symmetry caused by transverse circulation in the two sides of the jet, rainfall’s feedback and reinforcement of jet’s non-zonal characteristics had lead to positive feedback mechanism that was favorable of storm rainfall’s strengthening.
2001, 7(2): 199-208.
Abstract:
Dynamic and numerical methods are used to discuss the atmospheric response to SST thermal forcing. The results show that for planetary scale systems, the standing SST thermal forcing can quickly excite a stable atmospheric equilibrium state response, which is characterized by obvious large-scale teleconnection oscillation in east-west and south-north directions. For synoptic scale systems, the SST thermal forcing mainly excites the atmospheric low-frequency oscillation. Some basic relation and dynamic processes between SST thermal forcing and atmospheric response pattern are revealed and some new viewpoints are presented.
Dynamic and numerical methods are used to discuss the atmospheric response to SST thermal forcing. The results show that for planetary scale systems, the standing SST thermal forcing can quickly excite a stable atmospheric equilibrium state response, which is characterized by obvious large-scale teleconnection oscillation in east-west and south-north directions. For synoptic scale systems, the SST thermal forcing mainly excites the atmospheric low-frequency oscillation. Some basic relation and dynamic processes between SST thermal forcing and atmospheric response pattern are revealed and some new viewpoints are presented.
2001, 7(2): 209-217.
Abstract:
Using the T63L16 analysis data with the resolution of 1.875–w1.875 degree of latitude and longitude obtained from National Meteorological Center (NMC) and the real central position information of tropical cyclone (referred to as TC hereafter) numbered by NMC, the basic environmental geostrophic flow at 126 time levels of 25 TCs in 1996 are calculated. The vertical distribution features of the flows are analyzed. Besides, the deviation of real TC tracks from the flows (referred as steering deviation hereafter, namely, the deviation between the real central position of TC and the position calculated according to the steering flow) is also investigated. The result shows that the steering deviation would be different if the domain used to calculate the steering flow is different. The present paper obtains the optimum domain size to calculate the steering flow. It is found that the steering deviation is related to the velocity of steering flow and the initial latitude and intensity of TC itself, and that TC motion has relationship with the vertical shear structure of environmental geostrophic flow. The result also shows that the optimum steering flow is the deep-layer averaged basic flow from 1000 hPa to 200 hPa. Having the knowledge of these principle and features would help make accurate forecast of TC motion.
Using the T63L16 analysis data with the resolution of 1.875–w1.875 degree of latitude and longitude obtained from National Meteorological Center (NMC) and the real central position information of tropical cyclone (referred to as TC hereafter) numbered by NMC, the basic environmental geostrophic flow at 126 time levels of 25 TCs in 1996 are calculated. The vertical distribution features of the flows are analyzed. Besides, the deviation of real TC tracks from the flows (referred as steering deviation hereafter, namely, the deviation between the real central position of TC and the position calculated according to the steering flow) is also investigated. The result shows that the steering deviation would be different if the domain used to calculate the steering flow is different. The present paper obtains the optimum domain size to calculate the steering flow. It is found that the steering deviation is related to the velocity of steering flow and the initial latitude and intensity of TC itself, and that TC motion has relationship with the vertical shear structure of environmental geostrophic flow. The result also shows that the optimum steering flow is the deep-layer averaged basic flow from 1000 hPa to 200 hPa. Having the knowledge of these principle and features would help make accurate forecast of TC motion.
2001, 7(2): 218-224.
Abstract:
The capacity of Tropical Rainfall Measuring Mission (TRMM) Satellite for measuring rainfall was examined by using TMI-85.5 GHz microwave image data and precipitation data during a heavy rainfall experiment in southern China. From comparisons with the distribution of rain amount in an hour with BB T of 85.5 GHz microwave, it is clear that the center of heavy rain corresponds with an area of low BB T value. The location and shape of BB T distribution is similar to that of precipitation, and the larger the rainfall rates, the lower the BB T . A statistic analysis shows that the correlation coefficients between BB T and rain rates is negative and significant. Especially, when the rain rate is over 7 mm/h, the correlation degree between BB T and rain rates is more significant. The results shows that TRMM/TMI-85.5 G has great ability to measure convective heavy rain.
The capacity of Tropical Rainfall Measuring Mission (TRMM) Satellite for measuring rainfall was examined by using TMI-85.5 GHz microwave image data and precipitation data during a heavy rainfall experiment in southern China. From comparisons with the distribution of rain amount in an hour with BB T of 85.5 GHz microwave, it is clear that the center of heavy rain corresponds with an area of low BB T value. The location and shape of BB T distribution is similar to that of precipitation, and the larger the rainfall rates, the lower the BB T . A statistic analysis shows that the correlation coefficients between BB T and rain rates is negative and significant. Especially, when the rain rate is over 7 mm/h, the correlation degree between BB T and rain rates is more significant. The results shows that TRMM/TMI-85.5 G has great ability to measure convective heavy rain.
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