On 17 October 2024, the AERONET team corrected instrumental time shifts at two Australian sites: Birdsville (17 July 2018 - 25 November 2022) and Fowlers_Gap (5 June 2018 - 5 May 2021). The time shift of about 1 min was caused by the GPS malfunction. The original data had unrealistic air mass calculations at higher solar zenith angles and resulted in the Quality Assurance algorithm removing measurements, especially during low AOD periods. Consequently, climatological data at those sites contained biases. After applying the time correction to the clock readings in the raw datasets, a sig-nificant increase in Level 1.5 and Level 2.0 data took place. Datasets, display charts and climatology tables for these sites were updated on the AERONET website. All users working with Birdsville and Fowlers_Gap data are advised to download their latest versions, processed on or after 17 October 2024.

Dear colleagues, partners, and all participants in the AERONET Science and Application Exchange,

We are pleased to announce that the event page has been posted on our website under the Publications tab. It includes photo highlights from the event, along with the full program and links to some of the presentations and posters. If you would like access to all the event photos, please email Pawan Gupta and Petar Grigorov to request the Google Drive link.

We appreciate your support and look forward to more events like this in the future!

AERONET has been acquiring lunar observations from the majority of model T CIMEL sun photometers in the network for many years and producing a night-time AOD data set, which currently includes observations at 492 sites dating back as far as 2014 for some locations.

The Lunar AOD product relies on the ROLO Lunar Irradiance Model for extraterrestrial spectral irradiance, and for some time, it had been clear that some corrections needed to be made to this input to produce valid lunar AOD.

The AERONET approach to address this was by comparing Vo's (top-of-the-atmosphere signal) of high elevation lunar Langleys with solar Langleys at Mauna Loa Observatory (MLO) and Izaña calibration facilities. For a given instrument, the solar to lunar Vo ratios should match the sun/sky gain ratio of 4096. Thus, observed deviations from this nominal value could be determined as a function of lunar phase angle (LPA) and used as an empirical correction factor by which the base ROLO irradiances are modified.

The initial (provisional) lunar AOD product was based on a moderate number of such solar/lunar Vo comparisons; however, in the last several months, this comparison set was updated with the last 5 years of Langleys and adopted modified filtering thresholds. This has resulted in substantially more solar/lunar Langley pairs (N > 500 at every wavelength) from MLO and Izaña calibration sites. These data were used to generate statistically robust ROLO correction factors for each wavelength as a function of LPA.

The reprocessed dataset of lunar AOD, corrected with the updated empirical bias, has now also been extensively analyzed for all contributing sites. This analysis, which included evaluating the continuity of AOD between solar and lunar measurements during limited temporal windows, provides confidence in the robustness of the data. The absence of systematic bias and the AOD continuity during sunrise or sunset transitions further validate the accuracy of the dataset. Therefore, the decision was made to remove the current provisional status of the lunar level 1.5 data.

It's important to note that while the revised dataset of lunar AOD is a significant improvement, there are some operational aspects of the automated cloud-screening that are absent from the lunar AOD QC protocols. Additionally, there are other additional sources of uncertainty in lunar AOD which are spectrally variable which also result in larger total uncertainty of cloudless data as compared to daytime sun measurements of AOD. As a result, the lunar AOD cannot be expected to exactly match the accuracy of daytime AOD measurements. We continue with research to develop improved nighttime cloud screenings and processing to final Level 2.0 datasets.

We are happy to report that AERONET data are now visible on NASA's Worldview application. This open source code app from the Earth Observing System Data and Information System (EOSDIS) provides the capability to interactively browse over 1000 global, full-resolution satellite imagery layers and then download the underlying data. Many of the imagery layers are updated daily and are available within three hours of observation. Four of those layers represent AERONET's Aerosol Optical Depth 500nm (Near Real-Time and Daily) and Angstrom Parameter 440-870nm (Near Real-Time and Daily) data.

Dear AERONET colleagues, partners, and data users. On May 8th, 2024, the AERONET system will be upgraded from CentOS 7 to Oracle Linux 8. This means that the server, including website and relational database, will be down for most of the work day while we are migrating and synchronizing our data. Note that instruments will still be operational and we do not expect any data loss. We appreciate your patience!

Mark your calendars! We are excited to announce the upcoming AERONET science and application exchange, to be held on Sep 17-19, 2024, in College Park, MD, USA. This will be an in-person meeting only.

The exchange will bring together the global AERONET community to discuss and collaborate on topics related to the AERONET system. Such topics include, scientific development, data products, instrument calibration, research and application. This is also a wonderful opportunity to celebrate AERONET's 30 years of success in atmospheric aerosol measurements. We will have a mix of invited talks, contributed talks, and poster presentations, as well as ample opportunity for networking.

More information on Registration, Important Dates, Abstract Guidelines, and Accomodations can be found here.

We are thrilled to release our inaugural newsletter that covers most of 2023, with each following edition being released on a quarterly basis. This past year was a very exciting one for our team, filled with productive meetings and workshops, instrument and data upgrades, an abundance of new sites, and improvements to our data exploration and data download tools.

All newsletters will be stored in an archive found in the publications section of our webpage. In the future, we will explore ways to deliver the newsletter in a more user-friendly and interactive way, such as embedding it directly into an email with full button and hyperlink functionality. We appreciate your patience and support to the AERONET project!

AERONET is dedicated to high quality aerosol measurements around the world. One of the major reasons for AERONET success is standardization of instrumentation and calibration. Since 2016 CIMEL Electronique introduced a new version of the instruments deployed within AERONET: CE318-T Sun Sky Lunar photometer. This version has a number of advantages over the previous versions:

1. Provides day (sun and sky) and night (moon) measurements.
2. Implemented New Hybrid SKY scenario that assures more inversions of Volume Size Distribution (VSD) from sky measurements.
3. More accurate SUN/MOON tracking with micro-stepping technology (0.003° resolution).
4. Remotely upgradable firmware.
5. No risk of data loss: unlimited internal memory.
6. On-board GPS to provide exact position and time.
7. 4-G modem for data transfer.
8. Allows for more accurate calibration transfer (including sky).
9. Continual support for parts and firmware modifications.
10. Multi-spectral including UV channels (including sky).
11. Possibility to use the instruments in mobile mode.

Please note that older versions are not supported by CIMEL (both from parts and firmware). A lot of older version parts are obsolete and there is no way to add new measurements to the older version firmware. Calibration of the older versions is more labor intensive and time consuming. New developments within the network will not be transferable to the old versions.

Based on this we STRONGLY encourage the owners of the older versions to upgrade them to CE318-T version.

There are two options for the upgrade (contact CIMEL for details):

1. Purchase a totally new instrument (preferred solution for all old versions)
2. For digital versions (v5): replace sensor head, controller unit, and sensor head cable to bring the instrument to the same standards optically. Upgrade the robot at a later time.

Sites within ACTRIS domain and directly funded to become ACTRIS national facilities are required to upgrade to CE318-T by 2025.