The first phase of the ARMEX (Arabian Sea Monsoon Experiment) has been sponsored by Department of Science and Technology as part of Indian Climate Research Programme (ICRP). The aim of ARMEX is to investigate some important sub-synoptic features, which are responsible for very intense weather activity over a small area for a short period of a few hours to two days. India Met Department (IMD), Indian Institute of Technology (Delhi), Indian Institute of Tropical Met (IITM) Pune, NCMRWF, New Delhi, Indian Institute of Sciences (IIS) Bangalore and several universities also participated in the experiment along with the Indian Navy and Coast Guard.

The Indian Air Force with a dedicated meteorological branch has been involved in various international experiments in studying the behaviour pattern of monsoon. These experiments included Monsoon Experiment (MONEX) in 1979 with participation of many countries including USA and USSR and Monsoon Trough Boundary Layer Experiment (MONTBLEX) during
1990-93. However, for the first time, IAF allotted two AN-32 aircraft to collect in-flight meteorological data during the experiment. IAF also provided the manpower and equipment to record meteorological observations.

IAF transport aircraft offered an excellent platform to gather atmospheric parameters like temperature profile, moisture content and aerosol composition. One AN-32 aircraft was suitably modified at a work-station at Air Force Base Repair Depot (BRD), Kanpur to facilitate the IAF meteorological branch officers to take visual observation, undertake cloud photography and record other observations. The modifications included facilities for digital and video mapping of cloud imageries, upper air observations and an external probe in the form of aerosol analyser. In addition, both the aircraft were fitted with GPS to co-relate upper air observations with ground situation. Any modification in the aircraft requires test flying and certification of the modified aircraft. This task was undertaken by Directorate of Engineering and Directorate of Project at Air HQ.

The operation plan was worked out by Directorate of Met in consultation with Directorate of T&H at Air HQ. Command Meteorological Officer, HQ TC, IAF and Senior Meteorological Officer, AF Station, Yelahanka functioned as a nodal agency for planning and execution of IAF aircraft missions. Each commitment was planned on a day-to-day basis. The sorties were undertaken along a preplanned route and according to weather conditions on specific clearance from Directorate of T&H. An officer from Directorate of Met functioned as a contact person. He remained in contact with ARMEX Operation Centre located at India Meteorological Department, Lodhi Road, New Delhi. His task was to obtain all requirements of airborne and Pilot Ballon (PB) observations to be taken by IAF. Indian Meteorological Department was advised to give any requirement of airborne observations at least 48 hours in advance. On receipt of requirements, he liaised with Directorate of Operations (T&H) and Command Meteorological Officer, HQ TC for launch of the mission.

IAF was to fly maximum of two sorties a day over ARMEX area as per predetermined flight profile. The area of study extended from Saurashtra to extreme southern tip of Indian peninsula. The aircraft were operating from AF station, Yalahanka. The flying was restricted to day flying only. While flying, the aircraft were not to enter the intense convective cells. During the entire ARMEX, period flying effort was 20 sorties and about 80 flying hours.

Two Met Officers or Met Assistants remained onboard to fly in each mission to record in-flight observations. The airborne operations also involved special weather radar observations. By rotating the radar antenna in the air, a three dimensional image of the weather system is profiled for better understanding. These observations are complementary to the detection of mesoscale features, which can not be seen in satellite imageries. In addition, milking of Flight Data Recorder (FDR) was done on daily basis. These observations were scrutinised and compiled.

In addition to airborne observations, IAF was also involved in special surface and upper air observations. IAF undertook upper air observations and surface observations at Vadodara, Belgaum and Sulur. SWAC set up an upper air Pilot Balloon (PB) observatory at AF Station Vadodara and HQ TC at AF Station Belgaum. Central Met Store, New Delhi arranged the necessary equipment for AF Station, Vadodara and Belgaum. An Automated Weather Stations at (AWS) was installed at AF Station, Sulur.

IAF also provided two Met Observers to take ship observations from a Coast Guard ship. The Met Assistants took ship observations hourly during the day and synoptic hourly during night and maintained a Current Weather Log.