High-Resolution Simulation of Hurricane Bonnie (1998) High-Resolution Simulation of Hurricane Bonnie (1998). Part II: Water Budget 演講人:陳登舜 Braun, S. A., 2006: High-Resolution Simulation of Hurricane Bonnie (1998). Part II: Water Budget. J. Atmos. Sci., 63, 43-64.

Key words Water Budget, The requirement that the change in the amount of water stored in the atmosphere moving across a region should equal the difference between precipitation input to and evaporation loss from the underlying surface. (AMS ,glossary) CFADs,Contoured Frequency by Altitude Diagrams (CFADs)

Outline Introduction Simulation and analysis description a.Simulation description b.Simulated structure and validation Budget formulation Budget results a.Water vapor budget b.Condesed water budget c.Volume–integrated budget d.The artificial water source Conclusions

Introduction I The water vapor budget a. The condensation in the eyewall occurs convective hot towers b. Evaporation from the surface was approximately 20% and 25% of the condensation and total advection, respectively .(Kurihara’s 1975) c. Ocean source of water vapor was typically only about 6% - 13% of horizontal transport ( Hawkins and Imbembo 1976) d. in the eyewall the horizontal advection contribution was small compared to vertical advection. (Zhang et al. 2002)

Introduction II The condensation water budget a. Marks (1985) estimated that 60% of inner core-region rainfall of Hurricane Allen (1980) fell within stratiform rain areas and the water vapor convergence into this areas was more than twice the rainfall . b. the eyewall and stratifrom region ,analogous to tropical squall lines in which 30%-50% of precipitation falls out as outer region.( Marks and Houze 1987) c. it suggested that this localized outflow from the eyewall thus contributed significant amounts of ice for development of the stratiform precipitation.

Introduction III Horizontal advection tended to transport drier air into the core in the boundary layer and moist air from the eye to the eyewall within the low-level outflow above the boundary layer (Zhang et al. 2002). Outside of the eyewall the condensation occurs in weaker updrafts, indicative of a larger role of stratiform precipitation processes. In this study, we compute budgets of both water vapor and total condensed water (cloud condensate, and precipitation) from a high-resolution simulation of Hurricane Bonnie (1998).

Simulation and analysis description a. Simulation description Coarse-resolution: Started at 1200 UTC 22/08/1998 (36 hrs) 36 km: 91× 97 12 km: 160×160 High-resolution: Started at 1800 UTC 22/08/1998 (30 hrs) 6 km: 225×225 2 km: 226×226 Vertical: 27 levels

1800 UTC 22 Aug. TRMM 1050 UTC 24 Aug. TRMM 1200 UTC 23 Aug MM5 Too much rainwater mass occurs in the simulation

Radar Reflectivity CFAD Contoured Frequency by Altitude Diagrams (CFADs) 1800 UTC 22 Aug. TRMM 1200 UTC 23 Aug. MM5

40 m 2.7km Vr’ (contour) W (contour) 1-h Time Average (24-25 h) 6.8km C ) this shift occurs because of changes in the storm-relative environmental flow with height . D) This asymmetry is caused by the storm-relative flow associated with the environmental wind shear.

1-h Time Average (24-25 h) dBZ + w (qcl+qci) + w dBZ + Vr

tangential velocity radial velocity vertical velocity qv -0.3 g/kg 56ms-1 @750m vertical velocity qv -0.3 g/kg qrain, qsnow, qgr qcl + qci 0 oC

Budget Formulation local change horizontal flux divergence vertical flux divergence Divergence qv is mixing ratio of water vapor; qc is the mixing ratio of cloud liquid water and ice; qp is the mixing ratio of rain, snow and graupel; V’ is the storm-relative horizontal air motion; w is the vertical air motion; VT is the hydrometeor motion; + is source; - is sink; C is the condensation and deposition; E is the evaporation and sublimation; B is the contribution from the planetary boundary layer; D is the turbulent diffusion term; Z is the artificial source term associated with setting negative mixing ratios to zero. zero term surface precipitation flux Qc+ ,Qc- ,Qp+ ,and Qp- are the cloud and precipitation source and sink term

Budget Formulation(con’t) Zx is artificial source terms associated with setting negative mixing ratios (caused by errors associated with the finite differencing of the advective terms) to zero, that is, mass is added to eliminate negative mixing ratios. Dale R. Durran,2003

Budget Formulation(con’t) the temporal and azimuthal mean: (kg·m-3·h-1 ) the time-averaged and vertically integrated amount: (kg·m-2·h-1 ) the time-averaged, volumetrically integrated amount: (kg·h-1 ) the azimuthally averaged horizontal advective flux is simply that associated with radial transport

Budget results a. Water vapor budget 1-h Average (24-25 h) condensation horizontal flux divergence, Melting layer evaporation vertical flux divergence, Cond + Evap HF + VF divergence divergence term boundary layer source term DRY

much of the eyewall condensation is associated with hot towers. eyewall region (30-70 km) outer region (70-200 km) The percentage of the area The percentage of condensation occurring in updraft Updrafts greater than 2 m/s occupy somewhat less than 10% of the eyewall area at low to mid level, and produce 75% of the total condensation Updrafts greater than 4 m/s generally occupy less than 5% of the eyewall area, and account for almost half of the condensation. much of the eyewall condensation is associated with hot towers. The smaller contribution of stronger updrafts is indicative of the larger role of stratiform precipitation processes outside of the eyewall.

cloud budget b. Condensed water budget cloud sink horizontal flux divergence Evaporation; Autoconversion; Collection; net source condensation (total source of cloud) vertical flux divergence added water mass to offset negative mixing ratios boundary layer source Cloud liquid water Unlike in the water vapor , the flux divergence term is much smaller than the source/sink term

precipitation budget Source sink Warm-rain proc. Evaporation rain Melting layer graupel Melting snow Have a evaporation though the downdraft processes.

precipitation budget net microphysical source horizontal flux divergence precipitation fallout and vertical flux divergence cloud sink added water mass to offset negative mixing ratios

Horizontal distribution condensation evaporation downdraft precipitation fallout qv Only have slightly (a few tens of kilometers at most ) downwind of the condensation peak .

Displacement of the precipitation total rain source warm rain source Rain source + graupel sink cold rain source graupel source Graupel sink The two factors of displacement of the precipitation have only slightly downwind peak. The first factor is that much of the rainwater production in the eyewall occurs in association with warm rain processes. The second factors is that upward motion at upper levels is located on the western side of the storm

c.Volume–integrated budget Ocean source term of vapor which is only 4% of the low level radial import of moisture . The moisture convergence into the eyewall was more than twice the volumetric rainfall. Not all of the moisture converged into the eyewall is carried outward in the form of condensation . Almost 45% of total condensation is evaporated . The PBL source of vapor term is 8% of the low-level moisture import ,but 27% of the transport into the eyewall.

d. The artificial water source Cloud content Precipitation content cloud liquid water cloud ice rain snow graupel

cloud water rain graupel

Conclusion The simulation generally reproduces the track, intensity, and structure of the storm, but overpredicts the precipitation as inferred from comparison of model and TRMM radar reflectivities. The water vapor budget confirms that the ocean source of vapor in the eyewall region is very small relative to the condensation and inward transport of vapor, with the ocean vapor source in the eyewall (0.7) being approximately 4% of the inward vapor transport into the eyewall (16.8) region.

Conclusion In the eyewall, most of the condensation occurs within convective towers while in the outer regions condensation results from a mix of convective and stratiform precipitation processes. Precipitation processes acting outside of the eyewall region are not very dependent on the condensate mass produced within and transported outward from the eyewall. The artificial water mass source contribute an amount of water that is equivalent to 15%–20% of the total surface precipitation.

Typhoon Nari (2001) Water budget

Condensation Condensation Interval 2 g/m^3 h Bonnie 1998 Nari 2001

Evaporation Evaporation Interval 0.5 g/m^3 h Bonnie 1998 Nari 2001

Net Condensation Bonnie 1998 Net Condensation Interval 2 g/m^3 h Nari 2001

Horizontal Flux Divergence Bonnie 1998 Horizontal Flux Divergence Interval 20 g/m^3 h Horizontal Flux Divergence Interval 10 g/m^3 h Nari 2001

Vertical Flux Divergence Horizontal Flux Divergence Interval 20 g/m^3 h Bonnie 1998 Vertical Flux Divergence Interval 10 g/m^3 h Nari 2001

Total Flux Divergence Total Flux Divergence Interval 2 g/m^3 h Bonnie 1998 Total Flux Divergence Interval 1 g/m^3 h Nari 2001

Divergence Divergence Interval 0.5 g/m^3 h Bonnie 1998 Nari 2001

PBL Bonnie 1998 PBL Interval 0.5 g/m^3 h PBL Interval 0.5 g/m^3 h Nari 2001

Water Vapor Budget Bonnie 1998 Nari 2001

Liquid/Ice Water Budget Bonnie 1998 Nari 2001 Zero term =?? ??

Future Works 納莉與Bonnie在海上的water budget 大致上有一致的結果，但eyewall 區域降水偏少，目前還在檢查程式，待解決降水偏少的問題就可以計算出artificial zero term 的大小。 未來還要針對在陸地上做納莉颱風的water budget，我們預期會相較於海上還要造成更多的降水。 藉此我們就可以充分暸解在，颱風與地形的交互作用下，各項降水粒子的分佈。

Model Setup Model Domain Levels Microphysics PBL Radiation IC BC MM5, version 3.4; Dudhia1933; Grell et al. 1995 Domain D1 : 36 km (91 x 97) ; D2 : 12 km (160 x 160) two-way Levels 27 half sigma levels, model top is 50 hPa Microphysics Goddard (Tao and Simpson 1993; McCumber et al. 1991) PBL Blackadar PBL (Blackadar 1979; Zhang and Anthes 1982) Radiation Rapid Radiative Transfer Model (RRTM) long wave (Mlawer et al. 1997 ) and Dudhia short wave scheme (Dudhia 1989) IC 12-hourly global analyses from the ECMWF archived BC

dBZ (shading) W (contour) Qc+Qi (shading) W (contour) dBZ (shading) Vr’ (contour) 1-h Time Average (24-25 h)

In the outer region the PBL source of vapor term is about 8% of the low-level moisture import ,but 27% of the transport into the eyewall. About 70% of the condensate falls to the surface as precipitation. The outward transport of condensate aloft is about 9% of eyewall condensation The precipitation efficiency is about 65% ,and artificial term is about 13% of condensation in both region.