COMPUTATION OF PHYSIOLOGICAL INDICATORS FROM OBSERVED DATA

Q82. How does pack ice normally drift in the Northern Hemisphere during winter? Q83. Where do most of the world’s icebergs originate? Q84. What is the most important influence us to the movement of icebergs? Q85. What publication provides detailed instructions for reporting ice in the sea? COMPUTATION OF PHYSIOLOGICAL INDICATORS FROM OBSERVED DATA LEARNING OBJECTIVES: Define heat stress. Identify the signs of heat exhaustion and heat stroke. Define relative humidity (RH) and identify how relative humidity and the General Heat Stress Index (GHSI) relate to heat stress. Describe the procedure used to compute GHSI. Identify the difference between the GHSI computed by weather personnel and the Wet- bulb Globe Temperature (WBGT) index used by some military personnel. Explain the effects of cold on the body. Define wind chill temperature and describe the procedure used to determine wind chill temperature. Explain seawater immersion survivability. In the Navy and Marine Corps, all personnel routinely vary their activity and must wear clothing appropriate for the activity they expect to engage in. How "hot" or "cold" the weather is plays an important part in both operational and training activities, and is especially important in physical readiness training. The temperature is also a factor in off-duty recreational activities. Ashore and aboard ship, weather office observers are routinely asked for various readings used as indicators for the effects of temperature on the human body. In this section, we discuss heat stress and the effects of cold on the human body, as well as the values and indicators operational planners use to avoid exposing personnel to these hazards. HEAT STRESS Heat stress is the effect of excessive heat on the body, and the inability of the body to get rid of excess heat fast enough to maintain an internal temperature balance. Sweating is a sign that the body is functioning normally to maintain its heat level. Now let’s consider two types of heat stress: heat exhaustion and heat stroke. Signs of heat exhaustion include profuse sweating with a pale skin color, drowsiness, headache, nausea, vision disturbances, or muscular cramps. Heat exhaustion is a dangerous condition and should be promptly treated. Heat stroke is indicated by a lack of sweating with a hot, dry, red skin, dizziness, restlessness, confusion, or unconsciousness. Heat stroke is a potentially fatal condition requiring immediate medical assistance. Once a body has been heat stressed, the body’s tolerance to heat decreases to a certain degree. Since heat stress will result in permanent physiological changes and may result in death, heat stress should be avoided. Two heat-stress-related indicators, relative humidity and the General Heat Stress Index (GHSI) are routinely computed by weather observers to serve as guidelines for exposure to high heat situations. An additional indicator, the wet-bulb globe temperature, is frequently used as a heat stress indicator in certain situations, but is not routinely computed by weather observers. Relative Humidity Relative humidity, commonly abbreviated "RH," is the ratio of how much water vapor is in the air compared to the amount of water vapor, at the current temperature and pressure, that the air can possibly hold, expressed as a percentage. Without adding water vapor to or extracting it from the air, the relative humidity will fall as the temperature rises during the day; and as the temperature falls at night, the relative humidity will rise. The measurements that provide us with the value of water vapor the air can possibly hold are the observed air temperature and the observed pressure. The measurement that yields a value of water vapor actually held by the air is the dew-point temperature, which is calculated from the dry- and wet-bulb temperatures. Relative humidity is also the most requested indicator of heat effects on the body because it has been in use longer than any other, Just about everyone with an elementary education realizes that when relative humidity is high, the air feels hotter, and when the relative humidity is low, the air feels cooler. when the humidity is high, moisture does not evaporate efficiently from the skin, and the body temperature rises. But when the humidity is low, moisture on the skin evaporates rapidly and provides very efficient cooling of the body. Because of its widespread usage, 1-55