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Abstract
Data from the Nimbus 5 Electrically Scanning Microwave Radiometer (ESMR) are used to make calculations of the latent heat release (LHR) and the distribution of rainfall rate in a case study of a tropical cyclone as it grows from a tropical disturbance to a typhoon. The results indicate that the latent heat release characteristics of tropical cyclones can be determined from the microwave data and that such observations are potentially useful in the monitoring of such storms. The LHR (calculated over a circular area of 4° latitude radius) increases during the development and intensification of the storm from a magnitude of 2.7 × 1014 W (in the disturbance stage) to 8.8 × 1014 W (typhoon stage). The later value corresponds to a mean rainfall rate of 2.0 mm h−1. Even during the disturbance stage, the LHR increases significantly. It is also shown that the more intense the cyclone and the greater the LHR, the greater the percentage contribution of the larger rainfall rates to the LHR. In the disturbance stage the percentage contribution of rainfall rates ⩾ 6 mm h−1 is typically 8%; for the typhoon stage, the value is 38%. The distribution of rainfall rate as a function of radial distance from the center indicates that as the cyclone intensifies, the higher rainfall rates tend to concentrate toward the center of the circulation.
Abstract
Data from the Nimbus 5 Electrically Scanning Microwave Radiometer (ESMR) are used to make calculations of the latent heat release (LHR) and the distribution of rainfall rate in a case study of a tropical cyclone as it grows from a tropical disturbance to a typhoon. The results indicate that the latent heat release characteristics of tropical cyclones can be determined from the microwave data and that such observations are potentially useful in the monitoring of such storms. The LHR (calculated over a circular area of 4° latitude radius) increases during the development and intensification of the storm from a magnitude of 2.7 × 1014 W (in the disturbance stage) to 8.8 × 1014 W (typhoon stage). The later value corresponds to a mean rainfall rate of 2.0 mm h−1. Even during the disturbance stage, the LHR increases significantly. It is also shown that the more intense the cyclone and the greater the LHR, the greater the percentage contribution of the larger rainfall rates to the LHR. In the disturbance stage the percentage contribution of rainfall rates ⩾ 6 mm h−1 is typically 8%; for the typhoon stage, the value is 38%. The distribution of rainfall rate as a function of radial distance from the center indicates that as the cyclone intensifies, the higher rainfall rates tend to concentrate toward the center of the circulation.
Abstract
The Nimbus-7 Total Ozone Mapping Spectrometer (TOMS) was used to map the distribution of total ozone around western North Pacific tropical cyclones from 1979 to 1982. The strong correlation between total ozone distribution and tropopause height found in the subtropical and midlatitudes made it possible for TOMS to monitor the propagation of upper-tropospheric waves and the mutual adjustment between these waves and tropical cyclones during their interaction. Changes in these total ozone patterns reflect the three-dimensional upper-tropospheric transport processes that are involved in tropical cyclone intensity and intensity and motion changes. The total ozone distributions indicate that 1) the mean upper-tropospheric circulations associated with western North Pacific and Atlantic tropical cyclones are similar; 2) more intense tropical cyclones have higher tropopauses around their centers; 3) more intense tropical cyclones have higher tropopauses on the anticyclonic-shear side of their outflow jets, which indicate that the more intense tropical cyclones have stronger outflow channels than less intense systems; 4) tropical cyclones that intensify (do not intensify) are within 10° (15°) latitude of weak (strong) upper-tropospheric troughs that are moderately rich (very rich) in total ozone; and 5) tropical cyclones turn to the left (right) when they move within approximately 15° latitude downstream of an ozone-poor (ozone-rich) upper-tropospheric ridge (trough).
Abstract
The Nimbus-7 Total Ozone Mapping Spectrometer (TOMS) was used to map the distribution of total ozone around western North Pacific tropical cyclones from 1979 to 1982. The strong correlation between total ozone distribution and tropopause height found in the subtropical and midlatitudes made it possible for TOMS to monitor the propagation of upper-tropospheric waves and the mutual adjustment between these waves and tropical cyclones during their interaction. Changes in these total ozone patterns reflect the three-dimensional upper-tropospheric transport processes that are involved in tropical cyclone intensity and intensity and motion changes. The total ozone distributions indicate that 1) the mean upper-tropospheric circulations associated with western North Pacific and Atlantic tropical cyclones are similar; 2) more intense tropical cyclones have higher tropopauses around their centers; 3) more intense tropical cyclones have higher tropopauses on the anticyclonic-shear side of their outflow jets, which indicate that the more intense tropical cyclones have stronger outflow channels than less intense systems; 4) tropical cyclones that intensify (do not intensify) are within 10° (15°) latitude of weak (strong) upper-tropospheric troughs that are moderately rich (very rich) in total ozone; and 5) tropical cyclones turn to the left (right) when they move within approximately 15° latitude downstream of an ozone-poor (ozone-rich) upper-tropospheric ridge (trough).
Abstract
The distribution and intensity of tropical cyclone precipitation has been known to have a large influence on the intensification and maintenance of the system. Therefore, monitoring the tropical cyclone convective rainband cycle and the large-scale environmental forcing mechanisms that initiate and maintain the tropical cyclone convective rainbands may aid in better understanding and predicting tropical cyclone intensification.
To demonstrate how the evolution of the tropical cyclone precipitation can be monitored, the frequent Special Sensor Microwave/Imager (SSM/I) observations of precipitation from Typhoon Bobbie (June 1992) were used to help better delineate Bobbie's convective rainband cycle. Bobbie's SSM/I-observed convective rainband cycle was then related to the tropical cyclone's intensity change. To obtain a better understanding of how Bobbie's convective rainbands were initiated and maintained, total precipitable water (TPW) over the ocean regions, mean monthly sea surface temperatures (SSTs), and analyses from the European Centre for Medium-Range Weather Forecasts(ECMWF) model were examined. The SSM/I TPW helped to substantiate the ECMWF-analyzed regions of dry and moist air that were interacting with the system's circulation, while the mean monthly SSTs were used to determine whether the western North Pacific, where Bobbie traversed, was warm enough to allow for sufficient energy flux to support convection. The ECMWF model was employed to examine the environmental forcing mechanisms that may have initiated and maintained Bobbie's convective rainbands, such as mean vertical wind shear, environmental tropospheric water vapor flux and divergence, and upper-tropospheric eddy relative angular momentum flux convergence.
Results from the analyses of Typhoon Bobbie suggested the following: 1) The SSM/I observations of Bobbie's precipitation were able to detect and monitor convective rainband cycles that were similar to those observed with land-based and aircraft radar, in situ measurements, and SSM/I observations of western North Atlantic tropical cyclones. 2) The evolution of Bobbie's intensity coincided with the SSM/I-observed convective rainband cycles. 3) The SSM/I observations of the TPW over nonraining ocean regions were able to substantiate the ECMWF-analyzed moist and dry regions that were interacting with Bobbie's circulation. 4) In regions of warm SSTs and weak vertical wind shear, the enhancement of the precipitation in Bobbie's inner-core convective rainbands coincided with the inward convergence of upper-tropospheric eddy relative angular momentum, while the initialization of Bobbie's outer-core convective rainbands appeared to coincide with the large horizontal convergence of moisture. 5) The dissipation of rain in the inner-core convective rainbands appeared to be associated with inward propagation of newly formed outer convective rainbands, strong vertical wind shear (above 10 m s−1), and cool SSTs (below 26°C).
Abstract
The distribution and intensity of tropical cyclone precipitation has been known to have a large influence on the intensification and maintenance of the system. Therefore, monitoring the tropical cyclone convective rainband cycle and the large-scale environmental forcing mechanisms that initiate and maintain the tropical cyclone convective rainbands may aid in better understanding and predicting tropical cyclone intensification.
To demonstrate how the evolution of the tropical cyclone precipitation can be monitored, the frequent Special Sensor Microwave/Imager (SSM/I) observations of precipitation from Typhoon Bobbie (June 1992) were used to help better delineate Bobbie's convective rainband cycle. Bobbie's SSM/I-observed convective rainband cycle was then related to the tropical cyclone's intensity change. To obtain a better understanding of how Bobbie's convective rainbands were initiated and maintained, total precipitable water (TPW) over the ocean regions, mean monthly sea surface temperatures (SSTs), and analyses from the European Centre for Medium-Range Weather Forecasts(ECMWF) model were examined. The SSM/I TPW helped to substantiate the ECMWF-analyzed regions of dry and moist air that were interacting with the system's circulation, while the mean monthly SSTs were used to determine whether the western North Pacific, where Bobbie traversed, was warm enough to allow for sufficient energy flux to support convection. The ECMWF model was employed to examine the environmental forcing mechanisms that may have initiated and maintained Bobbie's convective rainbands, such as mean vertical wind shear, environmental tropospheric water vapor flux and divergence, and upper-tropospheric eddy relative angular momentum flux convergence.
Results from the analyses of Typhoon Bobbie suggested the following: 1) The SSM/I observations of Bobbie's precipitation were able to detect and monitor convective rainband cycles that were similar to those observed with land-based and aircraft radar, in situ measurements, and SSM/I observations of western North Atlantic tropical cyclones. 2) The evolution of Bobbie's intensity coincided with the SSM/I-observed convective rainband cycles. 3) The SSM/I observations of the TPW over nonraining ocean regions were able to substantiate the ECMWF-analyzed moist and dry regions that were interacting with Bobbie's circulation. 4) In regions of warm SSTs and weak vertical wind shear, the enhancement of the precipitation in Bobbie's inner-core convective rainbands coincided with the inward convergence of upper-tropospheric eddy relative angular momentum, while the initialization of Bobbie's outer-core convective rainbands appeared to coincide with the large horizontal convergence of moisture. 5) The dissipation of rain in the inner-core convective rainbands appeared to be associated with inward propagation of newly formed outer convective rainbands, strong vertical wind shear (above 10 m s−1), and cool SSTs (below 26°C).
Abstract
Special Sensor Microwave/Imager (SSM/I) observations were used to examine spatial and temporal changes in the precipitation characteristics for western North Pacific tropical cyclones that reached storm stage or greater during 1987-92. The second version of the Goddard scattering algorithm, that employed the 85-GHz brightness temperatures to measure rain rate, provided an analysis of the tropical cyclone precipitation distribution in greater detail, while the numerous SSM/I observations helped to better define the relationship between the tropical cyclones’ spatial and temporal distribution of precipitation and the systems intensity, intensity change, radiational forcing, and mean monthly sea surface temperatures (SSTs). The two SSM/Is flown since 1992 also helped to provide a more detailed analysis of the evolution of the tropical cyclone inner-core diabatic heating.
Similar to the SSM/I-observed 198789 western North Atlantic tropical cyclones, the SSM/I observations of the western North Pacific tropical cyclones revealed that the more intense systems had higher rain rates and greater areal distribution of rain. In addition, the heaviest rain rates were found nearer to the center of all the tropical cyclones. However, western North Pacific typhoons were found to have heavier azimuthally averaged rain rates and a greater contribution from the heavier rain within the inner core (i.e., within 111 km of the center) than the western North Atlantic hurricanes.
The SSM/I observations of the western North Pacific tropical cyclones also suggested the following: 1) there appears to be a diurnal variation in the tropical cyclone precipitation (i.e., morning maximum and an evening minimum) except in the inner-core regions of systems that are at storm stage and greater; 2) the maximum rain rate that a tropical cyclone can produce in the inner-core region is dictated by SSTs with maximum rain rates occurring at SSTs greater than 29°C; 3) the large changes in the tropical cyclone inner-core rain rate (latent heat release) help to initiate and maintain periods of tropical cyclone intensification; and 4) the intensity of these tropical cyclones become more responsive to rain-rate changes as the tropical cyclones become more intense.
Abstract
Special Sensor Microwave/Imager (SSM/I) observations were used to examine spatial and temporal changes in the precipitation characteristics for western North Pacific tropical cyclones that reached storm stage or greater during 1987-92. The second version of the Goddard scattering algorithm, that employed the 85-GHz brightness temperatures to measure rain rate, provided an analysis of the tropical cyclone precipitation distribution in greater detail, while the numerous SSM/I observations helped to better define the relationship between the tropical cyclones’ spatial and temporal distribution of precipitation and the systems intensity, intensity change, radiational forcing, and mean monthly sea surface temperatures (SSTs). The two SSM/Is flown since 1992 also helped to provide a more detailed analysis of the evolution of the tropical cyclone inner-core diabatic heating.
Similar to the SSM/I-observed 198789 western North Atlantic tropical cyclones, the SSM/I observations of the western North Pacific tropical cyclones revealed that the more intense systems had higher rain rates and greater areal distribution of rain. In addition, the heaviest rain rates were found nearer to the center of all the tropical cyclones. However, western North Pacific typhoons were found to have heavier azimuthally averaged rain rates and a greater contribution from the heavier rain within the inner core (i.e., within 111 km of the center) than the western North Atlantic hurricanes.
The SSM/I observations of the western North Pacific tropical cyclones also suggested the following: 1) there appears to be a diurnal variation in the tropical cyclone precipitation (i.e., morning maximum and an evening minimum) except in the inner-core regions of systems that are at storm stage and greater; 2) the maximum rain rate that a tropical cyclone can produce in the inner-core region is dictated by SSTs with maximum rain rates occurring at SSTs greater than 29°C; 3) the large changes in the tropical cyclone inner-core rain rate (latent heat release) help to initiate and maintain periods of tropical cyclone intensification; and 4) the intensity of these tropical cyclones become more responsive to rain-rate changes as the tropical cyclones become more intense.
Abstract
Three periods within the life cycle of Hurricane Camille (1969) are examined with radiometric and camera measurements from Nimbus 3 and camera information from ATS 3 in conjunction with conventional information. These periods are the deepening phase, the interaction of Camille with mid-latitude westerlies, and the excessive rain-producing period when the cyclone was over the central Appalachians.
Just prior to significant deepening, the Nimbus 3 Medium Resolution Infrared Radiometer (MRIR) window and water vapor channels showed a band of developing convection that extended to the cirrus level in the southeastern quadrant of the storm which originated from the ITCZ. Low-level wind fields were derived from conventional sources as well as from cumulus clouds tracked from a series of ATS 3 images. Within this band were low-level 30 kt winds that supplied Camille with strong inflow where the air passed over sea surface temperatures that were 1–3 standard deviations above normal.
At the beginning of the rapid deepening the MRIR radiometer measurements indicated a rapid contraction of the central dense overcast and then an expansion as the maximum deepening rate occurred. Simultaneously, the increase in the MRIR equivalent blackbody temperatures (TBB ) indicated the development of large-scale subsidence throughout the troposphere northwest of the center. When Camille weakened as it moved over the lower Mississippi Valley, the cyclone acted as a partial obstruction to the synoptic-scale flow and increased the subsidence west and north of the cyclone center as indicated by the increase in water vapor TBB and verified by three-dimensional trajectories. Increased cloud-top elevations, approaching the levels reached when Camille was an intense cyclone over the Gulf of Mexico, were estimated from the Nimbus 3 High Resolution Infrared Radiometer (HRIR) measurements on 20 August 1969, when Camille produced rains of major flood proportions near the east slopes of the Appalachians in central Virginia.
Abstract
Three periods within the life cycle of Hurricane Camille (1969) are examined with radiometric and camera measurements from Nimbus 3 and camera information from ATS 3 in conjunction with conventional information. These periods are the deepening phase, the interaction of Camille with mid-latitude westerlies, and the excessive rain-producing period when the cyclone was over the central Appalachians.
Just prior to significant deepening, the Nimbus 3 Medium Resolution Infrared Radiometer (MRIR) window and water vapor channels showed a band of developing convection that extended to the cirrus level in the southeastern quadrant of the storm which originated from the ITCZ. Low-level wind fields were derived from conventional sources as well as from cumulus clouds tracked from a series of ATS 3 images. Within this band were low-level 30 kt winds that supplied Camille with strong inflow where the air passed over sea surface temperatures that were 1–3 standard deviations above normal.
At the beginning of the rapid deepening the MRIR radiometer measurements indicated a rapid contraction of the central dense overcast and then an expansion as the maximum deepening rate occurred. Simultaneously, the increase in the MRIR equivalent blackbody temperatures (TBB ) indicated the development of large-scale subsidence throughout the troposphere northwest of the center. When Camille weakened as it moved over the lower Mississippi Valley, the cyclone acted as a partial obstruction to the synoptic-scale flow and increased the subsidence west and north of the cyclone center as indicated by the increase in water vapor TBB and verified by three-dimensional trajectories. Increased cloud-top elevations, approaching the levels reached when Camille was an intense cyclone over the Gulf of Mexico, were estimated from the Nimbus 3 High Resolution Infrared Radiometer (HRIR) measurements on 20 August 1969, when Camille produced rains of major flood proportions near the east slopes of the Appalachians in central Virginia.
Abstract
The relationship between the mean temperature of the top of the cloud canopies and the future maximum winds of Atlantic Ocean tropical cyclones is analyzed. The area-average cloud top temperatures from 309 observations of 12 tropical cyclones which occurred during 1974–79 were compiled from infrared measurements made by Geostationary Operational Environment Satellites. Maximum winds were obtained from best track records.
The satellite measurements showed that prolonged surges of intense convection developed in the near region surrounding the depression centers before the maximum winds initially increased. Subsequent weakening of the convection occurred but was frequently followed by new surges of intense convection. It was found that when these prolonged surges of intense convection 1asted for 9 or more hours, and the filtered (6-h running mean) area-average cloud top temperature within 222 km of the tropical cyclone centers was 238 K or less, that the maximum winds of the tropical cyclones increased by 5 m s−1 or more within 24 h later, 71 % of the time. However, when intense convection was not present, similar maximum wind increases occurred only 37% of the time.
The future maximum winds were compared with both the filtered area-average cloud top temperatures measured during the strong convective surges and the storm's intensities at the filtered temperature times using multiple linear regression. The correlation was found to be 0.771 for moderate/strong storms (storm intensity of 26 m s−1 or more) and 0.610 for weak storms (stores intensity of less than 26 m s−1). The relationships are statistically significant at the 0.0005 and 0.05 levels, respectively, and the lag time is near 24 h. The standard error of the regression is 5.7 and 6.2 m s−1, respectively. Statistical tests made to determine the quality of expected performance suggest that predictive equations will yield maximum wind intensities within 3 and 4 m s−1, respectively, of the standard error of the regression 95% of the time. In an independent test, the standard deviation of the error of the predicted maximum winds of moderate/strong storms was 8 m s−1, or well within the expected bounds.
Abstract
The relationship between the mean temperature of the top of the cloud canopies and the future maximum winds of Atlantic Ocean tropical cyclones is analyzed. The area-average cloud top temperatures from 309 observations of 12 tropical cyclones which occurred during 1974–79 were compiled from infrared measurements made by Geostationary Operational Environment Satellites. Maximum winds were obtained from best track records.
The satellite measurements showed that prolonged surges of intense convection developed in the near region surrounding the depression centers before the maximum winds initially increased. Subsequent weakening of the convection occurred but was frequently followed by new surges of intense convection. It was found that when these prolonged surges of intense convection 1asted for 9 or more hours, and the filtered (6-h running mean) area-average cloud top temperature within 222 km of the tropical cyclone centers was 238 K or less, that the maximum winds of the tropical cyclones increased by 5 m s−1 or more within 24 h later, 71 % of the time. However, when intense convection was not present, similar maximum wind increases occurred only 37% of the time.
The future maximum winds were compared with both the filtered area-average cloud top temperatures measured during the strong convective surges and the storm's intensities at the filtered temperature times using multiple linear regression. The correlation was found to be 0.771 for moderate/strong storms (storm intensity of 26 m s−1 or more) and 0.610 for weak storms (stores intensity of less than 26 m s−1). The relationships are statistically significant at the 0.0005 and 0.05 levels, respectively, and the lag time is near 24 h. The standard error of the regression is 5.7 and 6.2 m s−1, respectively. Statistical tests made to determine the quality of expected performance suggest that predictive equations will yield maximum wind intensities within 3 and 4 m s−1, respectively, of the standard error of the regression 95% of the time. In an independent test, the standard deviation of the error of the predicted maximum winds of moderate/strong storms was 8 m s−1, or well within the expected bounds.
Abstract
Satellite-measured equivalent blackbody temperatures of Atlantic Ocean tropical cyclones are used to describe the associated convection and cloud patterns. Average equivalent blackbody temperatures were developed from 538 geostationary satellite observations of 23 tropical cyclones. The average values were stratified into tropical storm or hurricane intensity category, then normalized to local standard time and composited to provide a 24 h diurnal time series. The composited values represent the mean cloud top temperature within data rings around the tropical cyclone centers.
The cloud top temperatures when compared to a mean tropical atmosphere suggest that the mean top of the dense cloud canopy of hurricanes is near 10.6 km and extends horizontally to 321 km radius from the center. The mean top of the dense canopy of tropical storms is near 9.7 km and extends horizontally to 278 km from the center. The mean top of the deep convection near the center of hurricanes is near 13 km and in tropical storms is near 12 km. A Fourier series analysis of the 24 h time series shows diurnal and semidiurnal cloud patterns which are statistically significant at the 0.0005 and 0.01 levels, respectively. The cloud cycles are in phase with the convection and cloud activity found in tropical systems by other investigators.
Abstract
Satellite-measured equivalent blackbody temperatures of Atlantic Ocean tropical cyclones are used to describe the associated convection and cloud patterns. Average equivalent blackbody temperatures were developed from 538 geostationary satellite observations of 23 tropical cyclones. The average values were stratified into tropical storm or hurricane intensity category, then normalized to local standard time and composited to provide a 24 h diurnal time series. The composited values represent the mean cloud top temperature within data rings around the tropical cyclone centers.
The cloud top temperatures when compared to a mean tropical atmosphere suggest that the mean top of the dense cloud canopy of hurricanes is near 10.6 km and extends horizontally to 321 km radius from the center. The mean top of the dense canopy of tropical storms is near 9.7 km and extends horizontally to 278 km from the center. The mean top of the deep convection near the center of hurricanes is near 13 km and in tropical storms is near 12 km. A Fourier series analysis of the 24 h time series shows diurnal and semidiurnal cloud patterns which are statistically significant at the 0.0005 and 0.01 levels, respectively. The cloud cycles are in phase with the convection and cloud activity found in tropical systems by other investigators.
Abstract
A statistical method has been developed using satellite, climatological, and persistence data to predict tropical cyclone position 12, 24, 48 and 72 h after initial observation. The satellite measurements were infrared window channel (11.0 μm) equivalent blackbody temperatures (TBB ), which gave representations (through the cloud and surface temperature fields) of the structure of the cyclones and the circulation features surrounding them. There were 197 individual measurements of TBB for each cyclone observation. Algorithms have been prepared using digital data from a single satellite image, 14 climatological and persistence type variables, and a combination of these data sources. The algorithms were developed using a unique statistical procedure based on an eigenvector preprocessing and the use of independent tests for screening decisions.
Independent testing of these algorithms showed that the average error made by the algorithms developed from the single satellite observation were comparable to the 48 h Joint Typhoon Warning Center (JTWC) forecast and were approximately 10% better for 72 h forecasts. Forecasts using only the climatological and persistence variables were about 20% worse than JTWC for 24 h forecasts and 10% worse for 48 and 72 h forecasts. When both satellite and nonsatellite variables were included, the performance was comparable to JTWC's for the 24 and 48 h forecasts and approximately 25% better than JTWC's for the 72 h forecasts.
The performance of the objective algorithms for various partitions was analyzed. It is shown that both the satellite and nonsatellite variables make significant and unique contributions.
Abstract
A statistical method has been developed using satellite, climatological, and persistence data to predict tropical cyclone position 12, 24, 48 and 72 h after initial observation. The satellite measurements were infrared window channel (11.0 μm) equivalent blackbody temperatures (TBB ), which gave representations (through the cloud and surface temperature fields) of the structure of the cyclones and the circulation features surrounding them. There were 197 individual measurements of TBB for each cyclone observation. Algorithms have been prepared using digital data from a single satellite image, 14 climatological and persistence type variables, and a combination of these data sources. The algorithms were developed using a unique statistical procedure based on an eigenvector preprocessing and the use of independent tests for screening decisions.
Independent testing of these algorithms showed that the average error made by the algorithms developed from the single satellite observation were comparable to the 48 h Joint Typhoon Warning Center (JTWC) forecast and were approximately 10% better for 72 h forecasts. Forecasts using only the climatological and persistence variables were about 20% worse than JTWC for 24 h forecasts and 10% worse for 48 and 72 h forecasts. When both satellite and nonsatellite variables were included, the performance was comparable to JTWC's for the 24 and 48 h forecasts and approximately 25% better than JTWC's for the 72 h forecasts.
The performance of the objective algorithms for various partitions was analyzed. It is shown that both the satellite and nonsatellite variables make significant and unique contributions.
Abstract
The Nimbus-7 Total Ozone Mapping spectrometer (TOMS) was used to map the distribution of total Ozone in and around western Atlantic tropical cyclones from 1979 to 1982. It was found that the TOMS-observed total Ozone distribution within the subtropics during the tropical cyclone seasonal correlated well with the tropopause topoghraphy, similar to earlier middle-latitudinal observations. This relationship made it possible to use TOMS to monitor the propagation of upper-tropospheric subtropical transient waves and the mutual adjustment between the tropical cyclone and the upper-tropospheric waves during their interaction. These total ozone patterns reflected the three-dimensional upper-tropospheric transport processes that were conducive for storm intensification and weakening. It was also found from satellite observations and numerical model simulations that modification of the environmental distribution of total ozone by the tropical cyclones was primarily caused by the secondary circulation associated with the tropical cyclone's outflow jet and the intrusion of stratospheric air in the eyes of tropical cyclones.
Abstract
The Nimbus-7 Total Ozone Mapping spectrometer (TOMS) was used to map the distribution of total Ozone in and around western Atlantic tropical cyclones from 1979 to 1982. It was found that the TOMS-observed total Ozone distribution within the subtropics during the tropical cyclone seasonal correlated well with the tropopause topoghraphy, similar to earlier middle-latitudinal observations. This relationship made it possible to use TOMS to monitor the propagation of upper-tropospheric subtropical transient waves and the mutual adjustment between the tropical cyclone and the upper-tropospheric waves during their interaction. These total ozone patterns reflected the three-dimensional upper-tropospheric transport processes that were conducive for storm intensification and weakening. It was also found from satellite observations and numerical model simulations that modification of the environmental distribution of total ozone by the tropical cyclones was primarily caused by the secondary circulation associated with the tropical cyclone's outflow jet and the intrusion of stratospheric air in the eyes of tropical cyclones.
Abstract
Special Sensor Microwave/Imager (SSM/I) observations were used to examine the spatial and temporal changes of the precipitation characteristics of tropical cyclones. SSM/I observations were also combined with the results of a tropical cyclone numerical model to examine the role of inner-core diabatic heating in subsequent intensity changes of tropical cyclones. Included in the SSM/I observations were rainfall characteristics of 18 named western North Atlantic tropical cyclones between 1987 and 1989. The SSM/I rain-rate algorithm that employed the 85-GHz channel provided an analysis of the rain-rate distribution in greater detail. However, the SSM/I algorithm underestimated the rain rates when compared to in situ techniques but appeared to be comparable to the rain rates obtained from other satellite-borne passive microwave radiometers.
The analysis of SSM/I observations found that more intense systems had higher rain rates, more latent heat release, and a greater contribution from heavier rain to the total tropical cyclone rainfall. In addition, regions with the heaviest rain rates were found near the center of the most intense tropical cyclones. Observational analysis from SSM/I also revealed that the greatest rain rates in the inner-core regions were found in the right half of fast-moving tropical cyclones, while the heaviest rain rates in slow-moving tropical cyclones were found in the forward half. The combination of SSM/I observations and an interpretation of numerical model simulations revealed that the correlation between changes in the inner core diabatic beating and the subsequent intensity become greater as the tropical cyclones became more intense.
Abstract
Special Sensor Microwave/Imager (SSM/I) observations were used to examine the spatial and temporal changes of the precipitation characteristics of tropical cyclones. SSM/I observations were also combined with the results of a tropical cyclone numerical model to examine the role of inner-core diabatic heating in subsequent intensity changes of tropical cyclones. Included in the SSM/I observations were rainfall characteristics of 18 named western North Atlantic tropical cyclones between 1987 and 1989. The SSM/I rain-rate algorithm that employed the 85-GHz channel provided an analysis of the rain-rate distribution in greater detail. However, the SSM/I algorithm underestimated the rain rates when compared to in situ techniques but appeared to be comparable to the rain rates obtained from other satellite-borne passive microwave radiometers.
The analysis of SSM/I observations found that more intense systems had higher rain rates, more latent heat release, and a greater contribution from heavier rain to the total tropical cyclone rainfall. In addition, regions with the heaviest rain rates were found near the center of the most intense tropical cyclones. Observational analysis from SSM/I also revealed that the greatest rain rates in the inner-core regions were found in the right half of fast-moving tropical cyclones, while the heaviest rain rates in slow-moving tropical cyclones were found in the forward half. The combination of SSM/I observations and an interpretation of numerical model simulations revealed that the correlation between changes in the inner core diabatic beating and the subsequent intensity become greater as the tropical cyclones became more intense.