In consideration of the fact that an increasing number of developing countries are now becoming active in the study of lower and middle atmosphere with the aim of obtaining improved weather forecasting, The Abdus Salam International Centre for Theoretical Physics (ICTP - Trieste, Italy) is organizing a Workshop on Physics of Mesosphere-Stratosphere-Troposphere Interactions with special emphasis on MST Radar Techniques. The workshop will be held in Trieste from 13 to 24 November 2000 under the direction of Prof. S. M. Radicella (Head of the Aeronomy and Radiopropagation Laboratory - ICTP) and Prof. D. Narayana Rao (Head of the Department of Physics, Sri Venkateswara University, Tirupati, India). The Faculty will also be composed of the Professors: S. FUKAO, Kyoto University, Japan K. S. GAGE, National Oceanic Atmospheric Admin., USA W. K. HOCKING, University of Western Ontario, Canada J. ROETTGER, Max Plank Institut für Aeronomie, Germany PURPOSE AND NATURE The main goal of the workshop is to understand the structure of the lower and middle atmosphere and contextually to study the interactions between its three components: Mesosphere, Stratosphere and Troposphere. The activity will include tutorial lectures and laboratory work. During the latter the participants, assisted by members of the faculty, will analyze data, obtained through the application of different radar techniques. The workshop will cover the following topics: Stable atmosphere: tropopause/stratosphere, Gravity waves and turbulence, Tropical meteorology, Mesospheric dynamics, Lower ionosphere structure, Scattering mechanisms, Principles of ST/MST Radar, Wind profilers, Boundary layer radar, Radio Acoustic sounding system, Meteor radar. PARTICIPATION Scientists and students from all countries that are members of the United Nations, UNESCO or IAEA can attend the activity. The main purpose of the Centre is to help research workers from developing countries through a programme of training activities within a framework of international co-operation. However students and post-doctoral scientists from developed countries are also welcome to attend. As the Workshop will be conducted in English, participants should have an adequate working knowledge of that language. As a rule, travel and subsistence expenses of the participants should be borne by the home institutions. However, limited funds are available for some scientists from developing countries. As scarcity of funds allows travel to be granted only in few exceptional cases, every effort should be made by candidates to secure support for their fares (or at least half-fare) from their home country. It is stressed that participants whose travel expenses are paid by the ICTP are required to attend the entire activity. For logistics reasons, connected with the number of Personal Computers available, the total number of participants in the Workshop is limited. There is no registration fee for attending the activity.