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Notes and Information about the Meteorological Data from the
Ada & Archibald MacLeish Field Station
Collection Site Details and Procedures
The MacLeish Field Station weather collection site is located at the end of Poplar Hill Road
in Whately, Massachusetts, USA (Lat: 42 deg. 26 min. 56 sec. N Long: 72 deg. 40 min. 50
sec. W). The meteorological instruments (except the rain gauge) are mounted at the top of
a tower 25.3 m tall, well above the surrounding forest canopy. The tower is located on a
local ridge at an elevation 77 m above sea level.
Please contact Paul Wetzel (pwetzel@smith.edu) with any questions.
Special Notes
Relative humidity and temperature are measured with a R.M. Young Co., Model 41382, relative
humidity and temperature probe. The probe is housed in a radiation shield and ambient air is
continuously blown past the sensor to reduce temperature fluctuation from solar radiation. The
calibrated measuring range of the temperature probe is -50 to +50˚C, with an accuracy of ±0.3˚C.
The relative humidity probe has an accuracy of ±2%.
Precipitation is measured using a Campbell Scientific 8” heated siphoning tipping-bucket rain gauge
located on the ground. The bucket tips when 0.01 inches (0.254 mm) of precipitation accumulates.
The rain gauge has a precision of +/– 2% for rainfall intensities up to 19.7 in/hour (500 mm/hr).
Note that if there is a large amount of snowfall it will take 1-3 days for all of the snow to melt
and be recorded by the gauge. This is especially true if large snowfalls occur during or are
followed by very cold temperatures. The result is that large snowfall events look like
extended precipitation events.
Wind velocity and direction are measured with a 2-axis, non-moving parts, ultrasonic anemometer
(R.M. Young, model 85004). Wind measurements are based on the transit time of ultrasonic pulses
between four transducers. The transit time between the transducers is altered as the wind blows to
calculate wind velocity. Wind direction is determined from relative velocities along each acoustic
path. The unit is heated to prevent ice and snow buildup. The anemometer has a wind speed range
of 0–70 m/s, with accuracy in the 0–30 m/s range of ±2% or 0.1 m/s. The wind direction accuracy
is ±2%.
Barometric pressure is measured with an R.M. Young barometric pressure sensor, model 61202V.
The operating temperature is –50 to +60 ˚C, with an accuracy of ±0.3 hPa at 20 ˚C.
A pyranometer (Kipp & Zonen, model CM 3) measures solar radiation received in the horizontal
(180 degrees) field of view. Typical accuracy is ±5%.
MacLeish Station Data Notes
Page 1
Data Format
Files containing 10 minute data are organized in the following column order:
1. Date/Time (24 hour clock)
2. Date/Time (24 hour clock) in decimal format
3. Air Temperature (˚C)
4. Wind Speed (m/s)
5. Wind Direction (degrees)
6. Relative Humidity (%)
7. Atmospheric Pressure (mb)
8. Solar Radiation (watts m-2)
9. Precipitation (mm)
Files containing daily data with maximum and minimum values and the times that those
values happened during the day are organized in the following column order:
1. Date/Time (24 hour clock)
2. Date/Time (24 hour clock) in decimal format
3. Mean Air Temperature (˚C)
4. Max. Air Temperature (˚C)
5. Time of Max. Air Temperature (˚C)
6. Min. Air Temperature (˚C)
7. Time of Min. Air Temperature (˚C)
8. Mean Wind Speed (m/s)
9. Mean Wind Direction (degrees)
10. Max. Wind Speed (m/s)
11. Time of Max. Wind Speed (m/s)
12. Min. Wind Speed (m/s)
13. Time of Min. Wind Speed (m/s)
14. Mean Relative Humidity (%)
15. Mean Atmospheric Pressure (mb)
16. Mean Solar Radiation (watts m-2)
17. Total Daily Precipitation (mm)
In the event of ties for the timing of minimum and maximum events, the last time
during the day that the event occurred is the value recorded.
MacLeish Station Data Notes
Page 2
Time Correction
Data at the MacLeish meteorological station is collected on Eastern Standard Time (EST).
There is no change made for daylight savings time. The calendar and Julian dates of
standard and daylight savings times are given in the table below.
Year
Daylight
Savings
Time
Begins
Daylight
Savings
Time Begins
(Julian Date)
Standard
Time Begins
2009
2010
2011
2012
2013
2014
2015
March 8
March 14
March 13
March 11
March 10
March 9
March 8
67
73
72
71
69
68
67
November 1
November 7
November 6
November 4
November 3
November 2
November 1
MacLeish Station Data Notes
Standard
Time
Begins
(Julian
Date)
305
311
310
309
307
306
305
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