What makes this station different?

Time interval for acquisition of measurements: 5 s, except for soil temperature and humidity 15 min.
Time interval for logging of summaries: 1 min, 1 h, 1 d.
Solar radiation measurement: currently seven types of sensors.
Soil measurements as a depth profile.
For research at the experimental field of the Viikki campus it provides on-site data.

Figure The station in the field. The trees located about 100 m North of the tower were cut at the end of the Summer of 2020.

Logger and sensors

A Campbell Scientific CR6 datalogger with a CDM-A116 analogue input module is used. The datalogger has both digital and analogue inputs. The analogue to digital conversion (ADC) is done with 24 bits resolution and auto-ranging. Data is acquired from all sensors except those in the ground once every 5 s and summaries computed and saved at 1 min-, 1 h-, and 1 d intervals. Soil sensors are read less frequently, and summaries saved at 1 h intervals. In the daily data, in addition to means, standard errors, maximum and minimum for most variables, and histograms for some radiation data, computed in the logger, are also saved. In daily data, times for maximum and minimum are also recorded. Each of the sets of summaries, 1 min, 1 h and 1 d, are stored in different tables (storage space) in the logger’s CRBASIC program and downloaded as separate text files. Data are downloaded on site through a USB connection to a laptop computer.

Figure The station in February 2017, before the cross-arm was repositioned. The crossarm is oriented N-S with the N on the right side of the photograph.

Figure View of the station after the sensors were repositioned in May 2020. The long cross-arm was moved higher up and a second, lower cross-arm oriented E-W was added for the weather sensor. Photograph in June 2020

Figure View of the station after the infrared temperature sensors were installed in November 2020 on a third cross-arm.

Radiation sensors are at > 2 m above the ground surface, on a cross arm on the South of the tower, except for the sglux ones and the CS PAR sensor that are on the North side at the opposite end of the same cross arm. The weather sensor is at 1.9 m above the ground, at the East end of an East-West cross arm 0.75 m away from the mast. The sensors were relocated in the Spring of 2020, moving the radiation sensors higher up and the weather sensor from the North to the East side of the mast. The station is powered by a battery that is charged by a mains power supply and a solar panel in parallel, ensuring uninterrupted power year-round in spite of the high frequency of measurement, and the heating of some of the sensors during winter time. The table below gives the list of sensors.

**Table** Sensors in the weather station. *signal* is how the datalogger receives the information. Sensors with mV (millivolt) output lack built-in amplifier and provide a raw electrical signal. Sensors with V (Volt) output have a built-in analogue amplifier. Signal in ohms (\(\Omega\)) is the sensor’s electrical resistance. SDI-12 is a digital serial communication protocol. In the case of analogue sensors, the digital conversion is done by the datalogger. For digital signals the conversion is done in the sensor. Most SDI-12 “sensors” like the WXT520 “weather sensor” contain sensors for multiple variables. SDI-12 communication allows the data from difference sensors to be sent sequentially using the same wires and logger inputs.
Sensor type	make	variable	qty.	signal	since
UV-Cosine (UVB)	sglux	UVB irradiance	1	0-5V	May 2020
UV-Cosine (UVA)	sglux	UVA irradiance	1	0-5V	May 2020
UV-Cosine (blue)	sglux	Blue-Violet irrad.	1	0-5V	May 2020
SKR-110 R/FR	Skye	red irradiance	1	mV	June 2017
SKR-110 R/FR	Skye	far-red irradiance	1	mV	June 2017
LI-190 quantum	LI-COR	PAR (total PPFD)	1	mV	January 2016
CS310	CampbellSci	PAR (total PPFD)	1	mV	June 2021
SMP3 pyramometer	Kipp	global radiation	1	0-1V	January 2016
BF5	Delta-T	PAR (total PPFD)	1	0-2.5V	June 2017
BF5	Delta-T	PAR (diffuse PPFD)	1	0-2.5V	June 2017
WXT520	Vaisala	Air temperature	1	SDI-12	August 2016
WXT520	Vaisala	Air humidity	1	SDI-12	August 2016
WXT520	Vaisala	Wind speed	1	SDI-12	August 2016
WXT520	Vaisala	Wind direction	1	SDI-12	August 2016
WXT520	Vaisala	Atmospheric pressure	1	SDI-12	August 2016
WXT520	Vaisala	Precipitation, rain	1	SDI-12	August 2016
WXT520	Vaisala	Precipitation, hail	1	SDI-12	August 2016
WXT530	Vaisala	Air temperature	1	SDI-12	June 2021
WXT530	Vaisala	Air humidity	1	SDI-12	June 2021
WXT530	Vaisala	Wind speed	1	SDI-12	June 2021
WXT530	Vaisala	Wind direction	1	SDI-12	June 2021
WXT530	Vaisala	Atmospheric pressure	1	SDI-12	June 2021
WXT530	Vaisala	Precipitation, rain	1	SDI-12	June 2021
WXT530	Vaisala	Precipitation, hail	1	SDI-12	June 2021
SoilVUE10	CampbellSci	Soil moisture profile	3	SDI-12	May 2020
SoilVUE10	CampbellSci	Soil temperature profile	3	SDI-12	May 2020
SoilVUE10	CampbellSci	Soil elect. cond. profile	3	SDI-12	May 2020
SoilVUE10	CampbellSci	Soil permittivity profile	3	SDI-12	May 2020
CS655	CampbellSci	Soil moisture	8	SDI-12
CS655	CampbellSci	Soil temperature	8	SDI-12
CS655	CampbellSci	Soil elect. cond.	8	SDI-12
CS655	CampbellSci	Soil permittivity	8	SDI-12
107	CampbellSci	Soil temperature profile	3	ohms	August 2020
CSmicro LT02	Optris	Surface temperature	2	0-5V	November 2020

Figure Hemispherical view from PAR sensor position. Field of view of the PAR sensor. The hemispherical photograph below was taken from sensors’ position and elevation, North at top. Taken in September 2017.

A small grove of birch trees about 100 m to the North of the station were cut in year 2020. They may have affected the wind regime to some extent from start of measurements in 2015 until the Summer of 2020. In spite of the distance to them, the tall buildings around the field are likely to disturb wind direction and speed differently in different parts of the field.