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Title: Atmospheric Radiation Measurement Madden-Julian Oscillation Investigation Experiment Field Campaign Report

Abstract

Every 30–90 days during the Northern Hemisphere winter, the equatorial tropical atmosphere experiences pulses of extraordinarily strong deep convection and rainfall. This phenomenon is referred to as the Madden–Julian Oscillation, or MJO, named after the scientists who identified this cycle. The MJO significantly affects weather and rainfall patterns around the world (Zhang 2013). To improve predictions of the MJO—especially about how it forms and evolves throughout its lifecycle—an international group of scientists collected an unprecedented set of observations from the Indian Ocean and western Pacific region from October 2011 through March 2012 through several coordinated efforts. The coordinated field campaigns captured six distinct MJO cycles in the Indian Ocean. The rich set of observations capturing several MJO events from these efforts will be used for many years to study the physics of the MJO. Here we highlight early research results using data from the Atmospheric Radiation Measurement (ARM) Madden-Julian Oscillation Investigation Experiment (AMIE), sponsored by the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility.

Authors:
 [1]
  1. National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States). Earth System Research Lab.
Publication Date:
Research Org.:
DOE Office of Science Atmospheric Radiation Measurement (ARM) Program (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1302195
Report Number(s):
DOE/SC-ARM-16-039
DOE Contract Number:
AC05-7601830
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; Gan Island, Indian Ocean, atmospheric convection, intertropical convergence zone, Madden-Julian Oscillation

Citation Formats

Long, Chuck. Atmospheric Radiation Measurement Madden-Julian Oscillation Investigation Experiment Field Campaign Report. United States: N. p., 2016. Web. doi:10.2172/1302195.
Long, Chuck. Atmospheric Radiation Measurement Madden-Julian Oscillation Investigation Experiment Field Campaign Report. United States. doi:10.2172/1302195.
Long, Chuck. 2016. "Atmospheric Radiation Measurement Madden-Julian Oscillation Investigation Experiment Field Campaign Report". United States. doi:10.2172/1302195. https://www.osti.gov/servlets/purl/1302195.
@article{osti_1302195,
title = {Atmospheric Radiation Measurement Madden-Julian Oscillation Investigation Experiment Field Campaign Report},
author = {Long, Chuck},
abstractNote = {Every 30–90 days during the Northern Hemisphere winter, the equatorial tropical atmosphere experiences pulses of extraordinarily strong deep convection and rainfall. This phenomenon is referred to as the Madden–Julian Oscillation, or MJO, named after the scientists who identified this cycle. The MJO significantly affects weather and rainfall patterns around the world (Zhang 2013). To improve predictions of the MJO—especially about how it forms and evolves throughout its lifecycle—an international group of scientists collected an unprecedented set of observations from the Indian Ocean and western Pacific region from October 2011 through March 2012 through several coordinated efforts. The coordinated field campaigns captured six distinct MJO cycles in the Indian Ocean. The rich set of observations capturing several MJO events from these efforts will be used for many years to study the physics of the MJO. Here we highlight early research results using data from the Atmospheric Radiation Measurement (ARM) Madden-Julian Oscillation Investigation Experiment (AMIE), sponsored by the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility.},
doi = {10.2172/1302195},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 7
}

Technical Report:

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  • Deep convection in the tropics plays an important role in driving global circulations and the transport of energy from the tropics to the mid-latitudes. Understanding the mechanisms that control tropical convection is a key to improving climate modeling simulations of the global energy balance. One of the dominant sources of tropical convective variability is the Madden-Julian Oscillation (MJO), which has a period of approximately 30–60 days. There is no agreed-upon explanation for the underlying physics that maintain the MJO. Many climate models do not show well-defined MJO signals, and those that do have problems accurately simulating the amplitude, propagation speed,more » and/or seasonality of the MJO signal. Therefore, the MJO is a very important modeling target for the ARM modeling community geared specifically toward improving climate models. The ARM MJO Investigation Experiment (AMIE) period coincides with a large international MJO initiation field campaign called CINDY2011 (Cooperative Indian Ocean experiment on intraseasonal variability in the Year 2011) that will take place in and around the Indian Ocean from October 2011 to January 2012. AMIE, in conjunction with CINDY2011 efforts, will provide an unprecedented data set that will allow investigation of the evolution of convection within the framework of the MJO. AMIE observations will also complement the long-term MJO statistics produced using ARM Manus data and will allow testing of several of the current hypotheses related to the MJO phenomenon. Taking advantage of the expected deployment of a C-POL scanning precipitation radar and an ECOR surface flux tower at the ARM Manus site, we propose to increase the number of sonde launches to eight per day starting in about mid-October of the field experiment year, which is climatologically a period of generally suppressed conditions at Manus and just prior to the climatologically strongest MJO period. The field experiment will last until the end of the MJO season (typically March), affording the documentation of conditions before, during, and after the peak MJO season. The increased frequency of sonde launches throughout the experimental period will provide better diurnal understanding of the thermodynamic profiles, and thus a better representation within the variational analysis data set. Finally, a small surface radiation and ceilometer system will be deployed at the PNG Lombrum Naval Base about 6 km away from the ARM Manus site in order to provide some documentation of scale variability with respect to the representativeness of the ARM measurements.« less
  • Regional cloud permitting model simulations of cloud populations observed during the 2011 ARM Madden Julian Oscillation Investigation Experiment/ Dynamics of Madden-Julian Experiment (AMIE/DYNAMO) field campaign are evaluated against radar and ship-based measurements. Sensitivity of model simulated surface rain rate statistics to parameters and parameterization of hydrometeor sizes in five commonly used WRF microphysics schemes are examined. It is shown that at 2 km grid spacing, the model generally overestimates rain rate from large and deep convective cores. Sensitivity runs involving variation of parameters that affect rain drop or ice particle size distribution (more aggressive break-up process etc) generally reduce themore » bias in rain-rate and boundary layer temperature statistics as the smaller particles become more vulnerable to evaporation. Furthermore significant improvement in the convective rain-rate statistics is observed when the horizontal grid-spacing is reduced to 1 km and 0.5 km, while it is worsened when run at 4 km grid spacing as increased turbulence enhances evaporation. The results suggest modulation of evaporation processes, through parameterization of turbulent mixing and break-up of hydrometeors may provide a potential avenue for correcting cloud statistics and associated boundary layer temperature biases in regional and global cloud permitting model simulations.« less
  • Two Madden-Julian Oscillation (MJO) episodes observed during the 2011 AMIE/DYNAMO field campaign are simulated using a regional cloud-permitting model, a regional model with various cumulus parameterizations, and a global variable-resolution model with a high-resolution region centered over the tropical Indian Ocean. Model biases associated with moisture mode instability, wind-induced surface heat exchange (WISHE), and convective momentum transport (CMT) are examined and their relative contributions to the overall model errors are quantified using a linear statistical model. Linear relationships are found among the normalized root mean square errors of precipitation, saturation fraction, evaporation, and surface wind speed suggesting that errors maymore » propagate across the processes involving these variables. Analysis using a linear statistical model shows the relationship between convection and local surface wind speed (related to CMT processes) is the source of the largest uncertainty. In comparison, WISHE processes in the simulations tend to be biased consistently, with excess evaporation for the same wind speeds as the observations, which suggests they are likely related to biases in boundary layer and/or surface schemes. The relationship between precipitation and saturation fraction (which is associated with moisture mode instability) is captured relatively well with slightly larger model precipitation in the simulations in comparison to observations for the same saturation fraction, especially for weak rain rates. By linking developments in theoretical understanding of MJO processes and cumulus parameterizations, this study provides guidance to future improvements of MJO simulation by in high-resolution regional and global models.« less
  • Results of the ARM Madden-Julian Oscillation (MJO) Investigation Experiment (AMIE) field campaign are contributing significantly to concurrent national and international research efforts addressing questions about how the MJO initiates and changes as it passes phenomenon differs in observations versus models.