Dropsonde Measurements for Characterizing Lower Troposphere

Clouds, rain, sunlight and the ocean taken from the P-3 aircraft during the research flight on 16 November 2011 during the DYNAMO field campaign over the equatorial Indian Ocean. © Shuyi S Chen Probing SHUYI CHEN PROFESSOR the Indian Ocean Professor Shuyi Chen explains the Madden-Julian oscillation and on global weather and climate, and describes her work measuring the initiation and evolution of this phenomenon in the Indian Ocean Kunio Yoneyama of the Japan Agency for Marine- of in situ observations over the tropical Indian Earth Science & Technology, and Dr Chuck Long Ocean in the past has contributed to our poor of the Pacific Northwest National Laboratory, understanding and prediction of the MJO. organised a major field campaign known as the DYNAMO that took place over the central Is collaboration important to this project? tropical Indian Ocean. The goal of DYNAMO Which disciplines do you work with, and why? was to take in situ observations that could help improve understanding and prediction of the Yes, collaboration has been essential for the MJO and long-range weather forecasts and success of this project. I work with scientists in enable scientists to further improve climate both the atmospheric and ocean sciences with prediction models. expertise in observations as well as computer modelling. Our colleagues at the NOAA Aircraft Dropsondes are airborne meteorological Operational Center (pilots, aircraft crew and tools used to profile the atmosphere. How flight directors) and the National Center for do they work and have you had to adapt their Atmospheric Research (NCAR) Earth Observing function to observe the MJO? Laboratory (EOL) provided critical support for operating the aircraft from the Island of Diego Dropsondes are devices deployed from aircraft Garcia during DYNAMO. Could you begin with an explanation of the to measure the atmospheric temperature, Madden-Julian oscillation (MJO)? humidity, pressure and wind in weather systems. What does the future hold for MJO The technology has existed since the late 1990s prediction and how might this affect The MJO is a tropical atmospheric disturbance and has been tested successfully in hurricanes weather forecasting? that originates in the equatorial Indian Ocean over the Atlantic and eastern Pacific regions. once every 30 to 90 days and propagates The DYNAMO field campaign was, however, the The highly complex multiscale processes eastward around the world. It has major impacts first time that we had the opportunity to use governing formation and evolution of the MJO on the global weather systems, such as heat dropsondes to observe the MJO. interact in ways that scientists still struggle to waves, torrential rainfall, flooding, tropical understand, which are therefore not accurately cyclones and winter storms. On longer time The MJO is a multiscale phenomenon, so for this represented in the existing theoretical scales it also affects the onset of El Niño and the project we had to develop a new observational framework and computer models. DYNAMO global climate system. strategy to sample details in the convective has provided valuable in situ observations clouds while also covering a very large area over a relatively short time period, which will From what context did Dynamics of the MJO of the cloud environmental conditions. The shed some light on this very difficult problem. (DYNAMO) emerge? Who was responsible dropsondes, along with the Doppler radar However, it will take some time, and perhaps for its establishment? and other instruments on board the National many more observations, to solve this puzzle. Oceanic Atmospheric Administration (NOAA) The scientific community has long recognised WP-3D aircraft, has provided the most Our current capability of predicting weather the importance of accurate forecasts of the MJO comprehensive airborne dataset in the tropical in terms of where, when and how much it is in the global weather and climate system. The Indian Ocean to date. going to rain, and how strong the wind will current numerical weather prediction models, blow, is limited to a few days or even less. however, have little predictive skill. One of the What makes the tropical Indian Because of the intraseasonal timescale and most challenging problems for MJO forecasting Ocean a particularly important region the global spatial scale of the MJO, many is the initial development of cloud systems over for investigation? scientists consider it as the interface or bridge a very large area (thousands of km2) over the of the global weather and climate systems. tropical Indian Ocean. The lack of observations The tropical Indian Ocean is the birthplace If we can improve our understanding of the has been a major obstacle. of the MJO, where the cloud systems form physical processes affecting the MJO we over a huge area. They fuel the large-scale should be able transform that knowledge to A large international group of scientists, led by atmospheric circulation that ultimately affects build better computer models for weather and Dr Chidong Zhang of the University of Miami, Dr global weather and climate systems. The lack climate prediction. WWW.RESEARCHMEDIA.EU 33 PROFESSOR SHUYI CHEN Understanding initiation of Madden-Julian oscillation Including the University of Miami, international research project DYNAMO has pioneered techniques to measure the development of a poorly understood yet highly influential climate system THE WEATHER IS notoriously difficult The timing and impact of the MJO is difficult to predict. Meteorologists must take into to predict because it is controlled by a highly account huge atmospheric systems, each complex array of variables on many scales, from affected by a multitude of factors including water in clouds to global atmospheric wind and energy from the Sun and the surface of the oceanic currents. Existing weather models are land and ocean, and interactions with other often inaccurate and must be improved with in climate phenomena. situ observations of the MJO and, in particular, events associated with its initiation. The Madden-Julian oscillation (MJO) is a large- The NOAA WP-3D aircraft used in DYNAMO and scale fluctuation in tropical weather causing dropsonde/ABXT deployed from the aircraft. MEASURING THE MJO a range of effects including heat waves, monsoons and tropical storms. It is initiated in In order to shed light on this poorly understood temperature at different depths. This allowed the Indian Ocean every one to three months, weather phenomenon, an international Chen and colleagues to analyse the air-sea and travels eastwards around the world to research project called Dynamics of the MJO fluxes of heat and moisture, prior to and affect global weather and climate systems. (DYNAMO) was established to perform a field throughout the MJO-2 event. observation campaign in the tropical Indian Ocean – the main initiation region of the TRIGGERING THE MJO MJO. DYNAMO is a collaboration between 19 universities and 11 research centres, collecting The onset of the MJO is typically marked by observations of the MJO from land-, plane- a change from low to high rainfall over the and ship-based stations. equatorial Indian Ocean. Before the initiation, the sea surface temperature warms to its Shuyi Chen, Professor of Meteorology and maximum, which produces air-sea fluxes of Physical Oceanography at the University heat and moisture that are favourable for of Miami, Florida, was the aircraft mission cloud formation. Water rapidly evaporates to principal scientist during the DYNAMO form precipitating clouds by the process of field campaign in October 2011 to March convection. These convective cloud systems 2012. She was responsible for measuring the form a major component of the MJO, which initiation of the MJO using a combination of then travels eastwards across the ocean and onboard instruments and airborne devices. the rest of the globe. In November 2011, Chen and her team captured the initiation and evolution of a Chen found that dry air from the southern particularly strong MJO system – known as subtropics surged north into the equatorial DYNAMO MJO-2 – providing a valuable and Indian Ocean, displacing the southern rare insight into these events. intertropical convergence zone (ITCZ) – a region of increased precipitation, usually A combination of radar and dropsondes about 10-15° south off the Equator, where devices launched from aircraft to measure the northeast and southeast trade winds temperature, humidity, wind and pressure converge. The dry air disrupts the ITCZ, was used to profile the atmosphere over causing convective cloud formation to the tropical Indian Ocean. Chen and her redevelop on the Equator, triggering the MJO- team were able to analyse both small-scale 2 event (as illustrated in figures 1 a and 1b). composition details within clouds and the large-scale weather systems that form in Remarkably, the dry air was also shown to be Figure 1. MJO initiation based on DYNAMO observations: (a) the tropical Indian Ocean to build up a involved in the eastward propagation of the ITCZ, (b) dry air intrusion displacing convection from the ITCZ 3D structure of cloud systems. Airborne MJO by causing swirling atmospheric waves, to the Equator and triggering MJO initiation, and (c) dry air expendable bathythermographs (AXBTs) which draws in more dry air from the western advection from the west propelling the MJO eastward. were also deployed, which measure the ocean Indian Ocean and subtropics to the equatorial 34 INTERNATIONAL INNOVATION INTELLIGENCE GPS dropsonde DROPSONDE MEASUREMENTS deployed from the FOR CHARACTERIZING LOWER NOAA WP-3D aircraft. The MJO is an integral part of global weather and TROPOSPHERE MOISTURE VARIABILITY AND AIR-SEA INTERACTION OVER THE climate systems but it is notoriously difficult to predict TROPICAL INDIAN OCEAN using existing models OBJECTIVES • To observe atmospheric water vapour edge of the MJO. This second intrusion Weather Forecast variability, convective cloud systems and suppressed cloud convection west of MJO-2 (ECMWF) model and air-sea fluxes and propelled the event eastward (figure 1c).

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