Vertical cloud structures of the boreal summer intraseasonal variability based on CloudSat observations and ERA-interim reanalysis

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Vertical cloud structures of the boreal summer
intraseasonal variability based on CloudSat
observations and ERA-interim reanalysis
X. Jiang D. E. Waliser J.-L. Li C. Woods,
Vertical cloud structures of the boreal summer
intraseasonal variability based on CloudSat
observations and ERA-interim reanalysis,2010
Xianan Jiang Duane E. Waliser Jui-Lin Li
Christopher Woods

• SpeakerLi-Chiang Jiang

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Outline

• Introduction
• Datasets
• An index for the boreal summer intraseasonal
  variability (BSISV)
• Vertical cloud structures of the northward
  propagating BSISV
• Summary

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MJO(MaddenJulian Oscillation)

• The intraseasonal variability (ISV) plays a
  significant role for tropical climate
• Eastward propagating in boreal winter
• A period of 3050 days, northward propagation
  over the Asian monsoon region in boreal summer

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EEOF Method

• (1) All the data were binned into pentad (5-day)
  values.
• (2) Intraseasonal anomalies were obtained by
  removing the annual cycle and data filtering
  through a 3090-day band pass filter.
• (3) Perform an EEOF analysis on band-passed
  (30-90 day) rainfall data (e.g., TRMM, CMAP) over
  the tropical Indian Ocean and western Pacific.
• (4) Identify MJO events from the PC time series
  of 1st EEOF mode.
• (5) Composite MJO events in band-passed rainfall
  and target quantity (e.g., temperature, moisture,
  ozone, aerosols).

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Introduction

• Sikka and Gadgil(1980)Cadet(1986) Lawrence and
  Webster(2002).
• The meridional propagation of the BSISV is
  found to be intimately associated with active and
  break phases of the Asian summer monsoon
• Jiang et al. (2004)
• Identified prominent meridional asymmetric
  structures associated with the northward
  propagating BSISV.

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Introduction

• Hsu et al.(2004)Fu et al.(2006)
• The northward shift of low-level moisture
  perturbation relative to the BSISV convection,
  which may suggest a pre-conditioning process for
  its northward propagation.
• An easterly vertical wind shear mechanism to
  explain the northward propagation of the BSISV.

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Now

• The study focus on
• Since three summer seasons from 2006 to
  2008.Compared to Cloud structures from CloudSat
  data and ERA-interim reanalysis data.

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Datasets

• European Centre for Medium-Range Weather
  Forecasts (ECMWF) ERA-interim reanalysis
• Liquid water content (LWC) and ice and water
  content (IWC) (2006 2008)
• CloudSat dataset
• Liquid water content (LWC) and ice and water
  content (IWC) (2006 2008)
• Tropical Rainfall Measuring Mission (TRMM)
• Daily mean rainfall with a horizontal
  resolution of 1 1
• (20062008)

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An index for the BSISV
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An index for the BSISV
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Vertical cloud structures of the northward
propagating BSISV
CloudSat LWC
CloudSat IWC
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Vertical cloud structures of the northward
propagating BSISV
ERA-interim LWC
ERA-interim IWC
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Vertical cloud structures of the northward
propagating BSISV
LWC
IWC
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CloudSat
ERA- interim
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Vertical cloud structures of the northward
propagating BSISV
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Total
CloudSat
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ERA- interim
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Summary and discussion

• Increased LWC in the lower troposphere is located
  north of the BSISV rainfall maximum, and
  therefore leads the convection,so northward
  displacement.
• Enhanced LWC anomalies to the north of the BSISV
  convection center are largely associated with
  low-level cumulus/stratocumulus clouds.

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Summary and discussion

• The maximum LWC anomalies are detected in the
  lower troposphere based on CloudSat, and in the
  middle troposphere in the ERA-interim.
• Enhanced cloud IWC is evident in the upper
  troposphere corresponding to enhanced BSISV
  convection.

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Summary and discussion

• Aforementioned differences in LWC and IWC
  structures associated with the BSISV could be
• ascribed to model biases and differences
  between CloudSat and ERA-interim datasets could
  be due to data sampling.

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Thanks for your attention !