Research Institute for Sustainable Humanosphere

Regional characteristics of Precipitation, Temperature and Water vapor in the western Pacific region, in particular, Over Indonesia

氏名 I. VENKATA, Subba Reddy
共同研究者 津田敏隆
採択年 2007(平成19) 年度

The spatial and temporal variations in precipitation, temperature and water vapor are most important in the climate change. Large-scale precipitation estimates can be derived from either surface gauge measurements or by satellite remote sensing, both of which have shortcomings. But recent years Aqua, Aura and COSMIC missions were highly useful and which covers the data globally. Aura is part of the Earth Observing System (EOS), a program dedicated to monitoring the complex interactions that affect the globe using NASA satellites and data systems. Aura’s instruments will observe the important sources, radicals, and reservoir gases active in ozone chemistry. The COSMIC mission is Global Positioning System (GPS) radio occultation (RO) which is launched on April 15, 2006 and it includes six microsatellites. The main purpose of this mission is to provide ~2500 real-time soundings per day with homogenous global coverage. Which can potentially have major impacts on weather, climate and space weather research and forecasting. This technique works by measuring the amplitudes and phase delays of radio signals from GPS satellites as they are occulted by the Earth’s atmosphere, and then retrieving atmospheric profiles of bending angle, refractivity, temperature, pressure and water vapor, as well as electron density in the ionosphere. GPS observations provide a unique combination of accuracy, high vertical resolution and insensitivity to clod and aerosol particles that is well suited to observations of the lower troposphere. These characteristics combined with the inherent stability of radio occultation observations make it an excellent tool for the measurements of long term trends.

The COSMIC satellite data is most useful to study the variation of water vapor, temperature and precipitation, because of global coverage with high spatial resolution. The aqua satellite data is also used to study the water vapor horizontally. The water vapor distribution varies sharply in the vertical dimension as evident in the many forms of stratiform cloud system. The convective and stratiform clouds are most important in the tropical region. Tropical precipitation provides three fourths of the energy that drives the atmospheric wind circulation through latent heat release. To understand the variation of these parameters globally the radio occultation (RO) technique is one of the most powerful techniques. Since the distribution of the radio occultation events is nearly uniform over the continent and ocean of the earth, the research of the global meteorological variations, large scale atmospheric wave propagations, local weather report, and so on, are quite promising and beneficial.

The ultimate goal and objectives of the study are as follows. To retrieve the water vapor from the RO satellite data and to study the annual, year-year and long term (10–20 years) variability of temperature, precipitation and water vapor over the western pacific region, with special emphasis over the Indonesia over the latitude ±20° and longitude 90°–180° E. In addition to COSMIC, Aqua and Aura satellites the equatorial atmospheric radar (EAR) is located at Indonesia is also used to understand the local disturbances and small scale phenomena and also to strengthen the satellite observations. The tropopause characteristics such as height of the tropopause, latitudinal and longitudinal variations, annual, year-year and long term variability of the tropopause temperature, height variation of tropopause will be studied. The possible mechanism for the variations of tropopause height and coupling process in the troposphere and stratosphere regions will be studied. The OLR data is archived from NCAR and is commonly used as a proxy of deep convection in studies of large-scale convective activity. Convective updrafts overshooting the cold point tropopause and can generate extremely cold, dry air within the updraft. In the tropical regions deep convection is one of the important mechanisms which will influence the height and structure of the tropopause, the value of the cold point temperature and the exchange of energy between troposphere and stratosphere. Deep convection is the dominant source of gravity wave (GW) activity in tropical regions. Temperature variability driven by GWs can drive in situ formation of tropical tropopause layer (TTL) cirrus that can effectively dehydrates air slowly ascending into the stratosphere. By using the COSMIC data set the above studies will be carried out extensively.

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