Chapter 1 presents an introductory overview of surface weather observations. Chapter 2 discusses the surface weather observation program, types of observations, criteria for specials, general observing standards, and dissemination. Chapter 3 presents the certification and quality control standards. It discusses certification of observers and quality control performed on-site, and at remote locations. Chapter 4 defines the requirements for maintaining records of surface weather data. It discusses the types of records, preparation and maintenance of the Station Information File, types of storage, and procedures for maintaining records of surface weather data. Chapters 5 through 11 focus on a specific element (e.g., Visibility is an element) and all the associated parameters (e.g., Prevailing Visibility and Sector Visibility are visibility parameters) of that element that appear in the weather report. The elements are: Wind (Chapter 5), Visibility (Chapter 6), Runway Visual Range (Chapter 7), Present Weather (Chapter 8), Sky Condition (Chapter 9), Temperature and Dew Point (Chapter 10), and Pressure (Chapter 11). Each chapter contains a similar format: a brief overview of the chapter, a section that describes parameters, and a section that defines further the observing and reporting standards for the reports. Each chapter also contains a Summary Table that offers an abridged listing of standards described in the chapter. By design, these summary tables do not contain all of the details found in the text. Therefore, these tables should only be used as an overview of the standards contained in the chapter. Chapter 12 defines the coding procedures for reports in the METAR/SPECI format. Appendix A is a Glossary. Appendix B is a list of Abbreviations and Acronyms. Appendix C lists Sensor Standards. Appendix D contains Runway Visual Range Tables. Throughout this Handbook, the following definitions apply: a. "shall" indicates a standard is mandatory. b. "should" indicates a standard is recommended. c. "may" indicates a standard is optional. d. "will" indicates futurity; it is not a requirement to be applied to standards.

This manual implements Air Force Policy Directive (AFPD) 15-1, Atmospheric and Space Environmental Support. It also implements Federal Meteorological Handbook No. 1 (FCM-H1) and the World Meteorological Organization (WMO) Manual on Codes, Volume I.1, Part A (WMO 306, Vol I.1, Part A) aerodrome routine meteorological reports (FM-15 METAR) and aerodrome special meteorological reports (FM-16 SPECI) codes. It prescribes basic observing fundamentals and terms and establishes aviation code forms for recording and disseminating weather observations. It applies to all Active and Reserve Component organizations conducting weather operations, including government-contracted weather operations if stated in the Statement of Work or Performance Work Statement.

An overall increase in global-mean atmospheric temperatures is predicted to occur in response to human-induced increases in atmospheric concentrations of heat-trapping "greenhouse gases." The most prominent of these gases, carbon dioxide, has increased in concentration by over 30% during the past 200 years, and is expected to continue to increase well into the future. Other changes in atmospheric composition complicate the picture. In particular, increases in the number of small particles (called aerosols) in the atmosphere regionally offset and mask the greenhouse effect, and stratospheric ozone depletion contributes to cooling of the upper troposphere and stratosphere. Many in the scientific community believe that a distinctive greenhouse-warming signature is evident in surface temperature data for the past few decades. Some, however, are puzzled by the fact that satellite temperature measurements indicate little, if any, warming of the lower to mid-troposphere (the layer extending from the surface up to about 8 km) since such satellite observations first became operational in 1979. The satellite measurements appear to be substantiated by independent trend estimates for this period based on radiosonde data. Some have interpreted this apparent discrepancy between surface and upper air observations as casting doubt on the overall reliability of the surface temperature record, whereas others have concluded that the satellite data (or the algorithms that are being used to convert them into temperatures) must be erroneous. It is also conceivable that temperatures at the earth's surface and aloft have not tracked each other perfectly because they have responded differently to natural and/or human-induced climate forcing during this particular 20-year period. Whether these differing temperature trends can be reconciled has implications for assessing: how much the earth has warmed during the past few decades, whether observed changes are in accord with the predicted response to the buildup of greenhouse gases in the atmosphere based on model simulations, and whether the existing atmospheric observing system is adequate for the purposes of monitoring global-mean temperature. This report reassesses the apparent differences between the temperature changes recorded by satellites and the surface thermometer network on the basis of the latest available information. It also offers an informed opinion as to how the different temperature records should be interpreted, and recommends actions designed to reduce the remaining uncertainties in these measurements.