1. Convener tool SOI for abstract management: in session organization phase I (SOI), conveners review the abstracts in their session. They can accept, reject or transfer abstracts to another session, or upload late abstracts. They can also discuss session merging with the PG chairs and PG scientific officers, and proceed with merging when needed. Session mergers are possible within and between programme groups.
2. Session threshold: sessions with a small number of abstracts (5 or less) will be cancelled. Authors are informed and asked to indicate a new session for their abstract.
3. Convener tool SOII for session tagging: during session organization phase II (SOII), conveners provide information on no-overlap and back-to-back requests, among others, as well as on estimated desired room size.
4. Finalize SOI and SOII if not finished by session conveners: after the conveners' deadlines for SOI and SOII have expired, the PG Chair will be asked to finalize the SOI and SOII tools for their PG sessions that are still open (i.e. conveners have not finished). Detailed instructions are provided within the PCI tool.
5. Session similarity: if a significant number of keywords or words in a session's title and description are similar with one or more sessions, these sessions are listed as potentially similar, with the option to contact the conveners to eventually agree on a merger. Please carefully check these sessions that are flagged as similar, and make sure that they are distinct and/or complementary.
6. Session mergers: sessions that received few submissions (but were not cancelled) have to be merged. Sessions that are very similar in scope can also be merged for a more coherent programme. Conveners and PG Chairs can merge sessions in SOI. It is advised that once a merger is decided, authors are informed by conveners and given time to eventually request a transfer of their abstract to a different session. Then, the procedure for finalizing the merger of sessions is as follows:
   • Discuss which session will form the basis for the new session.
   • Update the title, abstract, and list of conveners of this base session.
   • Mark all abstracts in the other session for transfer into the new (base) session.
   • Accept all those abstracts in the new base session. The result is that the base session for the merger now contains the abstracts of both sessions, while the other session contains no abstracts and can then be withdrawn (i.e. removed/cancelled).

It is recommended that the convener list, session title, and description are adapted in the case of a session merger. This is to guarantee the best representation of the ideas, topics, and targeted communities of all sessions involved in the merging. The session's title and description can be adjusted by the main convener or any of the co-conveners of the new (base) session through the session modification tool. The list of co-conveners, however, can only be adjusted by the main convener of the new (base) session. We recommend keeping the number of conveners at a maximum of 5 conveners (at least two active conveners, 1 convener and 1 co-convener). However, if justified, merged sessions can have a maximum of 7 conveners (1 main convener and 6 co-conveners).

In addition:

1. Rejected abstracts: in the PCI tool, PG chairs are asked to review the abstracts rejected by a convener for possible acceptance in another session or PG. Please carefully check these abstracts.
2. Similar abstracts: PG chairs are also asked to check those abstracts in which an analysis found substantial similarities to other submissions. Double submissions should be withdrawn. Feel free to use the EGU25 Topic Similarity Adviser.
3. Abstract acceptance: as part of the PCI tool, authors are informed about the acceptance (or not) of their contribution by a letter of acceptance. This letter does not yet state the form of presentation nor inform about scheduling issues.

Within the PCII tool, PG chairs are asked to schedule the sessions led by their PG by assigning rooms and time blocks to the sessions. Later, in session organization phase III (SOIII), conveners will use the PCII results to implement their sequence of presentations, according to the meeting format of the General Assembly.

When scheduling, PG chairs should pay attention to time conflicts and to conveners' requests. Requests from conveners (done during SOII) are available for download in the PCII tool.

PG chairs should carefully read the guidelines for scheduling that will be provided with the scheduling information email. They should not finalize PCII until the February PC meeting.

Clusters

The allocation of rooms for sessions is done by the PC Co-chairs and by single PGs or clusters. PG chairs that are within a cluster are asked to negotiate rooms with their cluster colleagues before they place sessions in the system.

Scheduling orals

1. Oral sessions are time blocks of 1 hour and 45 minutes.
2. Oral presentations can be scheduled in slots of 10 minutes, including change-over times and questions. Solicited presentations can be attributed to a 10-minute, a 20-minute, or a 30-minute slot, as preferred by the conveners' team. Conveners can schedule one solicited presentation per time block.
3. It is possible to schedule presentations for less than the total time of an oral block, with the remainder set aside for discussion, for instance. It is also possible to include a slot of 5 minutes for an introduction to be given by conveners. This is done by using the subtitle option of the tool.
4. PG chairs should pay attention to the fact that one oral block can only accommodate a maximum of 10 (either on-site or virtual) regular presentations.
5. Oral sessions can only be scheduled in the rooms and time blocks that were assigned to each PG or cluster.
6. It is possible to trade time blocks and rooms among PGs or clusters within the PCII tool, but please make sure that all involved PG chairs agree upon that.

Scheduling PICO

1. On-site poster sessions take place in the morning or afternoon of the conference day, the display time spanning two consecutive time blocks (morning: TB1–TB2 or afternoon: TB3–TB4). The designated attendance time, when the author is expected to present their poster, will vary for each author between TB1 or TB2 for morning sessions and TB3 or TB4 for afternoon sessions. This attendance time will be confirmed through the letter of schedule. Consider, there will be no TB4 on Friday.
2. PG chairs should schedule poster sessions in a way that posters are equally distributed over the week, and time blocks of a given day.
3. They should pay attention to avoid overlapping poster sessions with their corresponding oral sessions.
4. Poster locations (including halls) will be assigned after the PCII tool.
5. Virtual poster sessions will be scheduled during time block 3 (TB3). During PCIII, PG chairs are to topically group virtual posters into virtual poster sessions and appoint a respective session convener. The number of virtual poster sessions within the week will depend on the total number of virtual posters of a PG.

Solicited talks

Conveners will set the status of solicited presentation (oral, PICO, or poster) in their session in SOIII. A session can only have one solicited abstract per time block. In very rare circumstances, PG chairs can decide if an exception to this rule can be made. Solicited oral presentations can be attributed to a 10-minute, a 20-minute, or a 30-minute slot, as preferred by the conveners. Additional information on solicited talks is provided in the convener guidelines.

Medal and Award lectures

Division medal lectures, Arne Richter Award for Outstanding ECS lectures, and Division Outstanding ECS lectures are to be organized by the PG chairs and Division Presidents. It is recommended the following:

1. Division medal lectures should be scheduled for 30 or 60 minutes, preferentially at lunch or evening slots to avoid overlapping with scientific sessions.
2. Arne Richter Award for Outstanding ECS lectures and Division Outstanding ECS lectures should be scheduled for 20 or 30 minutes. They can be scheduled together with the division medal lectures (e.g., one after the other in a 60-minute session) or within a chosen oral session of the PG programme (after agreement with the conveners of the session).

In all cases, PG chairs/Division Presidents should communicate and agree with medallists and awardees before scheduling the lectures. The date and time of these lectures should be submitted via a designated form.

The call-for-skeleton programme opens in June for PG Chairs. It is available via the Copernicus Office dashboard for PC members called "PC Overview", and the corresponding access link is provided by email. In this phase, PG Chairs are asked to define their sub-Programme Groups and the sub-Programme Group Scientific Officers.

The public is invited to suggest sessions they would like to organize during the General Assembly. Guidelines for session proposal can be found in the convener guidelines and rules. PC members are invited to read them carefully.

In addition, we note the following:

1. Session title and description: when submitting a session proposal, conveners provide a session title, a short and a long description, and a list of co-conveners. At this stage, only the title and the short description are visible on the conference website. However, PC members can see these information completely by logging in to the provisional programme.
2. Session modification: conveners are only able to change the title and description of their sessions during the call-for-session-proposals and later during the Session Organization stages (tools SOI and SOII). If there is an urgent need for change outside these phases, conveners must directly ask their PG Chair or science officers to implement the requested changes. This can be done using the PC Overview tool.
3. Cooperation between PGs: conveners can suggest other PGs for session co-organization. The PG Chair follows up on these suggestions through the session programme finalization tool once the public call-for-session-proposals is closed.
4. Session co-sponsoring: conveners can suggest co-sponsoring of their session by colleague scientific organizations. The colleague organization should have been informed by conveners and/or have approved the co-sponsorship prior to session proposal submission. The PG Chair is responsible for following up on these suggestions during the session programme finalization.

After the public call-for-session-proposals, PG Chairs and science officers are asked to finalize the session programme for their Programme Group, before the public call-for-abstracts starts. Please pay specific attention to the following:

1. Finalization: once their programme is ready, the recommendation for PG Chairs is not to press "finalize" until the autumn PC meeting, when all Programme Groups are finalized together. After session programme finalization, further changes can only be implemented by Copernicus Meetings.
2. Permissions: science officers serving as sub-Programme Group chairs can only see and modify sessions and session proposals of their sub-Programme Group(s) and adjust the respective sequence in the programme. The entire list of sessions and session proposals of all sub-Programme Groups is only available for PG Chairs.

When implementing sessions, the following applies:

1. Accepting session proposals: PG Chairs and officers should carefully read the session descriptions and decide whether they accept the sessions proposed to their Programme Group or sub-Programme Group. Session descriptions can be adjusted, and similar sessions can be merged during this phase (see below).
2. Ordering of sessions: sessions can be moved to any position within the programme, including categorization into sub-Programme Groups. This is simply done by drag-and-drop. The position in the sequence of sessions will set the session numbering.
3. Session numbering: session numbering is done automatically upon finalization of the programme. Each session is assigned a number, which is based on (a) the affiliation of the session to a sub-Programme Group, and (b) the sequence of sessions within the sub-Programme Group. Thereby, the session number contains a running number within the sub-Programme Group of the leading PG (e.g. BG6.4, for a session in the sub-Programme Group BG6 of the leading Programme Group BG). This applies also to ITS sessions and their related Programme Groups (e.g. ITS3.6/NH2.3).
4. New sessions: PG Chairs and officers can upload new sessions if they think it is necessary, for instance, to fill thematic gaps in their session programme that are not already covered by the public session proposals.
5. Conveners rules and team diversity: conveners should follow the conveners guidelines and rules. If rules are violated, the system will not allow the finalization of the programme. We also recommend to check conveners team diversity, as specified in the guidelines.
6. Session similarity: if similarity is found for two or more sessions in a significant number of keywords or parts of their title and description, these sessions are flagged and listed for potential merger. Session mergers are possible within and between PGs. It is strongly encouraged to build a programme with sessions that are distinct and/or complementary. The presence of too similar sessions can be confusing for authors when submitting their abstracts.
7. Implementation of co-organization: if two or more PGs have a significant and active interest in the topics of a session, this session can be displayed as organized by a leading PG and co-organized by the other related PGs. It is implied that conveners with a link to the different PGs are involved in the session. Session co-organization is initiated by conveners, who suggest co-organizations when submitting their session proposal to the programme of a leading PG. The PG Chair of the leading PG decides on sending the co-organization requests to the other PG Chairs, who ultimately decide on the outcome of the requests. In the case of acceptance, the session is listed in the programmes of the PGs involved in the co-organization. The leading PG remains responsible for all organisation issues related to the session.
8. Implementation of co-sponsoring by colleague organizations: conveners can suggest co-sponsoring when submitting a session proposal. The final decision lies with the PG Chair. We recommend they check with conveners the following: (i) co-sponsoring is reciprocal, involving sessions organized in co-sponsorship at meetings of both organizations; (ii) the session has conveners from both organizations; (iii) the colleague organization agrees to session co-sponsoring; and (iv) the session co-sponsoring does not imply funding. A co-sponsoring organization should not influence the work of the conveners or the content of the session.
9. Inter- and Transdisciplinary Sessions (ITS): session proposals related to the topics of one or more PGs and with a truly inter- and/or transdisciplinary scope might have been suggested to the ITS programme, and need attention from the related PG Chairs (read carefully the ITS guidelines). ITS sessions are organized by the ITS PG Chair, in agreement with a disciplinary associated leading PG. Co-organization with one or more PGs is also possible. The eligibility of an ITS session proposal is evaluated by both the ITS chair and the associated leading PG Chair before its implementation in the programme. If both parties deny the eligibility of the proposal for the ITS programme, the session proposal is moved to the leading PG for further handling (i.e., implementation as a PG session, rejection of the proposal, or merger with another similar session already proposed in the PG). If the ITS chair and the leading PG Chair disagree on the eligibility of the proposal, they must refer to the Programme Committee Co-chairs for a final decision.