Monday, February 19, 2018

All Sky Photometer for NearSys Station, 19 February 2018

The All Sky Photometer began collecting data at 7:09 AM MST. The data shows the sky was very cloudy twice today.

Sunday, February 18, 2018

Visible and Thermal Images of a Cumulonimbus

A storm cloud approached NearSys Station today. I was curious about it's temperature variations and so took several visible and thermal images to compare. Here are two of the best pairs.


Based on color, the foreground cloud is warmer than the background one.


Bluer regions indicate colder patches of clouds. I think the warmer clouds are those that appear slightly brighter. Slightly darker regions in visible images may be higher altitude portions of the cloud.

Sunspot Observation at NearSys Station, 18 February 2018

The sunspot group that was visible last week is gone. Since it appeared at the sun's meridian (from Earth's perspective) eight days ago and the group has rotated at least 90 degrees, the sun must rotation once on its axis in less than 4X8 or 32 days.

No visible sunspots here.

Visibility for NearSys Station, 18 February 2018

The UAVSonde flight at 8:30 AM MST indicated the visibility is at least 30 miles. Clouds appearing over the Boise Mountains may indicate the visibility is at least 50 miles.

Looking south

Looking north

Looking east

Looking west

Thursday, February 15, 2018

Sky and Ground Thermal Observation for NearSys Station, 15 February 2018

A thermal measurement at 6:15 PM MST indicated a ground temperature of 14 *F And a cloud temperature of -2 *F. At a difference of 16 degrees and assuming a dry adiabatic lapse rate of 5.4 degrees per 1,000 feet, the cloud base is 3,300 feet above the ground.

The stratocumulus above NearSys Station were producing small amounts of virga earlier.


Tuesday, February 13, 2018

Sunspot Observation at NearSys Station, 13 February 2018

Before that sunspot has a chance to rotate out of view, I got a second picture.


Monday, February 12, 2018

Changes in the Estimated Altitude of Stratus Clouds as Snow Approaches

Meteorologists predicted snow for the lower Treasure Valley on Sunday afternoon ( February 11th). So I started making measurements of ground and sky temperatures using my Seek Reveal thermal imager. Then assuming a dry adiabatic lapse rate of 5.4 degrees per thousand feet, I calculated the base height of the clouds. It was readily apparent their altitude was lowering as the day progressed. The data below seems to confirm that qualitative observation.

The snow didn't start until sometime after 9:15 PM MST and was finished by 4:30 AM MST the next morning. Therefore, there is no data during the time of snow at NearSys Station. The snow we did get was light and amounted to only 1/4 inches.

Ground and Air Temperatures

Estimated Altitude Corresponding to the Temperature Differences

Sunday, February 11, 2018

Visibility for NearSys Station, 11 February 2018

The UAVSonde made a visibility assessment at 8:00 AM MST, 11 February 2018. After reviewing the images, it was determined the visibility is in excess of 50 miles.

Looking north

Looking east, the Boise Mountain range is clearly visible

Looking south

Looking west

Saturday, February 10, 2018

Sunspot Observation at NearSys Station, 10 February 2018

SpaceWeather.com reported the appearance of a large sunspot group crossing the sun. This is at a time when the sun should be entering a quieter time as it approaches solar minimum.

The SunSpotter telescope showed five sunspots in the group now crossing the sun's center.

By counting pixels and comparing them to the sun's known diameter, the largest sunspot was determined to have an umbral diameter of 18,300 miles and a penumbral diameter of 30,500 miles. That means the largest sunspot is nearly four times wider than Earth's diameter.


All Sky Photometer for NearSys Station, 10 February 2018

Photometer data was collected starting later than usual, at 7:52 AM MST rather than prior to 6:00 AM. It was a clear day with few if any clouds. However, since data collection began after dawn, the sky only brighten by a factor of two over the day.

This is a good reason to standardize the photometer readings, it would permit different days to be compared to each other.


Thursday, February 8, 2018

Sky and Ground Thermal Observation for NearSys Station, 8 February 2018

A thermal observation at 4:00 PM MST indicated the ground had a temperature of 33 *F and the altostratus over NearSys Station a temperature of -2 *F. Assuming a dry adiabatic lapse rate of 5.4 *F per thousand feet, The cloud base had an altitude of 6,500 feet.

The altostratus above NearSys Station in visible light

The altostratus above NearSys Station in long-wave infrared 

Sunday, February 4, 2018

Visibility for NearSys Station. 4 February 2018

The UAVSonde was launched at launched later than usual because of high winds. Visibility appears to be barely 50 miles.

Looking north

Looking east, the Boise Mountain range is barely visible, it at all.

Looking south

Looking West into the setting sun

All Sky Photometer for NearSys Station, 4 February 2018

NearSys Station started out cloudy, but cleared up for lunch time. Then it became cloudy again. The spike in blue is puzzling and needs to be watched in future measurements.