The Design Climatology Branch of the Air Force Cambridge Research Laboratories had the scientific responsibility for leading a DoD Task Group effort to revise MIL-STD-210A 'Climatic Extremes for Military Equipment'. This document represents the fruition of the goals of the task group. It relates the background studies supporting the values in MIL-STD-210B, so that MIL-STD-210B users need to consult only this single document for an elaboration on the MIL- STD-210B extremes. In addition, the report contains information on the origin, necessity for and the events leading to a revision of MIL-STD-210A. Discussions of the major changes in the Standard's philosophy and its contents are also provided.

Design of certain Air Force systems intended for world-wide usage requires knowledge of the possible joint extremes of high temperatures with high humidity. Previous studies have addressed themselves to this problem, but the statistics reported therein were not presented in terms of joint occurrence frequencies. This study presents joint values of temperature (to 120F) and dew point (to 93F) equalled or exceeded from 0.1 to 80% of the time (hours) in the world's severest joint high-temperature, high-humidity environment (Abadan, Iran). These values are compared with the joint high-temperature, high-humidity criteria presented in Military Specification MIL-E-38453A. This comparison indicates that the use of MIL-E-38453A can lead to overdesign at temperatures above 120F and to underdesign at lower temperatures.