| 24 Oct 2025
Ground-Based Atmospheric Measurements at the Onsala Space Observatory (Sweden): Data & Trends (2009–2025)
Abstract. This study presents a comprehensive long-term dataset of ground-based atmospheric observations collected at the Onsala Space Observatory (OSO), Sweden, between August 2009 and April 2025. The dataset includes measurements of temperature, relative humidity, atmospheric pressure, precipitations, wind speed, gust and direction, and solar irradiance. It offers high-resolution insight into local weather patterns and seasonal variations, making it a valuable resource for climate monitoring and regional environmental studies. Preliminary analysis reveals a warming trend of ∼0.15 °C.yr-1, with significant seasonal contrasts: the most pronounced increase occurs in winter (203.3 % above the annual trend, so winters are becoming milder), followed by autumn (80.1 %), spring (62.3 %), and summer (32.9 %). Precipitation trends show a significant decrease over the study period. Anomalies such as the particularly cold winters in 2009–2010 and 2010–2011 or the particularly warm winter in 2019–2020 are highlighted and linked with the North Atlantic Oscillation (NAO) phases. This dataset complements existing data for local trend analysis and atmospheric modeling in northern Europe.
The authors are clear that the intention of the paper is to introduce the observations and the site, not the presented analysis of the data. However the presentation of the data reviles insights in interpretations of the description and is thus useful. To be a useful article there are some details about the observations that must be added. For example the placement of the sensors, the resolution of the sensor and how certain variables are defined.
The presented analysis and interpretation is a bit trivial, but showcases the data set.
I would recommend the article for publication if they clarify it.
Specific comments:
Figure 1 gives an overview of the location of the instrument mast, but the picture is almost not showing the tower. I would highly recommend a better picture of it. In the text, at line 68, it is referred to as a "concrete tower".
Line 68: Has the sensor been the same for the whole measuring period? It is relevant for the humidity observations where capacitive sensors are known to drift in RHmax value with time.
How is the sensor placed on the tower. I cant tell from the picture. Is it placed on top of the tower or on the side on a boom (in htet case in wich direction?)?
Line 70: It is unclear if wind (speed and direction) is measured with the Vaisala weather transmitter WXT520 or with an additional separate sensor. It is also not clear how the Vaisala weather transmitter WXT520 is mounted on the tower.
Table 1:
It is unclear if the observations are made at 16.1 m above sea level, or at 16.1 meter on the tower. Or is the base of the tower located at sea level?
Rain rate (RR [mm/h]): According to the text rain rate is based on minute observations (line 73 and 168). Explain how this is done. Is it the maximum minute value that is used or ..?
Rain24: Accumulated precipitation during 24 can within meteorological data either be 00-24 or morning to morning (06-06 UTC).
The resolution of the sensors are missing in the table.
In which direction is the pyranometer mounted on the tower? If it is mounted on the tower it must be shaded by the tower part of the days.
Line 79-80: How are clear and cloudy pixels defined?
Line 84: Here is the additional pyranometer placed. The height is given but not the location (on the mast or on a separate structure)?
Line 102: It is unclear which pyranometer the text is referring to.
Line 136: I am curious about the very few days of fog in the RH data. Since OSO is located in a costal region I would expect to see at least some occurrence of foggy days. I agree that the drift in RH value is low for most of the time period, but from 2020 it is increasing by about 2% per year. Has the sensor been replaced or recalibrated during the time period?
Figure 2: Is a) showing daily or hourly observations? It is not mentioned in the text.
c) What pressure value is plotted? Observed value (at what height above sea level) or as sea level. This might be clearer if table 1 is updated.
Line 170: Measurable precipitation needs to be defined. Common resolution of precipitation observations is about 0.1 mm. It thus sounds odd that the measurable precipitation needs to be at least 1 mm/day. Please clarify.
Line 199: If the clouds promote vertical mixing, how can the conditions lead to stable temperature profiles? It more sounds like you have unstable or near neutral (windy) conditions.
Figure 4: What is plotted in the figure? Hourly average wind speed values or daily values?
You need to define your wind gust. Max value under what time period. Its also relevant to know the frequency of the measurement.
Line 235: Specify from from which sensor the data comes from (you write that there are two pyranometers).
Figure 5: What values are plotted? Daily average values, hourly average values or ..?
Line 261: Is the "." supposed to show that the values a multiplied by each other?
Line 274: Could the shape of the cure be due to drifting in RHmax value?
Line 289: It difficult to talk about trends when you at the same time show that they are not significant!
Line 318: I suggest you specify the observation height. Common meteorological data are from 1,5 or 10 m. So important to be clear about the heights here!