Climate Dynamics

, Volume 36, Issue 7–8, pp 1221–1237 | Cite as

Climatology of summer midtropospheric perturbations in the US northern plains. Part II: large-scale effects of the Rocky Mountains on genesis

Article

Abstract

Propagating convective storms across the US northern plains are often coupled with preexisting midtropospheric perturbations (MPs) initiated over the Rocky Mountains. A companion study (Part I) notes that such MPs occur most commonly at 12 UTC (early morning) and 00 UTC (late afternoon). Using a regional reanalysis and a general circulation model (GCM), this study investigates how such a bimodal distribution of the MP frequency is formed. The results point to two possible mechanisms working together while each has a different timing in terms of maximum effect. The diurnal evolutions between the midtropospheric flows over the Rockies and over the Great Plains are nearly out-of-phase due to inertial oscillation. During the nighttime, the westerly flows at 700–500 mb over the Rockies intensify while flows at the same level over the Great Plains turn easterly. These two flows converge over the eastern Rockies and induce cyclonic vorticity through vortex stretching. After sunrise, the convergence dissipates and the cyclonic vorticity is redistributed by horizontal vorticity advection, moving it downstream. This process creates a climatological zonally propagating vorticity signal which, in turn, facilitates the early-morning MP genesis at 12 UTC. The analysis also reveals marked dynamic instability conducive to subsynoptic-scale disturbances in the midtroposphere over the Rockies. Strong meridional temperature gradients appear over the north-facing slopes of the Rockies due to terrain heating to the south and the presence of cooler air to the north. This feature, along with persistent vertical shear, creates a Charney–Stern type of instability (i.e. sign changes of the meridional potential vorticity gradient). Meanwhile, the development of terrain boundary layer reduces the Rossby deformation radius which, subsequently, enhances the likelihood for baroclinic short waves. Such effects are most pronounced in the late afternoon and therefore are supportive to the MP genesis around 00 UTC. Examination of GCM experiments with and without orography further supports the critical role of the Rocky Mountains and its associated boundary layer impacts on the formation of MPs.

Keywords

Midtropospheric perturbation Short wave Baroclinic instability MCS Boundary layer 

References

  1. Aranson G (1963) The stability of nongeostrophic perturbations in a baroclinic zonal flow. Tellus 15:205–211CrossRefGoogle Scholar
  2. Banta RM (1984) Daytime boundary-layer evolution over mountainous terrain. Part 1: observations of the dry circulations. Mon Weather Rev 112:340–356CrossRefGoogle Scholar
  3. Banta RM (1986) Daytime boundary layer evolution over mountainous terrain. Part II: numerical studies of upslope flow duration. Mon Weather Rev 114:1112–1130CrossRefGoogle Scholar
  4. Banta RM, Cotton WR (1981) An analysis of the structure of local wind systems in a broad mountain basin. J Appl Meteorol 20:1255–1266CrossRefGoogle Scholar
  5. Barlow M, Nigam S, Berbery EH (1998) Evolution of the North American monsoon system. J Clim 11:2238–2257CrossRefGoogle Scholar
  6. Blackadar AK (1957) Boundary layer wind maxima and their significance for the growth of nocturnal inversions. Bull Am Meteorol Soc 38:282–290Google Scholar
  7. Bonner WD, Paegle J (1970) Diurnal variations in the boundary layer winds over the south-central United States in summer. Mon Weather Rev 98:735–744CrossRefGoogle Scholar
  8. Bosart LF, Sanders F (1981) The Johnstown Flood of July 1977: a long-lived convective system. J Atmos Sci 38:1616–1642CrossRefGoogle Scholar
  9. Bretherton FP (1966) Critical layer instability in baroclinic flows. Quart J R Meteorol Soc 92:325–334CrossRefGoogle Scholar
  10. Burpee R (1972) The origin and structure of easterly waves in the lower troposphere of North Africa. J Atmos Sci 29:77–90Google Scholar
  11. Carbone RE, Tuttle JD (2008) Rainfall occurrence in the U.S. warm season: the diurnal cycle. J Clim 21:4132–4146CrossRefGoogle Scholar
  12. Carbone RE, Tuttle JD, Ahijevych DA, Trier SB (2002) Inferences of predictability associated with warm season precipitation episodes. J Atmos Sci 59:2033–2056CrossRefGoogle Scholar
  13. Changnon SA, Kunkel KE (1999) The record 1996 rainstorm at Chicago. J Appl Meteorol 38:257–265CrossRefGoogle Scholar
  14. Charney JG, Stern M (1962) On the stability of internal baroclinic jets in a rotating atmosphere. J Atmos Sci 19:159–172CrossRefGoogle Scholar
  15. Chen TC, Yen MC, Wang SY (2007) Summer monsoon rainfall in East Asia and Taiwan. J Atmos Sci 35:305–352Google Scholar
  16. Davis CA, Ahijevych DA, Trier SB (2002) Detection and prediction of warm season midtropospheric vortices by the rapid update cycle. Mon Weather Rev 130:24–42CrossRefGoogle Scholar
  17. Doswell CA, Bosart LF (2001) Extratropical synoptic-scale processes and severe convection. In: Doswell CA (ed) Severe convective storms, Meteor. Monogr. 27, No. 49, Amer Meteor Soc, pp 27–69Google Scholar
  18. Eady ET (1949) Long waves and cyclone waves. Tellus 1:33–52CrossRefGoogle Scholar
  19. GFDL Global Atmospheric Model Development Teeam (2004) The new GFDL global atmosphere and land model AM2-LM2: evaluation with prescribed SST simulations. J Clim 17:4641–4673CrossRefGoogle Scholar
  20. Gutowski WJ (1985) Baroclinic adjustment and midlatitude temperature profiles. J Atmos Sci 42:1733–1745CrossRefGoogle Scholar
  21. Held IM (2007) Progress and problems in large-scale atmospheric dynamics. In: Schneider T, Sobel AH (eds) The global circulation of the atmosphere. Princeton University Press, Princeton, pp 1–21Google Scholar
  22. Held IM, Larichev VD (1996) A scaling theory for horizontally homogeneous, baroclinically unstable flow on a beta plane. J Atmos Sci 53:946–952CrossRefGoogle Scholar
  23. Helfand HM, Schubert SD (1995) Climatology of the simulated Great Plains low-level jet and its contribution to the continental moisture budget of the United States. J Clim 8:784–806CrossRefGoogle Scholar
  24. Hering WS, Borden TR (1962) Diurnal variations in the summer wind field over the central United States. J Atmos Sci 19:81–86CrossRefGoogle Scholar
  25. Hertenstein RF, Schubert WH (1991) Potential vorticity anomalies associated with squall lines. Mon Weather Rev 119:1663–1672CrossRefGoogle Scholar
  26. Higgins RW, Yao Y, Wang XL (1997) Influence of the North American Monsoon System on the United States summer precipitation regime. J Clim 10:2600–2622CrossRefGoogle Scholar
  27. Hobbs PV, Locatelli JD, Martin JE (1996) A new conceptual model for cyclones generated in the lee of the Rocky Mountains. Bull Am Meteorol Soc 77:1169–1178CrossRefGoogle Scholar
  28. Holton JR (2004) An introduction to dynamic meteorology, 4th edn. Academic Press, New York 535Google Scholar
  29. Jiang X, Lau NC, Klein SA (2006) Role of eastward propagating convection systems in the diurnal cycle and seasonal mean of summertime rainfall over the U.S. Great Plains. Geophys Res Lett 33:L19809. doi:10.1029/2006GL027022 CrossRefGoogle Scholar
  30. Jiang X, Lau NC, Held IM, Ploshay JJ (2007) Mechanisms of the Great Plains low-level let as simulated in an AGCM. J Atmos Sci 64:532–547CrossRefGoogle Scholar
  31. Johns RH (1982) A synoptic climatology of northwest flow severe weather outbreaks. Part I: nature and significance. Mon Weather Rev 110:1653–1663CrossRefGoogle Scholar
  32. Johns RH, Hirt WD (1987) Derechos: widespread convectively induced windstorms. Weather Forecast 2:32–49CrossRefGoogle Scholar
  33. Karyampudi VM, Koch SE, Chen C, Rottman JW, Kaplan ML (1995) The influence of the Rocky Mountains on the 13–14 April 1986 severe weather outbreak. Part II: evolution of a prefrontal bore and its role in triggering a squall line. Mon Weather Rev 123:1423–1446CrossRefGoogle Scholar
  34. Knievel JC, Johnson RH (2002) The kinematics of a midlatitude, continental mesoscale convective system and its mesoscale vortex. Mon Weather Rev 130:1749–1770CrossRefGoogle Scholar
  35. Kuo HL (1953) The stability properties and structure of disturbances in a baroclinic atmosphere. J Meteorol 10:235–243CrossRefGoogle Scholar
  36. Lieman R, Alpert P (1993) Investigation of the planetary boundary layer height variations over complex terrain. Boundary Layer Meteorol 62:129–142CrossRefGoogle Scholar
  37. Lin S, Pierrehumbert RT (1988) Does Ekman friction suppress baroclinic instability? J Atmos Sci 45:2920–2933CrossRefGoogle Scholar
  38. Maddox RA, Chappell CF, Hoxit LR (1979) Synoptic and mesoalpha scale aspects of flash flood events. Bull Am Meteorol Soc 60:115–123CrossRefGoogle Scholar
  39. Martner BE, Marwitz JD (1981) Airflow through the wind corridor in southern Wyoming. In: Proceedings of the second conference on mountain meteorology, Steamboat Springs, Amer Meteorol Soc, pp 309–315Google Scholar
  40. McCorcle MD (1988) Simulation of surface-moisture effects on the Great Plains low-level jet. Mon Weather Rev 116:1705–1720CrossRefGoogle Scholar
  41. Mesinger F et al (2006) North American regional reanalysis. Bull Am Meteorol Soc 87:343–360CrossRefGoogle Scholar
  42. Moore RW, Montgomery MT (2004) Reexamining the dynamics of shorts-scale, diabatic Rossby waves and their role in midlatitude moist cyclogenesis. J Atmos Sci 61:754–768CrossRefGoogle Scholar
  43. Nicolini M, Waldron KM, Paegle J (1993) Diurnal oscillations of low-level jets, vertical motion, and precipitation: a model case study. Mon Weather Rev 121:2588–2610CrossRefGoogle Scholar
  44. Paegle J, McLawhorn DW (1983) Numerical modeling of diurnal convergence oscillations above sloping terrain. Mon Weather Rev 111:67–85CrossRefGoogle Scholar
  45. Paegle J, Rasch GE (1973) Three-dimensional characteristics of diurnally varying boundary layer flows. Mon Weather Rev 101:746–756CrossRefGoogle Scholar
  46. Phillips NA (1954) Energy transformation and meridional circulations associated with simple baroclinic waves in a two-level quasi-geostrophic model. Tellus 6:273–286CrossRefGoogle Scholar
  47. Poulos GS, Bossert JE, McKee TB, Pielke RA (2000) The interaction of katabatic flow and mountain waves. Part I: observations and idealized simulations. J Atmos Sci 57:1919–1936CrossRefGoogle Scholar
  48. Robinson WA (2000) A baroclinic mechanism for the eddy feedback on the zonal index. J Atmos Sci 57:415–422CrossRefGoogle Scholar
  49. Satyamurty P (1983) Generation of subsynoptic-scale unstable baroclinic waves by surface friction. J Atmos Sci 40:2075–2079CrossRefGoogle Scholar
  50. Satyamurty P, Rao VB, Moura AD (1982) Subsynoptic-scale baroclnic instability. J Atmos Sci 43:1052–1061Google Scholar
  51. Staley DO (1989) Ageostrophic subsynoptic-scale baroclinic instability. J Atmos Sci 46:3065–3068CrossRefGoogle Scholar
  52. Staley DO, Gall R (1977) On the wavelength of maximum baroclinic instability. J Atmos Sci 34:1679–1688CrossRefGoogle Scholar
  53. Steenburgh WJ, Blazek TR (2001) Topographic distortion of a cold front over the Snake River Plain and central Idaho mountains. Weather Forecast 16:301–314CrossRefGoogle Scholar
  54. Stensrud DJ (1993) Elevated residual layers and their influence on surface boundary-layer evolution. J Atmos Sci 50:2284–2293CrossRefGoogle Scholar
  55. Stensrud DJ (1996) Importance of low-level jets to climate: a review. J Clim 9:1698–1711CrossRefGoogle Scholar
  56. Stone PH (1966) On non-geostrophic baroclinic stability. J Atmos Sci 23:390–400CrossRefGoogle Scholar
  57. Stone PH (1972) A simplified radiative-dynamical model for the static stability of rotating atmospheres. J Atmos Sci 29:405–418CrossRefGoogle Scholar
  58. Stone PH, Nemet B (1996) Baroclinic adjustment: a comparison between theory, observations, and models. J Atmos Sci 53:1663–1674CrossRefGoogle Scholar
  59. Stull RB (1988) An introduction to boundary layer meteorology. Kluwer, Dordrecht 666Google Scholar
  60. Swanson KL, Pierrehumbert RT (1997) Lower-tropospheric heat transport in the Pacific storm track. J Atmos Sci 54:1533–1543CrossRefGoogle Scholar
  61. Thorncroft CD, Hoskins BJ (1994a) An idealized study of African easterly waves. Part I: a linear view. Quart J Roy Meteor Soc 120:953–982Google Scholar
  62. Thorncroft CD, Hoskins BJ (1994b) An idealized study of African easterly waves. Part II: a nonlinear view. Quart J Roy Meteor Soc 120:983–1015Google Scholar
  63. Trier SB, Davis CA, Ahijevych DA, Weisman ML, Bryan GH (2006) Mechanisms supporting long-lived episodes of propagating nocturnal convection within a 7-Day WRF model simulation. J Atmos Sci 63:2437–2461CrossRefGoogle Scholar
  64. Tuttle JD, Davis CA (2006) Corridors of warm season precipitation in the central United States. Mon Weather Rev 134:2297–2317CrossRefGoogle Scholar
  65. Valdes PJ, Hoskins BJ (1988) Baroclinic instability of the zonally averaged flow with boundary layer damping. J Atmos Sci 45:1584–1593CrossRefGoogle Scholar
  66. Wallace JM (1975) Diurnal variations in precipitation and thunderstorm frequency over the conterminous United States. Mon Weather Rev 103:406–419CrossRefGoogle Scholar
  67. Wang SY, Chen TC (2008) Measuring East Asian summer monsoon rainfall contributions by different weather systems over Taiwan. J Appl Meteorol Climatol 47:2068–2080. doi:10.1175/2007JAMC1821.1 CrossRefGoogle Scholar
  68. Wang SY, Chen TC (2009) The late spring maximum of rainfall over the United States central plains and the role of the low-level jet. J Clim 22:4696–4709. doi:10.1175/2009JCLI2719.1 CrossRefGoogle Scholar
  69. Wang SY, Chen TC, Correia J (2009a) Climatology of summer midtropospheric perturbations in the U.S. northern plains. Part I: influence on northwest flow severe weather outbreaks. Clim Dyn. doi:10.1007/s00382-009-0696-3
  70. Wang SY, Chen TC, Taylor SE (2009b) Evaluations of NAM forecasts on midtropospheric perturbation-induced convective storms over the U.S. northern plains. Weather Forecast 24:1309–1333. doi:10.1175/2009WAF2222185.1 CrossRefGoogle Scholar
  71. Wiin-Nielsen A (1989) A stability investigation of a three level quasi-geostrophic model. Geophysica 25:21–35Google Scholar
  72. Zhang DL (1992) The formation of a cooling-induced mesovortex in the trailing stratiform region of a midlatitude squall line. Mon Weather Rev 120:2763–2785CrossRefGoogle Scholar
  73. Zhang DL, Fritsch JM (1988) Numerical simulation of the mesa-β scale structure and evolution of the 1977 Johnstown Flood. Part III. Internal gravity waves and the squall line. J Atmos Sci 45:1252–1268CrossRefGoogle Scholar
  74. Zurita-Gotor P, Lindzen RS (2004) Baroclinic equilibration and the maintenance of the momentum balance. Part II: 3D results. J Atmos Sci 61:1483–1499CrossRefGoogle Scholar
  75. Zurita-Gotor P, Lindzen RS (2006) A generalized momentum framework for looking at baroclinic circulations. J Atmos Sci 63:2036–2055CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Shih-Yu Wang
    • 1
    • 3
  • Tsing-Chang Chen
    • 1
  • Eugene S. Takle
    • 1
    • 2
  1. 1.Department of Geological and Atmospheric SciencesIowa State UniversityAmesUSA
  2. 2.Department of AgronomyIowa State UniversityAmesUSA
  3. 3.Utah Climate CenterUtah State UniversityLoganUSA

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