EPIC - ITCZ Summary

EPIC Scientific Objective (ITCZ)To observe and understand the ocean-atmosphere processes responsible for the structure and evolution of the large-scale atmospheric heating gradients in the equatorial and northeastern Pacific portions of the cold-tongue/ITCZ complex, including:

(a) Mechanisms governing temperature and salinity field evolution in the oceanic cold tongue and in the region of strong meridional gradient in sea surface temperature from the oceanic cold tongue through the ITCZ (air-sea interaction). (b) Atmospheric planetary boundary layer structure and evolution from the equator through the ITCZ, primarily in the southerly monsoonal regime(c) The processes determining the existence, character and strength of deep convection in the northeast Pacific ITCZ.

Objective (a): air-sea interaction

• instrument/acoustic raingauge (Nystuen and Ma )

• synoptic waves (Serra)• MJO (Maloney and Esbensen; Bielli

et al.)• shallow circulation and

entrainment (Zhang et al.)• zonal wind (Raymond)

Objective (b): Boundary layer

• momentum budget (Zhang et al.)• zonal winds/MJO (Raymond)• model - observation comparison

(Zeng et al.)

Objective (c): deep convection

• radar/satellite/region intercomparisons (Cefilli et al.; Nesbitt et al.; Pereira et al.)

• zonal winds (Raymond)• ABL entropy (Carrillo and Raymond)• waves: (Kiladis and Straub; Cifelli et

al.; Serra; Raymond; Maloney and Esbensen; Bielli et al.)

• orographic effects (Xie et al.)• vertical structure (Zuidema)• instrument/lidar (Baumgardner et al.)

Synthesis of EPIC ITCZ Research (1) Deep convection in the ITCZ is affected by atmospheric wave activities (easterly, Kelvin, MJO)– Do these waves simply redistribute deep convective precipitation in space and time or modulate the total amount of precipitation in the mean?

Synthesis of EPIC ITCZ Research (2) ITCZ convection is susceptible to ABL entropy, surface fluxes, northerly and southerly inflow/convergence,

– What is the importance of aerosol, mid and upper level humidity, and large-scale subsidence?

Synthesis of EPIC ITCZ Research (3) There are significant differences among deep convective systems in the regions of EPIC, TEPPS, and LBA

– How different are deep convective systems in the eastern Pacific from those in the western Pacific (TOGA COARE), North American monsoon (NAME), Atlantic ITCZ and Africa (AMMA/AMI)?

Synthesis of EPIC ITCZ Research (4) The vertical structure of convection in the ITCZ is of multi-mode

– Is the bimodal distribution in ITCZ convection caused by convective-scale or large-scale dynamics? – How is the bimodal distribution in ITCZ convection related to the bimodal distribution in the large-scale meridional overturning circulation?

Courtesy ofWalter Peterson

Synthesis of EPIC ITCZ Research (5) The vertical-meridional circulation in the eastern Pacific is featured of a deep and a shallow cell.

Equ

– What are the dynamics and climate significance of the shallow meridional circulation?

Synthesis of EPIC ITCZ Research (6) Air-sea interaction may take place in and near the ITCZ through modulations of surface winds by wave activities, zonal wind, and boundary-layer entrainment

– Are perturbations in SST important to the wave activities in the ITCZ?– Can the relative importance of absolute SST in the ITCZ vs. SST gradient to ITCZ convection be quantified?

Synthesis of EPIC ITCZ Research (7) Model deficiencies in the EPIC region include: underestimate of the ABL height, misrepresentation of the orography,

– Can models reproduce the multi-mode vertical structure of ITCZ convection, the shallow meridional circulation, the ABL structure, the regional dependence of convection/precipitation, and the effects of waves on ITCZ convection?

Synthesis of EPIC ITCZ Research (8) EPIC atmospheric observation sources include ship (radars, soundings, ….), aircraft (radar, lidar, dropsondes, …..), moorings, satellite, etc.

– need integrating approaches to combine these observations; – need integrating approaches to combine atmospheric and oceanic observations

What’s New?

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Structures of cloud and precipitation in the ITCZ

Convective Variability Across the East Pacific: A comparison of Precipitation Structure in the TEPPS and EPIC Domains - Robert Cifelli, Steve Nesbitt, and Steven A. Rutledge

EPIC and Other Recent Field Campaign Radar Data Collected in the Context of the TRMM PR Climatology - Stephen W. Nesbitt, Robert Cifelli, and Steven A. Rutledge

Convective Characteristics over the East Pacific and Southwest Amazon Regions: A Radar Perspective - Luis Gustavo Paiva Pereira and Steven A. Rutledge

On the Vertical Structure of the Upper Tropical Troposphere observed during EPIC by Cloud Radar and Soundings - P. Zuidema

Convection - Circulation Interaction I: Boundary-Layer Dynamics

Role of PBL-Top Zonal Winds in East Pacific ITCZ Dynamics - David J. Raymond

Role of the ITCZ in Air-Sea Interaction - Chidong Zhang, Michael McGauley, and Nick Bond

Spatial Variability of Entropy in the Boundary Layer - C. Lopez Carrillo and Dave J. Raymond

Marine Atmospheric Boundary Layer Height over the Eastern Pacific: Data Analysis and Model Evaluation - Xubin Zeng, M.A. Brunke, M. Zhou, C. Fairall, N.A. Bond, D.H. Lenschow

Convection - Circulation Interaction II: Wave Dynamics

Atmospheric Kelvin waves and Convective Variability over the EPIC Study Region - George N. Kiladis

Synoptic Disturbances in the East Pacific ITCZ and Their Effects on the Boundary Layer and Upper-Ocean Mixed Layer - Yolande L. Serra

The Amplification of East Pacific Intraseasonal Oscillation Convection and Wind Anomalies during June-November - Eric D. Maloney, Steven K. Esbensen

Maximum Covariance Analysis of the Summertime MJO in the Eastern Pacific - Soline Bielli, Dennis L. Hartmann, David J. Lorenz

Instrumentation

EPIC 2001 Lidar "Calibrations" with In Situ Measurements - D. Baumgardner, G.B. Raga and J.C. Jimenez

Acoustic Rain Gauge Measurements in the Eastern Tropical Pacific Ocean - Jeffrey A Nystuen and Barry Ma

Large-Scale Circulation

Predicting The Onset Of The North American Monsoon And Progress Toward A Mechanistic Understanding - David L. Mitchell, Beth Hall, Miguel F. Lavíin, Dorothea Ivanova 1and Kelly Redmond

Satellite observations and numerical simulation of eastern Pacific climate - Shang-Ping Xie, Haiming Xu, Yuqing Wang, and Justin Small