CHAPTER 1 SURFACE OBSERVATION ELEMENTS

CHAPTER 1 SURFACE OBSERVATION ELEMENTS INTRODUCTION In this chapter, we give you an overview of Surface Weather Observations and provide references for observation procedures. We also discuss some of the important values that weather observers calculate from observed data. These values include both physiological indicators and aircraft performance indicators. Physiological indicators are values that help estimate the effects of weather on the human body, and aircraft performance indicators are values that allow aviators to assess the effects of weather on aircraft. CONDUCTING OBSERVATIONS LEARNING OBJECTIVES: Identify measurement systems and time standards used while conducting surface weather observations. Recognize the general order in which elements are routinely observed. Throughout the Navy and Marine Corps, Aerographer’s Mates, Quartermasters, and Marine Corps weather observers use similar techniques and procedures to determine the current weather conditions. Accurate and timely submission of environmental observations are basic to the development of oceanographic and meteorological forecasts and tactical indices used in support of fleet operations. The methods used aboard ship differ slightly from those used at shore stations. In this section, we discuss procedures used both aboard ship and ashore. Some weather elements are observed by using different criteria, depending on the recording format and reporting code used. As of July 1996, all U.S. Navy weather activities have adopted the Aviation Routine Weather Report (METAR) and the Aviation Selected Special Weather Report (SPECI) codes for weather 9 observation procedures. The criteria for these codes are 5 covered in detail in chapter 3 of this module. The criteria for U.S. Navy surface aviation weather 5 observations ashore are contained in Surface METAR Observations User’s Manual, NAVMETOC- 9 COMINST 3141.2. There are minor differences in observation criteria between U.S. shore stations and activities located outside of the continental United States (OCONUS). These differences are highlighted in the manual. United States Navy Manual For Ship’s Surface Weather Observations, NAVMETOC- COMINST 3144.1, is used for shipboard weather observations. Except when necessary, we will not repeat information covered in those manuals, but will refer you to the manual. Before discussing the procedures or methods used to observe weather elements, let’s review some basics about observing and measuring the elements. MEASUREMENT SYSTEMS In the mid-1970's, the United States began switching to the metric system for weights and measures. In the field of military meteorology and oceanography, it is common to measure an element by using units from the old system and then converting the measurement to the metric system. Because of this, weather observers should be well versed in both systems and be able to convert units of length, volume, temperature, pressure, and mass. Appendix II of this module contains tables and conversion factors to convert from one system to another. Weather observers make temperature conversions most frequently. The three temperature scales used are the Fahrenheit, Celsius, and Kelvin scales. The United States and several other countries still use the Fahrenheit scale, which fixes the freezing point of water at 32°F and the boiling point at 212°F. Most of the world uses the Celsius scale, which fixes the freezing point of water at 0°C and the boiling point at 100°C. In meteorology and oceanography, both temperature scales are used, with frequent conversions between the two. Conversions may be made by using a conversion table or by using the following formulas: F = –C + 32 or C = –(F – 32) where F is degrees Fahrenheit, and C is degrees Celsius. 1-1