![]() ![]() Delineating between new snow and old snow presents a challenge. New Snow - New snow is the incremental amount of snow that has fallen since the last snow depth observation. Even with careful placement, all gages underestimate the real precipitation, particularly with snowfall. Measurement errors can also result from small amounts of dew, frost, and rime accidentally included in the total measured precipitation. Strong winds during precipitation events can cause considerable differences between measured and actual precipitation. The biggest factor in precipitation measurement error is wind. Precipitation intensity and duration, useful information for many NRCS design activities, can be derived from information gathered by precipitation gages. Most recording gages store information on a paper strip, which is generally changed weekly by an observer. Recording gages have instrumentation which records the time, duration, and intensity of precipitation. Non-recording gages simply collect precipitation amount of precipitation must be measured by an observer. precipitation gage has an eight inch diameter mouth and height of about 30 inches. Dew, frost and rime are excluded, since they are a result of water vapor in air condensing or freezing onto a surface. ![]() It is one of the most basic data elements collected by any climate station. Precipitation includes, but is not limited to, rain, drizzle, snow, hail, graupel, sleet, and ice crystals. Precipitation - Precipitation refers to all forms of water, liquid or solid, that fall from the atmosphere and reach the ground. The water depth is measured daily and adjusted for any precipitation which may occur. Accurate evaporation readings requires careful maintenance of an evaporation pan which contains water. Evaporation varies with latitude, altitude, season, time of day, and sky condition. ![]() Evaporation is influenced by solar radiation, air temperature, vapor pressure, wind, and possibly atmospheric pressure. For more information on instrument shelters, see the Weather Station Handbook - an Interagency Guide for Wildland Managers.Įvaporation - Evaporation is the physical process by which a liquid is transformed to a gaseous state. Instrument shelters are designed to rectify this problem. It is important that thermometers be shaded from sunlight to avoid an erroneously high measured temperature. Air temperature is usually measured with either a liquid-in-glass maximum and minimum thermometer mounted in a vented, wooden box or with an electronic sensor. The Fahrenheit scale is used most frequently in the US and Centigrade throughout the rest of the world. The Fahrenheit and Centigrade temperature scales establish the freezing of water at 32/0 degrees respectively and boiling point at 212/100 degrees respectively. It is measured on some definitive temperature scale. This does not mean that climatic data with less than 30 years of data cannot be analyzed, but that some adjustment be made to estimate what a 30 sample set would produce.Īir Temperature - Temperature is a measure of the hotness or coldness of air. An important rule governing small sample analysis requires a minimum of 30 samples. Any statistical analysis of climatic data, due mainly to the limited number of samples available, must follow the rules for statistical analysis. Statistical analysis of climatic data generates descriptive information which reflects the average atmospheric conditions at a location, as well as generating probabilities that extreme events will occur. The following description of climatic data elements is a condensation of the material contained in the National Weather Service Observing Handbook No.2, Cooperative Station Observations, the Weather Station Handbook and Interagency Guide for Wildland Managers, and the American Meteorological Society Glossary of Meteorology. Common data element durations available for the station could include monthly, daily, or hourly. Descriptive terminology for climaticdata elements are:Įlement Name - The full description of the element being referenced at the climate station (e.g., maximum temperature).Įlement ID - Is a shortened identifier for the element, usually 4 characters in length (e.g., TMAX (maximum daily temperature), TMIN (minimum daily temperature), PRCP (precipitation, etc).Įlement Duration - The interval between measurements of a data element. A climatic data element is a measured parameter which helps to specify the climate of a specific location or region, such as precipitation, temperature, wind speed and humidity. ![]()
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