About Sandy Ridge Weather Station
Updated 14 July 2010
Sandy Ridge Weather Station, located in Elkridge, MD (Howard County) began operating in late February 2002. The station coordinates are
39o 12' 29" north latitude, 76o 46' 8" west
longitude, with an elevation of approximately 350 feet above sea level. Click here
to see maps showing the station's
- Weather Sensors
- Sandy Ridge weather data are collected with a Davis Vantage Pro wireless weather station (model
6150). The Vantage Pro integrated sensor suite includes temperature
and humidity sensors, an anemometer for wind speed and direction and a
self-emptying ("tipping bucket" type) rain collector. The temperature and humidity sensors are enclosed in
a radiation shield to ensure accuracy in direct sunlight. The
sensor suite is solar powered, but also contains a lithium battery as a back-up power source. The transmitter and battery are
housed beneath the radiation shield.
Data are transmitted via radio signal to the Vantage Pro's indoor display console.
The display console employs a digital format liquid crystal display (LCD), powered
by an AC adapter or standard C-size batteries. The console enables real-time display of
all variables, plus recall of daily, monthly and annual maximum and minimum
values, and time of occurrence. The atmospheric pressure sensor is
built into the console.
- The Vantage Pro anemometer is detachable from the rest of the sensor
suite. The anemometer is mounted on a tripod atop the roof of our house
at a height of slightly more than 30 feet (10 meters) above ground. The
core of the sensor suite, including the temperature and humidity sensors,
rain collector and transmitter are
mounted on the side of the deck in our backyard at a height of approximately 6
feet (2 meters), above grass. Our house is situated close to
the crest of a hill at one of the highest points in our development, providing
nearly unobstructed exposure to the wind on three sides. Several
tall trees along the property line behind our house will obstruct the wind
under certain conditions (see below).
- Subjective Assessment of Data Quality
- The data from this site are unofficial and are intended for personal interest use only.
- - The temperature, humidity and
wind direction readings agree well with the official readings at Baltimore-Washington
International Airport (KBWI),
which is located approximately 5 miles to the
east-southeast of Sandy Ridge.
- - The wind speeds
are also quite comparable with the official ones, but may exhibit
a slight low bias in some conditions. The low bias appears to be most noticeable with north to northeast winds during
summer, due to several tall deciduous trees just beyond the property line in
back of our house.
- - The rain collector has good
exposure, and is periodically calibrated against a graduated cylinder-type rain
collector placed nearby. The tall trees along the back
of the property line may have a "shadowing" effect which produces a low bias under northeasterly flow conditions during summer. The rain
collector contains a thermally controlled heater for measuring the liquid
equivalent of frozen precipitation. The heater works well in general, although evaporation from the heated surface of the collector
appears to produce lower than expected liquid values in some conditions. The Davis
Rain Collector Heater was purchased separately.
- - The
atmospheric pressure is corrected to sea level for display purposes and
appears to be quite accurate.
- - Derived quantities, such as the wind
chill and heat index, are computed at the Vantage Pro console or by the
graphical display package (see below) using standard
formulae and also appear to be quite accurate.
- Data Logging and PC/Internet Connection
- Collection, analysis and graphical display of the data on a PC (including
Internet capability) require additional purchase of the
Davis WeatherLink graphical
software package. The heart of the package is the WeatherLink data logger, which
provides the data storage capability and transfer connection between the Vantage Pro console and the PC. While WeatherLink provides adequate
PC and Internet display capability, I use Ambient
Software's Virtual Weather Station (VWS) graphics package
to enhance this capability (the WeatherLink data logger is still required to
transfer the data to the PC).
Both WeatherLink and VWS have built in ftp capability for uploading and
downloading data, graphical images, etc. to the web site and run on a Windows PC. The Internet connection is
via cable modem, which greatly facilitates transfer of data to the web site.
- Web Page Content
The Sandy Ridge web site was established in March 2002. Real-time data, including the 24-hr
and 7-day history graphs, are updated every 15 minutes. Pages with live data,
such as the Current Conditions, Local Area weather, etc., refresh automatically every 2½ minutes. The wind speed on the Current Conditions page is the
average wind speed during the 10 minutes (10-minute average) preceding the latest update time. The climatological summaries are updated daily, just before midnight each day. The
yearly rain is the accumulated rainfall since January 1st of the
current year. The sky conditions shown on the Current Conditions page are based
on information from both Sandy Ridge Weather Station and the latest METAR
report from BWI Airport. The visibility reported on the Current Conditions page is based on the latest METAR report from BWI. Retrieval (download) and display of the METAR reports and daily climatological data (e.g., the normal and record high/low
temperatures at area airports shown on the Extremes page) are built-in capabilities of the VWS graphics package.
Unless otherwise indicated, the radar, satellite and forecast information are obtained from the National Weather Service (NWS) and
the National Oceanic and Atmospheric Administration (NOAA).
- Weather Servers/Mesonets
- Weather servers collect data transmitted from individual weather stations, providing potentially valuable real-time and
historical data bases for education, research and use by interested parties. A Meosnet refers to a network of stations whose collective data provide
a detailed picture of weather conditions on a local or regional scale. Currently, data from Sandy Ridge Weather Station are sent in real time
to Weather Underground Data Exchange,
APRSWXNET/Citizen Weather Observer Program,
NOAA Surface Data Mesonet
Click the Local Weather tab on the web page menu to view current and historical data from Sandy Ridge Weather Station
and other participating weather observers.
- Sandy Ridge Weather Station gratefully acknowledges
Sammimishweather.com for use of its menu design.