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Abstract
A bow echo is a bow-shaped radar reflectivity pattern that is often accompanied by downbursts at the apex of the bulge. It appears that there are two types of bow echoes documented in the literature, the squall-line type (SLBE) and the single-cell type (CBE). It is not clear that these two types of bow echoes are dynamically similar. This study presents the first complete case study on the CBE, which occurred on 14 July 1982 during the Joint Airport Weather Studies (JAWS) Project. The stormwide kinematic and thermodynamic structure of this storm was documented in Part I of this paper. This paper examines the initiation and evolution of a vorticity couplet using a vorticity-budget analysis to study the bow-echo structure and the bow-echo-microburst relationship.
The elongated-shaped echo assumed a bowed shape below cloud base after the downdraft developed. The bow echo is associated with a cyclonic-anticyclonic vorticity couplet with maximum relative vorticity intensifies of 5×10−3 and −4×10−3s−1 respectively, at the 2.4-km height. This couplet does not exist prior to the initiation of the downdraft. Examination of the vorticity budget shows that the vertical vorticity couplet is generated primarily through tilting of ambient horizontal vorticity by the microburst downdraft. The positive vorticity is enhanced by both the stretching effect and the downward advection of positive vorticity from above that is produced by the updraft through the same mechanism. A particle-trajectory analysis shows that the elongated echo is distorted into a bow shape by the shear vorticity, which exhibits a velocity differential between the center and edges of the echo.
A conceptual evolution model of the CBE is constructed based on the vorticity analysis in which an elongated echo may deform into a bow shape under the following meteorological condition: 1) a nearly unidirectional vertical shear, and 2) downdraft development. The product of the vertical shear and the horizontal gradient of the downdraft determine the strength of the vorticity couplet and hence the extent of the echo deformation. Since the environmental shear is often weak with an airmass thunderstorm, a strong downdraft is required to form a strong vorticity couplet. This may be why a CBE is often associated with strong wind events.
Abstract
A bow echo is a bow-shaped radar reflectivity pattern that is often accompanied by downbursts at the apex of the bulge. It appears that there are two types of bow echoes documented in the literature, the squall-line type (SLBE) and the single-cell type (CBE). It is not clear that these two types of bow echoes are dynamically similar. This study presents the first complete case study on the CBE, which occurred on 14 July 1982 during the Joint Airport Weather Studies (JAWS) Project. The stormwide kinematic and thermodynamic structure of this storm was documented in Part I of this paper. This paper examines the initiation and evolution of a vorticity couplet using a vorticity-budget analysis to study the bow-echo structure and the bow-echo-microburst relationship.
The elongated-shaped echo assumed a bowed shape below cloud base after the downdraft developed. The bow echo is associated with a cyclonic-anticyclonic vorticity couplet with maximum relative vorticity intensifies of 5×10−3 and −4×10−3s−1 respectively, at the 2.4-km height. This couplet does not exist prior to the initiation of the downdraft. Examination of the vorticity budget shows that the vertical vorticity couplet is generated primarily through tilting of ambient horizontal vorticity by the microburst downdraft. The positive vorticity is enhanced by both the stretching effect and the downward advection of positive vorticity from above that is produced by the updraft through the same mechanism. A particle-trajectory analysis shows that the elongated echo is distorted into a bow shape by the shear vorticity, which exhibits a velocity differential between the center and edges of the echo.
A conceptual evolution model of the CBE is constructed based on the vorticity analysis in which an elongated echo may deform into a bow shape under the following meteorological condition: 1) a nearly unidirectional vertical shear, and 2) downdraft development. The product of the vertical shear and the horizontal gradient of the downdraft determine the strength of the vorticity couplet and hence the extent of the echo deformation. Since the environmental shear is often weak with an airmass thunderstorm, a strong downdraft is required to form a strong vorticity couplet. This may be why a CBE is often associated with strong wind events.
Abstract
Multiplatform observations of Hurricane Rita (2005) were collected as part of the Hurricane Rainband and Intensity Change Experiment (RAINEX) field campaign during a concentric eyewall stage of the storm’s life cycle that occurred during 21–22 September. Satellite, aircraft, dropwindsonde, and Doppler radar data are used here to examine the symmetric evolution of the hurricane as it underwent eyewall replacement.
During the approximately 1-day observation period, developing convection associated with the secondary eyewall became more symmetric and contracted inward. Latent heating in the emergent secondary eyewall led to the development of a distinct toroidal (overturning) circulation with inertially constrained radial inflow above the boundary layer and compensating subsidence in the moat region, properties that are consistent broadly with the balanced vortex response to an imposed ring of diabatic heating outside the primary eyewall. The primary eyewall’s convection became more asymmetric during the observation period, but the primary eyewall was still the dominant swirling wind and vorticity structure throughout the period.
The observed structure and evolution of Rita’s secondary eyewall suggest that spinup of the tangential winds occurred both within and above the boundary layer, and that both balanced and unbalanced dynamical processes played an important role. Although Rita’s core intensity decreased during the observation period, the observations indicate a 125% increase in areal extent of hurricane-force winds and a 19% increase in integrated kinetic energy resulting from the eyewall replacement.
Abstract
Multiplatform observations of Hurricane Rita (2005) were collected as part of the Hurricane Rainband and Intensity Change Experiment (RAINEX) field campaign during a concentric eyewall stage of the storm’s life cycle that occurred during 21–22 September. Satellite, aircraft, dropwindsonde, and Doppler radar data are used here to examine the symmetric evolution of the hurricane as it underwent eyewall replacement.
During the approximately 1-day observation period, developing convection associated with the secondary eyewall became more symmetric and contracted inward. Latent heating in the emergent secondary eyewall led to the development of a distinct toroidal (overturning) circulation with inertially constrained radial inflow above the boundary layer and compensating subsidence in the moat region, properties that are consistent broadly with the balanced vortex response to an imposed ring of diabatic heating outside the primary eyewall. The primary eyewall’s convection became more asymmetric during the observation period, but the primary eyewall was still the dominant swirling wind and vorticity structure throughout the period.
The observed structure and evolution of Rita’s secondary eyewall suggest that spinup of the tangential winds occurred both within and above the boundary layer, and that both balanced and unbalanced dynamical processes played an important role. Although Rita’s core intensity decreased during the observation period, the observations indicate a 125% increase in areal extent of hurricane-force winds and a 19% increase in integrated kinetic energy resulting from the eyewall replacement.
Abstract
The Weather Research and Forecasting Model and its four-dimensional variational data assimilation (4DVAR) system are employed to examine the impact of airborne Doppler radar observations on predicting the genesis of Typhoon Nuri (2008). Electra Doppler Radar (ELDORA) airborne radar data, collected during the Office of Naval Research–sponsored Tropical Cyclone Structure 2008 field experiment, are used for data assimilation experiments. Two assimilation methods are evaluated and compared, namely, the direct assimilation of radar-measured radial velocity and the assimilation of three-dimensional wind analysis derived from the radar radial velocity. Results show that direct assimilation of radar radial velocity leads to better intensity forecasts, as this process enhances the development of convective systems and improves the inner-core structure of Nuri, whereas assimilation of the radar-retrieved wind analysis is more beneficial for tracking forecasts, as it results in improved environmental flows. The assimilation of both the radar-retrieved wind and the radial velocity can lead to better forecasts in both intensity and tracking, if the radial velocity observations are assimilated first and the retrieved winds are then assimilated in the same data assimilation window. In addition, experiments with and without radar data assimilation led to developing and nondeveloping disturbances in numerical simulations of Nuri’s genesis. The improved initial conditions and forecasts from the data assimilation imply that the enhanced midlevel vortex and moisture conditions are favorable for the development of deep convection in the center of the pouch and eventually contribute to Nuri’s genesis. The improved simulations of the convection and associated environmental conditions produce enhanced upper-level warming in the core region and lead to the drop in sea level pressure.
Abstract
The Weather Research and Forecasting Model and its four-dimensional variational data assimilation (4DVAR) system are employed to examine the impact of airborne Doppler radar observations on predicting the genesis of Typhoon Nuri (2008). Electra Doppler Radar (ELDORA) airborne radar data, collected during the Office of Naval Research–sponsored Tropical Cyclone Structure 2008 field experiment, are used for data assimilation experiments. Two assimilation methods are evaluated and compared, namely, the direct assimilation of radar-measured radial velocity and the assimilation of three-dimensional wind analysis derived from the radar radial velocity. Results show that direct assimilation of radar radial velocity leads to better intensity forecasts, as this process enhances the development of convective systems and improves the inner-core structure of Nuri, whereas assimilation of the radar-retrieved wind analysis is more beneficial for tracking forecasts, as it results in improved environmental flows. The assimilation of both the radar-retrieved wind and the radial velocity can lead to better forecasts in both intensity and tracking, if the radial velocity observations are assimilated first and the retrieved winds are then assimilated in the same data assimilation window. In addition, experiments with and without radar data assimilation led to developing and nondeveloping disturbances in numerical simulations of Nuri’s genesis. The improved initial conditions and forecasts from the data assimilation imply that the enhanced midlevel vortex and moisture conditions are favorable for the development of deep convection in the center of the pouch and eventually contribute to Nuri’s genesis. The improved simulations of the convection and associated environmental conditions produce enhanced upper-level warming in the core region and lead to the drop in sea level pressure.
Abstract
The development of airborne Doppler radars for atmospheric sciences research has vastly improved the ability to measure atmospheric storms. This paper addresses a new technique for improving airborne Doppler radar data quality. Assuming the earth's surface is flat and still, the technique uses the airborne radar measurements of the earth's surface reflectivity and velocity to correct for errors in navigation and radar pointing angles.
The methodology makes use of the helical scanning adopted in the existing systems onboard the two National Oceanic and Atmospheric Administration P3 aircraft and on the National Center for Atmospheric Research Electra aircraft (ELDORA/ASTRAIA radar). On the basis of a scan-by-scan analysis, it is shown that this methodology has the potential to retrieve most of the navigation errors, including errors in aircraft altitude, aircraft speed and drift, aircraft vertical velocity, aircraft pitch and roll, radar ranging error, and error in antenna spin angle. The methodology is demonstrated using a dataset obtained from ELDORA/ASTRAIA during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment. Analysis of these data shows it is possible to systematically correct for the navigation errors from a large dataset using a single set of corrections to the data.
Abstract
The development of airborne Doppler radars for atmospheric sciences research has vastly improved the ability to measure atmospheric storms. This paper addresses a new technique for improving airborne Doppler radar data quality. Assuming the earth's surface is flat and still, the technique uses the airborne radar measurements of the earth's surface reflectivity and velocity to correct for errors in navigation and radar pointing angles.
The methodology makes use of the helical scanning adopted in the existing systems onboard the two National Oceanic and Atmospheric Administration P3 aircraft and on the National Center for Atmospheric Research Electra aircraft (ELDORA/ASTRAIA radar). On the basis of a scan-by-scan analysis, it is shown that this methodology has the potential to retrieve most of the navigation errors, including errors in aircraft altitude, aircraft speed and drift, aircraft vertical velocity, aircraft pitch and roll, radar ranging error, and error in antenna spin angle. The methodology is demonstrated using a dataset obtained from ELDORA/ASTRAIA during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment. Analysis of these data shows it is possible to systematically correct for the navigation errors from a large dataset using a single set of corrections to the data.
Abstract
The concept and formulation of a real-time airborne Doppler radar wind field analysis technique, velocity track display (VTD), is presented. The VTD algorithm is a harmonic analysis method similar to the velocity–azimuth display technique for ground-based radars; however, it is designed to deduce the primary circulation properties of atmospheric vortices such as tropical cyclones. When an aircraft, equipped with a Doppler radar scanning in a track-orthogonal plane, penetrates a cyclonic circulation, VTD decomposes Doppler velocities on cylindrical rings into tangential, radial, and the mean cross-track component of the wind velocity. Obtaining estimates of the vortex circulation requires data from only one aircraft flight leg instead of two in the pseudo-dual Doppler radar method.
As a test, the VTD technique was applied to two orthogonal legs (“figure 4” pattern) in Hurricane Gloria (1985). The entire computation was completed about 15 min after the end of each flight leg with little or no human interaction. The reconstructed hurricane vortex structure (the mean tangential wind, mean radial wind, and the total tangential wind) is consistent with those documented in the literature by elaborate techniques that demand extensively interactive decisions and intensive computations. The output consists of about 4000 Fourier coefficients, which can be transmitted from an aircraft to a forecast center via geosynchronous satellite link in real-time for further analysis and as initialization for tropical cyclone models. A version of VTD was run successfully on board a NOAA WP-3D during the 1991 hurricane season.
Abstract
The concept and formulation of a real-time airborne Doppler radar wind field analysis technique, velocity track display (VTD), is presented. The VTD algorithm is a harmonic analysis method similar to the velocity–azimuth display technique for ground-based radars; however, it is designed to deduce the primary circulation properties of atmospheric vortices such as tropical cyclones. When an aircraft, equipped with a Doppler radar scanning in a track-orthogonal plane, penetrates a cyclonic circulation, VTD decomposes Doppler velocities on cylindrical rings into tangential, radial, and the mean cross-track component of the wind velocity. Obtaining estimates of the vortex circulation requires data from only one aircraft flight leg instead of two in the pseudo-dual Doppler radar method.
As a test, the VTD technique was applied to two orthogonal legs (“figure 4” pattern) in Hurricane Gloria (1985). The entire computation was completed about 15 min after the end of each flight leg with little or no human interaction. The reconstructed hurricane vortex structure (the mean tangential wind, mean radial wind, and the total tangential wind) is consistent with those documented in the literature by elaborate techniques that demand extensively interactive decisions and intensive computations. The output consists of about 4000 Fourier coefficients, which can be transmitted from an aircraft to a forecast center via geosynchronous satellite link in real-time for further analysis and as initialization for tropical cyclone models. A version of VTD was run successfully on board a NOAA WP-3D during the 1991 hurricane season.
Abstract
The navigation correction method proposed in Testud et al. (referred to as the THL method) systematically identifies uncertainties in the aircraft Inertial Navigation System and errors in the radar-pointing angles by analyzing the radar returns from a flat and stationary earth surface. This paper extends the THL study to address 1) error characteristics on the radar display, 2) sensitivity of the dual-Doppler analyses to navigation errors, 3) fine-tuning the navigation corrections for individual flight legs, and 4) identifying navigation corrections over a flat and nonstationary earth surface (e.g., ocean).
The results show that the errors in each of the parameters affect the dual-Doppler wind analyses and the first-order derivatives in different manners. The tilt error is the most difficult parameter to determine and has the greatest impact on the dual-Doppler analysis. The extended THL method can further reduce the drift, ground speed, and tilt errors in all flight legs over land by analyzing the residual velocities of the earth surface using the corrections obtained in the calibration legs.
When reliable dual-Doppler winds can be deduced at flight level, the Bosart–Lee–Wakimoto method presented here can identify all eight errors by satisfying three criteria: 1) the flight-level dual-Doppler winds near the aircraft are statistically consistent with the in situ winds, 2) the flight-level dual-Doppler winds are continuous across the flight track, and 3) the surface velocities of the left (right) fore radar have the same magnitude but opposite sign as their counterparts of right (left) aft radar. This procedure is able to correct airborne Doppler radar data over the ocean and has been evaluated using datasets collected during past experiments. Consistent calibration factors are obtained in multiple legs. The dual-Doppler analyses using the corrected data are statistically superior to those using uncorrected data.
Abstract
The navigation correction method proposed in Testud et al. (referred to as the THL method) systematically identifies uncertainties in the aircraft Inertial Navigation System and errors in the radar-pointing angles by analyzing the radar returns from a flat and stationary earth surface. This paper extends the THL study to address 1) error characteristics on the radar display, 2) sensitivity of the dual-Doppler analyses to navigation errors, 3) fine-tuning the navigation corrections for individual flight legs, and 4) identifying navigation corrections over a flat and nonstationary earth surface (e.g., ocean).
The results show that the errors in each of the parameters affect the dual-Doppler wind analyses and the first-order derivatives in different manners. The tilt error is the most difficult parameter to determine and has the greatest impact on the dual-Doppler analysis. The extended THL method can further reduce the drift, ground speed, and tilt errors in all flight legs over land by analyzing the residual velocities of the earth surface using the corrections obtained in the calibration legs.
When reliable dual-Doppler winds can be deduced at flight level, the Bosart–Lee–Wakimoto method presented here can identify all eight errors by satisfying three criteria: 1) the flight-level dual-Doppler winds near the aircraft are statistically consistent with the in situ winds, 2) the flight-level dual-Doppler winds are continuous across the flight track, and 3) the surface velocities of the left (right) fore radar have the same magnitude but opposite sign as their counterparts of right (left) aft radar. This procedure is able to correct airborne Doppler radar data over the ocean and has been evaluated using datasets collected during past experiments. Consistent calibration factors are obtained in multiple legs. The dual-Doppler analyses using the corrected data are statistically superior to those using uncorrected data.
Abstract
The concept and mathematical framework of the distance velocity–azimuth display (DVAD) methodology is presented. DVAD uses rV d (Doppler velocity scaled by the distance from the radar to a gate, r) as the basis to display, interpret, and extract information from single Doppler radar observations. Both linear and nonlinear wind fields can be represented by the same Cartesian polynomial with different orders. DVAD is mathematically concise and superior to the velocity–azimuth display (VAD) in interpreting and deducing flow characteristics. The rV d pattern of a two-dimensional linear wind field is exclusively in the form of a bivariate quadratic equation representing conic sections (e.g., ellipse, parabola, and hyperbola) centered at the radar depending only on divergence and deformation. The presence of a constant background flow translates the conic sections to a different origin away from the radar. It is possible to graphically estimate the characteristics of a linear wind field from the conical sections without performing a VAD analysis. DVAD analysis can deduce quantitative flow characteristics by a least squares fitting and/or a derivative method, and is a natural way to account for nonlinearity. The rV d pattern behaves similar to a type of velocity potential in fluid mechanics where ∇(rV d ) is a proxy of the true wind vector and is used to estimate the general flow pattern in the vicinity of the radar.
Abstract
The concept and mathematical framework of the distance velocity–azimuth display (DVAD) methodology is presented. DVAD uses rV d (Doppler velocity scaled by the distance from the radar to a gate, r) as the basis to display, interpret, and extract information from single Doppler radar observations. Both linear and nonlinear wind fields can be represented by the same Cartesian polynomial with different orders. DVAD is mathematically concise and superior to the velocity–azimuth display (VAD) in interpreting and deducing flow characteristics. The rV d pattern of a two-dimensional linear wind field is exclusively in the form of a bivariate quadratic equation representing conic sections (e.g., ellipse, parabola, and hyperbola) centered at the radar depending only on divergence and deformation. The presence of a constant background flow translates the conic sections to a different origin away from the radar. It is possible to graphically estimate the characteristics of a linear wind field from the conical sections without performing a VAD analysis. DVAD analysis can deduce quantitative flow characteristics by a least squares fitting and/or a derivative method, and is a natural way to account for nonlinearity. The rV d pattern behaves similar to a type of velocity potential in fluid mechanics where ∇(rV d ) is a proxy of the true wind vector and is used to estimate the general flow pattern in the vicinity of the radar.
Abstract
Dual-Doppler, polarimetric radar observations and precipitation efficiency (PE) calculations are used to analyze subtropical heavy rainfall events that occurred in southern Taiwan from 14 to 17 June 2008 during the Southwest Monsoon Experiment/Terrain-Influenced Monsoon Rainfall Experiment (SoWMEX/TiMREX) field campaign. Two different periods of distinct precipitation systems with diverse kinematic and microphysical characteristics were investigated: 1) prefrontal squall line (PFSL) and 2) southwesterly monsoon mesoscale convective system (SWMCS). The PFSL was accompanied by a low-level front-to-rear inflow and pronounced vertical wind shear. In contrast, the SWMCS had a low-level southwesterly rear-to-front flow with a uniform vertical wind field. The PFSL (SWMCS) contained high (low) lightning frequency associated with strong (moderate) updrafts and intense graupel–rain/graupel–small hail mixing (more snow and less graupel water content) above the freezing level. It is postulated that the reduced vertical wind shear and enhanced accretional growth of rain by high liquid water content at low levels in the SWMCS helped produce rainfall more efficiently (53.1%). On the contrary, the deeper convection of the PFSL had lower PE (45.0%) associated with the evaporative loss of rain and the upstream transport of liquid water to form larger stratiform regions. By studying these two events, the dependence of PE on the environmental and microphysical factors of subtropical heavy precipitation systems are investigated by observational data for the first time. Overall, the PE of the convective precipitation region (47.9%) from 14 to 17 June is similar to past studies of convective precipitation in tropical regions.
Abstract
Dual-Doppler, polarimetric radar observations and precipitation efficiency (PE) calculations are used to analyze subtropical heavy rainfall events that occurred in southern Taiwan from 14 to 17 June 2008 during the Southwest Monsoon Experiment/Terrain-Influenced Monsoon Rainfall Experiment (SoWMEX/TiMREX) field campaign. Two different periods of distinct precipitation systems with diverse kinematic and microphysical characteristics were investigated: 1) prefrontal squall line (PFSL) and 2) southwesterly monsoon mesoscale convective system (SWMCS). The PFSL was accompanied by a low-level front-to-rear inflow and pronounced vertical wind shear. In contrast, the SWMCS had a low-level southwesterly rear-to-front flow with a uniform vertical wind field. The PFSL (SWMCS) contained high (low) lightning frequency associated with strong (moderate) updrafts and intense graupel–rain/graupel–small hail mixing (more snow and less graupel water content) above the freezing level. It is postulated that the reduced vertical wind shear and enhanced accretional growth of rain by high liquid water content at low levels in the SWMCS helped produce rainfall more efficiently (53.1%). On the contrary, the deeper convection of the PFSL had lower PE (45.0%) associated with the evaporative loss of rain and the upstream transport of liquid water to form larger stratiform regions. By studying these two events, the dependence of PE on the environmental and microphysical factors of subtropical heavy precipitation systems are investigated by observational data for the first time. Overall, the PE of the convective precipitation region (47.9%) from 14 to 17 June is similar to past studies of convective precipitation in tropical regions.
Abstract
A quasi-linear convective line with a trailing stratiform region developed during the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX) while being sampled by two airborne Doppler radars. The finescale reflectivity and Doppler velocities recorded by the radars documented the evolution of the convective line. Bands of positive and negative vertical vorticity oriented parallel to the convective line were resolved in the analysis. This type of structure has rarely been reported in the literature and appears to be a result of the tilting and subsequent stretching of ambient horizontal vorticity produced by the low-level wind shear vector with a significant along-line component. The radar analysis also documented the evolution of an embedded bow echo within the convective line. Embedded bow echoes have been documented for a number of years; however, a detailed analysis of their kinematic structure has not been previously reported in the literature. The counterrotating circulation patterns that are characteristic of bow echoes appeared to be a result of tilting and stretching of the horizontal vorticity produced in the cold pool. The analysis suggests that the location along the convective line where embedded bow echoes form depends on the local depth of the cold pool. The rear-inflow jet is largely driven by the combined effects of the counterrotating vortices and the upshear-tilted updraft.
Abstract
A quasi-linear convective line with a trailing stratiform region developed during the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX) while being sampled by two airborne Doppler radars. The finescale reflectivity and Doppler velocities recorded by the radars documented the evolution of the convective line. Bands of positive and negative vertical vorticity oriented parallel to the convective line were resolved in the analysis. This type of structure has rarely been reported in the literature and appears to be a result of the tilting and subsequent stretching of ambient horizontal vorticity produced by the low-level wind shear vector with a significant along-line component. The radar analysis also documented the evolution of an embedded bow echo within the convective line. Embedded bow echoes have been documented for a number of years; however, a detailed analysis of their kinematic structure has not been previously reported in the literature. The counterrotating circulation patterns that are characteristic of bow echoes appeared to be a result of tilting and stretching of the horizontal vorticity produced in the cold pool. The analysis suggests that the location along the convective line where embedded bow echoes form depends on the local depth of the cold pool. The rear-inflow jet is largely driven by the combined effects of the counterrotating vortices and the upshear-tilted updraft.
Abstract
The impact of airborne Doppler radar data assimilation on improving numerical simulations of tropical cyclones (TCs) has been well recognized. However, the influence of radar data quality on the numerical simulation of tropical cyclones has not been given much attention. It is commonly assumed that higher quality radar data would be more beneficial to numerical simulations of TCs. This study examines the impact of the radar data quality control on assimilation of the airborne Doppler radar reflectivity and radial velocity observations in a numerical simulation of Typhoon Jangmi (2008). It is found that the quality of radar data has a strong influence on the numerical simulation of Typhoon Jangmi in terms of its track, intensity, and precipitation structures. Specifically, results suggest that a trade-off between the data quality and data coverage is necessary for different purposes in practical applications, as the higher quality data contribute to intensity forecast improvements, whereas data of lower quality but having better coverage are more beneficial to accurate track forecasting.
Abstract
The impact of airborne Doppler radar data assimilation on improving numerical simulations of tropical cyclones (TCs) has been well recognized. However, the influence of radar data quality on the numerical simulation of tropical cyclones has not been given much attention. It is commonly assumed that higher quality radar data would be more beneficial to numerical simulations of TCs. This study examines the impact of the radar data quality control on assimilation of the airborne Doppler radar reflectivity and radial velocity observations in a numerical simulation of Typhoon Jangmi (2008). It is found that the quality of radar data has a strong influence on the numerical simulation of Typhoon Jangmi in terms of its track, intensity, and precipitation structures. Specifically, results suggest that a trade-off between the data quality and data coverage is necessary for different purposes in practical applications, as the higher quality data contribute to intensity forecast improvements, whereas data of lower quality but having better coverage are more beneficial to accurate track forecasting.
