On the height distribution of convection in the tropics
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On the Height Distribution of Convection in the Tropics. Andrew Ballinger Monash University. Introduction and Motivation. Variety of convection in the tropics Multi-modal distribution of storm heights? Johnson et al , 1999. May and Rajopadhyaya, 1999. Implications:

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On the Height Distribution of Convection in the Tropics

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On the Height Distribution of Convection in the Tropics

Andrew Ballinger

Monash University


Introduction and Motivation

  • Variety of convection in the tropics

  • Multi-modal distribution of storm heights?

    • Johnson et al, 1999.

    • May and Rajopadhyaya, 1999.

  • Implications:

    • Tropospheric/Stratospheric exchange

    • Storm detrainment heights

    • Cirrus characteristics

    • Interpretation of satellite data


  • Types of Convection

    Continental

    • High Z extends well above FZL

    • Active lightning

    • Strong vertical motion

    • “Break” period

      • Low-level easterlies

    Oceanic

    • High Z mostly below FZL

    • Little lightning

    • Relatively “small” vertical motion

    • “Monsoon” period

      • Low-level westerlies


    TITAN

    Thunderstorm Identification, Tracking, Analysis, and Nowcasting.

    Reflectivity – 2km

    Reflectivity – 5km

    Reflectivity – 10km

    Reflectivity – 17km

    Dixon and Wiener, 1993


    Darwin Storm Dataset


    Storm initiation points (35 dBZ)

    Monsoon

    Break


    Storm initiation points (45 dBZ)

    Monsoon

    Break


    2pm

    3pm

    9am

    Diurnal cycle of the number of cells (35 dBZ)

    Monsoon

    Break


    4pm

    7am

    2pm

    Diurnal cycle of the number of cells (45 dBZ)

    Monsoon

    Break


    Distribution of storm max heights

    10

    10

    16

    17

    14

    14

    Distribution of storm max heights

    Monsoon

    35 dBZ

    45 dBZ

    Monsoon

    Tropopause

    Break

    35 dBZ

    45 dBZ

    Break


    Break – Diurnal cycle of storm max heights (35 dBZ)

    09:30 – 11:30

    15:30 – 17:30

    11:30 – 13:30

    17:30 – 19:30

    13:30 – 15:30

    19:30 – 21:30


    Summary

    • Convective cells deeper in break compared with monsoon

    • More intense cells in break period with strong overshoots of the tropopause

    • Intense cells mostly reach tropopause

    • In the monsoon period a height distribution max is found at 10km

    • Diurnal cycle of cell heights shows build up during the day.


    Questions?


    References

    • Dixon, M., and G. Wiener, 1993: “TITAN: Thunderstorm Identification, Tracking, Analysis, and Nowcasting – A Radar-based Methodology”, J. Atmos. Oceanic Technol., 10, 785–797.

    • Johnson, R.H., T.M. Rickenbach, S.A. Rutledge, P.E. Ciesielski and W.H. Schubert, 1999: “Trimodal Characteristics of Tropical Convection”, J. Clim., 12, 2397–2418.

    • Keenan, T.D., J. McBride, G. Holland, N. Davidson and B. Gunn, 1989: “Diurnal Variations during the Australian Monsoon Experiment (AMEX) Phase II”, Mon. Wea. Rev., 117, 2535–2552.

    • López, R.E., 1976: “Radar Characteristics of the Cloud Populations of Tropical Disturbances in the Northwest Atlantic”, Mon. Wea. Rev., 104, 268–283.


    Storm Duration

    Monsoon

    Total

    Break


    Reflectivity Thresholds (35)

    10 dBz

    1 dBz

    15 dBz

    5 dBz


    Reflectivity Thresholds (45)

    10 dBz

    1 dBz

    15 dBz

    5 dBz


    Monsoon/Break Definition

    Monsoon

    21/12/03 – 16/1/04

    Break 17/1/04

    – 31/1/04


    Break – Diurnal (45)


    Monsoon – Diurnal (35)


    Break – Diurnal (35)


    Monsoon – Diurnal (45)


    GATE Results

    ShallowCumulus

    CongestusCumulus

    Cumulonimbus


    Monsoon – Diurnal (35)


    Monsoon – Diurnal (45)


    Outline

    • Introduction and Motivation

    • Formulation of dataset

    • Results

    • Summary


    Motivation


    Acknowledgements

    • Dr Peter May – BMRC

    • Monash University

    • Bureau of Meteorology Research Centre


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