East Asia and Western Pacific METEOROLOGY AND CLIMATE

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81 appreciable intensity throughout their life span. They regard this to be due to weaker upper-air flow in this region. Besides they also point out that the size and orientation of the mountains are important for the generation and modification of lee cyclones, as well as the motion and intensification of cyclones. Using the Winter Monex data to study the period of 19-21 February 1979 over the lee side of the Tibetan plateau, Chen (1985) points out that Yun-Gui lee cyclogenesis of Feb. 19 was a hydrostatic response to the subsidence warming in the lower-and mid-troposphere when the temperature tendency by warm advection was roughly counteracted by the diabatic cooling process. At the same time, the secondary vertical circulation associated with the upper-level jet streak was suggested to have some contribution to the subsidence over the cyclogenesis area in addition to the leeside orographic effect. Jen (1987) studies the same case with the use of isentropic potential vorticity (IPV) analysis. He points out that the stretching of IPV in the lee side of the Tibetan plateau, if in phase with low-level warm vorticity, can cause a phase-lock and intensify the cyclogenetic process. The purpose of this study is to use a numerical model to study the Yun-Gui lee-cyclogenetic mechanisms. The hemispheric spectral model and its physical processes will be briefly described in section 2. Section 3 presents the synoptic analysis of Yun-Gui lee-cyclogenesis during 19 to 21 Feb. 1979, and the results of numerical model simulations. Section 4 provides the discussion of the results. 2. The hemispheric spectral model The equations and framework of the numerical model used in this study are described in Brenner et al. (1982) and Brenner et al. (1984). A brief description will be provided here as background. This is a spectral model with 12 layers and rhomboidally truncated at wavenumber 30. The prognostic equations are vorticity, divergence, temperature, specific humidity, and the logarithm of the surface pressure (continuity equation). The vorticity and divergence are given conventionally as Laplacians of a streamfunction and velocity potential respectively. The velocity components and geopotential are obtained diagnostically with the aid of the hydrostatic relation. The vertical coordinate of the model is cr=P/P*, defined by Phillips (1959), with a specification of layer locations described by Brown (1974) and Phillips (1975). The numerical methods in the model include spectral representation in the horizontal, the Arakawa quadratic conserving finite differencing in the vertical, and the semi-implicit time integration scheme. The nonlinear normal mode initialization technique developed by Machenhauer (1977), which is
82 implemented to the global model by Ballish (1980), is applied to adjust the input data. In this procedure, the data are projected onto the normal modes of the model and separated into the rotational (or Rossby) modes and the gravity modes. The gravity modes are adjusted in such a way that the linear tendency terms are balanced by the adiabatic nonlinear advective terms, thus resulting in a net initial gravity wave tendency of zero. The physical effects included in the model are the influences of orography, position-dependent surface friction, moisture physics, and sub-scale horizontal dissipation, parameterized by diffusion. Evaporation and sensible heat flux from the oceans are also included. The application of the moisture physics consists of a sequence of three steps to adjust the temperature and specific humidity. Each step possesses a characteristic spatial scale: (1) cumulus convection in a conditionally unstable, generally unsaturated large-scale flow, (2) large-scale condensaton in stable, saturated large-scale flow, and (3) dry convection in unstable, unsaturated large-scale flow. 3. The simulations of Yun-Gui cyclogenesis: 3.1 Data: The data used in this study are taken from the FGGE Level III-B data from 12 GMT Feb. 19 to 00 GMT Feb. 21, 1979. The input data for the numerical model includes winds and geopotential height (from 1000mb to 500mb) at 12 layers and moisture field (from 1000mb to 300mb) at 6 layers at 12 GMT Feb. 19 and 00 GMT Feb. 20 respectively. 3.2 Synoptic situation: The synoptic situation during this period will be described briefly in the following: In the 850mb analysis (Fig. 1) we can find a low pressure trough around the Yun- Gui area at 12 GMT Feb. 19. This trough the intensified for the next 36 hours. At the same time, southwesterly warm advection prevailed over southern China which caused unusually warm weather over the Taiwan area. For the 500mb synoptic chart (Fig. 2) we can see a warm ridge located around the Yun-Gui area at 00.GMT Feb. 20 and a weak trough around 105° E, 23 0 E-30°N. This trough continued to deepen for the next 12 hours. At 300mb the flow was generally from the west-northwest over the Yun-Gui plateau during this period. We also do the vorticity analysis for this case. Fig. 3 shows the vorticity field at 850mb. At 12 GMT Feb. 19 there exists a weak positive vorticity
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UNIVERSITY OF HONG KOHG LlBEAEY
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International Conference on East As
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FOREWORD The International Conferen
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VHI LIST OF PARTICIPANTS IN THE PHO
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45 LIM, Hock National University of
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XIII INTERNATIONAL ORGANIZING COMMI
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XV! The mean heat sources over Asia
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XVIII , Jhe impact of urbanization
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XX The East Asia heavy rainfall num
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THE THERMAL STRUCTURE AND CONVECTIV
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THE COUPLING OF UPPER-LEVEL AND LOW
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Q \ ed atmospheric processes * 2. M
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2) DH Experiment The horizontal flo
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of the orography, establishing a na
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11 a o 12 21 36 4$ 60 fZ Pig.3. Nea
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14 OVERVIB/V CF MEI-YU RESEARCH IN
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16 Fig.l Climatological daily rainf
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18 showed a marked contrast between
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20 3. SWDPTiC ^mLYSIS WD DIA^DSTIC
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22 and Chang (27). It was also foun
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24 triggering mechanisms. In additi
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26 important mechanism for creating
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28 mature convections. Satellite pi
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Page 57 and 58: 34 19.Chen, G.T. J., "A study on sy
Page 59 and 60: 36 complexes: 27-28 May 1981 case",
Page 61 and 62: 38 On Temporal Variations of Low Le
Page 63 and 64: 40 low-level flows of the Asian sum
Page 65 and 66: 42 the northern part of the Pacific
Page 67 and 68: 44 cycle is observed for the amplit
Page 69 and 70: 46 SUMMER (6-85 : 12 2 M979 P:850 M
Page 71 and 72: Observed Structure and Propagation
Page 73 and 74: 50 southeasterly current in the wes
Page 75 and 76: 40°N 30°N 15°N Equator 90°E 105
Page 77 and 78: 54 The pattern of arrows in Fig. 3
Page 79 and 80: 56 Figure 5. Vertical cross-section
Page 81 and 82: 58 TOE MEAN HEAT SOURCES OVER ASIAN
Page 83 and 84: 60 over tost parts of India, Southe
Page 85 and 86: 62 inctly different types. One is t
Page 87 and 88: 64 60 70 too no 120 00
Page 89 and 90: Fig.2.The 7-month mean values of (a
Page 91 and 92: 68 A NUMERICAL SIMULATION OF THE ME
Page 93 and 94: 70 Synoptic circulation patterns fo
Page 95 and 96: 72 (iii) The mid-latitude westerlie
Page 97 and 98: 74 and the temperate latitude weste
Page 99 and 100: 76 O 1 - (b) Total I Rainf a" 4 0
Page 101 and 102: 78 LONGITUDE TIME WINOCROS5 SECTION
Page 103: A simulation of Lee-Cyclogenesis ov
Page 107 and 108: 84 In all three experiments, a deep
Page 109: 86 References: Ballish, A.B., 1980:
Page 116 and 117: 93 1.2-a I2.S 120. 127,5 US. 11.5 7
Page 118 and 119: 95 2. Climatology of East Asian mon
Page 120 and 121: 97 850 MB WIND (U*. V) S. 0 30N i~^
Page 122 and 123: 99 120 ISO ISO 210 2VJ 770 ISO 180
Page 124 and 125: Figure 6 (a) Time-longitude section
Page 126 and 127: 103 Monsoon cyclones /-~N I Subtrop
Page 128 and 129: 105 INFLUENCE OF VARIATIONS OF THE
Page 130 and 131: surface during the rainy period of
Page 132 and 133: located at the position of the firs
Page 134 and 135: egion of western Australia. These t
Page 138: 115 Fig.^57 Characteristics of vari
Page 142 and 143: 119 Some Dynamic Aspects of the Equ
Page 144 and 145: 121 equatorial zonal plane. In this
Page 146 and 147: 123 where N is nondimensional Newto
Page 148 and 149: 125 moisture concentration graduall
Page 150 and 151: 127 boundary layer frictional conve
Page 152 and 153: 129 000 - 20 30 WAVELENGTH (10 3 KM
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131 CHINESE POLAR ORBITING METEOROL
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some middle and small receiving sta
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135 local meteorology units through
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140 The Mesoscale Monitoring System
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142 The weather radar network is co
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144 where V and L are in centimeter
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146 PRF: 80-2000 Hz Minimum detecta
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148 [UHF Doppler RadaT] ^Pibalk ' Z
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150 STRUCTURAL FEATURES OF A SQUALL
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152 25 2200L 16 MAY 0000 L 17 MAY X
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154 0*73 KN 0,73 KM TAMEX IOF2 00*1
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156 4.2 East-west Cross Section The
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158 KM -20 EAST OF TOGA -10 0043 28
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160 Radar Observation of Precipitat
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162 Fig. 2. A triple doppler networ
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164 for this presentation Fig. 5a(0
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166 near the northern tip of Taiwan
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168 In order to understand the inte
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170 REMOTE SENSING OF ATMOSPHERIC C
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172 In the meantime, with the incre
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174 method (scanning frequency) and
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176 For sharp absorption lines, the
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178 [10]* Sun Jinhui, Qiu Jinhuan e
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180 COMPARISION OF RADAR ESTIMATES
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182 of 29 %). The Ra/Rg and the rel
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184 under 1) errors in estimating r
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186 Table 1. Summary of Ra/Rg for t
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188 FIGURE 3. CORRELATION COEFFICIE
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190 DOPPLER WEATHER RADAR OBSERVATI
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192 which are concerned about by th
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194 fly on schedule, take off and l
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196 and minus value. Fig. 4 is the
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198 REFERENCES 1. Donald Turnbull e
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200 evaporation, condensation, wind
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202 control valve which permits amp
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204 Table 1 Rainfall Records of a T
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206 various rainfall intensity shou
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208 c 400-- £ o "5 350 H — A —
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210 IMPACT OF HOURLY S-VISSR SATELL
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212 Fig. 1. Daily 1.200 UTC • 500
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I Fig. 2. GMS-3 IR picture taken at
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216 110E 20 115E 30. 20" X J 4o*N'\
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218 Fig. 7. Provisional best track
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220 PREDICTABILITY OF LOW FREQUENCY
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222 expressions that invoke the Mon
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224 b) A low frequency mode experim
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226 A CLOUD WAVE THEORY AND ITS APP
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228 heating indicating a substantia
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230 If N Fig. I, A schematic diagra
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232 2. A Quasi-Diabatic Geostrophic
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234 X can be q, £ c, v, or T. The
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236 On the basis of the preceding d
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238 west of the maximum cloud cover
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240 NORMAL MODES OF CLIMATOLOGICAL
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242 (1983) pointed out that simulat
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244 reach the top of model atmosphe
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246 is not clear in the tropics. Th
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248 Wang, J.-T., J.-W. Kim and W.L.
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250 (a) 30°N-30°S (January) (b) 3
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252 An Important element of the ear
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254 IOCS I02S 3SN Fig. 1 A general
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256 staion of LID (farmland in the
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258 start from October 1990 and end
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260 The measurements of surface rad
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262 Secular trends in urban tempera
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264 LONGTERM TEMPERATURE TRENDS AT
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266 Using these data sources It has
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268 (3) a nearly static phase where
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270 greater rate of increasing mini
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272 consistent with accepted theory
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274 RECENT APPLICATIONS OF THE PENN
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276 upward motion (Fig. Ib) of air
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278 Stauffer and Warner (1987) used
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280 observed precipitation rates fo
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282 coupled model system show that
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284 Baroclinic Instability of Modif
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286 Eq (2.4) corresponds to the con
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288 conventional Eady waves, except
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290 perturbations in Mode I remains
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292 5: Summary And Remarks Two diff
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294 INFLUENCES OF OROGRAPHY ON FLOW
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296 (13) The next step is to determ
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298 where „ = 1 - R a = - R 2>x c
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300 — -~ 1, thus the above relati
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302 The vertical velocity at the to
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304 THE MIGEOPHYSICS OF A MEI-YU CA
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306 O.Qg-m" 3 , which is probably d
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308 snowflakes aggregation generate
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310 (a) TRP.CK - 2 (1652 0 - 1711 0
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312 1987 6/16 17QSSO U 0.9 C 2 = 1.
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314 2. Heavy Rainfall Upstream of a
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316 accumulated rainfall amount on
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318 Figures 11 and 12 demonstrate t
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320 DEGREE K IT ( M/S ) QC (G/KG) -
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322 270 290 310 330 350 370 POTJEMP
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324 A primitive equation model was
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326 had already been affected by so
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328 I .011 I 1...J/1 l\l l-L-l L I
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330 «'.. Fig. 11 Same as Fig. 9 ex
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332 Mathiar, M. B., 1983: A quasi-L
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334 Long (1985), the maximum occure
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336 February 1979. It clearly indic
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338 Jiang H. M. and Jeng H. N., "Nu
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TEMP.GRAD.(C/100KM3 1979/2/04/OOZ 1
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TKANS.C1R. 9 1979/2/04/OE2 •; J97
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344 however, the sharp decrease in
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346 00 " XD 3 b D 3 aD b dD = [ N.
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348 heights. The median diameter an
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350 going on within the melting lay
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352 TRFICK - I (HIS 0 - H31 0J PR0B
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354 MONTHLY AND SEASONAL FORECASTS
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356 In another experiment, the heat
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358 4. CONCLUSION The forecasting e
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360 TABLE 1. COMPARISONS OF THE COR
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362 Fig. 3. Map of the correlation
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364 THE TELECONNECTION OF EQUATORIA
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366 3-*-j-] dag grid % ^Showing eve
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368 oBE (6) fl(uP) , fl(vP) ... 0(w
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370 the major tidal components over
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372 one meter. Most of the water le
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374 and Technology Advisory Group,
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376 INTRODUCTION In 1%6, Bjerknes,
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378 THE INTERANNUAL VARIABILITIES O
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380 current between 127° E—128°
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382 El Nino and Southern Oscillatio
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384 Fig.5. The ADCP measurements (s
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386 I. Introduction Climate is one
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388 specifically at the modeling an
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390 Even during the warm phase of t
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392 (iv) To investigate the morphol
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394 Change program under IGBP is a
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396 TABLE 1: PROCESSES TO BE STUDIE
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398 w / / / / / / / / /-"V / / Z Fi
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400 CHINA-JAPAN JOINT RESEARCH PROG
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402 eastward. In addition to mainta
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404 Processes of Hicroscale Air-Sea
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406 phase velocity; both ratios, th
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T i l l ! o I • GO 00 J Wind Velo
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410 Concluding Remarks In order to
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412 THE VARIATIONS OF THE SST IN TH
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414 maps, there is an extensive are
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416 Flg.1. Time series of the annua
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418 90 N 90 S|. . . 20E 20E Fig.3c.
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420 ON LABORATORY SIMULATION OF SEA
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422 EXPERIMENT: Only simple and eas
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424 With the ability to simulate co
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426 (5) Meroney, R.N., Cermak, J.E.
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428 Fig. 3 Composite Photograph of
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430 A detailed description of the m
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432 However, the schemes failed to
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434 REFERENCES Anderson, E. and A.
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436 Figure 2 Vertical structure of
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438 36 HOUR FORECAST MEAN SEA LEVEL
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440 al.,1984). In this paper, a gen
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442 where subscript x denotes u, v,
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444 AM AM PO- N3 A/i + N3' and NH--
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446 there is only a minor differenc
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448 Guo X.R.,Yan Z.H.,Zhang Y.L. an
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450 THE EAST ASIA HEAVY RAINFALL NU
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452 (described in section 2) carrie
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454 Fig. . 2. Validation of Tempera
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456 simulate the partly cloudy cond
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458 3.3 Nesting Run with 2 km Grids
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460 REFERENCES Bhumralker, C. M., 1
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462 The Impact of the Termination o
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464 and 45.8 km respectively, which
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466 relative to (P+O/2, they actual
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468 Chang, S. W., 1982: The ore-gra
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470 Table 3. 24-hour forecast error
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472 Initial Position Errors 1983-19
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474 A SPECTRAL MODEL FOR MEDIUM RAN
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476 where I p u = FC-
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478 given. This is treated separate
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480 predicted location is too far t
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482 Fig.2 Distribution of 24h preci
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484 LONG-RANGE FORECASTING OF TAIWA
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486 monsoon in east Asia and for co
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488 unfortunately are not integral
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Figure 1. SPECTRAL ANALYSIS FOR MAY
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492 TaUj.g_ji Multiple rnfjross i o
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494 THE NONLINEAR INTERACTION OF IN
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496 Burgers(l948) had put forward a
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498 From Eqs,(8), the necessary con
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500 In order to show quantitatively
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502 Multiple Equilibria Of a Therma
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504 For the two-level quasi-geostro
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506 The coefficients Z, T, H, and T
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508 just the stable Branch 7 for st
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510 REFERENCES Bolin, B., 1950: On
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512 STATIONARY SOLUTIONS WITH TOPOG
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514 ANNTTAL CYCLE OF 2TTT Fig. 7 An
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516 CISK modes have narrow axes of
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518 about one to three weeks. Predi
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520 first one. In his work, the lon
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522 The works mentioned are qualita
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524 [12] Wang, S.-W., Adv. in Atmos
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526 processes that give rise to a d
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528 3 Local energetics analysis The
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530 dominant waves of a local mode
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532 slightly longer than the length
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534 tends to induce a westerly jet
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536 TYPHOON FORMATION AND DEVELOPME
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538 influence of the mean wind prof
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540 3. Steady-State Solutions The p
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542 of maximum wind (Fig 7 c). This
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544 (A) b- l.O.(B) b- 0.8.(C) b- 0.
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546 b= 1.0,C= 0.03,0 = 120., T = 50
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548 tropical cyclones. Then, Shapir
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550 fine equation (2) will be used
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552 4) Cumulus vertical flux of hea
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554 Fig. 4 Same as Fig, 1, but for
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556 n=800 bPa and r **1. Now it is
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558 RRFKRRNCF Challa, M., and R. T,
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560 The limited-area forecast syste
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562 Our study is to obtain and anal
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564 coarse grid (Fig. 5). The struc
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566 ACCUMULATED PRECIPITATION Fig.
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569 AUTHOR INDEX ANTHES, Richard A.
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571 LIOU, Chi-Sann LIU, Cho-Teng LI
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