Q82. How does pack ice normally drift in the Northern
Hemisphere during winter?
Where do most of the worlds icebergs originate?
What is the most important influence us to the
movement of icebergs?
What publication provides detailed instructions
for reporting ice in the sea?
COMPUTATION OF PHYSIOLOGICAL
INDICATORS FROM OBSERVED
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
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 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 lets consider
two types of heat stress:
heat exhaustion and heat
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.
stroke is a potentially fatal condition requiring
immediate medical assistance.
Once a body has been heat stressed, the bodys
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
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.
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,