While drought and climate change affect the supply side, population growth is expected to affect the demand side of water availability. Florida has experienced at least one severe and widespread drought every decade since 1900, and climate change projections show that meteorological droughts will occur more often in the future. In the United States, Florida ranks second among states for both value and land area of vegetable production, but this production is affected by periodic droughts. The wet-bulb thermometer is cooled to the lowest value possible. Water evaporates from the wick on the wet-bulb thermometer and cools the thermometer due to the latent heat of vaporization. After the wick is dipped in distilled water, the sling psychrometer is whirled around using the handle. One thermometer measures the air (dry bulb) temperature while the other one measures the wet-bulb temperature. The sling psychrometer consists of two liquid-in-glass thermometers. With a sling psychrometer, air flow is created by rotating the two thermometers through the air by hand (Fig. For an accurate reading, the wet bulb thermometer must have air moving over it. "Psychros" comes from the Greek work meaning "cold," and hence a psychrometer measures humidity by determining how much colder the wet bulb thermometer is than the dry bulb thermometer. With a psychrometer, one determines how much cooler the wet bulb is than the dry bulb and then calculates humidity by using appropriate graphs or tables. The wet bulb thermometer is kept wet by a moistened cotton wick or sleeve. A psychrometer is a device used to determine atmospheric humidity by reading the wet bulb and dry bulb temperatures. Thus, more damage can potentially occur during a windy freeze. Thus, the length of time a grove will be at low temperatures can be longer on a windy night than on a calm one. If the leaf is wet and water is not freezing on it, the leaf can theoretically cool to the wet bulb temperature. In a windy freeze, temperature of a dry leaf is usually fairly close to air temperature. Even though wind chill does not apply to plants, wind can remove heat from a grove rapidly. It does not apply to plants or vegetation. Wind chill was developed to estimate heat loss rate from humans and other warm blooded organisms. chill refers to the cooling effect of moving air on a warm body and is expressed in terms of the amount of heat lost per unit area per unit of time.
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