Improved Climatology of Tropical Cyclone Precipitation from Satellite Passive Microwave Measurements

2021 ◽  
pp. 1-42
Author(s):  
Song Yang ◽  
Vincent Lao ◽  
Richard Bankert ◽  
Timothy R. Whitcomb ◽  
Joshua Cossuth
Keyword(s):  
Tropical Cyclone ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
Passive Microwave ◽  
Shear Direction ◽  
Tropical Depression ◽  
Contraction Process ◽  
Concentric Pattern ◽  
Microwave Sensors ◽  
Left Quadrant

AbstractAccurate precipitation climatology is presented for tropical depression (TD), tropical storm (TS), and tropical cyclone (TC) over oceans using the recently-released, consistent and high quality precipitation datasets from all passive microwave sensors covering 1998-2012 along with the Automated Rotational Center Hurricane Eye Retrieval (ARCHER)-based TC center positions. Impacts with respect to the direction of both TC movement and the 200-850 hPa wind shear on the spatial distributions of TC precipitation are analyzed. The TC eyewall contraction process during its intensification is noted by a decrease in the radius of maximum rainrate with an increase in TC intensity. For global TCs, the maximum rainrate with respect to the direction of TC movement is located in the down-motion quadrants for TD, TS, and Cat 1-3 TCs, and in a concentric pattern for Cat 4-5 TCs. A consistent maximum TC precipitation with respect to the direction of the 200-850 hPa wind shear is shown in the down shear left quadrant (DSLQ). With respect to direction of TC movement, spatial patterns of TC precipitation vary with basins and show different features for weak and strong storms. The maximum rainrate is always located in DSLQ for all TC categories and basins, except the Southern Hemisphere basin where it is in the down shear right quadrant (DSRQ). This study not only confirms previously published results on TC precipitation distributions relative to vertical wind shear direction, but also provides a detailed distribution for each TC category and TS, while TD storms display an enhanced rainfall rate ahead of the down shear quadrants.

scholarly journals Tropical Cyclone Climatology from Satellite Passive Microwave Measurements

2020 ◽  
Vol 12 (21) ◽  
pp. 3610
Author(s):  
Song Yang ◽  
Richard Bankert ◽  
Joshua Cossuth
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
Passive Microwave ◽  
Vertical Wind ◽  
Vertical Shear ◽  
Shear Direction ◽  
Motion Direction ◽  
Horizontal Structure

The satellite passive microwave (PMW) sensor brightness temperatures (TBs) of all tropical cyclones (TCs) from 1987–2012 have been carefully calibrated for inter-sensor frequency differences, center position fixing using the Automated Rotational Center Hurricane Eye Retrieval (ARCHER) scheme, and application of the Backus–Gilbert interpolation scheme for better presentation of the TC horizontal structure. With additional storm motion direction and the 200–850 hPa wind shear direction, a unique and comprehensive TC database is created for this study. A reliable and detailed climatology for each TC category is analyzed and discussed. There is significant annual variability of the number of storms at hurricane intensity, but the annual number of all storms is relatively stable. Results based on the analysis of the 89 GHz horizontal polarization TBs over oceans are presented in this study. An eyewall contraction is clearly displayed with an increase in TC intensity. Three composition schemes are applied to present a reliable and detailed TC climatology at each intensity category and its geographic characteristics. The global composition relative to the North direction is not able to lead a realistic structure for an individual TC. Enhanced convection in the down-motion quadrants relative to direction of TC motion is obvious for Cat 1–3 TCs, while Cat 4–5 TCs still have a concentric pattern of convection within 200 km radius. Regional differences are evident for weak storms. Results indicate the direction of TC movement has more impact on weak storms than on Cat 4–5 TCs. A striking feature is that all TCs have a consistent pattern of minimum TBs at 89 GHz in the downshear left quadrant (DSLQ) for the northern hemisphere basins and in the downshear right quadrant (DSRQ) for the southern hemisphere basin, regarding the direction of the 200–850 hPa wind shear. Tropical depression and tropical storm have the minimum TBs in the downshear quadrants. The axis of the minimum TBs is slightly shifted toward the vertical shear direction. There is no geographic variation of storm structure relative to the vertical wind shear direction except over the southern hemisphere which shows a mirror image of the storm structure over the northern hemisphere. This study indicates that regional variation of storm structure relative to storm motion direction is mainly due to differences of the vertical wind shear direction among these basins. Results demonstrate the direction of the 200–850 hPa wind shear plays a critical role in TC structure.

scholarly journals Examination of Surface Wind Asymmetries in Tropical Cyclones. Part I: General Structure and Wind Shear Impacts

2017 ◽  
Vol 145 (10) ◽  
pp. 3989-4009 ◽  
Author(s):  
Bradley W. Klotz ◽  
Haiyan Jiang
Keyword(s):  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
Wind Shear ◽  
General Structure ◽  
Surface Wind ◽  
Vertical Wind Shear ◽  
Momentum Transport ◽  
Analysis Tool ◽  
Shear Direction ◽  
Motion Direction

Because surface wind speeds within tropical cyclones are important for operational and research interests, it is vital to understand surface wind structure in relation to various storm and environmental influences. In this study, global rain-corrected scatterometer winds are used to quantify and evaluate characteristics of tropical cyclone surface wind asymmetries using a modified version of a proven aircraft-based low-wavenumber analysis tool. The globally expanded surface wind dataset provides an avenue for a robust statistical analysis of the changes in structure due to tropical cyclone intensity, deep-layer vertical wind shear, and wind shear’s relationship with forward storm motion. A presentation of the quantified asymmetry indicates that wind shear has a significant influence on tropical storms at all radii but only for areas away from the radius of maximum wind in both nonmajor and major hurricanes. Evaluation of a shear’s directional relation to motion indicates that a cyclonic rotation of the surface wind field asymmetry from downshear left to upshear left occurs in conjunction with an anticyclonic rotation of the directional relationship (i.e., from shear direction to the left, same, right, or opposite of the motion direction). It was discovered that in tropical cyclones experiencing effects from wind shear, an increase in absolute angular momentum transport occurs downshear and often downshear right. The surface wind speed low-wavenumber maximum in turn forms downwind of this momentum transport.

scholarly journals Idealized Tropical Cyclone Responses to the Height and Depth of Environmental Vertical Wind Shear

2016 ◽  
Vol 144 (6) ◽  
pp. 2155-2175 ◽  
Author(s):  
Peter M. Finocchio ◽  
Sharanya J. Majumdar ◽  
David S. Nolan ◽  
Mohamed Iskandarani
Keyword(s):  
Tropical Cyclone ◽  
Wind Shear ◽  
Large Scale ◽  
Deep Layer ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Polynomial Expansions ◽  
The Impact ◽  
Tilt Response ◽  
Left Quadrant

Abstract Three sets of idealized, cloud-resolving simulations are performed to investigate the sensitivity of tropical cyclone (TC) structure and intensity to the height and depth of environmental vertical wind shear. In the first two sets of simulations, shear height and depth are varied independently; in the third set, orthogonal polynomial expansions are used to facilitate a joint sensitivity analysis. Despite all simulations having the same westerly deep-layer (200–850 hPa) shear of 10 m s−1, different intensity and structural evolutions are observed, suggesting the deep-layer shear alone may not be sufficient for understanding or predicting the impact of vertical wind shear on TCs. In general, vertical wind shear that is shallower and lower in the troposphere is more destructive to model TCs because it tilts the TC vortex farther into the downshear-left quadrant. The vortices that tilt the most are unable to precess upshear and realign, resulting in their failure to intensify. Shear height appears to modulate this tilt response by modifying the thermodynamic environment above the developing vortex early in the simulations, while shear depth modulates the tilt response by controlling the vertical extent of the convective vortex. It is also found that TC intensity predictability is reduced in a narrow range of shear heights and depths. This result underscores the importance of accurately observing the large-scale environmental flow for improving TC intensity forecasts, and for anticipating when such forecasts are likely to have large errors.

Examination of the Combined Effect of Deep-layer Vertical Shear Direction and Lower-Tropospheric Mean Flow on Tropical Cyclone Intensity and Size Based on the ERA5 Reanalysis

2021 ◽  
Author(s):  
Buo-Fu Chen ◽  
Christopher A. Davis ◽  
Ying-Hwa Kuo
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Vertical Wind Shear ◽  
Reanalysis Data ◽  
Vertical Shear ◽  
Shear Direction ◽  
Mean Flow ◽  
Representative Subset ◽  
Favorable Conditions ◽  
The Relationship

AbstractIdealized numerical studies have suggested that in addition to vertical wind shear (VWS) magnitude, the VWS profile also affects tropical cyclone (TC) development. A way to further understand the VWS profile’s effect is to examine the interaction between a TC and various shear-relative low-level mean flow (LMF) orientations. This study mainly uses the ERA5 reanalysis to verify that, consistent with idealized simulations, boundary-layer processes associated with different shear-relative LMF orientations affect real-world TC’s intensity and size. Based on analyses of 720 TCs from multiple basins during 2004–2016, a TC affected by an LMF directed toward downshear-left in the Northern Hemisphere favors intensification, whereas an LMF directed toward upshear-right is favorable for expansion. Furthermore, physical processes associated with shear-relative LMF orientation may also partly explain the relationship between the VWS direction and TC development, as there is a correlation between the two variables.The analysis of reanalysis data provides other new insights. The relationship between shear-relative LMF and intensification is not significantly modified by other factors [inner-core sea surface temperature (SST), VWS magnitude, and relative humidity (RH)]. However, the relationship regarding expansion is partly attributed to environmental SST and RH variations for various LMF orientations. Moreover, SST is critical to the basin-dependent variability of the relationship between the shear-relative LMF and intensification. For Atlantic TCs, the relationship between LMF orientation and intensification is inconsistent with all-basin statistics unless the analysis is restricted to a representative subset of samples associated with generally favorable conditions.

scholarly journals Multidecadal Variability of Tropical Cyclone Rapid Intensification in the Western North Pacific

2015 ◽  
Vol 28 (9) ◽  
pp. 3806-3820 ◽  
Author(s):  
Xidong Wang ◽  
Chunzai Wang ◽  
Liping Zhang ◽  
Xin Wang
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Wind Shear ◽  
Western North Pacific ◽  
Large Scale ◽  
Vertical Wind Shear ◽  
Trade Wind ◽  
Rapid Intensification ◽  
Multidecadal Variability ◽  
Heat Potential

Abstract This study investigates the variation of tropical cyclone (TC) rapid intensification (RI) in the western North Pacific (WNP) and its relationship with large-scale climate variability. RI events have exhibited strikingly multidecadal variability. During the warm (cold) phase of the Pacific decadal oscillation (PDO), the annual RI number is generally lower (higher) and the average location of RI occurrence tends to shift southeastward (northwestward). The multidecadal variations of RI are associated with the variations of large-scale ocean and atmosphere variables such as sea surface temperature (SST), tropical cyclone heat potential (TCHP), relative humidity (RHUM), and vertical wind shear (VWS). It is shown that their variations on multidecadal time scales depend on the evolution of the PDO phase. The easterly trade wind is strengthened during the cold PDO phase at low levels, which tends to make equatorial warm water spread northward into the main RI region rsulting from meridional ocean advection associated with Ekman transport. Simultaneously, an anticyclonic wind anomaly is formed in the subtropical gyre of the WNP. This therefore may deepen the depth of the 26°C isotherm and directly increase TCHP over the main RI region. These thermodynamic effects associated with the cold PDO phase greatly support RI occurrence. The reverse is true during the warm PDO phase. The results also indicate that the VWS variability in the low wind shear zone along the monsoon trough may not be critical for the multidecadal modulation of RI events.

scholarly journals Low Level Jet Wind Shear in the Sahel

2013 ◽  
Vol 11 ◽  
pp. 1-10
Author(s):  
Saïdou Madougou ◽  
Frederique Saïd ◽  
Bernard Campistron ◽  
Fadel Kebe Cheikh
Keyword(s):  
Wind Shear ◽  
Vertical Wind Shear ◽  
Shear Direction ◽  
Low Level ◽  
Aircraft Navigation ◽  
Time Period ◽  
Wind Profiler Radar ◽  
Low Level Jet ◽  
Wind Shears ◽  
Uhf Wind Profiler

In the Sahel, a vertical wind shear appears in the dry and in the wet seasons. In Niamey, Niger, during the dry season, the period of strong shears is clearly linked to the Nocturnal Low Level Jet (LLJ) since it occurs in a narrow time period around 06H00 UTC at 60% of the cases reach shears which require an alert to the pilots (higher than 4 ms-1 per 100 m). The majority of cases occur during the night with a wind shear direction between 90 and 150° per 100 m, which is shown that it is dangerous for aircraft. In Bamako, Mali, high wind shears represent (higher than 4 ms-1 per 100 m) only 16-22% of the cases and can occur at any time of the day. There are, however, 8% of the cases, the whole day long, when the wind shear can reach more than 6 ms-1 per 100 m. Most of the wind shear directions are also between 0 and 90° per 100 m during the night. This is why the Agency for the safety of aircraft navigation in Africa and Madagascar (ASECNA) has put in 2004 at Bamako airport an UHF wind profiler radar for monitoring nocturnal strong Low Level Jet wind shear which occur regularly in this airport.

scholarly journals Environmental Factors Affecting Tropical Cyclone Power Dissipation

2007 ◽  
Vol 20 (22) ◽  
pp. 5497-5509 ◽  
Author(s):  
Kerry Emanuel
Keyword(s):  
Tropical Cyclone ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Time Scales ◽  
North Pacific ◽  
Wind Shear ◽  
Western North Pacific ◽  
Vertical Wind Shear ◽  
Sea Surface ◽  
Strongly Correlated

Abstract Revised estimates of kinetic energy production by tropical cyclones in the Atlantic and western North Pacific are presented. These show considerable variability on interannual-to-multidecadal time scales. In the Atlantic, variability on time scales of a few years and more is strongly correlated with tropical Atlantic sea surface temperature, while in the western North Pacific, this correlation, while still present, is considerably weaker. Using a combination of basic theory and empirical statistical analysis, it is shown that much of the variability in both ocean basins can be explained by variations in potential intensity, low-level vorticity, and vertical wind shear. Potential intensity variations are in turn factored into components related to variations in net surface radiation, thermodynamic efficiency, and average surface wind speed. In the Atlantic, potential intensity, low-level vorticity, and vertical wind shear strongly covary and are also highly correlated with sea surface temperature, at least during the period in which reanalysis products are considered reliable. In the Pacific, the three factors are not strongly correlated. The relative contributions of the three factors are quantified, and implications for future trends and variability of tropical cyclone activity are discussed.

scholarly journals The Influence of Uniform Flow on Tropical Cyclone Intensity Change

2005 ◽  
Vol 62 (9) ◽  
pp. 3193-3212 ◽  
Author(s):  
Joey H. Y. Kwok ◽  
Johnny C. L. Chan
Keyword(s):  
Tropical Cyclone ◽  
Wind Shear ◽  
Mesoscale Model ◽  
Vertical Wind Shear ◽  
Lower Troposphere ◽  
Vertical Motion ◽  
Uniform Flow ◽  
Vertical Wind ◽  
Intensity Change ◽  
Westerly Flow

Abstract The influence of a uniform flow on the structural changes of a tropical cyclone (TC) is investigated using the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5). Idealized experiments are performed on either an f plane or a β plane. A strong uniform flow on an f plane results in a weaker vortex due to the development of a vertical wind shear induced by the asymmetric vertical motion and a rotation of upper-level anticyclone. The asymmetric vertical motion also reduces the secondary circulation of the vortex. On a β plane with no flow, a broad anticyclonic flow is found to the southeast of the vortex, which expands with time. Similar to the f-plane case, asymmetric vertical motion and vertical wind shear are also found. This beta-induced shear weakens the no-flow case significantly relative to that on an f plane. When a uniform flow is imposed on a β plane, an easterly flow produces a stronger asymmetry whereas a westerly flow reduces it. In addition, an easterly uniform flow tends to strengthen the beta-induced shear whereas a westerly flow appears to reduce it by altering the magnitude and direction of the shear vector. As a result, a westerly flow enhances TC development while an easterly flow reduces it. The vortex tilt and midlevel warming found in this study agree with the previous investigations of vertical wind shear. A strong uniform flow with a constant f results in a tilted and deformed potential vorticity at the upper levels. For a variable f, such tilting is more pronounced for a vortex in an easterly flow, while a westerly flow reduces the tilt. In addition, the vortex tilt appears to be related to the midlevel warming such that the warm core in the lower troposphere cannot extent upward, which leads to the subsequent weakening of the TC.

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