tag:blogger.com,1999:blog-5337555368793819627.post8361771146630382619..comments2023-06-07T09:04:36.390-04:00Comments on More Grumbine Science: Verifying forecasts 1Robert Grumbinehttp://www.blogger.com/profile/10783453972811796911noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-5337555368793819627.post-4271546592685838712010-12-25T12:57:44.127-05:002010-12-25T12:57:44.127-05:00As sea level rises, presumably the amount of land ...As sea level rises, presumably the amount of land area in the Canadian Archipelago will decrease. Whether or not this is enough to affect long-range forecasts for sea ice (50 years?) would surely depend on the relief of those islands, which I know nothing about.Steve Lhttps://www.blogger.com/profile/11808202186253600821noreply@blogger.comtag:blogger.com,1999:blog-5337555368793819627.post-39724416157671160082010-11-28T14:41:12.704-05:002010-11-28T14:41:12.704-05:00I first encountered this when I was trying to make...I first encountered this when I was trying to make a land mask for my grid (at that time 25.4 km on a polar stereographic grid) from someone else's higher resolution land mask (1/16th degree, on a latitude-longitude grid, call it 7 km). The simple thing to do is just count up how many cells from the high resolution grid fell into my lower resolution boxes, and what fraction were land. Clearly (turns out this isn't so clear if you consider how the satellite sensors work) if all of the points were water, you call it water on my grid. If they're all land, call it land. But how about if it's some of each? That's the million km^2 that you affect by your decision(s).<br /><br />It also turned out that the higher resolution mask was biased in favor of calling cells 'land' (for reasons that were sensible to the creators of the mask), so that if any portion of the about 50 km^2 cell were land, even just 1 km^2, then the cell was called land.<br /><br />I do things differently now, working directly with bounding curves for the land, lakes, and islands. But there is still a fundamental, unavoidable, problem of what to do with cells that are partly land, partly water, or that are very close to land (suppose one edge of the grid cell runs right next to land the whole way, but never has land inside -- but your ocean satellite sensor sees everything within 12 km of its observation point?)Robert Grumbinehttps://www.blogger.com/profile/10783453972811796911noreply@blogger.comtag:blogger.com,1999:blog-5337555368793819627.post-23059269605929529102010-11-27T00:38:55.045-05:002010-11-27T00:38:55.045-05:00any pointers to what you have done in griding??? ...any pointers to what you have done in griding??? <br />I'm pretty sure your smart enough to try just not counting the questionable area's, any other dead horses I should know about see as I'm starting at around -1,000,000 points in the hole<br />thanks jacob ljacob lnoreply@blogger.com