Weather Monitoring

An introduction to monitoring the weather
An overview of the requirements for monitoring meteorological parameters
The global view
Monitoring the weather conditions around us has always been important and will become more so in the future considering the current general warming over much of the earth. Understanding and monitoring the global weather systems is a vast and complex undertaking consuming many of the world's most powerful computers. Information is gathered to provide our daily weather forecasts and predictions on what to expect for the following 3 to 5 days. Many forms of travel are affected by the vagaries of the weather particularly the aviation industry with costly and annoying delays causing customers problems when they become stranded at airports due to unexpected fog, ice or snow. Our supply of food, crops and other seasonal commodities rely on having favorable weather conditions for their growth or harvest so it is extremely important to understand the global effects of the changes to our climate.

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Local not global
Many situation, however, require an intimate knowledge of the weather conditions on a local scale rather than globally or even nationally. Large petrochemical companies need to know which way the wind is blowing and how strong it is in case of accidental escapes of product to the atmosphere. In such hazardous material releases a quick response is required and a real time knowledge of local conditions is necessary to deal with such problems. In the past such organizations may have relied on the information from the nearest airport where such monitoring is the norm. But if there are large obstacles between them such as hills or mountain ranges the information will not be properly relevant due to distance effects. Other users include government organizations concerned with homeland security, agricultural departments studying crop growth, small harbors or airports, large quarries or opencast mines etc.

Portability is the key
 The local ability to respond to problems immediately virtually dictates that large and medium sized organizations who manufacture or process hazardous material need to be able to know what is happening on their own site and at key positions around a large installation. Portable weather stations such as the Casella Nomad system can provide cost effective information to the responsible supervisor or environmental officer. Because of the distances involved for a large site more than one outstation will often be needed and an ability to have a wide range of communication options is a big asset of the Casella Nomad system. Results can be passed back to the central controlling computer by direct cable, radio modem or GSM wireless phone.
 
typical fixed position weather station at an airport
What measurements are needed
Traditional weather measurements used fixed locations to mount a variety of sensors out of the direct influence of the sunlight to collect maximum and minimum air temperature, humidity, air pressure within a standard Stevenson screen type enclosure. Often located in school grounds or other private areas such as hospitals or government buildings they required someone to visit on a regular basis to read the dials and record results daily or hourly depending on circumstances. Hand held wind speed and direction indicators could be carried out to the site to collect relevant information manually. Rainfall gauges give the amount of precipitation over a given interval and then often need to be emptied to collect the next periods rain fall. All of these parameters and more are required to fully understand the behavior of the weather at any given instant or period of time.

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traditional Stevenson screen with temperature sensors
Meteorological parameters typically collected
A wide range of high quality sensors are provided to obtain the required information in the Casella weather monitoring systems. These include;
 *  wind speed using an anemometer
 *  wind direction using a wind vane
 *  ambient air temperature using a precision thermometer
 *  ambient air pressure
 *  relative humidity
 *  sunshine hours using a solarimeter
 *  rainfall using a tipping bucket rain gauge
Other parameters that are often useful in agricultural or crop studies include;
 *  soil temperature
 *  grass temperature
 *  leaf wetness
 
heated tipping bucket rain gauge prevents mechanism from freezing
Automatic collection of data
Considering the wide range of possible sensors that may be needed and the interval of data collection required to understand the local conditions a large amount of results can be produced by even a single weather monitoring station. Data storage is an important aspect of any such system as is the means of communication with the control center. For short periods of a few hours or days the on board memory will be sufficient to log relevant data and the stations can be accessed by visiting the site. For longer periods such as a few weeks or even months then larger volumes of results will be gathered and will need to be accessed perhaps on a daily basis for reporting purposes. Compact Flash (CF) cards enable industry standard storage media to be used and then accessed in the control computer. Capacities enabling many years of data storage even at short intervals are now available with such cards. Communication in these cases can be by direct cable link if the weather station is on the roof of a building or on the site boundary. Low power radio modems allow transmission of results up to a few miles back from a reasonably close site. The ability to use GSM wireless cell phone communication (where such services are available) greatly helps in getting the results where and when needed by simply dialing into the required outstation and downloading as often as required. The Casella Sensus control unit at the heart of every Nomad weather station can take care of all these requirements very easily.
example of a wind rose display showing predominant wind direction
this page last updated : Friday May 26, 2006