Atmosphere, in my opinion, is one of the most difficult things to grasp in writing thriller fiction. In my own preferred genre it is perhaps a little more clear-cut as all speculative-type fiction should be suffused with a sense of the unnatural or unknown. A kind of fearful anticipation of what could happen or what might happen - that is beyond our normal understanding.
But I think atmosphere is important in so many other ways. It creates certain expectations in a reader that must then be lived up to.
Atmosphere is created by various things. Settings help to a large extent and so do characters themselves but also the language used can also create atmosphere. But the atmosphere must fit with the story and so it is something I always give a great deal of thought to before I even begin writing.I suppose the easiest atmosphere to imagine is a scary one such as the type used in ghost stories. The clichéd haunted house that creaks and moans or the fog- shrouded moor that hides dark secrets. The hooting of owls and wild life at night - or the abnormal absence of the same!
Other types of genre fiction have their own clichés, of course. I do believe atmosphere is closely related to the emotion you are trying to elicit in your reader. If you wish your reader to feel anger than an unpleasant atmosphere (or setting) will help. If you are looking for a tender emotion then a romantic setting may help. However it is not just about setting. A harsh factory floor can be made atmospheric and romantic with the right words and actions.The trick (and the challenge) is to create your own sense of atmosphere to embed in your story, without it being clichéd. More difficult than it seems, I feel. For atmosphere is ethereal and like beauty, is in the eyes of the beholder ( apologies for the cliché).
Do you find it easy to develop a sense of atmosphere that fits with the story/genre?