Marys Peak Cloud Statistics
Over the 1,563 days the camera has been installed (4 years 3 months, and 11 days as of August 7th, 2014), 798 days were watched for this study. Of the 798 days observed, 780 have usable full day videos. That means 18 days were skipped due to a lack of a full video or part of a video. In the year 2011, the first full year of the camera, every day was watched. In the second half of 2010 (after installation on April 28th), 2012, 2013, and the first half of 2014 (until June 19th) a video was watched every 3 days to optimize video watching efficiency and to hopefully avoid getting stuck in the weather pattern. (Note: between June 19th and August 7th, 2014 a video was watched everyday as the final project was in full swing). Over the 780 days, there were 448 days where marine stratus or orographic stratus was observed, 321 days where convective cumulus was observed, 185 days where altostratus or altocumulus was observed, 53 days where stratocumulus was observed, 45 days where lenticularis was observed, 248 days where ground fog was observed, and 348 days where clear skies or high cirrus was observed (See Figure 1). Note how more than 50% of the observed 780 days included marine stratus or orographic stratus.
Marine stratus and orographic stratus occurs fairly regularly throughout the year, being slightly less common during the summertime (See Figure 2). The stratus was most common during the early morning and late evening or after precipitation had fallen.
Convective cumulus were also a very popular occurrence and have a slight seasonality curve to them being the most popular when the sun is strong and moisture is still available in the late spring (see Figure 3). Sometimes the sky in both the Willamette Valley and the Coastal Range would be speckled with them. On other days, cumulus would only develop over Marys Peak or Grass Mountain, likely a result of anabatic winds. Occasionally the cumulus would build high enough that they would produce precipitation. Actually cumulonimbus were rare and hard to pick out as they were often much larger than the frame and dropping a lot of precipitation.
Altocumulus and altostratus had a smaller overall occurrence compared to some of the other categories. It is possible that this number is lower than it actually is due to the nature of altocumulus and altostratus. They are higher elevation clouds, so while they don’t interact with Marys Peak, they can’t be seen unless the lower parts of the atmosphere are cloud free. The occurrences marked in Figure 3f show the times only when they were visible through breaks in lower level clouds or when there were no lower level clouds at all (See Figure 4).
Stratocumulus were the second lowest observed cloud type overall only ahead of lenticularis. This could be due in part of mislabeling of the cloud group. Stratocumulus clouds often form from decaying marine stratus or cumulus clouds (American Meteorological Society, 2014). At times, stratocumulus may have briefly been around in transitions from marine stratus to convective cumulus. Only times where there were obvious extensive periods of stratocumulus was it recorded. Perhaps one could question the integrity of this category and its necessity. Otherwise, stratocumulus were much more common during the wintertime when more moisture was present and skies were dreary. Some of the summer months did not record a single occurrence of stratocumulus (see Figure 5).
Lenticularis clouds formed more regularly throughout the year and do not appear to have much of seasonality. Through all of the months watched, they formed anywhere from just twice to multiple times per month (See Figure 6). Because of the low sample count of lenticular clouds, it may have been possible to have missed many more occurrences of this cloud type due to the nature of watching every third day. Very specific conditions were needed for these to be observed. Because air with a relative humidity near 100% was one of the criteria, it is very possible that lower clouds and precipitation obscured them higher up above the peak and the cloud base.
Of the 780 days, 218 started out with some sort of ground fog at sunrise that inhibited visibility and made detecting cloud arrangements at Marys Peak difficult if not impossible. On some days this burned off by 0800 hours, other times it lasted all day, and in some cases it came and went with precipitation. When graphed on a monthly basis, the seasonality of the fog is noticeable (See Figure 7).
The seasonality of clear skies and high fair weather cirrus clouds was also very evident when graphed in a similar manner. For all of the days watched each month, nearly 80% of those days had clear skies in August with less than 20% being clear in November (See Figure 8).
Our MissionThis webcam was funded by the National Science Foundation, with the original camera being installed by the Ocean Mixing Group on the roof of Burt Hall at Oregon State University on April 28th, 2010. The webcam is a part of experimental investigations into the physics of form drag in geophysical flows. The Biomicrometrology Group maintains the site as part of ongoing studies to understand and quantify interactions between the air, vegetation, and the land surface. The images obtained here are intended to complement studies of controlled flows over topographic obstacles in ocean and atmosphere. On August 4th, 2014, the Biomicrometeorology group at Oregon State University installed a new camera with near-infrared sensitivity to increase the window of viewability.
A collaborative, NSF-funded project by
C. Thomas, S. deSzoeke, L. Mahrt & E. Skyllingstad / OSU Atmospheric Sciences
J. Moum & J. Nash / OSU Ocean Mixing Group
Cloud Atlas compiled by REU student M. Spagnolo