Measuring the Weather

San Francisco Bay clouds

October began with rain, and snow in the mountains. The rain liberated the grass and weed seeds which had slumbered within their hard shells all summer. Fresh green grass pushed up through last season’s dry stubble. Weed seeds emerged as tiny paired leaves. The tight buds of the coyote bush opened to fuzzy white flowers. A second spring some call it—all brought on by the first rains of the fall season, with days still warm enough and long enough to urge on the new growth.

The last three weeks of October were rainless. By the end of the month, with daytime temperatures still even in the 70s, those thrusting blades of grass had lost their newborn intense green and were looking limp. Crickets continued their stridulations in the garden after dark, and bees and skipper butterflies worked the still-blooming sages by daylight.

Months, let alone seasons, rarely divide themselves in a tidy manner. But no sooner had I flipped the page of the calendar to November, cold, wet, and blustery weather arrived. The air was chilled and tangy with all the commingled odors of the new season.

At last there was weather to measure—changes in the barometer as storms come and go, wind velocities and directions to observe, and best of all rainfall totals to note. As a volunteer weather spotter for the US weather bureau, properly known as the National Oceanic and Atmospheric Administration (NOAA), I report noteworthy weather events on my hillside location such as “hail of any size, snowfall of any amount, thunder and lightning, rainfall of one-quarter inch or more in one hour, wind estimated or measured at 40 mph or more.”

WeatherBug instrument collecting
data on the roof at the Hall.

At the Lawrence Hall of Science, a quarter mile south of my house at the same elevation, the weather is measured with instruments provided by WeatherBug, a commercial outfit which supplies equipment and records weather information for various clients, including TV stations. The information recorded at the Hall is posted on the easy-to-access website The View from the Lawrence Hall of Science. Along with the weather data you can view a time-lapse movie of yesterday’s weather.

WeatherBug also provides equipment for the UC Botanical Garden a half mile away, down in Strawberry Canyon. The Garden has set up two other weather stations which collect rainfall and record high and low temperatures. The rainfall totals are sent to the Water Resources group at the County of Alameda Public Works. The Garden, with a collection of plants from all over the world, including from desert and subtropical regions, has a big stake in the weather.

Weather data collecting systems at the Botanical Garden and LBNL.

The weather-recording locations on a hillside and in the canyon reflect our “hill and dale” topography and the microclimates which topographic variations produce. Winter mornings are often much colder in the canyon, while warm summer or fall days and evenings are hotter on the hillside. On September 22 at 9 pm, the temperature at the Hall was 77 degrees F, while at the Botanical Garden in the canyon the temperature was 63.4 degrees F—a difference of 14 degrees! Both locations record considerably more rainfall (25-50% more) than stations in downtown Berkeley. The clouds rise as they encounter the hills in what is called orthographic lifting. Rising air cools, releasing more rain.

At Lawrence Berkeley National Laboratory, which occupies the south-facing slope of Strawberry Canyon, weather is recorded with sophisticated equipment, most of which is mounted on a 65-foot steel tower. (The rain gauge is located at ground level). As a Department of Energy research laboratory, LBNL is required to continually assess its operations’ environmental impact, including collecting and analyzing certain meteorological data, says meteorologist Pat Thorson in the LBNL Environmental Services Group.

The weather equipment is wired to a data logger at the base of the tower, which processes and transmits the information over the Lab’s network, to a computer which produces accessible and elegant readouts in real time for the LBNL staff to review.

Near-shore wave-rider buoys
transmit data to NOAA.

For the regional picture and beyond you can look to the information provided by NOAA, which employs 16 meteorologists in the regional Monterey office. Weather information is broadcast at regular intervals from a transmitter atop Mt. Pise in San Mateo County and includes information from offshore buoys. The near-shore wave-rider buoys transmit water temperatures, wave heights and the period between waves. Larger buoys also report air pressure and wind velocities. From land-based locations comes other information.

Each broadcast cycle includes 2-3 day forecasts for the Bay Area, for Santa Clara Valley and San Jose, for the Highway 40 and 50 corridors in the Sierra Nevada, and a long-range forecast extending out a week. With much faster computer models, meteorologists now have more confidence in their long-range forecasts.

Weather balloon
parachute instrument launch.

NOAA Meteorologist Tom Evans says that the weather data “work horse” continues to be weather balloons, launched twice a day at noon and midnight Greenwich Mean Time from 800 hundred locations worldwide. The local balloon is launched at 4 pm and 4 am from Oakland Airport. The balloons rise 100,000 feet into the atmosphere. When a balloon bursts (because of unequal pressure within and outside the balloon), a parachute attached to the instrument package deploys. The instrument package, enclosed in styrofoam and containing various sensors, a radio transmitter, a GPS, and a circuit board for collating data, falls slowly back to Earth.

Satellites, both geostationary and pole-to-pole orbiting, also provide data. The information provided by volunteer weather spotters helps meteorologists make decisions about short-term forecasts, advisories, and warnings.

A NOAA weather radio is a must for every weather buff. What a delightful way to end the day listening to the forecast, and then imagining a buoy bobbing on the heaving seas, or envisioning the wind of a certain velocity swaying the trees on Angel Island, or knowing that a well-organized storm, rich with rainfall, is approaching the coast as you drop off to sleep.

—Phila Rogers