Advanced Sounding & Modeling for Atmospheric Change Analysis

START project Y 103 Advanced Sounding & Modeling for Atomspheric Change Analysis Gottfried KIRCHENGAST 19.06.1998 Global concerns exist that the natural evolution of the Earth`s climate system is increasingly influenced by human activities. Atmospheric change is central to this "global climate change" problem. Especially the atmosphere`s radiative processes play a crucial role in climate and shape the atmosphere`s thermal structure, the temperature field. The proposed project aims at providing key contributions for a better understanding of climatic changes in the atmosphere`s thermal structure both due to natural and anthropogenic influences. Focus is to employ for this purpose advanced spaceborne remote atmospheric sounding techniques and radiation and energy balance modeling with unprecedented vertical resolution and accuracy. More specifically, the project contains the key activities summarized below. Advancement of the analysis of data from the so-called Radio Occultation (RO) technique for high-quality temperature profile retrieval and preparation of a long-term temperature climatology. Determination whether temperature change monitoring by the RO technique is in fact, as currently hoped, the most useful existing technique for this purpose. Use of the temperature climatology for analysing known interannual variability phenomena and yet undiscovered ones which might be found by the high vertical resolution and accuracy furnished by RO data. Preparation of long-term temperature trend analysis. Preparation of Infrared Advanced Sounder Interferometer (IASI) data analysis for highquality temperature and water vapor profile retrieval as well as for retrieving cloud parameters. Synergistic use of IASI/RO data, especially for cloud parameter retrieval. Development of a flexible high-vertical-resolution radiation and energy balance model for clear-sky and cloudy conditions. Use of this model for high-vertical-resolution diagnostic studies not possible with current General Circulation Models (GCMs), with the aim in mind to improve GCM energy balance physics, especially of clouds. Validation of the modeled temperature structure against the RO data and other suitable data. Employment of the developed energy balance model to study the interaction of radiation with upper tropospheric water vapor and clouds and assessment of the resulting temperature profiles. Study of the effect of increased greenhouse gases and aerosol on upper tropospheric water vapor and clouds and on the temperature profile in order to help reduce present uncertainties in water vapor/cloud feedback to anthropogenic radiative forcing. Furthermore, study of the realistic evolution of high-vertical-resolution temperature profiles by combined time-dependent analysis of the energy balance model and the RO and IASI data (plus other suitable data). Comparison to GCM data and assessment of potential improvements to GCM physics. Influence of the proposed work an the development of the field Significant influence is expected on the development of the field of climate change science concerning both (i) observations of climate change and (ii) modeling of climate change. (i) The analysis of an atmospheric temperature climatology performed based on advanced satellite borne remote measurements with unprecedented vertical resolution, accuracy, and long-term stability, has high potential to demonstrate to the climate community a novel type of atmospheric temperature change monitoring superior to any present means. Among many other benefits (such as the development of advanced data analysis methods), this would be a key contribution to studies for the detection and attribution of climate change. (ii) Combined use of high-vertical-resolution satellite borne measurements with long-term availability and of realistic high-vertical-resolution radiation and energy balance modeling will allow to characterize the evolution of the atmosphere`s vertical thermal structure with unprecedented detail. As one salient benefit, the emphasis placed on advancing the understanding of the interaction of radiation with clouds would help to reduce present uncertainties in cloud feedback to anthropogenic radiative forcing. As another related benefit, the contributions provided to improve the parameterization of energy balance physics, especially of clouds, in General Circulation Models, would help to increase the reliability of these models for climate change predictions.