The estuary weather station

Bennett's Point stands in a grassy field about 90 m from Mosquito Creek, a tributary of the Ashepoo River; the nearest obstructions to the wind are oak trees 25 m to the south and southwest. A galvanized steel tower lifts the wind monitor and the light sensor to a crossbar at its top, 6.1 m above the ground, and holds the temperature and humidity probe about halfway up, at 3.35 m. The logger and the barometer share a weatherproof box low on the tower, with the barometer at 1.5 m. A solar panel on an arm faces east, tilted at about 47°, and charges the battery. The rain gauge stands apart, 2.5 m southeast of the box on a level concrete platform, with its rim 1.3 m up.

Heights differ from reserve to reserve. At Jobos Bay in Puerto Rico, a 10 m galvanized tower built to the program's procedures carries the wind sensor at 9.75 m and the light sensor at 9.6 m, the temperature and humidity probe and the barometer at 2.7 m, and the rain gauge 1.0 m up, 3.8 m from the tower. Wind is weaker near the ground, so speeds from stations of different heights are not strictly comparable.

Wind comes from an R.M. Young 05103 wind monitor: a four-bladed polypropylene propeller 18 cm across, whose rotation gives the speed, held into the wind by a vane with a 38 cm turning radius, whose angle gives the direction. Its manufacturer states ±0.3 m/s or 1% of the reading, and ±3°.

Air temperature and relative humidity come from one probe, an E+E EE181, inside a shield of stacked plates that keeps off the sun and rain and lets the air through. Its humidity is stated to within about ±1.3% plus 0.3% of the reading between −15 and 40 °C, up to 90%; it reports no more than 100%.

Pressure is measured by a Vaisala PTB110 barometer inside the box: ±0.3 hPa at 20 °C, ±0.6 hPa between 0 and 40 °C, and drifting no more than 0.1 hPa a year.

Light is measured as photosynthetically active radiation (PAR): the light plants use, nominally 400 to 700 nm, counted as photons. Bennett's Point uses an Apogee SQ-110, whose waveband is 410 to 655 nm, in place of the earlier LI-COR LI-190.

Rain falls into the funnel of a Texas Electronics tipping-bucket gauge and runs into one side of a small seesaw. When that side holds 0.01 inch (0.254 mm) of rain, it tips, empties, and brings the other side under the funnel; a magnet passing a switch signals the logger, which counts the tips. The manufacturer states ±3% at rates of 1 to 6 inches (25 to 150 mm) an hour. An unheated gauge like this undercounts snow, and strong wind carries some drops past the funnel.

A Campbell Scientific CR1000 logger reads the sensors every 5 seconds and saves a record every 15 minutes. Unlike the water-quality sonde's single reading, most of what it saves is an average over the 15 minutes: air temperature, humidity, pressure, wind speed and wind direction. It also saves the highest wind speed among the 5-second readings, which is the gust, and the spread of the wind's direction; the highest and lowest air temperature; and the totals of rain and of light over the period.

Each record is time-stamped at the end of its period, in local standard time all year: the midnight record holds the averages and totals for 23:45 to 23:59. The reserve downloads the logger monthly, checks it against a handheld weather meter, cleans the sensors and cuts back plant growth around them. The sensors are sent back for calibration on a schedule: temperature and humidity and the rain gauge yearly, wind every one to two years, pressure and light every two, and the logger every five.

Every hour, the transmitter in the box sends the last four 15-minute records to a GOES weather satellite, and from there they go to the reserves' Centralized Data Management Office. They are checked automatically and become provisional data; the full record from the logger is later reviewed by the reserve and checked again by the office before it becomes authoritative.

Bluegraph reads these stations from NOAA's National Data Buoy Center, whose files carry only part of the record, once an hour: wind speed and direction, pressure and its change over three hours, air temperature, and the dew point, calculated from the temperature and humidity. The values are rounded: the wind to whole knots (about 0.5 m/s) and 10°, and the pressure to whole hectopascals. NDBC's files carry no gust, rain or light for these stations, so Bluegraph doesn't show them. You can find the stations on the stations list, among the estuaries, and the reserves' water-quality sondes on their own page.