Refer to figure.
AIREP stands for Aircraft Report. It is a type of meteorological report made by an aircraft in flight, providing real-time weather observations. These reports are crucial for weather forecasting, air traffic control, and flight planning.

ICAO Doc 4444

Air-report. A report from an aircraft in flight prepared in conformity with requirements for position, and operational and/or meteorological reporting.

4.12.4 Compilation and transmission of air-reports by voice communications

4.12.4.1 Forms based on the model AIREP SPECIAL form at Appendix 1 shall be provided for the use of flight crews in compiling the reports. The detailed instructions for reporting, as given at Appendix 1, shall be complied with.