By Niki Morock, Meteorologist
As I sat here, eating my lunch at my desk and reading weather news from last week that I had not had time to read until the quiet Friday before Christmas weekend, a thought occurred to me: weather and maps go together like peanut butter and jelly. You can appreciate each separately, but without one or the other, you could be missing out.
One of the big weather headlines last week was about a rare snow that fell over the desert in northern Africa. NASA's Earth Observatory highlighted the story with a satellite image of the whitened area around Ain Sefra, Algeria, at the edge of the Saharan Desert. The last recorded snow there was in February of 1979, so it truly is a rare occurrence. The combination of dry desert climate and its location in relation to both the equator and the Atlantic Ocean play a part in the area's lack of regular snowfall, but without a map, how would we know those factors?
Take a look at the Google map above. The pinned location is Ain Sefra, and the line drawn from there to southern Arizona is along the latitude 32.75 degrees North. The line crosses the southern United States through areas that do not normally see snow, but do get some on rare occasion, and it ends in Yuma, Arizona.
Both Yuma and Ain Sefra are arid regions, and some might blame their distance from the equator. Of course, they would be mistaken. Georgia, Alabama, Mississippi, Louisiana, and eastern Texas fall along the same parallel and are far from desert-like. The difference between those southeastern states and the southwestern states has to do with ocean circulation almost as much as their lack of white Christmases has to do with their distance from the equator.
You can see on NOAA's map of major ocean currents that both the Atlantic Ocean and the Pacific Ocean have currents that affect the land masses that border them. Those currents circulate generally clockwise in the Northern Hemisphere bringing warm water to the lands to their west - like the east coast of the United States - and cooler water to the lands to their east.
Those currents explain why Ireland and the United Kingdom have similar weather to our Pacific Northwest, and they help explain why Arizona and southern California have a climate similar to Saharan Africa's.
Of course, geography also plays a role in a region's long-term weather conditions. Mountains, large lakes, etc., must be included when considering climate, and those can be seen on some types of maps as well.
My point is that if you take the story - or worse, just the headline - at face value without putting it into context, you miss a chance at full comprehension.