Abstract

This article reports on cloud observations and air temperature data recorded over a 3-hour window during the October 14, 2023 annular eclipse event from Tacoma, Washington, USA using the GLOBE Observer app. In addition to the app data, we present our own experiences throughout the event. Data was taken as GLOBE User ID: 114994400 from Tacoma, WA, USA (47.3054, -122.5098). Observations started prior to first contact, at 0809 PDT, and ended at 1039 PDT. Maximum eclipse (81% coverage) was at 0919 PDT).

Image of temperature fluctuations during the eclipse — **Figure 1**
A screenshot of the GLOBE Observer Eclipse app displaying collected air temperature data across the eclipse event window. As you can see from the upper right corner, the app can be set to Fahrenheit, and it records your location information an easy-to-read graph of temperature versus time.

1. Introduction

The GLOBE Observer program seeks information on local conditions for observers throughout all stages of solar eclipses through their GLOBE Eclipse phone app (https://observer.globe.gov/do-globe-observer/eclipse). This paper describes my experiences completing this citizen science investigation during the October 14, 2023 Annular Solar Eclipse. I viewed the eclipse from Tacoma, Washington where the event maximum was at 9:19 am (PDT). I was not within the path of annularity; I experienced a partial eclipse with a maximum 81% coverage. I recorded eclipse observations from 7:44 am (PDT) to 10:49 am (PDT) using the GLOBE Observer app.

GLOBE User ID: 114994400

Location: Tacoma, WA, USA (47.3054, -122.5098)

Start Time (PDT): 0809

Max Eclipse Time: 0919 PDT (81%)

End Time (PDT): 1039

2. Methods

I completed cloud observations every 30 minutes and reported air temperature every 10 minutes over the observation window. During the 30 minutes surrounding the event maximum (9:19), I reported air temperature at 5-minute intervals (Table 1). All data was recorded using local time – Pacific Daylight time – on a 24 hour clock. Row 12 (bolded) was during maximum eclipse.

Observation Data:

Table 1
Obs	Time (PDT)	Time (UTC)	Air Temp (°F)	CloudObs?	Satellite Match
0	0744	1444	na	Y	GOES-18
1	0802	1502	57.1
2	0809	1509	57.0	Y	GOES-18
3	0819	1519	56.6
4	0829	1529	56.8
5	0839	1539	56.8	Y	GOES-18
6	0849	1549	57.0
7	0854	1554	56.8
8	0900	1600	57.5
9	0905	1605	56.9
10	0910	1610	56.7	Y	GOES-18
11	0914	1614	56.1
12	0919	1619	56.3	Y	GOES-18
13	0925	1625	55.5
14	0930	1630	55.8
15	0935	1635	56.3
16	0940	1640	56.8	Y	GOES-18
17	0945	1645	56.8
18	0950	1650	57.0
19	0955	1655	58.5
20	1005	1705	56.8
21	1009	1709	57.0	Y	GOES-18
22	1019	1719	57.9
23	1030	1730	58.3
24	1039	1739	59.0	Y	GOES-18
25	1049	1749	59.1

Figure 2 below shows the east-facing (i.e. in the Sun’s direction) cloud photos captured throughout my observations. This vantage looks out over the Puget Sound to the east towards Mount Rainier.

The day started out fairly cloudy and cleared up just enough to view the eclipse during its height. After about 0930, clouds slowly crept back in as well as a dense fog layer.

I made my first observation (Obs 0) prior to first contact, to record a pre-eclipse observation. Obs 1 at 0809 is at the projected first contact at my location, Obs 4 is at peak coverage, and Obs 7 at 1039 PDT is at the projected end of the event.

All my cloud observations were matched up with data from NOAA’s GOES-18 geostationary satellite.

Progression of east facing cloud photographs throughout the eclipse observation window. — **Figure 2**
Progression of east-facing cloud photographs throughout the eclipse observation window.

During the eclipse event, I experienced a general loss of light as well as a gradual increase in cloud cover, and, ultimately, fog at my location. I also experienced cooling temperatures as the eclipse progressed. Figure 3 below plots measured air temperature across time of day.

graph of temperature data over time showing it going up and down — **Figure 3**
Detailed time versus temperature data through my observing window.

After examining the data, I would guess that the two peaks on the graph (57.5°F at 0900 and 58.5°F at 0955) are likely errors in air temperature measurement. In general, it appears that temperatures remained stable until around 0910 at around 56.7°F. At that point, there is a noticeable trend downward which I could feel as well as measure. This continued until a temperature trough at 0925 at 55.5 °F. This was the first temperature reading after the maximum eclipse time at my location. As the Sun slowly emerged from behind the Moon, temperatures continued to steadily increase throughout the sampled window.

3. Summary

The observations and data support what one would expect during a solar eclipse event. There was a gradual loss of light coupled with cooling temperatures across the front end of the observation window. As the Sun emerged again on the back end of the observation window, light increased and temperatures warmed. Cloud cover and an incoming fog layer likely muted some of the effects of the eclipse at my location. This data is contributed to the GLOBE Project for analysis that will have statistical rigor.

Anecdotally, I observed the eclipse event from a public park in my hometown. It was exciting to see all the people gathered in the park with cameras and eclipse glasses to view the event. I found it great to be out experiencing the eclipse with a community of like-minded people.